ESE's works engine tuner

[F5 Dave]

Ahh, you'd spend it all on medicinal grain based beverages.

[41juergen]

I have a problem setting up the carb for a road going bike (TZR125 equipped with a Mikuni TM28 carb). I got the exhaust temp (and lambda) pretty much spot on when the engine is on the pipe. But when beeing at low a revs (e.g. between 4000 and 6000 rpm) the power is weak and the engine feels running very lean (also seen by the lambda trace, and I know the concerns of taking the lambda signal to verfiy how the fueling might be!). So the question is: how can I get the fueling much richer at WOT and below pipe action without messing up the setup at higher revs?

[husaberg]

I have a problem setting up the carb for a road going bike (TZR125 equipped with a Mikuni TM28 carb). I got the exhaust temp (and lambda) pretty much spot on when the engine is on the pipe. But when beeing at low a revs (e.g. between 4000 and 6000 rpm) the power is weak and the engine feels running very lean (also seen by the lambda trace, and I know the concerns of taking the lambda signal to verfiy how the fueling might be!). So the question is: how can I get the fueling much richer at WOT and below pipe action without messing up the setup at higher revs?

If its the same carb as the TMSS on the TZR250 they have a series of air correctors the f3 kit blocks these
The 250 TZR also has a PJ


https://www.kiwibiker.co.nz/forums/s...post1130168775
https://www.kiwibiker.co.nz/forums/s...post1130169246
https://www.kiwibiker.co.nz/forums/s...post1130169333

[41juergen]

If its the same carb as the TMSS on the TZR250 they have a series of air correctors the f3 kit blocks these
The 250 TZR also has a PJ

They are pretty much the same, also with a#50 PJ. It has the air correction screw (which is related to the idle sytem, mainly for low throttle, right?) and the main air jet (which is a #0.6 giving a close to constant lambda during the entire rev range beeing on the pipe). I have played a bit with a #0.5 MAJ with changes in lambda when the engine is on the pipe but not significantly below 6000 rpm...

[husaberg]

They are pretty much the same, also with a#50 PJ. It has the air correction screw (which is related to the idle sytem, mainly for low throttle, right?) and the main air jet (which is a #0.6 giving a close to constant lambda during the entire rev range beeing on the pipe). I have played a bit with a #0.5 MAJ with changes in lambda when the engine is on the pipe but not significantly below 6000 rpm...

out of those links

The air jet is used to vary the fuel curve.
With your carb at those revs you have about 4 circuits in play its just a case of juggling the overlaps to get the curve you desire.
if you read up the stuff in the second paragraph you should have a idea which bits to juggle
Unfortunatley its not just a case of saying richen the needle and it will sort it. although it may.
THe TZR250 race kit has a Larger needle jet and different tapper.
https://www.kiwibiker.co.nz/forums/a...id=4844&page=5

[41juergen]

out of those links

The air jet is used to vary the fuel curve.
With your carb at those revs you have about 4 circuits in play its just a case of juggling the overlaps to get the curve you desire.
if you read up the stuff in the second paragraph you should have a idea which bits to juggle
Unfortunatley its not just a case of saying richen the needle and it will sort it. although it may.
THe TZR250 race kit has a Larger needle jet and different tapper.
https://www.kiwibiker.co.nz/forums/a...id=4844&page=5

Yeah, I have played with the MAJ, but I saw mainly changes only when the engine is on the pipe.... Also at part throttle (let's say between 20-70%) and low revs the engine runs fine. When going to WOT at low rev's and then going backt to approx. 60% the engine revs up quite ok, only at WOT it don't get's enough fuel...

[husaberg]

Yeah, I have played with the MAJ, but I saw mainly changes only when the engine is on the pipe.... Also at part throttle (let's say between 20-70%) and low revs the engine runs fine. When going to WOT at low rev's and then going backt to approx. 60% the engine revs up quite ok, only at WOT it don't get's enough fuel...

It sounds to me that your cutaway and your needle Shroud need optimizing.
with the air Jet the main effect is at the top end of the curve.
the problem is to fix one part of the curve you will need to rejig the other settings as they overlap.

When taper an the positioning of the starts and thicknesses of ech taper on the needle will also effect this area.
Yamaha did likely a fair bit of work with the f3 race kit i would suggest the had good reasons for it.
if you are running the same carb on the same size engine it might pay to assume they knew what they were doing and there from there.

[Frits Overmars]

..I got the exhaust temp (and lambda) pretty much spot on when the engine is on the pipe. But.. at low revs.. the power is weak and the engine feels running very lean..
I know the concerns of taking the lambda signal to verify how the fueling might be.. how can I get the fueling much richer at WOT and below pipe action..

So you are aware that a Lambda sensor cannot tell you at all if a mixture is rich or lean. It can only tell you whether there is oxygen present in the exhaust gases.
Scavenging losses at low revs as a result of washed-through mixture will make sure of this oxygen presence. And misfiring because of an overly-rich mixture can enhance this presence even more, so enrichening the mixture at low revs may well worsen the 'lean' situation.
There are three things you can do about it. The first is copying Flettners cylinder with variable transfer timing. The second, somewhat simpler option, is to shift down when the engine threatens to drop out of its power band. The third option is to get an engine without a power band (and without two-stroke power),
a so-called foulstroke or Falschtakter .

