ESE's works engine tuner

[koenich]

Almost 35 years ago Frits...don't want downtalk the great effort and results we see from several people. Nor Jans achievements in any way.

But in the end it was Aprilias $ that could pay Jan to work full time on engines, a dyno facility, I'm certain a lot of engineers/technicans in the background making parts, all the prototypes,... which is necessary to achieve such results. My point just was that to develop a 25HP plus 50cc you'd need quite some time, parts and tools (= money), not talking about small batch industrialization requiring invest up front and then hoping to make a profit so you didn't bin your retirement fund.

[Niels Abildgaard]

Not even in the same time zone, Niels :msn-wink:. The 125cc Honda works cylinders of that era made about 44 hp at the gearbox exit which, according to your calculation method, would give their NSR500V 2x70 hp, a value that is not too far from their manufacturer's specification: 136 hp.


Hundreds. Any specific wishes?

The estimation method of sonic max limit of two strokers is maybee not fundamentally wrong.
If You have a picture of the Suzuki like the last one You showed of Thiel special homebrewed it will be lovely

[JdG]

https://youtu.be/oJcnaM-hB8Q

Zundapp crankcase, std. Derbi cilinder modified. Build in a Dutch shed by 2 brothers.

Lots of hours spend though...


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[Niels Abildgaard]

https://youtu.be/oJcnaM-hB8Q

Zundapp crankcase, std. Derbi cilinder modified. Build in a Dutch shed by 2 brothers.

Lots of hours spend though...


Verzonden vanaf mijn iPhone met Tapatalk

Very,very good.

Your 24.8 rearwheel for a 50ccm and the 52 from RA125 is a datapoint more.

52*(50/125)**.6666= 28.2 minus 12% gives Your 24.8.
We now have Two measurement based datapoints and an idea of magnitude of losses for almost fully develloped two strokes

[Frits Overmars]

The estimation method of sonic max limit of two strokers is maybe not fundamentally wrong.I would say that your method of determining engine power for engines with equal BMEP and different cylinder capacities via their angle.areas is basically correct.


If you have a picture of the Suzuki like the last one you showed of Thiel special homebrewed it will be lovely.Like I wrote, I have plenty pictures but I cannot post them all, so I will show a small selection of the 50-twin you asked about (but I could also show the 50-single, the 50-triple, the 125-2, the 125-4, the 250-2, the 250-4, the 500-2, the 500-4 and the 750-3).
347986 347985 347984 347983 347988 347987

[wobbly]

OK - great, we have a proven data point for a 50cc race engine on petrol making 28.2 CHp im guessing as the dyno video didnt show it @ 16500 rpm.
Thats a bmep of 15.3 Bar , just what I would expect , especially from a couple of Dutchmen in a shed.

Now compare that to what is supposed to be the " best " 30.5cc petrol engine on the market from Quickdraw - makes 8.75 Hp CHp at 16250 = 6.9 Bar = joke.
So now I know what can be done by a Dutchman in a shed = perfectly normal technically achievable performance.
Good , lets see what a Kiwi can do with Laser Sintering , CNC cases , Ti pipes and EngMod , all from the comfort of an office chair.

[Frits Overmars]

Suzuki 50-twin continued
347998 347997 347996 347995 https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=348000&stc=1&thumb=1&d=1607720518 (https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=348000&d=1607720518) https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=347999&stc=1&thumb=1&d=1607720518 (https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=347999&d=1607720518)

[Frits Overmars]

Suzuki 50-twin continued
348007348001348004 348002
The left-hand picture, by Kawai Mitsuo, is marked 'RK67', but in fact it shows the RK66, which had a much shorter connecting rod than its successor, the RK67.
The Kawai Mitsuo-picture also shows the third transfer port being fed through the piston, whilst the picture of my RK67 cylinder (center) shows that one year later the third transfer was directly connected to the crankcase.

[lohring]

Are there some model aircraft/boat classes where both spark ignited and glow engines compete?
The 2.5 and 6.5ccm engines have a ringless pistons and that can help produce as much power as they do
Has it ever been tried to modify a weedhacker engine with glow ignition and ringless pistons?

We did an evening of dyno runs on a 26 cc Quickdraw converted to glow ignition with a simplified WYK 33 carb. We couldn't get glow plugs to work. They either blew out the center or wouldn't light the glow fuel. The engine ran fine on the stock ignition on 15% nitro glow fuel, but burned the electrodes off the plug on 40% nitro fuel. We probably could have played with head volume and more glow plugs, but we had no incentive since we were after gasoline records.

Again, our experience with the CMB ringless piston design was poor. We weren't in the business of building complete engines; we went with the best available at the time. My friend, the late Jim Allen, claims he got 10 hp from a 26 cc Quickdraw by chroming the cylinder, running a higher compression toroidal head button, using his custom tuned pipe, and adding a custom 20 mm bore carb. I would love to see what a serious, modern 30 cc design could do.

Lohring Miller

[Niels Abildgaard]

Suzuki 50-twin continued
348007348001348004 348002
The left-hand picture, by Kawai Mitsuo, is marked 'RK67', but in fact it shows the RK66, which had a much shorter connecting rod than its successor, the RK67.
The Kawai Mitsuo-picture also shows the third transfer port being fed through the piston, whilst the picture of my RK67 cylinder (center) shows that one year later the third transfer was directly connected to the crankcase.

Thank You for some lovely 50ccm pornographs.Do You also have some of the final triple animal?
The picture here:

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=347997&d=1520911705

shows that electric transmission is worth a thought

[Frits Overmars]

Thank You for some lovely 50ccm pornographs.Do You also have some of the final triple animal?Yes Niels, I do have pictures of the 50cc triple and a lot of other Suzuki racers, about 200 in total. But it is rather impractical for me to post them one by one.
I would gladly ZIP the whole lot but I forgot how to upload zipfiles to Kiwibiker. Anybody?

[husaberg]

Yes Niels, I do have pictures of the 50cc triple and a lot of other Suzuki racers, about 200 in total. But it is rather impractical for me to post them one by one.
I would gladly ZIP the whole lot but I forgot how to upload zipfiles to Kiwibiker. Anybody?
............

You looking for another one?

https://www.youtube.com/watch?v=PcRWO-jvjDI

While we are waiting here is the one Hugh Anderson had here and sold to I think the Netherlands.
https://www.kiwibiker.co.nz/forums/showthread.php/151865-Old-multi-cylinder-bikes-of-the-50s-to-later-on-Japanese-British-Euro-etc?p=1130374843#post1130374843

https://www.kiwibiker.co.nz/forums/showthread.php/151865-Old-multi-cylinder-bikes-of-the-50s-to-later-on-Japanese-British-Euro-etc?p=1130616443#post1130616443

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=288082&d=1380532376

https://www.kiwibiker.co.nz/forums/showthread.php/151865-Old-multi-cylinder-bikes-of-the-50s-to-later-on-Japanese-British-Euro-etc?p=1130618964#post1130618964

[katinas]

So beautiful little engines, thank you Frits.
From spec chart, impressive air cooled twin RV62 250cc 42hp at 11000rpm.

Add few schemes of 1972 spec rotary valve racing outboard Veterok-70 350cc and Veterok-100 500cc (Konig copy). Interesting 350 cc power graphs with different
intake duration and different closing angle after TDC /fixed rpm. Both engines with same bottom, 54 mm stroke, just on 350cc cylinders with 45.3 mm bore.

[JdG]

Just to clear, that 50cc engine is not mine, nor did I have anything to do with it. I wish I was that good [emoji4]

I’m sure that Frits knows the Van Rossem brothers. Jan Thiel helped them a lot on a Dutch forum. As far as I know, this is the most powerful Dutch 50cc in pump fuel.


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[jfn2]

I have 2 questions. Why did ( not just Suzuki but a number of companies) lower the bottom of the ports below the BDC line? I know not much flow happens at BDC but it has to mess with the flow somehow. Also in the pic that Frits posted of the piston from the RK66 engine has grooves below the ring land. Were these used as a type of labyrinth seal. I notice some of the new 4-stroke pistons have the one above the ring. But I haven't seen them very often below the ring. One other question, how do I install this in a simulation program?

[wobbly]

jfn2 - Sorry to ruin your delusion buddy , but most all the flow occurs around BDC , via the large pressure delta across the Exhaust port created by correctly timed diffuser action.
At lower rpm the biggest depression occurs BBDC , it then advances thru BDC to ABDC as the fixed pipe length affects the arrival of the diffusers peak amplitude at the Exhaust port.
When the transfers first open there is more residual blowdown pressure in the cylinder , than pressure in the duct created by the piston descending - this is the sole reason for port stagger , the first transfer
to open , flows last.
The best pipes can suck the chrome off a towball for the greatest dwell time around BDC - thus the latest tuning trend is to increase the A port front wall angle right back toward the boost port
helping to reduce direct short circuiting created by very efficient diffusers.
Best example of this would be a stock TZ350 that simply refuses to make more power with a pipe bigger than 110 belly diameter.

As for having the transfer inner radius ending below BDC , maybe this was found to give a " better " flow regime when using elevator shaft ( love that term ) type ducts , as it attached the
flow to the piston early.
For sure in modern teecup ducts even small discrepancies in height, above or below , wreak the scavenging flow exit from the port.

And my guess re the groove below the ring was to lighten the piston , as it was probably derived from a die designed for two rings and had alot of unecessary skirt material between the top
of the small end and the top ring groove.

[porttiming124]

https://youtu.be/oJcnaM-hB8Q

Zundapp crankcase, std. Derbi cilinder modified. Build in a Dutch shed by 2 brothers.

Lots of hours spend though...


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Good morning all !
this forum is fantastic! thank you for sharing your expertise in 2-stroke engines!
in this video at 20 seconds for example have heard a pop?
what does that? thanks

[teriks]

Good , lets see what a Kiwi can do with Laser Sintering , CNC cases , Ti pipes and EngMod , all from the comfort of an office chair.
Im sure as h.. looking forward to follow this :)

[Muhr]

Yes it will be interesting to follow!

I myself spends Saturday night trying to master magic of super polish ...
And borrowed a 3d printer for carbon fiber / nylon. has managed to print the first part to the 50cc engine
Has also managed to cut some parts yesterday for manufacturing a connecting rod for the engine :woohoo:

[porttiming124]

Good morning all !
this forum is fantastic! thank you for sharing your expertise in 2-stroke engines!
in this video at 20 seconds for example have heard a pop?
what does that? thanks

sorry I did not copy the correct link! here is the good link to look at 20 seconds thank you


https://www.youtube.com/watch?v=6NwDSwxGpwM

[Condyn]

B port short side radius below BDC on these 1974 Yamaha GYT cylinders with the roofs axial way up. Why? I am completely confused on this one. By the way the elevator shaft phrase was coined by the great Kevin Cameron!

[wobbly]

Teriks - OK so here is the beginning of the project.
Baseline engine ( black sim ) is 31cc piston port on unleaded race gas , and the simulation is very close to the actual power curve supplied by the customer - who has his own dyno.
The initial stage of the project is to use existing engine parts that have proven to be reliable at 20,000, including a reed block from a Tiger King.
So a long stroke crank , with a new En39B billet much longer rod , with existing piston/bearings etc puts the new engine at 34.8cc ( 35cc being the class limit )
This is still very oversquare , always a bad idea , but this begins proof of concept for the EngMod optimised porting/pipe /new carb etc and the beginings of heading toward
what I consider as SOTA for bmep and piston speed.
Here is the result - the cases and cylinder are being designed in SolidWorks as we speak , and the Ti pipe is at the laser cutter already.

[wobbly]

Porttiming - the pops are blowback thru the carb , coming from either the ignition rev limiter or simply the carb going way rich well past the peak power rpm.

[porttiming124]

ok thank you wobbly

[peewee]

https://youtu.be/oJcnaM-hB8Q

Zundapp crankcase, std. Derbi cilinder modified. Build in a Dutch shed by 2 brothers.

Lots of hours spend though...


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that seems like a mighty sophisticated shed. in america the shed has only a lawn mower with a garden hose and a few shovels :lol:

[Muhr]

Yes it will be interesting to follow!

I myself spends Saturday night trying to master magic of super polish ...
And borrowed a 3d printer for carbon fiber / nylon. has managed to print the first part to the 50cc engine
Has also managed to cut some parts yesterday for manufacturing a connecting rod for the engine :woohoo:

Tried to make the rotor cover in Carbon nylon, would work if I make a disc against the rotary valve I think. (Also has one to be cast in aluminum)
Polishing was also quite ok, enough for a surface treatment.
Someone who has some tips on companies that are good at surface treatments such as "DLC".

[teriks]

Teriks - OK so here is the beginning of the project.
Baseline engine ( black sim ) is 31cc piston port on unleaded race gas , and the simulation is very close to the actual power curve supplied by the customer - who has his own dyno.
The initial stage of the project is to use existing engine parts that have proven to be reliable at 20,000, including a reed block from a Tiger King.
So a long stroke crank , with a new En39B billet much longer rod , with existing piston/bearings etc puts the new engine at 34.8cc ( 35cc being the class limit )
This is still very oversquare , always a bad idea , but this begins proof of concept for the EngMod optimised porting/pipe /new carb etc and the beginings of heading toward
what I consider as SOTA for bmep and piston speed.
Here is the result - the cases and cylinder are being designed in SolidWorks as we speak , and the Ti pipe is at the laser cutter already.
Wow, that standard engine is for sure how to flatten the curve... not always a good thing.
Id guess you'll get very close to your sim results. Even the 6.5 sim matches the limited data I have quite ok, after a bit of reduction of CE.

[teriks]

Tried to make the rotor cover in Carbon nylon, would work if I make a disc against the rotary valve I think. (Also has one to be cast in aluminum)
Polishing was also quite ok, enough for a surface treatment.
Someone who has some tips on companies that are good at surface treatments such as "DLC".
You sure are getting things done :)

I have had some stuff done at Ionbond: https://www.ionbond.com/about-ionbond/contacts-locations/sweden/
Youd have buy thru a company though, but given the waterjets etc Id guess that wont be a problem for you.

[Tim Knopper]

https://youtu.be/oJcnaM-hB8Q

Zundapp crankcase, std. Derbi cilinder modified. Build in a Dutch shed by 2 brothers.

Lots of hours spend though...


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The real numbers are 23 hp reed engine and 23 rotery engine official on dynoday every end of the year

[wobbly]

Condyn - nearly all the two stroke Jap engines from that period had the scavenging pattern as you describe with the B port up at around 45*, and its floor below BDC.
And there have been many examples of the boost port short turn lowered below BDC over the years , as they are angled up at 55+ - usually with a 1/2 moon concave curve , its something I have been meaning to try on a modern cylinder
for ages , but hard to rectify if its a fail.
The modern scavenging pattern reverses the axials , with the A port up at 25* + and the B at 15*- and I spent hours , years ago welding and epoxying up LC type ports to do exactly that.

[katinas]

Wob, Condyn, maybe this in theme. Quite by accident on Husqvarna TC65/85, we noticed that by rounding A and B the floor edges, up to r-3 mm, the power increased. I can’t say exactly why, but probably it helps mix flow back to transfers through the piston cutouts, after TDC and until the moment when A and B closed. With many others small modification on latest TC 85, all ended 12 hp at 7000rpm and rise without spots to 36.47 hp at 11756 rpm. from wheel.

[Muhr]

You sure are getting things done :)

I have had some stuff done at Ionbond: https://www.ionbond.com/about-ionbond/contacts-locations/sweden/
Youd have buy thru a company though, but given the waterjets etc Id guess that wont be a problem for you.

Thanks! I have heard some mixed experiences from them.



