ESE's works engine tuner

[Drew]

Well, the shape is measured by is radius (or radii if it's plural ;) ) but according to construction geometry the shape would be most accurately defined as a fillet.

A chamfer is a angled flat between two surfaces, as is a bevel.So the edge these guys are talking about, is rounded? I thought they were just grinding and angle bit to teh top port edge. Why they do this is not exactly clear. But I might just have missed something, everyone else on here gets it all, so stuff gets only brief explanation for dumb builder types.

[Ocean1]

So the edge these guys are talking about, is rounded? I thought they were just grinding and angle bit to teh top port edge. Why they do this is not exactly clear. But I might just have missed something, everyone else on here gets it all, so stuff gets only brief explanation for dumb builder types.

Yes, a deliberately rounded edge to the top of the port at the cylinder wall.

Gas flows differently at different speeds, it'll follow the curve at some velocities, not at others. You can use this to effectively alter port timing over the rev range.

There's almost certainly more highly refined shapes that could match gas behaviour with that ideal timing even betterer, but I suspect you'd need a glass engine and high speed video to fine them without many thousands of build/test itterations.

[Drew]

Yes, a deliberately rounded edge to the top of the port at the cylinder wall.

Gas flows differently at different speeds, it'll follow the curve at some velocities, not at others. You can use this to effectively alter port timing over the rev range.

There's almost certainly more highly refined shapes that could match gas behaviour with that ideal timing even betterer, but I suspect you'd need a glass engine and high speed video to fine them without many thousands of build/test itterations.

Thanks mate. Much more clearerer.

[dinamik2t]

I have thought of it like so:

269637269638

And here (I shot random photos and this 4.5 was better for explaining than the 3.5s)

269636


The 3.5 number is the radius of the fillet applied.
What I haven't got clarified is whether at 196*/yellow-line there is already an on-bore-surface radius or it is horizontal.
In my pic at least, there are (exaggerated): the top corner radii ^ the top edge radius until 196* ^ the drawn red radius until 202*.





everyone else on here gets it all, so stuff gets only brief explanation for dumb builder types.

I think that it is out of respect for Frits' or Wob's or anybody's private life and free time, that we do not ask for further explanation when something is shared..
No need to be mean.:drinknsin

[cotswold]

Just a couple of photo's of the porting progress ( or lack of ) on my interim cylinder. A bit of a bomb site but I can usually find what I'm after.
There are some broken tooling bits that has slowed me down ( managed to break off a drill bit but got that out with a bit of help from the Dremel ) but I have a heavy duty replacement on it's way, hopefully get it early next week so I can get it finished.

[TZ350]

Looking good, I like the work bench for holding the cylinder, good idea ....

[dinamik2t]

I see a drill there! How that is working with the porting bits? I always though an electric drill would be too powerfull for hand use, but I am most curious to know your opinion ad experiences.


By the way, Wob.. an idea I had last night. Would it be possible to guide mr Neels of EngMod to create an Aprilia scavening pattern?? Since it's becoming quite popular these days.
Or (of cource) we should ask him ourselves, if it's something he can do without a specialist's help.:yes:

[Frits Overmars]

By the way, Wob.. an idea I had last night. Would it be possible to guide mr Neels of EngMod to create an Aprilia scavening pattern?? Since it's becoming quite popular these days. Or we should ask him ourselves, if it's something he can do without a specialist's help.:yes:I know you're joking, but just in case: though Neels is a studied man, he also has plenty hands-on experience: "I am an engineer that does a bit of programming, not a programmer that does a bit of engineering." http://www.vannik.co.za/About.htm

[2T Institute]

The Aprilia scavenging is a case of the "whole is greater than the sum of the parts". Inputting the exact data from the drawings the outputs are nothing like the real thing.

[TZ350]

I see a drill there! How is that working out with the porting bits? I always thought an electric drill would be too powerfull for hand use, but I am most curious to know your opinion and experiences.

Yep, hand drills are good, you can do some quite good work with basic hand tools.

[dinamik2t]

I know you're joking

Then I shouldn't explain myself any further. :yawn:
Actually that phrase was told to me via email in 2010. Wobbly already had his hands on his own aprilia-like cylinder, plus he knows the program, so he could inform Neels of dimensions, without (Neels) having to get an RSW/A cylinder himself. I would very much like to know(have?) the capabilities of an engineer of Neels' caliber, unfortunately I don't, so I asked politely. If I offended him, I can't do anything but apologize.



Yep, hand drills are good, you can do some quite good work with basic hand tools.

I tried once with emery paper rolls into the ex duct, but it was bumping all over the place! :doobey:

[wobbly]

I think as Lozza alluded to, the issue with the Aprilia scavenging setup is that there are a huge number of details that collectively create a very synergistic whole.
Everything from the radius being discussed here of late to the just as important radius on the inner transfer duct /bore edge, all contribute.
The scavenging details are actual measurements,that usually are done in research labs, that is where the RS125 details came from.
I dont think that anyone has the measured data from an Aprilia cylinder - but maybe Neels could make an educated guess of the end result.
But in the overall scheme of us being able to predict the result of changes to a specific engine, I dont think many are capable of achieving anything like what resulted from 100 people working
for 10 years, as Frits has described the R&D dept at Aprilia.
Its seems to me that most simulations I do, overestimate the power achievable,thus indicating I am not able to meet the theoretical charging/scavenging efficiency numbers the sim is using.
Having an even better scavenging system would create even more unachievable power in the sim results.
The vast majority of my time is spent optimising the pipe and the intake geometry - the ports are easy, as the STA numbers direct you in the right direction all the time.
If you are short on blowdown the program tells you - you fix it, and get more power - simple,and you can be very sure that the mod you have just done would have worked on an engine , on the dyno, as well.

[dinamik2t]

Ok, that is more than understandable.

Wob, how do you usually handle the combustion efficiency factor?

[Brian d marge]

I think as Lozza alluded to, the issue with the Aprilia scavenging setup is that there are a huge number of details that collectively create a very synergistic whole.
Everything from the radius being discussed here of late to the just as important radius on the inner transfer duct /bore edge, all contribute.
The scavenging details are actual measurements,that usually are done in research labs, that is where the RS125 details came from.
I dont think that anyone has the measured data from an Aprilia cylinder - but maybe Neels could make an educated guess of the end result.
But in the overall scheme of us being able to predict the result of changes to a specific engine, I dont think many are capable of achieving anything like what resulted from 100 people working
for 10 years, as Frits has described the R&D dept at Aprilia.
Its seems to me that most simulations I do, overestimate the power achievable,thus indicating I am not able to meet the theoretical charging/scavenging efficiency numbers the sim is using.
Having an even better scavenging system would create even more unachievable power in the sim results.
The vast majority of my time is spent optimising the pipe and the intake geometry - the ports are easy, as the STA numbers direct you in the right direction all the time.
If you are short on blowdown the program tells you - you fix it, and get more power - simple,and you can be very sure that the mod you have just done would have worked on an engine , on the dyno, as well.

You can quantify experiment with real world data , , the software I use is a good guide thats all ( save a few hours and make feasabiliy studies easier ., what if !!) example I just completed a brake torque arm bracket , and just kept playing around with the shape untill I got it near what I wanted , if I get the new software working , the computer will do that part for me )

BUT it still needs to be buit and tested ,to back up , quantify the computer

Great tools ( the computer ) but ....

Stephen

[wobbly]

Comb Eff I vary depending upon the projected quality of the elements.
Running high com on Avgas with a toroid, in a square engine its up around 92%
Low com on pump with crap chamber shape and oversquare, its down around 82%.
Then lastly I move it around a bit if I have what seems to be too much power, but the curve shape is on the money.
It seems to be a fudge factor that can be used to move all the power up and down, it doesn't change the shape.

Re the computer sims believability factor, I have done so many trips to the dyno and got exactly what the sim said I would that its simply not an issue any more.
Only when reaching the outer limits, such as trying to model an RSA, that depends so much on alot of info we still havnt seen yet ( such as the PWM curve for the powerjets etc),then its a case of crap in = crap out.

[kel]

that depends so much on alot of info we still havnt seen yet ( such as the PWM curve for the powerjets etc),then its a case of crap in = crap out.
speaking of which - from the discussion on the pitlane GP125 all you wanted to know thread, it seems possible Aprilia did not switch off the power jet for over rev as the honda did (well maybe?)

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

On a seperate thread Frits shows the aprilia 100% throttle ignition curve which has noticeably more advance than the Honda at higher revs.

Lot of factors come into play obviously but Im wondering if this is the nature of the Triple port vs the Honda twin port and if its something TZ should consider for his GP125 triple port cylinder i.e. not turning off power jet and more advance in the upper revs at full throttle?

[Haufen]

I am thinking about building a new exhaust pipe.

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

Is there anyone having any experience on this subject?

[wobbly]

The Aprilia had issues with the full throttle shift when in overev,if the engine was tuned correctly for max power and rpm with the powerjet,it would not " slow down " when the ignition cut was
initiated by the riders foot on the shift lever.
The powerjet was used as such in the overev, but I have not seen an ignition curve or powerjet % table to be able to make judgement on what was happening.
A powerjet used with an ON/OFF solenoid can recover a huge amount of lost rpm due to the carb becoming naturally progressively richer past peak power, but PWM controll is able to tailor the fuel delivery
to exactly what is needed for any effect.

I have never had the need to try huge bends in a pipe,Honda have done a U bend in several places on various pipes, but that was the only way to find room, and I doubt they could do
anything about any loss in performance.

[F5 Dave]

. . .
Lot of factors come into play obviously but Im wondering if this is the nature of the Triple port vs the Honda twin port and if its something TZ should consider for his GP125 triple port cylinder i.e. not turning off power jet and more advance in the upper revs at full throttle?
Another factor is use of unleaded race gas vs what we run may make comparisons inconclusive.

[kel]

Another factor is use of unleaded race gas vs what we run may make comparisons inconclusive.

avgas likes more advance so if anything I would guess the effect would be compounded?

[TZ350]

269817 269816

NedKelly and Chambers are having a crack at a F5 50cc stroker.

[F5 Dave]

Good, make sure you all enter the F5 GP next year (if there is a GP arranged).

[F5 Dave]

Good, make sure you all enter the F5 GP next year (if there is a GP arranged).

AM6 I guess.

[SwePatrick]

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

Just a little vid then ;)
http://contour.com/stories/general-lee-audi-speedtest-with-gps

Look at the yellow line to the bottom right in browser.
214.2Mph in an old non aerodynamic Audi 80 quattro from 1984, no wings no nothing to make it slice the air.
Just power, but that day on 'low boost'.
He also ran 9.37 with slipping clutch on 1/4mile.
http://www.youtube.com/watch?v=Ma5NxEMlXrM&feature=youtu.be
Could be an high 8 when clutch can handle the power, never been done thou, so it hasn´t been done.
this car makes about 1000hp at 3.5bar absolute pressure(350kpa)
The 1132hp engine is in Norway, no pics or vids on that car.

this was my own car until recently, no racevids but pics.
https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-ash4/s720x720/380294_10150914723019475_1571785352_n.jpg
day before i sold it:
https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-ash3/s720x720/552556_10150966669374475_1464461987_n.jpg
just a idling video of car:
https://www.facebook.com/photo.php?v=450826304474

I can´t sit and look for hours on internet on old sites just to locate all the dynosheets etc etc.
Those above links a only a few.

and a small vid of me revving my 'nopower honda MB5'
https://www.facebook.com/photo.php?v=10151044778469475
Of course there is NO power gain at all above 8600rpm, all i got is 21,34hp at that rpm, no more.
All else is just a big hoax, i thought everybody understood that.. :Punk:

Yours sincereley
Patrick

[SwePatrick]

what measurement tools are you using for the port flow

Stephen

Actually nothing.. the dyno in the end of enginebuild(or track)
when building,,, well,, i calculate the areas only.
then give it the design i feel should work,, And up to this point,, all of them has worked quite well in dyno or track ;)


Rgds
Patrick

[SwePatrick]

And, wobbly..
I have done alomst the same thing to an lawnmower. ;)
This is my biggest failure.. hehe.

It revved so hard i had to lawn grass to keep engine at lower rpm and full throttle, but i just had it going for about 5minutes.
then it seized and spit out the rod.. *lol*

Rgds
Patrick

[speedpro]

It must be common to hot up lawnmowers. My one was an old iron horse 2-stroke. I drilled out the transfer ports, removed the throttle after it broke, and ran it on 100 octane and acetone and castor oil. Smelt good but you had to mow the lawn fast to stop it overrevving too much.

[Gigglebutton]

I have a Suzuki 2 stroke mower that I have ported, recut the head and fitted a pod filter to. It will only start with Easy Start sprayed in the pod. If you mow in the rain, the pod sucks in water and runs ruff. When its not raining it has loads more grunt & revs a little higher & sound great. I just took it in to work to fix the air filter housing. Thought about making a pipe for it but thats a black art.

[TZ350]

269827 269828 269829 269830

Ok I have been playing with my lawnmower too, its hard to see in the pictures but I have radiused the edges of the exhaust port. Originally it opened 81 deg ATDC, now its radiused up to 78.5 ATDC.

Looking from the top the bottom edge of the exhaust port looks square, but when you look from the bottom you can see the curved shape of the port better.

The width between the cylinder and transfer where the glue is, is 13mm, it was 16 before, but Kel suggested it might be to much. Before I made these changes the 3ex cylinder made an easy 29hp at the wheel, hopefully I will get it onto the dyno soon to see what effect these changes have had, fingers crossed that they will be positive.

[ief]

Is it just the pic or did you 'miss out' on the opportunity to make a nice radius on the inner side (devcon) of the transfer? (seems wide at the bottom so can't see it getting far more wider inside the transfer?)

[TZ350]

269835


Is it just the pic or did you 'miss out' on the opportunity to make a nice radius on the inner side (devcon) of the transfer? (seems wide at the bottom so can't see it getting far more wider inside the transfer?)


269836

Hard to see so well in the first picture. But the devcon comes below the cylinder, as I was trying to form a smooth radiused transition from the inside of the cylinder into the transfer duct. I was also trying to reduce the volume of the transfer duct and have the entry 1.1 times the port window with a big radius right around from the duct entry to the port window.

The inner wall of the duct now looks to thick and has been slimmed down in the top picture. Anyway this triple port cylinder, in spite of having more blow down time area has made less power than the single port so far. And if trimming the devcon in the transfers does not improve things then I probably wont bother on future cylinders and just leave the inner duct wall like Suzuki made them.

269837

[ief]

Guess you went a little overboard there, getting it back to original hight with a better radius then stock... could be benificial... I guess.

That sand linnen stuff used in belt sanders, might be the ticket for the the job, not easy on the fingers tho.

[kel]

The width between the cylinder and transfer where the glue is, is 13mm, it was 16 before, but Kel suggested it might be to much. Before I made these changes the 3ex cylinder made an easy 29hp at the wheel.

Yep thats right I made the leap from test pilot to design consultant with a single crash (hope they realise I took a knock to the head as well :lol:). Whats the saying "hero or zero"?

On a completely unrelated matter, it seems the mighty FXR's have reached their performance/reliability limit - quote Yowling "Yea 4 big ends in 2 weeks,(mat hoogie, hank, josh and bren)"

[FastFred]

...it seems the mighty FXR's have reached their performance/reliability limit - quote Yowling "Yea 4 big ends in 2 weeks,(mat hoogie, hank, josh and bren)"

Then there was that Bike that dropped its inlet valve at the BOB. I am not sure who, but someone on here suggested to Team ESE dropping 2PS or so to improve reliability, the 4-stroke boys might find it worth a go.

[F5 Dave]

Well to be fair (odd as it sounds coming from me) a lot of these 4 bangers are running old parts & at high revs the rods need replacing every-so often. - just people treat 4 strokes like XR250s & just petrol & oil.

That other bike was a GN125 & the best thing that could happen to it. Its been very reliably though (in the garage for 4 year stretches).

[TZ350]

269882

The transfer specs call for a area ratio between transfer port window and tract entry of 1.3:1 (main transfer).

269883

The tripple port cylinder on the right has had the duct entry closed up to a ratio of 1.3, it looks very small to me but the inner radius has a better looking curve to it.