.. at part throttle (let's say between 20-70%) and low revs the engine runs fine. When going to WOT at low revs and then going back to approx. 60% the engine revs up quite ok, only at WOT it don't get enough fuel...

You won't expect to get much power at part throttle, so whatever you do get, can be fine. At WOT you'll have higher expectations; you will also have a higher crankcase pressure and bigger scavenging losses. To some extent those losses can even be helpful in lowering the exhaust gas temperature to a level that is more suitable for those low revs.
Have you tried varying the ignition timing? Giving more advance should improve low-down power, but can become dangerous around maximum torque rpm.
A programmable ignition could be the best of both worlds, short of using that variable-height Flettner-cylinder or building a trombone exhaust pipe.

[41juergen]

It sounds to me that your cutaway and your needle Shroud need optimizing.
with the air Jet the main effect is at the top end of the curve.
the problem is to fix one part of the curve you will need to rejig the other settings as they overlap.

When taper an the positioning of the starts and thicknesses of ech taper on the needle will also effect this area.
Yamaha did likely a fair bit of work with the f3 race kit i would suggest the had good reasons for it.
if you are running the same carb on the same size engine it might pay to assume they knew what they were doing and there from there.

So you are aware that a Lambda sensor cannot tell you at all if a mixture is rich or lean. It can only tell you whether there is oxygen present in the exhaust gases.
Scavenging losses at low revs as a result of washed-through mixture will make sure of this oxygen presence. And misfiring because of an overly-rich mixture can enhance this presence even more, so enrichening the mixture at low revs may well worsen the 'lean' situation.
There are three things you can do about it. The first is copying Flettners cylinder with variable transfer timing. The second, somewhat simpler option, is to shift down when the engine threatens to fall out of its power band. The third option is to get an engine without a power band (and without two-stroke power),
a so-called foul-stroke or Falschtakter .

You won't expect to get much power at part throttle, so whatever you do get, can be fine. At WOT you'll have higher expectations; you will also have a higher crankcase pressure and bigger scavenging losses. To some extent those losses can even be helpful in lowering the exhaust gas temperature to a level that is more suitable for those low revs.
Have you tried varying the ignition timing? Giving more advance should improve low-down power, but can become dangerous around maximum torque rpm.
A programmable ignition could be the best of both worlds, short of using that variable-height Flettner-cylinder or building a trombone exhaust pipe.

@ Husa: May be I need to mention that I have changed the setup in the following way: the carb is equipped with a MAJ which has a connection to the outside atmosphere (and has some variable AJ's as beeing from my 3XV, may be similar as the RGV's have). I wanted to get rid of that and blocked the hose connector and installed a "fixed" MAJ #0.6 in the designed channel at the inlet bellmouth of the carb. With that I have changed the general setup at the needle jet significantly. I got back the ex temp within the power band by adjusting the MJ, all good there. What I did not have tried is a MAJ much bigger, e.g. #1,5 or so as I saw only a mall change when going up and down of an 0,1 increment for the MAJ. So the main question is if the MAJ also has a significnat influence on the fuelling when beeing below the power band.

@Frits: as said, I have learned from you guys what the bondaries of using a lambda sensor are... The engine is still not a seriuos tuned 2 stroker, it has the top end and intake from my 3XV which is a 28 hp 125 ccm setup. As mentioned, it is a road going bike with air filter, so shall run kind of reasonably propperly also below the power band... All the other stuff will come later during the winter time, I try to learn as much as possible (I know that will be limited) from that basic setup before going into serious power, but without Flettners idea
The bike has already a programable ignition, it has about 28°CA below the power band and it had better power below the power band when using the stock 3XV carb setup with the VAJ connected. So my prom is to get back the performance without using the VAJ's... A typical case of down tuning at the moment!

[adegnes]

Ahh, you'd spend it all on medicinal grain based beverages.

You know me too well...

[Flettner]

So, if we are going to run the exhaust out to 100 % of the bore width then are we looking at perhaps two exhaust ports? To get the best out flow.

[adegnes]

So, if we are going to run the exhaust out to 100 % of the bore width then are we looking at perhaps two exhaust ports? To get the best out flow.

Two ducts/pipes, one port, or two ports/ducts/pipes?
Might struggle with short circuiting even without going past 180°?

[ken seeber]

So, if we are going to run the exhaust out to 100 % of the bore width then are we looking at perhaps two exhaust ports? To get the best out flow.

Fletto, you know the answer. Don't fuck around with 2 exhausts when you can have three:





Just gotta get some wanker to finish it off..

[adegnes]

Fletto, you know the answer. Don't fuck around with 2 exhausts when you can have three:





Just gotta get some wanker to finish it off..

I need to catch up up in the foundry thread.
How's it running?

[jasonu]

You guys are so last year, (15 years ago)
Copper screw in top, built for my uniflow engine but never run. Clearly for the exhaust piston. Well finned underneath as to cool it best. These pistons were to run in the exhaust crankcases, fuel (petrol) air was at 6 to 1 ratio. Opposite crankcase were air only, subsequent mixing in the cylinder made the ratio out to approx 12 to one.

Best patent that before some prick nicks the idea...