vtraudt

We have been tuning this AMB for a while, but now seem to run against a wall: starting at 3000 rpm, we are getting timing pull on cyl 1 (earlier also cyl 2).
Swapping coils, injectors, new plugs, colder plugs: no change.

Compression test (2x) values:
Cyl 1: 140, 150
Cyl 2: 120, 130
Cyl 3: 130, 130
Cyl 4: 150, 150

Only running 240 g/sec (N75 at 70% duty cycle) (similar car tuned running 280 g/sec, not done tuning yet) with large turbo, high flow mani, DP, IC upgrade, water/meth (1 nozzle at TB, 1 in inlet pipe 12" before TB), 550cc injectors, etc. Boost kept at or under 22 psi (from 3k rpm on).

Every measurable parameter shows normal.
Even calculated (model is wrong on such modified engines) is low at this rpm.
What knock voltage might tell the ECU to pull timing? They are low at 3k, but later climb with higher RPM. Aside from knock voltage, other thresholds?

What can cause timing pull at such low RPM?
Since ECU does the pull, MUST be a measurable parameter that leads the ECU to pull timing (otherwise, ECU would not 'see' or 'know' of the condition).

x19

Hi, do you have a misfiring or timing problem or ? and do you have a chip in ECM and any code(s) on Instrument Panel or?
Swapping coil means misfiring I think. Compression seems OKay and like to know what engine story, includes fuel pressure etc it's might be helping us.

If you have a chip in ECM, try to see what happen after switch to OEM one. x19

vtraudt

Custom tune. No codes. Increasing timing or boost just creates more timing pull by the ECU.

- injector duty cyclle no issue (550cc Bosch EV14).
- wastegate N75 duty no issue (under 70%)
- IAT no issue (even at end of log run at 7.2k rpm only 110 deg F in 90 deg weather (#7 DevilsOwn nozzle 12" before TB; #3 nozzle at TB)
- EGT no issue (even so the values calculated by the model (no sensors) are off (math does not know or can account for high flow manifold, no cats, water/meth, etc.), about 200 degree higher than actually measured EGT
- knock voltage low at low rpm (obviously raising with higher rpm)