ESE's works engine tuner

[Flettner]

A prick of a thing to start.
Technique, exhaust port just open, then boot it, Left boot.
Two from two today, two attempts, two successes. E85, smells nice.
No turbochargers here.

[Muhr]

As i understand, it is just regular ones, but small cores.

So the question is what is your stinger temp...
https://liu.diva-portal.org/smash/get/diva2:1325593/FULLTEXT01.pdf

[Muhr]

A "normal" catalytic converter as on gasoline fueled passenger cars are "three way" catalytic converters requiring stochiometric AFR.

The oxidation catalytic converter is a different type that operates in an excess level of oxygen, typically found on diesel engines.

Could it not be that he is referring to something like this: https://emis.vito.be/en/bat/tools-overview/sheets/catalytic-oxidation
He also chooses to use the term EBK which in Swedish is the abbreviation for after burn chamber

[SwePatrick]

So the question is what is your stinger temp...
https://liu.diva-portal.org/smash/get/diva2:1325593/FULLTEXT01.pdf

High enough ;)

Video below prooves that often people overthink things, it´s a normal cat with a small 3hp engine running way rich (colder exhausts) and it lights up quite easily when rich.
And,, people running lean to light them up......


https://www.youtube.com/watch?v=ekQcy6GN1pM

Some info:
https://www.open.edu/openlearn/science-maths-technology/science/chemistry/the-three-way-catalytic-converter/content-section-1.5.2

[sniemisto]

I’d like to share my dyno result (Derbi D50B0) with new head insert even though it’s not pure back to back test as 1. old head had leak and 2. I changed squish from 0,5 to 0,4mm.

Peak was moved 400 rpm lower and some over rev power was lost. Dashed line is new one:

https://uploads.tapatalk-cdn.com/20210518/e2fcd667e203650876749d14455c6650.jpg

More than half of over rev power was gained back and little for peak with ignition adjustment. 1 degree more advance on peak power and 1 degree later timing for over rev. Dashed line is with new advance curve:
https://uploads.tapatalk-cdn.com/20210518/90ca2497764c407446dbfe50c10bd9a0.jpg

I made also some testing with different reeds. Test was done with 10mm spacer between block and crankcase and with no changes to ignition or jetting. I had been running with CR85 reed block and boyesen fiberglass 0,49mm petals. Malossi VL18 0,32mm carbon fiber (dashed line) was only better at over rev and worse in before.
Original Honda 0,41mm petals (dotted line) had also better over rev compared to boyesen with slightly reduced top:
https://uploads.tapatalk-cdn.com/20210518/75c29f9f215cc783d18878eefb27938e.jpg

Honda petals looks bit different than normal fiberglass, they look like fiber reinforced plastic.

[TZ350]

More of Alex's adventures at 2Stroke Tuning.

<iframe width="560" height="315" src="https://www.youtube.com/embed/6N8gFsHRO_o" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

[SwePatrick]

I noticed a thing, everytime you post new video from Norway, the thread dies a little.
time to wake it up again.

How would you guys deisgn a combustionchamber for an 85cc motocross with small mods like v-force and pro circuit pipe?

[F5 Dave]

By not using a a ProCircus pipe.

[SwePatrick]

That´s what i try to say to the friend, but he is a cataloguetuner.

[F5 Dave]

Well he'll be wanting a Dingleberry mod carburetor, a moleskin seat cover, Eeljuice chainlube, and of course a faktoryEFX decalkit.

[I may have made some of these things up]

[Pursang]

How would you guys design a combustion chamber for an 85cc motocross with small mods like v-force and pro circuit pipe?

1: Take the stock factory head, set the squish clearance, adjust the CR for low end, mid range or top end power.

2: Dress off any casting flash, vapour blast it, CNC mill in your initials and the words "Racing" or "Factory" or both.

3: Charge as much money as the client can bear.

Cheers, Daryl

[Grumph]

1: Take the stock factory head, set the squish clearance, adjust the CR for low end, mid range or top end power.

2: Dress off any casting flash, vapour blast it, CNC mill in your initials and the words "Racing" or "Factory" or both.

3: Charge as much money as the client can bear.

Cheers, Daryl

Substitute "Client's father " and you're onto it.

[F5 Dave]

1: Take the stock factory head, set the squish clearance, adjust the CR for low end, mid range or top end power.

2: Dress off any casting flash, vapour blast it, CNC mill in your initials and the words "Racing" or "Factory" or both.

3: Charge as much money as the client can bear.

Cheers, Daryl

I'm strangely tempted.

Where do I send my money ?

[koenich]

If you add "revs to the moon" I'll send my engine tomorrow!

Gold :corn:

[Muhr]

Hi, does anyone have Dyno graphs on Tm Mx 125 and or Ktm sx 125 2017 and newer. Would help a lot! Working on an engine for a friend and the results are deplorable. Have tried lots of different things but it absolutely does not want to breathe over 11k.

[Tim Ey]

Hi, does anyone have Dyno graphs on Tm Mx 125 and or Ktm sx 125 2017 and newer. Would help a lot! Working on an engine for a friend and the results are deplorable. Have tried lots of different things but it absolutely does not want to breathe over 11k.

125SX from 2016 (Model 2017)
349129
Before and after tuning. I have written more about it roughly a year ago.

Have you checked the Ignition? The 2017 125 SX is advancing to the moon after the retardation for overrev. I would consider it poor mans rev limiter...

[Muhr]

125SX from 2016 (Model 2017)
349129
Before and after tuning. I have written more about it roughly a year ago.

Have you checked the Ignition? The 2017 125 SX is advancing to the moon after the retardation for overrev. I would consider it poor mans rev limiter...

Thanks Tim!
In my case it is a TM 125 but the competition will include sx engines.
Then I know where the bar is. The TM cylinder has a port map similar to rs125 from the 90s

[jonny quest]

Inertia dyno testing, motor shows horsepower gains on the bottom end lower mid range.

On the track the dyno gains aren't felt by the rider.

Why is this?

[SwePatrick]

He probably never uses the powergained area.

[jonny quest]

He probably never uses the powergained area.

Rider complains it doesn't have enough bottom end power, compared to what he had before. But it clearly shows a decent gain on dyno

[SwePatrick]

Yes,, that may be why he keeps engine up top as a bad habit.

Very often this happens.

[Vannik]

Inertia dyno testing, motor shows horsepower gains on the bottom end lower mid range.

On the track the dyno gains aren't felt by the rider.

Why is this?

Maybe:

1. Pipe and engine was not at the correct temperature when dyno run was started; or
2. Acceleration rate on dyno is too fast showing the effect of a longer pipe because the pipe temperature does not heat up fast enough: or
3. ???

[jonny quest]

Maybe:

1. Pipe and engine was not at the correct temperature when dyno run was started; or
2. Acceleration rate on dyno is too fast showing the effect of a longer pipe because the pipe temperature does not heat up fast enough: or
3. ???

Very valid answers/questions. I didn't mention this in my original question...which now will change answers dramatically.

This particular question of mine is on a 4 stroke, with pretty consistent testing on my part.

I have an idea as to why this is the case to my original question, but I didn't want to skew the replies as of yet

[Frits Overmars]

Maybe:
1. Pipe and engine was not at the correct temperature when dyno run was started; or
2. Acceleration rate on dyno is too fast showing the effect of a longer pipe because the pipe temperature does not heat up fast enough: or
3. ???#2 is a common cause. On low-inertia dynos it may be necessary to make a dyno run in top gear if you want to mimic track behaviour in third or fourth gear.


Rider complains it doesn't have enough bottom end powerWimps! What those riders need is a ride on a twelve-speed Kreider or a fourteen-speed Suzuki.
OK, we've outgrown the times of 7-rpm power bands, but that's no excuse not to use your gearbox.
What has struck me in the course of the last half century: the best riders complain the least
(could of course also be because they have the best engineers on their side, right Jan? :first:)

[jonny quest]

I surely didn't put enough information in my original, nor second post regarding my question.

My power spread question regards an MX bike.

Riders want Enduro low end, Road Race top end. It truly isn't feasible to shift when you need too, or are supposed to on a MX track. Clutches are abused in almost every corner keeping revs up. If you happen to run out of gear on the lip of a jump... it's not pretty.

[F5 Dave]

Maybe:

1. Pipe and engine was not at the correct temperature when dyno run was started; or
2. Acceleration rate on dyno is too fast showing the effect of a longer pipe because the pipe temperature does not heat up fast enough: or
3. ???
An all-gears run was always important on inertia dyno testing.

[lodgernz]

50 CC AM6 2 stroke with turbo which set the land speed record of 233 KPH /144 MPH .
349138

[Peljhan]

Didn't Frits once enlighten us, that actual record engine was not this one, but "standard" with methanol and nitro?
I am wondering, what happened with Dutch attempt Green Tulip?

http://www.groene-tulp.nl/cms/
https://www.flickr.com/photos/teamheronsuzuki/sets/72157641769130104

Random question.. What would be good material to make cylinder studs? Which heat treatment? I know Frits would say Dilavar, but I think that is out of reach for me.

[Flettner]

Didn't Frits once enlighten us, that actual record engine was not this one, but "standard" with methanol and nitro?
I am wondering, what happened with Dutch attempt Green Tulip?

http://www.groene-tulp.nl/cms/
https://www.flickr.com/photos/teamheronsuzuki/sets/72157641769130104

Random question.. What would be good material to make cylinder studs? Which heat treatment? I know Frits would say Dilavar, but I think that is out of reach for me.

I would just use 4140 or 4340.

[Frits Overmars]

Didn't Frits once enlighten us, that actual record engine was not this one, but "standard" with methanol and nitro?
I am wondering, what happened with Dutch attempt Green Tulip?
http://www.groene-tulp.nl/cms/
https://www.flickr.com/photos/teamheronsuzuki/sets/72157641769130104.
Some myths are very persistent. The many pictures of the Buddfab turbo-Minarelli-50 are well known; pictures of the engine actually used in the Buddfab record machine are as rare as hen's teeth but they do show that the turbo was left at home in favor of a nitrous oxide (not nitromethane) injection system, below.
349142

What happened to the Green Tulip? It's Bonneville participation got drowned in rain and I haven't heard anything about it since. I would have visited its rider, my friend Aalt Toersen (shown below in his office) if it hadn't been for this damned Covid that makes traveling almost impossible.
349141

[KKT]

Eric Noyes writes that the 2008 144mph record run was done with the turbocharger fitted:

http://www.landracing.com/forum/index.php?topic=18228.0 (there are two pages to read)

[TZ350]

.
Posted for those like my self who are following 2Stroke Stuffing's adventures with his supercharged engine. https://youtu.be/47sf_5IQeMI

349144

I have been pretty quiet my self lately re-building a 250cc pre 72 Post Classic racer with its rotary valve Kawasaki engine. Flettner has given me a lot of help with this. Also someone else, the DoldGuy donated the carburetor and also helped me a lot with getting the DynoJet dyno working again.

There is nothing to special about this engine. It follows the current conventional single exhaust, 5 transfer two stroke tuning ideas. And the timing and pipe design was developed using EngMod2T software. It will run on a petrol/acetone/methanol mix. Methanol for cooling. Acetone to stabalise the Methanol against pre ignition. Petrol to adjust the engine's running temperature.

I am working on finalising the pipe design now and expect, because the engine will be Methanol cooled the pipe will be noticable shorter than a straight petrol pipe because the average pipe temperature will be much lower. I am not entirly sure about this so if anyone has experiance with this any tips would be welcome.

349145

This is not my bike but gives a bit of an idea of what they looked like back in the 70's.

[Grumph]

I can observe that a 250 gearbox kart I helped with - on a Meth/Tolulene/acetone mix - won a few Nationals using the stock MX pipe dimensions.
Never bothered to develop a pipe specifically for that fuel.

From my experience with Methanol in 4T's, the exhaust temps are not that much cooler.

[teriks]

.
I am working on finalising the pipe design now and expect, because the engine will be Methanol cooled the pipe will be noticable shorter than a straight petrol pipe because the average pipe temperature will be much lower. I am not entirly sure about this so if anyone has experiance with this any tips would be welcome.

Not that I would draw much of a conclusion from it for your engine, but I see pipe temperatures not too far from Wobbly's gasoline numbers on my tiny stuff running 80% Methanol, 20% Castor oil (as per the class rules).

[SwePatrick]

My kawasaki methanol 212cc engine always performed best when around 430c exhaust temp, probe was three pistondiams down in header.

[pete376403]

.
Posted for those like my self who are following 2Stroke Stuffing's adventures with his supercharged engine. https://youtu.be/47sf_5IQeMI

349144

I have been pretty quiet my self lately re-building a 250cc pre 72 Post Classic racer with its rotary valve Kawasaki engine. Flettner has given me a lot of help with this. Also someone else, the DoldGuy donated the carburetor and also helped me a lot with getting the DynoJet dyno working again.

There is nothing to special about this engine. It follows the current conventional single exhaust, 5 transfer two stroke tuning ideas. And the timing and pipe design was developed using EngMod2T software. It will run on a petrol/acetone/methanol mix. Methanol for cooling. Acetone to stabalise the Methanol against pre ignition. Petrol to adjust the engine's running temperature.

I am working on finalising the pipe design now and expect, because the engine will be Methanol cooled the pipe will be noticable shorter than a straight petrol pipe because the average pipe temperature will be much lower. I am not entirly sure about this so if anyone has experiance with this any tips would be welcome.
Have you checked out Harry Klemms F5 / F8/ F9 preparation tips? Lots wrong with those engines as they left the factory, but lots of potential when put together properly.

[Muhr]

Hi everyone, does anyone know a 115-120 conrod that has a 22mm pin. Have had a hard time finding anyone, last night's solution became a sleeve. Does not feel optimal, maybe someone who has made some other good solution to this problem.
a bonus in this case was that this conrod we put in had some weight which compensated for the change of pin quite well.

Muhr

[OopsClunkThud]

Hi everyone, does anyone know a 115-120 conrod that has a 22mm pin. Have had a hard time finding anyone, last night's solution became a sleeve. Does not feel optimal, maybe someone who has made some other good solution to this problem.
a bonus in this case was that this conrod we put in had some weight which compensated for the change of pin quite well.

Muhr

I think RD400 is 115 with 22mm pin

https://www.ebay.com/itm/254698877756?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=254698877756&targetid=4580496732614416&device=c&mktype=&googleloc=&poi=&campaignid=418233788&mkgroupid=1230353745471221&rlsatarget=pla-4580496732614416&abcId=9300542&merchantid=51291&msclkid=fee3e2fcaa82187164cf824ad7d84a08

[katinas]

Hi everyone, does anyone know a 115-120 conrod that has a 22mm pin. Have had a hard time finding anyone, last night's solution became a sleeve. Does not feel optimal, maybe someone who has made some other good solution to this problem.
a bonus in this case was that this conrod we put in had some weight which compensated for the change of pin quite well.

