LIL EVOL

iTrader: (14)

You can see the mods in my sig. My idle A/F surges from 14.5 to 17.0 sometimes at idle and then will occasionally dip to 11.5 and comeback. Vaccum is around 12-13 and idle is around 950. Cruising AF is 14.5 and WOT it is 11.5 at 21psi on 91 Octane with zero knock.

Is it the Cosworths (stock valvetrain with stock rev limiter set) or my PTE 880 Injectors?

Is an 880 injector too much on stock ecu? I can only flash tune since there isn't a dyno closer than 5hrs. Injector duty cycle is 67%.

Lastly, any idea what what help this issue the most? 720-780cc Injectors or S1 Cams since this is an occasional problem with Cossies?

Like I said NO KNOCK. All you knowledgeable tuners please chime in. I never had this problem with the HKS cams but swapped to Cossies/50-trim/880s at once. I'm really leaning torwards the injectors.

Evo8Emperor

iTrader: (12)

Maybe try posting in the Ecu Flash area. This one is way out of my area. Even if i did suggest it would probably only be scaling i would suggest which you may or have done.

LIL EVOL

iTrader: (14)

BUMP anyone?

Ted B

iTrader: (6)

The most common cause of a surging idle is a vacuum leak.

LIL EVOL

iTrader: (14)

Then why does my boost hold so tight? And cruising A/F 14.5 and holding and WOT 11.5 and holding?

Ted B

iTrader: (6)

Because the type of air leak that can cause idle issues is not necessarily severe enough to cause issues during other modes of operation. Even if you had a boost leak, you wouldn't necessarily observe a decrease in pressure, although you would experience a decrease in turbo efficiency.

This is where pressure testing the entire intake becomes valuable. You would be surprised at the number of persons here who are running around with vacuum and boost leaks and are unaware of it.

Mad_SB

iTrader: (8)

TedB is correct. Check the vacume lines on the egr valve. Also, how do the fuel trims look at idle? It is possible the trims are hunting bad. In general, you can bump the idle setting up a tad and add a degree or two of timing in the idle areas of the maps to get a little stronger idle.

Also, injector latency setting have a larger affect at idle than injector size scaling. Under load the opposite is true (under load injector size scaleing has more affect than injector latency) so you may need to work on the injector latency and size scale.

If the trims build up positive or negative during cruise but then correct and go te other way after the car sits and idles for a bit you will need to re visit your injector size scale and injector latency values until you find the happy medium.