269884

Measured the volumes of the transfer ducts.
Right hand tripple port cylinder with 1.3, 1.2 and 1.1 area ratios
Trans A = 24
Trans B = 16
Trans C = 8
Total = 48cc for all transfer ducts combined.
Left hand single port cylinder
Trans A = 40
Trans B = 20
Trans C = 8
Total = 68cc for all transfer ducts combined.
A lot of the fresh charge must be, being transfered from the crankcase.


Is it just the pic or did you 'miss out' on the opportunity to make a nice radius on the inner side (devcon) of the transfer? (seems wide at the bottom so can't see it getting far more wider inside the transfer?)

269880

I tried to get a more even and better radius like the dotted line with a 1.3 entry area ratio and a nice radius out of the cylinder.

269881

But maybe I need to make it more like this Cagivea cylinder but then I wouldn't have a 1.3:1 entry to port window area ratio ...:scratch:... I must be missing something.

[F5 Dave]

A reed valve?:Pokey:

[TZ350]

A reed valve?:Pokey:

NOoooooo ...... not a reed valve ... :bleh:

[TZ350]

Ok ... re visiting compression testers.

269893

This head has a 1/2" reach plug and the compression tester adapter fills it well so no low comp errors there but it would be a different story if this was a 3/4" reach RG50 head, then there would be a big clearance volume error.

269895

140 psi Compresion tested after reassembly, the cylinder was oily and cold.

269896

130psi Tested hot after a dyno session, I expect this is a truer reading as its what the engine would be like when running.

So about 10lb/psi between cold and oily and dried out and at running temperature.

So now we know ......

[Drew]

Ok ... re visiting compression testers.



This head has a 1/2" reach plug and the compression tester adapter fills it well so no low comp errors there but it would be a different story if this was a 3/4" reach RG50 head, then there would be a big clearance volume error.



140 psi Compresion tested after reassembly, the cylinder was oily and cold.



130psi Tested hot after a dyno session, I expect this is a truer reading as its what the engine would be like when running.

So about 10lb/psi between cold and oily and dried out and at running temperature.

So now we know ......I've got a twin though, so either way as long as conditions are the same both sides it's handy for me as a comparison yeah?

[TZ350]

I've got a twin though, so either way as long as conditions are the same both sides it's handy for me as a comparison yeah?

Yes ... I would think so, it looks like a compression tester used intelligently makes a good diagnostic and comparison tool for keeping an eye on the engines health but its a pretty unreliable way of determining a small engines corrected compression ratio.

[TZ350]

Kel came around tonight and gave me a hand with running the Beast up on the Dyno.

269899

Red line is what we had before we lost the ring locating pin. The Blue line is where we are at after chamfering the exhaust port and opening up the transfer ducts. Chamfering the exhaust port from 81 ATDC to 78.5 will have reduced the volume required in the cylinder head from 9.4cc to 9.0.

So three changes:-
Ex port effectivly opens earlier at 78.5 deg ATDC instead of 81 because of the radius.
Corrected compression ratio is reduced because of the change to the exhaust port timing, head needs CCing.
Bigger entry and reduced inner radius on the main transfer ducts.

Right from the start the engine sounded rich and flat. I am not sure what that means. But I will CC the head and the next chance I get to go on the dyno. I will get the laptop out and have a fiddle with the ignition timing and lean the main jet out a bit.

I am not to unhappy as I think the rich and flat response is because of the porting changes and may be a good sign, I expect it will come right when we get the ignition and carb sharpened up.

[Frits Overmars]

This head has a 1/2" reach plug and the compression tester adapter fills it well so no low comp errors there but it would be a different story if this was a 3/4" reach RG50 head, then there would be a big clearance volume error.There's always a big clearance volume: in the hose. And its effect gets worse the smaller the engine.


... it looks like a compression tester used intelligently makes a good diagnostic and comparison tool for keeping an eye on the engines health but its a pretty unreliable way of determining a small engines corrected compression ratio.Amen to that.

[Frits Overmars]

Corrected compression ratio is reduced because of the change to the exhaust port timing, head needs CCing.
.....Right from the start the engine sounded rich and flat. I am not sure what that means. But I will CC the head and the next chance I get to go on the dyno. I will get the laptop out and have a fiddle with the ignition timing and lean the main jet out a bit.Do yourself a favour, fiddle with the main jet and go to the dyno before changing the head volume.
And forget all about 'corrected' compression ratio. It's an illogical and unworkable concept.

[husaberg]

A long while back i said something to Rob about how the 24mm carb need not be as limiting factor to airflow as people think (well seeing as he has got 30 hp. It turns out its not a limiting as i would have thought anyway)

I said something along the lines that i don't see why the carb has to flow all the air flow for the engine, just some of the air/fuel mix.

Well it turns out, as i always suspected, I very rarely if ever have an original idea.

The URS 500
Which Helmut Fath one the 1968 world sidecar championship aboard well at least when in solo form (the sidecar at times had fuel injection i believe) has a duel inlet system with 4 22mm carbs on a 500 four (which is pretty small for a reputedly 85hp four stroke 4 cylinder.) Late MV 500s had 31mm carbs and the late Bennelli 500/4 was 33mm carbs
The diminutive 22mm carbs were supplemented by air slides that controlled air alone. Well they were in the article i read anyway the later ones might have been bigger
I am assuming the additional air inlet ducts only slides only come into play late in the rev range with the air fuel compensation control by rather large mainjets.
http://www.winni-scheibe.com/images_textbildarchiv/sport/urs/historie/motor_rechts.jpghttp://www.winni-scheibe.com/images_textbildarchiv/sport/urs/historie/45_standbild.jpghttp://www.winni-scheibe.com/images_textbildarchiv/sport/urs/kuhn/zylinderkopf_vergaser.jpghttp://www.winni-scheibe.com/images_textbildarchiv/sport/urs/kuhn/motorzeichnung.jpghttp://www.winni-scheibe.com/images_textbildarchiv/sport/urs/kuhn/kopf_kolben.jpghttp://www.winni-scheibe.com/images_textbildarchiv/sport/urs/kuhn/kopf_vergaser.jpghttp://www.kradblatt.de/fahrberichte/oldtimer/images/muench_urs_2.jpg

If you are struggling to see it look on top of the engine.
So whip up one of these systems over smoko will you Rob:msn-wink:


EILE MIT WEILE

[ief]

269880

I tried to get a more even and better radius like the dotted line with a 1.3 entry area ratio and a nice radius out of the cylinder.

269881

But maybe I need to make it more like this Cagivea cylinder but then I wouldn't have a 1.3:1 entry to port window area ratio ...:scratch:... I must be missing something.

I guess the 1.3:1 ratio is only part of the equation and duct volume is another and my guess is that the latter is being compromised to much now. If I understood Jan correct then the more volume crated at the top of the duct allways improved things...

Compromises, yet again :)

And while I'm thinking out loud here... The shape of the duct is from smallisch to big on the rsa and I wonder if that could have anything to do with blowback having less influence then (?)

[Buckets4Me]

So whip up one of these systems over smoko will you Rob:msn-wink:


EILE MIT WEILE

:shutup::facepalm::corn::blink::shit: you know he will try :no:

[wobbly]

The trend has been for a long time to reduce the volume of all the ducts in modern engines.
Aprilias Ex duct had the bottom filled in such that it was higher than BDC and the corners filled to reduce short circuiting from the A ports.
And the cylinder duct vol was CNC machined to be smaller and smaller in total vol,but in the process heavily promoting flow from the Aux ports to increase effective blowdown flow.
One of the transfer duct entrys was smaller than the port area ( the B and biggest port ) and for sure the ratio between the A and B port duct entry areas was tested
to death within the limitation of the case available area between the studs, by several of the 100 R&D festerers.
The idea here is to reduce the inertia of the initial volume available to the cylinder,that has to be accelerated out of the duct by the negative pressure ratio across the port.
That Cagiva cylinder is very "old" technology.

[ief]

Ehm, not sure if I get all that but none the less, how would that translate to TZ and his devconned barrel?

[wobbly]

TZs devconed cylinder had HUGE area of the A transfer duct at its entry, I pointed this out ages ago and suggested that the outer wall should be filled
to reduce the duct vol and smooth the entry flow.
But that would involve filling the case as well to match it, so he filled the inner radius as it was alot simpler.

[F5 Dave]

Ok ...

140 psi Compresion tested after reassembly, the cylinder was oily and cold.



130psi Tested hot after a dyno session, I expect this is a truer reading as its what the engine would be like when running.

So about 10lb/psi between cold and oily and dried out and at running temperature.

So now we know ......

So now we know what?:blink:

That they are a pretty coarse tool? The comparison is still of unknown variability.

Presumably the ring seal should be better after the bike was run-in (to an unknown quality). You should have tested it once it was cold after run-in to draw any conclusion, but even then you don't know how much oil has settled & got thrown onto the bore seal. I think the only thing it proves is that "results may vary"

[ief]

@wob #9050

Ok, that I get but... it seems it didn't help, in the contrary.

So I opted to rethink the choices made... still do I'm afraid.

Or..it has nothing to do with the devcon at all then all this is ehm... useless :innocent:

[TZ350]

So now we know what? ... :blink:

Wait for it .......


That they are a pretty coarse tool ... comparison is of unknown variability ... it proves that "results may vary"

Just like you and Wob said, "results may vary" ..... :laugh:

[TZ350]

TZs devconed cylinder had HUGE area of the A transfer duct at its entry, I pointed this out ages ago and suggested that the outer wall should be filled to reduce the duct vol and smooth the entry flow. But that would involve filling the case as well to match it, so he filled the inner radius as it was alot simpler.

Ok, that I get but... it seems it didn't help, in the contrary.

To early to say, all that can be said, is with the mixture going rich, that the latest simple changes have had quite an effect on the carburation.

269961

The loss of power is consistant with an overly rich mixture. I will sort that, then see where we are, with good carburation it may make more power than it did before.

[ief]

Oops, where did I come to this assumption then?

:facepalm:

Must have misread some previous posts then, ma bad, just wait and see what comes out then all though I still can't shake the idear the shape/ radius could be improved upon but who knows ai?

Carry on :Police:

[kel]

The trend has been for a long time to reduce the volume of all the ducts in modern engines.
The idea here is to reduce the inertia of the initial volume available to the cylinder,that has to be accelerated out of the duct by the negative pressure ratio across the port.

Agreed. Everything we know (which for myself comes from what I've read rather than proven) tells us that Devcon in the transfer will produce more power, its just a matter of finding the right combination of area, inner radius, inner wall width etc.


Or..it has nothing to do with the devcon at all then all this is ehm... useless :innocent:

Im confident we are on the right track as the bike sounded horribly flat yet still produced 27.5hp. Correct jetting, ignition timing and possibly compression and TZ's heading over 30hp! Watch this space.

[TZ350]

Im confident we are on the right track as the bike sounded horribly flat yet still produced 27.5hp. Correct jetting, ignition timing and possibly compression and TZ's heading over 30hp! Watch this space.

Hopefully get a chance to run it up again tonight ......

[Brian d marge]

Agreed. Everything we know (which for myself comes from what I've read rather than proven) tells us that Devcon in the transfer will produce more power, its just a matter of finding the right combination of area, inner radius, inner wall width etc.



Im confident we are on the right track as the bike sounded horribly flat yet still produced 27.5hp. Correct jetting, ignition timing and possibly compression and TZ's heading over 30hp! Watch this space.

Why don’t you try openFoam CFD , its free and in 2d not so bad to use , will give you a good idea of the flow

Stephen

[FastFred]

Why don’t you try openFoam CFD

http://www.openfoam.com/features/mesh-manipulation.php
https://sites.google.com/site/engcalculusev/openfoam-examples
http://openfoamwiki.net/index.php/2D_Mesh_Tutorial_using_GMSH

openFoam Tutorial ... plenty on the net about openFoam

[TZ350]

Im confident we are on the right track as the bike sounded horribly flat yet still produced 27.5hp. Correct jetting, ignition timing and possibly compression and TZ's heading over 30hp! Watch this space.

Kel and I finished off last night pretty sure it was rich.

269990

The target is 30+hp with the more reliable exhaust port width of 70-72% instead of 75.

Ok ... last time on the dyno the Beast sounded very flat and rich and only made 27.5 hp it has done better, so I changed the mainjet from a 135 to a 125 and the pilot from 38 to 32 and ran it up again.

269989

Ooops the power started falling off with each consecutive run. The last time I saw that the new piston in NedKellys bike had cracked and was about to disintegrate.

I felt pretty down thinking there was a problem and the night was done. I was not looking forward to pulling the cylinder off to see what had gone wrong. Bummer .....

But wait, I have a "compression tester" and know what the motor should read hot because I was smart enough to check it before when it was good.

I guess if I hadn't done that I would have had to pull it down to find out there was nothing wrong.

269988

Turns out it needed to be richened up, go figure, because it sure sounded rich before. Changed the main to a 145 and pilot to 42 and gained 2hp. Fiddling with the ignition didn't do anything but bring on det. So not 30+ yet and still sounds flat so I will look at the compression ratio next.

[Frits Overmars]

The trend has been for a long time to reduce the volume of all the ducts in modern engines. Aprilias Ex duct had the bottom filled in such that it was higher than BDC and the corners filled to reduce short circuiting from the A ports. And the cylinder duct vol was CNC machined to be smaller and smaller in total vol,but in the process heavily promoting flow from the Aux ports to increase effective blowdown flow.True, true, Wob. Except, how do you machine a duct smaller :whistle:?


... for sure the ratio between the A and B port duct entry areas was tested to death within the limitation of the case available area between the studsTrue again.


The idea here is to reduce the inertia of the initial volume available to the cylinder,that has to be accelerated out of the duct by the negative pressure ratio across the port.Here our opinions seem to differ. The mass of a gas column in a duct equals specific mass * duct length * duct cross area (let's assume for now that the area is constant over the duct's length). You want to get that mass into the cylinder in a given amount of time and that requires a certain flow velocity. This velocity is inversely proportional to the cross area. And the required pressure difference is proportional to the square of the velocity. So, though a longer duct will slow down the mass transfer, a larger cross area will help.

Where the charge goes, is another matter. It would be quite easy to enhance transfer flow by aiming the leading edges of the A-ports more towards the exhaust port, but that would cause massive short-circuiting. When looking at the inner duct curves of TZ350's cylinder, that thought crossed my mind...

[TZ350]

So, though a longer duct will slow down the mass transfer, a larger cross area will help. Where the charge goes, is another matter. It would be quite easy to enhance transfer flow by aiming the leading edges of the A-ports more towards the exhaust port, but that would cause massive short-circuiting.

269993

When looking at the inner duct curves of TZ350's cylinder, that thought crossed my mind...

Yes, actually hadn't realy noticed that before.

269995

The idea was to have a better curve with a bigger radius from inside the cylinder to the port window with a 1.3 entry area ratio. The area around the port window itself does not have any glue near it, so I just assumed that the port would still discharge in the same direction as before, but maybe not.

The single port cylinder on the left made 31hp so I am tempted to remove most of the glue from the transfers or at least heavily re shape it.

[wobbly]

I am sure that changing the Exhaust duct core size in the casting was an easy task at the factory,so that subsequently the nicely finished CNC machined area was able to be made progressively smaller and smaller
to good effect.

The second point is explained by your small add on comment - "mostly" the ducts are not constant cross section,the CSA gets progressively larger toward the entry point.
My small observation was that the trend has been to reduce that area at the entry to the duct, thus reducing the total volume, and thus the inertia of the volume total within that duct.
As always im gun shy of arguing with you Frits as you are easily capable of helping me shoot myself in the foot, even if I cant feel it.

[Haufen]

So the reduction in cross sectional area at the bottom of the RSA exhaust port works like an integrated oval to round transition?

Do you remember the percentage of the reduction in cross sectional area, Frits?

