Just finished breaking in my new setup (see relevant mod list below). Did a light pull in 3rd gear and experienced a bizarre and dangerous issue.

As per the attached log, there was a sudden drop in injector pulse width. On the following line, the load took a sudden drop resulting in high ignition timing. Also went extremely lean, probably from the drop in IPW. The throttle position shows a decrease, although I never lifted off the throttle.

Any ideas what is causing this issue? How should I diagnose? I'd like to get a better log and include airflow, but I'm afraid of engine damage. The car drives fine off-boost. I experienced this issue on 3 out of 4 pulls.

Things to note:
- Tephra V7, load limit set to 500
- E85 fuel, conservative tune based on old stock turbo set up
- Fuel trims are under 5%
- Poor resolution on log because of large number of variables being logged (unfortunately, was not logging airflow)

Relevant mod list:
- FP Black BB turbo
- Stock MAF with FP intake pipe (trimmed back about 2" for clearance with ACD reservoir)
- Apexi intake filter
- FIC Bluemax 1450 injectors
- Buschur double pumper
- GSC S2 274 cams

 

After some thought, I believe the more logical explanation is that the injector pulse width drop is actually occurring as a result of the load drop and for some reason it just doesn't match up in the log. It seems that a full fuel cut would drop the pulse width to zero, where as this is just a decrease. The ECU is probably just looking at the fuel map for the decreased load value and seeing a leaner fuel value, and more advanced ignition timing value on the timing map.

If this is the case, the question remains; why is the load dropping? Without the airflow measurement, I can only guess that the problem is with the MAF. However, the throttle position drop is very odd.

Is it possible that load is not simply a function of airflow but also includes throttle position in the calculation? If so, the root cause of my problem could be a faulty TPS sensor.

Thoughts?

 

*** Problem solved ***

It seems that the problem was caused by the intake filter hitting the ACD reservoir under acceleration. I attached the mounting bracket to the Apexi MAF adapter to restrict movement, and this problem went away. The movement of the MAF pipe and / or impact of the filter on the ACD reservoir must have been causing incorrect airflow measurements. Just did 3 pulls and didn't have any issues.