Muhr

Hi Muhr , KTM SX 200 conrod length 118 mm 22 mm pin ( 28 mm big end eye and 20 mm small end eye). Width 16 mm.
Big end outside 40 mm.

[wobbly]

TeeZee , I have done several projects using Methanol.
If tuned by way of pretty much stock ignition timing and going to 18 to 20 : 1 compression , the optimal egt seems to be around 420*C.
This is well over rich , but is perfect for an air cooled in this respect.
Thus the pipe average wall temps input for EngMod become 425 x 420/650 = 275* @ peak power and around 75% of that at the bottom of the powerband.

[Frits Overmars]

... a bonus in this case was that this conrod we put in had some weight which compensated for the change of pin quite well.So you had to use a lighter pin and therefore you are glad that the con rod is heavier?
A lighter pin or small end bearing or con rod small end or piston or ring will increase the balance factor and reduce the reciprocating balance force, while the rotating balance force remains unaltered. In short, lighter is always better. It's the balance forces, not the balance factor, that cause vibrations.

In theory, if you keep reducing those reciprocating masses, you may reach a point where the balance factor exceeds 100%, and then the vibration will increase once more, but now with a 180° phase shift. But in real life I've never seen that happen.

[wobbly]

Haha Frits , you are making an assumption we all live in real life.

[husaberg]

I can't be arsed formatting it
But I have a few spreadsheets to put into one document one day it is not pretty.
349148
There is double-ups and you will need to double check and there is likely a few 4ts
CLICK ON IT 3 TIMES

[sniemisto]

.
It will run on a petrol/acetone/methanol mix. Methanol for cooling. Acetone to stabalise the Methanol against pre ignition. Petrol to adjust the engine's running temperature.


What mixing ratios you planned to use? I’m interested in trying something similar on my air cooled Tomos.

[speedpro]

I used the same ingredients in my bike's fuel. 25% petrol(98), 75% methanol. With 20L of that mixed I then tipped in Acetone until it blended. Typically it took about 1L of acetone. It instantly turned from a cloudy mixture to perfectly clear as I tipped in the acetone. I used 100 octane and toluol for a while but 98 is something like 30% toluol so no need to add more. Given time the fuel will dissolve most flexible fuel hoses.

[Muhr]

Thank you all for the help (Husa impressive!) I look around among your suggestions and see what I can find.

Frits
Yes that's how it is. In this case, we change the deck height, cylinder, piston, conrod length and head. And do not end up super bad when it comes to balance factor or change the receiver weight significantly without touching the crankshaft.
little win win effort vs outcome. (22mm pin is big end)

[peewee]

Hi everyone, does anyone know a 115-120 conrod that has a 22mm pin. Have had a hard time finding anyone, last night's solution became a sleeve. Does not feel optimal, maybe someone who has made some other good solution to this problem.
a bonus in this case was that this conrod we put in had some weight which compensated for the change of pin quite well.

Muhr

yes ktm200 may suit you but check the prox catalogue for more options. maybe you can bore the pin bore in the web as well. i did that to fit a cr500 conrod to a ktm and its still holding up well

[Frits Overmars]

349151
-------------------------

[TZ350]

Haha Frits , you are making an assumption we all live in real life.

Yep, I have found reality to be over rated ........ :laugh:

[TZ350]

.
Although I have used Methanol and Acetone before. I liked the results but need to make a better job of it for the post classic racer.

Big shout out and thanks to:- Grumph, Teriks, SwePatrick, pete376403, Flettner and Wobbly for their thoughts and experiance with using Methanol. It has been a great help.

[TZ350]

349151
-------------------------

Plus +++1 ...... Happy Birthday Jan.

[lodgernz]

I can't be arsed formatting it
But I have a few spreadsheets to put into one document one day it is not pretty.
349148
There is double-ups and you will need to double check and there is likely a few 4ts
CLICK ON IT 3 TIMES

I'm sure we would all appreciate an Excel file of all that.
Looks like there are some entries lost at the top. Were those 4T?

[katinas]

Happy Birthday Jan.

[Muhr]

I tried to convert to excel, do not know how well I succeeded. Someone is welcome to take a look!

So I have not proofread everything, only converted and cleaned it up with macro

[lodgernz]

I don't know where I got this, but probably on this thread.
349165

[Condyn]

More connecting rods. http://www.transcanimports.com/downloads/Snowmobile%20Catalogue/Engine%20-%20Connecting%20Rods.pdf

[husaberg]

Sorry i am late happy birthday Jan.


https://www.youtube.com/watch?v=cxK_zWgw6gY
side note the Merlin was of course a 4V/cylinder

[Muhr]

These pictures pop up from time to time. Does anyone have information about this change?

[Frits Overmars]

These pictures pop up from time to time. Does anyone have information about this change?Your pictures show an Aprilia RSA125 with 'improved' crankshaft. The original crank wheels had flat inner surfaces that were 16 mm apart. My RSA125 pics are not too clear but the picture of the two RSW250 cranks shows what I mean.
Then, after Jan Thiel went into retirement in 2008, some geniuses at the factory grabbed their chance to 'correct' the crankshaft, fitting aluminium stuffing disks to the insides of the crank wheels in order to reduce the crankcase volume.
Now apparently the crank has become 'even better' with full steel wheels. Yet everybody wonders why a 2009 RSA125 was slower than the 2006 version...
349185349184 349182 349183

[Muhr]

Your pictures show an Aprilia RSA125 with 'improved' crankshaft. The original crank wheels had flat inner surfaces that were 16 mm apart. My RSA125 pics are not too clear but the picture of the two RSW250 cranks shows what I mean.
Then, after Jan Thiel went into retirement in 2008, some geniuses at the factory grabbed their chance to 'correct' the crankshaft, fitting aluminium stuffing disks to the insides of the crank wheels in order to reduce the crankcase volume.
Now apparently the crank has become 'even better' with full steel wheels. Yet everybody wonders why a 2009 RSA125 was slower than the 2006 version...

Ok thanks for the explanation Frits! So this milling is a further development in the same spirit as the crankshaft. When they noticed that the engine got worse with less volume!?

[husaberg]

Your pictures show an Aprilia RSA125 with 'improved' crankshaft. The original crank wheels had flat inner surfaces that were 16 mm apart. My RSA125 pics are not too clear but the picture of the two RSW250 cranks shows what I mean.
Then, after Jan Thiel went into retirement in 2008, some geniuses at the factory grabbed their chance to 'correct' the crankshaft, fitting aluminium stuffing disks to the insides of the crank wheels in order to reduce the crankcase volume.
Now apparently the crank has become 'even better' with full steel wheels. Yet everybody wonders why a 2009 RSA125 was slower than the 2006 version...
349185349184 349182 349183

I had read before re the crankstuffing but I assumed he was meaning this bit?
349187

[Frits Overmars]

Ok thanks for the explanation Fritz! So this milling is a further development in the same spirit as the crankshaft.hrWhen they noticed that the engine got worse with less volume!?Your guess is as good as mine, Muhr. Ask the geniuses :msn-wink:.

[Muhr]

Your guess is as good as mine, Muhrz. Ask the geniuses :msn-wink:.

Lucky you're such a generous man when it comes to other people's shortcomings Frits.:msn-wink:

[TZ350]

.
349189

I am a great fan of increasing the crankcase volume. Or more exactly the volume at the start of the transfer ducts. So that the pipe has a bigger volume of mixture to suck up into the cylinder. Triming the inside of the flywheels and fitting a longer rod with corresponding cylinder packer for extra volume under the cylinder. The idea about increased crankcase volume posted by Frits and Jan from their days at Aprilia have worked well for me.

349188

[jamathi]

Your pictures show an Aprilia RSA125 with 'improved' crankshaft. The original crank wheels had flat inner surfaces that were 16 mm apart. My RSA125 pics are not too clear but the picture of the two RSW250 cranks shows what I mean.
Then, after Jan Thiel went into retirement in 2008, some geniuses at the factory grabbed their chance to 'correct' the crankshaft, fitting aluminium stuffing disks to the insides of the crank wheels in order to reduce the crankcase volume.
Now apparently the crank has become 'even better' with full steel wheels. Yet everybody wonders why a 2009 RSA125 was slower than the 2006 version...
349185349184 349182 349183

Was the 2009 RSA really slower than the 2006?
Are you 100% sure? Dyno test?
I tried to ask the dyno-man but he did not respond me....
He simply said that the crankcase volume was too big!
They also tried a Honda-type exhaust port/duct.
He admitted that this was worse, 1,5HP less.
I think he should have known better after al the broken exhaust bridges we had at DERBI!!!! Not ONE cylinder lived longer than 6 weeks....
Is there any other reason why a reduced crankcase volume could be better?
Throttle response?
What would be the upper limit of crankcase volume?

[Frits Overmars]

Was the 2009 RSA really slower than the 2006? Are you 100% sure? Dyno test? I tried to ask the dyno-man but he did not respond me.... He simply said that the crankcase volume was too big! ... Throttle response? What would be the upper limit of crankcase volume?No dyno test results Jan. If they would not give those results to you, they certainly were not going to give them to me. But a dyno-man refusing to respond to a question from the engine creator, is already an answer in itself, wouldn't you say?
The difference between the 2009 and 2006 models stems from the riders' seat of the pants. And it should be possible to find conformation in top speed comparisons.
There may be an optimal crankcase volume regarding throttle response for reed valve engines, but I haven't seen it for disc-valve engines.

[Haufen]

Is there any other reason why a reduced crankcase volume could be better?
Throttle response?
What would be the upper limit of crankcase volume?

Happy belated birthday, Jan!

I found smaller crankcase volumes to be less sensitive in regards of jetting. With larger volumes, jetting may get very borderline at some point. A smaller volume gave me the same power and allowed for a much more robust and forgiving jetting and general setup. Both volumes had their individual inlet timings deduced on the dyno. So I'd say it's not only the smaller volume in my case, but the smaller volume which allowed for a better overall setup of that engine when also other parameters were tweaked.

I was planning to do further testing with that engine in order to find out the tipping points of case volume, i.e. when is it too small etc. but unfortunately did not get to it for some time now. Also, I want to do some tests with the same volume to find out WHERE to place the volume and if this is even important at all. I can imagine having a nice reservoir at the transfer entry might be better compared to an engine with cutouts in the crankwebs or extra volume in between the webs as in the latter case, the mixture might not be available in time.

[Vannik]

I found smaller crankcase volumes to be less sensitive in regards of jetting. With larger volumes, jetting may get very borderline at some point. A smaller volume gave me the same power and allowed for a much more robust and forgiving jetting and general setup. Both volumes had their individual inlet timings deduced on the dyno. So I'd say it's not only the smaller volume in my case, but the smaller volume which allowed for a better overall setup of that engine when also other parameters were tweaked.


I assume this is with a reedvalve engine?

In what range did you experiment?

I have always wondered about the influence of where the mixture is "stored" in the crankcase. Are you planning tests of this?

Cool info, thanks for sharing.

[jamathi]

No dyno test results Jan. If they would not give those results to you, they certainly were not going to give them to me. But a dyno-man refusing to respond to a question from the engine creator, is already an answer in itself, wouldn't you say?
The difference between the 2009 and 2006 models stems from the riders' seat of the pants. And it should be possible to find conformation in top speed comparisons.
There may be an optimal crankcase volume regarding throttle response for reed valve engines, but I haven't seen it for disc-valve engines.

Did'nt Hans Spaan test the difference?
The RSA won the world championships from 2008 until 2011.
So they were no so bad...

[Haufen]

I assume this is with a reedvalve engine?

In what range did you experiment?

That was with a rotary valve engine. I was able to reduce the volume by around 60cm³ in between these tests.



I have always wondered about the influence of where the mixture is "stored" in the crankcase. Are you planning tests of this?

Cool info, thanks for sharing.

Yes, I am planning to test this. Unfortunately, the crank with the smaller and already prepared webs is no longer with us, but I'll figure something out. Also, I want to reduce the volume even more using a 3d printed plastic insert to see if there is a tipping point somewhere on the way.

:drinknsin

[wobbly]

What many dont seem to get is that there is no " flow " from the case , thru the transfer ducts and out the port into the cylinder - even around BDC where the most bulk flow occurs.
There is more volume in the ducts , than there is mixture transferred into the cylinder.
Having a greater volume directly below the transfer duct entries may have a beneficial effect on power , rather than volume that is effectively " trapped " inside the crank.
But I believe a change in total volume , that moves the case Helmholtz frequency , has more influence.
RV engines " like " big case volumes , no matter how its achieved.
Reeds I have found have a tipping point at exactly 1.3 ratio . Any bigger than this and the reed stiffness has to be changed to so soft , they loose control and flutter .

[F5 Dave]

So what if you are trying to compensate for an old engine with thin elevator transfers of limited volume? That collection area may be more critical so testing could be skewed if the design tended towards that unfavourable situation. Perhaps.

[SwePatrick]

What many dont seem to get is that there is no " flow " from the case , thru the transfer ducts and out the port into the cylinder - even around BDC where the most bulk flow occurs.
There is more volume in the ducts , than there is mixture transferred into the cylinder.
Having a greater volume directly below the transfer duct entries may have a beneficial effect on power , rather than volume that is effectively " trapped " inside the crank.
But I believe a change in total volume , that moves the case Helmholtz frequency , has more influence.
RV engines " like " big case volumes , no matter how its achieved.
Reeds I have found have a tipping point at exactly 1.3 ratio . Any bigger than this and the reed stiffness has to be changed to so soft , they loose control and flutter .

Yes,, i agree.
I like to compare when opening the transfers with popping a balloon.
Engine has been filled in crankhouse(balloon), piston blows up pressure in the balloon and the transfers are popping the ballon.

[Condyn]

F5, wobbly found my piston port vintage air cooled engine liked a ccr of 1.28.

Quick question for anyone about connecting rods. Is there a proper way to machine or ream the small end eye open 2mm for a larger pin? There looks to be plenty of extra material so I am confident it would still retain its strength in that area. I am just unsure as it is a bearing surface. Thanks.

[husaberg]

F5, wobbly found my piston port vintage air cooled engine liked a ccr of 1.28.

Quick question for anyone about connecting rods. Is there a proper way to machine or ream the small end eye open 2mm for a larger pin? There looks to be plenty of extra material so I am confident it would still retain its strength in that area. I am just unsure as it is a bearing surface. Thanks.

Ask Ken he makes such objects.


Frits, just saw your post....your proposed specific power index looks more meaningful and relevant.

Still, I'll post what I was going to post

Below, as a refresher, is link to explain BMEP:

http://www.epi-eng.com/piston_engine_technology/bmep_performance_yardstick.htm

Not sure if this below covers the full history:

https://en.wikipedia.org/wiki/Rolls-Royce_Crecy

However, if it was going to seize, I’d take it in a tractor rather than 25,000 feet in the air…just a simple pain avoidance preference though…

[Condyn]

Thanks Husa, are you linking me to Ken or is there something buried in there? I did not have a proper look, however did not find anything of relevance right away.