270001

[speedpro]

I wonder if "inertia" is the right word to use when referring to the fluid in the transfer ports. For the same density the inertia of a fluid will be constant. With a larger volume port there will be a larger volume of fluid which if it was all to be accelerated at the same rate as the smaller volume would require more energy due to the greater mass being accelerated. However with a larger volume would all the fluid be required to accelerate at the same rate as the smaller volume? If the port window is unchanged at any moment in comparison to the larger and smaller volume ports there should be a similar amount of energy available to accellerate the fluid in the port as it is the differential in pressure at the port window that determines the energy available to accelerate the fluid.

For any given duct volume or cross-sectional area the energy level will be similar. Whether that results in a lot of fluid moving slowly or a smaller amount moving at a higher velocity will be dependant on the port volume or cross-section. Given the constantly varying everything there won't be one perfect configuration for "every" scenario. There will surely be an optimum configuration for a particular operating condition and desired outcome. A smaller port would result in a higher velocity which could be useful as the port closes to jam a bit more into the cylinder, due to inertia.

:wait: sits back and waits to be shot down

[Frits Overmars]

...As always im gun shy of arguing with you Frits as you are easily capable of helping me shoot myself in the foot, even if I cant feel it.I'm glad to have you as a sparring partner, Wob. It forces me to think a bit harder before hitting my keyboard. And feel free to aim at my feet anytime :shifty:.



So the reduction in cross sectional area at the bottom of the RSA exhaust port works like an integrated oval to round transition? Verstehe nur Bahnhof, Haufen.
Do you remember the percentage of the reduction in cross sectional area, Frits?I am still in a place far, far away (Dresden) and I have no access to my home archive; I only remember that the entry area of the B-ports is a trifle under their exit area. That is not something you should aim at (on the contrary); it evolved historically because Aprilia wished to keep the cylinder stud positions in their original place, so new cylinders would fit old engine cases. The RSA125 should have been free from that restriction because it was designed at Derbi, not at Aprilia. But in the development phase it was decided to fit an existing well-proven Aprilia cylinder, so the funny entry/exit relation remained.


I wonder if "inertia" is the right word to use when referring to the fluid in the transfer ports. For the same density the inertia of a fluid will be constant. With a larger volume port there will be a larger volume of fluid which if it was all to be accelerated at the same rate as the smaller volume would require more energy due to the greater mass being accelerated. However with a larger volume would all the fluid be required to accelerate at the same rate as the smaller volume? If the port window is unchanged at any moment in comparison to the larger and smaller volume ports there should be a similar amount of energy available to accellerate the fluid in the port as it is the differential in pressure at the port window that determines the energy available to accelerate the fluid.

For any given duct volume or cross-sectional area the energy level will be similar. Whether that results in a lot of fluid moving slowly or a smaller amount moving at a higher velocity will be dependant on the port volume or cross-section. Given the constantly varying everything there won't be one perfect configuration for "every" scenario. There will surely be an optimum configuration for a particular operating condition and desired outcome. A smaller port would result in a higher velocity which could be useful as the port closes to jam a bit more into the cylinder, due to inertia.
:wait: sits back and waits to be shot downI'm not aiming at your heart, Speedpro, only at your foot (learned that from Wobbly). It makes a difference whether all of the fresh charge has to come from the crankcase, or whether it is already waiting just outside the transfer windows, as is the case with large-volume ducts. These ducs themselves can then be refilled at leisure between transfer phases.

I will counter your final remark "A smaller port would result in a higher velocity which could be useful as the port closes to jam a bit more into the cylinder, due to inertia" with a quote of your own: "it is the differential in pressure at the port window that determines the energy available to accelerate the fluid".
The flow velocity is pressure-dependent, not port-area dependent (otherwise a closed port would give an infinite velocity:weird:). This velocity will only rise somewhat higher in a narrow duct because the smaller mass transfer through it will result in a slower pressure drop, therefore in a prolonged time during which the mass is accelerated.
Using the jamming effect, or RAM effect as the Mericans call it, is just an attempt to correct in the end phase of transfer (or intake) what went wrong at the beginning.

[crazy man]

l feel the love in here:innocent:

[Frits Overmars]

l feel the love in here:innocent:I hope Speedpro does too. It is never my intention to cut someone down to size; that would not make me look any taller.

[TZ350]

Having managed 29hp with the taper bored 24mm OKO I wanted to see what difference a bigger carb might make. The taper bored OKO is 31mm at the engine flange so I bored another OKO out to 30mm at the slide and 31 at the flange.

Set the 30mm carb up with a main jet one size bigger than the 24 and ran it up. It started and warmed up ok but when I tried to move up through the gears it wouldn’t accelerate.

Anything over half throttle and it just sat there going Blarrrr, sounded rich but I was caught out thinking that the other night. If it was lean I would have expected it to just cut out, it kept going but no matter what I did with the throttle it just would not pickup, sounded flat and rich.

The taper bored 24 had a 145 main, the 30 a 150 so it’s hard to imagine the 30 needing a main smaller than the 24. ???? ran out of time to look into it. I didn't think of it at the time but I should have pulled the power jet feed line off. Killing the power jet would have quickly told me if it was rich or lean.

Kel and I now think the flat sound to the exhaust is due to the top exhaust port chamfer blunting the exhaust note as the port is no longer cracking open suddenly, is that a good thing ???.

[speedpro]

I will counter your final remark "A smaller port would result in a higher velocity which could be useful as the port closes to jam a bit more into the cylinder, due to inertia" with a quote of your own: "it is the differential in pressure at the port window that determines the energy available to accelerate the fluid".

As the time the port closes though the fluid has already been accelerated and is now being decellerated by a port window that is reducing in size and thus restricting potential flow. That energy in the moving mass doesn't disappear but could in certain situations result in a pressure differential rise at the port window resulting in flow continuing.

I see your point about the duct holding the volume ready to flow through the port, a sort of mini plenum. However I also envisage an optimum size duct providing the volume of fluid to move through the port with little restriction at the start of the transfer while also providing a column of fluid which is moving with some velocity to facilitate flow towards the end of the transfer phase.

I don't have the knowledge though to determine if a large slow moving volume would be better in that situation or a smaller faster moving volume.

I compare it to velocity stacks on a dirty 4-stroke engine though I think it's a bit easier to visualise on a 4-stroke. Once that air is moving into the velocity stack it wants to keep moving even though the valve is closing or the piston has started up on the compression stroke. As in our lovely 2-stroke engines transfer ports, there is an optimum length and diameter(volume) for the application and tune of the engine.

[Frits Overmars]

...Kel and I now think the flat sound to the exhaust is due to the top exhaust port chamfer blunting the exhaust note as the port is no longer cracking open suddenly, is that a good thing ???.
If you only added a chamfer to the existing port, outflow will improve, waisting less energy in turbulence and sending more energy the pipe. It will also have raised the exhaust timing, opening the port when cylinder pressure is higher; another reason for the pipe to perform better.
I have met people who claimed they could tell just by listening whether an engine had auxiliary exhaust ports or a T-port. All I can hear is whether the silencer is still silencing or needs to be repacked.

Funny sounds can turn up if the ignition is borderline. Improving the cylinder filling can be enough to prevent the spark from sparking at the right time every time.
A simple test is to close the plug gap to 0.2 to 0.3 mm. If that improves things, you need a stronger ignition.

[RAW]

I am still in a place far, far away (Dresden) and I have no access to my home archive; I only remember that the entry area of the B-ports is a trifle under their exit area. That is not something you should aim at (on the contrary); it evolved historically because Aprilia wished to keep the cylinder stud positions in their original place, so new cylinders would fit old engine cases. The RSA125 should have been free from that restriction because it was designed at Derbi, not at Aprilia. But in the development phase it was decided to fit an existing well-proven Aprilia cylinder, so the funny entry/exit relation remained.


Frits I can't quite see what your meaning here, do you have any photos of the Derbi cylinder or something along these lines we could all view

Cheers:corn:

[Frits Overmars]

As the time the port closes though the fluid has already been accelerated and is now being decellerated by a port window that is reducing in size and thus restricting potential flow. That energy in the moving mass doesn't disappear but could in certain situations result in a pressure differential rise at the port window resulting in flow continuing.True. But that energy first has to be put into that mass. The longer the gas column and the higher it has to speed up, the slower will be the initial cylinder (or crankcase) filling. That was what I meant by 'correcting at the end what went wrong at the beginning'.
Utilizing ram effects requires long timings, and vice versa. But the shorter you can keep your timings, the more user-friendly the engine will be (exhaust timing partly excluded because you need a certain minimum timing for resonance).

[Frits Overmars]

Frits I can't quite see what your meaning here, do you have any photos of the Derbi cylinder or something along these lines we could all viewThere is no Derbi cylinder, RAW. That is, before Jan Thiel moved to Derbi to build the RSA engine, there had been Derbi reed valve racing engines, but their cylinders (and pipes) were exact Honda copies. The cylinder on the RSA has been an Aprilia pot from the beginning. I posted several zip-files here on the forum with lots of Aprilia engine details. You'll just have to do some searching.

[Neal]

270001[/QUOTE]


Hi Haufen ,

where did you get this picture from ? Are you casting your own barrel ?

[wobbly]

I believe the big radius at the bore centre line has two effects.
Firstly is to improve the bulk blowdown flow at low opening angles of the piston controlled port orifice, due to the gas attaching early to the roof.
Secondly the exiting wave amplitude is lowered and smoothed out by the gradual ( instead of a sharp edge ) port opening.
This would improve the scavenging action bandwidth, but the peak value is probably then raised as well,simply because the port opens earlier when the pressure above the piston is greater.
Thus you get the best of both, a wider effective scavenging action, combined with a higher peak value, making the pipe work better over a wider range.

The big radius can only be applied to a port with the chrome removed, it then has to be replated to permit the ring to run on a hard surface as it bulges out into the port - unless of course you have an iron bore..

[TZ350]

If you only added a chamfer to the existing port, outflow will improve ...

Chamfer and a little enlarging of the transfer port entry, no other engine or ignition changes at all and after changing the main jet from 135 to 145 the power on the dyno is up, from 27 to 29.


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


I believe the big radius at the bore centre line has two effects. Firstly is to improve the bulk blowdown flow at low opening angles of the piston controlled port orifice, due to the gas attaching early to the roof. Secondly the exiting wave amplitude is lowered and smoothed out by the gradual ( instead of a sharp edge ) port opening. This would improve the scavenging action bandwidth, but the peak value is probably then raised as well,simply because the port opens earlier when the pressure above the piston is greater.

Thus you get the best of both, a wider effective scavenging action, combined with a higher peak value, making the pipe work better over a wider range.

OK so the top of the exhaust port chamfer is a good thing.


I have met people who claimed they could tell just by listening whether an engine had auxiliary exhaust ports or a T-port. All I can hear is whether the silencer is still silencing or needs to be repacked.

This sound change is not a subtle thing that only I can hear, even people here in the workshop who have no real interest in tuning 2-strokes say they notice it, to them my bike now sounds like a FXR150, 4-stroke flat, fat and lazy not the typicall sharply tuned 2-stroke exhaust note.


Funny sounds can turn up if the ignition is borderline. Improving the cylinder filling can be enough to prevent the spark from sparking at the right time every time. A simple test is to close the plug gap to 0.2 to 0.3 mm. If that improves things, you need a stronger ignition.

Thanks for the tip, I will try closing the plug gap and also Wob has pointed out that my Ignitec has two channels and I could connect both of them to the coil for extra umph in the spark department. Wob has also sold me a special plug, it would be wasted trying it now, but when the engines running properly I will try it in a Back to Back dyno run.

The triple port cylinder has Exhaust and Transfer STA's capable of easy mid 30's rwhp so at 29 something is holding it back.

[Haufen]

Chamfer and a little enlarging of the transfer port entry, no other engine or ignition changes at all and after changing the main jet from 135 to 145 the power on the dyno is up, from 27 to 29.

Well then, sounds like a 155 is worth a try!


270001


Hi Haufen ,
where did you get this picture from ? Are you casting your own barrel ?

hi Neal,

these are not my sand cores. But it would be nice if they were :yes:. I found that picture somwehere on the net, could have been pit-lane.biz. The picture illustrates what I was trying to describe using words (but did not succeed). Look at the curved shape of the main exhaust port floor, there seems to be a reduction in area within the port.



Verstehe nur Bahnhof, Haufen.I am still in a place far, far away (Dresden) and I have no access to my home archive; I only remember that the entry area of the B-ports is a trifle under their exit area. That is not something you should aim at (on the contrary); it evolved historically because Aprilia wished to keep the cylinder stud positions in their original place, so new cylinders would fit old engine cases. The RSA125 should have been free from that restriction because it was designed at Derbi, not at Aprilia. But in the development phase it was decided to fit an existing well-proven Aprilia cylinder, so the funny entry/exit relation remained.



Thanks Frits. What I was referring to was a post from wob a couple (of hundred) pages back where he writes about having the exhaust port area at the exhaust flange about 75% of the value at the bore to gain horsepower.



All modern race engines have a nozzle restriction at the flange face, as big T ports and tripple Exhausts loose alot of velocity going into the header.
Rule of thumb is a 75% of the effective EX area at the flange.
Stepped oval duct into a round flange does work, but I have used a CNC oval to round transition in the spigot for years, as has Honda in A kit, and Aprilia factory engines, this works way better.
Here is a sim showing my new 400cc F3 engine, with and without the spigot nozzle.


And I was wondering if the exhaust port floor of the rsa was shaped the way it is to achieve the same thing. And if it was, if the value was about 75% also, or if another value gave better results.

[F5 Dave]

. . .
Anything over half throttle and it just sat there going Blarrrr, sounded rich but I was caught out thinking that the other night. If it was lean I would have expected it to just cut out, it kept going but no matter what I did with the throttle it just would not pickup, sounded flat and rich.

The taper bored 24 had a 145 main, the 30 a 150 so it’s hard to imagine the 30 needing a main smaller than the 24. ???? . . .
Its very easy to imagine it, same amount of suction but bigger hole. Less velocity, less signal. Best to always start off rich though. It can often catch you.

[2T Institute]

270001


Hi Haufen ,

where did you get this picture from ? Are you casting your own barrel ?[/QUOTE]

I got that pic from a Italian contact, his partner has the laser sintering machine to build these casting cores. IIRC he did most of the work for Aprilia. The 'lamp stand' as I called it is the voids in a casting, fits together with the cooling passage core and the outer shell. When placed together and cast voila a APE cylinder.

Wob I radiused a Stihl chainsaw cylinder(a bloody expensive one) revs to the moon with no replate and (touch wood) ring issues yet.

[wobbly]

Yea but Lozza was it a R3,5 and was the port at 70 + % and did it pull 14500,or even closer to the moon.

The curved convex shape of the Aprilia duct corresponds directly with the area increasing due to the Aux ducts entering the main.
Again the idea is to keep the duct volume down.

The 75% area at the cylinder exit is just something I discovered after running hundreds of sims, most of them worked best with an oval to round transition in the flange that started with this area
and the pipe header diameter equalled the total effective area of the ports.
Its been tested and proven so many times now, by so many other people, that it should be the first mod to make to any T or tripple port engine.
Here is a pic of one I have just done, that happened to have a tapered spigot - enabling the Aux ducts to be run all the way down into the pipe.
Check the big rad on the transfer duct/bore edge.

[SwePatrick]

The taper bored 24 had a 145 main, the 30 a 150 so it’s hard to imagine the 30 needing a main smaller than the 24. ???? ???.

This isn´t an exact knowledge actually.
This is directly related to the airspeed through the carb.

Higher speed draws more fuel from main jet(all others too infact)

Example, on my build.
I had 200 in main jet(keihin jet) inside my Mikuni TMX 40(bored out 38mm).
that one had problems with overflowing so i changed to an TM36.
I set that one up exactly like the 40mm just jetted it down to 185, but engine ran so rich i had to jet it down all the way to 160.

Of course there is an area change, that´s why i jetted it down to 185 to compensate for that.
When ending up on 160 i thought it can´t be making any power as it´s alomst the same as my 88cc build, that one has 145 in main.
But when testing it,, it still makes HUGE amount of more power than my 88cc build.

Here in Sweden we also say that if you are having to jet your carb insanely big your pipe is wrong.

With alls this said, i just wanted to state that jetting can be mindgobbeling, and just ignore it, follow your gutfeeling.

Rgds
Patrick

[F5 Dave]

. . .and just ignore it, follow your gutfeeling.. .
and the testing results.

