ESE's works engine tuner [Archive] - Page 36

husaberg

19th August 2012, 13:35

Hello guys..

I just have to say, a really really interesting thread.
took me 2 weeks to read it.(on sparetime at work)
And when i´m saying interesting i mean INTERESTING!!!!

Still taking i glimpse here and there to see if it has been updated.

I´m building a 'overkill' Honda MB5 here in Sweden and got much much good info here.

A preview pic:
https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/564285_10150714075114475_540649474_9804621_1310594 736_n.jpg
Not complete at all on the pic,, but in progress.

Yes.. ~ 20hp is good..
But i reckon i will double that atleast.

My 88cc machine got 5disc clutch with uprated springs, it slips from time to time.
And in dragracing the dog in the gearbox are living an hard life.
any defects and the shiftforks takes the beating and snaps.
My 88cc machine is in the area around 20hp at the wheel.

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc6/253781_10150214618249475_540649474_7419375_7240948 _n.jpg

that´s a pic of my 88cc hybrid.
from the beginning a watercooled cylinder, shaved off the waterjacket and replaced it with cooling fins like an std MT5 cylinder.

Quick spec 88cc:
CR80 crank
NSR50 gearbox
5disc clutch
PVL ignition
Mikuni TM28ss bored out to 30.8mm
V-force reeds
Modified Suzuki RM85 -04 exhaust.(to raise the rpm level, not perfect i know but the moped runs hard)
Wiseco piston

PICS: 88cc
<img src="https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc7/59347_434338379474_540649474_5227523_7072134_n.jpg" width="140px"/><img src="https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc7/156776_477514024474_540649474_5954235_7597157_n.jp g" width="140px"/><img src="https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc6/162876_477513864474_540649474_5954230_3218643_n.jp g" width="140px"/>

My 136cc project is an 'hybrid' that too.
I have built an clutchcase that gives room for 8discs.

Hello..

this bike isn´t for GP racing.. it´s for dragracing and topspeed events in Sweden for 'Mopeds'
It´s an old Kawasaki KX125 cylinder either -86 or -87.
I have bored it up to 58mm and with 49.5mm stroke(MT8 crank) it is now 136cc

A quick spec:

Kawasaki cylinder 58mm bore with woessnerpiston, new nicasil
'torus' combustionchamber 13-1 in ratio
V-force reeds
two carbs one 36mm and one 40mm(Mikuni TM/TMX)
Samarin CR125 rod, to get 1mm bigger wristpin and a little bit longer to fit better in cylinder, std is ~100mm now it´s 105mm, and finally bigger big end bearing.
Calculated exhaust(in progress right now)
6spd gearbox
Cylinder and exhaust tuned to get peak hp at ~12000rpm and ~1000rpm 'overrev'.

will build two models of clutch, one 8pcs and one 'slipclutch' with centrifugal weights.

the moped itself is an strengthened MB5 with uprated suspensions.
then lengthened and lowered to get some kind of good highspeed behaviour.

Rgds.
Patrick

21hp @ 8600rpm from a 50cc engine??

That sounds like staggering bmep

Mmmm.............

wobbly

19th August 2012, 17:53

21 Bar - bmep = 21 Hp at 8500 in a 50cc, and you are going to double that, yea right.
When you do it we will send you a container of chocolate fish, and as always i offer several free blowjobs in humble recognition.

bucketracer

19th August 2012, 17:59

My 88cc machine is in the area around 20hp at the wheel.

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc6/253781_10150214618249475_540649474_7419375_7240948 _n.jpg

that´s a pic of my 88cc hybrid.
from the beginning a watercooled cylinder, shaved off the waterjacket and replaced it with cooling fins like an std MT5 cylinder.

My 136cc project is an 'hybrid' that too.
I have built an clutchcase that gives room for 8discs.

Hi Wobbly, I am not sure if he is talking about 88cc or 136 but as you have pointed out, certainly not 50 .....

SwePatrick

19th August 2012, 19:05

Uh,, oh.. sorry guys. :(
i Thought you understood that i dynoed my latest build.
That is the Honda MB5 in pictures and with 58mm bore and 49.5mm stroke.(i calculated wron earlier this year, got it to 136cc, but it is slightly above 130cc)
No way you can get 21hp out of 50cc with no added boost at those rpm.
I got 130cc in the new build.
Big problems with fuel in dyno thou :(

And to clear up some misunderstandings, i haven´t got any engine that is on 50cc.
I got an MT5 with an 88cc engine also, but that one isn´t dynoed.
that is the one with aircooled cylinder on pictures.

My 130cc is watercooled.

Rgds
Patrick

TZ350

19th August 2012, 22:09

Well things didn't go to plan today, after practice and prelim races, engine failure and a masive high side that slam dunked Kel. Team ESE apologise for the hold up while the ambo attended to Kel and took him off for a few Xrays. The police cars turned up because they had heard the call for an ambo and thought a motorcyclist had been knocked down in the street outside.

Well we are not sure what happened and will take the Beast apart later in the week and see what went wrong.

Otherwise it was a great day, well run, friendly bunch of riders and the rain held off until the end of the last race.

Henk

19th August 2012, 22:17

Never good when someone gets a ride in the white bus. Let us know what you can regarding how Kel is.

speedpro

19th August 2012, 22:39

Awesome series of photos. Kel will want a set, eventually. Hope he's OK.

ief

20th August 2012, 02:08

Nice pics indeed but looks painfull non the less, hope it's not to bad.

And damn those engine troubles :facepalm:

wobbly

20th August 2012, 08:45

Nearly as good as Stoners loose in Qual, countersteering with the wheel in the air - dump it down facing the wrong direction and the thing gets real big air with him on the deck.

F5 Dave

20th August 2012, 10:01

TZ350

20th August 2012, 17:13

Hope Kel is ok.

Kel called around today with his arm in a cast, broken bone in his hand and elbow, 6-8 weeks before the cast comes off, so just in time for the start of the North Island Series.... :D ..... well hopefully.

The engines symptoms looked the same as Taupo and Kaitoki where the ignition was wrong and I felt very depressed thinking I still hadn't got a handle on this TPS and 3D ignition mapping thing.

There were suggestions (not from Kel) that I should de tune it a bit to make it more reliable and I was tempted until I thought about it and realized that 100% of F4 2-Strokes that have failed when racing all made less than 31hp.

In fact the last blowup reported the other week in another thread was a 14rwhp 125, so the idea of de tuning for reliability is dumb. The right thing to do is develop the reliability of this engine and at 9 bar clearly this engine is not all that stressed, and I should be able to push that up to 10 or possibly 11.

268503 268504

Took the head off and it turns out that the modification I had done to the piston so the ring gap ran in the boost port for improved reliability was the problem. The pin had come out and jammed the ring and piston.

268500 268501 268502

So shot ourselves in the foot again but in a different and more imaginative way this time, sorry Kel.

Now does anyone know what the realistic upper BMEP number is for an air cooled 2-stroke because I would like to go there?

Dutchee

20th August 2012, 18:25

Awesome pix from Damien.
He went past Craig and about stopped, so thought something had gone wrong. cops turning up was hilarious as we'd just had that buggy turn up earlier. fun times.

bucketracer

20th August 2012, 19:40

... shot ourselves in the foot again but in a different and more imaginative way this time ...

A true Burt Munro achievement ...

SwePatrick

21st August 2012, 03:27

Sorry Patrick but we don't always remember what other people are running, - I also thought "22 from a 50 & then at only 8000, double bull". But back to the 136cc if its pulling that at such low revs it still looks like it will turn out to be quite useful, hope you can sort the carb issue.

I've made the mistake of setting up a inlet on the bench & found when I put the engine in the frame it was too steep for the carb.

Hope Kel is ok.

It´s ok.. i blame myself :)

Yes 21hp at those rpm´s is good news althou it just died short after, it tells me something is quite good.
It´s tuned to make peakpower at ~12000-13000rpm
The dyno was run with KIPS ports closed, and when i came home i opened them again, it´s an certain gain in power what i can feel from my 'buttdyno', dunno how much, but there is a gain, if i´m allowed to guess, at 8500rpm maybe 1 or 2hp.
But way more at 12k rpm, but i can´t say any numbers as i haven´t reached those rpm´s in the dyno.
Home on the street it works just fine.

A question for you guys..
Keihin FCR40, is it possible to get them to work on 2stroke?
Or is there any other good downdraft 40mm carb out there?

Rgds
Patrick

wobbly

21st August 2012, 08:08

All the FCR carbs will work fine on a 2T.
The shroud in the carb bore is the same, as are all the air/fuel circuits the same as a PWK etc, but the FCR has an extra idle fuel jet ( screw adjustable).
The emulsion tube is removeable but is a fixed size.
All the adjustment is done on the needle dia, taper angle and taper start point - as are all Keihin 2T carbs.
To get the standard range of needles to work on a 2T the tube has to be reamed out, as all the 4T setups are very lean.

TeeZee, forget the twats saying detune the GP125 - forget your thoughts on doing anything else at all - make it reliable.
At 30 Hp its fast enough to win anything.
The power being made didnt affect the piston falling into the too wide EX, the power being made didnt overadvance the midrange timing, the power didnt make the ring pin fall out - etc etc

teriks

21st August 2012, 08:26

wax

21st August 2012, 08:29

Shouldnt the wheels point down.

haha

cool toy

Gigglebutton

21st August 2012, 08:48

cotswold

21st August 2012, 09:36

TeeZee, forget the twats saying detune the GP125 - forget your thoughts on doing anything else at all - make it reliable.
At 30 Hp its fast enough to win anything.
The power being made didnt affect the piston falling into the too wide EX, the power being made didnt overadvance the midrange timing, the power didnt make the ring pin fall out - etc etc

Your right Wob
Im no 2t guru, i make stuff, but it seems under stressed compaired to some of the other motors in bucket racing. I think TeeZee could get more out of it if he had more time to think & work on it. Just a few teething problems. Even NASA lost a few pilots :facepalm:

I am even less a 2t guru than Daz but all the issues that have happened to the motor can be ironed out, the ignition curve issue is gone, the port issue is a known factor and now you know the pin needs a blob of weld or some other fixative to discourage it from messing up it's rider. ( we used to weld the top of pistons to re-profile them in the singles any reason you could not counter sink and fill the hole with a bit of ali weld? )
Look forward to seeing Kel back on it as soon as possible

wobbly

21st August 2012, 09:54

If you watch the qual video,only Stoner,Hayden,Spees and Vale were steering with the front in the air at that point.
All crashed except Vale,and he was real close to it - think he would have if the thing would go fast enough.

TZ350

21st August 2012, 12:08

TeeZee, forget the twats saying detune the GP125 - forget your thoughts on doing anything else at all - make it reliable.At 30 Hp its fast enough to win anything. The power being made didnt affect the piston falling into the too wide EX, the power being made didnt overadvance the midrange timing, the power didnt make the ring pin fall out - etc etc

Yes your right, its just mechanical details now for reliability and we need to work on setting up the handling.

If I was going to do anything tuning wise now it should be to try and extend and plump up the lower end of the torque curve for drivability.

We had hoped to spend the last race meeting tuning the handling but having the directive to enclose the carb inside a catch tank sprung on us at the last minute left us scrambling to get it running right again which is a bit much on a race day.

We need to go down on a practice day and take our time to get things right, dynos are OK but its the track where its at!

Thankfully Kel is still keen.

F5 Dave

21st August 2012, 12:30

As long as it runs cleanly enough to transition; no one really cares what it pulls like at 9000.

richban

21st August 2012, 13:01

Kel called around today with his arm in a cast, broken bone in his hand and elbow, 6-8 weeks before the cast comes off, so just in time for the start of the North Island Series.... :D ..... well hopefully.

Thats bad news. Mend quick Kel. When I first saw the images I thought he was practicing his drifting with the smoke and all. Amazing job on the photos as usual from Damien.

SS90

21st August 2012, 13:55

TeeZee, forget the twats saying detune the GP125 - forget your thoughts on doing anything else at all - make it reliable.

The power being made didnt affect the piston falling into the too wide EX

Quite right, however, using the same logic, we could also say that the poxy single exhaust port, combined with the necessary BDTA required to achieve this power has overstepped the boundaries of mechanical reliability.

Would reducing the width of the exhaust port (given the duration is already too much, and therefore Foolhardy to increase) not reduce the the BDTA, and therefore, infact, be "detuning" the engine?

Dropping 2 P.S and designing an exhaust and cylinder head for what can only be described as massive gains, and designing an exhaust to suit (bearing in mind they only have 5 Ratios to transmit this through)

Better spreads of power are made everyday with far less of the gubbins this poor old whipped mule has.

Either that, or some sort of solution to the too wide exhaust port has to be found.... Maybe an exhaust bridge of some sort....?

Drew

21st August 2012, 14:12

Quite right, however, using the same logic, we could also say that the poxy single exhaust port, combined with the necessary BDTA required to achieve this power has overstepped the boundaries of mechanical reliability.

Would reducing the width of the exhaust port (given the duration is already too much, and therefore Foolhardy to increase) not reduce the the BDTA, and therefore, infact, be "detuning" the engine?

Dropping 2 P.S and designing an exhaust and cylinder head for what can only be described as massive gains, and designing an exhaust to suit (bearing in mind they only have 5 Ratios to transmit this through)

Better spreads of power are made everyday with far less of the gubbins this poor old whipped mule has.

Either that, or some sort of solution to the too wide exhaust port has to be found.... Maybe an exhaust bridge of some sort....?Did you get beat up a lot as a kid?

Nevermind.

Why are you the only guy saying this? In a forum with half a dozen dudes that seem to know their shit, no one else is bringing this obvious issue to light. It's very confusing for the totally ignorant like myself.

That is how you form a question, and reason for said question in English by the way.

richban

21st August 2012, 14:26

We had hoped to spend the last race meeting tuning the handling.

After lots of research, learning and talking to people that know more than me. I am super committed to get my new bike to handle superbly. In buckets I think it is the most overlooked performance upgrade. Not much point having lots of grunt if you can't turn it on. I will run the slow engine at first to really test the chassis. I figure I will have to ride it harder to keep up. After she rails I will chuck in some HP and get lazy again. I am aiming for a 23 degree steering angle with rider sag setup at 30 front 20 rear. Will see how that works out.

wobbly

21st August 2012, 14:28

The Ex port isnt the problem here.
At 72% width it will live forever, and at 78.5 ATDC who says its too high, it will support near on 40 Crank Hp.
The STA numbers show the Blow will support near on 40 crank Hp as well, so the system is inherently a match, and if the ports and pipe are SOTA it WILL make 40 crank Hp - with plenty of powerband width.
Its all but been done already, without trick shit transfers or pipe..
What IS the issue is the inlet port and its tiny carb, this is where all the effort needs to be directed, and TeeZee has already done a heap.
The sidetracks of Ex port width and ignition anomalies is simply an artifact of TeeZee learning what not to do in public.
He could have simply given it to me with 5K and it would have been a winner - how would he ( or anyone else ) learn jack shit from that.

jasonu

21st August 2012, 14:31

We had hoped to spend the last race meeting tuning the handling but having the directive to enclose the carb inside a catch tank sprung on us at the last minute left us scrambling to get it running right again which is a bit much on a race day.

Thankfully Kel is still keen.

Where did this 'directive' come from?

TZ350

21st August 2012, 15:23

Where did this 'directive' come from?

It was an internal team thing, people at Mt Welly are starting to become conscious of oil spills in general and Chambers wanted Team ESE to be above reproach.

Brian d marge

21st August 2012, 15:27

After lots of research, learning and talking to people that know more than me. I am super committed to get my new bike to handle superbly. In buckets I think it is the most overlooked performance upgrade. Not much point having lots of grunt if you can't turn it on. I will run the slow engine at first to really test the chassis. I figure I will have to ride it harder to keep up. After she rails I will chuck in some HP and get lazy again. I am aiming for a 23 degree steering angle with rider sag setup at 30 front 20 rear. Will see how that works out.

Havent heard this one in a while , well done ,

Stephen

bucketracer

21st August 2012, 17:04

So shot ourselves in the foot again but in a different and more imaginative way this time.

There you are TeeZee, ... its SS90 your very own devoted detractor, I expect Burt Munro had one of these too….

..... the bike in question just seems to be being tuned to a standstill …. People can jump up, Lay eggs, and wave pitch forks about all they like, I feel this is a valid point.

… one would have to wonder if someone is heading in the right direction... As you can produce an immense amount of torque from a two stroke, with-out any of the crap that thing has bolted on to it.

Better spreads of power are made everyday with far less of the gubbins this poor old whipped mule has.

husaberg

21st August 2012, 18:05

There you are TeeZee, ... its SS90 your very own devoted detractor, I expect Burt Munro had one of these too….

F sakes, Why does anyone even respond to his posts.
If you ignore him perhaps he will go away.
Oh well that theory doesn't work with me either:innocent:

Anyway back to constructive stuff, (rather than the vile ranting of a ....Vile ranter) as everyone has said get it reliable it is just detailed stuff.
Yes i know the devils in the detail:devil2:
Rob will forgive me for saying (i hope) that at times he is a little keen to try to many things at once, occasionally with mismatched parts.
Youthful over exuberance i guess.

Most people are guilty of the same (myself included although i suffer chronic procrastination as well)
Development gains often require a methodical somewhat restrained approach. This i guess is were the Japanese and Dutch really excel.

Now don't get me wrong.
Rob leaves no stone unturned in his pursuit of Bucket nirvana. He is open friendly, forgiving, thoughtful, insightful and incredibly enthusiastic
I hope no one takes this the wrong way (Except Neil) as i have met Rob and respect him both as a person and a Classic Kiwi can do Bloke.

Oh An actor to play SS nighty. Narh even Actors have moral standards, maybe a reality "star" nah again to much talent
Maybe a blogger who is famous just for his nasty rants.
http://t1.gstatic.com/images?q=tbn:ANd9GcQ-4VB8FOEjj5ndQ3HF7O2WYdy_8kyn8htPn1BdbYWn2wrh1v4vcg&t=1

F5 Dave

21st August 2012, 18:09

I'm confused:wacko: so who is going to play Anthony Hopkins in the movie about Rob racing old Suzukis in a few years time? And who will be Clarice Starling? perhaps SS90 will be available if Jodie Foster isn't. I mean we might as well turn this into a fusion adversity over Thriller Horror movie:blink:.

richban

21st August 2012, 18:52

The thing that pisses me off is that SS90's are cool. I know a guy in germany the collects them and lots of other global vespa people. They are really cool people doing amazing things with the old airplane starter motors that they are. SS90 is giving them a bad name. TZ is doing an amazing thing here. Its like open source for 2 stroke tuners. If i didn't have connections on the dark side of the force I would be implementing the gold that has been laid down in this thread across the years? Not sure when it started now. Fuck off 90 or have some respect. Cock.

wobbly

21st August 2012, 19:09

My votes for playing Tee Zee are Woody Harrelson, only just ugly enough.
But the shoe in for SS90 has to be Sharon from Kath and Kim - perfect likeness - always seeking attention and obviously just fukin dumb - from everything she says..

Farmaken

21st August 2012, 19:44

Bang on wobbly, go hard TZ.

:drinkup:

Yow Ling

21st August 2012, 21:18

http://www.youtube.com/watch?v=236YXw-5Xkw

Could this possibly be SS90 on his high powered bucket buster?

I think it is !

Bert

21st August 2012, 21:56

........
TeeZee, forget the twats saying detune the GP125 - forget your thoughts on doing anything else at all - make it reliable.
At 30 Hp its fast enough to win anything.
The power being made didnt affect the piston falling into the too wide EX, the power being made didnt overadvance the midrange timing, the power didnt make the ring pin fall out - etc etc

Quite right, however, using the same logic, ######### to achieve this power has overstepped the boundaries of mechanical reliability.

