Odd AFR problem

[RobH]

Hi guys. I've just made some changes to the cam timing on my Z32 TT, the engine builder had installed the belt wrong! Car was running pretty well all the same.

The car is generally running much better but I thought I'd better recheck the AFR as I'd made such a critical change, I was using a K value of 180 to get 14.7:1 at idle, I've now had to drop this to around 160 to get anywhere near Stoich. I went for quick drive and found some odd readings from the wideband. at idle it was about 13.8:1 and as soon as any load was applied it leaned right off to around 15 or 16:1. Closing the throttle used to give around 28:1 but now is reading anything up to 9:1!

There's obviously a problem somewhere. I'm using an Innovate wideband which was last calibrated about a month ago and hasn't been used since. The only ideas I currently have are recalibrate the wideband and check again, and check the MAF (although the consult readings seem reasonable).

Hope someone can throw me a line..

Cheers
RobH

[Eric]

what (size) injectors ?

rule of thumb is not to tweak K value at idle , as only a very few (z32) binaries will run around stoich at idle.
Most roms will run rich at idle, so if you tweak K @idle to get an afr of 14.7, chances are it will run (very) lean on any off idle situations.

[RobH]

Thanks Eric.

I thought by disabling the O2 sensors and setting the target to 14.7 in the appropriate (idle/closed loop) fuel map cells a good base K value could be set? That's how I've always understood it.

Running Nismo 555cc injectors, latency is set to 850 as it seems to run a bit better than the default 750.

Cheers
RobH