Missfire analysis

[retro-ed]

Hi Guys,

I am experiencing a bit of a misfire on my engine. It feels like when you hit fuel cut or boost cut but I was not aware there was such a thing in the std S14a setup. I am using DET3 map sensor as load, not afm (this problem also happened with afm).

Here is the log....



Here is the fuel map with the AFR logs overlaid...



As you can see, I have had to add a lot of fuel in the midrange to bring the AFR down.. Could this be causing the standard ECU to activate some sort of fuel cut?

I would appreciate peoples opinions..

Thanks

[oliverm29]

Maybe unrelated (to the det3) ignition problem have you checked the plugs? dodgy coil pack?

The map looks like its fueling as much if not more in the mid range than the top end, If your're having to make big adjustments to the fuel table to get it something like its maybe the standard ecu self learning and trying to adapt, I'm using the det3 and found disconnecting the lambda and knock sensors solved many problems

[retro-ed]

Maybe unrelated (to the det3) ignition problem have you checked the plugs? dodgy coil pack?

The map looks like its fueling as much if not more in the mid range than the top end, If your're having to make big adjustments to the fuel table to get it something like its maybe the standard ecu self learning and trying to adapt, I'm using the det3 and found disconnecting the lambda and knock sensors solved many problems

It feels very much like a fuel cut when cars have overboost protection. Ignition side all seems good.

For quick test I reverted back to an earlier map which doe not have such large numbers in midrange. Mixture was obviously lean but missfire / cut was not there. This is what was making me think I had reached the limits of the OEM map table. I will try bigger injectors this week so that the gain on the oem table is much less and see what that does.

At first I didnt think that I would have any issues with adding enough fuel in the midrange but the turbo I have fitted spools so much better than the std unit so I am guessing that is the cause

I will try with OEM Lambda dissconected and try that

[oliverm29]

Part of the problem is working out what the standard ecu is doing, there's going to be lots and lots of maps in there and they're all linked together so making any adjustments is going to have a knock on effect with everything else. The fuel maps inside the ecu are going to be directly linked to the ignition maps so if the ecu see's a big airflow (which is what your feeding it) its probably going to be retarding the ignition timing- maybe too much which is causing the rough running in the mid range

A different turbo shouldn't make much difference, I'd try resetting the ecu, zero'ing the maps in the det3 and seeing how it runs without the lambda - it'll probably run rich but you should be able to correct it with small adjustments in the fuel table, and it should stop the ecu adjusting its own closed and open loop maps (because it can't get any feedback from the lambda)

[Karel]

I think its something like overboost protection of stock ecu. If the ammount of meassured air is too high it cuts.... and your DET3 simulates AFM signal and gives it to the ecu....