[Frits Overmars]

I want to reduce the volume even more using a 3d printed plastic insert I tried something similar in a Rotax 124 kart engine which basically was a 125cc crankshaft in a 250cc MX engine. That was in 1978, so no 3D printing then, just me pouring epoxy.
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The effect was positive, but one of the mechanics, wishing to make it nicer, substituted my epoxy casting with a neat aluminium filler ring. The result was disappointing.
As it turned out, the positive effect of the epoxy casting was not due to its volume reduction but to its thermal insulating effect within the crankcase, keeping the gearbox heat away from the inhaled mixture.


Having a greater volume directly below the transfer duct entries may have a beneficial effect on power, rather than volume that is effectively " trapped " inside the crank. But I believe a change in total volume, that moves the case Helmholtz frequency , has more influence.The total case volume determines the frequency of the Helmholtz resonance, which has to fit the desired engine rpm.
But if not all parts of that total volume are in open communication with each other, those parts that have only a narrow connection act as pneumatic dampers,
which can considerably attenuate the amplitude of the Helmholtz resonance. So try to avoid nooks and crannies.

[wobbly]

Sadly the balloon analogy is fatally flawed by physics. At TPO the Blowdown pressure exceeds the case pressure created by the piston dropping.
This is how stagger works - the Blowdown pressure across the port that opens first , reverses the initial flow down the duct.
What pulls mixture into the cylinder , in a race engine is solely the increasing depression created by the diffuser action , maxing out around BDC if done correctly.
Only a weed eater uses piston compression of the case to push flow into the ducts.

Edit : The last 250GP season was won by Aoyama on a semi works Honda RS250 run by the Scot team in 2009.
He won the title pretty easily , with poles and lap records as well.
Sure , the Aprilia riders didnt do themselves any favours by stealing points off each other , but the HRC was faster , more often than not.
Would seem that the geniuses at the factory tuned Jans jewel to a standstill by 2009.

Edit - Spelt balloon wrong - in case ballon was fuckoff in Belgian or something.

Edit - I dont think you can enlargen a small end eye , as the case hardened surface must be a minimum of 0.5mm deep for rollers to run on - dont know if re case hardening can be done a second time.

[Grumph]

Sadly the ballon analogy is fatally flawed by physics. At TPO the Blowdown pressure exceeds the case pressure created by the piston dropping.
This is how stagger works - the Blowdown pressure across the port that opens first , reverses the initial flow down the duct.
What pulls mixture into the cylinder , in a race engine is solely the increasing depression created by the diffuser action , maxing out around BDC if done correctly.
Only a weed eater uses piston compression of the case to push flow into the ducts.


Okay, i have a question leading on from this. Lets say i have a piston port cylinder - basic 3 port layout -with very poor transfers. Small cross sectional area - and no room to enlarge them. What would happen if I cut finger transfers - like TD1C auxiliaries - with enough stagger to bleed off blowdown pressure at the crucial time.
Could this be used to encourage better flow volume from the main transfers ? Given of course a suitable pipe.

[wobbly]

Grumph , very hard to predict with so little info , sufice to say that in the 3 port ( transfers ) 100cc screamer kart engines the best layout was soon dicovered that opening the boost port
well before the mains gave the best power.
In your case maybe the effect of bleeding down the pressure differential at TPO ( added to the extra transfer STA ) would prove useful - who knows , its a fuking 2T so they love proving us wrong
even when the logic is perfectly valid.

[Grumph]

Thanks Wob. Re lack of info - I'd doubt if anyone's bothered to collect the data and put it into Enginemod for a 197 Villiers.....and i'd be very surprised if anyone ever does.
Cutting finger transfers is something I've been contemplating for some time. One day it will live again.

[SwePatrick]

Sadly the balloon analogy is fatally flawed by physics. At TPO the Blowdown pressure exceeds the case pressure created by the piston dropping.
This is how stagger works - the Blowdown pressure across the port that opens first , reverses the initial flow down the duct.
What pulls mixture into the cylinder , in a race engine is solely the increasing depression created by the diffuser action , maxing out around BDC if done correctly.
Only a weed eater uses piston compression of the case to push flow into the ducts.


Yes ofcourse, i just use that balloon term to simplify it for people that don´t understand that the crankhouse need to be designed different from the intakesystem.
Flow behaves much different.

[jamathi]

Sadly the balloon analogy is fatally flawed by physics. At TPO the Blowdown pressure exceeds the case pressure created by the piston dropping.
This is how stagger works - the Blowdown pressure across the port that opens first , reverses the initial flow down the duct.
What pulls mixture into the cylinder , in a race engine is solely the increasing depression created by the diffuser action , maxing out around BDC if done correctly.
Only a weed eater uses piston compression of the case to push flow into the ducts.

Edit : The last 250GP season was won by Aoyama on a semi works Honda RS250 run by the Scot team in 2009.
He won the title pretty easily , with poles and lap records as well.
Sure , the Aprilia riders didnt do themselves any favours by stealing points off each other , but the HRC was faster , more often than not.
Would seem that the geniuses at the factory tuned Jans jewel to a standstill by 2009.

Edit - Spelt balloon wrong - in case ballon was fuckoff in Belgian or something.

Edit - I dont think you can enlargen a small end eye , as the case hardened surface must be a minimum of 0.5mm deep for rollers to run on - dont know if re case hardening can be done a second time.

They may have reduced the crankcase volume on the 250 as well.
It did'nt help that Simoncelli broke his wrist one week before the first race.
And bautista had too many crashes, he still does the same...throwing away world championships....
The Scott-Honda was fast because they finally fitted the updates Honda had sent them during some years....
A friend of mine tested all this on his dyno! 98HP

[husaberg]

Thanks Husa, are you linking me to Ken or is there something buried in there? I did not have a proper look, however did not find anything of relevance right away.

I was quoting ken, to flush him out. That post was the first one that came up under his user name.
Ken started Strike products
http://www.strikeproducts.com.au/
He's an Aussie, but hey no ones perfect.

Sorry dude i thought you were talking piston not conrod.......

[yatasaki]

Thanks Wob. Re lack of info - I'd doubt if anyone's bothered to collect the data and put it into Enginemod for a 197 Villiers.....and i'd be very surprised if anyone ever does.
Cutting finger transfers is something I've been contemplating for some time. One day it will live again.
Each pair od fingers (2 pairs) spreads powerband for 1000 revs earlier in our buckets without affecting max power or overrev.

[crbbt]

They may have reduced the crankcase volume on the 250 as well.
It did'nt help that Simoncelli broke his wrist one week before the first race.
And bautista had too many crashes, he still does the same...throwing away world championships....
The Scott-Honda was fast because they finally fitted the updates Honda had sent them during some years....
A friend of mine tested all this on his dyno! 98HP

I am under the impression that the RSA/RWS 250 had 120hp?

Not sure where I got this number from however but guessing that was at the sprocket and not the wheel?

[F5 Dave]

Mine makes 140.

But it has 2 Ryger barrels on it.

Send money to. . .

[jamathi]

I am under the impression that the RSA/RWS 250 had 120hp?

Not sure where I got this number from however but guessing that was at the sprocket and not the wheel?

Cylinder tests at Aprilia were always done with a single cylinder engine.
We got 53,9HP
twin cylinder engines were never dyno-tested.
So at most it could have given 107HP....

[Niels Abildgaard]

Cylinder tests at Aprilia were always done with a single cylinder engine.
We got 53,9HP
twin cylinder engines were never dyno-tested.
So at most it could have given 107HP....

Was it measured on end of crankshaft or chain sprocket shaft and what was rpm?

[crbbt]

thanks for the correction! :niceone:

[husaberg]

Was it measured on end of crankshaft or chain sprocket shaft and what was rpm?

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[Niels Abildgaard]

Thank You for numbers but the photo does not look like a world beating dyno exercise?

[Frits Overmars]

Thank You for numbers but the photo does not look like a world beating dyno exercise?Well spotted Niels. The photo shows Jan Thiel's Aprilia flowbench test setup.

[husaberg]

Well spotted Niels. The photo shows Jan Thiel's Aprilia flowbench test setup.

Bugger, i knew it was the flow rig but it assumed it served as the mule engine as well.
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looking back through your posts its written any times that the Aprilia's outputs were always measured at the gearbox shaft.



Tyre pressure? Tyre type? Haufen, you do not seriously think that you can develop an engine to the required level by measuring rear wheel power, do you?
Tyre rolling losses are dependent on tyre deformation which is dependent on tyre pressure; those rolling losses heat up the tyre, which changes its pressure and the rolling resistance during the dyno run. Need I go on?

The RSA power was measured at the gearbox exit shaft, as has been mentioned repeatedly. The data-example I posted above is not from a 54 hp dyno run but from a different run, which by the way was not far short of 54 hp either.
I do not intend to start a language course of Italian technical abbreviations here, but anyone with a bit of two-stroke background should be able to deduce by the numbers what they are referring to.

The ambient factors were 27°C and 1013 mbar. Initially the ambient temperature was kept at the standardized 20°C, but in order to bring the circumstances more in line with the average circuit conditions it was later raised to 27°C. And because of the constant ambient factors there was no further correction required.
Anyway, most correcting algorithms are useless if not downright misleading when high-performance two-strokes are involved.


I assume inside cell dyno photos were frowned upon so i only have these
349209349211

i did have this below from Frits one but i am not sure what it was from.

349208
this looks to be off the crankshaft

Okay Jan says Honda...

[jamathi]

Was it measured on end of crankshaft or chain sprocket shaft and what was rpm?

Chain sprocket shaft.
Max torque at 12250
Max power at 13000

Measuring power at the crankshaft is very impractical....

[jamathi]

Bugger, i knew it was the flow rig but it assumed it served as the mule engine as well.
349205349207
looking back through your posts its written any times that the Aprilis outputs were always measured at the gearbox shaft.





I assume inside cell dyno photos were frowned upon so i only have these
349209349211

i did have this below from Frits one but i am not sure what it was from.

349208
this looks to be off the crankshaft

Not from Aprilia... This is from Honda!

[Niels Abildgaard]

Chain sprocket shaft.
Max torque at 12250
Max power at 13000

Measuring power at the crankshaft is very impractical....

Thank You for confirming my instincts.
Having more than the absolute minimum metal spinning at 15000rpm is asking for unnessecary trouble.
What reduction ratio /gear step did You use?

[Haufen]

i did have this below from Frits one but i am not sure what it was from.

349208
this looks to be off the crankshaft

Okay Jan says Honda...

This is from SAE paper 2004-01-3561 - Validation of a Computer Simulation of a High Performance Two-Stroke Motorcycle Racing Engine by Fleck et. al (QUB). They use a Honda RS125 engine and fuel injection.

[wobbly]

Yes the sectional pipe was used at QUB and then was given to Canterbury Uni , where it was used in several Phd theses I supervised.
The kit was offerred to me a couple of years ago , but I didnt think I would ever use it , now EngMod is so good - i think it was dumped.

My engine dyno has a ratio drop from a TM crank to the inertia wheel of 4.3 - this replicates the acceleration rate of a kart on track in 6th gear.
The disc is 425mm dia 100mm wide, with added inertia from a Toyota 4AGE auto starter flex plate and ring gear with 106 teeth used by the ecu hall effect pickup.

[Muhr]

I have this if anyone ever needs it

[41juergen]

How do I need to change the pipe temps in EngMot when running a stainless pipe? I use Wob's recomendation for the carbon steel pipes with approx. 325 °C at the lower end up th 425°C at max power and 450°C for overrev...

[Haufen]

where it was used in several Phd theses I supervised.

If you supervised PhD theses, does that mean you hold a PhD, too? Are these theses - or yours - publicly available? Or maybe some of the papers which had been published at the time? Interesting reading is always welcome.

[Vannik]

How do I need to change the pipe temps in EngMot when running a stainless pipe? I use Wob's recomendation for the carbon steel pipes with approx. 325 °C at the lower end up th 425°C at max power and 450°C for overrev...

Based on the dyno curves Frits posted:

1. At start of the powerband the stainless pipe is shifted 250rpm to the right
2. At max power the stainless pipe is shifted 500rpm to the right
3. At 1000rpm above max power rpm the stainless and mild steel pipes have same value.

I suggest you experiment with the prescribed temperatures to match this unless someone has a better idea or better data.

[wobbly]

Haufen , as Neels would say im a degree short of a Doc - only a Masters.
I have no idea what the setup is for external access to theses , I of course had mine and the supervised ones on old hard drives , but I will ask what is needed to get access
thru the Uni library.

[Muhr]

How do I need to change the pipe temps in EngMot when running a stainless pipe? I use Wob's recomendation for the carbon steel pipes with approx. 325 °C at the lower end up th 425°C at max power and 450°C for overrev...

Hi we have seen very little difference in material but a significant difference in thickness when we tested.
Below is with stainless steel 0.8mm 125cc. (I spray it step by step from 13000 therefore this exhaust temp)

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[wobbly]

I dont get what you are saying there Muhr , stainless is illegal in KZ anyway.
And your water temp is way too hot , as is the egt - no one could run anything like those temps on legal fuel ( 110 yes ) , plus are you are using the tiny 5mm threaded probes that read way high as they
are too short.
The R1 pipe was designed to be run at 640*C in the header , with the probe tip on the centerline , as this is the practical deto limited temp for the fastest team engines on CIK 100.

[Muhr]

I dont get what you are saying there Muhr , stainless is illegal in KZ anyway.
And your water temp is way too hot , as is the egt - no one could run anything like those temps on legal fuel ( 110 yes ) , plus are you are using the tiny 5mm threaded probes that read way high as they
are too short.
The R1 pipe was designed to be run at 640*C in the header , with the probe tip on the centerline , as this is the practical deto limited temp for the fastest team engines on CIK 100.

I would say that:
Exhaust
Ignition system
Carburettor
Powerjet / solinoid
Compression ratio
And the engine itself
would be illegal in kz.
The only thing that would meet the regulations would be the fuel.
jokes aside it is not a kz and we run with electronic powerjet with ignition every third revolution at throttle release, which pushes up EGT.
As for the sensor, we use below.
The image of the exhaust refers to the one in stainless steel.
We hope to be able to find a way to bring down the water temp with more coolers.

[41juergen]

I would say that:
Exhaust
Ignition system
Carburettor
Powerjet / solinoid
Compression ratio
And the engine itself
would be illegal in kz.
The only thing that would meet the regulations would be the fuel.
jokes aside it is not a kz and we run with electronic powerjet with ignition every third revolution at throttle release, which pushes up EGT.
As for the sensor, we use below.
The image of the exhaust refers to the one in stainless steel.
We hope to be able to find a way to bring down the water temp with more coolers.