[speedpro]

OK, I do have a big carb at 34mm on a 100cc motor. It has a 430 main, proven on the dyno to make best power. Someone else can check with Wobbly whether the pipe is right.

[teriks]

This sound change is not a subtle thing that only I can hear, even people here in the workshop who have no real interest in tuning 2-strokes say they notice it, to them my bike now sounds like a FXR150, 4-stroke flat, fat and lazy not the typicall sharply tuned 2-stroke exhaust note.
My 250sx recently did just that, a new plug with correct gap cured it. -Just to add to Frits thoughts on the ignition perhaps beeing the cause in your case.

[FastFred]

This sound change is an interesting one as by all accounts its making as much power or a little more so its not an engine that's gone off song.

[teriks]

This sound change is an interesting one as by all accounts its making as much power or a little more so its not an engine that's gone off song.
Imo thats well in line with
Funny sounds can turn up if the ignition is borderline. Improving the cylinder filling can be enough to prevent the spark from sparking at the right time every time. A simple test is to close the plug gap to 0.2 to 0.3 mm. If that improves things, you need a stronger ignition. Witch makes sense since the electric breakdown strength (or resistance to sparking) of a gas is ~proportional to it's density (that is not the case for the breakdown strength along the insulator surface though).

[SwePatrick]

OK, I do have a big carb at 34mm on a 100cc motor. It has a 430 main, proven on the dyno to make best power. Someone else can check with Wobbly whether the pipe is right.

Sarkasm?
Anyway.. i figure you are running mikuni jets..
If so,, just a dumb statement again.
as Keihin measures in 1/100mm
and Mikuni some 'flownumber'

How should i express myself?,, 'Geez' maybe? *lol*

Rgds

[dinamik2t]

Check the big rad on the transfer duct/bore edge.
Here is a pic of one I have just done, that happened to have a tapered spigot - enabling the Aux ducts to be run all the way down into the pipe.

Extra nice Wob!
(the path from C to B tfr entry is 'aftermarket'? This was also in the KTM 50 cylinder, wasn't it? it's a reed valve trend?)

In the tripple port exit, do you calculate .75 area with or without the aux 'cheeks'?
The old RSW drawings Frits provided, have the main oval ~39x31.5, plus a R11 for the aux's. While the 'main' exit is about .75, the total 'main+aux' exit exceeds that number quite much.

270085

[Frits Overmars]

Chamfer and a little enlarging of the transfer port entry, no other engine or ignition changes at all.No kidding. Man, it's a different engine now!

[wobbly]

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

[2T Institute]

Wob the Stihl pulls a good 10,000(TL 680mm)under load cutting a 18in hardwood log, ex width is low 60% as the piston has large cut aways around the pin. I got the largest rad I could(about 2.5mm) with a 60mm bore and a integral head, working from the bottom and through the ex duct.

[dmcca]

Wob the Stihl pulls a good 10,000(TL 680mm)under load cutting a 18in hardwood log, ex width is low 60% as the piston has large cut aways around the pin. I got the largest rad I could(about 2.5mm) with a 60mm bore and a integral head, working from the bottom and through the ex duct.
Sounds interesting, any pics or vid of it in action?

[TZ350]

With the triple port cylinder which has a main exhaust port 72% wide and with the 24mm carb on the left we have managed a best of 29hp, we have done better 31hp with a single exhaust port 75% wide which had less STA so something else is holding it back.

Maybe the restrictive 24mm carb regulation is starting to bite and its time to look at the plenum again.

270121

The regulation 24mm carb made 29hp, now it would be interesting to see if we can make more power with a bigger carb. Next week I hope to try the 30mm carb in the middle and if that makes more power then I will re visit the 24mm plenum idea.

The plenum idea is a way to get around the restriction of a 24mm carb. Basically the plenum is feed by the 24mm carb and the engine draws from the plenum through a 30mm inlet tract.

On WOT the 24mm carb can flow into the plenum full time while the motor only sucks from the plenum for half the time. So the 24mm carb could effectively pass twice the air to the engine than it normally would.

270122 270123

The 30mm plenum runner has a butterfly for varying the inlet runner area and inlet timing. It basically halves the runners diameter and effectively closes the inlet 10 deg earlier. EngMod2T simulations suggest that there may be some useful low-end torque to be had.

The butterfly valve is operated by a small model aeroplane servo. http://youtu.be/FeB9O6rtLXQ

A previous problem we had was fuel dropout and puddling affecting the fuel mixture. The plenum has been sculpted with Devcon putty so everything drains to a low point and a scavenge pump removes the waste fuel/oil.

When we first tried it, start up was easy. http://youtu.be/YxiEo8cgopg then a bit of a blits up the drive. http://youtu.be/p4ef-WUO1Qs When the team first posted this, someone pointed out that a first gear run up the drive didn't prove much, they were right, but it proved it ran. I guess they were focused on the negative and didn't have the wit to see the possibilities.

We also ran it around the track at Mt Welly and it went OK but track testing was stopped when we realized that more oil than fuel was dropping out which meant that lubrication was a bit doubtful. There are a few oiling ideas like re fitting the auto lube pump or drip feeding oil directly to the plenums runner.

270120

Anyway if it doesn't work out the plenum chamber makes a handy catch tank for the carburetor.

[TZ350]

<iframe width="560" height="315" src="http://www.youtube.com/embed/2fUvgwsJkm4" frameborder="0" allowfullscreen></iframe>

I don't know who the rider is but its a Suzuki GP125 running at the Greymouth Bucket races.

[Frits Overmars]

The idea is a way to get around the restriction of a 24mm carb. Basically the plenum is feed by the 24mm carb and the engine draws from the plenum through a 30mm inlet tract. On WOT the 24mm carb can flow into the plenum full time while the motor only sucks from the plenum for half the time. So the 24mm carb could effectivly pass twice the air to the engine than it normally would.Indeed. Nevertheless, you should pay attention to the flow through that carb because plenum pressure will drop during the inlet phase and you want to keep that drop as small as possible.
From what I can see, the tract length between the carb and the plenum is quite large, and so is the inertia of the mixture column in it. Though the flow through it is more or less constant, which lessens the inertia's influence, shortening it won't hurt. It will also create more room for an air filter (or should I say vacuum cleaner bag?).


The 30mm plenum runner has a butterfly for varying the inlet runner area and inlet timing. It basically halves the runners diameter and effectivly closes the inlet 10 deg earlier. EngMod2T simulations suggest that there may be some useful low-end torque to be had.Maybe, but the inflow at the butterfly body looks terrible. I would suggest losing the whole butterfly body and fitting a short, well-rounded bell mouth instead. The better shape and reduced column inertia will promote max.power and overrev. Moreover you may be able to close the inlet earlier which will give you back your low-end torque and simplify setting the carburation. And you will have one less servo system. You know my view on construction in general and on racing equipment in particular: every part that you can leave out, doesn't cost anything, doesn't weigh anything, and never breaks down.

By the way, a 30 mm carb may sound large to you folks, but over here we run 32 mm carbs on 50 cc engines, and they behave quite civilized with them (and make some power as well).

[TZ350]

Thanks for the tips, I have a shorter belmouth to try, changing the rotary valve is a bit of a bother as I have to take the clutch off to do it, it takes about an hour to swap a RV, I will try your suggestions but it will take a few sessions to try a few different RV's.

[Frits Overmars]

Thanks for the tips, I have a shorter belmouth to try, changing the rotary valve is a bit of a bother as I have to take the clutch off to do it, it takes about an hour to try a RV, I will try your suggestions but it will take a few sessions to try a few different RV's.No rush. I have ongoing projects that started 30 years ago :D.

EDIT: Maybe I can give you some pointers.
Closing the valve at 75° aTDC will give reasonable power and a friendly engine. Exceeding 85° aTDC may make the engine bad-tempered.
Trying disks with 75°, 80° and 85° will get you in the ballpark. I wouldn't bother trying intermediate values.

[ief]

I was curious so I thought I'd sim the triple port and lost power as well (just added aux ports to the single port setup and made the main port 72% and gave it a bigger radius) Then I lowered the ports a couple degrees and presto, power was back but...

With the triple ports the peak seems to go up the rev range and I don't see that in your runs and I wonder why?

I know I'm just messing about since the data is a guesstimate but still.

Also I wonder, your saying something else must be holding you back but wouldn't it to be expected that if the single port made 30+ hp the triple should be able to do that as well? I just don't see how something could be holding it back all of a sudden? Or if it does it seems something is just wrong?

[TZ350]

I was curious so I thought I'd sim the triple port and lost power as well (just added aux ports to the single port setup and made the main port 72% and gave it a bigger radius) Then I lowered the ports a couple degrees and presto, power was back but...

With the triple ports the peak seems to go up the rev range and I don't see that in your runs and I wonder why?

Yes, its suspicious ...

The way the side ports have been cut into the cylinder may be not so good and they don't flow as well as they should, its possible the triple does not have the STA I imagin.


your saying something else must be holding you back but wouldn't it be expected that if the single port made 30+ hp the triple should be able to do that as well? I just don't see how something could be holding it back all of a sudden? Or if it does it seems something is just wrong?

Yes, looking at the EngMod STA figures I expected the triple to easily make the same or more than the single port.

Everything else about the engine is the same except the glue in the transfers, the way I have gone about that may be whats wrong, its what I suspect anyway.

[ief]

Well, had a couple of hours fun with it and here are the results:

Little intro, when i got the files from you first thing i did was to detune it to get some figures more in line with your dyno runs, then i fiddeled around with the exhaust to see what i could get. Bin a while and i didn't save all the stuff but the red line is what i got i think. (if i remember correctly it was with an adapted early rs exhaust)

To make a long story short, i found that, with the triple exh. lowering the exhaust made better power witch to me suggests you'r loosing to much of the powerstroke now. Tried some different exhausts (adjusted them step by step) and ended up on the green line, about 3 hp more and lower in revs...

Witch brings me to your previous statement, it could be very well that your right that something is holding you back to get more power at higher revs, in the sim i am able to produce more power but at lower revs.

ps. I didn't change anything other then the exhaust and exhaust port between the triple and single port, well, except for recalculating the head.

For what it's worth and all that, if you like I can sent you the files, perhaps you can distill anything out of it.

edit: afterthought, lets see what this exhaust does on the single ex port. Was all most afraid it was all due to the exhaust but it seems the triple ports did something, pffffffff :rolleyes:

[jasonu]

every part that you can leave out, doesn't cost anything, doesn't weigh anything, and never breaks down.

That is the quote of the century!!!!!

[Frits Overmars]

That is the quote of the century!!!!!The century is still young, but thanks anyway, Jasonu.

[TZ350]

... i found that, with the triple exh. lowering the exhaust made better power witch to me suggests you'r loosing to much of the powerstroke now. Tried some different exhausts (adjusted them step by step) and ended up on the green line, about 3 hp more and lower in revs...

Do you have some numbers for the exhaust port or screen shots from EngMod you can post.

[ief]

Sure, this is what i ended up with for now... i'm sure with some more time there is more there but had enough for today.

[RMS eng]

Indeed. Nevertheless, you should pay attention to the flow through that carb because plenum pressure will drop during the inlet phase and you want to keep that drop as small as possible.
From what I can see, the tract length between the carb and the plenum is quite large, and so is the inertia of the mixture column in it. Though the flow through it is more or less constant, which lessens the inertia's influence, shortening it won't hurt. It will also create more room for an air filter (or should I say vacuum cleaner bag?).

Maybe, but the inflow at the butterfly body looks terrible. I would suggest losing the whole butterfly body and fitting a short, well-rounded bell mouth instead. The better shape and reduced column inertia will promote max.power and overrev. Moreover you may be able to close the inlet earlier which will give you back your low-end torque and simplify setting the carburation. And you will have one less servo system. You know my view on construction in general and on racing equipment in particular: every part that you can leave out, doesn't cost anything, doesn't weigh anything, and never breaks down.

By the way, a 30 mm carb may sound large to you folks, but over here we run 32 mm carbs on 50 cc engines, and they behave quite civilized with them (and make some power as well).

your tracks must be big to run 32mm carbs on your 50s,they would be shit on our small kart tracks,and worse in the wet.

[RMS eng]

That is the quote of the century!!!!!

thats how most of us build race bikes ??

[Frits Overmars]

your tracks must be big to run 32mm carbs on your 50s,they would be shit on our small kart tracks,and worse in the wet.They lap the entire field on kart tracks. With a 5-speed gearbox.

[RMS eng]

They lap the entire field on kart tracks. With a 5-speed gearbox.

what do they lap,do you have a photo of your kart tracks

[dinamik2t]

Just a notice: is there no room for a bigger corner radius for the aux passages? Increasing that would give some extra hp I think!

[jasonu]

thats how the experienced builders build race bikes ??

Fixed it for ya....

[TZ350]

OK today in A grade without Kel all we could do is watch.

Points Race 1 ... :first:2-stroke :second:4-stroke :third: 2-stroke.

Points Race 2 ... :first:2-stroke :second:4-stroke :third: 2-stroke.

The two 2-strokes were Derbi 80's in RS chassis, great little bikes and the 4-stroke was an FXR

With Kel out until November the only saving grace for Team ESE is that the FXR was tuned on the Teams Dyno.

[Buckets4Me]

With Kel out until November the only saving grace for Team ESE is that the FXR was tuned on the Teams Dyno.

that and the 50 kept going all day :clap:

[wax]

D you guys race the 50cc am6 mineralli over in new zealand

[Frits Overmars]

what do they lap,do you have a photo of your kart tracksThis tight enough for you?

[TZ350]

that and the 50 kept going all day :clap:

Your right, there were two Team ESE 50's

[TZ350]

D you guys race the 50cc am6 mineralli over in new zealand



270192270193

Not many around .... this is NedKellys, I think its an AM6

[wax]

I have an mhr mallosi team cylinder for one of these bikes. Brand new in the box I was hoping you guys raced a few as I wish to sell it

[TZ350]

... the inflow at the butterfly body looks terrible. I would suggest losing the whole butterfly body and fitting a short, well-rounded bell mouth instead. The better shape and reduced column inertia will promote max.power and overrev. Moreover you may be able to close the inlet earlier which will give you back your low-end torque and simplify setting the carburation.

I will give it a go, I already have a short bellmouth ready to try.


Closing the valve at 75° ATDC will give reasonable power and a friendly engine. Exceeding 85° aTDC may make the engine bad-tempered. Trying disks with 75°, 80° and 85° will get you in the ballpark. I wouldn't bother trying intermediate values.

The std timing for a GP125 is 55 ATDC (GP100 is 45) and I am currently running 85. EngMod2T suggests that with a 2L plenum (I have 1.5L) that 75deg ATDC would be good for the bottom end without loosing much of the top, so I will take your suggestion and start there.

270195

When I first tried the plenum idea I made a short belmouth.

270196

And the inlet tract was opened up to 32mm

270194

The inlet closing point was 80 deg ATDC and with the short inlet tract at 5-6,000 rpm there was quite a resonance hole that I called the Blarrrs.

270198

I tried closing the inlet earlier but even at 45 ATDC I still had the Blarrs and no top end. The Blarrrs were only cured by extending the inlet tract but now it was too long.

270199

I wanted to be able to continue to close the inlet at 85 deg ATDC and also shorten the inlet tract for better top end. The Butterfly arrangement was much shorter and controlled the blarrrs by changing the resonance of the intake system.

270197

When I first tried the plenum the engine was making 20hp and the plenum did not realy improve things.

I think the plenum will only show a real advantage when the engine has been developed to the point where the F4 Class Restriction of a 24mm carburettor is truly strangling the engines breathing.

To see if we had reached that point now we are at 30hp I wanted to try a bigger 30mm carb as that size was an easy match to the existing inlet tract.

[TZ350]

I have an mhr mallosi team cylinder for one of these bikes. Brand new in the box I was hoping you guys raced a few as I wish to sell it

We are restricted to using non competition parts, aftermarket road going sports bike parts might be OK but race stuff is a definit no no.

I don't know much about the different after market kits, is your cylinder kit "Race" or "Road Sport"?

