Joined: 26 Jul 2016
|Posted: Tue May 15, 2018 12:13 pm Post subject:
|WOT acceleration problems
M50B25TU, 240/240 cams, open loop, rest stock.
Is there somewhere positive deltaRPM fuel correction factor?
AFR is very good when engine is under max load and constant rpm, but rapid acceleration at high load goes very lean. Error is multiplied as higher is rate of acceleration.
As an example: constant rpm wot is 12.8-13 AFR, but 5 seconds wot dyno run from 3000 to 7000rpm AFR is 14-15.
ECU does individual load/rpm knock correction map for each cylinder. It's stored somewhere in SRAM.
I did some tests.
- Set knock control load threshold to "0", so knock control is always "armed".
- RPM 3000, about mid load.
- Set whole 1. cylinder knock threshold table to "0"
- 1. cylinder timing is retarded by "fake knock". 1. cylinder misfiring.
- Set knock control load threshold to 254 and then let engine idle.
- Engine is idling smooth, no misfiring.
- Set all knock settings to "factory values"
- Then, when engine reaches about 3000rpm at mid load, and knock control load threshold is reached, 1. cylinder will misfiring by retarded ignition.
There is no knock, so, timing starts to rise to no-knock values. In few seconds there is no misfiring, and advance is back in normal value.
- ECU will remember, if knock was detected in some conditions. Timing will not return, if conditions are not similar as knock has occured.
- IMO, In tuning, knock control load threshold is good to set to 254, or disable knock control by something way else. But knock must be controlled by other ways.