Wob, what diameter of the temp sensor do you run? I use typically the NiCr-Ni 1,5mm thermocouples...

[Tim Ey]

I would say that:
electronic powerjet with ignition every third revolution at throttle release, which pushes up EGT.


Hi Muhr
I do not get it. Do you miss every third ignition or do you perform an ignition only every third revolution?
And most importantly: At which rpm / occasion do you do so? Whilst shifting down? Whilst braking?

[wobbly]

Muhr , thats what had me confused , with a C and a R1 TM KZ pipe in the picture.
The sensor is exactly what I was refering to - when used on a KZ pipe it is way too short ,so being close to the header wall it reads high, and being fully enclosed its way too slow reacting to temp change .
I use Stinger probes from EGT Industries , they are 5mm (3/16" ) diameter , but have an exposed thermo tip and can be fitted to be exactly on the header centerline.
They are the only commercial sensor I have found with a 2 year guarantee , ive used and sold literally hundreds of them for over 15 years , and never had a failure.

Electronic powerjets are normally used to compensate for the fact that carbs naturally become progressively richer over the top of the powerband.
They can be switched off completely ( most do ) or can be PWM pulsed on/off to get a more progressive fuel curve.
But some ECU can also be used to prevent a rich , unburnt mixture from cooling down the pipe on overun into corners , by using a lookup table of rpm and TPS.

[Muhr]

Hi we use powerjet to cool the piston when you get off throttle/overrev. (I have with duty cycle) then we use reduced number of sparks at high revs with closed throttle.think it is called TCT
this has been shown to create an combustion in exhaust that so far has not shown any downsides except that I was lazy when I did stinger reductions and made some in aluminum which I have done many times before. This does not work with this setup

[F5 Dave]

Question Muhr: I've never exerted that level of control over pj, but on closed throttle would be great. If it would flow. So wouldn't you have to have a pj tube at the bottom of the carb where the closed slide didn't obscure it? Can you measure effect with egt on closed with and without? Would have thought that would be a bit murky?

My egt setup 15 years ago was terrible and I abandoned it without learning anything and angry how expensive it was..

Did someone say ktm had played with suplimentary injector to do this in case or did I dream that?

[wobbly]

F5 , IMHO its impossible to tune a 2T to the edge , consistantly , without having the best power EGT from the dyno and then be able to
replicate that on the track , in changing weather.
KTM had an injector in the intake , that supplied fuel on the overun. They had trouble early on with riders who insisted on crashing down 4 gears , then dropping the clutch so the revs instantly shot past 15,000.
The injector could add fuel/oil in this case - a carb cant.
Funny I seem to have heard that scenario about the Aprilia breaking the rear RV drive shaft for the same reason.

[jamathi]

F5 , IMHO its impossible to tune a 2T to the edge , consistantly , without having the best power EGT from the dyno and then be able to
replicate that on the track , in changing weather.
KTM had an injector in the intake , that supplied fuel on the overun. They had trouble early on with riders who insisted on crashing down 4 gears , then dropping the clutch so the revs instantly shot past 15,000.
The injector could add fuel/oil in this case - a carb cant.
Funny I seem to have heard that scenario about the Aprilia breaking the rear RV drive shaft for the same reason.

The revs shot past 17000......
And one rider I particularly dislike did a complete lap at Imola with a 250:
With one broken conrod! cutting the engine nearly in 2 pieces!!!
Also destroyed the gearbox
He should have been hanged.....

[Muhr]

Question Muhr: I've never exerted that level of control over pj, but on closed throttle would be great. If it would flow. So wouldn't you have to have a pj tube at the bottom of the carb where the closed slide didn't obscure it? Can you measure effect with egt on closed with and without? Would have thought that would be a bit murky?

My egt setup 15 years ago was terrible and I abandoned it without learning anything and angry how expensive it was..

Did someone say ktm had played with suplimentary injector to do this in case or did I dream that?

Hi I use it only at high RPM, exactly how effective it is for itself or is at lower RPM with closed throttle I can not answer. probably pretty bad pretty fast as we run it on the float cup. However, you can choose to put it on the diaphragm pump and have flow at idle if you wish. (This would technically be injection if it is a problem of the rules) The function is exactly as Wob described a nozzle with pulsating solenoid that can be set from 1to100 %

[lodgernz]

Interesting
https://www.visordown.com/news/new-bikes/langen-two-stroke-gains-euro-5-certification-heres-how?fbclid=IwAR0MlVrlLRACV_PGldk3EDI08zhnKoVPBtSu_ 7EOM1vpBBHk8qJ-1PFgO7E

[TZ350]

Interesting https://www.visordown.com/news/new-bikes/langen-two-stroke-gains-euro-5-certification-heres-how?fbclid=IwAR0MlVrlLRACV_PGldk3EDI08zhnKoVPBtSu_ 7EOM1vpBBHk8qJ-1PFgO7E

349252

The article describes it as direct injection. But it is a mystery where the injectors are. More info would be interesting.

[husaberg]

349252

The article describes it as direct injection. But it is a mystery where the injectors are. More info would be interesting.
https://vinsmotors.com/?lang=en

https://www.youtube.com/watch?v=g6MxCjDgJKI&t=15s
https://www.youtube.com/watch?v=WkZexoCSPMo&t=7s

here are the cases
349253


https://worldwide.espacenet.com/patent/search/family/064270926/publication/EP3695104A1?q=pn%3DEP3695104A1

https://patentimages.storage.googleapis.com/b3/55/6b/dcfb7aedd017cf/WO2019073448A1.pdf

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[ceci]

349257349255349254349256


Important detail, the injector is delaying to facilitate the creation of the spray, if it is more advanced it will facilitate the transport delaying the formation of the drop

For that reason it is more appropriate to use the EV 14K instead of the EV14 xT


https://www.hulsenturbotuning.nl/images/stories/virtuemart/product/bosch-ev14-dimensions.jpg

[palezu]

Cast a new 50cc Hi-Power jug for this year trials.

http://i.imgur.com/OTRhgp3m.jpg (https://imgur.com/OTRhgp3)

It has duct design features I have learned from here over the years. 190* 3-part exhaust, big transfers with 131-130-128 timings (about) and transfer radial angles taken directly from Frits MB40 design drawing. The angles should be fairly accurate because sand cores were made using CAD designed boxes.

http://i.imgur.com/fE9tIDmm.jpg (https://imgur.com/fE9tIDm)

https://i.imgur.com/yL4KdPXm.jpg

Exhaust duct length is about 1.3 times bore diameter and full top side water cooling. Exit area should be 70% of entry area, left some room to enlarge it. It is small, hard to believe that it might give actually more power.

http://i.imgur.com/2j3Ronjm.jpg (https://imgur.com/2j3Ronj)

We'll see how it works in a few weeks.

[wobbly]

Duct exit should be 75% of the total Ex ports effective area that is , x cosine of the roof down angle .
And its been proven a huge number of times , going straight from EngMod to the dyno.

[philou]

On the rsa carburetor, the idle circuit takes its air in the needle jet duct?

Usually there is a hole for each.

349278

349279

[jbiplane]

My open-source Speeduino based fuel injection and ignition kit for 40...180cc engines in action.
Hope start production in quantity after intence tests and summer holydays this October.

https://youtu.be/qeMpfWMmhv4

[TZ350]

.
Alex's 2stroke stuffing adventures continue:- https://youtu.be/T0p2VWBKJ4Y ..... :niceone:

[TZ350]

.
The Fuel Injected Langen achieving Euro 5 certification is brilliant.

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Towards the end of the dyno runs you can hear it hitting a rev limiter.

With only one injector my guess is that its limited to about 11,500 max rpm. Not because the injector is to small but rather an injector big enough for high RPM is to big at Low RPM for clean throttle response.

349281
This is not "Direct Injection", direct injection is injecting directly into the cylinder after the exhaust port has closed. And the limited time available for injection in direct injection engines is what limits their performance.

At some point on the engine load curve the reed block injector must be on for nearly the full 360 deg of crank rotation. And at other points the injector will be on for a significant amount of time to achieve a homogeneous air/fuel mixture in the crankcase that is ready to be drawn up the transfers.

The air/fuel mixture in the crankcase does not go directly to the cylinder but rather has to wait its turn. On each cycle the air/fuel mixture in the transfer ducts is sufficient to replenish the cylinder and the air/fuel mixture in the crankcase merely replenishes the transfer ducts ready for the next cycle. So the Langen crankcase with its reed injection has to have a proper air/fuel mixture throughout the crankcase.

"B" port injection is not limited in this way. Ideally "B" port injection just fuels the air waiting in the B transfer ducts. The A transfers that are more prone to short circuiting out the exhaust have cleaner un-fueled air in their ducts.

It is interesting that they can achieve Euro 5 with the Langen by directly injecting into the crankcase because it is hard to see how that is much different to the way a carb feeds the crankcase. I would think that both would have air/fuel mixture short circuiting out the exhaust and to some extent back out the inlet.

There must be more to this story, I would love to know what it is.

[ceci]

.
The Fuel Injected Langen achieving Euro 5 certification is brilliant.

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Towards the end of the dyno runs you can hear it hitting a rev limiter.

With only one injector my guess is that its limited to about 11,500 max rpm. Not because the injector is to small but rather an injector big enough for high RPM is to big at Low RPM for clean throttle response.

349281
This is not "Direct Injection", direct injection is injecting directly into the cylinder after the exhaust port has closed. And the limited time available for injection in direct injection engines is what limits their performance.

At some point on the engine load curve the reed block injector must be on for nearly the full 360 deg of crank rotation. And at other points the injector will be on for a significant amount of time to achieve a homogeneous air/fuel mixture in the crankcase that is ready to be drawn up the transfers.

The air/fuel mixture in the crankcase does not go directly to the cylinder but rather has to wait its turn. On each cycle the air/fuel mixture in the transfer ducts is sufficient to replenish the cylinder and the air/fuel mixture in the crankcase merely replenishes the transfer ducts ready for the next cycle. So the Langen crankcase with its reed injection has to have a proper air/fuel mixture throughout the crankcase. "B" port injection is not limited in this way.

It is interesting that they can achieve Euro 5 with the Langen by directly injecting into the crankcase because it is hard to see how that is much different to the way a carb feeds the crankcase. I would think that both would have air/fuel mixture short circuiting out the exhaust and to some extent back out the inlet.

There must be more to this story, I would love to know what it is.


You know that's not stratified scavenging like TPI is and that it's hardly better than a carburetor.
The Euro5 not includes minority group bikes (langen only 100 units) (trial offroad ones too)

[Muhr]

what are the requirements for euro 5?

https://m.youtube.com/watch?v=RwB5_lL8wyU

[breezy]

is it me or did it sound a bit boggy when he blips the throttle..?

[ceci]

what are the requirements for euro 5?

https://m.youtube.com/watch?v=RwB5_lL8wyU

https://eur-lex.europa.eu/eli/reg/2019/129/oj?locale=en

[Muhr]

https://publications.jrc.ec.europa.eu/repository/bitstream/JRC53779/eur%20report%2023999%20en_mopeds_2009%20%282%29.pd f

Euro 5 emissions limits (petrol) CO: 1.00g/km HC: 0.10g/km NOx: 0.06g/km PM: 0.005g/km

[Flettner]

Probably the only known photo of the uniflow100 in its frame.
Other bike my daughter is sitting on is a weedeater powered bike I built for the kids.
A lifetime ago.

[husaberg]

Probably the only known photo of the uniflow100 in its frame.
Other bike my daughter is sitting on is a weedeater powered bike I built for the kids.
A lifetime ago.

only decent photo :)
349291349292

[Flettner]

The two only known crap photos of the 100cc uniflow. 😀

[Condyn]

Hello gentleman, I have been having a difficult time trying to grasp inlets. Every time I research the matter I end up diving down some other 2T rabbit hole.

The following is my understanding and should not be taken as facts. Please correct me if needed.

From what I gather, rotary valve and piston port engines need to stay within a degree range so they can start and operate at low rpm. Those two types of engines seem to respond better to a large case volume than reed engines which I pair with reed resonance requirements. Reed engines do not seem to have the same timing drawbacks as they open and close at the right time if you get it right.

Now the questions:

First, I have read that reeds can be too big. What does that mean exactly? Is this directly tied to the requirements of effectively opening a reed?

Second, on a cylinder reed engine, is adding boyesen ports as effective as piston cuts to increase intake area in an example where the STA is the same either way?

And lastly, is the pipes diffuser strong enough to open reeds at bottom dead center or does all the mix entering the scavenging column via the boost port (cylinder reed example) come from the trapped volume in the reed block as the intake port is shrouded by the piston? Or must there be a link to the case through piston cuts during this phase?

[wobbly]

Question one - reedblock too big. This can be the effective port area , and or the petal / port edge curtain area at full lift - both combine to generate the STA metric created by the fixed
port area and the continuously changing petal lift profile.
Just like Blowdown and Transfer STA , the Inlet STA should be capable of supporting the power being generated at a specific rpm.
BUT , unlike the other two , the Inlet is self compensating to some degree - that is if the curtain area is insufficient , then as airflow rises the petals can , be held open higher , for longer.

The other side of that coin is energy recovery .
Depending upon the petals 1st Mode Natural Frequency rpm ( usually lower with bigger/longer/thicker reeds ) it can be entirely possible to not
be able to get the system into resonance at a useful rpm to use the "free" effect of much less energy needed from the Intake airflow column to get the petals off the seat, and to stay open.
Another issue is that even with a very well designed and bench tested stuffer , you will always end up with the flow finally dumping thru an excessive area change .
This is the reason also that there has been of late , a tendency to reduce the area in font of the reed tip in the case - same deal with a higher energy recovery loss created by a big area change.

Second question - increasing piston cutouts or lifting the skirt always has the down side that the area presented to the incoming flow is coninuously varying , usually from too small to too big .
Whereas Boyesens are fully open all the time.

Lastly reed lift and diffusser action. The first point here is that there is no flow from the case , up thru the ducts and into the cylinder while the transfer ports are open. There is more volume in the ducts
than that delivered into the cylinder by the scavenging streams.
In all race engines I have seen on EngMod , the petals are pulled off their seats close to TPC by the case going negative near BDC and if the Intake is tuned , the column behind the petals has a resonant wave creating
a positive ratio as well.
Cylinder reed engines will feed the boost port duct via the relatively huge volume surrounding the reedblock , the connection to the case is irrelevant.

[Condyn]

Thank you for the response. I will have to let that resonate for a bit!

[Muhr]

If it would flow. So wouldn't you have to have a pj tube at the bottom of the carb where the closed slide didn't obscure it?


Took a picture today when I had it in front of me.

