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"Surge Performance Chip" ... on 2002 STS yes or no?


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No. Your car does not use a 'chip'; it uses re-programmable memory. This is a snake-oil device designed to replace the air intake temperature sensor with a fixed low value. So instead of being able to properly adjust the fuel air ratio, the engine would instead run more lean than programmed. The claim is that this would then result in some benefit. In my opinion causing the car not to run at the optimal air/fuel ratio is not beneficial.


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It installs in the IAT line. The IAT is the Intake Air Temperature sensor. These are not new and their performance and effects are known. They basically lie to the PCM about the intake air temperature, which causes the mixture to be either leaner (when telling the PCM that the intake air is warmer than it really is) or richer (when telling the PCM tha the intake air is cooler than it is). Leaner is better gas mileage with less performance, richer is more torque and horsepower with less gas mileage. Good idea to control by the drivers taste, huh? -- NOT.

If the "chip" (I use quotes because this "chip" may be analog, or it may be a PIC microcontroller but it basically implements a curve of input vs. output voltage) has an offset from reality that is within tolerances then the engine won't be harmed and the warranty is good.

Here's the rub: if the PCM doesn't have the software sophistication to compensate for this sensor's bias due to the "chip" but does adjust the spark, using the knock sensor, to take advantage of a richer or leaner mixture, then the "chip" will do what the web site says it does -- except that seeing 7% to 10% gains in HP will likely be seen only in primitive systems or in wishful thinking.

In the GM DFI systems, the fuel-to-air ratio is maintained by the PCM using a number of sensors, including intake air temperature, manifold air pressure, exhaust oxygen content, manifold air pressure, mass air flow, coolant temperature, throttle position, vehicle speed, transmission input shaft speed (RPM), and others. The key to keeping the fuel-to-air ratio at target for any given condition is the exhaust oxygen sensor. All the rest are used for maintaining the right fuel-to-air ratio over varying conditions. If the IAT sensor has an offset, the PCM will, over a few minutes, adjust the fuel-to-air ratio appropriately and assign an offset to the readings from the IAT. In plain English, the GM PCM will calibrate out the effect of the "chip" in a few minutes.

If you want a chip to improve performance, Plan A is to tell your dealer that you are primarily interested in performance. They may reprogram your PCM to emphasize performance. It worked for me. Plan B is to work with one of our members here, who has developed a way to reprogram your PCM for performance. I'll leave it to him to step in here. Plan C is to get a new chip to replace one of the chips in your PCM; there are members here who have done that and have sources; again I'll leave them to step in here.

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