ESE's works engine tuner

[adegnes]

I had a similar problem, motor lean and cold when I was running Methanol. The cure was to blend the fuel with Acetone to reduce the fuels cooling effect. I had to get the motor to run warmer so the fuel actually evaporated. Maybe you will need to blend your fuel too, but you would think 280F - 138C would be warm enough ....

One would think so...
Thanks, I'll try blending with acetone.
I hope this is fuel related not some other issue.
Engmod says peak power @ 15500rpm. In the simulations I used the default temperature numbers + wobblys recently posted guidelines on rpm dependent exhaust temp. My real numbers could be vastly different I suppose...

[adegnes]

Seems like "cht", "egt", or any other three letter word is not a valid search term on this forum, I get zero results. 4 is the magic number, "idle" works fine. Dumb

[bjorn.clauw.1]

Seems like "cht", "egt", or any other three letter word is not a valid search term on this forum, I get zero results. 4 is the magic number, "idle" works fine. Dumb

I use google custom search engine for looking up older items (items just posted don't show up directly)
https://cse.google.com/cse/publicurl...90:5pd9xdluxce

[adegnes]

I use google custom search engine for looking up older items (items just posted don't show up directly)
https://cse.google.com/cse/publicurl...90:5pd9xdluxce

Great tip, thanks!

[bjorn.clauw.1]

Re cooling the spigot in KZ2 engines - yes, this idea if done by milling slots thru the flange face on the cylinder allows water
to cool right around the duct to the face, then also the steel spigot face is cooler as well if you cut the slots thru the gasket material.
I can touch the tapered spigot on the engine after a hard dyno pull without being burnt.
As you say this keeps the trapped mixture in the cylinder duct much cooler,and the egt further out in the header dropped as well.
I can run at least 2 jets leaner to get the egt back , without getting into deto using that system.
The pic is an early testing one, now the slots go right thru to water,top and bottom.

The 100cc engines really wide power band is down to the pipe design, with its series of bleed holes in the rear cone.
This pulls down the peak power and adds plenty at the bottom, and in the overev area.
Take that pipe and remove the rear cone holes,and it becomes all but impossible to tune the pumper carb properly,and the power band is basically 1/2 as wide.
OK for a slipper clutch setup on direct drive, no good at all without the clutch set to peak torque rpm.
The 3 port system has plenty of STA for the power produced, and the scavenging regime has been slowly developed over time to enhance the band width as well.

Excellent info, thanks for sharing! Regarding the 100cc pipe; can we say that a properly controlled sliding exhaust could mimic the wider powerband and maybe even give a little more peak power than the 100cc pipe?

I'm currently trying to apply all the things I have learned here onto a rs125 aprillia engine. (Also finishing the engine testbench) I believe Frits once said that Jan Thiel modified a reed intake engine to give 48hp. I was wondering if anybody had any info on this. Also not sure what to do with the large boyesen intake ports on the aprilia.
I always thought that big boyesens delivering the fresh charge directly into the transfers could be an advantage, but finding any information on this is proving to be hard.

[Frits Overmars]

Regarding the 100cc pipe; can we say that a properly controlled sliding exhaust could mimic the wider powerband and maybe even give a little more peak power than the 100cc pipe?

A properly controlled sliding exhaust will give a lot more power than the 100 cc kart pipe, and provided it has enough movement, it will also give a powerband that is at least as wide. But sliding pipes won't be allowed in karting.

I believe Frits once said that Jan Thiel modified a reed intake engine to give 48hp.

That was 49 hp, measured at the gearbox exit shaft. The engine was the reed-valve Derbi 125 cc GP-engine of 2004.

not sure what to do with the large boyesen intake ports on the aprilia.

That sufficiently identifies which Aprilia cylinder you are talking about. And I cannot repeat it often enough: check the coolant passages each side of the exhaust duct on that cylinder; they may be partly of even completely blocked.

[bjorn.clauw.1]

A properly controlled sliding exhaust will give a lot more power than the 100 cc kart pipe, and provided it has enough movement, it will also give a powerband that is at least as wide. But sliding pipes won't be allowed in karting.

Would be used on a rs125. I allready turned the cilinder around so I can make a straight (150mm sliding) pipe. Only downside is intake is against crankshaft rotation. Cilinder will use a cast iron sleeve with the top part exposed to the coolant (following Makr's design)

That sufficiently identifies which Aprilia cylinder you are talking about. And I cannot repeat it often enough: check the coolant passages each side of the exhaust duct on that cylinder; they may be partly of even completely blocked.

Yes, the passages are really tiny, will open them up (a lot) to improve the coolant flow. Following your advice I modified a vw waterpump which is now belt driven from the ignition rotor and flows 45l/min at 10000rpm. Exhaust duct will be modified to follow wobbly's design. Port geometry will be rsa125 style. Only unknown is the intake geometry with the boyesen ports. No idea if this will flow enough to match the rest/if there is any room for improvement here.