Wob, Condyn, maybe this in theme. Quite by accident on Husqvarna TC65/85, we noticed that by rounding A and B the floor edges, up to r-3 mm, the power increased. I can’t say exactly why, but probably it helps mix flow back to transfers through the piston cutouts, after TDC and until the moment when A and B closed. With many others small modification on latest TC 85, all ended 12 hp at 7000rpm and rise without spots to 36.47 hp at 11756 rpm. from wheel.

It is impressive!

36.47 hp at 11756 rpm It is 22nm at peak hp.

[teriks]

Thanks! I have heard some mixed experiences from them.
I have had mixed experiences too.
The crank pins on the MB40 was more miss than hit, but IMO thats mostly due to the loads and base material.
-I had a batch of shafts that were too soft and wore out way too fast, so tried to save some with dlc.

If I ever finish my own cases, Im trying shafts in "Uddeholm Vancron SuperClean (https://www.uddeholm.com/app/uploads/sites/43/2017/09/vancron-eng_p_2001-e4.pdf)", should negate the need of coatings.
Shafts are finished, but still a long way to go before I have running engines.

[Niels Abildgaard]

Wob, Condyn, maybe this in theme. Quite by accident on Husqvarna TC65/85, we noticed that by rounding A and B the floor edges, up to r-3 mm, the power increased. I can’t say exactly why, but probably it helps mix flow back to transfers through the piston cutouts, after TDC and until the moment when A and B closed. With many others small modification on latest TC 85, all ended 12 hp at 7000rpm and rise without spots to 36.47 hp at 11756 rpm. from wheel.

If the ultimate power of a two stroke is limited by port areas,as I think it is, we can rate these 36.47hp from a 85ccm with 52 from a RA125.

52*(85/125)**,6666=39.25 to be compared with Katinas 36.47.
Considering that the 85ccm has relative higher thermal losses it is awfull impressive for a private run project..

[Frits Overmars]

...on Husqvarna TC65/85 we noticed that by rounding A and B the floor edges, up to r-3 mm, the power increased. I can’t say exactly why, but probably it helps mix flow back to transfers through the piston cutouts, after TDC and until the moment when A and B closed.Katinas, I think I understand your message, but I am not 100% sure. Are you talking about rounding off the inner edges at the bottom of the cylinder bore, as in the Aprilia picture below, or are you talking about the floors of the transfer ducts where they enter the cylinder above the piston?
348042

[Muhr]

If I ever finish my own cases, Im trying shafts in "Uddeholm Vancron SuperClean (https://www.uddeholm.com/app/uploads/sites/43/2017/09/vancron-eng_p_2001-e4.pdf)", should negate the need of coatings.
Shafts are finished, but still a long way to go before I have running engines.

Hope to see more of that project !!


If the ultimate power of a two stroke is limited by port areas,as I think it is, we can rate these 36.47hp from a 85ccm with 52 from a RA125.

52*(85/125)**,6666=39.25 to be compared with Katinas 36.47.
Considering that the 85ccm has relative higher thermal losses it is awfull impressive for a private run project..

It's BMEP at 16.36 bar, right?
Hats off

[flyincat]

Part of this is also due to the fact that to fit the CR250 block in place meant that the petal exits were off bore center by 6mm - the CR125 is 6mm narrower , so it can be put back on center with an adapter plate
then a stuffer plate fitted down one side.

So one lesson I learned is that asymetric intake regimes loose power - be it an offset block or even worse sideways angled manifolds.


If reed engines are clearly sensitive to asymmetric intake flow, how does the rotary intake work so good coming in straight sideways?? Does it have to do with not using all of the reed area, with most of the flow biased to one side of the reed assy, and not so much to do with where the flow goes inside the crankcase? Thanks in advance!

[katinas]

Muhr, Niels one notice, this result was without air filter and torque was 22.28 Nm at 11542 rpm. With an air filter, max power range dropped between 35 and 36 hp. Stock 2020 85cc on our dyno shows 11.8 hp at 7000rpm until 27-27.7 hp at 11335 rpm. torque 18.22 at 9989 rpm.

Frits, yes its about the floors of the transfer ducts where they enter the cylinder. On SX 65 this add 0,7hp on several engines, but on 85 we never test this alone, just together with other modified things.
Probably this would reduce the power of the engine, where the piston sides cutouts is low, and transfers is masked when piston is at TDC, like on Aprilia rotary valve engine.

Looks like, from all KTM/Husky 50, 65, 85, 125 cc engines, 85 is most successful Austrian engine. And engine modification could be done without any additional kit parts, only modified stock.
I am still wondering how good is 85 std exhaust pipe. The only modification on it, was a smaller tail pipe insert, from stock 19.5mm to 17 mm. We reduce it step by step until mid range started to drop with 16.5 mm. But max power still rises.

[wobbly]

So this is where we run into trouble with the numbers , that simply cant lie. IF the TC85 has 36.46 WHp @ 11,756 then
with the usuall 12.5% losses to the crank we get 41.05 CHp.
At 11756 rpm ( a ridiculously low 19M/s piston speed ) this equates to 18.39 Bar.
Sorry - simply not possible on petrol ( and for sure never been done , as its way better than Mr Thiel even dreamed of ).

Now , if you rev the thing to 15500 as it should be ( 24M/s ) then the BMEP is 13.94 Bar - easily achieved by many a clever Dutchman or a Kiwi in a shed for that matter.
Not to put a finer point on it - someones dyno is telling porky pies , unless the numbers have been misquoted somehow.

[dutchpower]

I think Katinas you have around 30 hp now and that is pretty good ( stock TC 85 lays around 22 hp )

[wobbly]

Flyincat , I think that the angled manifold is the worst offender . I did days of flowbench testing of the SKUSA CR125 intake when using the straight RS125 rubber was effectively stopped , by
banning the use of the riubber stuffers if opting to use that manifold.
The flow exiting the petals on the inner short turn radius was so bad it was hard to measure using a velocity probe.
After cutting a heap of petals and using asymetric backups I managed to get something like 60/40% and power went up 1.5Hp.
The new petal setup biased flow upward under the piston as well as pulling it around to the LH side.

In the CPI Cheetah cylinder the LH/RH bias from the reed tips would have had a direct result on the flow thru the big Boyesens and thus directly into the transfer tunnels.
And the whole reason Jan liked the idea of the rear mounted RV was to eliminate the asymetric flow regime of the side mounted version.
The RSA was a sucess , power wise , but had a down side in that the front exit pipe limited the positioning of the engine in the frame , so it never handled as well as the RSW.
Jans opinion now I believe is that a RV on each side would be the best route to ultimate performance.

[katinas]

Wob, Duchpower, yes its always difficult to say real power with different dyno, but latest stock 2020 SX/TC 85 dyno graphs from others, shows very similar 27hp and 18Nm and identical 11.8 hp at 7000 rpm results.
From 3.27 https://www.youtube.com/watch?v=_TvRVPJrrN4

[dutchpower]

Wob, Duchpower, yes its always difficult to say real power with different dyno, but latest stock 2020 SX/TC 85 dyno graphs from others, shows very similar 27hp and 18Nm and identical 11.8 hp at 7000 rpm results.
From 3.27 https://www.youtube.com/watch?v=_TvRVPJrrN4

That are crank hp Katinas

[katinas]

That are crank hp Katinas

Thank you, so its better sensitive to feel the difference from modification.

[Muhr]

Thank you, so its better sensitive to feel the difference from modification.

We use the same software and dynos that VHM uses and I would say the same thing as Duchpower, most likely to be able to compare data between them (or the the big brother of the one vhm uses)
I have worked on a few Tm mx85 in recent years and have not seen that we are left in the dust. we have quite strict regulations where we can make exhaust systems but not modify anything on the engine. We get out around 30 crank. (I ended up with a 17.5mm reduction)
I do not think this takes anything away from your performance increase

[wobbly]

Notice that the VHM dyno result has a weather station connected , but the correction factor is 1.00 - one simple way to make the dyno lie.
I did wonder why we could never get near the results they posted about how fabulous their KZ pistons were.
Sure , they are doing comparative tests , but now their actual numbers are not reality.
But anyway - its just not possible an 85cc @ 11756 rpm is making 41 CHp with a resultant bmep WAY better than an RSA125.

[andreas]

This 85 cc would be reed inducted, but it has a few advantages over the aprilia, lower rpm while being just over 2/3 the size. Also the rpm is so low it can probably use the second reflection exhaust pulse at peak power- enough for that astronomical bmep??

[wobbly]

"Astronomical bmep " is the key phrase here.
Being a reed engine is an absolute ,proven , guarantee that it will make around 10% less power than a equally developed RV , and as for making peak power at just 19M/s piston speed
further reinforces the determination that the facts are seriously in question.
Is anyone seriously agreeing that a reed 85cc on petrol has been so well developed that it makes completly off the planet comparable Hp to an RSA125 at a piston speed suited to a chainsaw.

[katinas]

Notice that the VHM dyno result has a weather station connected , but the correction factor is 1.00 - one simple way to make the dyno lie.
I did wonder why we could never get near the results they posted about how fabulous their KZ pistons were.
Sure , they are doing comparative tests , but now their actual numbers are not reality.
But anyway - its just not possible an 85cc @ 11756 rpm is making 41 CHp with a resultant bmep WAY better than an RSA125.

Wob, VHM dyno result, like Duchpower said, is crank hp. We have two TC 85 2020, one with still absolutely stock engine, other modified so it was easy to compare. If VHM power graph of stock 85 is correct, that shows 27 hp from crank, it is the same that we found on our dyno for std engine. So modified engine power shows crank 35-36 hp, but just measured from wheel.
And yes, absolutely agree that 41 Chp at this rpm from 85 cc impossible, just maybe with turbo charging that ended immediately with melting piston.

[dutchpower]

VHM TC 85 is 27 hp incl. exh/head/piston/that air thing

27 hp less vhm parts is 25 hp 25 hp to the wheel is 25 hp - 3.125 hp (12.5 % ) 21.875 hp


Did you test both stock bike's !!!!!

The higher you make exh. degree the beter stock pipe

Your upgrade is oke only not your numbers

[katinas]

VHM TC 85 is 27 hp incl. exh/head/piston/that air thing

27 hp less vhm parts is 25 hp 25 hp to the wheel is 25 hp - 3.125 hp (12.5 % ) 21.875 hp


Did you test both stock bike's !!!!!

The higher you make exh. degree the beter stock pipe

Your upgrade is oke only not your numbers

Thank you again for correction. So, 25 hp is what we needed to set for std engine, than modified could be 33-34 hp from crank.
Yes we tested both std, but one new earlier this year with 27 hp, other little used, just month ago 27.7 hp.

We didn't change blowdown, but rise cylinder until mid range started to drop. This gave 1.2 mm base.

[Muhr]

Did not see it yesterday when I looked in the cell phone.

[Muhr]

Thank you again for correction. So, 25 hp is what we needed to set for std engine, than modified could be 33-34 hp from crank.
Yes we tested both std, but one new earlier this year with 27 hp, other little used, just month ago 27.7 hp.

We didn't change blowdown, but rise cylinder until mid range started to drop. This gave 1.2 mm base.

Found this picture from the 85 tests we did. has unfortunately happened more than once.
Was a bit too aggressive with ignition and 16.75mm reduction along with a cdi that is not adapted to the RPM we want to run:corn:

[katinas]

Muhr, yes with 17mm insert we retarded ignition with woodruff key, as there is no possibilities to adjust stator on TC85. But mainly, because of milled spark that protruded deeper to combustion chamber. Maybe this proteced piston.

[porttiming124]

348047348047

Hello !
here is a snowmobile cylinder!
look at the big radius in a corner of: B: port!
just on the side of: C: port.
Do you think it's in order to open progressive or is it to give more support to the ring gap?

[wobbly]

If the ring gap is between the B & C then it doesnt need that radius at all.
Saying " opening progressivly " is another way of saying , making less power by reducing the transfer area.
Unless there is no hook on the B rear wall , and this is some wierd attempt at reducing the B inertaction with the C flow.

[porttiming124]

it is a 2 ring piston with ring gap between the b and c port!
and yes there is a hook in the b port.

[wobbly]

Be the first thing I would grind out - if it needs more transfer STA , but how the hell can that be modelled in EngMod.
And wow , look at the step in the A transfer roof , never seen that before - a good way ( just maybe ) to help stop short circuiting up to the Aux.

[porttiming124]

I also removed the radius!
this is how i did in engmod.348049348050

[porttiming124]

Regarding the A port with two steps(2.8mm) in engmod I averaged the 2 heights to have the right area in my opinion!
on the other hand by doing this I am aware that I do not have the right blowdown!
what would you do with that?
thank you

[wobbly]

I cant see the numbers , too small and they are blurry if I enlarge them.
See if you can post better images first.

[porttiming124]

larger image but I just realized what is not common sense sorry wobbly

[porttiming124]

another try

[andreas]

Maybe treat the A port as two separete ones.

[wobbly]

So get rid of the big radiuses , and split the A port into two = 7 port.
Whats the STA page look like then.

[porttiming124]

very good idea
I will do it in 7 port today and I will get back to you with the STA

[philou]

Any idea which resin to use for mould intake rubber?


https://youtu.be/B-rb4bhaQ1k

[porttiming124]

here is the result with 7 port with the true height !the blowndown is now insufficient

[philou]

porttiming124 use "print screen" and past to Paint

348067

[Frits Overmars]

Good morning all !
this forum is fantastic! thank you for sharing your expertise in 2-stroke engines!
.....
sorry I did not copy the correct link!
.....
Hello !
here is a snowmobile cylinder!
look at the big radius in a corner of: B: port!
.....
it is a 2 ring piston with ring gap between the b and c port!
.....
I also removed the radius!
.....
Regarding the A port with two steps(2.8mm) in engmod I averaged the 2 heights to have the right area in my opinion!
on the other hand by doing this I am aware that I do not have the right blowdown!
.....
here is the result with 7 port with the true height !Portiming124, are you aware that you used 12 exclamation marks in 6 days on this forum alone?
You are in danger of exceeding your allocated amount of exclamation marks before the end of the month.
But do not fear, there is solution: in this forum it is permissible to end a sentence with a plain and simple period.
Sorry, I couldn't help myself :p. During my stay in Germany I seem to have developed an allergy to exclamation marks and prohibition signs 348068

[porttiming124]

Sorry frits I will be careful.

[porttiming124]

porttiming124 use "print screen" and past to Paint

348067
thank you philou

[andreas]

Haha, Porttiming your lack of b-d area is very common. It seems there is room to widen the auxillaries quite a bit, maybe even raise them a little relative to the main but there is a thin line before ex pulse get compromised. Remaining after that is only to raise all of them, this has a y- pipe? I think they work well with long ex-durations btw, but the Engmod can probably tell you all this.

[wobbly]

Achtung - not only are these Dutchmen bloody clever 2T tuners, they have a better grasp of propa English than many of us natives.
But re the 7 port ski engine , now that is a seriously wierd scavenging regime.
More especially as the B port is lower than the C , that are now C and D.

But , I have a feeling the axials are going to be wierd as well - post the transfer layout page .
I use Gadwin Printscreen , free and way more user friedly at copy/pasting any part , or all the screen to any file or printer.

I would lift the C ports about 1/2 way between the A and D , this will give more transfer STA again.
Then mod the Aux to get the Blowdown STA back in line , looks like the front top corner could go closer to the main Ex as well.
And get rid of those horrible port chamfers , completely unecessary.