[wobbly]

Here's a mod I have done on many Yamaha racebikes with the electronic solenoid PJ - move the PJ to the top of the bellmouth and shorten the dump tube so it
only protrudes around 15mm into the bore . I cut the tube end at 45* facing the reeds as this atomizes the fuel stream much better than the stock small hole does.
The slide has to be well past the tube end for flow to begin , having a low down tube richens the fuel curve way too much in the midrange.

The only other way is to use a truth table in the ecu to switch the flow depending upon TPS and rpm , but this is problematic to tune , causing jerking response on part throttle , mid corner.
Cutting the tube short works on Lectrons as well , when having to use large PJ flow ( 50 + ) to get the top end tune correct without shagging the midrange jetting.

[TZ350]

.
Alex is making progress with his 2Stroke Stuffing supercharged 50. https://youtu.be/_8xbYnXuI1A

[F5 Dave]

Took a picture today when I had it in front of me.
Ahh I see, it is a lot lower than I thought it would be with quite a lot of slide cutout showing.

So if you could control 2, a short one in from the side real low down that only works high revs closed throttle and another as Wob described.

[Muhr]

The only other way is to use a truth table in the ecu to switch the flow depending upon TPS and rpm , but this is problematic to tune , causing jerking response on part throttle

Thanks for the tip Wobbly!


Ahh I see, it is a lot lower than I thought it would be with quite a lot of slide cutout showing.

So if you could control 2, a short one in from the side real low down that only works high revs closed throttle and another as Wob described.

Yes definitely could be a way forward !!
the goal so far has been to achieve a good piston cooling with the help of PJ, which it looks like we have succeeded with.
The reason for this is that we have a fuel with limitations (98/90). the idea is to now start pushing the boundaries and see if we can go further with this approach than if we had a traditional carburetor setup

[wobbly]

My first reaction was that if you want flow at high rpm , closed throttle , the put the PJ tube on the other side of the slide.
Plenty of vacuum on closed throttle to pull fuel thru.
But why then did KTM feel the need to use an injector for the same thing ?

[F5 Dave]

Trick factor? Additional control options like adding fuel if knock sensor goes off? Would love to know.


But yes pj on other side of slide sounds better idea than mine (as usual) . Would have been useful on an old air-cooled bike of mine that was fine on kart tracks but would nip on hairpin at Ruapuna unless jetted so rich on pilot that it stumbled on reapplication. Think I'd cured the float feed as well.

[Muhr]

My first reaction was that if you want flow at high rpm , closed throttle , the put the PJ tube on the other side of the slide.
Plenty of vacuum on closed throttle to pull fuel thru.


Yes it might be a better solution.
My theory was that I wanted a pressure difference between the air bleed hole and the spray hole. for increased function at lower airflow?




bit of topic but cool slow motion pictures of a "carburetor" at work
https://m.youtube.com/watch?v=toVfvRhWbj8

[Pursang]

Matt Hudson from The Workshop YouTube channel is doing some development work on a multi-cylinder 2 stroke based on the Hossack engine.

https://www.youtube.com/watch?v=VRzSpSYQ2EU

Good description of prototype design and analysis of components using Solidworks.
5 videos so far in the series.

Cheers, Daryl.

[Tim Ey]

Yes it might be a better solution.
My theory was that I wanted a pressure difference between the air bleed hole and the spray hole. for increased function at lower airflow?




bit of topic but cool slow motion pictures of a "carburetor" at work
https://m.youtube.com/watch?v=toVfvRhWbj8
Huh? I never saw that air bleed hole before on a powerjet?!
How does it change its behaviour?

KTMs injector: Probably their bike turned out too light for the class? :-D

[Muhr]

Huh? I never saw that air bleed hole before on a powerjet?!
How does it change its behaviour?

KTMs injector: Probably their bike turned out too light for the class? :-D

Emulsion of the fuel before it leaves the tube was my thought
which should also widen the RPM range as the air hole (s) are static while the fuel feed will be dynamic to a greater extent. There are many who call a power needle a power jet.
As I see it a power jet has jets and emulsion tubes while the power needle is a needle and a tube. But I could be wrong

Do not know what the rules looked like in gp racing but if it was ok to have an injection / overpressure system you would probably have it, as the possibilities are endless

[lohring]

Matt Hudson from The Workshop YouTube channel is doing some development work on a multi-cylinder 2 stroke based on the Hossack engine.

https://www.youtube.com/watch?v=VRzSpSYQ2EU

Good description of prototype design and analysis of components using Solidworks.
5 videos so far in the series.

Cheers, Daryl.

I'm not sure why people keep trying to redesign the old round piston design. The issue in IC engines is the seal. Steam engine builders settled on the standard round piston because it could be produced accurately enough with simple machines to get a good seal. A century or so of experimenting hasn't improved on it. The Wankel engine was the latest attempt at sealing a different shape. Lots of alternate designs have been successful in hydraulic pumps, but the round piston still dominates. Lots of oil at lower temperatures make the problem easier.

Lohring Miller

[JanBros]

Matt Hudson from The Workshop YouTube channel is doing some development work on a multi-cylinder 2 stroke based on the Hossack engine.

https://www.youtube.com/watch?v=VRzSpSYQ2EU

Good description of prototype design and analysis of components using Solidworks.
5 videos so far in the series.

Cheers, Daryl.

I wonder why he thinks that the transfer port still open after the exhaust has closed is "gold" ? the piston is already going back up so not much suction, plus the exhaust is closed so you can not benefit from presurising the cylinder with mixture drawn in the expansion pipe.

[Pursang]

I'm not sure why people keep trying to redesign the old round piston design. The issue in IC engines is the seal. Steam engine builders settled on the standard round piston because it could be produced accurately enough with simple machines to get a good seal. A century or so of experimenting hasn't improved on it. The Wankel engine was the latest attempt at sealing a different shape. Lots of alternate designs have been successful in hydraulic pumps, but the round piston still dominates. Lots of oil at lower temperatures make the problem easier.


The earliest steam engines relied on cannon manufacturers for their technology. (The earliest cannon manufacturers relied on tree trunks!)
The square bore provides an extremely compact package for a multi cylinder engine.
The "square" piston eliminates the gudgeon assy. (Weight, parts, precision machining, lubrication requirements & a potential failure point)
Thanks to years of Wankel development the technology & materials to provide durable and efficient lip sealing are now available.


I wonder why he thinks that the transfer port still open after the exhaust has closed is "gold" ? the piston is already going back up so not much suction, plus the exhaust is closed so you can not benefit from presurising the cylinder with mixture drawn in the expansion pipe.

The 'design exercise' is not for a racing engine.
Having an extended time period available for direct F.I. (Or Air/fuel injection) is useful.
For a low(er) performance application, loss of mixture back to the transfer is way better than out the exhaust.

IMHO, the ability to provide pressurised transfer via an externally pressurised common multi-cylinder cranckcase will allow efficiency within the smallest possible dimensions and simplest construction. (Not sure if Matt is considering that option, the individual reed blocks suggest not... yet).

Cheers, Daryl.

[Frits Overmars]

The "square" piston eliminates the gudgeon assy. (Weight, parts, precision machining, lubrication requirements & a potential failure point)
Thanks to years of Wankel development the technology & materials to provide durable and efficient lip sealing are now available.Eliminating the gudgeon assy can just as well be achieved in a round cylinder bore; in fact it has been done in several air compressors.
It would also make sealing a whole lot simpler; all you'd need is one spherical piston ring.
One drawback: it's not suitable for piston-controlled exhaust ports.
349310

[JanBros]

The 'design exercise' is not for a racing engine.


then why would he be talking about getting the weight of the P-rod down to 100grams to rev it's nuts off ?

[wobbly]

The hole in the PJ tube is exactly the same as a normal idle or main air corrector . Air mass passing thru the venturi continues to increase past the
peak of BSFC @ max torque , thus the fuel curve goes progressively richer.
An air corrector may help atomization as a by product , but its designed function is to bleed in increasing amounts of air to change the fuel
curve closer to ideal as the power drops over the top of the pipe.
A Lectron has no air bleed system , and it atomizes the fuel droplets way better than any emulsion tubed carb.

[Vannik]

A Lectron has no air bleed system , and it atomizes the fuel droplets way better than any emulsion tubed carb.

After watching the see through carb video something struck me - the unemulsified fuel traveled quite deep into the venturi and the emulsified and evaporated very good. A Lectron must do something similar but even better, the fuel also shoots up into the venturi and is aided by the adhesion to the rear of the needle and is partially protected by the same needle. So it penetrates quite far before being carried away by the air stream. This should give superior atomization and vaporization combined with a more homogeneous mixture distribution early on in the air stream. Should be especially superior in very short intakes.

[Pursang]

then why would he be talking about getting the weight of the P-rod down to 100grams to rev it's nuts off ?

He says an awful lot of things! I often disagree with some of his pronouncements.

I think some of the weight thing was just demonstrating the ability of the engineering software to design and test for a particular operating condition.
The other part was explaining the concept of "margin of safety".

I'm not here to defend or apologise for him. I do think the exercise is interesting.
Putting it all up online, showing the process and the progress or otherwise is brave, same for Neil, Ken & Alex's projects)

Then again...perhaps he is considering taking Alex's challenge to build the WMPTSE ??

Cheers Daryl

[philou]

Do you have more information on dellorto VHTC carburettors?

Does it use specific jet, needle and needle jet or common to other model?

Is the jet in a plenum chamber?

[lohring]

Even after a lot of work, the Wankel was a failure, in part because of seal issues. I loved the idea, though, and own a model Wankel that I flew on an RC airplane. I also respect the attempt to show the steps to improve the old idea. However, didn't Honda unsuccessfully experiment with oval pistons? See https://global.honda/heritage/episodes/1979pistonengine.html

Lohring Miller

[Frits Overmars]

Even after a lot of work, the Wankel was a failure, in part because of seal issues. I loved the idea, though, and own a model Wankel that I flew on an RC airplane. I also respect the attempt to show the steps to improve the old idea. However, didn't Honda unsuccessfully experiment with oval pistons? See https://global.honda/heritage/episodes/1979pistonengine.htmlThat is a nice read Lohring; here's a quote I particularly like:
World GP racing regulations limit the number of cylinders to four. Accordingly, for a four-stroke engine to be as powerful as a two-stroke unit, it has to achieve twice its normal rpm. To achieve that, the team had to enhance the intake efficiency and design a valve system with higher resistance to friction and heat buildup at high revolutions. Given these conditions, the idea was born to double the number of valves to eight. As they examined the potential valve positions in the context of their four-stroke engine layout, the team came up with an idea of changing the piston's shape from a circle to an oval.Now allow me to tell that part of the story the way I remember it.
Honda realised that they would have to build an eight-cylinder four-stroke if they would have any chance at all to beat the four-cylinder two-strokes. But eight-cylinder engines were forbidden... "What if we remove the cylinder walls between adjacent pistons? Then we'd have a V-four instead of a V-eight!
It may not be in the spirit of the rules but it does follow the letter of the rules".
349314
Designing, building and trying to race the NR500 (I wonder who was the first to call it the NeverReady?) turned out to be an expensive way of discovering that two-strokes are not that easily beaten. It took Honda R&D a couple of years and more than a couple of Yen to see the light and start building excellent two-stroke racers.
In-between they went rotary as well:
349313 349311 349312

[katinas]

Interesting that for Daytona race Honda prepared big bore versions, NR 600 cc for the race and later with two stroke NS 550 cc. But F. Spencer use NS 550 only for practice and used 500 cc for the race.
Other very interesting Honda engine was 250 cc tandem for CR (RC) 250 prototype, or idea of oval piston for two stroke.

[pete376403]

Interesting that for Daytona race Honda prepared big bore versions, NR 600 cc for the race and later with two stroke NS 550 cc. But F. Spencer use NS 550 only for practice and used 500 cc for the race.
Other very interesting Honda engine was 250 cc tandem for CR (RC) 250 prototype, or idea of oval piston for two stroke.

Honda may have tried too many things at once - 16" wheels, monocoque frame making it hard to work on, probably other things as well.

[husaberg]

Interesting that for Daytona race Honda prepared big bore versions, NR 600 cc for the race and later with two stroke NS 550 cc. But F. Spencer use NS 550 only for practice and used 500 cc for the race.
Other very interesting Honda engine was 250 cc tandem for CR (RC) 250 prototype, or idea of oval piston for two-stroke.

They also built a turbo 250 oval piston for Freddy to try out couldn't convince the rule-makers to change the rules to allow turbos. Although Freddie tried it in practice.
https://pbs.twimg.com/media/Dk93sxQW0AA3Lys?format=jpg&name=small349321349320349322349319
the line drawing most say was for the round piston twin but note the gear driven cams
They then built a conventional round piston 250 kind of based on the VT250 with twin turbos that made over 100hp. Some say 150





Honda's web site


The NR250 Turbo was half an NR500 with twin turbochargers one for each cylinder and PCM-FI injection.
It was to replace the NR500 for Grand Prix racing. In 1983, it made 153 PS (150 HP) at 18500 RPM and 2.0 Bar pressure. Due to turbo lag (and rules changes) it never made it to the track.



The VT250RT made 150 PS (148 HP) at 11500 RPM and weighed approx. 375 lbs.
Honda found the VT250RT turbo came on boost at 7500 RPM and accelerated at twice the rate of the NS500.
Honda decided the power band was way too peaky for the rider to handle, de-tuned the engine to 90 PS (89 HP) at 11500 and wanted to put it into the 1985 Japanese model catalog as the VT250FTC, but was denied permission by the government.
Honda through a heap of graduate students at the Nr project to try new things composites USD forks side radiator small wheels, slipper clutches, carbon brakes, separate spring forks carbon frames etc.
Most were used later on the V fours.
349323

[lohring]

Super or turbo charging is the only hope a four stroke has to develop the same power as a simple tuned pipe two stroke of the same displacement. You either need double the BMEP or double the RPM. Increased intake pressure lets you do both to some degree. You then get a much more complicated and expensive engine. Racing bodies changed the rules to nearly double the allowed displacement for four strokes. You still get a heavier, more complex engine. Even Honda learned this.

Lohring Miller

[TZ350]

<iframe width="560" height="315" src="https://www.youtube.com/embed/RxjD_wLvwrE" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

2Stroke Stuffing is making progress with basic testing of the 24/7 idea. He has a normally aspirated 50cc two stroke with two carbs. A small carb/reed valve setup to get the engine up to speed. And then when its on the pipe he opens a second much larger carb that is completely open to the crank case. No reed or rotary valve. Totally open 24/7 and relying on resonance in the inlet tract.

The experiment showed promise and with some refinement should run well. It will be interesting to see if there is a power advantage.

The first time I came across this idea was when I read about a dyno test of a rotary valve two stroke single. Where at full power the rotary valve sized in the open position. The engine kept making full power until the throttle was closed and the revs drop'd. Later I saw Frits talking about the 24/7 concept. Where a pair of reeds were used to get the engine up to speed then when it was on the pipe the reeds were held open 24/7.



