Dyno Question

[XR6_661]

Something that has always eluded me...Probably a simple reason

I'll relate it to my own experience.

Now, a while ago I had a dyno run done and they ran the car up to 190ish kph.

Recently, had a dyno run done with my tune and it was only run up to 165ish kph.

Why? Would a car make a higher peak power at a certain speed?

Some people are gonna be like what a dumb question, but the only dumb question is one that didn't get asked.

Cheers

[Bundy]

ok for the 20 or so people that have looked at this thread and thought WTF


I'll answer the dumb question for youse...

Differences can be from and not limited by other errors

operator error, tying down the car to tight, sensor error, placing sensor in the wrong part of the engine bay, different dynos, different modes in dyno run, different gear to do the run in, different air temps and humidity and elevation, different fuel used, clogging up air filter, wrong settings in software etc etc

[nugget378]

Have you changed diff ratio's at all, were the 2 dyno runs done in the same gear?

I always prefer to have rpm up nstead of road speed, just personal preferance..

[BROCKYB8]

Like bundy said there are all different reasons .
Ive done a reading on 3 different dynos on 1 day and come up with 3 differnet results. Not only that but every different thing u do to your car can affect when the power comes

[XR6_661]

I jsut re-read my first post. Was a bit vague and cryptic.

My question is, what is/are the dyno operators reasons for running cars at a different speed on the dyno?

I.e. Why would 1 shop run a car to 190kph while another would only run a car to 165kph.

[nugget378]

Originally Posted by XR6_661

I jsut re-read my first post. Was a bit vague and cryptic.

My question is, what is/are the dyno operators reasons for running cars at a different speed on the dyno?

I.e. Why would 1 shop run a car to 190kph while another would only run a car to 165kph.

From what I have seen, most will stop the run where power starts to drop off..

[Wally]

Maybe the operator didn't care about vehicle speed and just dropped it in a lower gear than the previous test.

[Redrum]

I would say they just did the run in a different gear

[geckoGT]

I would say your car is now hitting peak power a lot earlier in the rev range and therefore there is no point revving the guts out of your car for nothing. Look at both of the graphs and you will find the run was stopped when the power was dropping off.

[prydey]

Originally Posted by Redrum

I would say they just did the run in a different gear

bingo. 190km/h will be your direct drive gear (4th in a manual 5sp, 3rd in 4sp auto) 160km/h would've been the next gear down.

some may argue differently but gearing has no bearing on engine power. you may get slightly different readings running a car in different gears but they will be close enough to the same.

with the 2 different graphs you'll notice peak power is still at the same rpm.

[XR6_661]

Ah yeah, one run was done in 3rd, the other in 4th.

Oh well, thanks guys! That answers my question.

[Werd.]

Originally Posted by XR6_661

Ah yeah, one run was done in 3rd, the other in 4th.

Oh well, thanks guys! That answers my question.