ESE's works engine tuner

[koenich]

AFR and EGT

I assume thats what you used to change the mapping!? I meant the OE setup, what is the Crank Pressure Sensor for and which factors will influence the injection?

[wobbly]

AFR = Lambda = LSU

[TZ350]

... what is the Crank Pressure Sensor for ...

Average crankcase pressure in a two stroke is much the same value whether you are making power or not.

The average crankcase pressure reading at idle is close to atmospheric and changes only slightly as the reeves head towards max torque.

I suspect the Crank Pressure Sensor might be being used for finding the "Difference" between "Max" and "Min" crankcase pressures during an engine cycle.

This "Difference" varies depending on the power output being developed and could be used as one of the factors for determining injection volume. Much like a MAP sensor on a four stroke.

4 stroke MAP - Lowest MAP pressure = 2 stroke smallest "Difference" .... 4 & 2 stroke engines idling.
4 stroke MAP - Higher MAP pressure = 2 stroke larger "Difference" .... 4 & 2 stroke engines making power.

The bigger the pressure "Difference" in a 2 stroke crankcase the greater the air flow and therefor injected volume required.

I would love to know more about how KTM actually use their pressure sensor on the EFI bikes.

[TZ350]

.

Pumper carburetors and pumper fuel pumps on a 2 stroke are activated by "Suck" and "Blow". "High" and "Low" crankcase pressure pulses.

The absolute pressure value of each individual "High" and "Low" pulse changes depending on the amount of power being produced.

But the "Average" value, ie ("High" plus "Low")/2 remains pretty much the same.

And the "Difference" value, ie ("High" minus "Low") changes according to the power being produced. More power, greater "Difference".

[dtenney]

Hello,




Decided to create account here as I have some problems with methanol and this forum has a lot of experience about it.

I have old air cooled Suzuki DS80 engine that im running with VP fuels M5 methanol. It works quite well and makes 12% more power than with 98 petrol. But problem is that after dyno- or top speed pull when you perss clutch it keeps reving insanely high for few seconds even the throttle is closed.
It must be killed with engine braking and brakes. Its even detonating after top speed test if clutch is pressed and needs a long engine braking. I've had bit similar problem with petrol but not even nearly so bad and it ends quickly.

Carb is chinese PWK 26mm with #32 idle jet and #220 main jet. Needle jet and needle are from bigger PWK. Needle is shortened to suit 26mm carb and randomly grinded with drill and sandpaper. It has electric fuel pump from K&N and needle valve flows 6,6dl/min. Engine has around 19whp with short dyno test.

What is the mechanism behind this behavior and any suggestions how to get rid of that?

Here is a little video, unfortunately first pull is missing where problem was worst. Second pull still has some and third for some reason is not so bad on this test. https://youtu.be/j8PJIAayKUU

We have dyno'd M5 as well and had the same problem with the lean condition likely because of the oxygenators used. The M1 works almost as well and is pure methanol and does not cause the lean condition. Thus we only use methanol without the added oxygenators.

[Condyn]

What is the thinking behind using multiple sheet metal thicknesses in one pipe? I faintly remember reading on here that Honda did that at some point, but have not figured out how to search effectively.

I notice when I have built a pipe out of thinner material it seems to light faster, and gets hotter to the touch much sooner. Does that also mean that the thin pipe also sheds heat faster than the thick one?

I short duration drag race AIR cooled snowmobiles which utilize a CVT, so rpm is maintained from about 5 feet from the launch to 500 feet. I purposely tune my clutches to allow some rpm increase down the track to follow the pipe as it heats. The pipe heat (open tipped fast response probe in belly) never stabilizes in 500 feet. The rate of temp increase slows, but it never plains out.

On the dyno, more warmup time pushes the peak power rpm further up in the rpm range. This comes as no surprise, but I did notice the power curve is overall lower with the rpm. VANNIK pointed out that this was likely due to the exhaust duct getting hotter and making the slug less dense. Makes sense.

The reason for my multi-thickness question is because I would like to heat the pipes on my warm up stand to my normal staging temperature as fast as possible and also give myself the best chance at keeping the duct as cool as possible. Would a thick header and thin rest of the pipe help this situation?

I have loads of belly temp datalogs with the thick pipes, and will be comparing to the thin ones once I build them in the next few weeks. I will share any interesting data I acquire.

