Timing & Fuel Trim Running -30 ??? - PeachParts Mercedes-Benz Forum

HDDP · #1 07-03-2007, 02:40 PM

Hey guys I'm not new to the forum, I just read more than post... Until now... I need some professional advice / guidance... I'll be as precise as possible in hopes that the forum guru's can help...

Here's a little back story, I'm road racing a fully gutted / caged '04 Chrysler Crossfire that as you know, has the W112 drivetrain and Bosch Motronic 2.8 computer on the 170 chassis. The engine is basically stock with the exception of a 3" dual CAI and a dual custom exhaust system w/o CATS, but still maintaining the second bank 02 sensors in the pipes. And a (off the shelf) PowerChip Gold 93 ECU remap.

Last weekend I conducted a full scan of the engine perfomance during a testing day at the track and recorded 19 key PID's. Some of the many PID's I scanned were Long Term Fuel Trim (LTFT), Short Term Fuel Trim (STFT) and Timing. The track is in the high desert of Southern California and it was very hot (105).

All of the engine parameters / sensors seem to be WNL (I think) except for the LTFT, STFT and Timing. They are all running in the SERIOUS negatives at idle and throughout the RPM range. I was only able to access bank 3&4 of the fuel trim, does this matter at all ?

The first set of data logs were conducted during 20 minutes of full race conditions at speed. There were 333 different logs calculated and recorded during the first test and 400 during the second test. The MAFS was cleaned prior to testing. I ran with new DENSO Irridium (hot) plugs during the first test, and Champion Copper Top (cold) plugs during the second test. Both tests were run with normal 91 octane pump gas without my normal power additives (KLOTZ COXOC & Propylene Oxide)

Here is what a typical data log looked like during idle:

(TEST 1)
Engine RPM: 677
Vehicle Speed: 0
Intake Pressure: 9.7 inHg
Intake Air Temp: 126f
Engine Coolant Temp: 185f
Calculated Load Value: 18.8%
LTFT Bank 3: -37.5%
LTFT Bank 4: -36.7%
STFT Bank 3: -40.6%
STFT Bank 4: -39.8%
Ignition Timing Advance for Cylinder #1: -25 deg
02 Sensor STFT Bank 2 - Sensor 2: 99.2%
02 Sensor STFT Bank 2 - Sensor 1: -1.6%
02 Sensor STFT Bank 1 - Sensor 2: 99.2%
02 Sensor STFT Bank 1 - Sensor 1: -0.8%
Absolute Throttle position: 2%
Air Flow Rate from MAFS: 0.51 lb/min

And here is a typical data log at speed during race conditions

(TEST 1)
Engine RPM: 4519
Vehicle Speed: 107
Intake Manifold Absolute Pressure: 26.9inHg
Intake Air Temp: 138f
Engine Coolant Temp: 203f
Calculated Load Value: 82.4%
LTFT Bank 3: -34.4%
LTFT Bank 4: -33.6%
STFT Bank 3: -39.8%
STFT Bank 4: -41.4%
Ignition Timing Advance for Cylinder #1: -17.5 deg
02 Sensor STFT Bank 2 - Sensor 2: 99.2%
02 Sensor STFT Bank 2 - Sensor 1: 0.00%
02 Sensor STFT Bank 1 - Sensor 2: 99.2%
02 Sensor STFT Bank 1 - Sensor 1: 0.00%
Absolute Throttle position: 100%
Air Flow Rate from MAFS: 15.81 lb/min

The second test was conducted after swapping the hotter DENSO plugs with colder Champion plugs and yielded similar results as above...

Now to the BIG question... What the heck could be causing the timing / fuel retard ? And how can I fix it without installing a piggyback computer system ?

Thanks in advance for any help...

HDDP · #2 07-05-2007, 04:59 AM

What's up guys ? No answers ? Guesses ?

david s poole · #3 07-05-2007, 11:16 AM

to be able to answer your question i would need to know the computer parameters for the timing.it may have something to do with the lack of backpressure in the exhaust and /or the new chip that you put in the computer.why dont you swap the chips back and run your test again at idle.the chip may be your problem because the live data should only be showing bank 1 and 2 not 3 and 4.this suggests that something with either your code reader or the chip is not right.