As you may know I recently installed a Kenne Bell supercharge on my 2K Navi. Although I wasn’t really looking to get a learning experience out of it I have. I also have a couple of questions regarding the PCM’s operation and was hoping to confirm or refute my understanding.

Under closed loop operation the PCM is receiving data from the oxygen sensors to further ‘trim’ the fuel air mixture in addition to data from IAT, MAF, TPS and whatnot. Under WOT this is not the case. My current understanding is that WOT operation is solely governed by ‘fixed tables’ for fuel delivery and spark advance and this is what the ‘performance chip’ (in my case the KB chip that came with the kit) governs. It essentially replaces the PCM programming but ONLY under WOT operation. Is this correct?

So when I have my vehicle tuned by a professional by having several dyno pulls, they are looking at a number of parameters to determine what the chip’s programming should be? I ask this because for a brief time I ran the setup without the chip. It ran like a raped ape, but I encountered some ping at WOT in the 4700-5250 range. Can I then assume that the knock sensor is not considered while under WOT operation? With the chip in place I don’t have any ping, but the vehicle is noticeably slower. I have captured some runs and have noticed that chipped I have about 3 degrees spark advance and without the chip I have about 15 degrees spark advance. (This certainly would account for the power difference). So my point is, once we get the fuel delivery (pulse width) worked out, is the only other variable timing? And if this is the case I’m guessing that I can’t then rely on the knock sensor to pull out timing as ping is encountered? Of course my desire is to run as much advance as possible but it would appear that I have to settle on the conservative side to insure that I don’t get into pinging in variable circumstances.

My real concern of course is getting this thing tuned out at 30-40 degree air temperatures running right up to the limit of spark knock only to have it pinging like mad on a 90 degree summer day. So, experts am I on the right track in my understanding? Is there any information and/or suggestion you can make?

 

A couple of things..... just because a tune on a supercharged application is making more power doesn't mean its a better tune. Too lean a/f ratios can give more power but you're risking engine damage. Without a chip, your stock computer is going to run it too lean.

The thing you need to do is get it up on a dyno that includes A/F graphs. The chip needs to get the A/F ratio perfect across the RPM range for maximum safe power.

As to the knock sensor... forget about it. In a great many Ford applications the computer doesn't even have it turned on! Your tuner should know the proper advance for the amount of boost you're getting.

Also, a Superchips or Diablo module doesn't tune at WOT. They tune at all throttle positions and RPMs.