1150 EF updating project

[lecroy]

Have been try to adjust the efi below 2000 r/min , but it seems to be impossible to get it good .
I need to move the throttlebody as close as possible to the plenum ( need a smaller throttlebody , about 1.45" - 1.9" in diam. ) .
Now there is too big air volume between throttlebody and engine . Air starts to "pump" inside the whole inlet system below 2000 r/min .

Are you really moving the throttle body, or just going smaller? If you move it, are you thinking to have it after the pump?

I thought you had a bypass valve in there now to solve it? No improvements?

I have a friend with a home made bike that has the turbo way way out in front. Little draw thru system. That thing has loads of pipe and a very small motor. Seems to idle fine. I was always surprized because all that fuel/air has to go through all those bends and such before it gets into the engine.

You are thinking that it is hard to meter the small amount of air flow with a grand ganyon sized valve versus a garden hose?

[Blower]

Are you really moving the throttle body, or just going smaller? If you move it, are you thinking to have it after the pump?

I thought you had a bypass valve in there now to solve it? No improvements?

I have a friend with a home made bike that has the turbo way way out in front. Little draw thru system. That thing has loads of pipe and a very small motor. Seems to idle fine. I was always surprized because all that fuel/air has to go through all those bends and such before it gets into the engine.

You are thinking that it is hard to meter the small amount of air flow with a grand ganyon sized valve versus a garden hose?

Iīm going to set a new smaller throttlebody as close as possible (without big modifications) to the plenum.So it will be in the pressure side of the supercharger .
Itīalso easier meter the air flow ( as you write ) , now the first 1/3 throttle is where it happens a most ( too big throttlebody ?) .

The bypass valve I made helps a lot , but there is still some difficulties to get efi working correct under 2000 r/min . Ie. when slowing down throttle off and pulling the clutch , the engine first rews up and then dies .
I have taking a datalog from Megasquirt , but it shows everything to be ok .

I think a bike with draw thru turbo and carburator is easier to get running idle and slow rews than a bike with roots type supercharger .

[lecroy]

That's a pretty big change to move the throttle body after the pump? But if it doesn't work the way you have it, there's no choice?

Having never played with with anything close to what your doing, I can't offer anything but a "good luck". Not sure why the little tubo bike would be easier to get things working. He does have a pretty small carb on it. Same basic arrangement you have. Turbo in front with long tube running from front to back of motor. Big difference is he puts the fuel in the front of the system. Hard to believe it works as good as it does. He rides it up to the line and back and it sounds very smooth when it does not explode. I have some pictures of it somewhere if you want me to dig them up.

[Blower]

That's a pretty big change to move the throttle body after the pump? But if it doesn't work the way you have it, there's no choice?

Having never played with with anything close to what your doing, I can't offer anything but a "good luck". Not sure why the little tubo bike would be easier to get things working. He does have a pretty small carb on it. Same basic arrangement you have. Turbo in front with long tube running from front to back of motor. Big difference is he puts the fuel in the front of the system. Hard to believe it works as good as it does. He rides it up to the line and back and it sounds very smooth when it does not explode. I have some pictures of it somewhere if you want me to dig them up.

Itīs not so big change . Bypass is already at right place , I need to cut about 4" away from pressure pipe before plenum , install new throttle body with old tps-sensor and throttle cable , replace old throttlebody with pipe and start the engine .
Well , itīs maybe not so simple , but ...

There is one major differens between turbo and a supercharged systems .
When turbo charged engine is idling or going with light load the turbo does not make any pressure . Turbo nearly resisting airflow to the engine .
Supercharger spinns all the time at same amount over engine revs. ie my case 30% faster than engine trying to pull thru throttle body 42% more air than the engines displacement .
This together with too big intake system volume makes fine tuning in light loads difficult .

[Blower]

And yes , it would be nice to see pictures .

[lecroy]

I was thinking that this was the point of the by-pass. No pressure at idle, similar to the turbo.

I'll see if I can find them tonight for you.

[lecroy]

Sorry for the delay. The frame, fuel tank, body, exhaust are home made. He rides it to the line and back. Electric start. Has a Busa clutch on it now. Idles smooth with all that tube.

/nCowboy's turbo skunk bike

/nCowboy's turbo skunk bike

[Blower]

Wow , thatīs a real rat dragster !
Heīs got a lot smaller intake system volume , than I have . Thatīs why heīs bike idles
and runs smoothly .


Btw , here is my EF dyno sheet 07.16.2008

[lecroy]

> Wow , thatīs a real rat dragster !
LOL! Its a skunk, not a rat. Notice the white stripe down it's back.

/nCowboy's turbo skunk bike

Yes, smaller intake and much smaller pistons to suck it down with.

Numbers look good so far. I assume that's SAE corrected on a wheel dyno.

[Blower]

> Wow , thatīs a real rat dragster !
LOL! Its a skunk, not a rat. Notice the white stripe down it's back.

/nCowboy's turbo skunk bike

Yes, smaller intake and much smaller pistons to suck it down with.

Numbers look good so far. I assume that's SAE corrected on a wheel dyno.

Itīs SAE corrected dyno and arear wheel power .

I get assembled a new throttlebody and dump valve . In the old tp place I put a pipe with aircleaner .
What a difference to the old system ! Idle is better than ever and low speed rideability is much better than before .
In the first testride I made some unwaited wheelies and burnouts . Now it performīs like supercharged bike should .
Made a datalog ride today and datalog shows a more stabile boost on whole rpm range .
Boost is now from 4000 to 9000 r/min 0.42 bar .
And the sound ... supercharger noise is now much louder than before and every gear change the dump valve makes a loud PSHIIII sound .

[lecroy]

Good to see both you guys posting again. Sounds like you have made some good progress as well. I had to do the conversion to PSI LOL. I would think the bike would be very driveable if you like the thrill of staring down death, and should live a long time at this pressure.

I think that skunk bike is using some 1.1 bar or so plus he sprays nitrous off the line. That poor little 650 twin was never meant to make that sort of power. He breaks a lot of parts and keeps beefing things up.

Post some new pictures of your fabrication work. Always top notch stuff!

[Blower]

Here are some pics :

The dump valve and the throttle body




Throttle body is from BMW 1150 , "slightly" modified and in itīs injector place is
home made "choke" .




And the whole bike

[rapidray]

WOW!!! VERY nice workmanship! Ray.

[drhach]

I thought I recognized that throttle. If I may ask, how did you get the 4-wire TP sensor to work? I have one that I'm trying to fit to a project of mine, but the 4-wire TP sensor is not linear. I have resorted to trying to fit a Bosch 3-wire unit to the Throttle Body. You are using a megasquirt ECU right?

[Blower]

I thought I recognized that throttle. If I may ask, how did you get the 4-wire TP sensor to work? I have one that I'm trying to fit to a project of mine, but the 4-wire TP sensor is not linear. I have resorted to trying to fit a Bosch 3-wire unit to the Throttle Body. You are using a megasquirt ECU right?

TPS is from Volvo 750 . I made 1" long adapter shaft and a adapter plate to get it fit to the BMWīs throttle .
ECU is a Mini Megasquirt , made by Arttu H .