[wax]

Its the hottest 50cc race cylinder Mallossi make.
Its can get to 20hp out of a 50cc on the right setup

[kel]

only saving grace for Team ESE is that the FXR was tuned on the Teams Dyno.
Owned and developed by an ESE team member therefore the team ESE 4 stroke :innocent:

[TZ350]

Well, the secrets out now, Team ESE are good at developing 4-Strokes too and collectivly have a 2-Stroke and a 4-Stroke at the very sharp end of "A" grade.

[SS90]

This tight enough for you?

The 12hr "Mofar" race they run at the beginning of each season is a real eye opener, many of the most talented engine builders around teamed up with the lightest riders. Much respect, even to finish the race.

[ief]

No idea if this is of any use to you Rob , but it is fun :)

Had another go at it and playing with the exhaust/ port combo didn't yield much other then moving the peak around mostly. I couldn't get past 27.38 kw no matter what i did.

So I took a look at the ignition and reduced the stinger from 23 to 22mm and, 15 exhausts later i got this.

gp5-5 is what i ended up with yesterday, gp5-12 or 17 is just to what is to be preferred (those are different exhausts), i have no clue to that.

All this is still with the worst scavenging and combustion eff. of 0.83.

edit: Why is it that always after i post something i think hmmmmmmmmm.

Most of the power increase seems due to making the stinger smaller and I take it, that would be one of the lesser realistic options due to detonation danger?

Fos his calculations show 18.6 mm and this is 20.3 so perhaps in the danger free zone still? Enlighten me plz ;)

[FastFred]

The 12hr "Mofar" race they run at the beginning of each season is a real eye opener, many of the most talented engine builders around teamed up with the lightest riders. Much respect, even to finish the race.

270210

A Mofa

http://spitzbube.blogspot.co.nz/2011/09/mofa-race-in-ebersbach-germany.html

[F5 Dave]

This tight enough for you?
Looks fantastic!. erm, but what is that presumably optional section closest? Are they. . .erm. . .Jumps?:eek5:

[Gigglebutton]

Owned and developed by an ESE team member therefore the team ESE 4 stroke :innocent:

It shore is and ridden by a new team member Glen Orwin. Thanks Kel, Rob and Richban for your help. Still a work in progress. We want more bottom end and Glen said it handles like a pig

[jasonu]

We want more bottom end and Glen said it handles like a pig

I knew a girl like that once...:crazy:

[cotswold]

It shore is and ridden by a new team member Glen Orwin. Thanks Kel, Rob and Richban for your help. Still a work in progress. We want more bottom end and Glen said it handles like a pig

It's already too fast

[TZ350]

A quick Google on Mofa Racing

<iframe src="http://www.youtube.com/embed/F60wo70HMiM" allowfullscreen="" width="420" frameborder="0" height="315"></iframe>

Twin Engined and Turbo Charged, you have got to be impressed.

<iframe src="http://www.youtube.com/embed/bSdx_z4nKpI" allowfullscreen="" width="560" frameborder="0" height="315"></iframe>

Just like here, a bit of work and imagination goes into building clever engines.

<iframe src="http://www.youtube.com/embed/l3mdcHu7lA0" allowfullscreen="" width="560" frameborder="0" height="315"></iframe>

And it looks like there is some pretty good kit around for the racing boys to bling their rides with.

270263 270264 270265 Mofar Racing

I think I could have lots of fun building something realy fast for this. It would be interesting to know how Mofa racing rules compare to our own F4/F5 regulations.

[Frits Overmars]

Looks fantastic!. erm, but what is that presumably optional section closest? Are they. . .erm. . .Jumps?:eek5:Yes Dave, they are . . .erm. . .Jumps. But no worries; they are only included in the Supermoto-layout.

[TZ350]

<iframe width="420" height="315" src="http://www.youtube.com/embed/HYxs6qF6-oE" frameborder="0" allowfullscreen></iframe>

Engine Brake (Dyno)

[F5 Dave]

Yeah I can imagine how many bucket clip ons would break & our folding pegs that would get forced past 90* on the landing:lol:

[TZ350]

I would suggest about 60% front, 40% rear, both for fast and not so fast bikes. If I recall correctly, the latest and fastes Aprilia GP-bike, the RSA250, had 62% front.

Posted because someone recently asked me about a suitable weight distribution.

Most of the talk on this topic is spread over pages 491 to 498.

[RAW]

Frits you posted the details for the 102 pipe and there was a mention of a 106 pipe, would you share that with us and if it's not to much trouble would you share your knowledge with what performance differences were noted between these two models

With regards to the spark plug posted elsewhere, I have seen the ground separate from the body with that plug

[Frits Overmars]

Frits you posted the details for the 102 pipe and there was a mention of a 106 pipe, would you share that with us and if it's not to much trouble would you share your knowledge with what performance differences were noted between these two models/The only difference is the end cone restrictor diameter: it's 23.3 mm for the 102 and 23.0 mm for the 106 (or the other way around; I can never remember which is which). One was for the 125 cc and the other was for the 250. As the 125 is on full song for a much greater part of the track than the 250, the restrictor difference should compensate for the EGT build-up. Personally I would never go below 23.3 mm with that kind of horsepower.


With regards to the spark plug posted elsewhere, I have seen the ground separate from the body with that plugThanks for the warning. Aprilia switched from NGK to Denso because parts of the isolator fell into the cylinder. Now they have switched to Superbikes :facepalm:.

[dinamik2t]

I think the 102 has 23.3 restriction, based on the schematic in your files, Frits. :yes:

[TZ350]

page 610 .....

Wob talks about simulation packages like the great EngMod2T


Its seems to me that most simulations I do, overestimate the power achievable,thus indicating I am not able to meet the theoretical charging/scavenging efficiency numbers the sim is using.
Having an even better scavenging system would create even more unachievable power in the sim results.
The vast majority of my time is spent optimising the pipe and the intake geometry - the ports are easy, as the STA numbers direct you in the right direction all the time.
If you are short on blowdown the program tells you - you fix it, and get more power - simple,and you can be very sure that the mod you have just done would have worked on an engine , on the dyno, as well.


Combustion Efficiency I vary depending upon the projected quality of the elements.
Running high com on Avgas with a toroid, in a square engine its up around 92%
Low com on pump with crap chamber shape and oversquare, its down around 82%.

Then lastly I move it around a bit if I have what seems to be too much power, but the curve shape is on the money.
It seems to be a fudge factor that can be used to move all the power up and down, it doesn't change the shape.

Re the computer sims believability factor, I have done so many trips to the dyno and got exactly what the sim said I would that its simply not an issue any more.
Only when reaching the outer limits, such as trying to model an RSA, that depends so much on a lot of info we still havnt seen yet ( such as the PWM curve for the powerjets etc),then its a case of crap in = crap out.


it seems possible Aprilia did not switch off the power jet for over rev as the honda did (well maybe?)

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

On a seperate thread Frits shows the aprilia 100% throttle ignition curve which has noticeably more advance than the Honda at higher revs.

Lot of factors come into play obviously but Im wondering if this is the nature of the Triple port vs the Honda twin port


The Aprilia had issues with the full throttle shift when in overev,if the engine was tuned correctly for max power and rpm with the powerjet,it would not " slow down " when the ignition cut was initiated by the riders foot on the shift lever. The powerjet was used as such in the overev, but I have not seen an ignition curve or powerjet % table to be able to make judgement on what was happening.

A powerjet used with an ON/OFF solenoid can recover a huge amount of lost rpm due to the carb becoming naturally progressively richer past peak power, but PWM controll is able to tailor the fuel delivery to exactly what is needed for any effect.


The trend has been for a long time to reduce the volume of all the ducts in modern engines.
Aprilias Ex duct had the bottom filled in such that it was higher than BDC and the corners filled to reduce short circuiting from the A ports.
And the cylinder duct vol was CNC machined to be smaller and smaller in total vol,but in the process heavily promoting flow from the Aux ports to increase effective blowdown flow.

One of the transfer duct entrys was smaller than the port area ( the B and biggest port ) and for sure the ratio between the A and B port duct entry areas was tested
to death within the limitation of the case available area between the studs, by several of the 100 R&D festerers.
The idea here is to reduce the inertia of the initial volume available to the cylinder,that has to be accelerated out of the duct by the negative pressure ratio across the port.




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

True


The trend has been for a long time to reduce the volume of all the ducts in modern engines. The idea here is to reduce the inertia of the initial volume available to the cylinder,that has to be accelerated out of the duct by the negative pressure ratio across the port.


Here our opinions seem to differ. The mass of a gas column in a duct equals specific mass * duct length * duct cross area (let's assume for now that the area is constant over the duct's length). You want to get that mass into the cylinder in a given amount of time and that requires a certain flow velocity. This velocity is inversely proportional to the cross area. And the required pressure difference is proportional to the square of the velocity.

So, though a longer duct will slow down the mass transfer, a larger cross area will help.Where the charge goes, is another matter. It would be quite easy to enhance transfer flow by aiming the leading edges of the A-ports more towards the exhaust port, but that would cause massive short-circuiting.


The flow velocity is pressure-dependent, not port-area dependent (otherwise a closed port would give an infinite velocity. This velocity will only rise somewhat higher in a narrow duct because the smaller mass transfer through it will result in a slower pressure drop, therefore in a prolonged time during which the mass is accelerated.
Using the jamming effect, or RAM effect as the Mericans call it, is just an attempt to correct in the end phase of transfer (or intake) what went wrong at the beginning.

P605


I think the flat sound to the exhaust is due to the top exhaust port chamfer blunting the exhaust note as the port is no longer cracking open suddenly, is that a good thing ???.


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

Funny sounds can turn up if the ignition is borderline. Improving the cylinder filling can be enough to prevent the spark from sparking at the right time every time.
A simple test is to close the plug gap to 0.2 to 0.3 mm. If that improves things, you need a stronger ignition.


The longer the gas column and the higher it has to speed up, the slower will be the initial cylinder (or crankcase) filling. That was what I meant by 'correcting at the end what went wrong at the beginning'.

Utilizing ram effects requires long timings, and vice versa. But the shorter you can keep your timings, the more user-friendly the engine will be (exhaust timing partly excluded because you need a certain minimum timing for resonance).


I believe the big radius at the bore centre line has two effects.

Firstly is to improve the bulk blowdown flow at low opening angles of the piston controlled port orifice, due to the gas attaching early to the roof.

Secondly the exiting wave amplitude is lowered and smoothed out by the gradual ( instead of a sharp edge ) port opening.
This would improve the scavenging action bandwidth, but the peak value is probably then raised as well,simply because the port opens earlier when the pressure above the
piston is greater.

Thus you get the best of both, a wider effective scavenging action, combined with a higher peak value, making the pipe work better over a wider range.


The curved convex shape of the Aprilia duct corresponds directly with the area increasing due to the Aux ducts entering the main.
Again the idea is to keep the duct volume down.

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

Its been tested and proven so many times now, by so many other people, that it should be the first mod to make to any T or tripple port engine.
Here is a pic of one I have just done, that happened to have a tapered spigot - enabling the Aux ducts to be run all the way down into the pipe.
Check the big rad on the transfer duct/bore edge.


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


... you will have one less servo system. You know my view on construction in general and on racing equipment in particular: every part that you can leave out, doesn't cost anything, doesn't weigh anything, and never breaks down.


The only difference is the end cone restrictor diameter: it's 23.3 mm for the 102 and 23.0 mm for the 106 (or the other way around; I can never remember which is which). One was for the 125 cc and the other was for the 250. As the 125 is on full song for a much greater part of the track than the 250, the restrictor difference should compensate for the EGT build-up. Personally I would never go below 23.3 mm with that kind of horsepower.


Some have already seen this, but four those not involved in the project or reading twostrokemotocross.com:
A Kiwi doing Ignitech controlled variable intake timing, plus fuel injection on a two-stroke.
Link: http://twostrokemotocross.com/forum/general-two-stroke-talk/cycle-world-two-stroke-article/15/
Plenty of clever folks there on the opposite side of the globe...


I did a huge testing project a few years ago on Honda CR125 for SKUSA box stock racing in karts.
22mm was as small as I could go sitting dead on 40 Hp at the gearbox,going lower made it finicky to tuning and made no more power - 22.5 made less power.
Although the pipe is a tech item I was able to hide a "tailpipe nozzle " easily enough for testing and racing.
But also from experience that is about the limit on power and tailpipe nozzle size in all sorts of applications.

[teriks]

Some have already seen this, but four those not involved in the project or reading twostrokemotocross.com:

A Kiwi doing Ignitech controlled variable intake timing, plus fuel injection on a two-stroke.
Link: http://twostrokemotocross.com/forum/general-two-stroke-talk/cycle-world-two-stroke-article/15/


Why wait, do it yourselves, the technology is already out there. I use a Link Atom computer on my MX twostroke. Rear transfer port injection, by staging the injection, fuel wastage is reduced, more power, wider power spread. Enough oil deposit on the transfer runs down to the crankcase to service the bigend. It's been running for about eight months now. Yes there has been may issues.


The bike I have fuel injected is Kawasaki 350 Bighorn 1973. This only a test hack. A VMX bike.


Ignore the bike. The EFI that it run's on now is off the shelf components, Link EFI, car injectors, bosch fuel pump, Subaru relief valve. You can see the injector nozzles in the in the back of the crankcase ( x2).
http://i1056.photobucket.com/albums/t380/uniflow/1f6c55fd.jpg



This bike has a vairable rotary valve housing operated by the Ignitec ignition. From 55 degrees valve closing at low speed to 78 Degrees at full throttle.
http://i1056.photobucket.com/albums/t380/uniflow/0c93ef14.jpg



Fueling changes. Link EFI has the ability to change the fueling as the head temp changes. With Ethanol the fuel requirement changes above 70 degrees C, more fuel required. This can be changed on a graph that uses TPS and Temp. This information is overlaid the main fuel map. Very handy with an air cooled engine.



The rod is a Hot Rod, to suit a Polarus trail boss. Five mm longer and I had to bore the crank flywheels out one mm. I offset the holes half a mm to get an extra one mm stroke. It is a much better rod than original. Piston is also Wiseco trail boss.
An exhaust power valve would be next on the development list.
I think this engine is as far as I want to go with development, I only did it to see if it could be done, EFI that is. I bought a YZF 250 to start the next development, throw the engine out and fit a 350 twostroke with EFI. This new water cooled engine will have a powervalve and I would like to use the vairable rotary valve again as it shows good results. Probably will run it on ethanol again as well. Trouble is, Meagan my daughter thinks the YZF is her's now and is using for trail riding. The new engine will probably take a little time to build up anyway.



The rotary valve still organizes the air into the crankcase, just has no fuel with it. Oil is still deposited from the injected fuel around the crank case and rotary valve via deposits in the transfer ports. One of the problems with the Link computer is some it's twostroke injection timing software is not operational yet. I can change the start of injection timing to a given point with the "on time" moving away from this point. I'm injecting approx over 180 degrees at full throttle (180 degrees injector on time ), so I have to set the start at approx 20 degrees after TDC ( quite a way before transfers open) so that at full throttle there is no injection still happening after transfer closes. If injection occurs after transfer port shut the fuel mixture on the next cycle is not so accurate ( power loss ). This I have found. Best it to have a fixed shut time ( approx 30 degrees before transfers shut ) and have the injection start vary. This will bring max injector start time to about 30 degrees ATDC at full throttle. This is what is needed, as up to about one third throttle is happening as the transfer is occurring. This I have found gives best bottom end power. Clear as mud?



In a nutshell, the injection timing is important. I can see why it's probably a good idea to use a small and a large injector, staged. The Link software is not able to do this in " twostroke mode" . Also there is an option to nail down the injector finish time and adjust the start time, or a center and adjust either way from that point. Also not available in twostroke mode. These options are available in fourstroke mode. So next step is to call the bike a fourstroke twin, 360 degree firing ( I don't need to use the ignition as this is done with a separate unit), This will use two drivers ( switches ) in the Link unit to run each cylinder ( if it were a twin ). Both drivers can be hooked together to run my pair of injectors each 360 degree cycle. This requires a cam sensor, I'll use a circuit called a flip flop connected to the ignition trigger ( single pulse per rev ). This circuit ( flip flop ) will only allow every second pulse to be seen by the Link computer, as far as the computer is concerned, a cam sensor. This will trick the computer in doing what I need it to do. Now all these options will be available. New Link soft wear will be available in eight months. I can't wait that long, I want it now.
That's a big nutshell.

