Performance Programer 97 ETC??

FYI - the resistor mod won't do anything but screw up your car. Here's why:

The computer needs to know the air temperature to calculate the air density involved with fueling calculations. So, an unsuspecting victim buys this "chip" (resistor), unplugs the air temp sensor, and plugs in the resistor. The computer instantly sees it as 20 degrees F outside. (In reality, it's 70 degrees F) Hmm... okay, denser air needs more fuel.

*PCM pours more fuel in*

Car warms up, and enters closed loop. The O2 sensor starts reading the exhaust, and detects a rich condition. The long term fuel trim starts cutting back on the fuel,

*PCM reduces fuel back to stoichiometric (14.7:1)*

You're now back where you started. If you floor it, it will use the long term fuel trim in it's calculations, and be (hopefully) no different than before you had the "chip" (resistor)

BUT, you really start to play havoc on your engine when it's not 70 degrees outside. Say you're sitting in traffic and now the air is 120 degrees... Now the long term fuel trim has to compensate for this, every time it changes. But it can only change so much, and that doesn't even account for when the computer isn't paying attention to the oxygen sensor (open loop, like during warmup) The air temp sensor was put in place to make changing the fuel trim unnecessary.

In reality, what you would want to do is reprogram the fuel map to a *leaner* condition, and advance the spark tables to make more power. All engines are different, and GM likes to make "safe" power. It's always better to err on the side of rich than lean, so they typically put WOT at 12.5:1 or less. I've seen 11:1 before. Most power naturally aspirated is made at 12.6-13:1. Unfortunately, for the 97, this is not an option. Actually for all cadillacs it's not an option. Proprietary engine management programming and what not.

Hope that helps, :stirpot:

Trench said:

I was just reading the feedback from that seller and there is one remark saying "Awesome power, okay gas mileage, quick shipment, Thanks!"
He bought a resister..errr… “chip”, for an Aurora.
Although I have always disregarded these "chips" there is some info out there stating they do offer some increase in power. Now, if it's good for your catalytic converter is another story.

Click to expand...

Hey Trench - 2 hrs. SW of Chicago... Are you in Bloomington or Peoria? I used to live in Bloomington and I'd go back if I could.

Anyway, as eldorado1 eloquently detailed for us, the resistor basically just sets into motion a series of compensations that ultimately result in little or no benefit to performance. If they dump extra fuel in there, as may happen when intake temperatures are high, that unburned fuel can burn when it comes into contact with the hot catalyst surfaces. That will obviously make the catalytic converter run much, much hotter. They can glow red with the worst problems. The cat will not live long under those circumstances, and all that fuel being burned in the catalyst certainly isn't doing your mileage any good. It's probably detracting from engine performance as well. Try passing a emissions test with one of those in place. Even if they don't test the tailpipe gases, the resulting codes it will likely set won't make Mr. E.P.A. very happy... So in short, it certainly looks like a very bad idea. Thanks to eldorado1 for a great post.