Hey guys, I had a question... If you are running 4.10's in your car, but the ECU is still set to recognize 3.42's, is there any untapped potential horsepower due to the difference in revs or is it going to be a minimal difference?

Also, can anyone calculate the difference in power digit-wise?

P.S- Also burned out my wiring harness to my knock sensors, which was not throwing a code at the time of tune.

 

lol nobody?

 

Your speedo is going to be off. The gear swap is probably eating 10-15rwhp.

Is that enough to throw off your tune? Not really.

 

So with the 4.10's in the car and the ECU being tuned for 3.42's, 410/405 is more closely to about 425/410.

As for the knock sensor harness being burned out while the car was tuned (not throwing a code at the time), is it possible that my timing is going to be advanced now that it was replaced?

 

Why would a gear change change the output of the motor?

 

Not necessarily the output of it, but rather the accuracy of the dyno results.

 

I wouldn't really think of it that way. With that mindset you can say the car with 2.73 gears you car would put down 500rwhp...

Gearing has nothing to do with the tune or any of its parameters, so the only thing that is problematic with you not updating the tune is going to be the speedometer being off.

 

Lower gears have more parasitic loss. It doesn't change the output of the motor - but shows up on the dyno. However, it doesn't show up at the track as a lower gear will help move the car with more mechanical advantage.

 

I think what the OP is asking is if you do a pull with the tune unchanged for the new gears then do a pull with the tune changed for the new gears will it show up in different dyno numbers for the 2 pulls. And for that the answer is no.

 

A dyno algorithm determines horsepower based on speed and acceleration rate, if my speedo is off due to a difference in gear ratio versus what my ECU is programmed, how are my numbers going to be accurate?

 

The dyno doesn't care what your speedometer is showing. It has it's own speedometer on the rollers. And if it is a dynojet it is far from accurate anyways. Real dynos measure actual torque and calculate HP based on the math formula tq x rpm/5252 = hp. Dynojets measure rate of acceleration of 2 fixed weight rollers, and backwards calculate HP and tq with a fudge factor.

 

a gear change without a tune will have more issues than just the speedo off , all your mph thresholds for up and downshifts will be off - its worth getting it tuned.

 

Look at his sig. It is a Manual trans.

 

guess I missed that lol