[dutchpower]

In plain english How the hell you get those numbers in real live engine :crazy:

[wobbly]

God save us - the axials are a nightmare 8-17-9-50.
How people ( I wouldnt be kind and call them engineers ) actually got paid to produce this complete rubbish is beyond me.
No other two stroke in the world has ever had such a complete mess , looks to me like its not even possible to "fix " by dropping the cylinder and regrinding everything.
Maybe if the Aux floor is lifted , you could start again - as the Aux roof is 6.2mm lower than the main - wtf , gets weirder every time I look.

[porttiming124]

look at the port layout (I put the cylinder upside down so that you can see the roof of the 'a' port) and also I removed the radius in the upper corner of the 'B' port as wobbly to recommend thank.

[porttiming124]

Achtung - not only are these Dutchmen bloody clever 2T tuners, they have a better grasp of propa English than many of us natives.
But re the 7 port ski engine , now that is a seriously wierd scavenging regime.
More especially as the B port is lower than the C , that are now C and D.

But , I have a feeling the axials are going to be wierd as well - post the transfer layout page .
I use Gadwin Printscreen , free and way more user friedly at copy/pasting any part , or all the screen to any file or printer.

I would lift the C ports about 1/2 way between the A and D , this will give more transfer STA again.
Then mod the Aux to get the Blowdown STA back in line , looks like the front top corner could go closer to the main Ex as well.
And get rid of those horrible port chamfers , completely unecessary.

wobbly I checked with the piston to widen the auxiliary port exaust towards the center of the cylinder as you have drawn in red and I am at 1-2 mm from the pin of the piston
so yes I can go there a little on this side but not much, I will also go there on the side of the main port,
if I put the auxiliary ports 6 degrees lower than the main port, is that correct?
thank you

[F5 Dave]

That's odd. Looks like a very nice casting though. Transfer the aux further out to the ex union. Transfers look pretty shallow from a sweeping inner point of view.

[wobbly]

The Aux are at 181* Duration now , Vs the 201* of the main port - I would go up to 191* but the transfer axial angles are the biggest issue.
How you fix them to be something normal like 25* 15* 55* I really dont know.

[porttiming124]

ok perfect .
in general on an engine which is well designed, what should be the height of the bottom of the auxiliary exaust port?

[wobbly]

If its done properly the Aux can be below the A port timing edge.
Here is a TM homologation diagram - with a small mod I make that puts the top corner over the small end pin.
But as the exit angle is very shallow , there is minimal effect from port linking so it makes more power.

[andreas]

Maybe it's an acquired taste but I don't hesitate to use epoxy in the transfer ducts. Better have the glassfiber kind, that way chunks won't fall out and you can arrange so that it is mechanically locked.

[philou]

In Facebook


348089

Translate in English :

Hello, after making the modification to cool the exhaust duct on a cagiva mito cylinder.

I have the problem of having the exhaust gases too cold. From the usual 550 degrees I only have 440 degrees.

The carburetion is perfect. Do I have to change the ignition advance?

[andreas]

I think you have to question whether he actually tested this, bacause how would it circulate, and how would it not leak.

[philou]

A part closes the conduits for sealing

348095348096348097

[wobbly]

Not only does the implementation look highly suspect - just about impossible for it not to leak , but how can the carburation be " perfect " at 550* or 440*.
Neither number are even close , on track or a dyno.
My original test was on a B homologation cylinder , unwelded at the time to reduce the exit area , and it would leak vey easily until I discovered Loctite Master Gasket in a syringe.
The later cylinders had much more vertical area for the slots and had no issues.

[nitro2tfx]

I haven't been on here in a long time, what's the trick to getting a jpg to show directly in a post (not as an attached thumbnail).

I have the jpgs loaded on Dropbox but adding the Dropbox links to the post doesn't seem to do anything according to the preview.

Thanks.

Anyway the thumbnails show high speed RECORDED pressure data (cylinder, intake, exhaust) that I promised ages and ages ago. I planned to have crankcase pressure too but will have to do that another time. Yamaha Banshee with some mods, details to follow.

[porttiming124]

If its done properly the Aux can be below the A port timing edge.
Here is a TM homologation diagram - with a small mod I make that puts the top corner over the small end pin.
But as the exit angle is very shallow , there is minimal effect from port linking so it makes more power.

thanks wobbly.
I took the tm digram and converted it (roughly) to my bore and stroke to be able to insert it into my cylinder to give me a visual idea of ​​the difference.
woow quite a difference.
ports A and B are larger, port C is similar.
my biggest problem if i want to try to get close to your diagram is the divider between port a and port b.
either I remove it and remake one and I weld it in the right place (very difficult)
the other option would be to widen port A as much as possible towards port B while keeping the current divider (easier)
for the auxiliary exaust port I can reshuffle it with solder.
for port A I can rebuild the exaust side as well as the top also with solder.
to widen the B port I will have to convert or modify my piston 2 ring to a single ring with the ring gap in the center (something I never did) of the C port.
it's a big project but i'm looking at all the options. thank you

[andreas]

A part closes the conduits for sealing

348095348096348097
Looks like a different cylinder-And that yellow stuff is trying to tell you something.


Not only does the implementation look highly suspect - just about impossible for it not to leak , but how can the carburation be " perfect " at 550* or 440*.
Neither number are even close , on track or a dyno.
My original test was on a B homologation cylinder , unwelded at the time to reduce the exit area , and it would leak vey easily until I discovered Loctite Master Gasket in a syringe.
The later cylinders had much more vertical area for the slots and had no issues.
Exactly.

thanks wobbly.
I took the tm digram and converted it (roughly) to my bore and stroke to be able to insert it into my cylinder to give me a visual idea of ​​the difference.
woow quite a difference.
ports A and B are larger, port C is similar.
my biggest problem if i want to try to get close to your diagram is the divider between port a and port b.
either I remove it and remake one and I weld it in the right place (very difficult)
the other option would be to widen port A as much as possible towards port B while keeping the current divider (easier)
for the auxiliary exaust port I can reshuffle it with solder.
for port A I can rebuild the exaust side as well as the top also with solder.
to widen the B port I will have to convert or modify my piston 2 ring to a single ring with the ring gap in the center (something I never did) of the C port.
it's a big project but i'm looking at all the options. thank you
I realize you're thanking Wobbly. Just what sort of solder are you reffering to? as you mention welding also.

[porttiming124]

Hello Andreas.
i thanked wobbly for providing me with the tm certification diagram to help me understand the port layout.
for welding I am talking about tig welding.
a friend of mine is a welder for prototype helicopter projects, he has very small, pencil-sized welding tools. for example some time after having stroked a cranshaft I had too much transfer port duration so to lower the port he reshuffled the edge.
then I had the nickasil redone and finally I filled it with jb weld epoxy.

[porttiming124]

Just a little parenthesis to tell you that I speak French.
I understand English fairly well but for the spoken word I work hard with my friend (google translate) to correct myself and allow me to communicate with you.
if you see incorrect verb tenses or anything else that is not perfect it is not intentional.
thank you.

[andreas]

Hello Andreas.
i thanked wobbly for providing me with the tm certification diagram to help me understand the port layout.
for welding I am talking about tig welding.
a friend of mine is a welder for prototype helicopter projects, he has very small, pencil-sized welding tools. for example some time after having stroked a cranshaft I had too much transfer port duration so to lower the port he reshuffled the edge.
then I had the nickasil redone and finally I filled it with jb weld epoxy.

Ok, solder here is for elctrical component thats why I asked. You work fast.

[JanBros]

anybody recognises these exhaust ?

these had the white label with "KR1" attached to them but they seem to need a long flange on the cylinder to slide them over to fit, and the tailpipe comes out way too low for KR1's

http://users.telenet.be/jannemie/exh%201.jpg

I can't remember where I got these, but they don't fit a KR1. the support on the belly is all wrong.

http://users.telenet.be/jannemie/exh%202.jpg

both are after market and very low on weight

[andreas]

I understand you speak French, I also understand what you are saying (probably).

[Frits Overmars]

... the thumbnails show high speed RECORDED pressure data (cylinder, intake, exhaust)Thanks Nitro, I love TFX recordings. But yours make me wonder about the high exhaust pressure spike around TDC. Connecting exhaust pipe and crankcase at TDC via a shortened piston skirt would be a bad idea with such a pressure profile. It would also annihilate exhaust wave superposition at EO. For comparison I dug up a 12-year old TFX recording of a 125 cc kart engine at 12775 rpm.
Its exhaust pressure profile is not ideal either, but it shows quite a difference with yours. What exhaust timing did you use?
348136 348137

[nitro2tfx]

Thanks Nitro, I love TFX recordings. But yours make me wonder about the high exhaust pressure spike around TDC. Connecting exhaust pipe and crankcase at TDC via a shortened piston skirt would be a bad idea with such a pressure profile. It would also annihilate exhaust wave superposition at EO. For comparison I dug up a 12-year old TFX recording of a 125 cc kart engine at 12775 rpm.
Its exhaust pressure profile is not ideal either, but it shows quite a difference with yours. What exhaust timing did you use?
348136 348137

Just to be clear this is not an optimized exhaust, nor optimized engine in any way. We haven't physically done anything to the engine yet other than spruced up the fuel and timing a bit, and added the sensors. What you are looking at is a recording of what things look like inside the engine "as received" (plus ignition timing/fuel) at one engine speed.

All of the traces are from a stock Banshee engine that has a few typical aftermarket Banshee bolt ons added on, the exhaust is a stock Toomey T6 exhaust (broad powerband pipe), V-Force reeds, 33mm PWK carbs (no Power Jets), Cool Heads, all common as mud Banshee aftermarket bolt-ons lol. Other than that just the ignition timing bumped up and the fuel spruced up.

Initially we will make some more fuel changes and maybe an intake revision, before doing any porting or exhaust changes. At some power level blowdown will limit things and porting will have to be done before continuing on, but we are over 100 IHP and haven't touched the ports.

I might add that the recorded data was taken onboard the Banshee on the fly, it was not done on a dyno. Gearing was changed from 14/41 to 19/38. Fast trail riding.

I will post some more info, different engine speed etc.

[wobbly]

The recorded pressure diagrams have one issue that needs addressing.
Where is the Exhaust sensor in relation to the piston.
If the distance /time factor is not taken into account by the software , then that spike that is shown at tdc , wont be anywhere near tdc.
If the sensor is 150mm from the piston , then that spike , a snapshot in time ,will have taken a significant number of degrees of crank rotation to arrive at that point.
A function of the wave speed , and rpm.
This is why Neels code has a fixed wave snapshot at the port face , then a second wave showing whats happening at a set distance from the port.
In this case the pressure diagram is meaningless , but other metrics such as wave Mach can be observed.
Many highly reputable SAE papers on engine simulation Vs real data , including those of Blair and Fleck et al from Queens , have been presented showing wave forms where this time smear is completely ignored.
And if one wants to get really pedantic , the pressure traces , should also be labelled as rightward or leftward propogated ie is the pressure rise coming from the port , or the reflected returning pulse.

[wobbly]

Portiming124 - Bonjour mon ami . OK so if you are well versed in removing the chrome , and welding the ports or dividers , then that cylinder could easily be fixed.
If thats the case , then get rid of the A port step , lift the bottom outer corner of the Aux port , and as you say get rid of the second ring and move the top pin over the boost port.
Then epoxy up the duct roofs to get modern axial angles.
Depending upon the end use , it would be much easyer to implement reverse stagger , leave the A port low and lift the B , C port 4* of duration higher , like the Aprilia scavenging pattern.
And please dont put any solder in the cylinder except to check the squish.

[nitro2tfx]

The recorded pressure diagrams have one issue that needs addressing.
Where is the Exhaust sensor in relation to the piston.
If the distance /time factor is not taken into account by the software , then that spike that is shown at tdc , wont be anywhere near tdc.
If the sensor is 150mm from the piston , then that spike , a snapshot in time ,will have taken a significant number of degrees of crank rotation to arrive at that point.

No issue, the sensor is a little over 2 inches from the piston. 6 inches would be WAY too far for the reasons you mentioned, and too close to the piston is also not good as you get localized effects.

This is just a Toomey T6 pipe, bone stock, not a TFX pipe nor customer pipe, and so far I have only posted at one engine speed, naturally things are different at different engine speeds.

There are several things wrong with this pipe (easy to see on the trace) if one's goal was max power/torque, the T6 is a decent broad powerband pipe. At some point we may record pressures for a higher power type pipe, just for interest's sake and comparison sake. I can post that too, then we can see how much is left on the table beyond that. There's plenty of power to be made yet before getting into another pipe though.

[flyonly]

Any idea which resin to use for mould intake rubber?


https://youtu.be/B-rb4bhaQ1k

Philou.

Did you get a response from anyone or work it out. I am interested also


Sent from my iPhone using Tapatalk

[Muhr]

Philou.

Did you get a response from anyone or work it out. I am interested also


Sent from my iPhone using Tapatalk

Do not know if I know any good resin, but 3d printing might be an option

I think intakes are often made of PF rubber

https://m.youtube.com/watch?v=d9FAEArjMms

[husaberg]

Pretty sure n the site or one of the videos he covers what the rubber was for the RD ones have posted them before he does a very nice job.
https://precisiontradingsystems.com/inlet_rubbers.htm
https://precisiontradingsystems.com/inlet_videos.htm
Also a guy on the KR1 site was making 35mm intakes, BDK were/are selling them.

http://www.kr-1s.co.uk/forum/viewtopic.php?t=5197

[peewee]

and move the top pin over the boost port.
.


that reminds me i just did another set the other day. tough little buggers trying not to blow the corner edge off and you only got one shot to get it right. proffesional machinist in oregon united states fucked up my yami cylinders and punched them to 68mm instead of 66 but to make matters worse the left cyl bore vertical centerline didnt intersect the comb chamber center. no choice but to drop in sleeves and start over . the only good news is im back at 64mm

[philou]

Do not know if I know any good resin, but 3d printing might be an option



Thanks you reply,

In 3d printing what is the duration over time?

How much is the shore hardness?

[Frits Overmars]

And if one wants to get really pedantic, the pressure traces should also be labelled as rightward or leftward propogated ie is the pressure rise coming from the port, or the reflected returning pulse.Call me pedantic.Putting two sensors some distance apart, say a distance equivalent to 20 crankshaft-degrees at rpm of max.torque, would give me all the info I need.


Portiming124 - Bonjour mon ami.... Please dont put any solder in the cylinder except to check the squish.Pauvre ami, he has to live with a language in which the word souder can mean weld, solder and braze :scratch:.

[Peljhan]

Hello.

To introduce myself first. I am Kristjan from Slovenia and I race with Tomos 50cc at Grobnik circuit at classic 50 event. Did also some 60cc kart racing as a kid.
I built Tomos D6 replica and now building Tomos GP77 replica with some freetech50 stuff developed (I must find 50cc thread here to post some more).

I am reading this thread for long time now (still trying to catch up at page 1500.. :sweatdrop ). It is awesome to read from you guys and thanks for sharing all your experience.

To add a little of my own. I 3D printed intake manifold for my Cagiva Mito for Dellorto 38 carb. First out of plastic (black part) with rubber (white part). You can see how I joined them together. Plastic cracked after few dyno pulls. Than I printed it completly from rubber and when I bolted it down, it made a little opening on sides. I quick fixed that because I needed bike for riding to work. I also printed matching insert.

Further development would be to print first few layers, insert laser cut alu or steel sheet plate and print the rest. Plate would distribute pressure evenly on cylinder for nice seal. Unfortunately development was stopped as I crashed with my Mito and broke my back, dislocated hip etc. Now I came from rehab after 6 months, so I have some free time to further read this forum and maybe contribute :)

[andreas]

Very nice.

[wobbly]

You are dead right Frits ,two sensors would give exactly what is needed , but with the processing power in my phone its way easyer to track the crank rotation and the wave amplitude against time.
The whole return wave is displaced in time, thus can be calculated to be shown graphically with the correct relationship to the crank sensor.
Still cant believe the intellectual Hp that completely missed that basic physics.