Plenty of clever folks there on the opposite side of the globe...

[wobbly]

Have to reduce the Aprilia power output to down around 40 Hp to fit a 22.3 nozzle Frits.

[Frits Overmars]

I think the 102 has 23.3 restriction, based on the schematic in your files, Frits. :yes:Thanks, Dinamik. I corrected the typos in my previous post.

[ief]

Wob, are you saying you put that in engmod and got det warning when going higher then 40 hp when using 22.3 mm?

[wobbly]

I did a huge testing project a few years ago on Honda CR125 for SKUSA box stock racing in karts.
22mm was as small as I could go sitting dead on 40 Hp at the gearbox,going lower made it finicky to tuning and made no more power - 22.5 made less power.
Although the pipe is a tech item I was able to hide a "tailpipe nozzle " easily enough for testing and racing.

But also from experience that is about the limit on power and tailpipe nozzle size in all sorts of applications.

[2T Institute]

Sounds interesting, any pics or vid of it in action?

It is at home at the moment(owner wants more.....) started it up once at home and it is truely loud and obnoxious beast, ask Jeram he was there. A normal chainsaw noise with a ear piercing shriek from the chamber on top


Aprilia switched from NGK to Denso because parts of the isolator fell into the cylinder

Joined the Denso revolution a few years ago when I had a few NGK new-out-of-the box failures.

[TZ350]

270406

This week I have been working on a push and go, no battery required ignition for the Grandsons F5 Honda 100. The ignition was cobbled together from a Jaycar CDI kit and Suzuki trigger and coil. It took a couple of nights of playing around putting the kit together and getting a positive leading edge on the trigger wave form.

A 230 to 9 Volt transformer was connected back to front with the 9V side connected to the Std 6V Honda generator coil and the 230V side charges the CDI capacitors. The points cam lobe was ground away around most of the cam leaving only a small part of the original lobe to excite the trigger.

Got a nice blue spark tonight and its even timed right, so tidy the wiring up next week and the ignition should be ready to go.

[dinamik2t]

Wob, I have a question about EngMod results, if you have some time to spare.
I remember your comment about 'silly long headers'. I have the following and a 61X54.5 engine, which in sim is around 47hp (even at 0.83Ceff), but dynoed only to 34.5hp.

270498270499

All the other parameters seem to be realistic, according to your guidance. I wonder whether this pipe could create a simulation over-prediction.
The thing is, I know neither the AFR nor the ADV curve, but the person to tune it on the dyno is supposed to have experience with these engines. :blank:


Furthermore, could you point out a few things, that a novice tuner should pay extra attention when assembling an engine, so that it's done correctly -like tolerances or similar things (??) ?

[2T Institute]

The screen grab looks very good. That's very over square dimensions, 144mx'ers don't add much peak hp but add a fair bit of area under the curve.

[dinamik2t]

It is indeed too oversquare, but unfortunately that was a given with this engine, nothing I could do. So was the pipe design. We added auxiliary EX ports to help TA and according to EngMod, it was enough for about 52hp.
I simulated the worst engine possible and still got 47, so I am definately missing something, either in inputs or assembly.

[wobbly]

The pipe does indeed have a silly header, but the angle is close to what the second stage of a 2 stage header would have.
It then extends into what would normally be a shallow first diffuser cone.
The result is that the main diffuser is pretty steep, so its this that is giving the good depression around BDC - and the reasonable power delivery at that rpm.
The Aux ports are giving good blowdown , as there is only a small pressure rise when the transfers open.
So many small details affect the real power delivery, and I would have to write a book with 30 chapters to even begin to point you in the right direction
as far as correct assembly is concerned - and its this, that my customers are paying for.

[kel]

I would have to write a book with 30 chapters - its this, that my customers are paying for.
Bleeding your customers to write a book :lol: Write faster, I'll take a copy.

[dinamik2t]

as far as correct assembly is concerned its this, that my customers are paying for.

Har har :sweatdrop. Ok, Wob, thanks!
Perhaps I should seek such directions in race engine manuals.

[TZ350]

270609

OK ... going to have a go on the dyno with the 30mm (the middle) carb tonight. The objective is to see if the 24 is choking the engine yet.

270608

The 24 and smaller 72% and radiused main exhaust port with side windows is making just about the same power as the single 75% wide one did.

270607

But we still have a way to go to get back to the extra wide exhaust ports glory days of 31hp.

Anyway tonight it will be interesting to see what we can get out of a 30mm carb.

[crazy man]

l was thinking about putting a 24mm carb on my brothers rs125 just to see what it ould put out

[speedpro]

Don't tell him though, eh.

[Buckets4Me]

l was thinking about putting a 24mm carb on my brothers rs125 just to see what it ould put out

now thats backwards but would give us an idear :niceone:

[TZ350]

Not the result I was expecting.

270613

Kel gave me a hand with the dyno tonight and here are the carb comparison results .... 30mm carb Blue line vis 24mm Red line and I expect that with a bit of a play the 24 would pickup that bit of over rev too.

Funny thing, after radiusing the top of the exhaust port I had to increase the 24mm carbs main jet from 135 to 145 and the 30 ran best at 125 ...... bigger carb smaller main jet, I don't get that.

At near 30rwhp it looks like the 24mm carb is not strangling the intake yet, so something else is holding it back. And the good old plenum is not needed for now and can go back in the cupboard.

[dinamik2t]

I like this test TeeZee; trying to find out what's missing in a back to back test.
I wish I could answer you carburation question.. I recently found this Dellorto 'read-me' pdf: http://www.thisoldtractor.com/gtbender/mg_manuals/dellorto_manual.pdf. I haven't read it yet, but perhaps there are some interesting info inside -looks so at least.

[TZ350]

Just had a look at it, very interesting read. Thanks.

[dinamik2t]

There were also these two ignition tester made-in-china gadgets, which seemed rather interesting:

http://www.rccdi.com/news/Accessories/8.html
http://www.rccdi.com/news/Accessories/7.html

Forgot to mention them the other day..
The instructions doesn't help much. The first is a spark tester / RPM, the second one a static/base advance finder.
They're sold on ebay too.

[ief]

Would you mind sending me the recent engmod files Rob? Didn't get much feedback on the ones I send you and perhaps of no use at all but still curious. I'm now at 42 hp, detuned exhaust to 22 mm stinger and 24mm carb. Only thing perhaps to high is compression of 7.1? (not to sure about ignition figures as well in the light of realism)

But still, if I hear dinamik simming 47 and making 34 then what's the use ai?

Nevertheless would be nice to be able to compare yours and mine for educational purpose and all :)

[dinamik2t]

Oh, Rob's simulation consistensy is far better than mine. From 39 to his max 31, is only factor .8 .
And Wob has already proven it even better. Myself, I am just missing the experience to supervise the sims predicting capabilities, unlike a 30year-experienced tuner. If it wasn't like that, I guess they would like to pull all their (remaining?:shifty:) hair out!

I can upload that 47dk pack, if you like to play though.


(dk=the donkey unit)

[ief]

Don't mind if you do Din, the more the merrier ;)

[dinamik2t]

Here you go:
http://users.uoa.gr/~sph0800108/modenas_dinamik_forum/EngMod2T/2stroke.rar
( http://users.uoa.gr/~sph0800108/modenas_dinamik_forum/EngMod2T/54.OneHalf.pack , http://users.uoa.gr/~sph0800108/modenas_dinamik_forum/EngMod2T/Apr_RSA125.pack , http://users.uoa.gr/~sph0800108/modenas_dinamik_forum/EngMod2T/Z-61-Georgio.pack )
Mind yourself though, there may be inaccuracies esp. on carb & exp/trp files. Anything with a greek question mark ';' is definitely one of them.

[ief]

Cheers! Will take a look at it later on :niceone:

[TZ350]

But still, if I hear dinamik simming 47 and making 34 then what's the use ai?

I think your right, changing things like port timing is wrong but varying the combustion and I guess delay and other related variables is the way to get the simulation to reflect your engines reality at the crank.

Although EngMod2T is just a simulation and not real life on a dyno, it does suggests the outcome of any changes and direction to take, and EngMod does this very well. But sometimes I have found myself tickling the simulation to get a bigger hp number, with changes that can't be made in real life.

Below is Wobs view.


Combustion Efficancy, I vary depending upon the projected quality of the elements.

Running high com on Avgas with a toroid, in a square engine its up around 92%
Low com on pump with crap chamber shape and oversquare, its down around 82%.
Then lastly I move it around a bit if I have what seems to be too much power, but the curve shape is on the money.
It seems to be a fudge factor that can be used to move all the power up and down, it doesn't change the shape.

Re the computer sims believability factor, I have done so many trips to the dyno and got exactly what the sim said I would that its simply not an issue any more.
Only when reaching the outer limits, such as trying to model an RSA, that depends so much on alot of info we still havnt seen yet ( such as the PWM curve for the powerjets etc),then its a case of crap in = crap out.

[TZ350]

270649

Chambers offers a virtual Chocolate Fish to the first person who correctly identifies what this cylinder came from and nope, not a lawn mower.

270648

Low wide inlet port, transfers and exhaust are just drillings.

270647

The carbon build up clearly shows the combustion gases have been back flowing down the transfer ports. More so on the exhaust port side and its instructive how far the carbon extends down the port wall, apparently this happens on part throttle at high rpm.


It seems that at high rpm and part throttle the pressure in the cylinder is higher than in the crankcase when the transfers open and hot burnt combustion gases back flow down the transfers. Part throttle detonation is the current big issue for our 30+hp air-cooled engine. Retarding the ignition on part throttle is only part of the solution.

The above Quote links to a detailed discussion by Jan Thiel about this back flow phenomenon and its effects on high performance 2-stroke reliability.

[crazy man]

a chain saw

[F5 Dave]

Well I'm glad you did the larger carb experiment. That is not what I would have expected either, but it underlines my mantra of 'test everything'. I have been surprised many times fitting stuff that is going to be better & isn't. For instance I had a 24mm carb for my 50 as well as a 26 & a 28. All Mik flatslides. I made a new inlet & it was 26mm at the manifold.

Of all the carbs the 28 was the best. The 24 which I was hoping would be my kart track setup wasn't as good but almost matched the 28 in overrev. the 26 was worse all over no matter what jets were fired at it. Clearly the slope may be dependant on the air bleed, but you should be able to get some of the curve to match, like peak.

[Drew]

a chain sawI thought that too, but how do you run a chain saw at part throttle/high rev?

So my guess is, radio controlled plane.

[TZ350]

a chain saw

We have a winner

270655



I thought that too, but how do you run a chain saw at part throttle/high rev?

Yes, good point ... not sure.

[TZ350]

Well I'm glad you did the larger carb experiment. That is not what I would have expected either ... For instance I had a 24mm carb for my 50 as well as a 26 & a 28.

Interesting about the different carbs you have tried on the 50 and that the 28 was the best, where I would have gone for the 24.

[Drew]

Yes, good point ... not sure.

It's bugging me for some reason.

Only thing my less than optimum mind can come up with, is that if the governor on a chainsaw works the same as a lawn mower by oscilating the throttle butterfly quickly when the revs get up. I suppose that is part throttle.

[dinamik2t]

Below is Wobs view.

An addition on those, but only from 'sim life' testing:
Ceff will impact the overrev. Lower the factor and it has less power/rpm in overrev. Also, higher Ceff setups, are more sensitive to ADV and have higher cylinder temperatures.

[crazy man]

We have a winner

270655




Yes, good point ... not sure.yum chocy fishie:banana:

[TZ350]

It's bugging me for some reason.

Only thing my less than optimum mind can come up with, is that if the governor on a chainsaw works the same as a lawn mower by oscilating the throttle butterfly quickly when the revs get up. I suppose that is part throttle.

All the Still chain saws I have had something to do with didn't have a governor, just a trigger throttle. Although you didn't hold it on part throttle much, it was more like all or nothing but I guess all the momentary times on part throttle all add up.

For a chain saw I suspect you also get this blow back when its maxed out and won't rev any higher because there is insufficient blowdown time area to support any more rev's.

[HPbyGD]

How about just taking all the vent lines from the carb and either apply a small pressure or a small vacuum to them to get an indication of which way your jetting needs to go ? It is a lot faster then stopping the testi to change jets !

Gary



Having managed 29hp with the taper bored 24mm OKO I wanted to see what difference a bigger carb might make. The taper bored OKO is 31mm at the engine flange so I bored another OKO out to 30mm at the slide and 31 at the flange.

Set the 30mm carb up with a main jet one size bigger than the 24 and ran it up. It started and warmed up ok but when I tried to move up through the gears it wouldn’t accelerate.

Anything over half throttle and it just sat there going Blarrrr, sounded rich but I was caught out thinking that the other night. If it was lean I would have expected it to just cut out, it kept going but no matter what I did with the throttle it just would not pickup, sounded flat and rich.

The taper bored 24 had a 145 main, the 30 a 150 so it’s hard to imagine the 30 needing a main smaller than the 24. ???? ran out of time to look into it. I didn't think of it at the time but I should have pulled the power jet feed line off. Killing the power jet would have quickly told me if it was rich or lean.

Kel and I now think the flat sound to the exhaust is due to the top exhaust port chamfer blunting the exhaust note as the port is no longer cracking open suddenly, is that a good thing ???.

[ief]

Oeps, seems I 'lied' a little, I was under the impression comb eff. was @ 0.83 but it was set @ 0.87, that cost me about 3 hp (so 38.5 now) but I presume I can make up for it by working on the exhaust once again (all ready have made about 70 versions/ adaptations :))

Other then that I could see it as being pretty ok-ish, comb file is mostly wobs work with exception of the ignition curve as is the temp file.

I found most of the positive changes became; as wide as much tr, little longer tr duct, slightly shallower angles, lowered exhaust and aux (from what i had) shape of the inlet was good for one kw (!) and reducing the carb length and longer intake (83.5 degr if memory serves) on the RV.

And of coarse fine tuning the exhaust...

Anyway, I got some more playing to do wit 0.83 comb. eff. See if I can get it back to 40+ :)

[FastFred]

270647

The carbon build up clearly shows the combustion gases have been back flowing down the transfer ports. More so on the exhaust port side and its instructive how far the carbon extends down the port wall, apparently this happens on part throttle at high rpm.

I think it also happens on full throttle at high rpm when the blow down becomes to short for the rpm and the pressure of the remaining combustion products in the cylinder push into the transfers and prevent the inflow of fresh mixture. Adjusting the blow down time area is a little trick that can be used to govern the top rpm (speed) of the chain saw, lawn mower, moped or scooter etc.


... the governor on a chainsaw works the same as a lawn mower ...

Drew may be right, chainsaws and lawn mowers et all have simple built in governors.

[Yow Ling]

I think it also happens on full throttle at high rpm when the blow down becomes to short for the rpm and the pressure of the remaining combustion products in the cylinder prevent the inflow of fresh mixture. Adjusting the blow down time area is a little trick that can be used to govern the top rpm (speed) of the chain saw or Moped Scooter etc for a simple self governor.



Drew may be right, chainsaws and lawn mowers et all have simple built in governors.

The pipe probably helps govern the revs too, I think microlights use the pipe to cap the rpm as well

[Drew]

The pipe probably helps govern the revs too, I think microlights use the pipe to cap the rpm as well
You can do that without killing or maiming the power output?

[FastFred]

The pipe probably helps govern the revs too, I think microlights use the pipe to cap the rpm as well

True, but would it account for the carbon in the transfer ports on the chainsaw cylinder . :scratch:

I think that blow down is used to limit the max full throttle no load rpm seen by a chainsaw, lawn mower, concrete cutter, weed eater etc.

Where as the Microlight engine is under load all the time its spinning the prop and at WOT finds its happy place on the torque curve as defined by the pipe and that could be a place where blow down is totally adequate and there is no blow back down the transfers.

2-strokes, so simple, and yet so complicated.

