Chevrolet Colorado & GMC Canyon Forum banner
1 - 3 of 3 Posts

·
Registered
Joined
·
20 Posts
What year is your truck and what did you modify on the engine physically?

I have been considering making a thread/asking about this as i've started to play with the vve and the vvt calibration on my 2011 2.9L automatic. I first started with the vvt (after calibrating the MAF map) but that seemed to really screw up the resulting fuel trims I think because of the vve table now being wrong. So now I am slowly fixing up the vve table with the vvt locked out at 0 degree.

On mine I felt 15 or 16 degree (i'm not totally sure what this number means, as there is no clear documentation from hpt, I assume degrees of cam retard?) on the cam felt the fastest above 2500 RPM, but I guess that is really subjective. I think we could use the MAF frequency number plotted over RPM to see what cam angles produce the most air intake registered by the MAF.
 

·
Registered
Joined
·
20 Posts
Which pid are you logging to get torque? Did it seem repeatable to use for comparisons? I am weary of reading into of a lot of the 'calculated' pids but have no real reason to believe it isn't reliable to quantify tuning changes.

I was imagining one could log the MAF frequency in hz on engine RPM vs MAP like so:
Purple Font Violet Rectangle Line

(This was my commute to work this morning with maf only fueling and vvt locked out at 0 degree.) I believe if I made the vvt static to 15 to 20 degrees of retard, the wide open throttle area at the bottom should have a higher frequency at 2500RPM+ due to the engine consuming more air. And similarly I think we could tune more efficiency into the cruise area of the map by doing the opposite; for a given RPMxMAP load point, if we obtain a lower MAF frequency at certain vvt angle, less air and therefore fuel will be consumed at that point. If that makes any sense at all.
 

·
Registered
Joined
·
20 Posts
Ooh another thing I noticed and forgot to mention, my stock calibration sets the VVT to 11 degrees at mid to higher engine loads. At that setting, the scanner shows a bit of knock spark retard (I run 87 octane) at cruise at even low-ish rpm like 1700-2000 on the highway. When the vvt is set to 0 degree over the whole map, I get pretty much NO knock retard under the same conditions. This makes me think the engine is getting more air with the vvt, but we already know the right amount of overlap does that.
 
1 - 3 of 3 Posts
Top