Hi all,

I am having issues identifying the cause(s) for a lean spike that occurs a split second right after loading the engine.

It happens in any gear. It also happens when only lightly loading the engine (boost < 0psi).

Grounds have been checked, they are fine.

Any suggestion on where to look out would be greatly appreciated.

 

Looks like the TPS accel enrichment is too low. I would say check your TPS but since you datalog the TPS it seems to work fine. It should stumble or hickup a little too during the lean spike. Otherwise I would be a bit suspicous of other things.

IIRC you run a Vitesse setup so you should also ask John about this since he knows the software settings.

 

Acceleration Enrichment is the same used in 1000s of systems. If it is the cause it would have shown many times before on different cars.

- What year DME are you using?
- Have you unplugged the O2 sensor to see if it makes a difference?
- Have you checked the injectors? Can you try different injectors?
- Can you log the MAF signal along the rest of the variables?
- You have access to other 951s. Try your MAF + Chip/board in the other 951. Do you get the same results? Try the MAF + chip/bpard from the other car on your car? What results do you get?

 

John - could it be that the DME code does not translate to French well?

Either that or he is too close to the Large Hadron Collider….

 

Everything is possible!

 

John,
- What year DME are you using?
1990
- Have you unplugged the O2 sensor to see if it makes a difference?
What sort of difference should it make since the AFR is fine past the initial load?
- Have you checked the injectors? Can you try different injectors?
No, and I can't
- Can you log the MAF signal along the rest of the variables?
How? Again, if there is a problem with the MAF signal then why is the AFR fine past the initial load?
- You have access to other 951s. Try your MAF + Chip/board in the other 951. Do you get the same results? Try the MAF + chip/bpard from the other car on your car? What results do you get?
Is it ok to install a 2.5/72lbs chipboard on a 3.0/83lbs car?

Chris,
FYI the Vitesse PB doesn't work correctly if it's connected to a laptop that's not completely set up in English.

 

- Have you unplugged the O2 sensor to see if it makes a difference?
What sort of difference should it make since the AFR is fine past the initial load?
Unplug the O2 and see if it makes a difference!

- Have you checked the injectors? Can you try different injectors?
No, and I can't
Then how would you rule out the injectors?

- Can you log the MAF signal along the rest of the variables?
How? Again, if there is a problem with the MAF signal then why is the AFR fine past the initial load?

If there is turbulence or a loss in voltage. Again, you MUST look at all the variables! If you do not log the MAF signal, how can you rule it out?


- You have access to other 951s. Try your MAF + Chip/board in the other 951. Do you get the same results? Try the MAF + chip/bpard from the other car on your car? What results do you get?
Is it ok to install a 2.5/72lbs chipboard on a 3.0/83lbs car?

Injectors must match chip/board. You can try the 72# with the 83# chip/board, set the FQS to richen the mixture. WARNING - just to try if it makes a difference - Do not run it under boost.

Chris,
FYI the Vitesse PB doesn't work correctly if it's connected to a laptop that's not completely set up in English.

As Chris said, it's a language barrier. The compatibility issue relates to the decimal point "." or ",".

 

Pleased to say this issue was partially addressed by improving the alignment/indexing of the MAF housing with the J-pipe.
The SFR J-pipe I use doesn't seemed to be curved the exact same way as the Vitesse J-pipe and realigning the MAF sensor with the radius of curvature of the J-pipe has helped much.

Well, there is still a little lean spike but it's not as "excessively" lean as it was before and it should not be cause for concern as I don't get any blinks of knock anymore right at the moment I floor the throttle (Vitesse = top stuff).
I suppose I will have to live with it if I don't ditch the Bosch Motronic.