jaredfigdor

Hello. I have a 1993 turbo miata running megsquirt pnp. The car will start from a cold start and idle at what it should. When I start driving it, the afr's are good. It will be at around 11.5 under boost and in the 14's while not in boost. However, when I have been driving the car for around 30 minutes, the afr's will start getting messed up. Under boost it is between 14 and 15 which is obviously not good and my idle will start to climb into the 16's and keep going up. Sometimes the car even fully leans out then dies. Im not sure what would cause this. Something is happening when the engine is hot and I've been driving it for a bit. Im not sure what. Let me know if you have any insight on this issue. Thanks!

Onyxyth

iTrader: (2)

Where is your IAT located?
Is MAT correction / air density pulling fuel?

Post your tune and logs please.

jaredfigdor

The IAT is about 6 inches before the throttle body.

I don't have a log but I will get one. In the meantime here is my tune. Thanks for the help.

stefanst

iTrader: (1)

I think Onyxyth nailed it. You seem to be using the stock MAT correction table which is waaaaay too aggressive.

This is what I'm using.

DNMakinson

iTrader: (3)

MAT Air Density Correction should be 100% at the MAT where you most often tune your fuel tables. I set 70* to 100% as that is a MAT I see often, either early AM in summer, or afternoon in winter. That way MAT correction does not get in your way when you are establishing your VE table.

Then, create the correction curve at some nominal cruise power level as ambient temperature changes. Using the same, nominal power location then allows MAT to be the main variable you are tuning at that time.

That will get you from 40 - 100* between winter and summer, depending on your location. Then you can extrapolate above if need be, as stefanst like likely did (I doubt he ever saw 248* MAT).

Good practice says make 70* and up 100%, and then tune it last, after you get the VE table sorted out.

See the pattern? When possible, address one variable at a time, else you will chase your tail.