[TZ350]

l was thinking about putting a 24mm carb on my brothers rs125 just to see what it could put out

I would be very interested in seeing the result... :)

[TZ350]

270747

I have just received another Knock Gauge, this one has two extra outputs. http://www.knockgauge.eu/content/blogcategory/22/41/

YouTube links showing the Knock Gauge in action.

The two green lights, the orange warning light then you see the red det light. http://youtu.be/aZkZR-JBr_E and http://youtu.be/vFoZyw_sHmA

Like last time, one that goes to ground for signaling the IgniTec to retard and a new one that pulses from 0V to +5V each time the Knock Gauge sees a detonation event.

The Curtis event counter can then count the detonations. Now I have the makings of a det sensor, ignition retarder and det counter.



269009


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

269008


This post links back to various cheap counters that could be used with the Knock Gauge.

[richban]

270747

I have just received another Knock Gauge, this one has two extra outputs. http://www.knockgauge.eu/content/blogcategory/22/41/

Like last time, one that goes to ground for signaling the IgniTec to retard and a new one that pulses from 0V to +5V each time the Knock Gauge sees a detonation event.

The Curtis event counter can then count the detonations. Now I have the makings of a det sensor, ignition retarder and det counter.



This post links back to various cheap counters that could be used with the Knock Gauge.



If I can get a laptop to talk to my ignitech proper I will have a go at setting the ignition with the amped up earphones on the dyno. The computer I was playing with just kept wanting to install stuff. Hate windows. I have a Mac. or 2. Will let you know how I go Rob. Hp might remain a rumor for a while.

[TZ350]

If I can get a laptop to talk to my ignitech proper I will have a go at setting the ignition with the amped up earphones on the dyno.

I will be interested to see how you get on, with mine, all I could hear was noise, maybe I had something wrong.

I also had a lot of trouble with my computer freezing up when it was talking with the IgniTec on the Dyno, a 5K resistor plug cap cured that.

[richban]

I will be interested to see how you get on, with mine, all I could hear was noise, maybe I had something wrong.

I also had a lot of trouble with my computer freezing up when it was talking with the IgniTec on the Dyno, a 5K resistor plug cap cured that.

I did quite clearly hear the knock with Andrews phones last time. It was a manifold leak.

[TZ350]

270755

I must have something wrong on mine, the pickup maybe. I will have another look at it.

270754

This is a USB to Serial converter I used with the IgniTec, it seems to work OK.

[richban]

270755


This is a USB to Serial converter I used with the IgniTec, it seems to work OK.

The computer see's that there is a serial device there but try's to go looking for software to install the device as fas as I can figure. So the USB connection is working I spoz. Last time I just plugged it in and it worked. But that was with a serial cable. Different computer. So maybe I do need to install something.

[richban]

I must have something wrong on mine, the pickup maybe. I will have another look at it.




Maybe just have the bike running hi idle have a listen then undo the manifold clip and start to pull the carb off. Should hear it knock as it leans with all the extra Air. I think.

[TZ350]

The computer see's that there is a serial device there but try's to go looking for software to install the device as fas as I can figure.

Software that I had to install came with my USB/Serial cable.

[Yow Ling]

Making progress on my dyno, would have done more but after getting the big wheels out of the car boot Im rooted !

l270756270757

[TZ350]

That looks like the makings of a pretty decent inertia dyno. Is the disk break for slowing it down after a pull or going to be for holding a load on the motor?

[Yow Ling]

That looks like the makings of a pretty decent inertia dyno. Is the disk break for slowing it down after a pull or going to be for holding a load on the motor?

could be both, havnt got a caliper yet, the disk is off a v8 commodore. I havnt got much experience with dynos yet other than a few quick runs and one session at the Ashvegas dyno. hope to have the drum finished and mounted this weekend

[Sketchy_Racer]

Speaking of dyno's, Kyle and I have almost finished our inertia dyno too, did all the machining last weekend and got the frame together this arvo.

What software you looking at running Yow?

270758270759

[TZ350]

Those dynos are looking good, things are getting real interesting in F4 & 5 now with all this development work going on.

[dmcca]

I'm glad the discussion has come to dynos... I'm serious about buying one very soon.
For those in the know what do you think of low weight roller eddy current dynos?? I'm looking at a Dynotech (made by dyno dynamics and shares the drivetrain of the 450DS) and it has a hollow, light weight roller and ALL load and acceleration is controlled by the eddy current retarder. It cannot be run in 'inertia' mode but the benefit of the light roller seems to be that it shows up every little glitch in ignition and fueling that a heavy roller would mask.

Thoughts?

[Sketchy_Racer]

I'm glad the discussion has come to dynos... I'm serious about buying one very soon.
For those in the know what do you think of low inertia eddy current dynos?? I'm looking at a Dynotech (made by dyno dynamics and shares the drivetrain of the 450DS) and it has a hollow, light weight roller and ALL load and acceleration is controlled by the eddy current retarder. It cannot be run in 'inertia' mode but the benefit of the light roller seems to be that it shows up every little glitch in ignition and fueling that a heavy roller would mask.

Thoughts?

I dont have a lot of experience with dynos, but my theories are along the lines of this;

Although I like the idea of running an engine at a steady state to test certian RPM, the reality is that in normal operating conditions a motor cycle race engine is never held at fixed RPM. So while it may be great for problem solving, I feel that for optimal tuning it is not so great. What lets the inertia dyno down is that it is only really effective at full throttle, but the data is far more relevant and repeatable which is the most important aspect.

For the dyno Kyle and I are making It is a inertia dyno, but I am going to add a eddy current brake for doing steady state testing but with no data acquisition. I have just started the design for it now, but it will be a home built eddy current brake so we'll see how it goes.

I suppose it comes down to what you want to use it for.

[quallman1234]

270755

I must have something wrong on mine, the pickup maybe. I will have another look at it.

270754

This is a USB to Serial converter I used with the IgniTec, it seems to work OK.

Gotta watch those USB to serial converters, as the majority use TTL. Which is 5V, where as some equipment requires 15V.
I had to buy a PCMCIA Seiral card for a laptop at work, to get it to work with our electronic locks and also our cnc cropper. Obviously thats big shit but it is something to be aware off.

[Frits Overmars]

I'm looking at a Dynotech and it has a hollow, light weight roller and ALL load and acceleration is controlled by the eddy current retarder. It cannot be run in 'inertia' mode but the benefit of the light roller seems to be that it shows up every little glitch in ignition and fueling that a heavy roller would mask.It's the other way around. High-inertia rollers do not mask anything. Controlled brakes of any type do, especially the 'advanced' variety with step test facilities.
In a step test the controller tells the dyno to step through the rpm range in 200 rpm steps, for example, and each next step is to be reached in 0,2 seconds, also for example.
Suppose the engine reaches a very weak spot somewhere in its power curve. But it has to move on regardless, at the rate dictated by the controller. If it appears that it won't reach the next step in time, braking torque is reduced, to zero if necessary, and the engine strolls through the entire rev range at a nice even pace.
Put that same engine on an inertia dyno and you can hear it struggle to get out of that weak spot. The carburation may get upset in the processs, the plug may foul, exactly like it would on a track. With a brake dyno you won't find out until you get to the track. And then it may be too late.

[Neal]

270747

I have just received another Knock Gauge, this one has two extra outputs. http://www.knockgauge.eu/content/blogcategory/22/41/

YouTube links showing the Knock Gauge in action.

The two green lights, the orange warning light then you see the red det light. http://youtu.be/aZkZR-JBr_E and http://youtu.be/vFoZyw_sHmA

Like last time, one that goes to ground for signaling the IgniTec to retard and a new one that pulses from 0V to +5V each time the Knock Gauge sees a detonation event.

The Curtis event counter can then count the detonations. Now I have the makings of a det sensor, ignition retarder and det counter.



This post links back to various cheap counters that could be used with the Knock Gauge.


How much does a complete set up cost ?

[Yow Ling]

Speaking of dyno's, Kyle and I have almost finished our inertia dyno too, did all the machining last weekend and got the frame together this arvo.

What software you looking at running Yow?

270758270759

Thats looking flash, better hurry up with mine. I have been looking at Dyno Mite software from performance trends about US$500 for 3 channels drm speed ignition and egt. you can download a copy of the software not crippled for 10 days, looks ok to me . So far im $600 into this so it looks like $1500 will kill it.
What did you use for the roller, mine is a cng cylinder with the mass bolted to the ends

[TZ350]

How much does a complete set up cost ?

Its a bit of a pick and mix so I highlighted the dollar amounts so you can see where the prices come from.




269009

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

http://www.ebay.com/itm/Knock-gauge-for-detonation-sensor-klopfsensor-NEW-/180904010253?pt=Race_Car_Parts&hash=item2a1eb8220d&vxp=mtr

Knock Gauge $49.99 plus option 1 switch to ground for the IgniTec ignition retard add $20 plus option 3 pulsed 0v to 5V for the counter so add another $20

$90 USD for the Knock Gauge part off Ebay.

Less than $200 NZD should cover it.

[TZ350]

270776

dyno like this?

Small home made inertia dyno. more pictures on the original post.

<iframe src="http://www.youtube.com/embed/HYxs6qF6-oE" allowfullscreen="" width="420" frameborder="0" height="315"></iframe>

Engine brake dyno, simple to make and easy to calibrate.

270777270778270779

And then there are the Iphone Dyno Apps.

http://www.dtec.net.au/Inertia Dyno Design Guide.htm

http://www.dtec.net.au/Inertia & Brake Dyno (Dynamometer) System - Kart, RC, Bike & Car- Engine & Chassis.htm

Lots of info on bits and bobs suitable for making a small dyno.

Measurement is Everything ... we can only improve what we can measure.

[Sketchy_Racer]

Thats looking flash, better hurry up with mine. I have been looking at Dyno Mite software from performance trends about US$500 for 3 channels drm speed ignition and egt. you can download a copy of the software not crippled for 10 days, looks ok to me . So far im $600 into this so it looks like $1500 will kill it.
What did you use for the roller, mine is a cng cylinder with the mass bolted to the ends

Ours is a solid roller, made from scrap metal. it's 20X 20mm thick 300 diameter steel disks with a 40mm hole bored in them with a shaft through the lot. They have been welded together then machined round. It is certainly not a "pretty" way of doing it but it was free which is what this project is all about I am about $500 into it now and that is including buying a brand new cooling blower ($270) I'm having fun at the moment getting it ballanced up, looks like it is going to be hard. I has a small vibration at around 50KPH drum speed then goes away. It may be as good as it gets with the roller we have. It is not bad though just enough to feel when standing on top of it while doing a run, you can't feel it through the bike.

Kyle is in the process of making some software at the moment to try, to begin with we are only going to be monitoring drum RPM but may build in a ignition RPM sensor later. With my EFI bike the ecu already sends out a graph with RPM over time so I can use that data to calculate the torque curve from the calculated moment of inertia of the drum.

Also i'll get some photos tonight of the way I made the wheel length adjuster, it's simple as and works very easy.

[Yow Ling]

Started assembling it today, looks like its built for Russian Navy , lots of big steel

270788

[Sketchy_Racer]

That is one tough looking dyno! Better put some wheels on it so you can move it! What are the measurements of your drum and flywheels

I spent this arvo balancing mine, pretty happy with it, in theory it needs to be dynamically balanced but I recon I can get it good with the suck and see method, it's probably around 30g out now but not sure where and which side.

[Yow Ling]

I have a shipping container behind the shed was going to put it in there, the big wheels are 400mm OD 80mm thick the cng cylinder is 320 mm OD 10mm wall and the end plugs for the cylinder are 300mm OD 25mm thick 400mm shaft same as yours. The frame is 750 between the rails. All the steel was given to me so not much point in scrimping on that part, ran out of CO2 for my mig so kinda done for the weekend frame wise, maybe tomorrow I go drill some holes in the weights.

Balance wise mine will be a bit of a mess, the disks were the centres for some big gears when they flame cut them they put the start in my bit, I will need to measure the volume of the cut and remove a similar amount from the opposite side, also the cng cylinder isnt as round as it could be

[Ocean1]

That is one tough looking dyno! Better put some wheels on it so you can move it! What are the measurements of your drum and flywheels

I spent this arvo balancing mine, pretty happy with it, in theory it needs to be dynamically balanced but I recon I can get it good with the suck and see method, it's probably around 30g out now but not sure where and which side.

Have you got a shaft in it yet? Only, I'm wondering if you can get it onto a wheel balancing machine...

[Kickaha]

Have you got a shaft in it yet? Only, I'm wondering if you can get it onto a wheel balancing machine...

Unless it's a truck balancer I think it would be to heavy and it's probably to long anyway, you'd also have to make some kind of adapter to be able to bolt it up

You could do a static balance easily enough if you had a couple of v blocks and bearings to suit or even with it in the frame

[Ocean1]

Unless it's a truck balancer I think it would be to heavy and it's probably to long anyway, you'd also have to make some kind of adapter to be able to bolt it up

You could do a static balance easily enough if you had a couple of v blocks and bearings to suit or even with it in the frame

Knife-edges would be the traditional way, and yeah you can get it good, but only in a single plane. Wouldn't actually cost that much to get Howitts in Naenae to do it.

[wobbly]

This is what is on my engine dyno.

http://www.sportdevices.com/dyno/sp1.htm

I have used this setup for over 12 years, with a couple of upgrades by selling the complete dyno ,and rebuilding better - as I am doing right now.
A great system, and the software can be downloaded and used at any time.
Using 152 teeth input on the starter wheel, it can resolve 1/10 Hp changes in a KT100 with amazing repeatability, as long as you use an egt, head and case temp setup to replicate
engine heat load on every test.

Frits is right ( as usuall ) about the acceleration dyno being the most useful.
I set up the engine gear ratio to test, so it accelerates as it would as close to track conditions as possible.

But an eddy current can be set up to work exactly like an inertia, simply by using the constant load mode.
Then the absorber applies the same load to the engine all the time, just like a steel wheel or roller.
Advantage is that on say a Dynojet you can easily dial up the load needed in % terms, to get the acceleration rate you want.
We use that facility with a twist - program it to increase the load with roller speed.
Thus when doing an all gear run, the load increases just like the wind drag with increasing speed - so the acceleration rate decreases.
Perfectly mimicking the track conditions.
Means you can dial in the ignition and fuelling at very high acceleration rates in the lower gears, then do the same at slower rates in 5th/6th.

[bucketracer]

<iframe width="560" height="315" src="http://www.youtube.com/embed/fPnkDd0cepg" frameborder="0" allowfullscreen></iframe>

Keeping up the corner speed.

[richban]

<iframe width="560" height="315" src="http://www.youtube.com/embed/fPnkDd0cepg" frameborder="0" allowfullscreen></iframe>

Keeping up the corner speed.

Gay...........

[Ocean1]

Thus when doing an all gear run, the load increases just like the wind drag with increasing speed - so the acceleration rate decreases.
Perfectly mimicking the track conditions.

I've heard of older dynos that use a monty great fan as the load, for similar reasons.

Think the rate of change would be too high to simulate drag in race conditions. You could, however add a smaller fan, driven off an existing roller to get pretty close, and throttle the fan intake to fine-tune it.

Is there a market for these things, guys? Or are they worth just whatever spare time you have to make one?

[Sketchy_Racer]

I've heard of older dynos that use a monty great fan as the load, for similar reasons.

Think the rate of change would be too high to simulate drag in race conditions. You could, however add a smaller fan, driven off an existing roller to get pretty close, and throttle the fan intake to fine-tune it.

Is there a market for these things, guys? Or are they worth just whatever spare time you have to make one?

Yeah there is a market, but there is a reason a commercially available dyno is upwards of 10-15k. To build one "properly" would be a great cost, where ours are made of scrap metal and although be useful wont be as versatile as a professional unit. I would imagine that if we put our DIY units up for sale we may get a couple of thousand for it, but it is only worth what someone is prepared to pay for it.

I am looking into building a trailer to house mine, but that may be a while away I have run out of room!

[Yow Ling]

Is there a market for these things, guys? Or are they worth just whatever spare time you have to make one?

There is a desire to own one, but usually as far as it goes. You can buy a FXR for the price of making one, and most bucketracers are a little more cost conscious than your average 600 or 1000cc racer. Sketchys one looks great because it looks like it can be stored under a bed or in a wardrobe.

