Quote:
Originally Posted by trukk  Guys, if the PCM automagically completely compensated for this, then why would anyone ever need to get a tune? It can only do so much.
-Chris |
To answer this question: GM programs predetermined values for A/F ratios in that the vehicle must abide by. As a perfect example, when we've taken the STS-Vs in for tuning, the PCM is, from the
factory, programmed to a target a/f ratio of 10.5:1. This means the PCM is constantly trying to achieve 10.5:1 a/f ratios regardless of the amount of air you introduce. It doesn't matter if you have a cold air intake or not, the vehicle's computer is STILL trying to produce that air/fuel ratio.
Now things 'might' be different on your CTS-V, Chris, but this is not a CTS-V, it's an STS-V and this vehicle has different parameters set for it. Number one, being a supercharged vehicle, the a/f ratios are typically run a lot richer than your CTS-V, unless you added a supercharger. Ideal a/f ratios that produce the most power reliably for the STS-V is around 11.7:1. A naturally aspirated motor can be run a lot leaner without worry.
Getting back to the first paragraph, if the STS-V is set to target a 10.5:1 a/f ratio and we tune the vehicle to instead target 11.7:1, of course we're going to get an increase in power and torque. Is it worth tuning? You bet! Ask any of the STS-V owners if they feel a noticeable difference after a performance tune or ECU box install. I hope this clarifies things a bit for you.