[Juho_]

I always thought that big boyesens delivering the fresh charge directly into the transfers could be an advantage, but finding any information on this is proving to be hard.

I have believed, that the boyesen ports are supposed to be directed to the case.



Like in the YZ 250 '96-> cylinders. Older YZ 250 cylinders have kind of same design as Rotax 122/123's.

Rotax 122/123 cylinder's boyesen ports are aimed nearly straight to the A/B transfers divider (or atleast it looks like that, when watching pictures I found).


Correct me if I'm wrong!

[bjorn.clauw.1]

Rotax 122/123 cylinder's boyesen ports are aimed nearly straight to the A/B transfers divider (or atleast it looks like that, when watching pictures I found).


Correct me if I'm wrong!

That is correct, they are aimed straight ahead. My line of thinking was this could help the inflow in the cylinder when piston is at bdc and the engine is on the pipe. Making the transferduct volume larger because the volume behind the reeds can be added to the transfer duct volume. (Straight in means no bends need to be negotiated to suck mixture in). Just a thought as the common belief on this is that the mixture going in the cylinder is that amount that resides in the transfer ducts.

[AndreasL]

Sorry to interrupt the interesting ongoing discussions with some old hat and basic questions...

We have all learnt that putting a "to good" pipe (i.e. FOS Concept, Wobbly etc) at a "crap transfer old school cylinder" is a bad thing.

But how good or bad a pipe is possible for the crap setup?

Any rules of thumb, ideas and guides besides/in addition to "run a 1000 random sims in EngMod" how to find the limit would be very helpful.

The FOS Concept have got me started but its obvious that I need to reread everything about pipes posted here.
This is not easy! (Remember wobs posted a "guidelines" to what was effecting what part of the pressure trace curves, but that was some 900 pages ago!!! Need to see if I can find it again.)

Anything specific to look for in EngMod to see when the pipe is sucking to hard at the transfers, letting the fresh gases take a short cut out the exhaust?

Thanks in advance!

[wobbly]

As I have shown before there is no intake flow when the piston is at BDC, the reeds are closed.
But there can still be significant flow as the transfers are closing edit due to inertia effects in the intake length.
This stream that is perpendicular to the B duct entry can badly affect the flow regime at the entry to the B duct, and no matter what is
done to enhance B port flow ( ie higher, wider, hooks in the port etc,) no more power eventuates.

Thus it would seem that directing the flow downward into the floor of the cavity under the transfer duct entry area is better than a straight shot
that ends up crashing into the B duct front wall.

Re the " overscavenging effect " of super efficient pipes on crap transfers, I have emailed Neels to see if he can detail the best way to identify the effect actually occurring in EngMod.
All the engines that have this possible issue I have dealt with, also have the problem that a fat pipe simply wont fit on the bike ie TZ350.

[AndreasL]

Thanks wobs for running my errands!

On a side note, yesterday I was informed of some dyno results from 2 other cylinders like the one I try to sim in EngMod.
Not having any real dyno numbers up until now for what is possible with this engine have made me VERY doubtful to my skills using EngMod and if the program is realistic to use "as is", without the so hated fudging of numbers, to have believable results for my type of engine.

The conclusion seems to be that I have to apologies to Neels and I hope that I have some comparisons between sim and dyno to show in a couple of month. (Yes, this is sloooow.) Hopefully it shows that even a 50cc old moped engine, "tuned to death" at 6-8 bar BMEP , is handled well by EngMod even when run by a n00b at 2t tuning. Hopefully...

[bjorn.clauw.1]

As I have shown before there is no intake flow when the piston is at BDC, the reeds are closed.
But there can still be significant flow as the transfers are closing edit due to inertia effects in the intake length.
This stream that is perpendicular to the B duct entry can badly affect the flow regime at the entry to the B duct, and no matter what is
done to enhance B port flow ( ie higher, wider, hooks in the port etc,) no more power eventuates.

Thus it would seem that directing the flow downward into the floor of the cavity under the transfer duct entry area is better than a straight shot
that ends up crashing into the B duct front wall.

Thanks for the explanation Wobbly, will add redirecting boyesen ports to my (lengthy) to do list.
(This would also explain why rotax opend up the boyesen ports towards the bottom of the transfer duct entry on the new rotax dd2 and made a guide for them in the crankcase halves - compared to the older 122 cylinder)


Still interfering with b duct flow but a lot better then the older 122 style. I will cut them out even deeper to mimic the YZ250 Juho posted.

[AndreasL]

(remember to choose "flat view")

Do you have to be a member to have this option?
If not, I have to be blind or something...

Tried to register but had the same "password missing problem" TZ reported.

[bjorn.clauw.1]

Do you have to be a member to have this option?
If not, I have to be blind or something...

Tried to register but had the same "password missing problem" TZ reported.

Jep, when registered "flat view" appears. (Registered without problems)