Aftermarket Cams

Any tuning suggestions for improving how the engine runs at low load / idle with aftermarket cams? I'm running GSC S1 cams. During warmup enrichment and idle at 1500 RPM it purrs. Once it reaches operating temp and idle drops to 1000 RPM the engine runs rough. I'm running the same amount of ignition timing and AVCS as before. I'm going to add a few degrees of ignition timing and drop the AVCS to zero and see where that gets me. Any input is appreciated

Hmm crickets so far. Well here's what I'm trying:

Rescaled DBW throttle plate position to run a minimum of 3% at 0 accelerator pedal angle.

Increased base idle timing by 2 degrees

Dropped AVCS to 1 degree at idle RPM and low load.

Didn't flash these changes yet, planning on that tomorrow.

Try richening up the idle with the closed loop compensation tables. Maybe target 14-14.2 and see if that helps.

I wouldn't try to tune your idle until you've resolved the AVCS malfunction. I have seen cars idle very poorly due to cam position sensor problems.

Most of the time the AVCS wont move much at idle due to the loweroil pressure. To make it run smooth down low, you must up idle speed and there are certain idle airflow parameters that will prevent low rpm dip, etc inherent with a high flow cam / low airflow (erratic vacuum) condition.

And of course make sure you have a good set of injectors with proper scaling

Yup ID1000's scaled properly.

I started using the idle air flow / stability definitions for ECUFlash and it's helping. Now, if I can just get to the bottom of why the passenger side cam sensor is reading 54 degrees advance most of the time at idle. It read 0-1 like it should on one occasion since doing the new build.

New sensor did not fix the problem then?

Appears not. It was good for part of one run cycle but now it's just staying at 53-54. Someone suggested checking the oil control valve solenoids and seeing if they are stuck.

Well it can't hurt to check, or swap side-to-side, but IIRC the mechanism cannot physically reach 53-54 degrees.

Well it can't hurt to check, or swap side-to-side, but IIRC the mechanism cannot physically reach 53-54 degrees.

 

Yeah on the USDM cars my understanding is the sprocket at most can reach 25-30 degrees on our cars.

That seems about right. Next time I have a junk sprocket I will measure just to be sure.

 

This leads me back to thinking the waveform that the ecu is seeing is incorrect. Whether it is the grooves in the cam, or another signal interfering/superimposing with the cam signal...

I agree. There's no tone ring right? The cam position sensor just reads the grooves that are in the camshaft? I may have to take a closer look at the cam grooves.

Correct.

I just wanted to post an update that once I got the OCVs replaced for the AVCS, the car is idling great with just an idle airflow adjustment for the cams. Idles at stoich no problem.