Would reducing the width of the exhaust port (##########) not reduce the the BDTA, and therefore, infact, be "detuning" the engine?

Dropping 2 P.S and designing an exhaust and cylinder head for what can only be described as massive gains, and designing an exhaust to suit (bearing in mind they only have 5 Ratios to transmit this through)
########
Either that, or some sort of solution to the too wide exhaust port has to be found.... Maybe an exhaust bridge of some sort....?

Devils advocate... (not forgetting my only red rep since 2005 came from SS90)..here Page145!! (http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1129703743#post1129703743)
I think we might be all "trigger fingering" a little fast here towards SS90 (all be it removing the history ###). He does have a couple of valid points which has been discussed here over the past 12-18 months. Suzuki never designed the GP125 for these types of performance figures; TZ (and the entire team ESE) has done some amazing work in public space proving that is it possible to do to the poor old thing.

SS90 has posed a couple of valid questions here (useful mainly for people thinking of following the ESE lead in building a GP125 racer).
30 Hp is achievable (following the great resources on this thread) it may actually be pushing past the mechanical boundaries of the actual engine design; would 27-28 be the same??
and is it's overall performance ultimately limited by the 5 speed box?? (would you actually notice 2-3 peak HP??)
Could a new sleeve with a bridged exhaust port offer a better overall solution to reliability?? (I ask this as my 100 is on the limit as well & we have discussed the merits of this a while back)...
what actually caused the ring pin to fall out? (who actually knows) but Yamaha TZs did have issues here in the past; ironic given that they also had large single exhaust ports (is it a ring hammering effect caused by the ring passing in and out of the wide exhaust port? resulting in pin issues) I have some vague recollection of someone (s) telling me that I was in for similar issues....

Kel; bad luck mate heal fast; its not the best fun being the crash tester...

Frits Overmars

21st August 2012, 22:07

To give you some idea of what I'm messing with, something completely off topic. -except for being two-stroke and somewhat bucket, as in old engine, well, and some tape and tie wire.
268553
.. or maybe I just like the beautiful blue color and need to share it somehow ;)Gee, that's the old MB40 engine with rear inlet valve and clumsy cylinder fixation - three bolts going down from the cylinder into the crankcase and two going up from the crankcase into the cylinder which means you have to remove the engine from the plane each time you want to pull the cylinder down. It was a learning curve for us :rolleyes:.
I can't tell from your picture but chances are it even has a steel crankcase.
Here's some noise trom the little miracle: http://www.youtube.com/watch?v=5aBCQGq5Al4

andrew a

21st August 2012, 22:12

Hi guys just poped onto this threed and saw Kels pics. Impresive. Sorry to hear about broken bones though. Hope it heals well.
Keep up the good work guys. I find it dificult to see where you get the time.

bucketracer

21st August 2012, 23:15

SS90 has posed a couple of valid questions ...

Re read the original SS posts, valid questions sure, genuine even, they could have been if they had been asked without the embellishments.

..... the bike in question just seems to be being tuned to a standstill …. People can jump up, Lay eggs, and wave pitch forks about all they like.

… one would have to wonder if someone is heading in the right direction... As you can produce an immense amount of torque from a two stroke, with-out any of the crap that thing has bolted on to it.

Better spreads of power are made everyday with far less of the gubbins this poor old whipped mule has.

So whats your take on the superfluous verbiage in his posts.

Maybe SS90's posts were genuine, so here they are answered by a genuine industry insider.

The Ex port isnt the problem here.
At 72% width it will live forever, and at 78.5 ATDC who says its too high, it will support near on 40 Crank Hp.
The STA numbers show the Blow will support near on 40 crank Hp as well, so the system is inherently a match, and if the ports and pipe are SOTA it WILL make 40 crank Hp - with plenty of powerband width.
Its all but been done already, without trick shit transfers or pipe..
What IS the issue is the inlet port and its tiny carb, this is where all the effort needs to be directed, and TeeZee has already done a heap.

The sidetracks of Ex port width and ignition anomalies is simply an artifact of TeeZee learning what not to do in public.

husaberg

21st August 2012, 23:20

Here's some more Helmholtz-encouragement:

Regarding induction systems: build a short induction tract and visit a test bench.
You can forget about calculations. The formulas you find in various books are all based on the Helmholtz resonator. It made me write a simple story, called:
Helmholtz blues
"A Helmholtz resonator consists of a volume connected to a duct". That is what Wikipedia tries to tell you.
But that is a Helmholtz resonator in its simplest form; one that you won't find anywhere in an engine.
What you do find in an engine is an intake tract with a variable cross-sectional area. This tract is from time to time connected to a variable volume (the crankcase) through a very variable window (the intake port / reed valve / rotary inlet).
The crankcase is connected to a number of transfer ducts with variable cross-sectional areas, which are from time to time connected to a very variable volume (the cylinder) through a number of very variable windows (the transfer ports).
The cylinder is from time to time, through a very variable window (the exhaust port), connected to an exhaust pipe with a very variable cross-sectional area who at the same time doubles as a volume. This pipe volume is constantly connected to a big volume (the outside world) through a tailpipe with a constant cross-sectional area and constant entry and exit windows (thank God, finally someting that's not variable).
We call this a compound Helmholtz resonator .
The various papers also tell us how to calculate the resonator's frequency:
" frequency = speed of sound / (2*pi)* Sqr ( cross-sectional area of the neck / ( volume of the resonator * effective neck length ) ) ".
O yes, the speed of sound... It is dependent on temperature, which is not really constant in the intake tract and the crankcase, rather variable in the transfer ducts and very variable in the cylinder and the exhaust pipe.
Now the above frequency formula is not exact; it is an approximation that is usable as long as the volume of 'the' tract is very small compared to the resonator's volume.
So when engines are concerned, that formula goes very far out the window.
Who said gas dynamics is simple dull?
PS:
It's a similar story with acoustics. That is a sub-branch of gas dynamics, simplified with a lot of assumptions that are acceptable as long as the sound pressure does not exceed a certain limit. The wave pressures in a two-stoke exhaust exceed that limit by a factor of thousand. Bye bye, acoustics...

I think i found the bit where i misquoted Frits from. Bloody couldn't find it last time.

Helmholtz frequency, my dear Watson. The smaller crank will give the pipe more crankcase volume to breathe from. This larger volume will also lower the resonance frequency of the inlet system, hence the drop at high rpm. It can be compensated with a shorter inlet tract, a bigger carb diameter and a later inlet closure. To put it real simple: if you have more volume, you need more time to fill it. But more time, i.e. later closure, has adverse effects at low revs. So my preference is a shorter tract (unless you go the 24/7-way and employ a reed for the low revs, and swing it out of the way at high revs).

teriks

21st August 2012, 23:23

Gee, that's the old MB40 engine with rear inlet valve and clumsy cylinder fixation - two bolts going down from the cylinder into the crankcase and two going up from the crankcase into the cylinder which means you have to remove the engine from the plane each time you want to oull the cylinder down. It was a learning curve for us.
I can't tell from your picture but chances are it even has a steel crankcase.
Here's some noise trom the little miracle: http://www.youtube.com/watch?v=5aBCQGq5Al4
Thats the one, steel crankcase from 1999, new cylinder though. My favorite cyl. from 1999 finally gave up in June, cracked around one of the head bolts. -Robust stuff :-)
I'm using the old stuff for fun, and to try a lot of stupid and a few not so terrible things on. The fun part is when i can keep up with the latest generation engines speed-wise ;)

My rather long term plan is to build my own rear induction crankase for the long-stroke, the design is coming around ever so slowly...

Bert

21st August 2012, 23:49

Re read the original SS posts, valid questions sure, genuine even, they could have been if they had been asked without the embellishments.

So whats your take on the superfluous verbiage in his posts.

Maybe SS90's posts were genuine, so here they are answered by a genuine industry insider.

hence the #### not ..... in the quotes ;)

My take; maybe too much time in the eastern block ?? banging his head against a wall dealing with scooter people???

the point I was making is that maybe there is scope in his points (he is also not alone in his comments about bridging the exhaust port to limit ring issues and gaining optimum durations and performance; I'm sure I recall Wobs being part of that as well ---I'll go look for it might be wrong).

ief

22nd August 2012, 02:34

Could it be that the exhaust outlet does have something to do with it, not by being to large then but by being unsymmetrical?

wobbly

22nd August 2012, 07:40

You guys arent getting it at all.
All the issues that the GP125 engine has had, have NOTHING to do with the power it makes.
It would have died at 22 Hp with the Ex port too wide.
It would have died at 17 Hp with the incorrect ignition timing
It would have died at 12 Hp when the ring pin fell out.
Need I go on.
Of course all this type of shit normally happens behind closed doors and gets chalked up to experience.
Its being done here in the open for everyone to learn from.

FastFred

22nd August 2012, 07:43

We had hoped to spend the last race meeting tuning the handling but having the directive to enclose the carb inside a catch tank sprung on us at the last minute left us scrambling to get it running right again which is a bit much on a race day.

Chambers points out, it was a team decision and you had a week and a half ...... :devil2:

TZ350

22nd August 2012, 08:07

crazy man

22nd August 2012, 08:10

why dont you back the engine of 2-3 hp and see if it fixes the pomblem if not you know it was not that . my sidecar years ago tf 100 sezed up twice so l backed the timing of just a tad and a bigger main in it . ran it for 2 years won the sidecar titles twice never did a thing to it untill the big end went.. food for thought

crazy man

22nd August 2012, 08:22

have you ever had the bike seized on the dyno at all? if so was it the roll down or do you pull the cluch in as it rolls down?

teriks

22nd August 2012, 09:44

I like it, and the blue color, thats seriously interesting.
Thanks! Apart from beeing beautiful, the color gives gives you a decent indication on pipe surface temperature using something like: http://www.uddeholm.com/files/Temperature_guide.pdf or http://www.smex.net.au/reference/steelcolours.htm

RAW

22nd August 2012, 10:53

jasonu

22nd August 2012, 12:47

It was an internal team thing, people at Mt Welly are starting to become conscious of oil spills in general and Chambers wanted Team ESE to be above reproach.

Really??? Sorry mate but I smell:bs: Most of the oil on the track comes from the Karters chain oil.
I hope new rules were not made without proper discussion and proof.

crazy man

22nd August 2012, 13:35

Massive waste of brain interlek being thrown back and forth here, how have we ended up so far off track ? ( pun intended ) what was it that stopped this machine, as Wob has stated A RING PIN, just address the fault and move forward again, leave this garbage talk with the garbage talkers::nono:sleep:all l read was (The engines symptoms looked the same as Taupo and Kaitoki ) so just trying to help what l thought was the same promblem happing!

TZ350

22nd August 2012, 14:21

Really??? Sorry mate but I smell:bs: Most of the oil on the track comes from the Karters chain oil.
I hope new rules were not made without proper discussion and proof.

No not a rule change, and I used the wrong word when I said "directive" it was a team decision taken as some of the kettles have been overheard worrying about the color of the pots. I got my bottom polished and maybe thats a good thing as it looks like the whole Mt Welly kitchen is headed for an oil hygiene scrub up.

jasonu

22nd August 2012, 15:07

No not a rule change, and I used the wrong word when I said "directive" it was a team decision taken as some of the kettles have been overheard worrying about the color of the pots. I got my bottom polished and maybe thats a good thing as it looks like the whole Mt Welly kitchen is headed for an oil hygiene scrub up.

Yes that is about what I thought happened. Is the kart club getting involved?

TZ350

22nd August 2012, 15:58

Yes that is about what I thought happened. Is the kart club getting involved?

No no, still pretty low level ... at the last wet Bucket meet there was quite an oil sheen developing during the day.

TZ350

22nd August 2012, 16:01

have you ever had the bike seized on the dyno at all? if so was it the roll down or do you pull the clutch in as it rolls down?

Usually a bit of both, roll off then pull the clutch if the run down is taking to long. Run down on the dyno takes much longer than normal overrun into a corner so I often pull the clutch but not always. We realy need a brake on the dyno drum.

Yes I have had a seizure on the dyno during a pull, I was impatient to get going and it was a cold seizure as I hadn't warmed it up very well.

Wob points out that after maximizing the ignition on full throttle runs on the dyno, if I had closed the throttle a bit at peak torque the engine would have seized.

I can certainly see that could happen now that I have that knock sensor because on over run and lower throttle runs it often lights up like a Xmas tree when it wouldn't have if it was a full throttle run.

crazy man

22nd August 2012, 17:57

after my brother had seized his rs125 lots of times we brought a det counter . never seized it again . all it took was some cloud cover and the dets just went up by thousands but after awail we did sort it to run safe. but everything is a learning curve

bucketracer

22nd August 2012, 21:14

TeeZee has a knock sensor thing connected to his ignition which retards when it senses detonation but I think he would like a det counter too but does not know where to get one or at least an affordable one. If someone has one for sale, I know TeeZee would like a PM.

Buckets4Me

22nd August 2012, 21:21

wobbly

23rd August 2012, 08:10

$80 gets you a self powered counter.
http://www.intech.co.nz/catalogue/download-pdf-individual/114-Catalogue-nz.pdf

RS will do one as well im sure.

TZ350

23rd August 2012, 18:44

$80 gets you a self powered counter.
http://www.intech.co.nz/catalogue/download-pdf-individual/114-Catalogue-nz.pdf

RS will do one as well im sure.

Yes, thanks I will have a dig through the RS catalog.

speedpro

23rd August 2012, 19:11

Possibly kj8234 from Jaycar, $28.90ea plus a little box to put it in.

RMS eng

23rd August 2012, 19:51

Yes, thanks I will have a dig through the RS catalog.

I got one for a RS125 Karter from Kevin at Race supplies,if your running Av gas you may be better with a exhaust temp set up.

TZ350

24th August 2012, 08:11

Thanks for the tip ...

F5 Dave

24th August 2012, 09:37

Just a note of vigilance for the builders of anything fabricated. Remember to leak test. I'm chasing all sorts of holes from crazy areas currently. leak tester has been covered several times. Inlet area is always a favourite.

TZ350

24th August 2012, 10:19

Just a note of vigilance for the builders of anything fabricated. Remember to leak test.

We currently don't have a tester and have paid the price on one of the other Team ESE bikes, I am off to SuperCheap/Repco/CarParts place to find a Radiator Tester, actually when you think about it they can't be that hard to make.

Pictures of a commercial and homemade radiator tester.

F5 Dave

24th August 2012, 10:37

Just a 3 way gas fitting (in/ gauge/ out) from Paykels -a scrader valve for a bicycle pump is the 'in'.
5psi is enough. Then some blanking plugs for the inlet & exhaust. The inlet for the engine can be into one of these fittings, or a hollowed out sparkplug.

Ocean1

24th August 2012, 10:54

F5 Dave

24th August 2012, 11:18

yes indeed, a squirty bottle filled with something bubbly. I haven't moved to liberate the kids bubble mixture, its overkill, just some soapy water is enough.

wobbly

24th August 2012, 12:58

dinamik2t

24th August 2012, 14:05

You can cheaply make your own -trustworthy- tester:

268701268702268703268704

All you need is a pressure gauge of 5~10 psi, a hand rubber 'squeeze' pump (medical store), some carb hose, a Y connector and 2 rubber plugs (chemistry shop) with diameters equal to your exhaust and inlet manifolds respectively.
I found everything on ebay because I was bored, but one can definately search the local market and pay no more than 15$.

Fooman

24th August 2012, 14:58

The problem with a rad leak tester is that if you have a leak - the thing runs out of psi before you can find where its going.
I use my Oxy bottle, i set the guage to 5 psi and fill the engine - you can then run around with a soapy water brush and test all the seals and gaskets.
When you have fixed any issues, then re pressurise the engine and turn off the bottle valve - the guage shouldn't move for 10mins if all is well.

Hi Wobbly,

I think that is very poor advice for one particular reason: I would not use pressurised oxygen on anything that is potentially exposed to oil or grease. In 100% oxygen - even at atmospheric pressure - fuels, oils and greases can spontaneously ignite. A blob of grease saturated in oxygen is essentially a blob of high explosive. A colleague of mine once had to investigate a death resulting in the inflation of a tire with oxygen (the oxy bottle was conveniently located) rather than air or nitrogen. The oxygen caused the sealing grease on the bead to ignite/explode, next to the guy who had just made his last mistake.

Air from a compressor? OK. Argon/mix from a MIG/TIG bottle? Better. Oxygen? No way.

Cheers,
FM

Drew

24th August 2012, 15:08

Hi Wobbly,

I think that is very poor advice for one particular reason: I would not use pressurised oxygen on anything that is potentially exposed to oil or grease. In 100% oxygen - even at atmospheric pressure - fuels, oils and greases can spontaneously ignite. A blob of grease saturated in oxygen is essentially a blob of high explosive. A colleague of mine once had to investigate a death resulting in the inflation of a tire with oxygen (the oxy bottle was conveniently located) rather than air or nitrogen. The oxygen caused the sealing grease on the bead to ignite/explode, next to the guy who had just made his last mistake.

Air from a compressor? OK. Argon/mix from a MIG/TIG bottle? Better. Oxygen? No way.

Cheers,
FM:eek5:

Well buggery bollux, good to know.:confused:

Yow Ling

24th August 2012, 15:22

Use acetylene then you dont have to fuck around with the soapy water , just run your lighter over it

F5 Dave

24th August 2012, 15:35

Fooman doesn't show up often but what he writes makes for interesting reading. A mysterious chap who I haven't laid eyes on for many many years despite living about 10 doors away for several years. I think.

I prefer a hand pump (and Jason can shut up for the rude remark he is forming as he reads that) as I can't have a whoopsy & over-pressurise the engine with a dicky regulator or operator error. I used to use 10psi but have been told that is too high & can damage seals &/or cause leaking seals to seal by pressing them harder against the shaft.

Even with 10psi I used to use table leg bungs in the inlet manifold & they would get spat out occasionally with a surprising POP! & flight. I now try to get a convienient piece of Acetal with a groove turned in like a carb.

wobbly

24th August 2012, 15:48

Sorry you are right , I use ARGON from my tig set, why the hell I wrote Oxy with no Alky in my system is a mystery.
An air compressor with a reg would work fine, the point was that i pump up 100s of engines and got sick of pumping furiously whilst trying to find the leaks - needs 3 hands.

Fooman

24th August 2012, 15:50

Fooman doesn't show up often but what he writes makes for interesting reading. A mysterious chap who I haven't laid eyes on for many many years despite living about 10 doors away for several years. I think.

Don't worry, I salute your place every morning I drive past dropping the sprog off to school.

Far too busy being an international man of misery these days. But I did notice an early version of your 50 while wandering through SFO airport earlier this year:

268707

Fooman

24th August 2012, 15:54

Sorry you are right , I use ARGON from my tig set, why the hell I wrote Oxy with no Alky in my system is a mystery.

Thats good to hear! Thanks for the clarification :)

...got sick of pumping furiously...

Ever think of hiring a glamorous assistant?

Cheers,
FM

Fooman

24th August 2012, 16:00

I prefer a hand pump ... as I ... have a ... dicky ... error. I ... use 10psi ... pressing ...harder against the shaft.

Sounds like you need a glamorous assistant as well...

Cheers,
FM

RMS eng

24th August 2012, 16:00

F5 Dave

24th August 2012, 16:02

That 50 is Kewl!@

F5 Dave

24th August 2012, 16:04

and the last thing you guys need is a nother thing to blow your motors up

and the only blowing up you do these days is that doll that you hide in the garage cheeky git.

jasonu

24th August 2012, 16:43

jasonu

24th August 2012, 16:46

and the only blowing up you do these days is that doll that you hide in the garage cheeky git.

