Nistune Forums

Hi,

This might be of interest to you all - my friends car is over fuelling. It has been mapped by a reputable chap and was until recently running spot on 12AFR when on WOT. Boost pressure is either 1.2 BAR (low) and 1.4 (high).

Summary - 12AFR before, nice
10.5 AFR after, not nice

We have used the same rolling road for all the results below by the way -
this was when the car was running nicely. The only changes to the car have been a single peice propshaft, and a change of exhaust to an apexi n1 evo (used to be a 3" system with 4.5" back box-no issues with this just wanted a different sound)

RR last year setup nicely
http://i161.photobucket.com/albums/t203 ... A61347.jpg

The RR resulted after those two changes is this.
low boost

http://i161.photobucket.com/albums/t203 ... A61349.jpg

high boost

http://i161.photobucket.com/albums/t203 ... A61350.jpg

compression tested the engine 140,135,140,140

boost leak checked the intake system up to 20psi the system is spot on.

Sure enough, logged the run out today with the car and looking at the fuel map, as soon as it comes on boost, it starts accessing the last or second to last column TP load.

The AFM was suspect but we have looked at that and Nistune shows it is producing the right results up the rev range, no anomalous readings.

Surely a proshaft and exhaust change shouldnt cause such an issue?
Results on a postcard if you can, I will attach the datalog for anyone that is really looking into this.

Thanks for any suggestions!

fuel pressure been checked? maybe some sort of blockage or restriction in the return line?

i know who tuned this, he usually has mid to high 13's during the boost transition zone from what ive seen in other maps. has this area been affected aswell?is the map rich throughout or only at the high load cells? if its rich throughout (not including o2 feedback zones) i would say its worth investigating the return fuel lines.

other than that its double checking what the input sensors are saying, like the temperature sensors, double check they are good by swapping with known working items.

what about the condition of the electrical contacts for the injectors? if i remeber correctly, the s14 fires injector by not grounding instead of by sending a high signal. so double check the wireing to ground the injectors as if this signal doesnt get through clearly then they will be live and there you go, overfuelling.

It wont be the knock sensor as the tuner does a straight copy of fuel maps.