Performance Chips: Pros vs Cons
09-28-2002, 10:39 AM
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Performance Chips: Pros vs Cons
A soon to be 928 owner here, asking what may be a dumb questions, but here it goes:
What are the pros and cons of getting a 928 with performance chips ?
Thanks
Pete
What are the pros and cons of getting a 928 with performance chips ?
Thanks
Pete
09-28-2002, 11:12 AM
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The LH-Jetronic 928s use programmed "maps" in the chips to set the ignition timing and the basic air/fuel ratio. During most operation, the fuel/air ratio is controlled to near 14.7/1 by the ECU based upon the output form the oxygen sensor.
At full throttle, the oxygen sensor is ignored, and the ECU reverts to the programmed maps.
The chips are based upon the vendor's belief that they can make better maps than Porsche.
On most standard automobiles, the maps are programmed with a fairly large safety factor, so that the car will perform adequately and safely at sea level and low temsp, or at high altitudes and high temps.
By reducing these safety factors, you can gain small amounts of preformance.
Porsche appears to have smaller safety factors than most makers, so the performance gains are likely to be smaller. The amount gained seems to vary from model to model, with smaller gains in the higher-performance models.
Bottom line - some minor performance gains in some models, little or none in others. Call the 928 vendor that you use, and then double-check that with the other vendors and make up your own mind.
In general, the 928 is tuned highly enough that it is very difficult to make any easy, cheap power mods.
At full throttle, the oxygen sensor is ignored, and the ECU reverts to the programmed maps.
The chips are based upon the vendor's belief that they can make better maps than Porsche.
On most standard automobiles, the maps are programmed with a fairly large safety factor, so that the car will perform adequately and safely at sea level and low temsp, or at high altitudes and high temps.
By reducing these safety factors, you can gain small amounts of preformance.
Porsche appears to have smaller safety factors than most makers, so the performance gains are likely to be smaller. The amount gained seems to vary from model to model, with smaller gains in the higher-performance models.
Bottom line - some minor performance gains in some models, little or none in others. Call the 928 vendor that you use, and then double-check that with the other vendors and make up your own mind.
In general, the 928 is tuned highly enough that it is very difficult to make any easy, cheap power mods.