He doesn't hide it...

TZ350

24th August 2012, 17:22

Page 590 ...

jan thiel on part throttle deto

"I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling."

No answer here but at least we are not alone with engines that fail on part throttle

http://www.pit-lane.biz/t3173p60-gp1...vermars-part-2

Brian Callahan
Jan or others, how did you control the tuned pipe wall temperature (or EGT directly?) when testing on dyno? This seemed the most difficult thing to mimic when testing either the GP engines at QUB or my R/C boat engines, in the lab. The inertial dyno or computer controlled brake seem to work best because we can match the test engine's acceleration with reality. On steady-state testing, EGT would simply climb 500, 600, 700, 750 °C until way past reality and the piston would seize.

Frits Overmars
This has always been one of Jan's greatest handicaps. He has asked for an inertial test bench over and over, but Aprilias race director Witteveen, or The Great Leader as we call him, never deemed it necessary....

Jan Thiel
When EGT goes up and up there should be some serious problem with the engine.
We never had pistons seize during our steady state tests.
Working on the dyno continuously 5 days a week!
I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling.

As Frits has written, I would have liked to have also a dynamic testing possibility, with a flywheel.
In my opinion you should simulate a straight, starting at around 10.000 rpm, and shift through the gears
until you reach top speed. And with the airbox as used on the bike, with a ventilator that simulates the raising
air speed as it would be on track! Maybe it is interesting to know that without a ventilator the engine gave
less power with the airbox fitted.

I was told that such a testing system was too expensive.
And unnecessary as we won anyway!

I can also see a disadvantage of 'dynamic' testing.
Because the duration of the test is so short you can get away with very extreme (too extreme?) settings,
without damage.

GrahamB
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Haufen
Yes I know, but part load egt is usually lower than full load egt. And I think most of us would prefer higher part load egt over part load detonation. Of course, how far one could go and how far one would need to go would have to be tested, and how much would be needed would depend on the engine.

Mic
How about much larger travel on the exhaust power valve.
With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Jan Thiel
This causes detonation (auto ignition)
The problem is that the burned gases do not exit the cilinder!
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Jan Thiel
Haufen, We also had such a test bench at Aprlia.
The prototype of this test bench was developed by Apicom in collaboration wit Aprilia.
So we had it first, and now anyone can buy it.
It was helpful but not what I wanted.
A so-called step test.
And without the airbox!

Frits Overmars
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below, but then two-stroke development at Aprilia was terminated because of Dorna's ban on two-strokes

Howard Gifford
Another way to lower HP without sacrificing piston cooling would be to richen the mixture when you want to lower the power. With a signal to a fuel enrichening solenoid you could achieve a power range. It would then be instantaneous and programmable. Not enviornmentally friendly but would work for racing. The mixture ratio difference from high power to low power would need to be just rich enough before a misfire and just lean enough for sustained high power.

The variable tailpipe idea will work but I suspect the pipe temperature would drop off and it would take several seconds to regain full power. But then again rich mixture may have the same problem.
Two strokes are like redheads. Hard to figure out and very temperamental. But when they are happy they are a lot of fun!
HG

Jan Thiel a écrit:
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.

Institute of TwoStrokes
On aftermarket ignitions I use there is a mode I can switch on where a number of indivdual sparks are cut, depending on throttle position. It is now only configured for cutting 1 in every 3 sparks on over run(tps <10% with high rpm). Would that sort of system solve the part throttle detonation? If the number of sparks cut could be varied along with TPS for this to begin and end? If it would be helpful I'm certain the manufacturer would only need a software change to do this.

Jan Thiel
I certainly thought about cutting sparks.
But remember: the problem was AUTO-ignition!

GrahamB a écrit:
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Jan Thiel
Indeed, retarding too much caused detonation!

Institute of TwoStrokes a écrit:
Jan Thiel a écrit: The entering fresh charge is ignited by the remaining, hot, burned gases! You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? On aftermarket ignitions I use there is a mode I can switch on where a number of individual sparks are cut, depending on throttle position. Would that sort of system solve the part throttle detonation?

Frits Overmars
As Jan pointed out, once you have auto-ignition, the engine does not listen to its ECU any more. So you would have to start skipping sparks well before the onset of detonation.
In a foul-stroke your proposed system does work, but a two-stroke would react far from linear. For example, if you skip 1 in 4 sparks, you will loose much more than 25% of engine power because that one missing spark will cause the gasdynamics processes to collapse. The main problem would be to realise a smooth transition from intermittent to full ignition.

Jan Thiel a écrit:
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Haufen
I think I expressed myself unclearly. What I meant was the following:
Imagine your engine with the throttle opened just above the auto-ignition range. Then you have sufficient transfer flow, but too much power. To lower the power, now retard the ignition. Then you still have sufficient transfer flow, but with less power.

I think Honda used auto-ignition to their advantage on two-strokes. As far as I remember they did it with a (very) variable exhaust power valve.

Frits Overmars a écrit:

Mic a écrit:
How about much larger travel on the exhaust power valve. With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Frits Overmars a écrit:
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below.

269232

Haufen
I think I have not gotten behind the variable tailpipe idea, yet. What would you like to vary with it and to achieve which effects? At little throttle openings the pressure inside the exhaust pipe is already very close to atmospheric pressure (if not even) on most engines. And if you had say 100mbar inside the pipe at the critical throttle opening, then the engine might have had more power with a bigger tailpipe.

Frits Overmars
'Opening' the end of the reflector will cause a substantial weakening of the reflected pulse and thus less charging of the cylinder. Izze simple, no?

Haufen a écrit:
Variable transfer timing would be nice also, if feasible.

Frits Overmars
That would be my ideal. Lowering all the transfer roofs would shorten the transfer timing and lengthen the blowdown timing, so the cylinder pressure would drop further before the transfers would open. It would cure the hig revs/low power-detonation and it would improve the power band because a too early-returning exhaust pulse would have less opportunity to push the fresh cylinder contents back into the crankcase.
A controllable transfer height would even make a throttle valve unnecessary.
There's only the little problem of how to build it...

Jan Thiel
Haufen, Auto-ignition usually occurs between 10 to 40% throttle at high revs.
In fast, non full throttle corners.

Retarding the ignition was tried to diminish power.
This makes the exhaust very hot.
Then, when you need full power, it is not there because the exhaust temperatures are wrong.
This takes a little time, when the engine is back to full power you are already at the end of the straight!
The same goes for water injection in the exhaust.
It was tried by Rotax about 25 years ago.
There was a LOT more power at low revs, so the rider had to take it easy when opening the throttle.
But the engine revved a little bit less, because the exhaust temperature did not recover at high revs.
And lap times became actually slower.
After a day of testing the system was switched off.
Lap times immediately improved!

A very important thing when accelerating is the power you have after changing gear.
Spark interruption may be not so good for this!
As I did not have the dyno I wanted this gearchange effect could not be tried on the dyno, very regrettably!
Retarding the ignition and weakening the mixture by powerjet can also have a negative effect on this.
The exhaust temperature should be 'Right' for the No. of revs after you change gear.
If the temperature is too high there will be less power!
So it is REALLY complicated!

F5 Dave

24th August 2012, 17:25

Does that mean its time for a friday afternoon Musical Interlude?

http://www.youtube.com/watch?v=8d9E-8yGlVo

Frits Overmars

24th August 2012, 18:23

In addition to engine leak testing I like to test piston ring leakage.
You don't need to plug any inlet or exhaust openings. Just connect the contraption in the drawing below to a compressed air line and to the plug hole, and hold the crankshaft in a position where all ports are closed.
Close the valve and set the pressure on the gauge to a fixed value that you will always use. Then open the valve.
If the ring seals 100%, the gauge will rise to 100% of the pre-set pressure, no matter how narrow the restriction is.
If the ring doesn't seal at all, there will be no pressure build-up in the cylinder and the gauge will show zero.
With this setup I have even been able to tell at which side of the piston the ring got stuck in the groove: the con rod inclination will push the piston to one side of the cylinder and lift the ring from the other side if it is stuck at that other side.

F5 Dave

24th August 2012, 22:57

that was the method some kart chap was describing, but I'd never heard anyone else doing such. He then started wibbling on about running in on non synthetic & my eyes glazed over, but maybe I should re-evaluate my preconceptions. and build such a rig. thanks
I can see the 'Did it pick up' question could be answered in many cases with such a rig.

Ocean1

25th August 2012, 11:49

Just connect the contraption in the drawing below to a compressed air line and to the plug hole

I cleaned most of my workshop looking for my version... it's gone. Mine had a needle valve where your restriction is as well as a ball valve on the downstream side of the gauge. For normal use the PRV was set to about 20psi, close the needle valve to test leakage, back on to re-set.

It'll turn up one day, you wait.

Frits Overmars

25th August 2012, 21:55

I cleaned most of my workshop looking for my version... Such an experience will influence your workshop like a new girlfriend will influence your house :shifty:.

Ocean1

25th August 2012, 22:01

Such an experience will influence your workshop like a new girlfriend will influence your house :shifty:.

I found it. In my other workshop. :shifty:

TZ350

26th August 2012, 14:39

268797 268798 Richbans Bucket Build.

This is a seriously good looking F4 bike ...... very impressed ...

husaberg

26th August 2012, 15:55

<center>Great looking all right esp for a Suzuki....<center>
<center><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=268798&d=1345882136" width="455px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=267920&d=1344503767" width="340px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=268803&d=1345956041" width="340px"/>

Honda wheels, Honda frame, Honda forks, Honda brakes, Keihin carb (Honda owned)
Now if he runs a Honda full fairing and Honda Seat, so as to totally hide that FXR engine.

It could be the most beautiful bike Suzuki never made.........:innocent:

http://www.kiwibiker.co.nz/forums/showthread.php/151176-NSR-FXR-The-New-No45

Bert

26th August 2012, 15:55

something for a sunday smile:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=261084857319&ssPageName=ADME:B:WNA:US:1123

diesel pig

26th August 2012, 17:49

bucketracer

26th August 2012, 18:40

... reving the bucket up the gauge went off like a christmas tree and I am wondering what others have there gauges set to? ...

We have one of those but only learning about these things ourselves. And this is how we think it works if that's any help.

Knock rings in the cylinder like a bell.

The ringing has a frequency that depends on the size of the cylinder, bigger the cylinder/combustion chamber the lower the frequency.

The adjustment on the knock gauge selects this frequency much like tuning in a radio station.

The adjustment on the knock gauge is not about adjusting the loudness of the radio station.

To tune the knock gauge in you adjust the knob until you see two strong green lights when accelerating.

We think the two green lights indicate the knock gauge is tuned in properly.

It would worry me if I was seeing the red deto light at this point and start backing the ignition off or richin it up.

On our first dyno runs with the knock gauge we saw perfect green on the pull and red xmas tree lights on the run down so it was detonating badly on run down with a closed throttle.

TeeZee's is set at about a 1/3rd.

We would love to hear more from someone with experience using one of these knock gauges.

wax

26th August 2012, 18:42

I guess you have to tune with out it and then when tune is perfect then adjust it. Kinda pain having to do that but its better than not having it

husaberg

26th August 2012, 21:45

OK moto3 is on i sitting her watching the one thing i can't understand is.
why do they sound so crap. bbbbpppppprrrrrrrrr, wtf it so monotone...........Don't they have a powerband and expansion chambers?
Also i thought they were all going to be Honda powered (in hindsight that might be the Moto2's). I feel ripped off regardless
I will have to turn the sound down i guess.

wax

26th August 2012, 21:54

Its kinda lost its appeal to me now since they went four stroke

F5 Dave

27th August 2012, 09:26

Have you heard Motocross? Its ruined the viewing experience. Bunch of bikes farting.

F5 Dave

27th August 2012, 09:30

I have just been putting on my knock gauge on the bucket and when I run her in the drive with the sensitivity set half way, reving the bucket up the gauge went off like a christmas tree and I am wondering what others have there gauges set to?
The gauge is from http://www.knockgauge.eu and the sensor is off a subaru car. It's mounted on a 100cc LC two stroke on a head stud straight onto the head with nothing inbetween if that is any help.

Its funny you say that. I have presactly the same Subi deto doofer & knockgauge. I connected it yesterday & went to the dyno. Rang up like a tree. I ended up ignoring it & feeding in smaller jets & advanced timing increased the power so I can't believe it was setup right.

My sensor is on the side of the cylinder. I wonder it it is just getting too much vibration? Not that it vibrates that bad. . . I turned the dial to try calibrate it & didn't get much change. maybe it is in a sensitive plane to operate the piezo.

Moooools

27th August 2012, 10:22

Its funny you say that. I have presactly the same Subi deto doofer & knockgauge. I connected it yesterday & went to the dyno. Rang up like a tree. I ended up ignoring it & feeding in smaller jets & advanced timing increased the power so I can't believe it was setup right.

My sensor is on the side of the cylinder. I wonder it it is just getting too much vibration? Not that it vibrates that bad. . . I turned the dial to try calibrate it & didn't get much change. maybe it is in a sensitive plane to operate the piezo.

If you can get your hands on an oscilloscope it works a treat. We just used one on the UoA dyno with a WR450. Mounted sensor on the side of the cylinder. Knock showed up as huge spikes on the oscilloscope. Well above any other noise. Then again it was on a steady state eddy current dyno. Things might go a bit quicker on one of those inertial thingys. #4StrokebutStillRelated

F5 Dave

27th August 2012, 10:33

I could even get the deto light showing revving it in neutral - & that was after finding the point of best power was somewhat advanced of where I started & progressively increased till I went too far & went back a little.

[edit] Wonder if an aircooled motor 'rings' so much that it is not useable?

2T Institute

27th August 2012, 14:24

Finning on the cylinder might be doing that, cut some old inner tubes into thin strips roll them up and jam them between the fins.

F5 Dave

27th August 2012, 15:07

Maybe I just wait till I water cool it, I can do that on the 100. - Funny I've kept some of the rubber dampers they come with std in the past, - but threw them out as I could never think why I'd put them back in. . . until. . .

husaberg

27th August 2012, 20:11

Have you heard Motocross? Its ruined the viewing experience. Bunch of bikes farting.
Yeah granted (spend a lot if time with the kids at MX) but at least there still is the 2 stroke shrill in the minis, Plus the MX bikes vary the revs a bit more plus bounce of the limiters a fair bit.....plus the two/four mix is sweet. But the Moto3 is drone city er....Motomonodrone

Maybe I just wait till I water cool it, I can do that on the 100. - Funny I've kept some of the rubber dampers they come with std in the past, - but threw them out as I could never think why I'd put them back in. . . until. . .

The Rubbers keep the noise down. The same reason Why Honda added them in the first place.
The quieter the engine the louder the exhaust can be.whist still not exceeding the noise limits (but you already knew that)

One thing i really want to know about is Friction minimisation

Wob has shared some worthwhile gains can be made with ceramic bearings and Teflon seals floating mains etc what else i assume the GP bikes had pressure feed gearboxes what else................

Yow Ling

27th August 2012, 20:23

what else................
remove seals from wheel bearings
single skinny ring
no cams
skinny rider (air friction)
tyres
plain chain

husaberg

27th August 2012, 20:43

remove seals from wheel bearings
single skinny ring
no cams
skinny rider (air friction)
tyres
plain chain

Ok slippery goop on leathers (Tight fitting leathers).
Slippery fairing even if they are ugly (only Yams):shifty:
Plain as you say skinny but HD chain with proper one piece bushes non stamped links (the old ones were handmade) new ones ?

Gee that first yam is still ugly even now.....slippery or not.

<img src="https://lh6.googleusercontent.com/-q2Z1CI4A07A/TXN8DA9qfMI/AAAAAAAAAek/tWa9z_C9ofc/05.jpg" height="180px"/>http://www.jumpingjack.nl/Images_2009_4/GP-rac187.jpghttp://www.jumpingjack.nl/Images_2009_4/GP-rac186.jpg

This below is what got me thinking re friction yes its Diesel i have seen other stuff similar re F1 and Indycar and so forth.
So Read it otherwise the puppy doesn't get parole
<img src="http://russiapedia.rt.com/files/galleries/canine-cops-life-russian-police-kennel/canine-cops-life-russian-police-kennel_5.jpg" width="190px"/>

cotswold

27th August 2012, 21:01

husaberg

27th August 2012, 21:06

Thanks TeeZee..

The blue print of my new and improved cylinder has been.... well er printed on the inside of the cylinder, it's been dialed in and scribed and I have my instructions, I just have to get hold of the appropriate tuning tools and I will be off and running.
Photo's will be added as i progress

I see beer and powertools. So its off to a perfect start.......:drinknsin
<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=268922&d=1346058050" width="340px"/>

Below Kevin Vs the evil Honda mounted Eddie.
The only Suzuki i really liked. Gee Kevin was awesome to watch then. Crash or Burn (trying)

cotswold

27th August 2012, 21:56

[QUOTE=husaberg;1130385916]I see beer and powertools. So its off to a perfect start.......:

It's Speights but

bucketracer

27th August 2012, 22:05

... it's been dialed in and scribed ...

268938

Calibrating the Verniers !!!!!!

Henk

27th August 2012, 22:44

[QUOTE=husaberg;1130385916]I see beer and powertools. So its off to a perfect start.......:

It's Speights but

Not beer at all then.

Sketchy_Racer

27th August 2012, 23:20

268938

Calibrating the Verniers !!!!!!

I saw the photo and cried a little inside... At least it's not a Micrometer.:shit::shutup:

cotswold

28th August 2012, 05:10

I saw the photo and cried a little inside... At least it's not a Micrometer.:shit::shutup:

TeeZee reckoned this would get a response :yes: but do not waste your tears as they were not my good ones but a pair of Chinese $12 specials .

TZ350

28th August 2012, 07:54

I saw the photo and cried a little inside... At least it's not a Micrometer.:shit::shutup:

268990

I know it looks a bit harsh, but sometimes you have to be cruel to be kind.

268989

Cut down verniers are an easy and accurate way of checking port heights and for getting the transfer pairs opening at the same time.

wobbly

28th August 2012, 07:54

Been away winning races so will reply now re the deto box.
Calibration is easy, turn it down real low such that the green lights do come on when doing a full throttle run.
Keep turning it up till you get a deto indication somewhere in the powerband, going up on full throttle, or as TeeZee found, when backed off on the overun.
In short - believe what you are seeing, if it shows deto on the overun, then, its got deto in the overun.
This MAY not be an issue when racing as you MAY not damage anything detoing for a short period under these conditions.
But,of course if you have a TPS this means you can use a 3D map, and its easy to pull out a couple of degrees of timing at that point, and the deto will go away - simple.
I found that maximum performance on the dyno meant you had short flickers of deto at nearly all rpm on full throttle,and it lights up when you hit the limiter.
I do several pulls at 1/4, 1/2 and 3/4 throttle,running up against the dyno load, as well as running down on the overun. to generate the TPS driven curve shape.
This enables you to dial up the max advance needed everywhere, then go into the software and back the whole curve down 1 to 2 degrees.
Now you have a good curve shape that the engine actually needs, and any issues on track, can then be taken care of by the box switching the retard input to pull out 2* to prevent unforeseen meltdowns.
I havnt used the deto setup on an aircooled, but I suspect that the deto ringing frequency signal is much bigger amplitude than a watercooled cylinder,meaning you get a much quicker indication of deto approaching.
Means its very sensitive to adjustment, but I say again, if it is flashing deto at one rpm and not at another, then believe what you are seeing, just turning it down so it does nothing, is dumb.

