ECMlink 2G What is your vacuum with GSC S1 268 cams?

[DSM B]

Hey guys, I am trying to improve my idle and I can only get the vacuum to 16.4 in hg at best. I do have 268 (GSC S1) cams and I am wondering what vacuum people with those cams have.

When I watch my wideband, it does seem to bounce around mainly lean and the idle is not rough, but it is not smooth either. There seems to be small idle misfire stumbling's. I am suspecting a vacuum leak and I have done several BLT's that have not pointed toward any vacuum leaks, but I could be mistaken.

I am set up with speed density and I still want to rule out any vacuum leaks, so I am wondering what people with the same cams have.

My fuel trims and Airflowperrev seem to be inline, yet my car still runs lean according to the wideband. I do have adjustable cam gears, I did adjust them to improve the idle vacuum and it did not improve, 16.4 seems to be the best I can do.

I am wondering if my throttle body has a small leak, I did replace the throttle shaft seals and I do have FIAV bypass plate installed. I don't know if I have small leak somewhere in there maybe that I BLT just isn't picking up.

Attached is a log for review, I am open to any advice or feedback. My injectors are Bosch 1600 HiZ injectors and I do have dyno acr 2 on my ignition.

Thanks

 

[jdxnc]

16.4 is about correct for a 268 duration cam, + or - a little depending on a lot of variables in the motor, for example; compression, age, your altitude etc.

12 is about all I can get with my S2s

 

[USMCGSX]

Mine went from -19 hg with stock cams at 750 rmp, to -15 hg at 850 rpm idle with S1 cams.
Also went +1mm on valves when the cams went in, not sure how much of a factor that might be but probably worth mentioning.

 

[motomattx]

Vacuum numbers are really worthless in this discussion, every engine will be different based on a million different things, your vacuum is not what makes a bad or good idle unless you have a pretty significant vacuum leak and with your numbers you dont and on speed density it shouldn't make a real difference anyway, I would look elsewhere for your issues, maybe you just are not being realistic about your idle quality with bigger cams. Your afr is going to bounce around with big cams, there is valve overlap that will cause that at idle, you can pretty much ignore your afr's at idle with big cams anyway.

 

[Canadian_CD9A]

Cam gears are a major variable on vacuum, too. If it bothers you, tune the overlap to where you want it.

 

[motomattx]

Cam gears are a major variable on vacuum, too. If it bothers you, tune the overlap to where you want it.

Yeah, I agree one hundred percent on that, I was going to mention that also but then he did say that he had adjusted the cams for better idle already.

 

[DSM B]

Ok great, thanks for feedback guys! I have been playing with my tune and think I have it smoothed out as it can be and I am very happy with it. My vacuum settles around 15-16 and that seems to be in line with what you guys have.

Do you guys use idle air clamp with speed density?