I was out playing with the new race car's tune the other day. Since I have a skunk2 intake manifold, I expected some wonky vvt requirements. I wasn't wrong, but while working through the couple of logs I took, I noticed something odd. The car actually makes (slight) positive manifold pressure at some points, and about 90 kpa at others. Is it faulty logic to use MAP readings to tune VVT?

 

Map readings: definitely not the way.
Proper way is on a dyno.

 

Is there something wrong with established values on stock cams?

 

this is if you're bored and chasing that last 1-2tq.

 

I'd be highly suspect of anything over 100-103. 105.8 seems like either a blip, or a bad sensor, or bad calibration, or all three.

Get on a dyno. Decrease all cells by 5*, if anything improves, keep going, if not, start upping everything by 2*. Once certain RPM ranges stop showing gains, leave them and continue increasing the rest of the cells. VVT has a limit, so pay attention to actual intake cam timing, because at a certain point you'll just be throwing duty cycle in the wind.

I'd honestly run a conservative base VVT and ignition table and not bother with anything beyond fueling until you visit a dyno.

 

It all goes out the window with different intake manifolds and some headers.

It's possible my source is noise, but with the skunk there are really only a couple of places I can put it. The vacuum source is the analogue to where the stock manifold fuel pressure barb is. I'll hit the dyno, but it is much more difficult to separate the noise from real delta when tuning n/a cars through VD runs.

 

You'll soon come to realize how impossible it is to squeeze 1-2hp out of a n/a bp using vd. (most can't even do it properly in the most controlled load bearing dyno environment, actually). with turbo cars ~5hp variances are no biggie since you're picking up gobs of power. with n/a the 5hp variances make your 1hp gains basically invisible

 

Good thing I am already at my goal then!