F5 Dave

28th August 2012, 09:31

I haven't used the ignitech yet (still commissioning the new engine with same peripherals as previous so I know where I am). I couldn't turn the knock down enough so it didn't flash up.

I'm losing a bunch of power somewhere so I can't say that the bike is running well, but I did gain 2hp leaning & advancing the settings so I can't see it in freefall deto at the start of the session despite gauge screaming it.

Have to strip engine again, I'm losing 6hp from previous, the engine is no longer leaking but I wasn't happy with the crank & it seemingly hasn't settled in. Crank got wider with looser setting & I think its pushing on the bearings. I would imagine it would be discolouring bearings to lose that much power though. Was pushing against time.

wobbly

28th August 2012, 10:25

Gigglebutton

28th August 2012, 14:48

[QUOTE=wobbly;1130386088]Been away winning races so will reply now re the deto box.

What bike was winning the races?

F5 Dave

28th August 2012, 15:01

He didn't say it was a bike, but I'll angle strongly that it was a 2 stroke.

wobbly

28th August 2012, 15:51

I built a new TM 125 KZ2 kart engine for Matt Hamilton from ChCh, I have raced with his dad for years.
Ground Aprilia type porting into the cylinder.
First run of the National Pro Series we stuck it on pole,changed everything to learn what not to do in every heat race with 2 -1sts, a 2nd and 4th.
Won the final 25 lapper going away.
Biggest opposition panicked the tuning of their million dollar trick factory engine ( not using a digital weather station - oh dear ) and siezed 1st lap of the final.
So sad I nearly wept for them - yea right.

TZ350

28th August 2012, 16:26

$80 gets you a self powered counter.
http://www.intech.co.nz/catalogue/download-pdf-individual/114-Catalogue-nz.pdf
RS will do one as well im sure.

The Trumeter 7111 is no longer stocked by RS but they do have something similar.

269009

703TR002N-512D RS part number 183-5952 $63.50 ... 5-12V and less than 10mA so easily self powered and at 500Hz fast enough to count all deto events as seen by the Knock Gauge or similar, as 200Hz in a 2-Stroke equals 12,000 rpm.

269008

And here is something if you want to try your hand at making a complete det counter for your self.

269011

RS part number 185-6090 $45.30

You could box this along with an amp or frequency filter from Jaycar and make you own little compact det counter.

269012

Electrical specs.

269014

Two different ways to go, with an amp you would count the high amplitude deto peaks or you could use a band or high pass frequency filter and count whatever passes through it.

F5 Dave

28th August 2012, 17:03

You might need bigger handle bars & an auto alternator to drive all this extra stuff:sunny:

FastFred

28th August 2012, 17:17

269018

You might need bigger handle bars & an auto alternator to drive all this extra stuff:sunny:

269017

Hub dyno and a Basket for all of those extras.

TZ350

28th August 2012, 18:58

Goodness knows what all that means but flowers are always nice.

Haufen

29th August 2012, 11:17

I am thinking about building a new exhaust pipe.

If I have to make a, say, 180 degrees turn in routing the pipe, and leaving installation spacing issues aside, would it be better to make a large and smooth turn for about 3/4 of the pipe or would it be better to have the pipe make two smaller turns, allowing for longer straight sections in the pipe?

Buckets4Me

29th August 2012, 18:22

A Slight

269082 E.S.E factory team rider

husaberg

29th August 2012, 18:28

<center>
A Slight
E.S.E factory team rider

269082

<center>Gee didn't recognise him without the mohawk.<center>
<img src="http://i45.tinypic.com/219xtgx.jpg" width="200px"/><center>

Buckets4Me

29th August 2012, 18:41

Gee didn't recognise him without the mohawk.
<center>http://i45.tinypic.com/219xtgx.jpg

it was meant to say. A slight team E.S.E rider :)

</center>

TZ350

29th August 2012, 23:01

Someone elses links list:-

http://www.rzrd500.com/phpBB2/viewtopic.php?t=2438

Might be worth a look.

F5 Dave

30th August 2012, 15:51

The piezo sensor will easily show the missfire from hitting the limiter, so it will also show a big end knock, as well as the piston hitting the head.
Dont know about excessive piston slap , but probably.
Plenty of "noise" sources in a 2T.

I'm reserving a bit of jugement re air cooled as I found my larger big end (ooh-er Vicar) was just scraping the bottom of the cases & also touching the reed stops on the up swing. Perhaps that could have been the noise that set the gauge off. Well called if so.

I was mid stripping it off the aircooled engine to throw it on the 50 till I'd WC'd the 100, but I'll give it another try & report back.

[edit] I found also where I had the gauge I couldn't turn the adjuster by hand so was being delicate with a screw driver, but there is heaps of adjustment left I hadn't used.

Yow Ling

30th August 2012, 20:56

An early 2 stroke uniflow petrol motor, kinda cool but way different to what we have today
http://modelengineeringwebsite.com/Clerk_two-stroke.html

husaberg

30th August 2012, 21:29

Someone elses links list:-

http://www.rzrd500.com/phpBB2/viewtopic.php?t=2438

Might be worth a look.

page in your links
http://domlnator.tripod.com/id11.html

TZ350

31st August 2012, 19:46

Kel sent me this ......

jan thiel on part throttle deto

"I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling."

No answer here but at least we are not alone with engines that fail on part throttle

I scraped the full coversation below from here:- http://www.pit-lane.biz/t3173p60-gp1...vermars-part-2

Brian Callahan
Jan or others, how did you control the tuned pipe wall temperature (or EGT directly?) when testing on dyno? This seemed the most difficult thing to mimic when testing either the GP engines at QUB or my R/C boat engines, in the lab. The inertial dyno or computer controlled brake seem to work best because we can match the test engine's acceleration with reality. On steady-state testing, EGT would simply climb 500, 600, 700, 750 °C until way past reality and the piston would seize.

Frits Overmars
This has always been one of Jan's greatest handicaps. He has asked for an inertial test bench over and over, but Aprilias race director Witteveen, or The Great Leader as we call him, never deemed it necessary....

Jan Thiel
When EGT goes up and up there should be some serious problem with the engine.
We never had pistons seize during our steady state tests.
Working on the dyno continuously 5 days a week!
I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling.

As Frits has written, I would have liked to have also a dynamic testing possibility, with a flywheel.
In my opinion you should simulate a straight, starting at around 10.000 rpm, and shift through the gears
until you reach top speed. And with the airbox as used on the bike, with a ventilator that simulates the raising
air speed as it would be on track! Maybe it is interesting to know that without a ventilator the engine gave
less power with the airbox fitted.

I was told that such a testing system was too expensive.
And unnecessary as we won anyway!

I can also see a disadvantage of 'dynamic' testing.
Because the duration of the test is so short you can get away with very extreme (too extreme?) settings,
without damage.

GrahamB
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Haufen
Yes I know, but part load egt is usually lower than full load egt. And I think most of us would prefer higher part load egt over part load detonation. Of course, how far one could go and how far one would need to go would have to be tested, and how much would be needed would depend on the engine.

Mic
How about much larger travel on the exhaust power valve.
With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Jan Thiel
This causes detonation (auto ignition)
The problem is that the burned gases do not exit the cilinder!
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Jan Thiel
Haufen, We also had such a test bench at Aprlia.
The prototype of this test bench was developed by Apicom in collaboration wit Aprilia.
So we had it first, and now anyone can buy it.
It was helpful but not what I wanted.
A so-called step test.
And without the airbox!

Frits Overmars
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below, but then two-stroke development at Aprilia was terminated because of Dorna's ban on two-strokes

Howard Gifford
Another way to lower HP without sacrificing piston cooling would be to richen the mixture when you want to lower the power. With a signal to a fuel enrichening solenoid you could achieve a power range. It would then be instantaneous and programmable. Not enviornmentally friendly but would work for racing. The mixture ratio difference from high power to low power would need to be just rich enough before a misfire and just lean enough for sustained high power.

The variable tailpipe idea will work but I suspect the pipe temperature would drop off and it would take several seconds to regain full power. But then again rich mixture may have the same problem.
Two strokes are like redheads. Hard to figure out and very temperamental. But when they are happy they are a lot of fun!
HG

Jan Thiel a écrit:
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.

Institute of TwoStrokes
On aftermarket ignitions I use there is a mode I can switch on where a number of indivdual sparks are cut, depending on throttle position. It is now only configured for cutting 1 in every 3 sparks on over run(tps <10% with high rpm). Would that sort of system solve the part throttle detonation? If the number of sparks cut could be varied along with TPS for this to begin and end? If it would be helpful I'm certain the manufacturer would only need a software change to do this.

Jan Thiel
I certainly thought about cutting sparks.
But remember: the problem was AUTO-ignition!

GrahamB a écrit:
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Jan Thiel
Indeed, retarding too much caused detonation!

Institute of TwoStrokes a écrit:
Jan Thiel a écrit: The entering fresh charge is ignited by the remaining, hot, burned gases! You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? On aftermarket ignitions I use there is a mode I can switch on where a number of individual sparks are cut, depending on throttle position. Would that sort of system solve the part throttle detonation?

Frits Overmars
As Jan pointed out, once you have auto-ignition, the engine does not listen to its ECU any more. So you would have to start skipping sparks well before the onset of detonation.
In a foul-stroke your proposed system does work, but a two-stroke would react far from linear. For example, if you skip 1 in 4 sparks, you will loose much more than 25% of engine power because that one missing spark will cause the gasdynamics processes to collapse. The main problem would be to realise a smooth transition from intermittent to full ignition.

Jan Thiel a écrit:
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Haufen
I think I expressed myself unclearly. What I meant was the following:
Imagine your engine with the throttle opened just above the auto-ignition range. Then you have sufficient transfer flow, but too much power. To lower the power, now retard the ignition. Then you still have sufficient transfer flow, but with less power.

I think Honda used auto-ignition to their advantage on two-strokes. As far as I remember they did it with a (very) variable exhaust power valve.

Frits Overmars a écrit:

Mic a écrit:
How about much larger travel on the exhaust power valve. With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Frits Overmars a écrit:
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below.

269228

Haufen
I think I have not gotten behind the variable tailpipe idea, yet. What would you like to vary with it and to achieve which effects? At little throttle openings the pressure inside the exhaust pipe is already very close to atmospheric pressure (if not even) on most engines. And if you had say 100mbar inside the pipe at the critical throttle opening, then the engine might have had more power with a bigger tailpipe.

269228

Frits Overmars
'Opening' the end of the reflector will cause a substantial weakening of the reflected pulse and thus less charging of the cylinder. Izze simple, no?

Haufen a écrit:
Variable transfer timing would be nice also, if feasible.

Frits Overmars
That would be my ideal. Lowering all the transfer roofs would shorten the transfer timing and lengthen the blowdown timing, so the cylinder pressure would drop further before the transfers would open. It would cure the hig revs/low power-detonation and it would improve the power band because a too early-returning exhaust pulse would have less opportunity to push the fresh cylinder contents back into the crankcase.
A controllable transfer height would even make a throttle valve unnecessary.
There's only the little problem of how to build it...

Jan Thiel
Haufen, Auto-ignition usually occurs between 10 to 40% throttle at high revs.
In fast, non full throttle corners.

Retarding the ignition was tried to diminish power.
This makes the exhaust very hot.
Then, when you need full power, it is not there because the exhaust temperatures are wrong.
This takes a little time, when the engine is back to full power you are already at the end of the straight!
The same goes for water injection in the exhaust.
It was tried by Rotax about 25 years ago.
There was a LOT more power at low revs, so the rider had to take it easy when opening the throttle.
But the engine revved a little bit less, because the exhaust temperature did not recover at high revs.
And lap times became actually slower.
After a day of testing the system was switched off.
Lap times immediately improved!

A very important thing when accelerating is the power you have after changing gear.
Spark interruption may be not so good for this!
As I did not have the dyno I wanted this gearchange effect could not be tried on the dyno, very regrettably!
Retarding the ignition and weakening the mixture by powerjet can also have a negative effect on this.
The exhaust temperature should be 'Right' for the No. of revs after you change gear.
If the temperature is too high there will be less power!
So it is REALLY complicated!

bucketracer

31st August 2012, 20:05

Better spreads of power are made everyday with far less of the gubbins this poor old whipped mule has .....?

Year Right ......

OK the thinking mans solution for detonation on over run.

269259

TeeZee it looks like you and Jan Thiel need an exhaust and/or variable transfers gubbin as discribed by Frits.

husaberg

31st August 2012, 22:23

Well Dave doesn't like it even though it is based on a Honda:shifty:
I have linked it before but not with heaps of pics nicely sized to fit.

<img src="http://hem.bredband.net/henrik_john/block14.JPG" width="565px"/><img src="http://hem.bredband.net/henrik_john/insug1.JPG" width="565px"/>
<img src="http://hem.bredband.net/henrik_john/block18.JPG" width="565px"/><img src="http://hem.bredband.net/henrik_john/reed11.JPG" width="565px"/>
<img src="http://hem.bredband.net/henrik_john/block16.JPG" width="565px"/><img src="http://hem.bredband.net/henrik_john/block13.JPG" width="565px"/>
<img src="http://hem.bredband.net/henrik_john/block12.JPG" width="565px"/><img src="http://hem.bredband.net/henrik_john/DSC00289_resize.jpg"width="565px"/>
<img src="http://hem.bredband.net/henrik_john/block15.JPG" width="565px"/><img src="http://hem.bredband.net/henrik_john/block18.JPG" width="565px"/>

Maybe Frits or Jan could fill us in as it were on the Process Aprilia or Derbi used to seal the sandcast alloy casting they used i seen "Hippling" mentioned on the Pitlane thread

More precisely: HIP Heat Isostatic Pressing. This is an operation which is to penetrate at high temperature under high pressure into a casting, an alloy of zinc intended to fill all the pores so as to densify the original alloy.

1. Casting
2. HIP Treatment
3. T6 heat treatment
4. Machining
5. Nicasil plating
(i am of course assuming of course they were sandcast)
any info on other methods would be great i have seen other sealers mentioned as being petrol resistant and able be used on crankcases
i wonder how a fuel tank sealant likre petseal would go?

Frits Overmars

31st August 2012, 22:50

Maybe Frits or Jan could fill us in as it were on the Process Aprilia or Derbi used to seal the sandcast alloy casting they used i seen "Hippling" mentioned on the Pitlane thread No need to shout Husa, I am wide awake. I don't know about hippling but in case you are also interested in hipping, take a look here: http://www.pressuretechnology.com/about-hip.php

husaberg

31st August 2012, 22:59

No need to shout Husa, I am wide awake. I don't know about hippling but in case you are also interested in hipping, take a look here: http://www.pressuretechnology.com/about-hip.php

Thanks google was not my friend in this case i tried as i hate asking questions that can be easily googled
but then again i only tried hippling.
Then went back to the pitlane thread to finish the post and check the spelling.Then seen HIP:facepalm:
the shouting was er... because you live a long way away.........
So it was still heat treated afterwards interesting was it mainly for Sealing or strength (probably both)

Had you tried any other methods or other sealing methods. Sand-casting by nature can be porous and i guess so can welding like above.
http://www.x-seal.co.uk/case_studies.html
three bond looks like it has one.
Loctite as well http://tds.loctite.com/tds5/docs/290-EN.pdf
http://www.kbs-coatings.com/RustSeal.html
http://www.cafehusky.com/threads/glyptal-1201-coating-used-for-inside-of-crank-cases.26761/

Obviously the HIP process is far superior.

bucketracer

31st August 2012, 23:34

Sand-casting by nature can be porous and i guess so can welding like above.
http://www.x-seal.co.uk/case_studies.html
three bond looks like it has one.
Loctite as well http://tds.loctite.com/tds5/docs/290-EN.pdf
http://www.kbs-coatings.com/RustSeal.html
http://www.cafehusky.com/threads/glyptal-1201-coating-used-for-inside-of-crank-cases.26761/

TeeZee has talked at work, about castings being vacuum impregnated with resin, TeeZee has a chamber and vacuum pump big enough for a crankcase half if anyone wants to try it.

Frits Overmars

31st August 2012, 23:48

Hipping is not about sealing at all. It is about improving the density and mechanical quality of the material. Impregnating will not do that.

husaberg

31st August 2012, 23:54

Hipping is not about sealing at all. It is about improving the density and mechanical quality of the material. Impregnating will not do that.

So no problems with porosity were encountered.
i see on the link you posted it mentioned sealing in the blub though.
I understand the density and mechanical quality hense why i said it hip was superior and was just going to add.
i guess the heat transfer would suffer with a sealer also, i assume, going back to your cooling.... cooling..... cooling...post ages ago

bucketracer

1st September 2012, 06:49

Hipping is not about sealing at all. It is about improving the density and mechanical quality of the material. Impregnating will not do that.

We had thought about casting our own cylinders but the integrity of the bore surface was a likely problem, it looks lik Hipping could help there.

TeeZee's vacuum impregnating was about sealing porosity's to make things air tight. Or so you didn't get virtual leaks when the object was used in a vacuum chamber. It might have application to crank cases and sealing porosity's in welds etc, like the cases Husa has been posting pictures of.

This has been topical here at work as there is some talk of converting a RG50 to rotary valve by poring molten aluminum into the left hand case and sealing it afterward by vacuum impregnating it with epoxy. The rotary valve inlet would then be machined into the new surface.

bucketracer

1st September 2012, 07:56

269260

Here Husu, looks like something you were telling me about, lots of fining and a short exhaust tract to minimize heat uptake from the exhaust tract.

Grumph

1st September 2012, 07:57

We had thought about casting our own cylinders but the integrity of the bore surface was a likley problem, it looks lik Hipping could help there.

TeeZee's vacuum impregnating was about sealing porosity's to make things air tight. Or so you didn't get virtual leaks when the object was used in a vacuum chamber. It might have application to crank cases and sealing porosity's in welds etc, like the cases Husa has been posting pictures of.

This has been topical here at work as there is some talk of converting a RG50 to rotary valve by poring molten aluminum into the left hand case and sealing it afterward by vacuum impregnating it with epoxy. The rotary valve inlet would then be machined into the new surface.

Casting integrity is best achieved with pressure die casting. The "other" Ned Kelly in Timaru has been low pressure die casting pistons for years so it is possible in the home workshop. Hot isostatic pressing is not avilable in the Southern Hemisphere to my knowledge - but there was for years an outfit in Aussie doing high pressure resin sealing of castings...
An option for your case filling is metalspraying - whichever way you do it, it WILL distort so be prepared for that.

bucketracer

1st September 2012, 08:01

An option for your case filling is metalspraying - whichever way you do it, it WILL distort so be prepared for that.

Hadn't thought of metal spraying, thanks. For the molten pour we had planned on filling the inside of the case half with casting sand and screwing the case to a metal plate using the original case fastening holes.

wobbly

1st September 2012, 10:40

The hipping process works amazingly well.
We had the rapid prototype cast cylinders for the BSL500 hipped, and the CNC machining became super bright and smooth when it was done on the treated material.

TZ350

1st September 2012, 19:25

Suzuki never designed the GP125 for these types of performance figures; TZ (and the entire team ESE) has done some amazing work in a public space proving that it is possible to do to the poor old thing. SS90 has posed a couple of valid questions here (useful mainly for people thinking of following the ESE lead in building a GP125 racer). 30 Hp is achievable (following the great resources on this thread) but it may actually be pushing past the mechanical boundaries of the actual engine design; would 27-28 be the same?? and is it's overall performance ultimately limited by the 5 speed box??

Its early days for the 30+hp engine so I would definitely go for the more proven 26-28 hp engine and wait and see how the 30+hp one finishes up. The difference between them is only 72% vis 75% exhaust width and 80 vis 78.5 deg ATDC exhaust opening and head cc'd to match, everything else is pretty much the same.