336062

I think it's possible that a conventional reed starts behaving like a 24/7 inlet when the engine frequency rises above the reed's natural frequency,
but it will still offer a lot of flow resistance. Better swing the reeds out of the way altogether.

[Frits Overmars]

The video tells it all: blowback from the 24/7 carburetor whenever its throttle is opened, wich is only to be expected considering the Helmholtz resonance frequency there: conventional crankcase volume, big carb diameter, short inlet tract, low revs and infinite inlet timing.
Revving the engine higher before opening the 24/7 carb, like Alex is proposing, will help, but the best (and simplest) solution is to increase the inlet tract length.

[husaberg]

The video tells it all: blowback from the 24/7 carburetor whenever its throttle is opened, wich is only to be expected considering the Helmholtz resonance frequency there: conventional crankcase volume, big carb diameter, short inlet tract, low revs and infinite inlet timing.
Revving the engine higher before opening the 24/7 carb, like Alex is proposing, will help, but the best (and simplest) solution is to increase the inlet tract length.

Hi Frits, wouldn't it be more effective to make the bellmouth longer or better still variable?

https://www.youtube.com/watch?v=NMY_In9yen4&t=6s


https://i.imgur.com/QqXkzwu.mp4
or the Mazda 787B
https://hips.hearstapps.com/hmg-prod.s3.amazonaws.com/images/787b-intake-1617895794.gif



seen this today make your own bellmouths the easiest way
https://imgur.com/QqXkzwu

https://imgur.com/QqXkzwu

[Frits Overmars]

Hi Frits, wouldn't it be more effective to make the bellmouth longer or better still variable?It might be, in combination with fuel injection. But when using a carburetor, as Alex is doing in his latest 2Stroke Stuffing video ( https://www.youtube.com/watch?v=RxjD_wLvwrE (https://www.youtube.com/watch?v=RxjD_wLvwrE&t=3s) ) a bellmouth is definitely a bad idea because it would put the carb somewhere in the middle of the inlet tract, instead of at the very beginning, where it ought to be.
'Somewhere in the middle' there is a real risk of pulsating flow going to and fro over the needle jet, picking up fuel each time, forming an ultra-rich mixture that may drown the engine.


seen this today make your own bellmouths the easiest way
https://imgur.com/QqXkzwu
https://imgur.com/QqXkzwuThe easiest way to make a bellmouth maybe, but not a good way. An efficient bellmouth has a properly radiused entry, guiding air from all directions into the inlet tract.
349331

[husaberg]

It might be, in combination with fuel injection. But when using a carburetor, as Alex is doing in his latest 2Stroke Stuffing video ( https://www.youtube.com/watch?v=RxjD_wLvwrE (https://www.youtube.com/watch?v=RxjD_wLvwrE&t=3s) ) a bellmouth is definitely a bad idea because it would put the carb somewhere in the middle of the inlet tract, instead of at the very beginning, where it ought to be.
'Somewhere in the middle' there is a real risk of pulsating flow going to and fro over the needle jet, picking up fuel each time, forming an ultra-rich mixture that may drown the engine.

The easiest way to make a bellmouth maybe, but not a good way. An efficient bellmouth has a properly radiused entry, guiding air from all directions into the inlet tract.
349331

Three times past the main jet.........

[speedpro]

3D printed for my 125

[speedpro]

Alex is planning a simple injection system on the 24/7 port. The carb was just a test as he just had to give it a try.

[F5 Dave]

Have we seen in the cases? Looks like trying to go through the crank webs?.?

[SwePatrick]

Yes, there are videos that shows it.
And no, not between the webs.

[ken seeber]

Well, the DCI (Direct Cylinder Induction) thing is still happening. See earlier posts #35387 & 35479 for a bit of background.


349378

[Muhr]

Has anyone thought about the engine's internal inertia in connection with gear compensation when running the dyno. This is a shortcoming when one is interested in getting an idea of how an engine performs against an engine with a different gear ratio from the crankshaft. As far as I have seen, a dyno only compensates for the gear ratio but not for the increased power consumption to accelerate the engine's own inertia at a higher gear ratio. This is usually visible when running a all gear pull. Wondering if there would be a good way to generalize this?

[ken seeber]

Took a little vid of the engine running at lower speeds and no load. Does show a depression in DCI passages.

https://studio.youtube.com/video/D6EX3x8yptU/edit

[SwePatrick]

Has anyone thought about the engine's internal inertia in connection with gear compensation when running the dyno. This is a shortcoming when one is interested in getting an idea of how an engine performs against an engine with a different gear ratio from the crankshaft. As far as I have seen, a dyno only compensates for the gear ratio but not for the increased power consumption to accelerate the engine's own inertia at a higher gear ratio. This is usually visible when running a all gear pull. Wondering if there would be a good way to generalize this?

Sportdevices can do both, but.. generally just uninterestiing and you might have got it backwards?
The faster the engine accelerates the more inertialosses, and by this it means that in higher gears it doesn´t need to compensate as much as in lower gears.
Just dyno it for torque and power in the gear closest to 1:1 ratio, and use sweep through gears just to verify the setup works.

Just to clarify: in static dynopulls there are alomost no compensation at all, as it takes very little power to keep engine rotating at the same speed.
And sweeping pulls in dyno(opposite to static) takes more power the faster you accelerate the engine, so the biggest compensation is in LOWER gears.
Dyno program adds power in lower gears to make power equal as in higher gears if setup correct.

[Muhr]

Sportdevices can do both, but.. generally just uninterestiing and you might have got it backwards?
The faster the engine accelerates the more inertialosses, and by this it means that in higher gears it doesn´t need to compensate as much as in lower gears.
Just dyno it for torque and power in the gear closest to 1:1 ratio, and use sweep through gears just to verify the setup works.

Just to clarify: in static dynopulls there are alomost no compensation at all, as it takes very little power to keep engine rotating at the same speed.
And sweeping pulls in dyno(opposite to static) takes more power the faster you accelerate the engine, so the biggest compensation is in LOWER gears.
Dyno program adds power in lower gears to make power equal as in higher gears if setup correct.

To clarify I see 8: 1 higher ratio than 1: 1 if you misunderstood / wanted to misunderstand. What do you usually do when you run 1: 1? Sometimes, it is not possible to get close to previous references and then you start to think about these question.

[Frits Overmars]

Has anyone thought about the engine's internal inertia in connection with gear compensation when running the dyno. This is a shortcoming when one is interested in getting an idea of how an engine performs against an engine with a different gear ratio from the crankshaft.In static power measurements the engine's internal inertia does not play a role as there is no rpm variation during the measuring phases.
In dynamic measurements the power absorbed by the internal inertia will not show up at the measured power graph which is usually a good thing because most of the time you will want to see the nett power delivered by the engine.
If you really want to know the internal inertia, you can deduce it by calculating and adding the inertias of all rotating engine parts, taking their rpm ratios in relation the crankshaft rpm into account.

Some say a coast-down run will reveal the internal engine losses but this won't tell you much about the inertial losses because there are also pumping losses, oil churning losses and friction losses, most of the latter being a percentage of the engine power sent through the transmission.
However, during a coast-down the amount of power sent through the transmission is much lower than the power delivered by a firing engine, so it is not realistic to add the measured coast-down power to the measured power of the firing engine and present the sum total as crankshaft power, as is often done.

Comparing engine measurements that were done with different transmission ratios from engine to dyno made me develop the Power Range concept that I introduced in this forum some time ago (in 2013 if memory serves). Today the Power Range option is also incorporated in Vanniks EngMod2T software.

[Muhr]

In static power measurements the engine's internal inertia does not play a role as there is no rpm variation during the measuring phases.
In dynamic measurements the power absorbed by the internal inertia will not show up at the measured power graph which is usually a good thing because most of the time you will want to see the nett power delivered by the engine.
If you really want to know the internal inertia, you can deduce it by calculating and adding the inertias of all rotating engine parts, taking their rpm ratios in relation the crankshaft rpm into account.

Some say a coast-down run will reveal the internal engine losses but this won't tell you much about the inertial losses because there are also pumping losses, oil churning losses and friction losses, most of the latter being a percentage of the engine power sent through the transmission.
However, during a coast-down the amount of power sent through the transmission is much lower than the power delivered by a firing engine, so it is not realistic to add the measured coast-down power to the measured power of the firing engine and present the sum total as crankshaft power, as is often done.

Comparing engine measurements that were done with different transmission ratios from engine to dyno made me develop the Power Range concept that I introduced in this forum some time ago (in 2013 if memory serves). Today the Power Range option is also incorporated in Vanniks EngMod2T software.


Thanks Frits!
As always, you have thought about most things! I'll take a look at your concept and see what I can learn.

[wobbly]

You have a couple of competing variables at play with " inertia " type testing, but some also affect a steady state power test as well.
Thus you need to have a total reduction ratio such that the time taken for the test , will generate realsitic pipe temps.
The other side of that coin is that the higher the inertia ( or lower ratio ) the in cycle speed variation of the crank is reduced , and the engine makes more power.
This was discovered by Dr Fleck at QUB , when using correctly calibrated dyno's the heavyer inertial loaded one would make more power on the same engine.

There is a real Catch 22 with crank or other inertial loads.
More crank inertia reduces the in cycle speed variation , but of course a greater inertia crank is harder to accelerate.

But a test I did on a 500GP bike at Sepang involved two identical bikes side by side.
One had a normal Ti clutch with alloy and the usual fibre clutch plates , the other had a 10.000 GBP AP carbon carbon clutch pack.
Out of the final corner onto the straight past the pits , the carbon clutch bike pulled near on one bike length advantage per gearchange , and ended 8Km/Hr faster into turn 1
The only issue was none of the riders could get the starts to work reliably and it was shelved , as did all the other teams.

[SwePatrick]

To clarify I see 8: 1 higher ratio than 1: 1 if you misunderstood / wanted to misunderstand. What do you usually do when you run 1: 1? Sometimes, it is not possible to get close to previous references and then you start to think about these question.

I just meant the gearbox ratio, always dyno in gear closest to 1:1, this gives you the least impact on the result as there are the least losses inside the engine.
I cannot for obvious reason run 1:1 (crank/dynoroller)
In my opinion there are never any reasons for sweeping through the gears when adjusting the engine.
It only becomes a reason when tracing problems or setting up functions, shifting point´s(to maximize acceleration), shiftcut, etc etc.

And if dyno´s inertia don´t match your vehicles mass, there are even less reasons to sweep through the gears.

No, i don´t start to think about those questions as i see usage of dyno a more openeyed way of what´s what and know how software and physics works.
It just becomes that way when owning a dyno, build one and study :niceone:

So in short: No the impact of engines own inertia is higher in lower gears, or should i say the impact is bigger when engine runs through the rpm band faster?

If having this(ineria correction) correctly setup in software and pipe and engine is warm, plus got the traction on the roller.(very hard in lower gears)
The powergraph should vary very little in numbers between the gears.

Frits!
i have dynoed my yamaha 84.3hp to the wheel(e85 fuel) and my dyno report it to about 93.7 at the crank when doing a coastdown with holding the clutch, is this about what would disappear in losses through drivetrain?

[Muhr]

If having this(ineria correction) correctly setup in software and pipe and engine is warm, plus got the traction on the roller.(very hard in lower gears)
The powergraph should vary very little in numbers between the gears.


My question is about exactly what you say your program can handle, so I wonder how the program did this guesstimation?

[Frits Overmars]

i have dynoed my yamaha 84.3hp to the wheel(e85 fuel) and my dyno report it to about 93.7 at the crank when doing a coastdown with holding the clutch, is this about what would disappear in losses through drivetrain?More or less, but as I tried to explain above, it cannot be exact. Transmission losses are mainly a percentage of the transmitted power but this transmitted power is absent during a coast-down run and you cannot measure something that is not there. Furthermore, a pulled clutch never opens 100%; there will always be some drag, and there's no telling how much it will be.

[SwePatrick]

My question is about exactly what you say your program can handle, so I wonder how the program did this guesstimation?

You configure the engines inertia, almost impossible to calculate, you need to calculate each gear(that spins), clutch, crank.
Make it easy for yourself and just measure the inertia of the crank and clutch separated from the engine.
Use falling weight method.

And then,, you got friction, oil churging etc etc.

[Muhr]

You configure the engines inertia, almost impossible to calculate, you need to calculate each gear(that spins), clutch, crank.
Make it easy for yourself and just measure the inertia of the crank and clutch separated from the engine.
Use falling weight method.

And then,, you got friction, oil churging etc etc.

I think most people here have an idea how they could do this the hard way. The question was about a simplified estimation, similar to crank power.
It sounds incredible that your program wants you to specify this for each engine you run.

[SwePatrick]

I think most people here have an idea how they could do this the hard way. The question was about a simplified estimation, similar to crank power.
It sounds incredible that your program wants you to specify this for each engine you run.

As every engine differs, so ofcourse you need to edit this to suit the engine.
But, i don´t use it, it´s not interesting because what i wrote earlier.

Don´t let let it block your mind, forget it and go on with more useful stuff to do, like starting up your project ;)

The simplified way, i hinted of that earlier, but again:

'If value is setup correct the enginepower should differ very little between the gears in a pull through the gears...'

And by that, just put in a random number and look at the difference, adjust until you´re happy.
(and still be asking yourself if it´s really correct)

[Muhr]

As every engine differs, so ofcourse you need to edit this to suit the engine.
But, i don´t use it, it´s not interesting because what i wrote earlier.

Don´t let let it block your mind, forget it and go on with more useful stuff to do, like starting up your project ;)

The simplified way, i hinted of that earlier, but again:

'If value is setup correct the enginepower should differ very little between the gears in a pull through the gears...'

And by that, just put in a random number and look at the difference, adjust until you´re happy.
(and still be asking yourself if it´s really correct)

I think a little like this! If we assume that we have a run of 6 seconds between 8500 and 14500 it is about 105 rad / s2 if we do it in half the time then it is about 210 rad / s2
If we then assume that we have a driveline weight of 6 kg and an inertia radius of 3 cm (dia 6cm). Very simplified but still ....
Then it would be something like 6 * 0.03 (M)*105*0.03/2 = 0.2835 MN linear, which should be at least 2-3x that at peak torque. As I said very simplified but you probably have something to add here ...

Of course small potatoes for you with the torque you present from an old mild sport oriented engine from the early 80's. But for a little guy like me, it makes a difference.
Or maybe I should just adjust the numbers until I'm happy.

[wobbly]

A DynoJet has a fudge factor built into the software that cannot be adjusted.
It occurred during development , using a Harley as a test mule - it didnt seem to make enough power , so they " adjusted " it.
This was because the HD had huge , heavy flywheels , and wheels/tyres etc.
Now when we test a kart on one it seems to read high , due to very low inertial loads.