And in the spirit of learning something every day , the Mito reed stuffer as shown would be easily the worst shape I have tested on the flow bench , and dyno.
The shape should be convex on the sides , not tapering inwards to nothing.
Worst shape , to best , we are talking nearly 2 Hp in 50.

The worst bastardization of so called English is done by the Yanks - they invented the word " soder " that no one else in the world can even remotely understand.
Simply as they are too lazy to include the L in solder.

[Peljhan]

As I said, I was in a hurry to get on the road, so I modeled first shape that I imagined :D
Thanks for that. Would be interesting to try it on a dyno when I repair the bike.

[nitro2tfx]

The whole return wave is displaced in time, thus can be calculated to be shown graphically with the correct relationship to the crank sensor.
Still cant believe the intellectual Hp that completely missed that basic physics.



Not sure who would have missed that ?

There are quite a number of waves happening, particularly in a bad pipe design, and it takes surprisingly little in the way of adjustments to a pipe to go from good to bad, sometimes just the fabrication process itself.

I am hoping Neels is still on here and uses the one engine speed exhaust/intake pressure trace that I posted, along with the engine details to gravitate to the right bit of input tweaks in his software, creating a similar graph to the recorded one, then go from there in the discussion using different engine speeds.

[Muhr]

Thanks you reply,

In 3d printing what is the duration over time?

How much is the shore hardness?

I would certainly not say that I am an expert on flexible filaments but there are very many brands. Then there are also several different writing methods such as extrusion (FDM), SLS, SLA.
flexible filament made by the manufactur that make the printer I use I think is at 60 in shore.
which may not be optimal for what you want to do.

below an attempt to simulate the dellorto rubber I intend to use for the 50cc engine I am building

[wobbly]

Neels code has the functionality already to show exactly the same graphical data as you have posted.
Here is the closest I have to a Banshee 350, this is Henise's TZ350 with reed conversion that holds the LSR for non streamliner on petrol at Boneville @ 170.519 mph
showing Exhaust and intake pressure ratio @ 8000 rpm.
Can you expand the X scale to show only 360* total ( ie one cycle ) centered on BDC , as this is probably the most critical area of pipe design we need to be looking at.
Plus add the case pressure ratio as well , on the same graph , as this enables optimum tuning of a reed engines intake length.

[ken seeber]

A question of logic:

Old mate over here in the land of Oz is doing a 35 cc RC engine, essentially with a scaled down RSA KZ cylinder format, using a 38 mm piston.

What piston to bore clearance?

A Ø54 KZ runs around 0.07 clearance with a coolant temp of say 45 deg C. Using this as a guide, and scaling, this would be 0.07 *38/54 = 0.049. Now, the RC engine will be drawing in lake/sea water at say 20 deg. Assuming the piston remains at the same temp, but the plated aluminium bore runs 45-20 = 25 deg cooler. This would mean it expands less, to the tune of 38*25*0.000024 = 0.028.

So, a suggested clearance would be 0.049 + 0.028 = 0.077 = 0.003 inches

Sounds a lot, maybe wrong on the assumption that the piston remains at the same temp as a KZ, however note that these things run for either 8 or 12 min heats, full throttle for 100%, no cooling periods as for gear changing and backing off for a corner. Not to dissimilar to speedway karting where a 54 piston in an aircooled engine might have its clearance increased to 0.13 from 0.07 for a sprint kart circuit.

[Vannik]

I am hoping Neels is still on here and uses the one engine speed exhaust/intake pressure trace that I posted, along with the engine details to gravitate to the right bit of input tweaks in his software, creating a similar graph to the recorded one, then go from there in the discussion using different engine speeds.

Clint,

I am still here, a few times a day!

I do not have a Banshee model, if someone has one or a port map I can create one and run a few sims.

Neels

[nitro2tfx]

Clint,

I am still here, a few times a day!

I do not have a Banshee model, if someone has one or a port map I can create one and run a few sims.

Neels

Hi Neels, sounds good. I don't have a port map in hand at the moment as porting is something that will be done later on, so ports haven't even been looked at yet. Yes I know porting is more often done first than last lol, as it is a no-brainer, but the goal for this Banshee is probably a whole lot different from other people's Banshee projects.

[nitro2tfx]

Neels code has the functionality already to show exactly the same graphical data as you have posted.
Here is the closest I have to a Banshee 350, this is Henise's TZ350 with reed conversion that holds the LSR for non streamliner on petrol at Boneville @ 170.519 mph
showing Exhaust and intake pressure ratio @ 8000 rpm.
Can you expand the X scale to show only 360* total ( ie one cycle ) centered on BDC , as this is probably the most critical area of pipe design we need to be looking at.
Plus add the case pressure ratio as well , on the same graph , as this enables optimum tuning of a reed engines intake length.

The "functionality already to show exactly the same graphical data as you have posted" is a stretch, but yes Neels software is a useful tool too, and in the past Neels and I had discussed using both technologies together to create something even better than apart.

Do you know any more details about the TZ350 you posted i.e. power at 8000, and what was peak power rpm, custom exhaust presumably, custom porting ? etc.

I can change the scaling as requested, but as a point of interest seeing what happens on 2 consecutive cycles in one graph also has it's benefits, not always, but when there is something different happening between one cycle and the next, then it is a big plus.

There is no crankcase pressure recorded on this engine as yet, waiting on a sensor. The case ratio is stock. Everything about the engine itself is stock except for the heads, it's all just bolt-ons for the moment, including the heads.

[philou]

I sell my kidneys to have access to this technology?

[nitro2tfx]

I sell my kidneys to have access to this technology?

Are they in good working order .....or........lol.

[wobbly]

Nitro , why do you say the exact same functionality is a stretch ? I can use the sim output data to super accurately predict the performance of every single change to an input element.
Be it a 1mm change in header length , to 1* change in ignition timing.
And to boot it has outputs for every concievable performance indicator , that you would need another 20 sensors to log.
The x axis scaling I mentioned simply due to you commenting that pipe design analysis was a point of interest .
In this regard all we need to see happens between EPO and EPC ie centered on BDC , what the pipe/port pressure ratio is doing when its closed is pretty much irrelevant - thus stretching this scale gives much better insight.

I have microscopic data for the TZ350 LSR engine as it was completely designed in EngMod . Starting with a 250G cylinder and a 58mm Banshee crank the pipe , ignition , squish , compression ,reed thickness ,intake length ,duct areas/mach , everything was optimized with probably a Kg of alloy Tig rod.
And its a testament to Neels code that every single element was built as designed on screen , it went to the salt having only been started from cold , did a few runs to get the Lectrons dialled in -
then smashed the LSR record out of the park.
Have a look on Jeff Henise FB page , all the mods done are there in detail - https://www.facebook.com/jhenise/posts/10155500252306228

[Condyn]

I have said it before and I will say it again. That project inspired the hell out of me. I am unable to view most of the photos because I refuse to be on Facebook, but the basis of my current snowmobile engine masterpiece (in the making) if you will, was derived from the Henise, Wobbly project. My crank is out getting stroked square at the moment, and then the joy of doing aluminum sleeves for the first time. Details and Questions to follow.

[dutchpower]

Neels code has the functionality already to show exactly the same graphical data as you have posted.
Here is the closest I have to a Banshee 350, this is Henise's TZ350 with reed conversion that holds the LSR for non streamliner on petrol at Boneville @ 170.519 mph
showing Exhaust and intake pressure ratio @ 8000 rpm.
Can you expand the X scale to show only 360* total ( ie one cycle ) centered on BDC , as this is probably the most critical area of pipe design we need to be looking at.
Plus add the case pressure ratio as well , on the same graph , as this enables optimum tuning of a reed engines intake length.

Wobb do you have that showing ratio by 12000 rpm

[wobbly]

Yep Dutch , here is the same sim output @ 11,000 ( peak power ) and 12,000 peak rpm.
During the record run it would not change out of 5th gear into 6th , thus was pulling 12,000 thru the timing lights.
So there is still alot left on the table speed wise , and power wise once I get a chance to dyno the thing.
If there is a LSR run in the new year we are shooting for a 200mph medal.

[jfn2]

Hello Wobbly
Sims look very textbook. I have a question about one area. On both the sims at EPO there is a dive in case pressure. If I remember correctly Neels (at one time) mentioned this area should be higher with a pipe change. I don't remember what that change was. If it was higher it would heighten the peak pressure.
Also could you explain more about what a good reed stuffer should look like? I have a picture of a TM reed stuffer and I can not tell the difference from the pics between that one and the bad one just posted. Or am I just in need of more sleep? Thank you. Jeff

[wobbly]

The waveform , at a chosen rpm spread to suit the end use , should have the maximum possible residual pressure ratio at EPO.
This creates superposition of that pressure with that above the piston @ EPO , thus a higher amplitude pressure ratio travels down the diffuser creating a bigger depression around BDC.

The amount of residual pressure ratio is dependant upon the interaction of the port frequency and the Lt of the pipe.
This effect has a naturally bigger amplitude over a wider rpm range when the port duration is down near 190* , but of course this has a huge effect on the blowdown capability.
In the TZ350 I wanted a bias toward peak and overev power , so blowdown was far more important.
The really important elements of the pipes waveform is how deep and wide the negative pressure is around BDC , and the peak return waves position in relation to EPC.

I posted a pic of my best reed stuffer , that has a convex shape down the sides , the bad shape is concave blending to nothing at the tips.
Here is the printed TM stuffer I use again.

[ken seeber]

Now, this looks interesting....

348167

[jfn2]

Wobbly
Thank you for the explanation on the case pressure dip at EPO.
Also for the info on the reed stuffer. I was a little confused there.
I need to make 2 stuffers and want to get started on the right foot.
I would like to ask your thoughts on Boyesen's dual stage reeds for MX bikes? And how they compare to the V-force reeds.

[Vannik]

Some first order results of comparing a Banshee sim with measured traces. Some comments:

1. The sim model is currently a very rough approximation of the real engine and even more so with the pipe, I have no idea what the Toomey T6 looks like.
2. The porting is mostly based on the RZ350 model, until somebody supplies better.
3. I digitized the traces Nitro posted and then used a small amount of smoothing, getting csv files will be better.
4. For some reason I had to shift the inlet trace by 45 degrees to get alignment between the sim and measurement.

[JanBros]

Now, this looks interesting....

348167

Am I the only one who has no clue what this is ?

[wobbly]

Neels , the RZ and Banshee ports are essentially the same bar no PV in the quad engine , but there are two series of RZ with 1mm difference in EPO , no idea which casting Yamaha used
for the quad.
As the pipe dimensions are super critical to the waveforms shape , I dont think we can safely make any coments about how good or not the sims predictive strength actually is,
until we have apples for apples.
And the differing position of the inlet sensors must be responsible for the angular displacement.

JanBros, yep the cylinder is on the dyno , waiting for a printed cover plate to do a twofold test cooling the outside of the transfer ducts , and then adding cooling and a water entry over the outside of the boost port.
I did a dyno run some time ago where all the cold water was directed into the cylinder over the boost port , cooling the transfer tops , then the Axhaust duct , then into the head.
That added 1 Hp , so I am hopefull this test will show the way for future cylinder designs.
Jan picked up 1/2 Hp simply by cooling the inside turn of the transfer ducts , this should add even more.

Edit - the Boyesen reed blocks have very very good stuffer shapes , especially for bent manifolds , but sadly the two stage reeds do very little good in relation to using a VeeForce.

[ief]

From what I can gather, same as first model ypvs except for the exhaust port hight, 29,5 vs 27 mm from top.

52 hp @ 7000 rpm vs 59 @ 8500 according to yamaha.

(edit: ypvs date seems to differ from site to site, think this is the right one)

[jfn2]

Wobbly
As you replied: "the Boyesen reed blocks have very very good stuffer shapes , especially for bent manifolds , but sadly the two stage reeds do very little good in relation to using a VeeForce."
Is this because of the increased tip area with the V-force? The reason I ask this is what if you increased the tip area on the boyesen dual stage reeds by adding a third reed on top of the second reed, or a fourth or even a fifth. I had my first reed setup from Boyesen back in 1970 when he brought out his reed system for the Husqvarna bikes. And he showed me a 3-tier reed and I also saw a 5-tier system in the back of his shop he was working on for a Maico. He didn't comment on them back then but he said he was working with some factory riders with the 3-tier system. I didn't have use of or even have a dyno back then so I cain't say for sure how well it worked but I built a few 3-tier systems and they worked very well for me. I ran them in bikes and snowmobiles. I did have a snowmobile engine dynoed back in 1972 with good results but I changed a few different things at the same time. Since the snowmobile engine was a cvt drive with clutch engagement at about 6500-8500 rpm I don't think the 3-tier reed system helped much. Your thoughts on 3 -4 tier on a v-force reed setup? Also a stuffer in a v-force setup?

[wobbly]

The VeeForce concept is somewhat more complex than just much larger tip area , but for sure its a big contributor.
Its other area of improvment is that due to the increased tip area , for the same flow rate / pressure drop thru the system much less petal lift is needed.
Thus less flow energy is used to achieve the curtain area needed to see the same pressure drop/flow rate across the block.

My take on the basic dual petal Boyesen patented setup is that it looks way more effective than it actually works in practice - but can be alot better than the stock block it replaces.
Sure , in a MX scenario , having very soft petals on top , that open easily with very little pressure delta , you can pick up a bunch of good throttle response off the pipe.
The idea is then that the bigger , thicker petal , also opens at higher airflows to contribute to the upper powerband.
But what i believe happens next is that the soft petal does what soft petals do - go spastic at the first opportunity and badly affects not only the lift profile of the main reed , but also creates
a bunch of turbulence thru the whole system.
This is exactly what happens on the flow bench as you ramp up the feed pressure.
Also its impossible to get a really effective stuffer to work with the much smaller exit area under the top petal , and expect that to work properly when the main petal opens as well.

VeeForce make the same plastic block , and use it in a bunch of differing applications , with just a change in the stuffer/mount plate, to suit whatever shape occurs when the usuall rubber ears are cut off the rubber manifold.
So in many cases you can build a very effective custom stuffer by using one from a different model bike , cut them in 1/2 and using just one side ,put them back to back inside your chosen block.
Does a really good job of making a smaller , central round hole that can then be shaped to suit a setup like 35mm carbs on a Banshee alloy manifold fitted to an LC racebike.
A huge improvment in flow/power over the aftermarket Banshee setup , as well as an even bigger jump for the LC.

[TZ350]

<iframe width="560" height="315" src="https://www.youtube.com/embed/wEA6Oq81uAA" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

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

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

[porttiming124]

Portiming124 - Bonjour mon ami . OK so if you are well versed in removing the chrome , and welding the ports or dividers , then that cylinder could easily be fixed.
If thats the case , then get rid of the A port step , lift the bottom outer corner of the Aux port , and as you say get rid of the second ring and move the top pin over the boost port.
Then epoxy up the duct roofs to get modern axial angles.
Depending upon the end use , it would be much easyer to implement reverse stagger , leave the A port low and lift the B , C port 4* of duration higher , like the Aprilia scavenging pattern.
And please dont put any solder in the cylinder except to check the squish.

I sent my cylinders this week to have the nichasil removed, I will receive them within 10 days.
During this time I am looking at the STA in engmod to find the duration of the transfers.
I see that with the optimized transfer width I can have less duration and even more

[porttiming124]

that reminds me i just did another set the other day. tough little buggers trying not to blow the corner edge off and you only got one shot to get it right. proffesional machinist in oregon united states fucked up my yami cylinders and punched them to 68mm instead of 66 but to make matters worse the left cyl bore vertical centerline didnt intersect the comb chamber center. no choice but to drop in sleeves and start over . the only good news is im back at 64mm

Hello peewee.
I'll have to relocate my pin like you.
Can you explain the prosedure please ?