Bucket posted links on page 500 to detailed posts on how ESE built the 26+ and 30+hp engines.

269310
SS90’s

I have seen other similar shaped and very impressive graphs posted by SS90 with more hp but as far as I can make out from his posts, this one is his own work and from an engine similar to mine, 125cc air-cooled, 24mm carb and rotary valve.

SS90’s graph has a 2.5K power spread, the others at most, maybe 3K. Well if 2.5-3K is enough for SS90’s 4 speed Vespa with the big gap between third and forth, then my 4K power spread is plenty for the Suzuki’s closer ratio 5 speed. I dont think the 5 speed box is a limiting factor.

I think with its high torque and more width maybe 5-6K rpm to minimize gear changes the Vespa curve could be a winner. And I have already posted my ideas on how the Vespa approach can be extended into something really useful with a Trombone pipe. When we have got the ignition and mechanicals sorted we intend going there with the 30+ hp engine.

269311
ESE 72% 80 ATDC 28hp

At 72% exhaust port width and ex opening 80 deg ATDC giving 26-28 hp the motor proved reliable and is probably a good place to aim for, its what the other ESE bikes are running but it doesn’t interest me, I want to explore a bit further than that.

269312
TeeZees 75% 78.5 ATDC 30hp

31+ hp required a 75% exhaust port opening 78.5 deg ATDC, I ran into trouble here as the shape of the port is more critical at 75% and I had recycled an old damaged cylinder and got the shape wrong around the bottom of the port.

269553

I think 75% is livable with careful shaping of the top and bottom of the port but 72% is definitely easier to do.

We had problems at Taupo and Kaitoki that we put down to inexperience developing the ignition curve on the dyno. And suffered engine killing detonation on lower throttle openings that we later put down to, a to advanced ignition with the throttle partially closed.

At the time, we didn't know you had to retard the ignition on partial throttle.

But now it seems it’s not just an ignition timing thing but an auto ignition problem too from residual hot gases left in the cylinder.

The following post covers some of the issues. This adventure just gets better and better.

TZ350

1st September 2012, 19:26

Jan Thiel. At part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.

A disadvantage of 'dynamic' testing. Because the duration of the test is so short you can get away with very extreme (too extreme?) settings, without damage.

(On closing the power valve)

This causes detonation (auto ignition) The problem is that the burned gases do not exit the cylinder! Retarding ignition also does not make sense. As you have an AUTO-ignition problem! So the engine does not 'listen' to its ECU any more!

I thought about cutting sparks. But remember: the problem is AUTO-ignition!

GrahamB retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Jan Thiel Indeed, retarding too much caused detonation!

I was thinking about a way to reduce engine power without closing the throttle. But how can you do this?

Retarding the ignition was tried to diminish power.
This makes the exhaust very hot. Then, when you need full power, it is not there because the exhaust temperatures are wrong.

This takes a little time, when the engine is back to full power you are already at the end of the straight!

The same goes for water injection in the exhaust. There was a LOT more power at low revs, so the rider had to take it easy when opening the throttle
.
But the engine revved a little bit less, because the exhaust temperature did not recover at high revs. And lap times became actually slower. After a day of testing the system was switched off. Lap times immediately improved!

A very important thing when accelerating is the power you have after changing gear.
Spark interruption may be not so good for this! As I did not have the dyno I wanted this gearchange effect could not be tried on the dyno, very regrettably!

Retarding the ignition and weakening the mixture by powerjet can also have a negative effect on this.
The exhaust temperature should be 'Right' for the No. of revs after you change gear. If the temperature is too high there will be less power!

Frits Overmars
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm. At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.

TZ350

1st September 2012, 21:53

Previously Frits has suggested a way of working with this, I will look the post up.

husaberg

1st September 2012, 22:00

timg

1st September 2012, 22:06

Wob has previously detailed some ways of modding conventional carbs to work in a downdraft situation. Link please? Ta

Kickaha

1st September 2012, 22:08

. A virtual Chocky fish to anyone under 30 years old who knows what the filthy Diesel is.

Fuck off, I want a real one

Dirty old Cosworth

husaberg

1st September 2012, 22:09

Link please? Ta

Have a look at the picture click on it twice.
Its the Quantel Norton IE the Cosworth Challange or a couple of cylinders loped of a Cosworth V8 DF something
John Surtees converted the Carbs (ex F1 car and Motorbike 500cc world champion) I guess if he is still alive he would be not so young so should be easy to find at Home.
http://www.johnsurtees.com/4394/pages/contact.aspx

Oh if you meen Wobs fix i will look,its before PG450 where he last aluded to it i have it on file i think i a Word document.
Maybe search wobbly posts
but it might be easier to ask MR Wobbly

Hindsight i think the fix was for the PJ on MX carbs and the other fix was for reverse facing carbs on the BSL but i am sure Wob will have a fix?

Fuck off, I want a real one

Dirty old Cosworth

Copy of your Birth certificate please.

Grumph

2nd September 2012, 05:41

Wob has previously detailed some ways of modding conventional carbs to work in a downdraft situation.

The carb is a Amal MK2 concentric. the remote Float appears to be a Amal matchbox of an old Amal GP, cunning.

I seen this way today. A virtual Chocky fish to anyone under 30 years old who knows what the filthy Diesel is.

That was made to work by an Aussie by the name of Gary Flood....Surtees involvement was to offer advice and give them a couple of ex Ferrari radiators...

The first Britten used Mk2 Amals - one converted to downdraft with a right angle float chamber made up and attatched to the body - done by Alan Wylie I think. Awkward and not particularly satisfactory. Kampen in Holland is doing the same on Dellorto pumpers for Aermacchis. Most Dellortos will go to 42 deg downdraft no probs.

If you need a downdraft carb use one made for it - way less trouble.

husaberg

2nd September 2012, 08:43

That was made to work by an Aussie by the name of Gary Flood....Surtees involvement was to offer advice and give them a couple of ex Ferrari radiators...
Correct on the Flood surtees in the bit i have read was the technical advice including carburation set up and chassis set up but why Ferrari Rads thats odd......

The first Britten used Mk2 Amals - one converted to downdraft with a right angle float chamber made up and attatched to the body - done by Alan Wylie I think. Awkward and not particularly satisfactory.
Do uou mean the Britucati or the more likely the Denco version i guess the FCR hadn't been invented then or at least hasn't on sale to the public.

If you need a downdraft carb use one made for it - way less trouble.
Yes in a ideal word way less trouble, but sometimes impossible to find.
Price up a FCR30-32-34mm on downdraft set up for a 2 stroke.
Most of the second hand ones (hens teeth btw)come in groups of fours.

So if there is a way of making the common PWK or TMX or what-ever work, It may well be worth the effort.
Nearly all the downdraft carbs available are old and made for road bikes have different more complicated metering circuits than, the race carbs and do not have the spares available (try getting a different slide cutaway for a n RGV carb for instance)
So i think it is easier to convert say an Oko to downdraft than try too get an NSR or RGV carb to work as well

Kampen in Holland is doing the same on Dellorto pumpers for Aermacchis. Most Dellortos will go to 42 deg downdraft no probs.

Yeah but, they look so wrong without the SS35 Dellotto.........

Grumph

2nd September 2012, 10:43

Correct on the Flood surtees in the bit i have read was the technical advice including carburation set up and chassis set up but why Ferrari Rads thats odd......

Yeah but, they look so wrong without the SS35 Dellotto.........

Ex F1 oil coolers he donated which were the right size for water rads....just had them lying round....like when he wanted to build a racing Black lighning Vin, he just happened to have the bits in storage....

Don't get me started on bloody SS1's....

For downdraft carbs set up for 2 strokes, look at jetskis first. Hidden in varous catalogues too are downdrafts from Mikuni and Keihin.
They do make them, it's just a hard job finding them....

dinamik2t

2nd September 2012, 11:50

downdrafts from Mikuni

http://www.mikuni-topham.de/ENGLISHSITE/TMRTDMR_English/TDMRTMR_English.html

I guess they can be searched for under the name Mikuni TMR. :)

husaberg

2nd September 2012, 12:50

http://www.mikuni-topham.de/ENGLISHSITE/TMRTDMR_English/TDMRTMR_English.html

I guess they can be searched for under the name Mikuni TMR. :)

I was sceptical as i had only seen them in 39 and 41mm
but here is a 28mm one i shudder to think of the price though:sweatdrop
NSF100 YOSHIMURA MIKUNI TMR-MJN28 CARBURETOR
http://shop.yoshimura-jp.com/files/img1/778-489-8000.jpg
One of following Yoshimura head kit.
・Yoshimura head 125cc kit
・Yoshimura head 115cc kit
Manifold kit for NSF100
Racing throttle holder set for TMR small body (NSF100/L:700mm). Layout of the throttle cable is different from STD cable.
One of following heat guard.
・Carbon carburetor heat guard sheet set
・Carbon heat guard material set
Bore Size (mm) φ28
Body Interval Single Body
SpigotDiameter(mm) 31mm
SpigotLength(mm) 24mm

GSX400 IMPULSE/GSX400S
YOSHIMURA MIKUNI TMR-MJN32 CARBURETOR (FUNNEL TYPE)
Bore Size (mm) φ32
Body Interval 77-85-77
SpigotDiameter(mm) 38mm
SpigotLength(mm) 28mm
REQUIRED PARTS

NSF100 YOSHIMURA MIKUNI TMR-MJN32 CARBURETOR (SILVER BODY)
http://shop.yoshimura-jp.com/files/img1/768-489-7000.jpg
YOSHIMURA HEAD 125cc KIT
Φ32 Insulator set/NSF100
Aluminium manifold (for NSF100)
Manifold gasket
Cap bolt M6×20SUS (2pieces)
Racing throttle holder set for TMR small body (NSF100/L:700mm). Layout of the throttle cable is different from STD cable. One of following heat guard.
・Carbon carburetor heat guard sheet set
・Carbon heat guard material set

Carburetor for the engine with Yoshimura Head 125cc Kit.
・Port machining required.
・POWER FILTER TYPE is not applicable. Bore Size (mm) φ32
Body Interval Single Body
SpigotDiameter(mm) 35mm
SpigotLength(mm) 29mm

http://shop.yoshimura-jp.com/en/product/result.php?word=tmr&w_key=1&page=3

TZ350

2nd September 2012, 13:02

Husa, in the picture of that carb there is two bellmouths, a smaller one inside the main one, how does that work? what are the benifits? does anyone know anything about them.

husaberg

2nd September 2012, 13:08

Husa, in the picture of that carb there is two bellmouths, a smaller one inside the main one, how does that work? what are the benifits? does anyone know anything about them.

This one?
http://shop.yoshimura-jp.com/files/img1/768-489-7000.jpg
Its just an adapter isn't it? if not i have no idea.
There seems to be a lack of air entry for the pilot etc (might be over the other side)i can remember some other bell mouths that look like these old Keihins CVs? edit concentric Amal
http://www.feked.com/images/product/thumbnail_fkbell422-2-600.jpg

richban

2nd September 2012, 13:10

Husa, in the picture of that carb there is two bellmouths, a smaller one inside the main one, how does that work? what are the benifits? does anyone know anything about them.

Its a similar system to the wing splitter that you see for FCR's. Its all about trying to improve airspeed on large carbs. Small bell helps at say quarter throttle then on wide open it can come through from all angles. I looked at that when I switched to a 32 on the FXR. Turns out the 32 was fine down low.

husaberg

2nd September 2012, 13:17

Its a similar system to the wing splitter that you see for FCR's. Its all about trying to improve airspeed on large carbs. Small bell helps at say quarter throttle then on wide open it can come through from all angles. I looked at that when I switched to a 32 on the FXR. Turns out the 32 was fine down low.

Where are you guys looking?

oh are you sure its not just a shadow, so the bellmouth is suspending in mid air ohh i am a thicko.......

DUAL STACK AIR FUNNEL SYSTEM SET its an optional part.

http://shop.yoshimura-jp.com/files/img2/765-T2-R0601.jpg
http://shop.yoshimura-jp.com/en/product/syousai.php?id=1385

richban

2nd September 2012, 13:19

Where are you guys looking?

Back of the carb has 2 bellmouths.

Another version.

269325

dinamik2t

2nd September 2012, 14:00

Here's an exploded view :

269328

The double bellmouth must be a Yoshi add-on.

TZ350

2nd September 2012, 14:09

Thanks, the wings are easy to understand, I just couldn't see how the double bellmouths were meant to work.

husaberg

2nd September 2012, 14:24

Thanks, the wings are easy to understand, I just couldn't see how the double bellmouths were meant to work.

I couldn't even see the Double bell mouth...

Here's an exploded view :

269328

The double bellmouth must be a Yoshi add-on.
<img src="http://shop.yoshimura-jp.com/files/img2/765-T2-R0601.jpg" width="340px"/>
http://shop.yoshimura-jp.com/en/product/syousai.php?id=1385

dinamik2t

2nd September 2012, 15:10

I haven't neglected your post Husa, I was pointing out that it was an aftermarket part; not a mikuni part. :drinknsin That became obvious though in the following posts..

husaberg

2nd September 2012, 22:50

I haven't neglected your post Husa, I was pointing out that it was an aftermarket part; not a mikuni part. :drinknsin That became obvious though in the following posts..

No worries just added it in case it was missed

Ok here is a Amal concentric MK1 modified to push pull with large (read huge) float bowl of a Valiant (Chrysler car)which i guess makes it a Strongberg?
its on a stinkin diesel tractor on alky

speedpro

3rd September 2012, 07:42

This problem reminds me of an issue I had with my TS/RGV motor years ago. On the dyno at certain times you could see flames dancing round inside the carburetor. This was a full crankcase reed conversion. After a long time, over a year, in an attempt to fix the problem I just advanced the timing as far as it would go. The flames disappeared and it starting making modest power.

It seems from what people have been saying that this problem of detonation is evident on all(?) high performance 2-strokes. There may be a small number of cures but for whatever reason they have never been implemented. Thinking about it this could be what stopped my bike at Taupo. The piston was certainly hammered with cracks all over and Dave did say he was cruising in the corners which probably created the conditions needed for the problem to manifest.

The simplest answer seems to be to ride hard, maybe even changing down shift patterns - letting the revs drop as you brake and then dropping the gears as needed from lower revs.

TZ350

3rd September 2012, 08:48

Fooman

3rd September 2012, 12:15

Casting integrity is best achieved with pressure die casting. The "other" Ned Kelly in Timaru has been low pressure die casting pistons for years so it is possible in the home workshop. Hot isostatic pressing is not avilable in the Southern Hemisphere to my knowledge - but there was for years an outfit in Aussie doing high pressure resin sealing of castings...
An option for your case filling is metalspraying - whichever way you do it, it WILL distort so be prepared for that.

Best sort of casting process for mechanical integrity - in terms of strength, near-net shape, and little or no porosity, is squeeze casting. Best way to describe it is "liquid forging". The combination of high pressure, low feed rates, and high heat transfer during solidification from the mold result in porosity free and fined grained/dendritic microstructure - best for (low temperature) mechanical properties. The most common application for squeeze casting, that I can remember, is mag (aluminium) wheels. Toyota first started using it in 1978 on their alloy rims, mainly to prevent leakage of the air through the rims. Also used for casting pistons. I wrote something (http://ir.canterbury.ac.nz/handle/10092/1086) about squeeze casting a wee while ago if you want to read bit more about it.

High pressure die casting is good for surface finish, but does entrap a lot of gas during the casting process - the high velocity of the feeding results in "spraying" of the metal into the mold. So behind a nice finish, the casting can be a bit swiss cheesy.

Low pressure die casting is more sedate, meaning less issues with porosity than HP die casting, but has lower heat transfer rates that squeeze casting, giving a smaller supercooling effect, resulting in lower hetrogenous nucleation, and ultimatly coarser grains/dendrites than squeeze casting - lower mechanical properties.

The "Cosworth Process" is another good process for casting, used to cast engine blocks in sand. Mold is filled from the bottom, under very low pressure and velocity, to make sure defects like porosity, entrapment, lapping and segregation are minimised. But does not match the heat transfer of permanent mold casting techniques, hence lower mechanical properties. Was patented by Cosworth, but those have probably run out now.

Cheers,
FM

Grumph

3rd September 2012, 13:54

Fooman

3rd September 2012, 14:10

Interesting...been a while since I talked to Ned about his setup but I seem to recall it involved two people, one of whom swung on a lever attached to some kind of old stirrup pump arrangement which directly pressurised the melt...but only to the extent of the pressure the person swinging on it could exert.
Sounds a lot like a squeeze process.

Could be. LP die casting generally used gas pressure on the melt to slowly feed the molten metal into the die. Once sufficient material has solidified, that gas pressure is generally not enough to continue feeding into shrinkage regions or maintain pressure in the solidifying casting.

HP die casting uses a ram to rapidly force the melt into the die, through a nozzle.

The squeeze casting die I adpated for my research was originally built for use under a hydraulic shop press. With squeze casting, you really need quite high pressures - on the order of 50 to 150 MPa to get the best results. Fat bloke on end of lever may not be enough, generally hydraulics are used - One configration of my casting rig was designed to have 200 tonnes of force going onto something the size of a small can of V - never actually cast anything that way however. Most of my casting was done between 50 to 100 MPa, using a 10 tonne cylinder acting on the end of a 25 mm diameter mold.

Cheers,
FM

husaberg

3rd September 2012, 17:22

Best sort of casting process for mechanical integrity - in terms of strength, near-net shape, and little or no porosity, is squeeze casting. Best way to describe it is "liquid forging". The combination of high pressure, low feed rates, and high heat transfer during solidification from the mold result in porosity free and fined grained/dendritic microstructure - best for (low temperature) mechanical properties. The most common application for squeeze casting, that I can remember, is mag (aluminium) wheels. Toyota first started using it in 1978 on their alloy rims, mainly to prevent leakage of the air through the rims. Also used for casting pistons. I wrote something (http://ir.canterbury.ac.nz/handle/10092/1086) about squeeze casting a wee while ago if you want to read bit more about it.

High pressure die casting is good for surface finish, but does entrap a lot of gas during the casting process - the high velocity of the feeding results in "spraying" of the metal into the mold. So behind a nice finish, the casting can be a bit swiss cheesy.

Low pressure die casting is more sedate, meaning less issues with porosity than HP die casting, but has lower heat transfer rates that squeeze casting, giving a smaller supercooling effect, resulting in lower hetrogenous nucleation, and ultimatly coarser grains/dendrites than squeeze casting - lower mechanical properties.

The "Cosworth Process" is another good process for casting, used to cast engine blocks in sand. Mold is filled from the bottom, under very low pressure and velocity, to make sure defects like porosity, entrapment, lapping and segregation are minimised. But does not match the heat transfer of permanent mold casting techniques, hence lower mechanical properties. Was patented by Cosworth, but those have probably run out now.

Cheers,
FM

Thanks Great stuff the Cosworth/GKN process is discussed here.
The third attachment

SwePatrick

4th September 2012, 02:01

Complete differ from what you are discussing right now.. but i have to share it with you.

'Elsinore' gearbox can only take a certain amount of torque.
If you reach above this, the gears inside will not take it ;)

https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-ash4/s720x720/418787_10151073747844475_1945299258_n.jpg

this is 4th gear, it shredded when pulling hard at ~11000rpm, about 68Mph

Now i will go an another step in evolution on engine.
More revs = less torque
2 ways to go there, either tune the engine harder, or manufacture an new primary gear to rev up the gearbox.
And newer CR80 gears are much more rigid, i will use those also.

Rgds
Patrick

Frits Overmars

4th September 2012, 02:26

'Elsinore' gearbox can only take a certain amount of torque. If you reach above this, the gears inside will not take it.Any gearbox will behave like that, Patrick.