Even in this case we have to adjust the gear used to get a suitable runup time for the pipe to be hot enough , or add Eddy Current load % to slow the acceleration rate.
My engine dyno is calibrated , with load drop and rundown factors in the software , but I dont use the Sportsdevices engine inertial factor as all the engines are similar in this respect.
The engine dyno reads around 12.5% higher than a Dynojet , that makes perfect sense to me.

But at the end of the day the raw numbers make no difference at all.
Does one reed petal make better power , yes or no , as long as the dyno and my method is absolutely repeatable the answer is all that matters.
I have checked this dozens of times using the track data logger , plugged into a virtual dyno with NT sofware.
This converts the data into a Hp graph , and any change in power from the actual dyno , is reflected exactly as the same difference on track.

[adegnes]

349388

Cheers everyone!
Been a while. Yet again.

Don't know where to start.
First, Thank you TZ for consistently sharing my videos!
Thank you Ken for the emails, and the reminder to check out the ESE thread.
I've got a lot of reading up to do, at least a year back, maybe two, hell even three.
I'm more than halfway into that bottle, and tend to become overly philosophical at this point, now being no exception. Keep that in mind.
My absence is not merely lack of time(still a big part of it though), but also a conscious decision to shroud myself from the input of all the brilliant minds on here.
Ludicrous, I know. But you see, the best moments for me, are those moments when I've come up with something(to me) brilliant all on my own, with little external input. It might not really be that brilliant, and it might have been thought of before, but the feeling is still real.

After a while I get too curious and cave in, like now. Luckily I've got a lot of reading up to do.

I really believe I can make the most powerful two stroke ever(hp vs cc, must not forget to specify), eventually.
I mean, why settle for anything less?
It's all about the journey though, learning things, evolving, establishing connections between everything you pick up along the way. No matter how immediately irrelevant something seems, there's always something to draw from it.
Even wood chopping...

Anyways.

The PiP engine is up and running now with a bridged exhaust.
I'm not giving up on the 100% exhaust, just moving the experimentation over to a dedicated engine for just that.
Wobbly, I know it's proven tech, but I also know they ran that patented L-ring with a big dip in the middle of the exhaust roof(like that "W" port, just not as bad...)
With a proper chamfer/radius, and the right ring construction I think it can work fine without a "dip".

I'm set on Bonneville next year, and I need something running and somewhat reliable, had to turn down the amount of experimental stuff involved.

Don't tell anyone, but the brute force engine is mostly to see where I'm at in the fully-fledged-prototyping-facility-game.
Almost there.
I have a feeling it can produce some power tho, and lots of flames!
It's also kind of a relaxing project, a dumb engine, "brutus".


Picked up a telma retarder 2 days ago, building a load cell dyno. Was originally going for a diy hydraulic pump type, but changed my mind. Getting older, slowly more sensible...

Cheers!

[teriks]

Took a little vid of the engine running at lower speeds and no load. Does show a depression in DCI passages.

https://studio.youtube.com/video/D6EX3x8yptU/edit
Your link didnt work, (unless you log in, probably with your account at that).
http://youtube.com/video/D6EX3x8yptU should work though.

[F5 Dave]

A DynoJet has a fudge factor built into the software that cannot be adjusted.
It occurred during development , using a Harley as a test mule - it didnt seem to make enough power , so they " adjusted " it.
This was because the HD had huge , heavy flywheels , and wheels/tyres etc.
. . .

Wasn't enough fudge. (Spookily I am actually munching some chocolate and biscuit baking goodness as I type). A mate (Chris Sayle) bought the first DJ in Wellington late last century.

He had some disappointed Hardly customers. Fortunately for them WMC bought a dyno and that gave 'the right figures'.:lol: pity as they were easily parted with their money. Improvements Largely by removing the Thunder Wailing Budgie go faster parts they had bought. Also unpopular.

[ken seeber]

Your link didnt work, (unless you log in, probably with your account at that).
http://youtube.com/video/D6EX3x8yptU should work though.

Teriks,

Good spotting and thanks for that. My youtubing skills are clearly lacking....age.

Should get the thing running with the single DCI carb today/tomos.

http://youtube.com/video/D6EX3x8yptU

[speedpro]

349331
It looks like the .3r section makes up 90degrees(.3r radius & .3r height) leaving 90degrees for the other 2 sections combined. Is there a preferred angular displacement for each radius section? I have drawn something like this but with 60degrees for each radius which "looks" OK.
Also, should there be a taper on the main body of the velocity stack and if so what angle, included or per side?
Application is a FI FZR250

[speedpro]

Wasn't enough fudge. (Spookily I am actually munching some chocolate and biscuit baking goodness as I type). A mate (Chris Sayle) bought the first DJ in Wellington late last century.

He had some disappointed Hardly customers. Fortunately for them WMC bought a dyno and that gave 'the right figures'.:lol: pity as they were easily parted with their money. Improvements Largely by removing the Thunder Wailing Budgie go faster parts they had bought. Also unpopular.
I recall one customer Hardly where the "Thunder Jet" had to be blocked to make the bike go properly(for a Hardly). Another had a small fortune spent on it with the result that it made the exact same horsepower as Viv's stock ZZR600 in back-to-back dyno runs

[ken seeber]

Here's a quick vid of the DCI engine running on the main carb and the DCI carb, with no fuel, is opened up.
No explosions, it just revs up.....I'm excited.

https://www.youtube.com/watch?v=gmX4cD7x3F4

[Frits Overmars]

It looks like the .3r section makes up 90degrees(.3r radius & .3r height) leaving 90degrees for the other 2 sections combined. Is there a preferred angular displacement for each radius section? I have drawn something like this but with 60degrees for each radius which "looks" OK. Also, should there be a taper on the main body of the velocity stack and if so what angle, included or per side? Application is a FI FZR250That three-radii bellmouth drawing (it's an oldie from a German paper that's almost as old as I am) shows a fairly effective approximation of what theoretically ought to be a continuously-increasing radius.
As the local diameter of the bellmouth tightens downstream, the flow velocity increases and the bellmouth radius should also increase in order to keep the transversal acceleration of the air molecules within bounds and so prevent flow detachment, turbulence and pressure losses.

I take it that with "the main body of the velocity stack" you mean the cylindrical or conical part between the bellmouth and the carb.
Well, it has no right to be there at all. The carb should be at the beginning of the inlet tract, not 'somewhere in the middle' where inlet pulses may pass over the jet in both directions, each time picking up fuel and making carb adjustment a nightmare. You may get away with it if you have intake fuel injection, but that brings its own problems in two-strokes.



Here's a quick vid of the DCI engine running on the main carb and the DCI carb, with no fuel, is opened up.
No explosions, it just revs up.....I'm excited. https://www.youtube.com/watch?v=gmX4cD7x3F4Now imagine restoring the scavenging symmetry by having the engine breathe cold mixture with the correct air/fuel ratio through both side-mounted carbs :D.

[SwePatrick]

Or maybe I should just adjust the numbers until I'm happy.

With statement like this you won´t get far regarding credits in my bag.
I tried to say you are chasing things with minor interest, just go for the raw data as wobbly says.
Don´t bother if your dyno shows 200hp, if you have gained 1hp and have done it with good repeatibility you have done something good.

Use the exact same dyno all the time when developing.
Comparing to others, i always call it 'dick contest'

Talk softly and carry a big stick! :innocent:

[Muhr]

just put in a random number and look at the difference, adjust until you´re happy.
(and still be asking yourself if it´s really correct)



Or maybe I should just adjust the numbers until I'm happy.


With statement like this you won´t get far regarding credits in my bag.


Talk softly and carry a big stick! :innocent:

Ok! I would like to avoid being in that bag.

[Vannik]

I know this video is on diesel engine emission testing but about a third of the way in they show the crankshaft speed fluctuation in one cycle (well maybe 4 cycles :laugh:) and it is what Wobbly and Frits have mentioned a number of times in that in a 2T engine it influences how long the ports stay open:

https://www.youtube.com/watch?v=Yjh_U9LLxY4

[speedpro]

Private video

[teriks]

Private video
Too bad, was available yesterday..

[TZ350]

.
349399

Blue line is WOT and the Red line is the throttle partially closed.

I have always wondered why my fifty when it was tapped out on WOT going down the back straight, it would pick up speed when I closed the throttle a bit..... :scratch:

Fixed ignition timing, 24mm Carb, no power jet. Ignition and main jet optimized on the dyno with WOT wide open throttle runs.

Any suggestions/thoughts would be welcome.

[husaberg]

.
349399

Blue line is WOT and the Red line is the throttle partially closed.

I have always wondered why my fifty when it was tapped out on WOT going down the back straight, would pick up speed when I closed the throttle a bit..... :scratch:

Fixed ignition timing, 24mm Carb, no power jet. Ignition and main jet optimized on the dyno with WOT wide open throttle runs.

Any suggestions/thoughts would be welcome.


Carburation wise if it picks up speed when the throttle is closed it's too lean.

[Frits Overmars]

.I have always wondered why my fifty when it was tapped out on WOT going down the back straight, it would pick up speed when I closed the throttle a bit..... Fixed ignition timing, 24mm Carb, no power jet. Ignition and main jet optimized on the dyno with WOT wide open throttle runs.


Carburation wise if it picks up speed when the throttle is closed it's too lean.I'm curious for a further explanation Husa. I'd rather expect it to be too rich. Then closing the throttle will lower the needle in the needle jet, making the mixture leaner.

[ken seeber]

Got the DCI running with fuel into the DCI carb, seems to work...

https://www.youtube.com/watch?v=iAf1gbWztT8

[136kg136ps]

Frits, wouldn't closing the throttle also lower the amount of air entering, possibly making it richer momentarily somewhat like choke. Seems a catch 22 to me. But y'all are over my head half of the time anyway.

[Muhr]

I'm curious for a further explanation Husa. I'd rather expect it to be too rich. Then closing the throttle will lower the needle in the needle jet, making the mixture leaner.

Can you not both have a point if we think for example a K 27 and a U needle eg U11

[Frits Overmars]

Frits, wouldn't closing the throttle also lower the amount of air entering, possibly making it richer momentarily somewhat like choke.I cannot rule it out, but I've never experienced myself that closing a throttle makes the mixture richer. On the other hand, I have often witnessed it getting leaner, sometimes resulting in seizures and crashes.


... y'all are over my head half of the time anyway.Let's be glad this isn't a swimming competition :D.
Joking apart, I try to write simple and understandable and I like to think I was rather good at it in my previous life as a technical editor.
But English is not my native language so there will no doubt be room for improvement. Just keep on asking if something is not clear.

[jonny quest]

TZ350, is pipe temp the same for both runs?

Those runs to me look like a pipe temperature difference.

Or, it's really not making any more power as dyno is showing, it's just showing its revving higher... the leaner part throttle mixture is making pipe temp higher with 2 things.

Leaner mixture = pipe temp increase

Less airflow going through = hotter cylinder and pipe

[teriks]

Got the DCI running with fuel into the DCI carb, seems to work...

https://www.youtube.com/watch?v=iAf1gbWztT8
Very cool! The concept for sure works, looking forward to see the continuation.

[wobbly]

Muhr , the effect you are describing is bound up in the fact that a KZ carb is way too small for a 50 Hp 125 engine.
The airflow velocity is VERY high , thus the venturi depression created necessitates a very small main jet to achieve the correct A/F ratio.
This also means the needle/tube combination has a very small annulus area at WOT.
In fact a well tuned KZ will rev to 12,000 with no main jet at all - been there done that , not intentionally I might add ( dumb or even dumber ).

But back to TeeZee dilemma , in this case the partially closed slide is decreasing the carbs airflow , way less than it is decreasing fuel flow from the emulsion tube nozzle , thus its (edit) :leaning the fuel curve over the top of the pipe.
This is evidence of the fact that airflow thru the venturi continues to increase past the power peak , but less fuel is required at this point , as the combination of scavenging and trapping efficiency % is decreasing even faster
If you had an electronic PJ this could be switched off , to achieve the required fuel curve past peak power - and this would increase the overev power exactly as per the red curve.

But in this case I would suggest fitting a much bigger main air corrector jet , this will need a comensurately bigger main to get the peak power fueling/egt the same , but then the big air corrector will
continue to lean off the overev fuel curve automatically.
I have done the reverse of this several times to stop having to run a huge main to prevent an engines egt from continuing to run away past peak Hp , thus killing the peak power number with an over rich condition.
The same can be done by using a flat line ignition curve past peak Hp , thus reducing the pipe egt/heat runaway, so reducing the need to add fuel to help cooling - not power.

Again - proving that your engine is doing just that , with a flat line ignition .
Always a dumb idea.

Edit - i mistakenly wrote leaning - richening is correct - sorry

[husaberg]

I'm curious for a further explanation Husa. I'd rather expect it to be too rich. Then closing the throttle will lower the needle in the needle jet, making the mixture leaner.

The reasoning is from everyone from Bell to jennings and Gorr says the same.:innocent:
ALthough i have seen Cameron say the opposite once. i have had the same its always been cured by making the main or PJ larger.

I'd suggest the reasoning is when you are backing off slightly but not enough for the overlapping needle to have much effect
The backing off a little at the end of a long straight as Rob suggested and then running better. i assume there is still a strong fuel signal but less airflow so the momentary to lean condition is corrected from the too lean to the optimum. as the airflow decreased faster than i suspect the fuel flow does as its has more ineteria so there is a lag.
if you were shutting off the throttle a longer way it would be on the needle. As the greatest area of a needle Effects, MIO is 3/8 to 3/4 throttle (unless of course the tapper is well off or the NJ is to small.)
349403

i just read Wobs response maybe it can be both.
Camerons has said a few times rolling off and if it picks up revs then the mixture is too rich
349404
maybe depending on if the carbs optimal size its too rich if its undersize for MAx HP its indicates to lean
Too small carbs auto en richen at peak revs where as bigger ones tend to lean out


you could also try a taller or shorter hood on the Needle jet to alter the fuel supply.
as bones harder to fix than fouled plugs Maybe Rob can try a richer jet first and see if it makes it worse?


349407349406349405

[F5 Dave]

First thing I always (sometime remember) do is pull the main out and see if the bike will run past 3/4 throttle, or if the needle jet is still the restriction.

Actually I think this is where I came in probably on page 1 or 2 of this thread.

[Muhr]

Wob, yes true in the case I described. "Described" perhaps a little bit rich to call it
However, I think the discussion that took place is interesting


Here I think was a pretty interesting run. (Off topic above)
Same:
Carburettor
Reed
Crankcase assembly
Head volume
Piston
Port duration (transfer time area not much difference)
Exhaust (Ok, was probably no benefit to the blue)


Clearly state what certain things can be more important ..