[philou]

I don't know if it's allowed here.

A download link to an Italian book


https://welovevespa.weebly.com/uploads/1/2/6/5/12655370/ebook_facchinelli_-_elaboriamo_il_2_tempi.pdf

[Muhr]

Hi everyone has spent the Christmas weekend trying to understand what benefits different shapes of bellmouth have at different air speeds. Is it something that someone has investigated and if so, what have you come up with?
Have come so far that I can see an improvement in cfd but feel skeptical that I will see any major improvement in dyno.
Anyway, I'm thinking of reworking a carburetor to get this tested.

[TZ350]

I can see an improvement in cfd but feel skeptical that I will see any major improvement in dyno.
Anyway, I'm thinking of reworking a carburetor to get this tested.

Don't be disappointed if you test a carb with improved CFD and don't see a corresponding increase in output on the dyno.

After my own carb experiments I concluded that the inlet was most likely not the restriction that is holding the engine back. I found most of my improvement by improving the "Transfer" and "Trapping" efficiency of the motor. Rotary valve, big crankcase volume, A ports angled higher than the B ports.

I spent a lot of time playing with improving carburetors as their size was class limited for me. The thinking was that a 24mm carb would restrict a 125cc two stroke to something less than 20 RWHP. On the dyno, after a lot of development I made as much as 32 RWHP with a 24mm carb and single exhaust port.

But I found my air cooled motor could not reject enough waste heat to make 32 RWHP sustainable on the track. 28 RWHP was sustainable and 22 was very reliable. Heat rejection issues probably explains why the factory 125cc air cooled road racers of the day were about 28HP.

[wobbly]

Prof Blairs take on a Bellmouth.
https://www.yumpu.com/en/document/read/4448382/w-melvin-cahoon-prof-blair-associates

[porttiming124]

I sent my cylinders this week to have the nichasil removed, I will receive them within 10 days.
During this time I am looking at the STA in engmod to find the duration of the transfers.
I see that with the optimized transfer width I can have less duration and even more



here are the STAs with the wider and lower transfer.
I worked on the height of the transfer to match the achievable power of the BLW (which I do not touch)
It seems to me to make sense but what do you think of low duration like that?

[nitro2tfx]

Nitro , why do you say the exact same functionality is a stretch ? I can use the sim output data to super accurately predict the performance of every single change to an input element.
Be it a 1mm change in header length , to 1* change in ignition timing.
And to boot it has outputs for every concievable performance indicator , that you would need another 20 sensors to log.
The x axis scaling I mentioned simply due to you commenting that pipe design analysis was a point of interest .
In this regard all we need to see happens between EPO and EPC ie centered on BDC , what the pipe/port pressure ratio is doing when its closed is pretty much irrelevant - thus stretching this scale gives much better insight.

I have microscopic data for the TZ350 LSR engine as it was completely designed in EngMod . Starting with a 250G cylinder and a 58mm Banshee crank the pipe , ignition , squish , compression ,reed thickness ,intake length ,duct areas/mach , everything was optimized with probably a Kg of alloy Tig rod.
And its a testament to Neels code that every single element was built as designed on screen , it went to the salt having only been started from cold , did a few runs to get the Lectrons dialled in -
then smashed the LSR record out of the park.
Have a look on Jeff Henise FB page , all the mods done are there in detail - https://www.facebook.com/jhenise/posts/10155500252306228

Where to start. There are lots of performance predicting simulation software programs, some 2 stroke, some 4 stroke, likely some rotary ones exist as well. Most of them predict performance of a build and/or guide the build fairly well, some better than others. I think everyone knows that, or should.

There are some big differences between predicting performance/guiding a build with simulation software versus actually measuring pressure waves.

1) Measuring pressure waves allows you to actually see the pressure waves as they are (within sensor positioning limits). Simulation software does not have to get the waves exactly right to make people happy, it just needs to get the performance prediction close to make people happy. Measured pressure waves and combustion pressures show what happened, even for transient events that only happened on one cycle or a handful of cycles. Lots of interesting things to see cycle to cycle.

2) Measuring pressure waves (and combustion pressures) allows you to do things inside the box, a little outside the box, and also WAY WAY outside of the box, no limitations. Since it is recorded data you know just what happened inside the engine, for every single cycle for the whole test whether on a dyno, or at the track. No ifs, ands, or buts about it, every cycle, not averaging of events. What happened in the engine, as recorded, is what happened in the engine, it is not dependent on software limitations, nor wishful thinking, nor what SHOULD have happened in the engine, it is a factual recording of what actually happened. Lots to be learned when you see everything that happened, not just an average.

3) Ignoring what happens with the pressure waves when the exhaust port is shut is a mistake. True when one uses simulation software it doesn't matter because there is nothing you can do about it, the output is the output and depends on the input. However, when the person behind the keyboard is doing the thinking, instead of the software, that changes the picture entirely, what happens with the port shut is valuable info, that's why we display it in our graphs.

4) Lots of fast vehicles have been built without using either measured pressures or simulation software pressures, the two technologies are bonuses for sure, both separately and together, but they are not the only way to skin a cat. Just depends on who is doing the cat skinning lol. To be honest something fast designed without pressure measuring equipment or simulation software is a more impressive feat.

5) The companies that make pressure sensors have been around for several decades, it is a multi millionaire dollar industry and continues to grow. Pressure sensors are NOT inexpensive, if simulation software was functionally exactly the same, no one would be manufacturing the pressure sensors nor buying them.

6) When one relies SOLELY on simulation software, one is automatically locking themselves in to being "no better than the rest". Anyone using the same simulation software can build something equally as good. This is not true of using recorded pressures, recorded pressures pits one person against the next, ingenuity vs ingenuity, the end products will not be the same. Simulation software gives a person a leg up on those that don't have it, or aren't adept at using it, but simulation software in conjunction with pressure recording equipment gives a person two legs up.


I'm not trashing Neels software in any way, it is very good software, but it is not correct to think that simulation software is the exact same thing as recorded pressures, it isn't. There are benefits to simulation software and there are benefits to recorded pressures, that's why having both together is the cat's meow.

[Vannik]

Where to start. There are lots of performance predicting simulation software programs, some 2 stroke, some 4 stroke, likely some rotary ones exist as well. Most of them predict performance of a build and/or guide the build fairly well, some better than others. I think everyone knows that, or should.

There are some big differences between predicting performance/guiding a build with simulation software versus actually measuring pressure waves.

3) Ignoring what happens with the pressure waves when the exhaust port is shut is a mistake. True when one uses simulation software it doesn't matter because there is nothing you can do about it, the output is the output and depends on the input. However, when the person behind the keyboard is doing the thinking, instead of the software, that changes the picture entirely, what happens with the port shut is valuable info, that's why we display it in our graphs.

Nitro, very good response as per usual.

Ignoring the effect of the closed cycle is not something the sims do though. Attached a pdf I distribute with my software.

348178

[andreas]

I haven't been on here in a long time, what's the trick to getting a jpg to show directly in a post (not as an attached thumbnail).

I have the jpgs loaded on Dropbox but adding the Dropbox links to the post doesn't seem to do anything according to the preview.

Thanks.

Anyway the thumbnails show high speed RECORDED pressure data (cylinder, intake, exhaust) that I promised ages and ages ago. I planned to have crankcase pressure too but will have to do that another time. Yamaha Banshee with some mods, details to follow.

I don't understand, how can the returning wave be 70% larger than than the outgoing?

[nitro2tfx]

I don't understand, how can the returning wave be 70% larger than than the outgoing?

There are more waves in that pipe (or any pipe) than just the blowdown wave and the returning negative and positive waves. Always. Waves add up and the result at any point in time (or angle) is the summation of the waves, some generated from the current cycle, some generated from the previous cycle.

The pressure waves in a particular pipe for any particular cycle are dependent on the pipe/porting of course, they are also dependent on the combustion process in the cylinder for that cycle, ..........AND the pressure waves that are still ringing back and forth from the previous cycle (or cycles). That's why it is important to know what happened in the previous cycle as well as the cycle of interest.

Another thing that most people don't realize is that in a spark ignition engine the combustion process varies quite a bit from one cycle to the next, so the driving force for the pipe varies from cycle to cycle. A modern diesel engine is a different story, the combustion cycle is just about the same cycle after cycle after cycle, for a given rpm/load, but in a spark ignition engine it is not like that, every cycle is different from the one before it and after it.

[nitro2tfx]

Some first order results of comparing a Banshee sim with measured traces. Some comments:

1. The sim model is currently a very rough approximation of the real engine and even more so with the pipe, I have no idea what the Toomey T6 looks like.
2. The porting is mostly based on the RZ350 model, until somebody supplies better.
3. I digitized the traces Nitro posted and then used a small amount of smoothing, getting csv files will be better.
4. For some reason I had to shift the inlet trace by 45 degrees to get alignment between the sim and measurement.


When I have a chance I will see if the T6 pipe dimensions happen to exist somewhere online.

As for the intake, where was the "sensor" placed in the simulation software ? Was any sort of bellmouth etc. used on the carb in the software ?

[TZ350]

IAnyway the thumbnails show high speed RECORDED pressure data (cylinder, intake, exhaust) that I promised ages and ages ago.

I planned to have crankcase pressure too but will have to do that another time. Yamaha Banshee with some mods, details to follow.

I would be very interested in the crankcase pressure data.
.

[Muhr]

Don't be disappointed if you test a carb with improved CFD and don't see a corresponding increase in output on the dyno.

After my own carb experiments I concluded that the inlet was most likely not the restriction that is holding the engine back. I found most of my improvement by improving the "Transfer" and "Trapping" efficiency of the motor. Rotary valve, big crankcase volume, A ports angled higher than the B ports.

I spent a lot of time playing with improving carburetors as their size was class limited for me. The thinking was that a 24mm carb would restrict a 125cc two stroke to something less than 20 RWHP. On the dyno, after a lot of development I made as much as 32 RWHP with a 24mm carb and single exhaust port.

But I found my air cooled motor could not reject enough waste heat to make 32 RWHP sustainable on the track. 28 RWHP was sustainable and 22 was very reliable. Heat rejection issues probably explains why the factory 125cc air cooled road racers of the day were about 28HP.


Nice work. It is not easy to get that type of power out of an air-cooled engine with single exhaust

I hope I have ok setup in terms of transfer, exhaust, crankcase volume etc. Where I see as the biggest challenge for me is to get enough time area for the intake as I want to get peak hp closer to 22m / s which I think will be very difficult.
In a previous project that I helped a friend with, that was the biggest challenge. It was a 50cc cvt (Rotary valve)that we took out max at 15500.
Miserable to start and stuck below 3000, if you happened to drop it below 8000.



Prof Blairs take on a Bellmouth.
https://www.yumpu.com/en/document/read/4448382/w-melvin-cahoon-prof-blair-associates

That was the article that made me start thinking about it. I was looking for something completely different when I stumbled across it. then it was a simulation that eventually became many.

[wobbly]

Nitro , plenty to agree with in your reply , but plenty to passionately disagree with as well.

You are making a huge assumption ( often just an error waiting to be revealed ) that everyone using a good sim is " happy " simply inputing data , then looking solely at the result in an output power graph.
That couldnt be further from the truth - the on screen wave form , as interpreted by the user " thinking " as you put it , reveals exactly what needs to be done next.
In this respect its just as powerfull as your interpretation of the real time wave forms using intellect/experience , but just using a different source of data.

You say ignoring the trace info outside of EPO - EPC is a mistake and anyway " nothing can be done about it " - so what can you " do about it " using the live data , nothing as well - except interpret the results.
If the pipe is well designed the result will always be 1 - as much superposition at EPO as possible , 2 - as deep/wide as possible depression around BDC , 3 - the highest peak return wave just before EPC.
Sure , we can interpret what is happening with legacy cycle waves combining or destructive interference , but what happens when the port is closed , ends up only affecting one thing , the relative strength of the
remnant pressure at EPO - nothing else.
It can go above and below a pressure ratio of 1 several times when the port is closed , but the only thing that actually matters is the end game, the strength of superposition.

Sure I agree lots of fast engines have been designed without any data , be it from a sim or live.
Perfect example though would be the last homologated TM kart engine. The pipe design for that took 4 people 4 months full time to build 25 pipes, dyno test the result and then try to decide what did or didnt work.
I did over 100 sims , built 3 test pipes , dyno and track tested them , plus produced a new CAD file of a way superior Exhaust duct , all in 3 months , alone.
The result was a huge advance in power - in exactly the places asked for , on the dyno and on the track.

Absolutely impossible to achieve , without using a good code that deleted the need to build and verify a huge number of multiple design theories.
My opinion now is that there is very little " cleverness " in doing that task without data , just a huge wasted amount of expense and time , with no way of guaranteeing that there was not alot " left on the table "
apart from a pile of useless pipes.

But the end game here is , if your results from comparing an apples for apples sim against live data ends up improving Neels code , in any way ,shape ,or form , im really glad for your help.
Just dont presume all we are doing is being " happy " by looking at the very last part of the equation for build sucess = a power graph.

[Muhr]

Anyway, I'm thinking of reworking a carburetor to get this tested.
Had some time to spare today so now it's done.

[philou]

Muhr, Maybe this could inspire you

https://www.motomeccanicaracing.it/2015/02/07/kit-phbg-21/

[OopsClunkThud]

Here's the "master template" that I made from info in the Blair paper as well as the curtain length that wobbly published. I may (or may not) have got it completely wrong.

link to parametric Fusion360 sketch.

I make a copy and size it to fit any given application.

348180
https://a360.co/3pmDAZY

[SwePatrick]

Hi everyone has spent the Christmas weekend trying to understand what benefits different shapes of bellmouth have at different air speeds. Is it something that someone has investigated and if so, what have you come up with?
Have come so far that I can see an improvement in cfd but feel skeptical that I will see any major improvement in dyno.
Anyway, I'm thinking of reworking a carburetor to get this tested.

This design below has worked best for me:
On a mikuni vm42 taperbored from 43.5 to 48mm then radius tangent to the velocitystack.

348181

[F5 Dave]

Muhr, Maybe this could inspire you

https://www.motomeccanicaracing.it/2015/02/07/kit-phbg-21/
Inspires me to cut a Dellorto in 1/2

[JanBros]

Wob, have you experiented with "your exhaust duct" and it's influence on where in the rev-range it benefit's ?

need to make new exhausts for my KR1 as I'm building one with an RGV swing arm and because of it's wider knuckle in the rear suspension, the (very good) original pipes no longer fit.
I do not want any more HP because the cylinders can not handle al lot more than standard, they crack at the rear mounting holes because the base is to thin.

So I'm wondering if you have advise on a duct that benefit's power lower down the rev-range ?

[wobbly]

JanBros , the duct rule of thumb naturally exhibits the trend of pumping up peak , and more so overev power.
This is soley due to the increased Mach in the duct ie approaching 0.8M if done correctly.
But due to this phenomenon it is then possible to redesign the pipe , such that it counters the trend of the duct by increasing considerably the mid and off pipe power.
Add the two together , and the result is a ton of midrange power , with no loss or gain in peak and overev than you had previously.

[Muhr]

I may (or may not) have got it completely wrong.


348180
https://a360.co/3pmDAZY

I think you seem to have got it pretty right!

[dutchpower]

Big diff. in rpm

[SwePatrick]

I think you seem to have got it pretty right!

