[Sledgehammer70]

So, I know this car has torque all over the place, but it seems the car dyno's the best in 4th gear. Anyone else seeing the same results?

3rd gear hit redline way to quickly and 5th seems very drawn out and the speeds get to high.

[SuperSound]

4th wouldn't be 1:1. 6th would be 1:1 and what you would want to dyno in.

[Boricua]

I just dyno my 8 speed auto car today, was 388 hp and torque was 404. The guy did a second pass and was almost identical. That without the npp exhaust.

[jimmypop13]

Originally Posted by Boricua

I just dyno my 8 speed auto car today, was 388 hp and torque was 404. The guy did a second pass and was almost identical. That without the npp exhaust.

What gear? That was the point of this thread.

Most shops I've seen are dynoing the autos in 5th gear because even though 6th gear is your 1:1, it will get the tires spinning too fast for safety

[drivingagain]

Originally Posted by Boricua

I just dyno my 8 speed auto car today, was 388 hp and torque was 404. The guy did a second pass and was almost identical. That without the npp exhaust.

This seems very low? Anyone else agree? 16% drop in hp.

[Eric SS]

Originally Posted by jimmypop13

What gear? That was the point of this thread.

Most shops I've seen are dynoing the autos in 5th gear because even though 6th gear is your 1:1, it will get the tires spinning too fast for safety

I'm confused by this. If most cars are dynoed in a 1:1 ratio, why would the 6th gen camaro be any different as far as the tires "spinning too fast for safety" goes? Any car in 1:1 will be spinning the tires at the same speed (except for tire height differences). Am I wrong?

[SuperSound]

Originally Posted by Eric SS

I'm confused by this. If most cars are dynoed in a 1:1 ratio, why would the 6th gen camaro be any different as far as the tires "spinning too fast for safety" goes? Any car in 1:1 will be spinning the tires at the same speed (except for tire height differences). Am I wrong?

I know the V6s are hitting the speed limiter on the dyno. So surely it's isn't much faster than what they are attempting.

[6spdhyperblue]

Originally Posted by Eric SS

I'm confused by this. If most cars are dynoed in a 1:1 ratio, why would the 6th gen camaro be any different as far as the tires "spinning too fast for safety" goes? Any car in 1:1 will be spinning the tires at the same speed (except for tire height differences). Am I wrong?

because these new cars have ratios all over the place compared to where they were a few years ago.

gotta start considering the rear end ratio.

IMO the gear selected should be closest to the final ratios we always have been using - 3.23-3.90 final ratio.(tranmission gear ratio X rear ratio)

not using the gear bringing the final ratio in this range skews your results against historical data.

[SuperSound]

Originally Posted by Nicul15

because these new cars have ratios all over the place compared to where they were a few years ago.

gotta start considering the rear end ratio.

IMO the gear selected should be closest to the final ratios we always have been using - 3.23-3.90 final ratio.(tranmission gear ratio X rear ratio)

not using the gear bringing the final ratio in this range skews your results against historical data.

You should read this. Bottom line, the dyno operator should be taking the transmission ratios into effect. But each dyno handles the math differently.

Will different final drive ratios affect the dyno readings?

This one's tricky. First, there are potential discrepancies because different gears have different inertia values, generate more friction, and change the amount of tire slip. Higher numerical gears tend to be more inefficient, so as gear ratios increase numerically, power levels tend to slightly drop, particularly on an inertia dyno. When torque is multiplied by steeper gears, tire slippage also tends to increase.

However, there's another, often overlooked, factor in the brew: rpm and torque are inversely related to calculating horsepower, so changing the rear axle ratio or testing in other than a 1:1 transmission gear seemingly shouldn't change the horsepower numbers. But this doesn't take into consideration the fact that changing gear ratios changes the engine's rate of acceleration. For example: We know that on an engine dyno, if you change a sweep test's acceleration rate from, say, 300 rpm/second to 600 rpm/second, the flywheel power number (bhp) drops due to the faster rate of acceleration. As an engine accelerates at a higher rate, the power required to accelerate the engine increases, and a greater portion is consumed before it gets to the flywheel. Going to numerically higher gear ratios-whether in the trans (testing in a lower gear) or in the rearend-is like increasing the rate of acceleration in a sweep test. Whether this actually changes a given chassis dyno's reported results depends on how the specific dyno manufacturer does its math. For the most consistent results, always test in the same trans gear (generally 1:1) and rebaseline the vehicle after a rear-axle ratio change.

http://www.hotrod.com/how-to/additio...is-dyno-guide/

[6spdhyperblue]

Originally Posted by SuperSound

You should read this. Bottom line, the dyno operator should be taking the transmission ratios into effect. But each dyno handles the math differently.

Will different final drive ratios affect the dyno readings?

This one's tricky. First, there are potential discrepancies because different gears have different inertia values, generate more friction, and change the amount of tire slip. Higher numerical gears tend to be more inefficient, so as gear ratios increase numerically, power levels tend to slightly drop, particularly on an inertia dyno. When torque is multiplied by steeper gears, tire slippage also tends to increase.

However, there's another, often overlooked, factor in the brew: rpm and torque are inversely related to calculating horsepower, so changing the rear axle ratio or testing in other than a 1:1 transmission gear seemingly shouldn't change the horsepower numbers. But this doesn't take into consideration the fact that changing gear ratios changes the engine's rate of acceleration. For example: We know that on an engine dyno, if you change a sweep test's acceleration rate from, say, 300 rpm/second to 600 rpm/second, the flywheel power number (bhp) drops due to the faster rate of acceleration. As an engine accelerates at a higher rate, the power required to accelerate the engine increases, and a greater portion is consumed before it gets to the flywheel. Going to numerically higher gear ratios-whether in the trans (testing in a lower gear) or in the rearend-is like increasing the rate of acceleration in a sweep test. Whether this actually changes a given chassis dyno's reported results depends on how the specific dyno manufacturer does its math. For the most consistent results, always test in the same trans gear (generally 1:1) and rebaseline the vehicle after a rear-axle ratio change.

http://www.hotrod.com/how-to/additio...is-dyno-guide/

good read. im thinking numbers from the A6 and A8s just aren't gonna be that comparable to historical data.

where the 4L60E(3rd gear) used to read way lower than a M6 these newer transmissions are reading a bit higher

[SuperSound]

Originally Posted by Nicul15

good read. im thinking numbers from the A6 and A8s just aren't gonna be that comparable to a 4L60E then

In terms of driveline loss...definitely not. That whole article is a good read for anyone who wants to argue cars are underrated because a car made XXX RWHP on some dyno. There are a lot of factors to contend with.

[Eric SS]

Originally Posted by Nicul15

because these new cars have ratios all over the place compared to where they were a few years ago.

gotta start considering the rear end ratio.

IMO the gear selected should be closest to the final ratios we always have been using - 3.23-3.90 final ratio.(tranmission gear ratio X rear ratio)

not using the gear bringing the final ratio in this range skews your results against historical data.

Duh. Total brain fart on my end forgetting the rear end ratio's of these new autos are super low (high). Thanks.

[Sledgehammer70]

Originally Posted by drivingagain

This seems very low? Anyone else agree? 16% drop in hp.

Depends on the dyno and how they calc the run.

[Sledgehammer70]

Originally Posted by SuperSound

4th wouldn't be 1:1. 6th would be 1:1 and what you would want to dyno in.

I can try it when I head back to BBK. We only tried, 3rd, 4th, and 5th.