[wobbly]

Now I understand what I was confusingly trying to say above - the WOT run is going rich over the top.
The partially closed run has the fuel curve leaner over the top , thus the extension to the power band.
I have tried lowering the shroud , ( Dellorto make long and short variants ) as I thought in the small 30mm carb this would restrict airflow , but sadly no free lunch.
Once it was rejetted to get the same egt , the power was identical.
A retarding ignition or an electronic PJ would for sure work to pull up the egt past peak and increase overev power.

[Muhr]

I have tried lowering the shroud , ( Dellorto make long and short variants )


Is it the same as atomizer? or is it something else you are referring to?

[wobbly]

Muhr , yes the atomiser shroud in your hand.
I did a back to back with the long and short variant , thinking the short one would create less turbulence in the small 30mm bore.
But from memory I had to make a 3 main jet change to get identical egt , and bugger , the power curve didnt change at all.

[Muhr]

Can not say that my experience has been different, however, may be useful in some applications

[sniemisto]

I was trying 24mm and 28mm PWK carburetors on dyno. I ended up with both producing identical EGT 580C to end of 6th gear run. They did that with identical 120 main jet.
28mm was better in top and over rev (photo enclosed, solid line is 28mm). With 125 I got almost same power as 24mm with 120.

On open road testing I usually end up to EGT 680C with long gearing. For some reason 28mm was going really high, up to 760C. I needed to jet up until 128 main until I ended up with 680C.
With both both jets I lose power if I try to turn throttle back from WOT.

Why bigger carburetor is making hotter EGT in open road, but still acting same as smaller in dyno??

28mm is original Keihin from KTM SX and is having “2t cut” in atomizer shroud. 24mm is chinese YSN coby and it has lower 4t type atomizer with uncut straight end.

Wobbly mentioned that atomizer lenght affected on main jet sizing. Could we be dealing on related thing here?

Bike is Derbi 50cc with FOS pipe having 14mm stinger restriction. I measure EGT 150mm from piston face.

Regards,
Sami

https://uploads.tapatalk-cdn.com/20210724/4135fcbeea0839a6ed3162165c07e053.jpg


Sent from my iPhone using Tapatalk

[wobbly]

The problem to deal with first is the huge difference in egt on the dyno and the road .
This in short means the dyno is not representing the real power curve of the pipe , not even close with 100*C difference in egt
But the other issue is that any engine that can survive being run at 760*C has serious tuning issues , probably way too much ignition retard in the overev.
This means you are choosing the main jet to kill exhaust temp - not make power , but the dyno never even gets to that temp , so who knows what the issue really is ?

[sniemisto]

Thanks Wobbly for your reply. I think I understand.
When I’m not able to get enough egt for good power in dyno, I end up over retarding it in over rev. That produces too high egt in open road testing and that sould be corrected with advancing until temp is again low enough, not with jetting up. I should then change pipe dimensions if I’m not happy with power after that.

I haven’t measured egt in typical kart track we are racing, I assume temp is lower with shorter gearing and not that much overrev. That should be good thing to test. Anyway problem is still there.

I like testing bike with long gearing overrev run because we have one meeting every year we are running on really long straights. Somehow piston is doing great with 4 hour race and 680C. On 760C test I stopped straight after I saw it. I’m not 100% sure if my egt gauge is reading right.

I run 16 degree advance on max power 12300 rpm, it goes to 5 in 14000 rpm and stays there. It can be seen in open road that egt starts rising after 13000 rpm when advance is dropping under 10.

Our inertial dyno is not able to get real egt and power curve of pipe. Maybe some wrapping during dyno could fix this problem a bit? Or this type of heat buildup is not replicating real situation?


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[wobbly]

The first issue is to get the dyno inertia/gearing such that the run time is long enough to replicate the acceleration rate at the track.
680*C is fine if the engine was designed to be run at that temp , with the fuel suiting the compression.
But it has been my experience that 680* as a pipe design temp is only possible on 110 octane if the compression and timing are correct.
15* at peak power is absolutely right ( for good fuel at 680* - what is it ? ) and kart tracks always favour high compression for off corner drive with plenty of turns
and usually only one long straight.

But having the egt climb to 780* past peak power when held up there is a function of 3 elements.
Too much retard - I would be looking to drop to say 10* - 1000 rpm past peak , then flat line it.

Secondly , to prevent having to jet up to stop temp runaway , the main air corrector needs to be reduced in size - this then means a smaller main can be used to get best peak power
at the correct temp the pipe was designed around , and the egt wont keep on rising. If the corrector and the retard are correct , then the engine will make peak power at the correct egt
and it will hold this egt into the overev. The smaller corrector keeps the fuel curve tracking the best power bsfc number more accurately.

Lastly compression , the fact the engine survived 780* simply means the compression must be too low - even given the severe retard curve.
Severe retard can be used if the pipe Lt is purposely made too long , to help mid power ( also if the longer Lt gives better superposition in concert with the chosen EPO timing ).
And then the long pipe is made to rev well past its designed rpm with retard generated header temp - but in this case an electronic power jet works even better.

[sniemisto]

Thanks a lot, there’s many good points I can proceed with.
Engine has 13,5 compression and running on 98 octane with 5% ethanol.


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[Muhr]

One question, are you on target with the rest of the engine as you are with stinger reduction / exhaust?
If you have an efficient exhaust but perhaps not as efficient supply of fresh gas?
As for compression, I use for example 8.2cc head on a 125cc with 98 octane does not say much. I think that RON is not very interesting, your MON value will determine, where I assume that you have 87.5 at a gas station in Finland with 5% ethanol. But you should at least be able to run a 3.3-3,2cc head

[sniemisto]

Muhr, I’m not at target.
I’was about to mach my egt figures with EngMod and real life to produce new pipe dimensions. Then I faced this too high temp issue.

There is also many thing I plan to do differently on next cylinder. I have too high aux exhaust ports (main 192,8 - aux 192), STA is still blowdown limited, too low axial angles.. + other small things.

I have fresh power valve cylinder to start modificate for new spec, but it has waited to properly match my EngMod model to current situation. It now appears that it still need these dyno / egt issues solved before I’m there.

Thanks for your reply, 3,2cc head is thing that I like to test also.


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[sniemisto]

I adjusted ignition curve like wobbly suggested and keeped carb as it was with big 128 main jet. It felt goin same as usual on the road test, 106km/h @ 14100 rpm.

I tried to do 2-5 gear accelerations and brakings replicating race track. EGT stays quite nicely in 580-600C, same as dyno is capable of. Still with long 6th gear pull it went up to 675C, but took longer time.

Edit: There is air correction hole in carb frame, located in same passage as idle air screw. It is 0,6-0,7mm (no correct size wire to accurately measure). I put piece of gasket there to block it. It produced quite same EGTs during test ride. Bike felt accelerating better, need to dyno it if there is changes to see.
I didn’t try to jet down at this point as EGT is still high.

[philou]

14mm stinger is very small.
For a 50 cc I never go below 16 mm

[wobbly]

I believe now we have more info , and I have slept on it , the underlying issue is not directly the swept compression , but the dynamic compression.
This factor is affected by the Delivery Ratio , and the scavenging plus trapping efficiency %.
If any of these three are compromised then the real trapped compression ratio is low.

In this case , changing just the ignition curve , dropped near 100*C , out of the long run temp , proving that that element was seriously wrong for the pipe length and tune.
Getting to just under 600* for the short sprint track simulation is low, so for that scenario it needs jetting down.

I would say that as something else is badly affecting the dynamic compression , that you could go up a whole point in swept compression , lean it down and make a good gain in power.
Of course fixing the real issue has got to be the plan.
Be interesting to know what the Mach is in the stinger nozzle , if the bmep is low due to the low dynamic com , then a 14mm stinger may suit this engine just fine as it is now.

[F5 Dave]

Just a point on measuring compression on a 50.

Measure Measure Measure. When you start getting consistent results then start writing them down. They are so small the difference of 0.sodall of a cc makes a big difference.

I would grease the ring, run it up to the top, wipe, lock flywheel, put on head, 5w fork oil, burrette , fill till 2nd thread to account for spark plug.

Then wipe. Repeat again and again. Then again. Of course sunken spark position complicates matters.

[wobbly]

Better way to do it is to use a flat plate of clear plastic.
Using a thin wipe of grease glue the plate to the head surface and using ATF fill it to the top of the threads.
Clean it up and repeat turned over with the plug in , and a plate with a hole in it.
The different readings give you exactly the assembled plug thread volume.
Then if you use ATF you dont need any grease around the ring , as all this does is fill up the volume between the ring and the bore.
The only downside , but this applies to any oily fluid , is you must leave the burette sitting for at leat 15 to 20 minutes , as the dropping fluid level leaves around 0.5mil on the glass bore
dependant upon the speed of pour.
The very reason I finally bit the bullet and got raped buying a digital lab burette - a used one from an American medical auction house still cost me 400 USD.
Dead cool way to do it and accurate to 0.01cc.

[Muhr]

Muhr, I’m not at target.
I’was about to mach my egt figures with EngMod and real life to produce new pipe dimensions. Then I faced this too high temp issue.

There is also many thing I plan to do differently on next cylinder. I have too high aux exhaust ports (main 192,8 - aux 192), STA is still blowdown limited, too low axial angles.. + other small things.


I had not guessed that BD was your biggest limitation.



I usually draw the volume in the computer and confirm with burette. here is a 50cc with a 2cc dowel

[Frits Overmars]

Better way to do it is to use a flat plate of clear plastic. Using a thin wipe of grease glue the plate to the head surface and using ATF fill it to the top of the threads.
Clean it up and repeat turned over with the plug in , and a plate with a hole in it.I use a perspex plate with two 5 mm Ø holes in it, about 15 mm apart: one hole to administer the oil, the second hole to let the air bubble out. It's much easier that way.

[sniemisto]

Oh boy, I haven’t tough enough about head volume accuracy needed on 50cc calculations, even how easy it is to see with simple calculations.

I have just placed head upside down with spark plug in place. Sealed plexiglass with grease, then filled through hole by pouring hydraulic oil with 5ml syringe.

I have made assumption that excluded squish volume is about same as piston dome top. That is very rough assumption and off course not true.
My 4cc head is something else in reality.

Now I need to buy burette and measure true head volume from assembled engine like you described.


I need to correct that 80C egt temp drop was mainly done by jetting up main from 120 to 128.
Advancing ignition did slow down egt rise, but on long 6th gear run it still end up almost same 680C as with more delayed curve.

[Muhr]

I have lived in the belief that cavity / protrusion take each other out on a spark plug. Maybe not the case?
In any case, it is more important to have your method and have it as a reference
when trying different things. Buying an expensive tool is definitely not a must but makes it quite easy.

[F5 Dave]

Make sure you bolt the barrel down as small engines have through bolts rather than base studs.

[wobbly]

Thanks Frits , great to learn something every day.
Guess I will be drilling a second hole in my prespex.

[speedpro]

I used syringes of oil and measured the plunger travel with calipers. Accurate enough for me.

[wobbly]

Yea well SpeedPro , the engines you were dealing with would not even notice 0.5cc either way.
A 50 + Hp 125 on the other had will self destruct instantly with that sort of error if it wasnt for airport weather stations ,egt and deto datalogging.

[Muhr]

Make sure you bolt the barrel down as small engines have through bolts rather than base studs.



Thanks for your reply, 3,2cc head is thing that I like to test also.



And it can be really problematic with these through bolts when you start raising the compression. on the motor in the picture, we first pulled out the threads on the nuts and when we changed to stronger, we pulled out the threads in the block after which we had problems that the stud bolts stretched. Finally we put helical threads and made new stud bolts M7 (original M6) in SS 2242 (AISI-SAE H13)If I remember correctly.

[speedpro]

Yea well SpeedPro , the engines you were dealing with would not even notice 0.5cc either way.
A 50 + Hp 125 on the other had will self destruct instantly with that sort of error if it wasnt for airport weather stations ,egt and deto datalogging.
True. The engines weren't particularly highly tuned although the last one started to head in the right direction. I did get repeatable results, and always took at least 4-5 separate measurements. Variation was easily less than .15cc

[TZ350]

Yea well SpeedPro , the engines you were dealing with would not even notice 0.5cc either way.
A 50 + Hp 125 on the other had will self destruct instantly with that sort of error if it wasn't for airport weather stations ,egt and deto datalogging.

Its true, Buckets are not at the very pointy end of development but SpeedPro was the first to make a verified 30 RWHP. He did it with a Honda MB100 commuter bike engine. Output was tested on Team ESE's dyno jet dyno.

[wobbly]

Not a critic of SpeedPro at all - i was involved in some of his projects and he always produced fine work.
Just my view is you use a hypo if you cant afford/justify a burette , and you use a burette if you cant afford/justify a digital titrator.

[andreas]

Does someone know about chassis geometry/tuning? Or what's relevant for turning. my bike wants to go straight, I have to pry the bars out in all corners or I have to lean over (quite drastically). This can be a tire issue? Or something else that can be altered?

[husaberg]

Does someone know about chassis geometry/tuning? Or what's relevant for turning. my bike wants to go straight, I have to pry the bars out in all corners or I have to lean over (quite drastically). This can be a tire issue? Or something else that can be altered?

Raise the rear lower the front put on a sharper profile front tire and or smaller front wheel lower profile or a narrower tire. Experiment with a higher front pressure. Shorten the wheelbase. Take off the steering damper or set to zero.
Buy the Foale chassis book or the Bradey book or any of Camerons books.
Countersteer as well.
but anything you can do to lessen the trail will help from what you describe.

[wobbly]

Drop the forks thru the tripples to lower the front.
Next big change is to reduce the trail with different tripple offset and/or change to a lower section height front tyre ie a 50 down from 60.
Lifting the rear is last ditch , as it affects the squat geomerty.

[andreas]

Aha, thanks Husa, indeed the bika came with a jack up kit at the rear, and the front end was dropped about 10mm. I set it back to standard because I hated the riding position, even lowered the rear some, and the changes in handling from this was too small for me to notice. The tires are Pirelli supercorsa, and I'm inclined to think a narrower front will help some. The Foale book, i'll try and find it.

[andreas]

Thanks Wobbly, I think it's a 120/70 right now. Less profile will help?

[wobbly]

Stay at 120 but lower the section height , this keeps the grip , lowers the front and puts more weight transfer into the front tyre when turning in.

[andreas]

Ok, I understand this will reduce the trail. It respond quickly but just needs a lot of counter steering or leaning out.

[husaberg]

https://books.google.co.nz/books?id=84hF-qoR5I8C&pg=PP2&hl=da&source=gbs_selected_pages&cad=2#v=onepage&q&f=false

[andreas]

https://books.google.co.nz/books?id=84hF-qoR5I8C&pg=PP2&hl=da&source=gbs_selected_pages&cad=2#v=onepage&q&f=false


Thanks Husa.