Now i will go an another step in evolution on engine. More revs = less torque.Less torque = less power, unless you raise the revs more than you lower the torque.

2 ways to go there, either tune the engine harder, or manufacture an new primary gear to rev up the gearbox.I would prefer the third way: implement a shock absorber, preferably in the primary transmission, but it will do some good in the rear wheel hub too.
And while you're at it: your gearbox will be eternally grateful to you if you manage to fit a slipper clutch. Most gearbox breakages occur when shifting down.

dinamik2t

4th September 2012, 04:54

shock absorber, preferably in the primary transmission, but it will do some good in the rear wheel hub too.

Frits, would you have a photo of such a setup, to see how it's like? I haven't heard of it before.
:o :nya:

Frits Overmars

4th September 2012, 05:52

Sorry, I'm on tour; can't get to my archive at home. But Google must be able to come up with something....

dinamik2t

4th September 2012, 07:35

You 're giving two stroke concerts??

I 've tried it before I ask, but I couldn't get something. I quick-searched 'transmission shock absorber'. You wouldn't mean the clutch cushions, eh?
Anyway, no worries, I will find it somehow. :)

speedpro

4th September 2012, 07:37

Normally there is a form of cushdrive built into the rear hub of the clutch basket. You should be able to see the springs it it uses springs though on smaller ones I've seen they use rubber blocks.
A bike I built years ago made so much torque it was smashing the cush drive up against the stops which were the rivets holding the clutch basket to the hub etc. The springs actually coil bound and shattered spreading little bits of spring all through the engine. I've rebuilt it a few times and now have extremely strong springs in the cush drive plus a beefier backing plate and upped the rivet size. It buzzes at part throttle because there's no give at light load but I've used it a bit without getting pieces of spring stuck to the sump plug.
Whip the clutch out and have a look. Generally there will be 3 rivets holding it all together. If you grind the heads off it will all come apart and you can check it out. If your bike is making lots more torque than the clutch was designed for the cush drive could be bottoming out transferring shock loads to other transmission parts.

teriks

4th September 2012, 07:41

Something like this?
http://pro50parts.neto.com.au/buy/pw084-pw50-primary-drive-gear/PW084
Now, a PW50 is not exactly a high performance bike...

wobbly

4th September 2012, 07:44

SwePatrick

4th September 2012, 07:56

Thanks for the tips Frits.
Just a couple of words,, I´m skipping info cause i thought you´d understand better than the normal internet troll.
What i meant with more revs on engine is to keep the poweramount i have, but move it more upwards in rpm band.
that will end up in less torque, but the same amount of work is beeing done.(the work is a product of torque and movement, therefor called effect(effekt in sweden, equals to what torque and turning have produced))

My dynosheet says to me i am on a good track with power, it ended up in 21.34hp at 8600rpm(due to carb problems), but engine revs about 15k.
That should be around 23-24hp in engine on that rpm(8600). that is as i see it quite good.

And the third way you are talking about,, the engine has rubbercushions on clutch, i have just inspected them, no problems there.
And the gear shredded going upwards in rpm band, no clutch no shifting, just torque pulling hard.

Bear in mind, the gearbox is designed for about 15hp engines.
I just find it as a receit that i have succeded with something.
No hanging head here.. just laughing at the shredded gears.
Quite comfortable problem i might say ;)

SwePatrick

4th September 2012, 07:59

Frits does mean rubber shock absorbers in the back of the outer clutch basket, most engines have this.
Another pointer is to get the stock gears cryo treated, the hardening process for production gearbox parts is shortened to the least possible.
This means there is a heap of incompletely converted martensite within the structure - the cryo converts this remnant material and helps part strength immensely.

Yes, cryotreatment could give me some more marginals.
But, look at the gears again.
The cogs are just fine, no problems.
i just kind of cut the gear in 'half'

Later watercooled CR80´s have the 'dogs' on gears 'closed' at one side of the gear, this should be much harder to 'cut in half'
and the gears do fit in the gearbox with small mods.
Even early Elsinore 125, around 1975 can fit with small mods.

Rgds.

edit: what i talked about with 'closed' dogs.
http://www.cyclepedia.com/wp-content/uploads/2009/11/CR85_452.jpg

the MT8 gearbox i have just shredded is the dogs all the way thrugh the gear, thus making it very weak.

dinamik2t

4th September 2012, 08:37

It's what I used to know as cushions then. Here:

269441

I guess those two springs-shocks are what you guys described earlier.
And since Patrick is dealing with CR80 parts, here's its clutch basket:

269439269440

husaberg

4th September 2012, 18:21

Yes, cryotreatment could give me some more marginals.
But, look at the gears again.
The cogs are just fine, no problems.
i just kind of cut the gear in 'half'

Later watercooled CR80´s have the 'dogs' on gears 'closed' at one side of the gear, this should be much harder to 'cut in half'
and the gears do fit in the gearbox with small mods.
Even early Elsinore 125, around 1975 can fit with small mods.

Rgds.

edit: what i talked about with 'closed' dogs.

the MT8 gearbox i have just shredded is the dogs all the way thrugh the gear, thus making it very weak.

I actually have a whole brand new "old stock" 76 CR125m (360 center code) gearbox. well at least 80% of one if not more.
kicking around in the shed.
But from what i understand Speedpros put 30 hp through his mb50 gearbox plenty people have put at least mid 20's through theirs without much issue is that the first one you have blown or is it one of many? I realise the drag racing is going to be hard on the box but just asking.
the 87 gearbox defiantly has in my experience closer ratios improved plates Steel rather than alloy and non pulp friction plates than the air cooled 80's but i seem to remember you saying the aircooled ones you had were closer ratios.

I wonder if the fact the gears are 30 years old and have possibly had a rough life as well.
The other option would be go to the 5 speed, These are a bit beefier as well.

speedpro

4th September 2012, 18:57

I was a bit surprised a cog broke as well due to my own experiance. My sidecar only made 19.9hp but the gearbox got heaps. You could really clutch it hard being a sidecar without it trying to spit you off which must have upped the load on the cogs. My bucket gearbox has been faultless apart from when I ran the oil a bit low at Taupo and scorched a few gears and selector forks. It's an MB50 gearbox, similar to a CR80 I understand, and designed for very modest power levels. My old 22.5hp bucket never had a gearbox problem and the 30hp one looked fine when I had it apart recently.

SwePatrick

4th September 2012, 20:03

I forgot to mention.

My Kawasakicylinder is stated '38hp' from factory, if true? i dunno
I know they were dynoed to 27hp at 11000rpm´s as std from factory at the rearwheel.
Now it is 132cc and way tougher tuned than when it left the factory.

Little setup:
40mm carb
V-forve reeds(ported)
15-1 compression
Cylinder tuned to make peak hp at ~13k, std is about 11k
Homemade pipe, with theories from old GP racer guy Peter Sköld.(R.I.P)

I dynoed 21.34hp at 8600rpm(at rear wheel) and engine running a bit lean just before it died.
If running dyno again now when carb is sorted out, i would figure i´d dyno about 23hp at the same rpm, and add a couple of hp´s to reach 'engine power'.
The engine pulls HARD all the way up to ~14km but i figure peakpower is at ~13k.
If one is allowed to dream,, i think engine power should be in the area of 40hp+

So why i shredded the gear isn´t hard to understand ;)
My first post about the gears was mentioned to be a bit funny also.
But as i don´t smear down all my posts with smileys they can be misunderstood.

Rgds.

speedpro

4th September 2012, 21:21

I wouldn't take too much notice of the factory claims regarding horsepower. Pete Sale, a respected local tuner, and I used to have a few good laughs about the "real" numbers obtained on his dyno compared to the claimed numbers. Some of the "good" tuning stuff was bollocks as well, like FMF fatty pipes that he tested.

To quieten that sceptical little whisper I keep hearing it would be good to get your bike on a dyno and running properly and post some numbers.

dinamik2t

4th September 2012, 21:39

Actually, Patrick, no hard feelings, but 40 (you meant wheel, right?) hp from such an oversquare engine isn't a lot?
It would be around 47 crank or around 12.4 bar BMEP, which is manageable I guess; except the time-area needs vs numbers being large, especially at 13k rpm. I am no guru here, but it seems hard to accomplish.
Perhaps on a narrow-band, dragster basis?

SwePatrick

4th September 2012, 21:47

I´m talking 40+ at engine.. not wheel.
And yes, i find factorynumbers quite funny.
Therefor i say i have dynoed 21.34Hp at rear wheel at 8600rpm(running lean)
And the factory kawa wich i have taken the cylinder from has dynoed 27hp at rear wheel ad ~11000rpm.
(I don´t see it impossible on an oversquare engine, i have almost the same time/portarea as a GP racer engine.)

All the other number are 'daydreaming'.

I thought you figured that out also.

well well.
I´ll stop posting then if you can´t read my bad language skills.

Frits Overmars

4th September 2012, 21:50

Perhaps on a narrow-band, dragster basis?Narrowing the power band down from its natural 'racing two-stroke' character will not raise peak power, but lower it.

speedpro

4th September 2012, 21:58

Geez. Don't take any of this the wrong way. Me personally, I want to see what it's making and then when you take it to the track how it goes against other competitors.

SwePatrick

4th September 2012, 22:49

What track?

I think you got it all wrong.. this is a 'moped' that is run at club mettings at 1/8mile straight line.
I just wanted to build an overkill moped.

And why that 'geez'?
Do you think it´s impossible to get 40+ hp at engine with hometuned 132cc engine?
If so, you need to look further than inside your box.

Such a lame statement..

dinamik2t

4th September 2012, 22:53

I´m talking 40+ at engine.. not wheel.

Excuse my misconception then.

Narrowing the power band down from its natural 'racing two-stroke' character will not raise peak power, but lower it.

You sure know better Frits.:) I was thinking about high-er header/baffle angles and port timings. Wouldn't those add peak power at the expense of power spread?

Frits Overmars

5th September 2012, 00:46

Haufen

5th September 2012, 06:48

No.
Port timings and pipe shape of a state of the art competition two-stroke are just that: state of the art. I think I already tried to explain why steeper cones and higher port timings won't do any good. I just can't find it back (silly search option!) so you may have to do some searching yourself.

Is that where you explained that and why the ideal exhaust port timing is about 190 degrees? (http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130304016#post1130304016)

kel

5th September 2012, 08:42

What track?

And why that 'geez'?
Do you think it´s impossible to get 40+ hp at engine with hometuned 132cc engine?
If so, you need to look further than inside your box.

Such a lame statement..

SwePatrick, you seem to be taking on thoughts, advice and general ramblings as personal attacks. Im not sure why but I am sure it will limit what you can gain from this thread/forum.

wobbly

5th September 2012, 09:11

I think we are getting lost here due to misconceptions of approach.
If you take a RD250 and lift the Exhaust 3mm it will narrow the powerband and raise the peak power.
Take a RSA250 and raise the Ex by 3mm and it will make less power, alot less.

Same with trying to use steeper cones, the RSA approach pushes the limits of energy being able to be used to increase the charging and trapping efficiency.
Combined they create a very high Delivery Ratio, and I would say there were very few avenues left to explore that would increase the current value.

If your engine hasnt got SOTA anything then sure, making any changes that move toward the RSA system will be a good thing.
But thinking that simply carrying on that approach to the extremes is faulty logic.

dinamik2t

5th September 2012, 10:23

I think we are getting lost here due to misconceptions of approach.

Yeah, I realised that after going back and seeing the word 'racing' in Frits' pre-previous post. He meant that 'state-of-the-art racing' two stroke.
The thing is most of us have little to no access to materials, experiments and parts of this perfection. (I skipped the 'knowledge', thanks to you :D)

TZ350

5th September 2012, 11:56

.... this is a 'moped' that is run at club meetings at 1/8mile straight line. I just wanted to build an overkill moped 40+ hp at engine with hometuned 132cc.

132cc 40 crank hp 1/8 mile racing moped ..... it should be possible, anyway I like the idea.

jasonu

5th September 2012, 12:43

dmcca

5th September 2012, 23:44

OK, firstly please forgive me if this has been spoken about here before... I have searched and havent found any references to it... nor do i recall reading about it here, but maybe i have missed it.

Several years ago i was rebuilding a friends 2007 RM250 MXer which was previously used by an Australian offroad champion. The engine was incredibly strong, possibly the fastest 250 I have ever ridden. It had great bottom end and revved to the moon without any hesitation. When I opened it up the engine was essentially stock other than a crude angle cut along the exhaust port roof at the bore edge... the angle was close to 50 or 60* and was slightly radiused into the port. I forget the stock exhaust opening but the angle was probably 3-4mm high and raised the duration to the mid 190's (196* rings a bell but dont quote me on the figures as i wasnt in the habit of keeping good notes back then). Overall it was done in a very rough manner but it seemed to work incredibly well and i spent a long time thinking about the effect it would have until i eventually forgot about it before really coming up with any answers.

I was recently re-reading the entire pit-lane thread on the RSA125 an noticed a brief mention by Jan Thiel of the radius that the Aprilia cylidner has at the exhaust port roof to improve flow... there are also two differnt durations mentioned for the RSA exhaust, one is 202* the other states "196* without taking the radius into account", or something to that effect... I instantly remembered the crude RM250 mod and have been thinking about it ever since. To be honest i can't fully explain the effect of the radius... I think increased blowdown and increased flow out of the port but how would the leaving and returning exhaust wave act??... Hmm, still thinking about exactly how the radius would act.

Going by the RM i rode it seemed to keep the stock bottom end and add significantly to top end and over rev...

The other day i tried to sim it using Engmod. I started with a stock 2012 KTM300 file and raised the exhaust port only by 1mm, 2mm and 3mm... the graph shows the stock and +2mm power curves and if you combined the best of both lines this is pretty much what i felt on the RM... the +1mm and +3mm graphs are intuitively obvious...

269529

I have also seen some patents relating to this idea but no explanation as the the exact effects it has.

Has anyone tried a back to back comparison between a 'standard' port and a radiused port to explain the real world effects it has?

Once again if this has been spoken about before then just ignore this and ill retreat back into my cave...

SwePatrick

6th September 2012, 02:38

SwePatrick, you seem to be taking on thoughts, advice and general ramblings as personal attacks. Im not sure why but I am sure it will limit what you can gain from this thread/forum.

I don´t think i do.
What upsets me is that people are reading my posts as the devil reads the bible.
And that expression 'geez' is to me an expression we use in Sweden when people are really really dumb.
I do not judgement people until they have proven themself dumb.
But in certain cases i might reconsider my rules from here on.

I´ll tell you a little bit of my 'history' and where i´m coming from to clearify that i´m no rookie:
I´m born 1970
started to tune my first moped, a Puch 'florida' at 12years of age.
I got that to run at the impressive speed of 40Mph, not bad for a guy that wasn´t even a teenager.(and only tuned 1hp products)
At 13years of age i ported and flowed my first FORD V4 heads.
Those became running so good that they were used in an Rallycar(SAAB 96)
Then it became a Zündapp, at 15 years of age, tuned that one to the point where the std conrod couldn´t take it anymore.
It revved REALLY hard with my bored out BING22mm carb, (bored out to 24mm)
this was 1985.(with homemade pipe)

Several engines has passed my fingers since then.
Snowmobiles,Rallycars,Offroads, all with good results.

In latest 10years i have been concentrated to port and flow different dragracing cars heads.
Often Audi 5cyl 2.2litre.
Which i have tuned to about 1100hp in engine.(Exactly 1132hp)
And often with MUCH broader powercurve than others.
I had myself an Opel(vauxhall) Kadett GTE wich i had converted to 4wd with an specially built turboengine from my theories.
This was quite cool,, i settled for about '700hp' as maximum and then finetuned everything to work as good as possible.
This ended up in the most hard running 2.3 litre(4cyl) engine i ever driven.
full boost already at 3000rpm, and had it all the way up to 8000rpm.
Boost was almost instant, no lag, at any rpm between 3k and 8k.

Latest acheivment is an Audi 80 quattro 1984 wich had a topspeed of 214.2Mph on standing kilometer,(1000m)

But somehow i got tired of all this hogging out 4 stroke heads, so i picked up 2stroke tuning again.
Now with skills i wish i had when i was 15 years old.

Through all this years of tuning, i have never used a flowbench. i often have to 'fight' with internet trolls that people CAN be born with talent, but i´m always loosing the keyboardwar *lol*.

With that said, i just wanted to say i got about 30years of experiance in enginetuning in my spine.

Rgds
Patrick

Grumph

6th September 2012, 06:58

Relax Patrick, you're not under attack....The Kiwi sense of humour and some of our colloquial expressions are often hard to interpret...

Frits seems to have it covered though - I hear he may have family here in NZ which would help.

With your background in performance cars you'd fit in well here in NZ, it's a large part of our culture.
Just be thankful it's not an Australian site...

Carry on the good work.

SwePatrick

6th September 2012, 07:23

I´m calm.

But i know of experiance that many people reacts strange when a 'newbie' on different forums is waving the big hammer.
I just wrote the last post to clearify that i am not dumb ;)
And this thread with Frits many many tips and pictures have made me more certain of my work as i can see a lot of similar thoughts and similar ways to design different things on a twostroker as my own ways.

Rgds
Patrick

FastFred

6th September 2012, 07:40

I was recently re-reading the entire pit-lane thread on the RSA125 an noticed a brief mention by Jan Thiel of the radius that the Aprilia cylidner has at the exhaust port roof to improve flow...

Could you please tell us more about this radius, maybe draw a picture so I can understand it. Thanks.

wobbly

6th September 2012, 07:56

I have just completed a back to back test on the Ex port radius in a TM 125 kart engine.
The cylinder from the factory was a special "tuned "expensive part number, and I was given a stock one to modify.
For sure the two were very different, the stock one being alot lower timing.
This was fortuitous,in that it enabled alot of room to be used to move ports.

First test was the stock cylinder with the main EX at 194, I put a big radius on the roof giving effective timing at 196.5 ( the trick cylinder was the same at 196.5 )
This instantly picked up power everywhere from 8000 to 14000, with alot better overev power, being 6Hp up at 14000
The next test involved dropping the cylinder,removing the chrome and regrinding the ports to the reverse stagger layout.
The A port being the lowest, to allow alot bigger Aux ports.
The main Ex port now opened around 192,with effective at 195 but the Aux opened at the same time, giving better blowdown area, as well as the flow enhancing radius on all 3 ports.

With the reverse stagger giving better transfer area ( as the B,C ports being high with alot of width compared to the previously high A port ) the engine now made 2 Hp or more than the factory trick cylinder
but was now 8 Hp up at 14000 and gained 400 rpm of usable overev, as previously it dropped dead at 13800 on track.
This setup proved to be quite insensitive to jetting and timing changes, allowing alot more static advance giving much better off corner power without killing revs as this would normally do.
Thus the enhanced blowdown flow of the radius at low port openings,allowed those much lower timings to be used effectively, enhancing power everywhere, but most importantly in the overev,where blowdown is most needed.

Frits is right when he says that the Italian factories are 3 years behind,as they still havnt started to use much of the technology developed at Aprilia even now.

dmcca

6th September 2012, 11:03

Thank wobbly, very interesting info... Seems my bum dyno wasnt telling lies on the RM. I'd love to do a series of tests of radius vs different port heights to determine a loose relationship between radius and 'equivalent' duration (based on normal right angled ports)... I guess it gives the BD of a high port but does the exhaust system more or less act like a lower port setup giving improved spread?? Maybe with the right port durations (similar to the aprilias) it allows the superposition effects of a ~19X* port (and exhaust) with the blowdown advantage of a ~20X* port for extra overrev. I'll keep thinking... and testing!

