Engine stalling at 10-20% throttle (no boost)

[master_328]

Hi guys, I have a kitcar with a hayabusa engine and a mcXpress turbokit running 16psi. The engine is running fine under full boost and in idle, but it`s stalling in low throttle area, when boost is "0". A/F drops under 9 in this 10-20% throttle area. I already checked atmospheric (AP) and map (IAP) sensor, voltage output is ok referred to repair manual. But after some testing, I found a problem...when I put a small vacuum on the atmospheric sensor, the ecu enriches mixture and when I put a bit of pressure on it, it leans out mixture. That`s exactly the opposite it should do referred to my repair manual. Is my ECU blown?
I have no further idea. Any help is highly appreciated. Which a/f ratio are your engines running in this condition, should be 13 - 14.

Thanks Christoph

 

[NearDeath]

Make sure the fuel regulator is NOT seeing vacuum. Had an issue where when I was coming off boost, the vacuum was so great, it took my fuel preassure down low enough to make the bike die...

Moved the fuel regulator vacuum hose from throttle body seeing vacuum to tapped up-pipe seeing no vacuum.

CLoud

 

[master_328]

It`s a rising rate fpr, so it should see vacuum and boost.

 

[turbojonn]

If it's a begi rising rate regulator it should only see positive pressure. I have one and it has only one line going to it. That line is a positive pressure line. This line has a check valve in it so it can not see vacuum.

 

[master_328]

Hello, thank you, but the OEM fpr also reduces fuel pressure in vacuum?! I`m tracking another problem, perhaps the ECU is the wrong one for my engine, does anybody has part numbers for the year the engine was built in?!

 

[NearDeath]

Does it die when you come off boost?

 

[master_328]

Hello, no, it just stalls at 10-20% throttle, when there is no vacuum and no boost. (manifold pressure=atmospheric pressure). Air/fuel ratio goes down to under 9. Boosting is ok (perhaps a bit too rich, idle is also ok).

I think I have a sensor/ECU problem, since the ecu reacts the wrong way on sensor input. (when I put vacuum to the atmospheric sensor, the ecu injects more fuel and it should lean out mixture) The whole engine was built for me by a company, but I think they mixed up something. I already checked sensor output of my sensors, they are ok referred to my repair manual.

Can you guys tell me the year of your bike and the part numbers for ECU, MAP (IAP) sensor and atmospheric (AP) sensor? Do you know which parts were changed by susuzki over the years?

Part numbers on my engine:

ECU / ECM
32920-24F01

MAP (IAP) sensor:
15620-02F00
100798-4210 Denso number

atmospheric (AP) sensor:
81A0
079800-4990 Denso number