Variable Cam Position Tables

[David-L]

I'm having some trouble understanding how the variable cam in Gen V V8s is set up. From what is have read in the links below(not sure how reliable), The cam is installed with 0 in the tables (ECM 33103 Intake Cam Position-High Baro) as full advanced and the values in the table are the degrees of retard? Is this the correct understanding? Are the values crank degrees or cam degrees?

My largest point of confusion is where the cam is installed at the factory. I am used to working on Gen 1 & 2 small blocks where the cam is installed with the intake centerline at 106deg. Where is the intake centerline on Gen V engines installed and does that correspond to 0 in the tables or a value in the tables.

https://forum.hptuners.com/showthrea...e-cam-settings
https://www.motortrend.com/how-to/18...n-iv-v-engine/
https://help.summitracing.com/app/an...ming-%28vvt%29
https://www.motortrend.com/how-to/mo...-camshaft/amp/

Cam.PNG

[kevin87turbot]

The number that you see in the table is how many degrees of retard that is commanded. That table shows to have up to 28 degrees of cam retard commanded. It's fairly common to reduce the amount of commanded cam retard at part throttle. However, at WOT, you'll be hard-pressed to beat the OE settings, assuming you still have the OE cam.
When you step up to a larger VVT cam, you'll have to change the WOT settings significantly.

[David-L]

Okay, thank you! Those values sound like a lot of retard for lower RPM and low load. I read somewhere retarding reduces manifold vacuum which can offer a slight benefit on fuel economy, but I wonder how much of a benefit it really is.

Also interesting about the WOT values... mine is a stock cam, but I would expect to see more retard than 6-7deg at higher RPMs under WOT.

[IARLLC]

I think that Kevin is right. From what I have seen, one tuner even found a bit of power on an L92 by reducing the full throttle retard at 5500 1 degree (from 12 to 11). Since 7 on the far right side of the table probably just means that your 5.3 cam (7 degrees advanced when the table reads 0) is finally straight up, my logic tends to think that there is some power to be had up there....but as Kevin wrote, the OE full throttle numbers are hard to beat.

One thing I've done over and over and over on L92, LY6s, and L86s. Since I don't own a dyno, I've made numerous runs, charting all of the data looking for improvements in airflow through the MAF and better ETs. Most of the time I see that the OE is pretty good full throttle.

The majority of the benefit I see on the cam adjustment is medium throttle accel. I try to leave the super-light/light throttle cruise alone so as to keep the mileage benefit of the factory "over-retard" or "EGR retard" but I don't think it helps the fuel mileage when you have to give more and more and more gas with no accel then downshift to get down the road. That is why I suggest gradually reducing the over-retard at all airmass levels beyond cruise. More predictable accel, more enjoyable, less downshifting...