Out of interest when you dropped the cylinder in the second test did the port floors end up below the piston at bdc? And if do did you bother correcting this with epoxy to avoid flow separation and improve cooling?

wobbly

6th September 2012, 12:04

Stock the port floors were slightly above the timing edge, when I dropped the cylinder they ended up 0.2mm below,not a concern I would have thought.

Edit - also the rules dont allow " adding material " for KZ2 .

FastFred

6th September 2012, 12:42

It might be a 12A Rotary exhaust port but there is some interesting ideas about testing and port radiusing applicable to 2-strokes. http://www.yawpower.com/Flow%20Testing.html

Ages ago Bucketracer posted about port radius's, at the time I don't think anyone recognized its value or knew what size the radius could or should be or paid much attention except SS90 who seems to delight in any opportunity to derided Bucket for his internet based research.

Me, well I would like to know more about the dimensions of suitable radius's.

kel

6th September 2012, 12:43

Jan Thiel of the radius that the Aprilia cylidner has at the exhaust port roof to improve flow... there are also two differnt durations mentioned for the RSA exhaust, one is 202* the other states "196* without taking the radius into account", or something to that effect...

Interesting stuff. Perhaps Frits might expand on this.
When I read the pitlane thread sometime back I assumed the radius referred to was the radius top edge of the exhaust port as is done on most all exhaust ports to aid ring life, thus the auxilliaries were 196* in line with the lower edge of the top of the exhaust port (as if it was square edge at the top) while the highest section of port due to the top edge radius was 202*. But dmcca has read this as a radius cut horizontally into the exhaust duct itself, which from Wobblys post most definitely has a positive effect on power. Jennings raised this in his 2 stroke tuners handbook way back when - 1973 to be precise

"As regards the exhaust port, a secondary function is served by providing a bevel,
and radiused edges, around the port window. There is a very considerably contraction of
flow through any sharp-edged orifice, and such orifices may be made effectively larger
by providing them with a rounded entry. Improvements in flow in the order of 30-
percent could be had were it possible to give the port window edges a radius of, say, ¼
inch. Unfortunately, to do this would mean advancing the point of exhaust-opening a like
amount, which in most engines would result in a very radical exhaust timing indeed. It
is, on the other hand, often possible to carve just such a radius at the sides of an exhaust
port - although it is questionable that this radius would be as effective as simply widening
the port to the same extent. The radius approach does have the advantage of leaving
intact much of the metal around the port, which can be important: Thick sections of metal
tend to equalize cylinder temperatures and prevent the kind of local distortion that is such
a potent cause of piston seizure."

F5 Dave

6th September 2012, 13:10

I'd assumed the 196/202 thing was the Power valve only moved a small amount, but did it fast enough & only started from (ermm?) 10,000 or something like that.

dinamik2t

6th September 2012, 14:32

If I remember Jan's info correctly, AUX ex ports were 2mm below the main. Main was 196 plus that big radius, extending it to 202.
If the -2mm from the main are with the 202 duration, then AUX timing is around 83 or 194 duration. If it was with the 196, the they are 86/188.

The PV was 90/180 at 10000, fully open to 79/202 at 12000.

With a 54.5 stroke, each timing degree is about 0.5mm, so the radius from 82/196 to 79/202 is 1.5mm vertically.
<strike>From EngMod's CADing, the exhaust top edge radius could be around 60-70mm to be like that.
</strike>
edit: removal of misleading pic:sweatdrop

269549

dmcca

6th September 2012, 14:38

Interesting stuff. Perhaps Frits might expand on this.
When I read the pitlane thread sometime back I assumed the radius referred to was the radius top edge of the exhaust port as is done on most all exhaust ports to aid ring life, thus the auxilliaries were 196* in line with the lower edge of the top of the exhaust port (as if it was square edge at the top) while the highest section of port due to the top edge radius was 202*. But dmcca has read this as a radius cut horizontally into the exhaust duct itself, which from Wobblys post most definitely has a positive effect on power. Jennings raised this in his 2 stroke tuners handbook way back when - 1973 to be precise
"

I'd assumed the 196/202 thing was the Power valve only moved a small amount, but did it fast enough & only started from (ermm?) 10,000 or something like that.

Hmm... Maybe I have mistakenly interpteted it in a different way to others... I know I was constantly trying to find an explanation for the RM250 experience of a few years ago and so when I read a couple of key quotes at pit lane (from people who should know!) I didn't question my initial interpretation of what they were saying. Rightly or wrongly it seemed to add up to me.

I will try to find the quotes and post them up here just to see how others would interpret them...

dmcca

6th September 2012, 15:14

Here we go...

Jan Thiel, p44 Pit Lane RSA125 thread...

"The exhaust port had a radius at the top, but this was more for the flow and not to avoid ring clipping.
We never had problems with the piston rings, the central exhaust port was not so wide."

When i read this i though that a normal curved port roof doesnt really do much extra for flow, its more about controlling the exhaust pulses and saving rings, so to me it made sense that he could be talking about a horzintal radius which would definitely have a big impact on flow.

Frits Overmars, p47 Pit Lane RSA125thread...

"Exhaust 202°, A-transfers 130°, B- and C-transfers 132°."

fpayart, p7 Pit Lane RSA125 thread Part 2...

Q: Will you tell us the final width and height of the RSA exhaust exit? (after some conversation regarding port widths)

A: The sizes are 39.5 width x 27.5 height (without the radius).
Now I can imagine your next request
The opening time is 196 ° measured without taking into account the radius.

To me this last bit sealed the deal... why would he give a height or a duration to the lower point on a normal curved roof radius (ie. the height to some point near the far side of the port roof)... he wouldnt, it doesnt make sense... i think think this adds further weight to the fact that its a horizontal radius blending inwards into the exhaust duct. This would explain the difference in durations listed by people who definitely know this engine. I guess the way the port acts is somewhere between the two durations, most likely determined by the exact dimensions or construction of the radius...

Also there is this...
Havent really read the detail but the pics reflect what i found on the RM250...
http://www.google.com/patents?id=ikswAAAAEBAJ&pg=PA2&source=gbs_selected_pages&cad=4#v=onepage&q&f=false

kel

6th September 2012, 16:09

Yes very interesting indeed. I have a spare cylinder that I hope to start working on as soon as my wrist has healed, the exhaust port is top of the list for what I'd do differently from last time. Hopefully Frits will expand on the use of the top horizontal radius and how best to put this into effect.

jasonu

6th September 2012, 16:42

I don´t think i do.
What upsets me is that people are reading my posts as the devil reads the bible.
And that expression 'geez' is to me an expression we use in Sweden when people are really really dumb.
I do not judgement people until they have proven themself dumb.
But in certain cases i might reconsider my rules from here on.

I´ll tell you a little bit of my 'history' and where i´m coming from to clearify that i´m no rookie:
I´m born 1970
started to tune my first moped, a Puch 'florida' at 12years of age.
I got that to run at the impressive speed of 40Mph, not bad for a guy that wasn´t even a teenager.(and only tuned 1hp products)
At 13years of age i ported and flowed my first FORD V4 heads.
Those became running so good that they were used in an Rallycar(SAAB 96)
Then it became a Zündapp, at 15 years of age, tuned that one to the point where the std conrod couldn´t take it anymore.
It revved REALLY hard with my bored out BING22mm carb, (bored out to 24mm)
this was 1985.(with homemade pipe)

Several engines has passed my fingers since then.
Snowmobiles,Rallycars,Offroads, all with good results.

In latest 10years i have been concentrated to port and flow different dragracing cars heads.
Often Audi 5cyl 2.2litre.
Which i have tuned to about 1100hp in engine.(Exactly 1132hp)
And often with MUCH broader powercurve than others.
I had myself an Opel(vauxhall) Kadett GTE wich i had converted to 4wd with an specially built turboengine from my theories.
This was quite cool,, i settled for about '700hp' as maximum and then finetuned everything to work as good as possible.
This ended up in the most hard running 2.3 litre(4cyl) engine i ever driven.
full boost already at 3000rpm, and had it all the way up to 8000rpm.
Boost was almost instant, no lag, at any rpm between 3k and 8k.

Latest acheivment is an Audi 80 quattro 1984 wich had a topspeed of 214.2Mph on standing kilometer,(1000m)

But somehow i got tired of all this hogging out 4 stroke heads, so i picked up 2stroke tuning again.
Now with skills i wish i had when i was 15 years old.

Through all this years of tuning, i have never used a flowbench. i often have to 'fight' with internet trolls that people CAN be born with talent, but i´m always loosing the keyboardwar *lol*.

With that said, i just wanted to say i got about 30years of experiance in enginetuning in my spine.

Rgds
Patrick

Pictures and or videos or it never happened. Seriously mate I am interested in seeing some of your work especially the Audi and Opel stuff you mentioned.

speedpro

6th September 2012, 22:21

With that said, i just wanted to say i got about 30years of experiance in enginetuning in my spine.

Rgds
Patrick

Geez some people are sensitive. I'll say it again - I'd like to see what power your engine is making. Not because I doubt (well maybe a little bit) what you are saying but because
I'm interested in most things that burn petrol, or methanol, or nitro and I want to know what it's doing, not because I want to put it down. There's nothing to be gained from that and no point to it.

FYI I have a 39 year old turbo bike that made 175rwhp with bent exhaust valves and I've ported alloy big block heads that when fitted to a steel bodied holden ute ran 6.9? seconds at over 200mph in the quarter.

I also consider a drag strip to be a track. It's short and straight but still a track.

Drew

6th September 2012, 23:23

I also consider a drag strip to be a track. It's short and straight but still a track.Drag racing goes somewhere. Point A, to point B. Circuit racing goes round in stupid circles!

Brian d marge

7th September 2012, 01:14

Frits Overmars

7th September 2012, 05:15

fpayart, p7 Pit Lane RSA125 thread Part 2...

Q: Will you tell us the final width and height of the RSA exhaust exit? (after some conversation regarding port widths)

A: The sizes are 39.5 width x 27.5 height (without the radius). Now I can imagine your next request. The opening time is 196 ° measured without taking into account the radius.

To me this last bit sealed the deal... why would he give a height or a duration to the lower point on a normal curved roof radius (ie. the height to some point near the far side of the port roof)... he wouldnt, it doesnt make sense..Francis Payart's answer makes perfect sense. Besides, he should know, he bought the winning Aprilia RSA125 right after the last 125 cc Grand Prix and today he produces his own, very well-made copies of those cylinders for his 250 cc tandem twin FPE superkart engine.
The port in the cylinder casting has a timing of 196°. Then the upper edge receives a radius that lifts the timing edge to 202°. It's as simple as that.

wobbly

7th September 2012, 07:53

Yea right ok guys, lets quit dick measurements, and get on with posts that help others understand 2T workings.
By the way I built a racing lawnmower when I was 12 - does that count.

kel

7th September 2012, 08:09

The port in the cylinder casting has a timing of 196°. Then the upper edge receives a radius that lifts the timing edge to 202°. It's as simple as that.
Frits, for the purpose of implementing and testing this radius is there a ratio to apply based on area, timing, etc? Is 6deg effective timing the magic number to work towards in say 2 deg steps? In the attached drawing AP125-01 does the broken line above the exhaust port represent the area the radius is applied to?
Thanks in advance for your advice
269598 269597

F5 Dave

7th September 2012, 09:31

Wow, every days a school day.

I've been making big radius ex ports purely for ring life, something a chap Ram told me over a beer in the 80s was to make the port top square & create an eyebrow top & sides so the piston sees fast opening flat but the ring sees a nice rounded port. Never to that level I don't think & it appears the assumptions were wrong, but I wasn't expecting that.

Ohh lookie, page 600.

F5 Dave

7th September 2012, 09:32

Y. . . .
By the way I built a racing lawnmower when I was 12 - does that count.
Depends, did you get paid per lawn, or by the hour?

TZ350

7th September 2012, 09:43

Page 600 ... there are other interesting link collections on most other decade pages. Or you can use Thread Tools and View Images to flick through the images and find associated posts.

On Page 500, Bucket has links to how Team ESE built their 26, 28 and 31 hp engines.

Page 500 .....
No need to have a peaky engine. Here are Two Very useful Tools. EngMod2T a 2-Stroke simulation package and a handy (and cheep) Porting Calculator from:- http://www.porting-programs.com/ which is based on Blairs work.

Gordon Jennings book Two Stroke Tuners Handbook.

http://edj.net/2stroke/jennings/
http://3cyl.com/mraxl/manuals/jennings/chambers.pdf

Back in the day, Jennings was the Bible and it is still a good read. He did a good job of unravelling the mysteries of port timing, but he did not give much emphasis to blowdown time area. This oversite of such an important aspect of 2-Stroke tuning is probably why its been overlooked by so many tuners and it probably held back home tuned strokers for years.

We know better now and the clever trick is to keep the Transfers low and wide to enable adequate blowdown without having to go to extremes with the exhaust port.

Bell was next.

http://www.2shared.com/document/2G7BEpq3/A_Graham_Bell_-_Two_Stroke_Per.html

Then there was Blairs work and he put numbers to the exhaust blow down time areas required.

http://www.dragonfly75.com/motorbike/2StrokeDesign.pdf
http://www.prme.nl/download/engine-0.pdf
http://www.4shared.net/download/8hfjpcIM7V1dtEKx5cBzEj/Design-and-simulation-of-two-stroke-engines-Gordon-P-Blair.html

STA Specific Time Area is port time area at a chosen RPM. STA underpins all 2-stroke design work.

This software is so good and so cheap you should get yourself a copy ......

Two-Stroke Porting Software.

269622

Plan your ports with this software using Jennings and Blairs principles.

Porting Calculator and Port Analyser. $16.25 USD each. Paypal accepted.

These are based on Blairs and Jennings Books, makes it easy to apply their work to your motor. The program screen can be switched between Blair or Jennings and back again as you work.

Look at them here:- http://www.porting-programs.com/

I purchased mine over the net 8 months ago using Paypal and it was available for downland within hours.

Then when I claimed my free upgrade it to was quickly available.

Do go and have a look at his site:- http://www.porting-programs.com/.

Frits talks about 190 deg Exhaust port duration being the optumim and why......

Do I understand this correctly, given sufficient blow down and exhaust STA an exhaust duration of 180 deg would be the optimum at any rpm? The short answer is yes.

When the exhaust port opens, a pressure pulse starts moving through the exhaust pipe. It is reflected at the end cone and it should be back at the cylinder just before the exhaust port closes.
Next a part of this reflected pulse bounces off the partly-closed exhaust port and a residual pulse starts moving down the exhaust pipe. This residual pulse too is reflected by the end cone and starts moving back to the cylinder. Ideally it will arrive at the exhaust port just when the port opens again. Then the cylinder pressure and the pressure of the residual pulse combine their energy and the resulting pulse will be stronger than the pulse from the previous cycle. And the combined pulse from the next cycle will be stronger still, and so on; we have achieved true resonance.

Some may argue that we want a low pressure in the exhaust pipe when the port opens because then the spent gases will experience less resistance while leaving the cylinder. But that is not true. Gas flow depends on a pressure difference ratio. But once that ratio reaches 2, the flow velocity will reach Mach 1, the speed of sound. Raising the pressure difference any further will not raise the flow velocity any further.
The cylinder pressure at exhaust opening can be as high as 7 bar and the pressure of the reflected pulse will be about 2 bar. Thus the pressure ratio is well above 2, so lowering the pressure in the exhaust duct outside the cylinder will not do any good to the flow.

What has the exhaust timing got to do with the 'true resonance' I mentioned above?
The initial pulse starts moving at Exhaust Opening and it has to be back at Exhaust Closing, or a little earlier. This pulse travels with the speed of sound and its journey up and down the exhaust pipe will take t seconds.
The residual pulse starts moving at Exhaust Closing and it has to be back at the next Exhaust Opening. This pulse also travels with the speed of sound and its journey up and down the exhaust pipe will also take t seconds.
So from EO to EC takes t seconds and from EC to EO also takes t seconds. In English: the exhaust port should be open just as long as it should be closed.
Assuming that the crankshaft rotates with a uniform speed, this means that the crank angle during which the exhaust is open must be equal to the crank angle during which the port is closed. So both angles must be 180°.

I developed this line of thought some 40 years ago, but when I first published it in 1978 (in the motorcycle magazine Moto73 of which I was the technical editor) everybody called me crazy. Some people still do, but I got used to it .

Above I made a couple of assumptions. The crankshaft does not rotate with a uniform speed, but at high revs the deviation is negligible. In case you really want to know, I did the math for the Aprilia RSA125. At a nominal rpm of 13,000 the minimum rotation speed is 12970 rpm @ 107° after TDC and the maximum value is 13031 rpm @ 356° aTDC. What's more significant: the deviation in crankshaft position from truly uniform rotation is always less than 1°. So that really is negligible.

Second assumption: both the initial pulse and the residual pulse move with the speed of sound. Not true: the pulse pressures in exhaust waves are so high that acoustics rules do not apply any more. We are dealing with gas dynamics here and the stronger a pulse, the faster it moves. Since the residual pulse is weaker than the initial pulse, they move at different speeds. But we will leave this aside for now.

Third assumption: the initial pulse starts moving as soon as the exhaust port starts opening. More or less true, but we are not interested in the first weak appearance of the pulse; we want to know when the pulse reaches its maximum amplitude. And that requires a certain amount of open exhaust port area. It turns out that for our desired theoretical exhaust timing of 180° we will need a geometrical exhaust timing of about 190°, depending on the shape of the port: does it open gradually or does it open over its full width all at once.

The obvious question will be: why has the Aprilia RSA125 a geometrical exhaust timing of about 200°? True, at 190° the maximum torque value would be higher, but the engine would not want to rev because the blowdown time.area would be too small.
The 200° are a compromise: a bit less torque and a bit more revs; as long as the torque decline is smaller than the rpm rise, we gain horsepower.

Is that where you explained that and why the ideal exhaust port timing is about 190 degrees?

Exhaust Port Radius.

I was recently re-reading the entire pit-lane thread on the RSA125 an noticed a brief mention by Jan Thiel of the radius that the Aprilia cylinder has at the exhaust port roof to improve flow... there are also two different duration’s mentioned for the RSA exhaust, one is 202* the other states "196* without taking the radius into account", or something to that effect...

Interesting stuff. Perhaps Frits might expand on this.

"As regards the exhaust port, a secondary function is served by providing a bevel,
and radiused edges, around the port window. There is a very considerably contraction of
flow through any sharp-edged orifice, and such orifices may be made effectively larger
by providing them with a rounded entry. Improvements in flow in the order of 30-
percent could be had were it possible to give the port window edges a radius of, say, ¼
inch. Unfortunately, to do this would mean advancing the point of exhaust-opening a like
amount, which in most engines would result in a very radical exhaust timing indeed. It
is, on the other hand, often possible to carve just such a radius at the sides of an exhaust
port - although it is questionable that this radius would be as effective as simply widening
the port to the same extent. The radius approach does have the advantage of leaving
intact much of the metal around the port, which can be important: Thick sections of metal
tend to equalize cylinder temperatures and prevent the kind of local distortion that is such
a potent cause of piston seizure."

The port in the cylinder casting has a timing of 196°. Then the upper edge receives a radius that lifts the timing edge to 202°. It's as simple as that.

Since I am spilling the beans here: the top radius was 3.5 mm; it was tangential to the exhaust duct roof. That raised the timing from 196° to 202° when the first glimpse of light became visible.

I have just completed a back to back test on the Ex port radius in a TM 125 kart engine.
The cylinder from the factory was a special "tuned "expensive part number, and I was given a stock one to modify.
For sure the two were very different, the stock one being alot lower timing.
This was fortuitous,in that it enabled alot of room to be used to move ports.