[wobbly]

Answer to the question is the thin material heats quicker and cools quicker due to its inherent thermal inertia.
Honda and Yamaha Kit engines used 0.6 mm for the header and the last 1/2 of the rear cone ( in Ti of course ) with the rest of the body in 0.8.
Thus the 2 hottest parts of the pipe cooled quicker to improve acceleration after backing off into a corner , then heated up faster to give max top end on the straights.
Im completely unsure as to the use of this effect in a CVT situation , but would be interested in your findings.

[Vannik]

I short duration drag race AIR cooled snowmobiles which utilize a CVT, so rpm is maintained from about 5 feet from the launch to 500 feet. I purposely tune my clutches to allow some rpm increase down the track to follow the pipe as it heats. The pipe heat (open tipped fast response probe in belly) never stabilizes in 500 feet. The rate of temp increase slows, but it never plains out.

I have loads of belly temp datalogs with the thick pipes, and will be comparing to the thin ones once I build them in the next few weeks. I will share any interesting data I acquire.

Have you tried a 2-step approach like the 4T turbo engine guys do? They retard the timing and limit the rpm while staging to build turbo rpm but on a 2T you should be able to do the same to get the pipe to its optimum temperature. The moment they launch the timing goes back to optimum for power. If you could do this and use a thick walled pipe to get to and then stay at the optimum pipe temp maybe some gains?

[Condyn]

Wobbly I will be sure to share my findings. I am slowly learning how much influence real world field conditions layer on the variables.
Vannik, the 2 step idea has crossed my mind. It was always strictly forbidden in the classes I race in, however now I do not see it in the rule book. Might have to give that a try. Thank you both.

[HSuomi]

I have two questions that may point to what is happening.
First , what is the actual float valve orifice size.
Second , if you are using a pump with a return and a jet restriction back to the tank , put a T in the fuel line next to the carb inlet , and run a clear fuel line upwards say 2M off this T.
Start the pump and rev up the engine.
What is the pressure height of the fuel in the clear line above the gasket face of the carb bowl , when the engine is reved.

Float valva hole is drilled to 3mm.

I can test this next time when I do some other testings. Is the idea to find how much pressure the float valve is seeing?

There has been also comments about the oxygen/nitro in M5 methanol causing lean situation. But why is the engine running normal idle before the dyno/speed runs? What actually happens after the run to keep the rpm high? It goes normally back to idle when I rev it before the runs.

[wobbly]

Only other issue is that I have done a direct back to back with 1mm Vs 0.6mm pipes , and the thin wall pipe always makes more power on the dyno.
We cant do this in KZ as the pipe wall is spec at 0.8.

[Flettner]

Float valva hole is drilled to 3mm.

I can test this next time when I do some other testings. Is the idea to find how much pressure the float valve is seeing?

There has been also comments about the oxygen/nitro in M5 methanol causing lean situation. But why is the engine running normal idle before the dyno/speed runs? What actually happens after the run to keep the rpm high? It goes normally back to idle when I rev it before the runs.

Intetesting, with my 350 on E90, the tuning map required when the engine is cool is different to the map required when hot. It seemed that 70 / 80 degrees C is about the cut off. Above this needs about a 7 to 10% increase in master fuel. As it cools off it needs to go back to orginal fuel map again. Lucky the LINK ecu has a temp / fuel graph able to adjust according to temp.

Why? I guess above 70C the ethanol vaporises completely, under, not so. When ethanol vaporises completely I think thats when it releases more oxygen..... needing more fuel.
Im speculating, all I know is thats what my Kawasaki needs to run cleanly throughout its operational load variations.
It runs crank case EFI.

[Grumph]

I'd agree with those temps. Running a water cooled 4T on methanol my experience says use a 70C thermostat. Done just that on roadrace bikes, speedway cars and sidecars - and vintage race cars. One such with decades of poor running history cleaned out and ran better than ever with that change.

[Flettner]

I might add, trying to get the Kawasaki to run E90 through a carbutetor was pretty much impossible. Either too rich or too lean, set it for good power mid race and it would blubber for the first few laps or set it nice for the first few laps and have serious detonation after a lap or two.
EFI is the fix.

[Pursang]

I might add, trying to get the Kawasaki to run E90 through a carbutetor was pretty much impossible. Either too rich or too lean, set it for good power mid race and it would blubber for the first few laps or set it nice for the first few laps and have serious detonation after a lap or two.
EFI is the fix.

OK for Formula Libre .... tough for 'Historics'. Can we please have a simple analog thermal controlled main jet?