Weird VCT issue.

Helping a buddy with his boosted coyote.

From 4900-5300 it drops from 100% optimum power mapped point, to 60% of it.

However it stays on VCT SCHEDULE MODE (optimum power) throughout the pull.

Fueling is perfect. No drop in spark. No throttle closing.

This is an aluminator with boss springs. I think it might be back pressure related due to the springs and the point at which it happens

Any other ideas? I do have the intake cam moving quite a bit in that area, someone made reference to the VCT feed forward tables, but I am not sure in which manner to adjust them.

Edit

It's something with scanner. If you follow the cam angles it should follow OP commanded. Mine does. It used to report 100% weight to op and now it weights the angle to the mp closest to the actual cam degrees.

I've got the trick flow valve springs on my twin turbo coyote and I too have seen this. It is most definitely a scanner issue as Matt outlined. I can see nothing that indicates the vct system is having any issue getting to the commanded vct angles even with the 210lbs springs I've got.

Also settings that would command 100% op and I have logs to verify this now have the mapped points shifting weight around. I'm certain if I could load that tune I'd now see moving mapped points as opposed to a solid 100% op.

Does spark follow what it's reporting?

My spark and cams follow OP. They do not follow what's reported.

I've wondered about this also based on logs I have.

Quote:

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Originally Posted by schaid

I've got the trick flow valve springs on my twin turbo coyote and I too have seen this. It is most definitely a scanner issue as Matt outlined. I can see nothing that indicates the vct system is having any issue getting to the commanded vct angles even with the 210lbs springs I've got.

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Good to know since that's what he plans on using for valve springs.


Unfortunately I was using his computer which is not setup properly or atleast how I have mine setup. Hopefully this weekend I will get a chance to log cam angles against commanded.

I did notice at a glance the MAF airflow also oscillates during that period of 49-5300. But I guess that kind of makes sense, since it thinks the cams are doing crazy things.

I will say I cannot "feel" this happening, pulls great. So probably right something in the scanner.

Would need to see tune and logs to make a better guess.

If your MAF is oscillating either your airflow actually is, your sensor is dirty, or possibly failing. With Frequency related sensors or equipment in general they usually show just spots in the frequency range that degrade first before totally failing. The ECU could definitely pick this up and compensate for it by falling out of OP mode. If it gets worst or was worst it may even throw a MIL.

is this oscillation extremely fast(hundreds of seconds or less between peaks) or pretty slow(tenths of seconds or more between peaks)?

I asked about this awhile back and never got a solid answer. On mine It seems like wherever the VCT angle is it will use the MP weight closest to those values regardless of if its in OP or not. In OP mode though it does seem to target the OP VCT targets, its just as it moves it sometimes can cross through a normal MP table. My spark seems to follow the MP weights though.

The digital maf is super sensitive. Any sort of delamination of the air or turbulence in the pipe will cause minor fluctuations in the signal.

Looks to be a scanner issue as stated prior.

Cam angles follow commanded even when it falls out of 100% optimum power.

Thanks guys.