First test was the stock cylinder with the main EX at 194, I put a big radius on the roof giving effective timing at 196.5 ( the trick cylinder was the same at 196.5 )
This instantly picked up power everywhere from 8000 to 14000, with alot better overev power, being 6Hp up at 14000
The next test involved dropping the cylinder,removing the chrome and regrinding the ports to the reverse stagger layout.
The A port being the lowest, to allow alot bigger Aux ports.
The main Ex port now opened around 192,with effective at 195 but the Aux opened at the same time, giving better blowdown area, as well as the flow enhancing radius on all 3 ports.

With the reverse stagger giving better transfer area ( as the B,C ports being high with alot of width compared to the previously high A port ) the engine now made 2 Hp or more than the factory trick cylinder
but was now 8 Hp up at 14000 and gained 400 rpm of usable overev, as previously it dropped dead at 13800 on track.
This setup proved to be quite insensitive to jetting and timing changes, allowing alot more static advance giving much better off corner power without killing revs as this would normally do.
Thus the enhanced blowdown flow of the radius at low port openings,allowed those much lower timings to be used effectively, enhancing power everywhere, but most importantly in the overev,where blowdown is most needed.

Frits is right when he says that the Italian factories are 3 years behind,as they still havnt started to use much of the technology developed at Aprilia even now.

There is more on Exhaust Port Radius below.

269613

And Yamahas Ideas about what is important with transfers.

TZ350

7th September 2012, 09:44

Page 600 B

It seems that at high rpm and part throttle the pressure in the cylinder is higher than in the crankcase when the transfers open and hot burnt combustion gases back flow down the transfers.

Part throttle detonation is the current big issue for our 30+hp aircooled engine. Retarding the ignition on part throttle is only part of the solution.

More blowdown time area is required to lower the in cylinder pressure so opening the power valve further when closing the throttle at high rpm could be a solution.

Or the pressure inside the expansion chamber (and cylinder) could be lowered by having a second stinger pipe with a butterfly. Which is opened in high rpm part, throttle situations to drop the expansion chamber and cylinders working pressure.

And Frits proposes an idea where the intensity of the reflected wave is reduced by changing the size of the bleed venture at the end of the reflective cone.

Kel sent me this ......

jan thiel on part throttle deto

"I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling."

No answer here but at least we are not alone with engines that fail on part throttle

I scraped the full coversation below from here:- http://www.pit-lane.biz/t3173p60-gp1...vermars-part-2

Brian Callahan
Jan or others, how did you control the tuned pipe wall temperature (or EGT directly?) when testing on dyno? This seemed the most difficult thing to mimic when testing either the GP engines at QUB or my R/C boat engines, in the lab. The inertial dyno or computer controlled brake seem to work best because we can match the test engine's acceleration with reality. On steady-state testing, EGT would simply climb 500, 600, 700, 750 °C until way past reality and the piston would seize.

Frits Overmars
This has always been one of Jan's greatest handicaps. He has asked for an inertial test bench over and over, but Aprilias race director Witteveen, or The Great Leader as we call him, never deemed it necessary....

Jan Thiel
When EGT goes up and up there should be some serious problem with the engine.
We never had pistons seize during our steady state tests.
Working on the dyno continuously 5 days a week!
I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling.

As Frits has written, I would have liked to have also a dynamic testing possibility, with a flywheel.
In my opinion you should simulate a straight, starting at around 10.000 rpm, and shift through the gears
until you reach top speed. And with the airbox as used on the bike, with a ventilator that simulates the raising
air speed as it would be on track! Maybe it is interesting to know that without a ventilator the engine gave
less power with the airbox fitted.

I was told that such a testing system was too expensive.
And unnecessary as we won anyway!

I can also see a disadvantage of 'dynamic' testing.
Because the duration of the test is so short you can get away with very extreme (too extreme?) settings,
without damage.

GrahamB
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Haufen
Yes I know, but part load egt is usually lower than full load egt. And I think most of us would prefer higher part load egt over part load detonation. Of course, how far one could go and how far one would need to go would have to be tested, and how much would be needed would depend on the engine.

Mic
How about much larger travel on the exhaust power valve.
With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Jan Thiel
This causes detonation (auto ignition)
The problem is that the burned gases do not exit the cilinder!
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Jan Thiel
Haufen, We also had such a test bench at Aprlia.
The prototype of this test bench was developed by Apicom in collaboration wit Aprilia.
So we had it first, and now anyone can buy it.
It was helpful but not what I wanted.
A so-called step test.
And without the airbox!

Frits Overmars
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below, but then two-stroke development at Aprilia was terminated because of Dorna's ban on two-strokes

Howard Gifford
Another way to lower HP without sacrificing piston cooling would be to richen the mixture when you want to lower the power. With a signal to a fuel enrichening solenoid you could achieve a power range. It would then be instantaneous and programmable. Not enviornmentally friendly but would work for racing. The mixture ratio difference from high power to low power would need to be just rich enough before a misfire and just lean enough for sustained high power.

The variable tailpipe idea will work but I suspect the pipe temperature would drop off and it would take several seconds to regain full power. But then again rich mixture may have the same problem.
Two strokes are like redheads. Hard to figure out and very temperamental. But when they are happy they are a lot of fun!
HG

Jan Thiel a écrit:
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.

Institute of TwoStrokes
On aftermarket ignitions I use there is a mode I can switch on where a number of indivdual sparks are cut, depending on throttle position. It is now only configured for cutting 1 in every 3 sparks on over run(tps <10% with high rpm). Would that sort of system solve the part throttle detonation? If the number of sparks cut could be varied along with TPS for this to begin and end? If it would be helpful I'm certain the manufacturer would only need a software change to do this.

Jan Thiel
I certainly thought about cutting sparks.
But remember: the problem was AUTO-ignition!

GrahamB a écrit:
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Jan Thiel
Indeed, retarding too much caused detonation!

Institute of TwoStrokes a écrit:
Jan Thiel a écrit: The entering fresh charge is ignited by the remaining, hot, burned gases! You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? On aftermarket ignitions I use there is a mode I can switch on where a number of individual sparks are cut, depending on throttle position. Would that sort of system solve the part throttle detonation?

Frits Overmars
As Jan pointed out, once you have auto-ignition, the engine does not listen to its ECU any more. So you would have to start skipping sparks well before the onset of detonation.
In a foul-stroke your proposed system does work, but a two-stroke would react far from linear. For example, if you skip 1 in 4 sparks, you will loose much more than 25% of engine power because that one missing spark will cause the gasdynamics processes to collapse. The main problem would be to realise a smooth transition from intermittent to full ignition.

Jan Thiel a écrit:
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Haufen
I think I expressed myself unclearly. What I meant was the following:
Imagine your engine with the throttle opened just above the auto-ignition range. Then you have sufficient transfer flow, but too much power. To lower the power, now retard the ignition. Then you still have sufficient transfer flow, but with less power.

I think Honda used auto-ignition to their advantage on two-strokes. As far as I remember they did it with a (very) variable exhaust power valve.

Frits Overmars a écrit:

Mic a écrit:
How about much larger travel on the exhaust power valve. With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Frits Overmars a écrit:
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below.

269228

Haufen
I think I have not gotten behind the variable tailpipe idea, yet. What would you like to vary with it and to achieve which effects? At little throttle openings the pressure inside the exhaust pipe is already very close to atmospheric pressure (if not even) on most engines. And if you had say 100mbar inside the pipe at the critical throttle opening, then the engine might have had more power with a bigger tailpipe.

269228

Frits Overmars
'Opening' the end of the reflector will cause a substantial weakening of the reflected pulse and thus less charging of the cylinder. Izze simple, no?

Haufen a écrit:
Variable transfer timing would be nice also, if feasible.

Frits Overmars
That would be my ideal. Lowering all the transfer roofs would shorten the transfer timing and lengthen the blowdown timing, so the cylinder pressure would drop further before the transfers would open. It would cure the hig revs/low power-detonation and it would improve the power band because a too early-returning exhaust pulse would have less opportunity to push the fresh cylinder contents back into the crankcase.
A controllable transfer height would even make a throttle valve unnecessary.
There's only the little problem of how to build it...

Jan Thiel
Haufen, Auto-ignition usually occurs between 10 to 40% throttle at high revs.
In fast, non full throttle corners.

Retarding the ignition was tried to diminish power.
This makes the exhaust very hot.
Then, when you need full power, it is not there because the exhaust temperatures are wrong.
This takes a little time, when the engine is back to full power you are already at the end of the straight!
The same goes for water injection in the exhaust.
It was tried by Rotax about 25 years ago.
There was a LOT more power at low revs, so the rider had to take it easy when opening the throttle.
But the engine revved a little bit less, because the exhaust temperature did not recover at high revs.
And lap times became actually slower.
After a day of testing the system was switched off.
Lap times immediately improved!

A very important thing when accelerating is the power you have after changing gear.
Spark interruption may be not so good for this!
As I did not have the dyno I wanted this gearchange effect could not be tried on the dyno, very regrettably!
Retarding the ignition and weakening the mixture by powerjet can also have a negative effect on this.
The exhaust temperature should be 'Right' for the No. of revs after you change gear.
If the temperature is too high there will be less power!
So it is REALLY complicated!

TZ350

7th September 2012, 09:45

Page 600 C

Knock Gauge

I have just been putting on my knock gauge on the bucket and when I run her in the drive with the sensitivity set half way, reving the bucket up the gauge went off like a christmas tree and I am wondering what others have there gauges set to?
The gauge is from http://www.knockgauge.eu and the sensor is off a subaru car. It's mounted on a 100cc LC two stroke on a head stud straight onto the head with nothing inbetween if that is any help.

I could even get the deto light showing revving it in neutral - & that was after finding the point of best power was somewhat advanced of where I started & progressively increased till I went too far & went back a little. Wonder if an aircooled motor 'rings' so much that it is not useable?

Been away winning races so will reply now re the deto box.
Calibration is easy, turn it down real low such that the green lights do come on when doing a full throttle run.
Keep turning it up till you get a deto indication somewhere in the powerband, going up on full throttle, or as TeeZee found, when backed off on the overun.
In short - believe what you are seeing, if it shows deto on the overun, then, its got deto in the overun.
This MAY not be an issue when racing as you MAY not damage anything detoing for a short period under these conditions.

But,of course if you have a TPS this means you can use a 3D map, and its easy to pull out a couple of degrees of timing at that point, and the deto will go away - simple.
I found that maximum performance on the dyno meant you had short flickers of deto at nearly all rpm on full throttle,and it lights up when you hit the limiter.

I do several pulls at 1/4, 1/2 and 3/4 throttle,running up against the dyno load, as well as running down on the overun. to generate the TPS driven curve shape.
This enables you to dial up the max advance needed everywhere, then go into the software and back the whole curve down 1 to 2 degrees.

Now you have a good curve shape that the engine actually needs, and any issues on track, can then be taken care of by the box switching the retard input to pull out 2* to prevent unforeseen meltdowns.
I havnt used the deto setup on an aircooled, but I suspect that the deto ringing frequency signal is much bigger amplitude than a watercooled cylinder,meaning you get a much quicker indication of deto approaching.

Means its very sensitive to adjustment, but I say again, if it is flashing deto at one rpm and not at another, then believe what you are seeing, just turning it down so it does nothing, is dumb.

The det amp is very selective about displaying real deto signals.
You simply wind in the sensitivity such that the two greens are on and then the orange will tell you where you are getting close to a knock.

Wind up the sensitivity again and the red will come on in the same spot as the orange did before.
Pull out a degree or two at that rpm and the red will go out - leaving the orange semi warning.
Keep doing this till the curve is optimised.

It works the other way as well, no orange and you can be sure you dont have enough advance at that point.
Then you can run the earth line back to the Ignitech with only one or two degrees of deto retard a a failsafe.
If you try to run say 3* of retard with the sensor output connected to the Ignitech, it works so fast the light never comes on, so you cant see whats happening.

The piezo sensor will easily show the missfire from hitting the limiter, so it will also show a big end knock, as well as the piston hitting the head.
Dont know about excessive piston slap , but probably.
Plenty of "noise" sources in a 2T.

The Knock Gauge can easily be adapted to be a Det Counter as well if you buy it with option 1 for retarding the IgniTec’s ignition and option 2 for a 0-5V pulse signal out for each det the a Counter can see.

Quite a bit of info on counters you could use with the Knock Gauge here:-

703TR002N-512D RS part number 183-5952 $63.50 ... 5-12V and less than 10mA so easily self powered and at 500Hz fast enough to count all deto events as seen by the Knock Gauge or similar, as 200Hz in a 2-Stroke equals 12,000 rpm.

Someone elses links list:-
http://www.rzrd500.com/phpBB2/viewtopic.php?t=2438
Might be worth a look.

This problem reminds me of an issue I had with my TS/RGV motor years ago. On the dyno at certain times you could see flames dancing round inside the carburetor. This was a full crankcase reed conversion. After a long time, over a year, in an attempt to fix the problem I just advanced the timing as far as it would go. The flames disappeared and it starting making modest power.

It seems from what people have been saying that this problem of detonation is evident on all(?) high performance 2-strokes. There may be a small number of cures but for whatever reason they have never been implemented. Thinking about it this could be what stopped my bike at Taupo. The piston was certainly hammered with cracks all over and Dave did say he was cruising in the corners which probably created the conditions needed for the problem to manifest.

The simplest answer seems to be to ride hard, maybe even changing down shift patterns - letting the revs drop as you brake and then dropping the gears as needed from lower revs.

More on Exhaust port Radius's

I have thought of it like so: The 3.5 number is the radius of the fillet applied.

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In my pic at least, there are (exaggerated): the top corner radii ^ the top edge radius until 196* ^ the drawn red radius until 202*.

I think the flat sound to the exhaust is due to the top exhaust port chamfer blunting the exhaust note as the port is no longer cracking open suddenly.

If you only added a chamfer to the existing port, outflow will improve, wasting less energy in turbulence and sending more energy the pipe. It will also have raised the exhaust timing, opening the port when cylinder pressure is higher; another reason for the pipe to perform better.

I believe the big radius at the bore centre line has two effects.
Firstly is to improve the bulk blowdown flow at low opening angles of the piston controlled port orifice, due to the gas attaching early to the roof.

Secondly the exiting wave amplitude is lowered and smoothed out by the gradual ( instead of a sharp edge ) port opening.

This would improve the scavenging action bandwidth, but the peak value is probably then raised as well, simply because the port opens earlier when the pressure above the piston is greater.
Thus you get the best of both, a wider effective scavenging action, combined with a higher peak value, making the pipe work better over a wider range.

The 75% area at the cylinder exit is just something I discovered after running hundreds of sims, most of them worked best with an oval to round transition in the flange that started with this area and the pipe header diameter equalled the total effective area of the ports.

Its been tested and proven so many times now, by so many other people, that it should be the first mod to make to any T or triple port engine.

Here is a pic of one I have just done, that happened to have a tapered spigot - enabling the Aux ducts to be run all the way down into the pipe.

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Check the big rad on the transfer duct/bore edge.

In all the engines I have done the area at the flange face is approx equal to the main port effective area, or approx .75 of all 3 ports.
The header diameter is equal to the effective total of all three ports.

The trend has been for a long time to reduce the volume of all the ducts in modern engines.

Aprilias Ex duct had the bottom filled in such that it was higher than BDC and the corners filled to reduce short circuiting from the A ports.
And the cylinder duct vol was CNC machined to be smaller and smaller in total vol, but in the process heavily promoting flow from the Aux ports to increase effective blowdown flow.

One of the transfer duct entrys was smaller than the port area ( the B and biggest port ) and for sure the ratio between the A and B port duct entry areas was tested
to death within the limitation of the case available area between the studs, by several of the 100 R&D festerers.

The idea here is to reduce the inertia of the initial volume available to the cylinder, that has to be accelerated out of the duct by the negative pressure ratio across the port.
That Cagiva cylinder is very "old" technology.

The secondarys facing each other relatively flat will always collide, but the hooks rotate the flow under the boost as it exits the port ( easy to see with the tap water Jante trick),clearing out a big "dead" area
in front of the rear port.

All modern race engines have a nozzle restriction at the flange face, as big T ports and tripple Exhausts loose alot of velocity going into the header.
Rule of thumb is a 75% of the effective EX area at the flange.
Stepped oval duct into a round flange does work, but I have used a CNC oval to round transition in the spigot for years, as has Honda in A kit, and Aprilia factory engines, this works way better.

The stinger nozzle effectively removes the stinger tube length from the equation - it was developed for Spencers NSR that had one stinger 150 long, the other was 450. The nozzle is around 2 to 3mm smaller than the tube stinger .

Simple answer re the odd shape and reduced area of the Ex duct exit is that with a 3 port cylinder, the area of the main port is plenty big enough to support the gas flow
created by the power being made.

The big Aux additional area allows better Blowdown STA, but this area is only needed above TRO.
Thus having a huge duct simply drops the velocity, reducing the wave amplitude into the header.
The Aprilia shape promotes the flow from the Aux ports by keeping the extra horizontal area all the way into the pipe - thus helping blowdown flow and overev power..

Reducing the duct vol by having area reducing steps, keeps the velocity high and again promotes the flow regime in the side ports. There may be a case to say that the steps reduce backflow from the pipe at low rpm when it is too short,but for sure there is no outflow disruption,and in any case tests showed that power went up as the duct became smaller.
I have exhaustively ( pun ) tested the vol/shape effects on a T port ( as has Mr H ) and an oval to round transition with no steps works better. A factory A Kit has a very small 41 by 32 oval, with a CNC transition into a 41 header.

Tuning using the exhaust gas temp.....

One thing you wont get is deto of the end gases without loosing power.
The phenomenon of deto is caused by temp/pressure creating free radicals, this process eliminates a huge amount of the available energy in the combustion fuel.
And once the radicals are formed, they are self-sustaining, and cause a runaway reaction process - consuming more energy.
This is exactly why the egt drops when you are too lean, and deto starts - no energy left to create heat - ie no power.

Each engine is different but if a setup has the optimum com and the timing in the ballpark of 15* at peak power, then Avgas or leaded racegas around the equivalent RON
will always be maxed out at around 1250* - @ 150mm min from the port.

Unleaded likes to be alot richer and makes more power with more advance so that setup makes best power at around 1050.

Not enough com or advance, and the peak safe egt will rise, but power wont, it will just rev on more due to the higher wave speed.

But you have still got it wrong about the air on the day.
You can jet to get the optimum egt, no matter what the RAD says, and it will be in the same state of tune - just using all the oxygen in the air available and mixing it with the correct amount of fuel.

On a hot day,or low Baro, it will hit 1250 but simply make less power, due to less oxy and thus less fuel = less BTUs burned.

The 400 F3 we thrashed on the dyno and at 12,000 held by the dyno for around 30 secs it settled at 12000* F - 96 Hp with no fade.

Thus this is a good safe baseline for the new owner who may not have the tuning smarts to determine what is good or not - but if he has to change jets 3 times during a day
to see 1200 then he will be well on the way to learning what to do.

Matters not how the best temp was derived, on track or on the dyno.
With the gauge running and say a 180 main, then going down to 178,if I only see a small increase in temp ( 20*F) then that instantly means that more heat energy is being used somewhere - not in heating the Ex gas to make power.

If the original temp was 1240, then that will be the ref temp for any air conditions on any day.
With the example I gave we had a 3 jet spread during the day, a very cool dense morning, and a very hot dry afternoon.
In both cases the egt settled at around the same mark. One jet leaner and we would be in the danger zone - one richer and we wouldn’t be the fastest by a mile as we were.