That huge radius on the bell would work better in a 4stroke setup.
Look at old gp bikes carburetors instead and simulate their setup.
As stated before, you might not look at max flow,,,,

https://www.apriliaforum.com/forums/attachment.php?attachmentid=23345&stc=1&d=1108261594

[Frits Overmars]

That huge radius on the bell would work better in a 4stroke setup.
Look at old gp bikes carburetors instead and simulate their setup.
https://www.apriliaforum.com/forums/attachment.php?attachmentid=23345&stc=1&d=1108261594Here is that very same carburettor, fitted on an Aprilia RSW125, with its big black bellmouth. So looking at old gp bikes carburetors is indeed a good idea https://www.kiwibiker.co.nz/forums/images/smilies/msn-wink.gif.
348191 348190

[Muhr]

That huge radius on the bell would work better in a 4stroke setup.
Look at old gp bikes carburetors instead and simulate their setup.
As stated before, you might not look at max flow,,,,

https://www.apriliaforum.com/forums/attachment.php?attachmentid=23345&stc=1&d=1108261594

Hi Patrik I have simply made it so big that size is no longer a factor. It is my intention to use this for testing extremes in both directions. The easiest thing would have been to put on a larger carburetor. My hopes for something spectacular with this are low, what do you say knowledge is power. Have not gotten as far as you so I know what works for what and what flow speeds suit what.

[SwePatrick]

Hi Patrik I have simply made it so big that size is no longer a factor. It is my intention to use this for testing extremes in both directions. The easiest thing would have been to put on a larger carburetor. My hopes for something spectacular with this are low, what do you say knowledge is power. Have not gotten as far as you so I know what works for what and what flow speeds suit what.

I´d say with a huge radius the length of carb is becoming way to long.
I'm not 100% sure about this but a carb can almost never be to short in a highrevving engine, and by that one would never want to make it longer ;)

And that´s what i´ve noticed in my dyno also, every time i made inlet length shorter it was a gain.

[nitro2tfx]

Nitro , plenty to agree with in your reply , but plenty to passionately disagree with as well.

You are making a huge assumption ( often just an error waiting to be revealed ) that everyone using a good sim is " happy " simply inputing data , then looking solely at the result in an output power graph.
That couldnt be further from the truth - the on screen wave form , as interpreted by the user " thinking " as you put it , reveals exactly what needs to be done next.
In this respect its just as powerfull as your interpretation of the real time wave forms using intellect/experience , but just using a different source of data.

I agree that simply looking at power output predictions may not be enough to make you happy, but it no doubt makes a lot of people happy. The people like yourself that are doing a lot of thinking about traces, and so on, are ASSUMING that in addition to the power predictions the simulated exhaust traces and intake/crankcase traces are right. The fact that power predictions are close to the real world in no way means that the exhaust traces are just as close, not at all. Obviously they are not horribly wrong, but by the same token they are not fantastically right and some details are lost. That is where some things are left on the table, currently.




You say ignoring the trace info outside of EPO - EPC is a mistake and anyway " nothing can be done about it " - so what can you " do about it " using the live data , nothing as well - except interpret the results.

I was saying that ignoring EPC-EPO is a mistake, makes no difference whether we are talking about simulation data or recorded data. That's why we plot it and the previous cycle. Neels indicated that the simulation software does not ignore EPC-EPO irregardless of whether the end user does or not. It does matter (see below).




If the pipe is well designed the result will always be 1 - as much superposition at EPO as possible , 2 - as deep/wide as possible depression around BDC , 3 - the highest peak return wave just before EPC.
Sure , we can interpret what is happening with legacy cycle waves combining or destructive interference , but what happens when the port is closed , ends up only affecting one thing , the relative strength of the
remnant pressure at EPO - nothing else.
It can go above and below a pressure ratio of 1 several times when the port is closed , but the only thing that actually matters is the end game, the strength of superposition.



"1 - as much superposition at EPO as possible" . Yes but the superposition needs to be close but not quite aligned and shape matters.
"2 - as deep/wide as possible depression around BDC" . Coarsely but shape of the depression matters somewhat too.
"3 - the highest peak return wave just before EPC" . Shape matters a lot and a higher peak with the wrong shape will not make more uumph.

4 - what happens EPC-EPO affects more than just the remnant pressure at EPO it affects the shape of the superposition pressure in the vicinity of EPO AND what happens during the depression around BDC

5 - traces with numerous unwanted oscillations, are well....unwanted, these unwanted oscillations can be due to the pipe design or due to minor fabrication imperfections, it doesn't take much, this can also be seen and eliminated using recorded data. Everybody has had a pipe that should have worked fine but didn't quite live up to expectations, sometimes this is nothing more than due to not so obvious minor details that set up additional oscillations. The recorded data shows if you have what you think you have, or you don't.

Wave shape, angular location and magnitude, all 3 matter.

[wobbly]

Dutch - from your plots I can see that at 21,000 the tuned length is spot on and in resonance with the port frequency.
You have exellent superposition that produced a huge amplitude wave down the diffuser , and a good return , correctly timed pulse just before EPC.
But the diffuser shape ( % Lt starting and or angles ) is all wrong - in that at lower rpm its doing almost nothing around BDC , and at the correct rpm for resonance , the max depression is far too late in the cycle.
This lateness of depression peak then , above resonance rpm , is even further off the scale to the right.

[Muhr]

I´d say with a huge radius the length of carb is becoming way to long.
I'm not 100% sure about this but a carb can almost never be to short in a highrevving engine, and by that one would never want to make it longer ;)

And that´s what i´ve noticed in my dyno also, every time i made inlet length shorter it was a gain.

I understand that you have thought through the physics behind that.
With the BMEP numbers you present, I understood that you had solved it..... Luckily I have a few more variants to test.
Actually stood tonight and thought about how I could shorten the intake I understand that I have a bit left until I reach an acceptable level.
How do you usually do?

[ken seeber]

To me it is clear that predictive software and/or taking real time measurements are just some of the tools to assist in the design of one important functional component of the final product, in this case a high performance 2 stroke engine.

The real test is ultimately to use these tools in addition to skills, knowledge, imagination, experience, instinct and dedication to come up with an improved product each time.

[TZ350]

I'm not 100% sure about this but a carb can almost never be to short in a highrevving engine, and by that one would never want to make it longer ;) And that´s what i´ve noticed in my dyno also, every time i made inlet length shorter it was a gain.

We went to an extreme with a short carb/inlet tract.

348195348196


Pic-04 the new 33mm bellmouth feeding directly to the motor.

348194

The idea worked Ok and made very good power but with the short inlet tract there was a severe resonance dip just before it came on the pipe. So severe that it would spit fuel past the front axle.

348197

Increasing the length of the inlet tract greatly reduced the resonance dip.

It ran Ok.

<iframe width="560" height="315" src="https://www.youtube.com/embed/YxiEo8cgopg" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>


<iframe width="560" height="315" src="https://www.youtube.com/embed/p4ef-WUO1Qs" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>


If I could have solved the problem of fuel/oil dropout in the plenum I would use this idea. As it made very good low end power out of the corners and still had very good top end as well. On track tests it was a two stroke that drove like a bigger four stroke.

The plenum resonance seemed to plump up the bottom end remarkably. And if we could have automatically altered the plenum resonance (volume) I am sure we could have greatly improved the engine performance everywhere.

[wobbly]

The other consideration with inlet length is that the reflected wave off atmosphere is a gradual reversal of that waves sign.
End correction for the wave not reflecting off a hard medium takes care of this effect in a sim , but my take on large bells is that making them longer and much larger in diameter
may not in reality change the true reflection point , but it just moves the bell further into the reflection zone , improving the energy recovery of the area change.

[SwePatrick]

I understand that you have thought through the physics behind that.
With the BMEP numbers you present, I understood that you had solved it..... Luckily I have a few more variants to test.
Actually stood tonight and thought about how I could shorten the intake I understand that I have a bit left until I reach an acceptable level.
How do you usually do?

No calculations here ;)
A lot of dynopulls tells the reality.

I often shorten the rear of the carb and make an intakeplate like modern cartengines have.
The carb protrudes into a plate bolted on the reed.

348205

And below a cart engine, look at the carb, not a big radius in the bell, a taper into the throttle blade that begins with a small radius and a 'plane' that connects outward against where you mount the airfilter.

348204


Ignore picture below,, something got messed up when uploading

[wobbly]

The KZ Dellorto kart carb is nothing special at all , its just what was homologated many years ago and no mods are allowed.
But one airbox manufacturer was clever and achieved what im sure all good tuners would have eventually come up with.
They made the rubber clamp on manifold effectively a continuation of the bell , with minimal extra length.
This is worth several Hp past peak over others that simply have an extension to the flat clamp surface.

[SwePatrick]

It was just an example.

A fullradius velocity stack seldom gives max power is what i try to say.

Always this black and whiteness........
never nobody tries to understand.
One always need to write a novel to leave out all misunderstandings.

[wobbly]

What I was saying was that the full radius " velocity stack " , in a simple back to back dyno test , gave a big increase over a shorter , smaller diameter bellmouth.
In this case , with a very short intake length already , a big increase in top end power was the result , although a small amount of length had been added.
So the added pressure recovery created by the extended bell , overcame any percieved downside of increased length.
Black is less power - white is more , the dyno does not lie or guess - as we do most of the time.

[Muhr]

The KZ Dellorto kart carb is nothing special at all , its just what was homologated many years ago and no mods are allowed.
But one airbox manufacturer was clever and achieved what im sure all good tuners would have eventually come up with.
They made the rubber clamp on manifold effectively a continuation of the bell , with minimal extra length.
This is worth several Hp past peak over others that simply have an extension to the flat clamp surface.

Here is a sim of 0mm radius 8mm and one ellipse.



It was just an example.
A fullradius velocity stack seldom gives max power is what i try to say.

Always this black and whiteness........
never nobody tries to understand.
One always need to write a novel to leave out all misunderstandings.

It's just a little confusing, if you look at the picture I posted last time. Then you can see on the left a couple of rubbers from 2 engine manufacturers on the intake you refer to, if you then look in the middle of the same picture, there are 2 carburetors that are identical to what you are referring to.
Here is also a link to the air box Wob refers to:
https://www.tkart.it/en/magazine/tech-focus/active-filter-an-innovation-by-righetti-ridolfi/

[TZ350]

.

My bike having disgraced itself on the dyno by locking up at full song in top gear was put in the naughty corner to think about its behavior.

It is quite something to have the back wheel stop and the dyno drum still spinning at 100mph.

348216

Pulled the engine out today to see what went wrong.

I had all ways been a bit nervous about the old RD400 rod letting go at 14,000 rpm.

348215

But the mystery depend when I found no real engine damage but a lot of black fine soft almost rubbery stuff coating the cylinder head and crankcase walls. It was everywhere.

348214

The culprit was reveled. The rotary valve blade had broken and rubbed its way through the rotary valve covers outer "O" ring and eventually jammed the engine.

For such a dramatic moment on the dyno there is not much damage thankfully.

[porttiming124]

Happy New Year everyone

[wobbly]

Portiming - same to you .Your question about the numbers on the STA sheet.
Those look just fine , the devil is in the detail .
Post your .pack and we can tell you what isnt going to work - if anything.

[ken seeber]

The recent talk on short carbs coincided with me fossicking around and finding this short carby I made around 50 years ago. Obviously a slide unit, but the fuel metering was done using the same principle as the Wal Phillips carb. I fitted it to my first ever raced bike, a Suzuki A100. It sort of worked, running on methanol, but no magical power boost. Was a pig in many areas and, when running, had a standing fog outside of the carb that left everything smothered in fuel. Trying to get the thing running at night in neighbouring suburban streets was a touch anti-social….they thought. Sold the bike shortly after. Bloody 2 strokes.

348245348246348247348248348249348250

[nitro2tfx]

To me it is clear that predictive software and/or taking real time measurements are just some of the tools to assist in the design of one important functional component of the final product, in this case a high performance 2 stroke engine.

The real test is ultimately to use these tools in addition to skills, knowledge, imagination, experience, instinct and dedication to come up with an improved product each time.

Both real time pressure analyzers products and simulation software products are very good and useful tools, but like anything else a lot depends on the end user too. Typically both technologies save a good deal of time and money in the long run, as well as improve performance, some people really run with the ball and some don't, but the opportunity is there.

[nitro2tfx]

One thing I have not noticed in this thread, nor anywhere else, is a discussion of how positive pressure return waves are generated in ways other than just a positive pressure reflection off of a converging cone or flat end surface, in a typical 2 stroke pipe. Has this been discussed at all ?

[TZ350]

One thing I have not noticed in this thread, nor anywhere else, is a discussion of how positive pressure return waves are generated in ways other than just a positive pressure reflection off of a converging cone or flat end surface, in a typical 2 stroke pipe. Has this been discussed at all ?

No. But start it off and tell me more about these magic waves energy source.

[Vannik]

One thing I have not noticed in this thread, nor anywhere else, is a discussion of how positive pressure return waves are generated in ways other than just a positive pressure reflection off of a converging cone or flat end surface, in a typical 2 stroke pipe. Has this been discussed at all ?

1. From a wave going through a contact discontinuity - where the composition and or temperature changes
2. Reflection from a shock wave forming
3. A suction wave traveling down a diffuser will reflect a positive wave back
4. ?

[nitro2tfx]

1. From a wave going through a contact discontinuity - where the composition and or temperature changes
2. Reflection from a shock wave forming
3. A suction wave traveling down a diffuser will reflect a positive wave back
4. ?

Since it seems like 1,2,3 and possibly 4 have not been discussed much, or at all, maybe it would be useful to explain 1,2,3 in some detail to ALL. Then from that I can see if your 1,2,3 includes my "4" or not.

As a side note I think we are going to have to measure the T6 Banshee pipe as there don't seem to be any dimensions for it on the internet. Hoping to get another few tests in before taking anything apart so there will be a bit of a delay in getting those numbers to you.

[wobbly]

Nitro , as I am really keen on using any tool I can in the quest for increased speed of analysis in producing new or better designs , can you explain one thing to me
about the way you implement the data analysis of the real time observations.
To me the process is only one step ahead of the old " suck it and see " approach.
As it seems you have to do a test run , analyse the data , then the only way forward is to modify or rebuild the pipe/ports etc , then do another test - still slow and laboreous , but more informed obviously.

Again I come back to the last big project I did for TM.
They wanted more front side power , so it took me about a week of constant small iterations in the sim, and analysis , to discover categorically that the last part of the diffuser , had the biggest effect on this.
I started out with a short , shallow section , just like an Aprillia pipe , and 30 sims later ,ended up with a cone way longer , and steeper , than I could ever have imagined.
Then to supress the tendency to produce more peak ( not wanted , as it creates too much tuning drama trying to supress deto ) this needed a completely differing approach ( from " normal " )
to the header and 1st diffuser % / length.

I built one pipe to dyno prove the diffuser concept , one to prove the header , and one to prove the rear cone matched the sim effects.

Is the real time data analysis able to match or short circuit this process without spending hours rebuilding pipe after pipe iterations - just to see if a theory matched reality.

[41juergen]

I'm in the need for the KTM SX250 cylinder data for EngMod (ExPort and Transfers) as I don't have the cylinder yet in my hands. Can anyone help me with that? If one would have the whole EngMod project file for the SX250 would be also very appriciated... :not:
cheers
Juergen

Got it, thank you so much Neels!!!!