Maybe having a dyno is like roasting your own coffee beans, can be done but there is a bit of dicking around involved, you have to be keen

[jasonu]

Totally Gay...........
Fixed it for ya

[dmcca]

It's the other way around. High-inertia rollers do not mask anything. Controlled brakes of any type do, especially the 'advanced' variety with step test facilities...



Frits is right ( as usuall ) about the acceleration dyno being the most useful.
I set up the engine gear ratio to test, so it accelerates as it would as close to track conditions as possible.

But an eddy current can be set up to work exactly like an inertia, simply by using the constant load mode.
Then the absorber applies the same load to the engine all the time, just like a steel wheel or roller.
Advantage is that on say a Dynojet you can easily dial up the load needed in % terms, to get the acceleration rate you want.
We use that facility with a twist - program it to increase the load with roller speed.
Thus when doing an all gear run, the load increases just like the wind drag with increasing speed - so the acceleration rate decreases.
Perfectly mimicking the track conditions.
Means you can dial in the ignition and fuelling at very high acceleration rates in the lower gears, then do the same at slower rates in 5th/6th.

Thanks Frits and Wobbly, very helpful answers.

Frits, your response was not what i expected but makes total sense the way you explain it.

It seems to me that an eddy current dyno is capable of a wider variety of tests for efi and ignition tuning (step tests, drag tests, constant rpm test, etc) albeit with less accuracy and repeatability than an inertia dyno, which is best used to mimic acceleration as seen on a track. Is there a perfect middle ground... Something like the Dynojet with its heavy roller AND an eddy current brake? Or do the two units simply perform different tasks and therefore are best used for what they are designed for.


as long as you use an egt, head and case temp setup to replicate
engine heat load on every test.

Wobbly can you explain this further? So do you just monitor these manually and do a final comparison run once the heat build up in the engine matches previous runs?

[Yow Ling]

Thanks Frits and Wobbly, very helpful answers.

Frits, your response was not what i expected but makes total sense the way you explain it.

It seems to me that an eddy current dyno is capable of a wider variety of tests for efi and ignition tuning (step tests, drag tests, constant rpm test, etc) albeit with less accuracy and repeatability than an inertia dyno, which is best used to mimic acceleration as seen on a track. Is there a perfect middle ground... Something like the Dynojet with its heavy roller AND an eddy current brake? Or do the two units simply perform different tasks and therefore are best used for what they are designed for.



Wobbly can you explain this further? So do you just monitor these manually and do a final comparison run once the heat build up in the engine matches previous runs?

The Dynojet at Ashburton has exactly that an inertia drum and an Eddy current brake on the same shaft, I guess the software must combine the data from both parts to give a final reading. When I ran my bucket down there the Eddy brake has a temp sensor and was running over 200°C so how much of my 19hp went into there I dont know, must have been a reasonable portion

[Ocean1]

Yeah there is a market, but there is a reason a commercially available dyno is upwards of 10-15k. To build one "properly" would be a great cost, where ours are made of scrap metal and although be useful wont be as versatile as a professional unit. I would imagine that if we put our DIY units up for sale we may get a couple of thousand for it, but it is only worth what someone is prepared to pay for it.

I am looking into building a trailer to house mine, but that may be a while away I have run out of room!

For a build of 5-10 units I reckon I could make the mechanical components for maybe $4-5k, budget for metrology starts from perhaps a few hundred, reasonable range for about a grand, (sky's the limit, obviously). Guess it still boils down to more than most bucket racers would want to pay but I can see a club or even a couple of teams collaberating. In which case building one around a road trailer makes a lot of sense.

[Buckets4Me]

For a build of 5-10 units I reckon I could make the mechanical components for maybe $4-5k, budget for metrology starts from perhaps a few hundred, reasonable range for about a grand, (sky's the limit, obviously). Guess it still boils down to more than most bucket racers would want to pay but I can see a club or even a couple of teams collaberating. In which case building one around a road trailer makes a lot of sense.

the hard part is getting a decent roller $$ and then the software $$ all the other parts are doable by just about anyone

[dmcca]

the hard part is getting a decent roller $$ and then the software $$ all the other parts are doable by just about anyone

I priced up making my own inertia dyno not long ago... Solid roller ~350kg, ~400mm dia, 400mm long with stub axles, machined out of a solid bar was going to be $2000 for the material and about $1000 in machining. Plus transport between steel supplier, machinist and then me. Including the software/hardware that wobbly mentioned above plus a starter system, battery, steel frame, chequer plate covers, computer, monitor, fans, printer, etc, etc was going to be about $7000 from memory plus my time. Of course they can be made cheaper as others here have skillfully done, but then they're not suitable for resale as has been suggested in the last page or so.

After pricing everything up I found this one new for $8000 plus about $1000 freight, which seemed WAY easier than making one... http://www.daytondyno.com/webpage200hp.html

... Then I got side-tracked by an eddy current dyno... and that's where I still am today!

[crazy man]

I priced up making my own inertia dyno not long ago... Solid roller ~350kg, ~400mm dia, 400mm long with stub axles, machined out of a solid bar was going to be $2000 for the material and about $1000 in machining. Plus transport between steel supplier, machinist and then me. Including the software/hardware that wobbly mentioned above plus a starter system, battery, steel frame, chequer plate covers, computer, monitor, fans, printer, etc, etc was going to be about $7000 from memory plus my time. Of course they can be made cheaper as others here have skillfully done, but then they're not suitable for resale as has been suggested in the last page or so.

After pricing everything up I found this one new for $8000 plus about $1000 freight, which seemed WAY easier than making one... http://www.daytondyno.com/webpage200hp.html

... Then I got side-tracked by an eddy current dyno... and that's where I still am today!it was 1700 for my 350 dia roller machined my self witch ended up taking 3 x longer than l thought . a 1000 would be cheap as if you got it done for that. it took 8 hours just to norl the dam thing! but if you could find one cheap its the way to go but if you can do most the work your self and to say you made it at the end of the day good on you

[Ocean1]

the hard part is getting a decent roller $$ and then the software $$ all the other parts are doable by just about anyone


I priced up making my own inertia dyno not long ago... Solid roller ~350kg, ~400mm dia, 400mm long with stub axles, machined out of a solid bar was going to be $2000 for the material and about $1000 in machining. Plus transport between steel supplier, machinist and then me. Including the software/hardware that wobbly mentioned above plus a starter system, battery, steel frame, chequer plate covers, computer, monitor, fans, printer, etc, etc was going to be about $7000 from memory plus my time. Of course they can be made cheaper as others here have skillfully done, but then they're not suitable for resale as has been suggested in the last page or so.

After pricing everything up I found this one new for $8000 plus about $1000 freight, which seemed WAY easier than making one... http://www.daytondyno.com/webpage200hp.html

... Then I got side-tracked by an eddy current dyno... and that's where I still am today!

Can't help with the transport, software (actually, maybe I can), battery, printer etc etc but a solid steel roller is a fairly expensive place to start if you just want mass. I also started making one, years ago, was a 3ft length of 12" line-pipe filled with concrete and a Caterpiller halfshaft. Ballanced up fine and cost me... can't remember but not very much.

[wobbly]

Running a KT100 is fraught with heat problems, as it affects every part of the testing.
Simply put, you MUST have the same head temp and case temp at the start of every test.
Then monitor the egt at the end of each test.
For example you can change the pipe length, run up the engine to get your reference head and case temp.
But the egt at peak rpm may be 100* lower.
So you must then turn the tap and change the jetting.
This then means repeat the test, until you reach the same egt as previously.
Then overlay the curves to see if the new pipe length actually is better than the last one.
All you are doing is replicating what would happen on the track,but making very sure the conditions are perfectly equal.
This enables the 1/10 Hp resolution in changes to be seen with confidence, as head or case or egt temp has a way bigger influence on the dyno power reading, than any pipe or small port timing change would ever produce.

Same issue with a water cooled 125.
If the change produces a change in egt, then you must go back and rejet and rerun the test.
On track we will always be shooting for a reference egt,by changing jets based on the current air conditions,no matter what the port timing or the ignition curve or the pipe shape,may be.
So the dyno result must reflect this process to be able to document on track reality and thus performance, with any useful accuracy.

[dinamik2t]

Wob, with air-cooled engines do you simulate somehow the stream of air cooling the cylinder/head ?
This (air-cooling in general) must be a good reason for power losses between sim-dyno. Do you have any idea of the efficiency of the air-cooling system described in EngMod?

[Brian d marge]

Wob, with air-cooled engines do you simulate somehow the stream of air cooling the cylinder/head ?
This (air-cooling in general) must be a good reason for power losses between sim-dyno. Do you have any idea of the efficiency of the air-cooling system described in EngMod?
Not sure of your Eng mod , but the design of the fins I can help I have some papers , on them somewhere

Stephen

[dinamik2t]

Thank you!
Would you mean this? http://users.uoa.gr/~sph0800108/modenas_dinamik_forum/2T_Books/Air-cooling%20Effect%20of%20Fins%20on%20a%20Motorcylce %20Engine.pdf

I remember reading another document somewhere about head fin design, but I cannot locate at the moment.

[wobbly]

I have never done a sim of an air cooled, Neels was after a dyno run of a stock KT and pipe a while ago for some students using his code for a project.
But on the dyno for sure you need to simulate the air flow over the case /cylinder/head to get repeatable results.

[F5 Dave]

So is it fair to say that the closer to the edge the more critical temp is to performance?

Reason I suggest that is we spun up my mates VJ23 (70 degree Jap market only but derestricted) and the curves overlayed perfectly over 3 runs, there was a bit of delay between the runs & the engine got hotter. The test started at say 55* & ended at 71*. Couldn't pick the curves from each other.

Btw 60hp @ ~11,200 which meant 30hp for each 125 cylinder (ignoring less losses of a twin) on a std road engine that can run on 91 oct. Pretty good considering the squish is probably a mile wide. The old VJ22 does about 52 on similar dyno.

But because of the comp being low maybe it is [edit] more- tolerant of temp diff?

[dmcca]

Simply put, you MUST have the same head temp and case temp at the start of every test.


In a water cooled engine is it reasonable to just use coolant temp as a blanket temp reference instead of head, case and plug temp on an air cooled engine?

I've noticed using my digatron unit that coolant temp (taken at head exit) and plug temp are always within 20* of each other on my bike during normal riding and always move simultaneously... Pretty much what I expected as the coolant significantly masks the true plug temp.

[wobbly]

The KT100 is thermally borderline with a proper header and pipe.
Make anything more than about 17 at peak and the engine will go away after 3 laps on the track.
I spent around 3 months full time on the dyno, and could get over 20 Hp, but on track none of those pipes could be used in a race.
So I concentrated on generating a flat downsloping torque curve that gave plenty of bottom and overev power, with no hump in the graph that would over heat the finning.
As soon I did the engine would heat fade and loose around 20% of its power everywhere.

A watercooled engine should start all the tests at the same water temp,as I have found that a full house 125 will loose around 2 Hp if run at 70* instead of 50*.
The crank/cases heating up looses power as well,so I try and keep this as constant as possible.
I have never run a "stock " type bike engine, but I would guess that if you started the test at 70, you would loose power as it heated up further from there.
A CR125 engine as run in SKUSA box stock with a pipe would loose 1.5 if i overheated it during a dyno run from 6000 to 12000 - ruining the test.

[Frits Overmars]

...Frits is right ( as usuall ) about the acceleration dyno being the most useful. I set up the engine gear ratio to test, so it accelerates as it would as close to track conditions as possible. But an eddy current can be set up to work exactly like an inertia, simply by using the constant load mode. Then the absorber applies the same load to the engine all the time, just like a steel wheel or roller.Thanks for the flowers, Wob. But an inertia roller does not apply the same load to the engine all the time. In a situation where the revs do not increase, the roller does not put any load on the engine at all. Its load is acceleration-dependent and that is practically impossible to achieve with any brake; the brake governing software won't know what to do until after the 'event'.
Advantage is that on say a Dynojet you can easily dial up the load needed in % terms, to get the acceleration rate you want. We use that facility with a twist - program it to increase the load with roller speed.
Thus when doing an all gear run, the load increases just like the wind drag with increasing speed - so the acceleration rate decreases.
Perfectly mimicking the track conditions. Means you can dial in the ignition and fuelling at very high acceleration rates in the lower gears, then do the same at slower rates in 5th/6th.Right, mate. You can also use it to 'brake away' some of the engine torque and measure a strong engine on a light inertia dyno, and still achieve realistic acceleration times.

[wobbly]

Dead right Frits,but for the usual situation I encounter,where I build engines somewhere near well tuned to begin with, they are always trying to accelerate
the brake during a test - so I havnt encountered the "not enough power to accelerate the drum " syndrome.
Is this what you are alluding to?

[Frits Overmars]

Dead right Frits,but for the usual situation I encounter,where I build engines somewhere near well tuned to begin with, they are always trying to accelerate the brake during a test - so I havnt encountered the "not enough power to accelerate the drum " syndrome. Is this what you are alluding to?Yes, I tried to clarify the fundamental difference between acceleration-dependent loading of an engine and just applying a braking torque. We both agree that an inertial dyno is the best tool for developing competition engines, and that a combination of such a dyno with a brake (usually an eddy current brake) is nicer still, but at a cost. In case you do not have deep pockets, a simple inertial dyno is not only the cheapest choice, but also the best one.

[Yow Ling]

In case you do not have deep pockets, a simple inertial dyno is not only the cheapest choice, but also the best one.

Haha not many deep pockets in bucket racing, and the ones that are deep are Gorse lined

[Drew]

Haha not many deep pockets in bucket racing, and the ones that are deep are Gorse linedMine are so deep I can't reach anything in them. When I get brave and try, only then do I find the gorse.

Should the situation be so dire as to continue digging, I still come up empty because there was nothing to be hard to get in the first place.

Do I qualify to ride buckets?

[F5 Dave]

no, but show up & you can wave a flag.

[Drew]

no, but show up & you can wave a flag.I did that already! But don't tell the real racing fraternity, I've got them just where I want them for now.:yes:

[F5 Dave]

Ahh;- Lulled into that real sense of security. They'll never suspect a thing.

[FastFred]

<iframe width="420" height="315" src="http://www.youtube.com/embed/1Z6iXeaGVHY" frameborder="0" allowfullscreen></iframe>

A word to the wise, .... don't mess with this woman or her girl friends.

[Pumba]

A word to the wise, .... don't mess with this woman or her girl friends.

Um, WTF???

:confused::confused::confused::confused::confused: :confused::confused::confused::confused::confused:

[TZ350]

Wrong thread I think ....:no: but good shooting never the less.

[wax]

Thats random. But ok I will not mess with her :blink:

[kel]

Um, WTF???

We have been arming our women for the immanent invasion. Thats right, not only are they educated but they are also weapons savvy (and nice to look at). Fastfred is clearly using this forum to place our would me invaders on notice :blink:

[F5 Dave]

Has anyone tuned any 2 strokes lately? I haven't & had to endure some 4 stroke shenanigans last night. But we almost got an RD400 going. Ok, not even close. . . Maybe I'll get some time tonight to fettle my racebike (read: strip & flush the last of the piston pieces out of the bottom end).

[TZ350]

Has anyone tuned any 2 strokes lately?

270980

Chambers and I dug out his old GP/FZR combo that has been sitting in the shed for a while. It is an early setup with limited porting and a pipe adapted from a RG250. Last night we ran it up on the dyno, 22.5hp. And Bucket grabbed a few graphs to compare with the 20hp FXR's, I guess he will post them.

[F5 Dave]

Sounds interesting. Have you ever posted or have bog stock FXR curves on your dyno?

[TZ350]

Have you ... bog stock FXR curves on your dyno?

No never had a std road going FXR150 on the dyno, I would be interested in getting a base line if someone has one to try.

Not sure if these are good examples but:-

270982

14hp Stock FXR150 Bucket thats not running that well. Cut down pipe and muffler changed to something smaller and out of the way.

270981

17hp Stock FXR150 with bigger carb, std cams, cut back exhaust pipe with after market muffler fitted under the engine.