[136kg136ps]

What say ye? Snake oil or engineering breakthrough?
I was immediately skeptical when it mentioned the high octane requirement and need for high pressure oil in the transmission but always willing to listen.

https://www.sticsupertorque.com/productinfo.html

[lodgernz]

What say ye? Snake oil or engineering breakthrough?
I was immediately skeptical when it mentioned the high octane requirement and need for high pressure oil in the transmission but always willing to listen.

https://www.sticsupertorque.com/productinfo.html

Historic discussion starts at post 31977 here: https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131133232#post1131133232

[Vannik]

Since it seems like 1,2,3 and possibly 4 have not been discussed much, or at all, maybe it would be useful to explain 1,2,3 in some detail to ALL. Then from that I can see if your 1,2,3 includes my "4" or not.

Nitro, will do but it will take a few days. I have to put in words what is normally in differential equations in a way that is both still correct and understandable. But it is a good idea to do this.

[Vortex]

Hello folks,
I have been a passive reader here for a long time now and I would like to confess that there is a lot of 2-stroke expertise to be found here, really interesting and great.
I have been working in karting for many years, mainly in the OK engine sector (direct drive). I also own an engine test bench (dynamic, static and dynamic/static combined measurements possible).
We are very limited by the regulations in those classes.
The power density has become extremely tight, many drivers are only separated by 1/10 of a second or less per lap.
I dare to ask a question about the exhaust. The exhaust is homologated for 3 years and is the same for every manufacturer, so the engine or rather the requirements for the engine should be made to match the exhaust as much as possible. So I can only use given tolerances here.
Is there a nice person here who would be willing to maybe make me different simulations by exploiting the given tolerances to then be able to see the different tendencies, it is not enough for me to just drive the whole exhaust long or short, this result is known to me.
The simulations don't have to be for free either.
I bought the EngMod2T software a few years ago, but unfortunately I don't know how to use it.
If there should be this nice person here then please let me know. Of course I would be very happy to provide all the technical details.
Thank you in advance.

[136kg136ps]

Historic discussion starts at post 31977 here: https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131133232#post1131133232

Thanks for that, missed a lot around that time with all the Luc banter.

[wobbly]

Mr Vortex - PM sent re sims in EngMod.

[nitro2tfx]

Nitro , as I am really keen on using any tool I can in the quest for increased speed of analysis in producing new or better designs , can you explain one thing to me
about the way you implement the data analysis of the real time observations.
To me the process is only one step ahead of the old " suck it and see " approach.
As it seems you have to do a test run , analyse the data , then the only way forward is to modify or rebuild the pipe/ports etc , then do another test - still slow and laboreous , but more informed obviously.

Again I come back to the last big project I did for TM.
They wanted more front side power , so it took me about a week of constant small iterations in the sim, and analysis , to discover categorically that the last part of the diffuser , had the biggest effect on this.
I started out with a short , shallow section , just like an Aprillia pipe , and 30 sims later ,ended up with a cone way longer , and steeper , than I could ever have imagined.
Then to supress the tendency to produce more peak ( not wanted , as it creates too much tuning drama trying to supress deto ) this needed a completely differing approach ( from " normal " )
to the header and 1st diffuser % / length.

I built one pipe to dyno prove the diffuser concept , one to prove the header , and one to prove the rear cone matched the sim effects.

Is the real time data analysis able to match or short circuit this process without spending hours rebuilding pipe after pipe iterations - just to see if a theory matched reality.

A long winded question deserves a long winded answer lol.

Basically the short answer is "it depends".

Simulation software and real time pressure measurement are not exactly competing products, they are overlapping/complimentary products. Simulation software does some things quicker and cheaper than real time pressure measurement. Real time pressure measurement does some things better than simulation software.

In the 4 stroke world real time cylinder pressure tuning is king, the intake and exhaust are important but not as much. In the 2 stroke world cylinder pressure tuning generally takes a back seat to porting and exhaust tuning, even though one could modify a 2 stroke combustion chamber any number of ways that could never be done with a 4 stroke. When it comes to cylinder pressure tuning, there is no comparison between simulation software and real time pressure measurement, none, real time pressure measurement is much, much better at it.

When it comes to 4 stroke exhausts, real time pressure measurement is more capable than simulation software.

However, 2 stroke exhausts are a different story, construction is time consuming. What one is trying to do determines which (simulation soft or real time pressure measurement) is more appropriate, though in many cases the appropriate thing to do is use both technologies.

If for example you have something that works pretty well, and your goal is to make it better then carry on with life, perhaps rinse and repeat, then simulation software will be the quickest and cheapest method. Probably no wife approved reason to purchase real time pressure measurement in this case lol.

On the otherhand if you have:

1) something that is fully developed with simulation software and you want to take it further than that or
2) your competition is using the same simulation software as you are i.e. they can duplicate your results or
3) you are trying something radically different with the engine or exhaust system which isn't modeled well or at all in simulation software or
4) you want to verify what the actual pressures are to make sure the simulation software is inline with reality or
5) you are trying to redesign the combustion chamber or evaluate the combustion process in any way (fuels, additives, ignition, chamber shape, chamber material etc.) or
6) you are trying to do something significantly different on the intake side of things or
7) you are testing/tuning/developing an engine that makes a LOT of power or where detonation or pre-ignition is a worrisome issue, real time pressure measurement will keep you from blowing it up during the process

In cases 1 through 7 you would want to use real time pressure measurement, simulation software should be used too for the relevant aspects.

As a rule of thumb simulation software is the quickest way to get from A to B. Real time pressure measurement is the best way to get from B to C and often the only way to know C even exists. No matter what you build, how you build it and whether you pegged the imagination/ingenuity meter doing it, real time pressure measurement will handle it. The 2 technologies are overlapping and complimentary.

The next time I post I will post a screenshot of the pressure waves from a unique pipe we have used on 4 strokes. Yes I know nobody wants to hear about 4 strokes lol, but 2 stroke//4 stroke is not the point, the point of showing it is to show that a 2 stroke like exhaust pressure trace can be generated without using a 2 stroke type exhaust pipe and it can even be generated on a 4 stroke engine.

[TZ350]

The next time I post I will post a screenshot of the pressure waves from a unique pipe we have used on 4 strokes.

I am always interested in real time/world measurement. Please give us more info on the hardware used.

[Vannik]

Nice discussion Wobbly and Nitro!

As promised, a first attempt at explaining some gasdynamic reflections without using differential equations. Please comment, ask questions etc so I can improve it.

348284

[Condyn]

Excellent info Neels. Thank you. I hope I am not jumping the gun on commenting because there is a lot to take in with that. I would like to know what effect, if any, intersecting waves have on one another. If a closed pipe baffle wave has a slightly reduced amplitude, how is it strong enough to push the spilled, untrapped, cold slug back into the cylinder? I know you have provided some pipe development examples with your software, I am interested in more info like that if you or anyone else reading this would be interested in sharing that kind of thing. Cause and effect of what to change and why while developing a pipe. The paper you just released certainly helps paint a picture for us of what is going on. ( Also slight typo on Number 2 I believe ) Thank you again.

[Frits Overmars]

Nice discussion Wobbly and Nitro! As promised, a first attempt at explaining some gasdynamic reflections without using differential equations. Please comment, ask questions etc so I can improve it.I love it Neels! It also makes me feel young again; it takes me back 44 years, to 1977, when I made an attempt to do what you are doing right now: to put in words what is normally in differential equations in a way that is both still correct and understandable.
At the time I was technical editor of the motorcycle magazine Moto 73 and I wanted to do something a bit more satisfying than just explaining combustion engine basics for the umpteenth time. The chief editor warned me that most readers would not appreciate an in-dept treatise in a popular magazine but I was as stubborn then as I am now, so I carried on. Over the years that treatise became the most-sought-after story ever from Moto 73.
Below is a picture from it, trying to explain how a diffuser functions, and a PDF containing the complete story. It was written in Dutch (although I keep adding that all drawings are in English) but I know you won't have any difficulty reading it.
348285348287

[teriks]

As promised, a first attempt at explaining some gasdynamic reflections without using differential equations. Please comment, ask questions etc so I can improve it.

Great write up, impressive to condense all that into just a couple of pages.

[Vannik]

Condyn,

Thanks for spotting that, I will fix it in issue 2

The more difficult part to explain is that there is both energy and inertia involved and sometimes amplitude is converted into inertia and sometimes the other way. The differential equations are: 1. conservation of mass, 2. conservation of energy and 3. conservation of momentum. All three must be satisfied at all times. So sometimes you can fool yourself if you just look at pressure amplitude as it is not the full picture. I do not know how to elegantly explain that.

Frits,

I can read that just fine thank you. Seems I follow you by about ten years, in the early 80's I was technical editor for a local magazine, Bike & Track and tried to do similar. I still have a handwritten copy of an article I wrote on blowdown specific time area!

Anyway, let us see what Nitro comments.

[wobbly]

Condyn - Neels has given you a clue to the answer about how the overscavenged gas slug sitting in the duct is reversed back into the port by a returning reflected wave of lower amplitude,
arriving from the closed end rear cone.
The clue is " contact discontinuity ". Thus the cold gas slug is much more able to be influenced by the hot return wave due to a large difference in all of the variables - pressure , density , temp and inertia.
Seeing that in print further reinforces the test I did to prove Jan correct and "the great leader " more of a tosser than we already thought.
The colder the duct surface surrounding the excess charge is , the bigger the " discontinuity value " and thus the stronger the push is to return the slug from whence it came.

[Vannik]

One of the things I am not sure about, but suspect about contact discontinuities is that is the difference between a header where the first part is straight compared to one that starts curving immediately from the cylinder interface. It should be obvious that as the gas travels down the pipe the cold and hot gas will mix more and more as it travels down the pipe. A curved pipe where the length the gas has to travel along the inside of the curve is much shorter compared to how far it has to travel along the outside of the curve. This creates a smearing or mixing of the contact discontinuity and lowers its effect.

A strong well defined contact discontinuity formed close to or inside the exhaust port passage seems to be a major advantage. This might be one of the reasons for the Wobbly Exhaust Port. If an engine is not developed for it, it will cause detonation if it is applied to the engine. I think the purpose of Yamaha's "detto button" in their straight pipes on the 500cc GP bike was to smear the contact discontinuity.

[jonny quest]

Vannik, you're starting to hit on why some engines don't care if it has a straight pipe attached to it, or one with many curves. Some engines lose power with a twisty pipe, others don't.

I'll add my thoughts to this after I figure out how to put my thoughts into words

[jonny quest]

It appears to me the hot gasses follow the outside radius of the pipe, while unburnt fuel tends to follow inner radius of the pipe. (Header early diffuser)

A cylinder more susceptible to transfer/exhaust short circuiting is more likely to lose power with a twisty pipe over a straight one

[Vannik]

It appears to me the hot gasses follow the outside radius of the pipe, while unburnt fuel tends to follow inner radius of the pipe. (Header early diffuser)

Flow through a pipe, especially unsteady compressible turbulent flow does not behave as we would think. The closest mind picture is that it forms two contra rotating cork screws going through the bend. The following pictures are a simplistic view of the process:

348298 348299

A better reference is:

https://macsphere.mcmaster.ca/handle/11375/21560

The download is free.

A bend does a very good job of mixing gas. Fuel droplets are not part of the gas and will probably accumulate on the outside of the bend.

[Muhr]

Flow through a pipe, especially unsteady compressible turbulent flow does not behave as we would think. The closest mind picture is that it forms two contra rotating cork screws going through the bend. The following pictures are a simplistic view of the process:

348298 348299

A better reference is:

https://macsphere.mcmaster.ca/handle/11375/21560

The download is free.

A bend does a very good job of mixing gas. Fuel droplets are not part of the gas and will probably accumulate on the outside of the bend.



I always get the vortex to start right after the bend when the pressure at the bottom decreases. has tried to change the CO2 level without major changes in results.
They say that the source code in this program is used by several Formula 1 teams, perhaps McLaren:lol:

[TZ350]

.
Edgecombe last weekend. F4/F5 combined https://www.facebook.com/tim.coopey/videos/10222757679404327

[Condyn]

FOS pipes I built made very excellent power on the very first pull on the dyno. Only 3hp shy of supposedly well developed pipes. These were built using the starting point 550 speed of sound variable. I feel as if there is gobs of power still left behind as this is version 1. I hope to model this engine and get a peak power egt from the donate-ee for simulations.

[Frits Overmars]

FOS pipes I built made very excellent power on the very first pull on the dyno. Only 3hp shy of supposedly well developed pipes. These were built using the starting point 550 speed of sound variable. I feel as if there is gobs of power still left behind as this is version 1. I hope to model this engine and get a peak power egt from the donate-ee for simulations.Glad to hear it, Condyn :niceone:.

[Muhr]

Here is a sim of 0mm radius 8mm and one ellipse./[/url]

Did with a little help from a friend a test on bellmouth unfortunately on the wrong engine (for obvious reasons), but maybe can give an indication of what to expect.

Engine: tm kz-R1
Dyno: Dynostar
EGT: Auto release 550 ° C
Compensation: 0.025 hp / kmh driveline loss (shown as 0.03)
Water temperature: 50c ° (external temperature controlled coolant)

Test:

Purple: With air box (Righetti)
Green: Without +5 on jetting for the same EGT for all below
Red: With little Bellmouth
Blue: With huge Bellmouth

[philou]

In dynamics, can the airbox add an unmeasurable addition to the dyno?

The air being tranquilized and not subjected to the eddies and the speed of movement

[nitro2tfx]

The next time I post I will post a screenshot of the pressure waves from a unique pipe we have used on 4 strokes. Yes I know nobody wants to hear about 4 strokes lol, but 2 stroke//4 stroke is not the point, the point of showing it is to show that a 2 stroke like exhaust pressure trace can be generated without using a 2 stroke type exhaust pipe and it can even be generated on a 4 stroke engine.

EXHAUST TRACE FOR A TYPICAL 4-2-1 EXHAUST ON A 4 STROKE
I know we aren't here to talk 4 strokes, but for reference sake, this is basically what an exhaust trace looks using a typical exhaust header design (on a 4 stroke).

https://hosting.photobucket.com/images/bb352/nitro1385/Typical_Aftermarket_4-2-1_Exhaust.gif?width=450&height=278&fit=bounds&crop=fill


EXHAUST TRACE FOR UNIQUE CUSTOM EXHAUST ON THE VERY SAME 4 STROKE ENGINE
This exhaust design generates a pressure trace that looks fairly similar to what is generated in a 2 stroke tuned pipe, BUT ths exhaust pipe looks nothing like a 2 stroke tuned pipe.
https://hosting.photobucket.com/images/bb352/nitro1385/TFX_Custom_Exhaust.gif?width=450&height=278&fit=bounds&crop=fill

So what is the point of posting this ? First, this unique custom exhaust design exists nowhere else but at TFX, it functions over a very wide rpm range and can generate a very intense low pressure. Second, the pressure trace looks a lot like a trace generated by a 2 stroke tuned pipe but it's design is completely different from that.

Third, and the main point of posting this is that this is a 100% creative exhaust design, it looks nothing like that which is used on 2 stroke or 4 stroke engines. It was not arrived at by using simulation software, nor altering a 4 stroke design, nor altering a 2 stroke design. Thge general design was literally pulled out of thin air using some creative thinking and logic, then made to work using real time exhaust pressure data. This very same general design could be fabricated in any number of different ways in terms of specific dimensions and 99 % of them will not work (as we learned lol). The reason we were able to arrive at the working version is because we had real time exhaust pressure data and could see where we were going wrong and the direction we needed to take to get where we hoped (I say "hoped" because we had never been there) to go. The design exceeded our hopes. This is an example of the "C" I was talking about previously when I mentioned that simulation software will get you from A to B quickly, but real time pressure data can get you from B to C even when you don't know if "C" exists, no matter what you design real time pressure data shows you what you have and you can see where you need to go.

[wobbly]

Well here we go again with me disagreeing and thinking in a completely differnt tangent to you Nitro.
What you have shown with the 4 stroke plot is simply what has been documented in many SAE papers describing what is needed , and comparing TFX data to simulation data to prove it.
Perfect example is SAE 2001 01 1797/4218.
This showed real time data against Optimum Power Technolgy's 4 stroke sim package ( I can use that as its free to Uni engineering depts )
Testing a straight pipe Vs a pipe/diffuser combination.
4Ts exhausts are simpler in that there are two effects that can contribute to power , pulling as wide and as deep a depression around TDC overlap as possible , and secondly a strengthening leftward
depression during the EVO period to reduce exhaust stroke pumping losses.

Achieving both together can accentuate peak power , spreading the two effects out favours powerband ( torque ) width.
Saying that achieving that plot could not be done just using a sim package is narrow minded rubbish - again it comes back to interpreting the data , and intellectual accuity in coming up with innovative
solutions to generate the desired end result.
Its easy to see on that plot that achieving even greater depression , sooner , between - 150 and -30 would reduce pumping losses during EVO. I dont need real data to see that trend at all.

The result certainly isnt limited by the sims ability to represent vey accurately the real time data - the big differnce being the time and work involved is exponentially less the harder the task at hand is.
Sadly for 4T tuning the exhaust plays second fiddle big time to the gains achievable with inlet tuning , the complete reverse of a 2T.
Variable length Exhaust = big 2T power , variable length Inlet = big 4T power.

EDIT - I could not resist adding a reply to this quote " I know we aren't here to talk 4 strokes, but for reference sake, this is basically what an exhaust trace looks using a typical exhaust header design (on a 4 stroke)."

That pressure trace result is NOT from a typical exhaust header , its a completely wrong example , there is virtually no help with exhaust stroke pumping losses , and there is virtually no depression around TDC overlap
ie that pipe setup is NOT tuned correctly to the chosen rpm.
The super secret setup IS tuned correctly so will obviously produce superior pressure trace shape and power as a result.

[dutchpower]

Sadly for 4T tuning the exhaust plays second fiddle big time to the gains achievable with inlet tuning , the complete reverse of a 2T.

Think Wobb if you have time for it !!!!!!!!

[TZ350]

<iframe width="560" height="315" src="https://www.youtube.com/embed/iv_RLU0Pw_A" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[TZ350]

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

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

<iframe width="560" height="315" src="https://www.youtube.com/embed/gH0EtQcWYFk" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

[Vannik]

EXHAUST TRACE FOR UNIQUE CUSTOM EXHAUST ON THE VERY SAME 4 STROKE ENGINE
This exhaust design generates a pressure trace that looks fairly similar to what is generated in a 2 stroke tuned pipe, BUT the exhaust pipe looks nothing like a 2 stroke tuned pipe.

Nitro,

That is a truly amazing trace. More so on a 4T engine. I know you do not want to disclose how you achieve it but is there a way we can do an NDA so I can test to see if a sim can duplicate it?

It does seem that there are a number of steep wave fronts in there. Very interesting.

[wobbly]

Well Dutch you have me by the balls , I read it twenty times , and thought on it all night.
If you fuckup the Exhaust on a 4T but have a perfect inlet system it will make around 70% of its power capability.
If you completely fuckup a 2T Exhaust , but have a perfectly developed inlet system it will make around 30% of its capability.
Is that not what I was saying, or am I so blind I cant see the woords for the trees.

[Muhr]

In dynamics, can the airbox add an unmeasurable addition to the dyno?

The air being tranquilized and not subjected to the eddies and the speed of movement

I do not know if it is a language barrier on my part.
But is not everything that is immeasurable or otherwise can not be proven "possible"

[philou]

I am French ( :facepalm: ) and my English is bad

I wanted to say :
who cannot measure himself against the dyno

With the calm air in the dyno room

[Vortex]

I am French ( :facepalm: ) and my English is bad

I wanted to say :
who cannot measure himself against the dyno

With the calm air in the dyno room

Bonsoir Philou,
Dis le en Français. Ce que tu dis là n'a pas trop de sence, désolé.

A+

[Muhr]

I am French ( :facepalm: ) and my English is bad

I wanted to say :
who cannot measure himself against the dyno

With the calm air in the dyno room

I think I understand what you're after. Airspeed can affect different intakes in different ways, which can not be measured in a dyno room?
Yes, it may be in some cases, in this case, the dyno run with the airbox was a reference and no test object.

[Condyn]

Starting to lay weld on my cylinders. Surprisingly going fairly smooth for my very first time running a TIG. Not exactly stacking dimes, but hey I only have a DC machine. Preheated to right around 300°f and kept it under 450°f to preserve the heat treat. Question regarding case reeds vs. piston cuts. Is there any noticeable advantage between a nice rear boost port and full skirt pistons, against big piston cuts and boyeson ports? The whole idea all along was to convert it to case reed because It is already under major construction. Time and effort should be ignored. I have a lot of that left in me. Stick with the plan or complete waste of time?

[wobbly]

Cylinder reeds with piston cutouts and or Boyesens can be made to work , the system needs analysis in EngMod to see if the proposed power level the rest of the
engine is being designed around can be supported.
But a case reed is a simple "weld it on and go " scenario.
No brainer in my book.

[lodgernz]

Wobbly, several times in your posts you've used the abbreviation RAD. By the context, I guess it's to do with environmental factors like temperature and pressure etc.
Can you clarify please?

[wobbly]

RAD = Relative Air Density , this is a calculated metric including Pressure ( mBars ) Temp ( Deg C ) and Humidity %.
The number is related to a standard set of numbers that give a reading of 100%.
Using RAD you can calculate engine Hp correction on a dyno or calculate a jet change to suit the weather.
I have changed to using Density Altitude , simply as the scale is bigger and I can hone in more accurately when getting a result that is in between jets.
Good thing is that you can dial up the closest airport weather station, anywhere in the world , ( that all pilots use ) on your phone to get a current RAD or Density Altitude number , and know that it is super accurate.
Here is an older jet chart I did in excel , one data point off the dyno , and two more from a perfect tune at the track.

[lodgernz]

Thanks Wobbly, that's really interesting.
On that chart, it looks as if the RAD is directly inversely proportional to the altitude. Is it really that simple, or have I misunderstood?

[wobbly]

Basically yes.
RAD 100% = 0 Density Altitude. And if the RAD increases to say 103 % ie more oxygen = more fuel needed = more power , then my joke at the track is that we are now under water
the air is so dense.
The best definition I have seen is - Density altitude is pressure altitude corrected for nonstandard temperature. As temperature and altitude increase, air density decreases. In a sense, it's the altitude at which the airplane "feels" its flying.

[Muhr]

I had this on the computer

RAD 100%
C°: 15.55
HUMIDITY: 0%
PRESSURE: 101.52 KPa
ELEVATION: 0M


SAE STANDARD

J607
C°: 15,55
HUMIDITY:0%
PRESSURE: 101,32KPa
ELEVATION: 0M


J1349
C°:25
HUMIDITY:0%
PRESSURE: 99KPa
ELEVATION: 0M


DIN STANDARD
C°: 20
HUMIDITY:0%
PRESSURE: 101,3KPa
ELEVATION: 0M


JIS STANDARD
C°: 25
HUMIDITY:0%
PRESSURE: 98,99KPa
ELEVATION: 0M


J1995
C°: 25
HUMIDITY: 0%
PRESSURE: 100 KPa
ELEVATION: 0M

[Muhr]

Got home some gears that I ordered, had a bit of a hard time deciding what I would have so I have both 1 and 1.5 of the bevel gears.
Someone who knows a little about gears who can tell about the pros and cons with a larger or smaller module, such as module 1 30 teeth or module 1.5 20 teeth.
Assume that there will be less tolerances when mounting on a smaller module

[philou]

I think I understand what you're after. Airspeed can affect different intakes in different ways, which can not be measured in a dyno room?

Yes you understood me.

For the gears, the language barrier will make this impossible

I invite you to try the "filengrenne" software which I think will give you a little answer for gears.

https://moodle.insa-rouen.fr/course/view.php?id=700

[edgefinder]

Wobbly, several times in your posts you've used the abbreviation RAD. By the context, I guess it's to do with environmental factors like temperature and pressure etc.
Can you clarify please?

Here's a good place to monitor weather where you'll be racing
https://airdensityonline.com/tracks/

[lodgernz]

Basically yes.
RAD 100% = 0 Density Altitude. And if the RAD increases to say 103 % ie more oxygen = more fuel needed = more power , then my joke at the track is that we are now under water
the air is so dense.
The best definition I have seen is - Density altitude is pressure altitude corrected for nonstandard temperature. As temperature and altitude increase, air density decreases. In a sense, it's the altitude at which the airplane "feels" its flying.

I'm wondering why altitude is a factor. I thought that the ambient air pressure and the temperature were enough to calculate the air density, the air pressure being partly dependant on the altitude anyway.

[lodgernz]

Here's a good place to monitor weather where you'll be racing
https://airdensityonline.com/tracks/

Thanks, that's useful for the big tracks, but only includes one kart track.
In any case, the air density varies all the time, so using an average value would be less useful.

[wobbly]

Ive been to every kart track in the country and the only one that has any issues getting current cell phone based weather data from a nearby airport is Rotorua.
Only due to being in the middle of nowhere .
But even there its possible to travel not far to get a signal.
The same app works in Vegas , Lonato or Te Puke.

[Muhr]

Yes you understood me.

For the gears, the language barrier will make this impossible

I invite you to try the "filengrenne" software which I think will give you a little answer for gears.

https://moodle.insa-rouen.fr/course/view.php?id=700

Looks really interesting! Have only seen a few videos with very limited understanding of French, but will try the program as soon as I get to a windows computer.
looks like it has a cam module?

[philou]

The software manages all common involute gears types of metric module and diametral pitch toothing.
They manage gears interference, teeth creeping,...

It's free. Only the post-processor and gcode function to codrive the cnc machines can be purchased

The export in CAD software is ok and free.

Warning to the units metric and impérials set between in the software

[Vannik]

Gasdynamics - Issue 2

Please let me know if you disagree, want something explained better etc.

348379

[41juergen]

Neels, is that correct or is the bulk temp lower because of the short circuting?

The effect on the pipe, other than the pulse shape change by the contact discontinuity, is that
on the older engine the pipe bulk temperature is higher than on a modern engine and the
result is a longer tuned length for the same rpm value

[Frits Overmars]

Gasdynamics - Issue 2. Please let me know if you disagree, want something explained better etc.Once again great reading Neels. To come across something described so clearly and understandably is a rarity. It reminds me of professor Alfred Jante's treatises that I cherish :niceone:.

[dutchpower]

I like only the last line Frits and Neels

. This promotes mixing of the gas and it smears the contact discontinuity. So if your
pipe relies on the primary or secondary contact discontinuity, having a bend in the header will
influence the way the pipe works. This is why some pipes are sensitive to curvature and others
not.

[Condyn]

Neels, I just want to add to the praise. To elegantly answer that many gray areas in my, and many others thoughts takes a great deal of skill. The FOS pipes I showed a few days ago that worked very well were originally built for, and tested on a vintage machine with the same “port map” on paper as the more modern machine that they did very well on. They did absolutely nothing for the vintage shaft duct, blowdown deficient engine. I somewhat expected that result from bits I have picked up on to do with diffuser design, but this really helped. Thank you very much.

[Vannik]

Neels, is that correct or is the bulk temp lower because of the short circuiting?

The effect on the pipe, other than the pulse shape change by the contact discontinuity, is that
on the older engine the pipe bulk temperature is higher than on a modern engine and the
result is a longer tuned length for the same rpm value

Yes, the short circuiting is less than the residual fresh charge in a modern engine, plus a modern engine has a cooled exhaust port duct.

The aim on a modern engine is to plug back into the cylinder only the coldest and purest part of the fresh charge in the exhaust port duct. That way we can prevent detonation and gain power.

[Condyn]

Shown is a sketch of something that I have been wondering about. The numbers are fabricated, more so the idea that is of question. A 1mm oversize piston and cylinder coupled with the engines factory 1mm smaller cylinder head, whilst using a L-ring piston. The squish gap is large at 1.6mm, just an everyday rider engine on pump gas. Being that it is an L-ring, is it still necessary to cut the head to the proper bore size, or would it be more logical to leave the smaller head diameter because the ring is a few degrees lower than the edge of the piston? I understand the nooks and crannies are of concern, but what is worse? You either end up with corners, or a larger gap between the ring and the “new” cut head. If I smash solder with the smaller diameter head it measures 1.6mm inside the squish band area and 2mm above the ring. If I were to cut the heads, there would be an even larger gap above the ring.

1mm larger diameter is .5mm per side. ( obviously but worth noting )
Apologies for the likely sideways photo.

[wobbly]

Having alot of mixture trapped at the bore edge is asking for deto as there is no cool surface close by , plus that volume burns way too late in the combustion cycle to help push the piston down effectively.

[Muhr]

The software manages all common involute gears types of metric module and diametral pitch toothing.
They manage gears interference, teeth creeping,...

It's free. Only the post-processor and gcode function to codrive the cnc machines can be purchased

The export in CAD software is ok and free.

Warning to the units metric and impérials set between in the software

I took the easy way this time but a super usable program that I will benefit from many times!:niceone:

[Frits Overmars]

Muhr, setting the correct clearance on a set of such gears is a nightmare. You should definitely google Cylkro Kronenräder. It offers a much better solution. If I had encountered it earlier, I would undoubtedly have recommended it for the Aprilia RSA.
348405348406

[philou]

The engineers blue marking is very good for locating the surfaces of the gear teeth and adjust the correct clearance

Old school style

348407

[Muhr]

Muhr, setting the correct clearance on a set of such gears is a nightmare. You should definitely google Cylkro Kronenräder. It offers a much better solution. If I had encountered it earlier, I would undoubtedly have recommended it for the Aprilia RSA.
348405348406

Thanks Fritz as always good tips. Have never heard of this before. I sent an email, we'll see what they answer, if they have something that would fit. I have done a bit of research on small teeth gears and understood that it is a bit tricky to succeed.

https://www.kggear.co.jp/en/wp-content/themes/bizvektor-global-edition/pdf/1.7_Backlash_TechnicalData_KGSTOCKGEARS.pdf

https://www.geartechnology.com/issues/0613x/bevel-gear-installation.pdf


The engineers blue marking is very good for locating the surfaces of the gear teeth and adjust the correct clearance

Old school style

348407

Thanks philou yes i think gear compound is a must

[TZ350]

.
Another video clip from Two Stroke Stuffing.
.

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

[wobbly]

Still cant stop getting annoyed when 8 of 10 clever dick ideas turn out to be flops.
Today , of all days at 30* C you would think cooling the transfer duct outer walls would be worth a bunch of power - but no.
Complete waste of time , so I tested and retested, doing all gear runs , as well as 6th gear WOT pulls - no power to be had.
A huge dissapointment.
I tested as well the expensive 3mm longer race plug , with the body machined back to put the gap close to the chamber center , again , no power at all.
Maybe the the new shallower chamber with the semi flat top piston makes the idea redundant.
Bugger.

[F5 Dave]

The amount of times I tested things that should work, like taking the kink out of an inlet manifold for a straight shot for example and found the dyno doesn't care, or rather the engine back to back swap, decides that this engine is not impressed. Another may be, but this one is not giving up its knickers (probably until you change something else).

[FJRider]

Still cant stop getting annoyed when 8 of 10 clever dick ideas turn out to be flops.


The good news is ... 9 of 10 BIG and well paid motorcycle engine research workshops ... have already tried those "Possible performance gain" methods.

They had the same result as you did.