Dyno 3rd or 4th gear?

[Kichigai]

Just wondering if anyone can fill me in on why certain garages dyno in different gears?

Does it give a different output reading? If so, what are the reasons for running in different gears?

Just plain curious.

[skyzerr33]

from what i gather yes

auto should be run in 3rd manual in 4th as these are the gears with the 1:1 gear ratio. using other gears with give incorrect readings either high or low depending on the gear used

[GTS-t VSPEC]

Skyzerr is right, 4th gear for manuals, I think third gear will give higher readings, hence why some places do it, so you think they did a good job. As long as the place you go to is consistant then it doesn't really matter.

See'ya:burnout:

[Leewah]

It is true that manuals should be dynoed in 4th but due to the 200km/h speed limits on most DynoDynamics dynos, a lot of runs are done in 3rd as 4th is past 200 km/h.

4th is a 1:1 ratio and therefore a true power figure at the wheels assuming that the dyno is calibrated correctly in the first place.

[BOOSTMEISTER]

AMAZING....No conflicting opinions, and I too agree. Most of our cars will not still be making HP at 200km/h. Mine didn't and it put out 217rwkw at its most tuned stage. My mate has a rb20det in his silvia and he makes over 250rwkw and his max power is still below 200 so this shouldn't be a issue. Make sure it is done in 4th though, once you start to make around the 200rwkw mark you may actually find that you get a higher figure in 4th than 2nd/3rd anyway due to less stress on the motor.

[Cubes]

3rd gear made less power than 4th gear at RPM's DD Dyno.

But that may be due to the AF's being perfect in 4th (12:1) where as in 3rd it was still a little rich. There was a 4rwkw difference.

Fuel Pressure Reg Bleeder does strange things.

[Guest KILLER-T]

What about doing a tune up in 3rd gear i had a fuel reg fitted today and the guy did the dyno in 3rd gear i dint notice untill i got home and looked at the print out i made peak power @ 120kmh so it must of been in 3rd on the dyno.Now i am worried about flooring it in 4th because of the extra load on the engine it hasnt been tested on the dyno in 4th

[Ustasa]

The power output of the engine is the same regardless whether the car is dynoed in 3rd, 4th or even 5th gear. But in lower gears the higher wheel speed and distortion in the tyre/dyno roller interface shows up as a higher power figure at the wheels NOT the engine.

Hope that helps.

[2rismo]

Hope that helps.

And that's a mechanical engineer 0wning us all !!

ROFL

[Cubes]

For example.

Dyno a Turbo car in first gear... You will get a low power reading then second a little higher then 3rd higher again. 4th well sometimes higher.

Now do it to a V8 1st same power reading, second power reading is the same as 1st. All the gears are the same on a NA car.

The reason why a turbo car will make more power in higher gears is the turbo has time and is able to flow as much air as it possibly can. More exhaust flow for a longer period of time.

Its not just about psi.

I can make full boost on 1/4 throttle but the car wont accelerate as quick as when I'm on full boost with full throttle. Hence more air is being supplied.

ROLF.. Hope that helps....

[Guest KILLER-T]

Yep Joel thats what i thaught because my car only boosted to 1.08 bar every other dyno i have had the boost is 1.20-1.25 bar

[Ustasa]

Joel,

If the steady state operating conditions were the same in 1st and 4th gears your engine would be making the same power. Were the same ramp rates and inertia figures dialled in for the power runs in different gears? The ramp rate changes the time your engine is held under load when run on the dyno which can affect the power developed by the engine.

Different gearing will never change the power an engine makes but it will change the torque that is fed through the drivetrain. In the end it’s what gets to the ground that is important, as long as the tune is done in the right speed range to suit the dyno and rpm of the car.

[Cubes]

I think most dyno runs leave the ramp rates etc no matter what gear they run it in this is why the power figures vary in different gears?!?

[noone]

Was looking at my graph and am sure it to is i 3rd but in kph rather than rpm I am running 18's but overall diameter is very close to stock from memory Have searched but cant seem to find what 3rd gear ratio actually is to convert to RPM can anyone help.

Damn this is an old thread just realised

[STATUS]

What about doing a tune up in 3rd gear i had a fuel reg fitted today and the guy did the dyno in 3rd gear i dint notice untill i got home and looked at the print out i made peak power @ 120kmh so it must of been in 3rd on the dyno.Now i am worried about flooring it in 4th because of the extra load on the engine it hasnt been tested on the dyno in 4th

Yeah no good, alot of places dont road test after tunes either which is an issue. A dyno cannot 100% replicate driving conditions (rememmber wind resistance etc) and it is possible for a well tuned car on a dyno to ping its self to destruction higher up in the gears.

[CEF11E]

Yeah no good, alot of places dont road test after tunes either which is an issue. A dyno cannot 100% replicate driving conditions (rememmber wind resistance etc) and it is possible for a well tuned car on a dyno to ping its self to destruction higher up in the gears.

I can testify to that :0

my cefiro made 210rwkw and no detonation all was good but up hills in 3rd and 4th it would ping as soon as it hit peak torque. even after the timing was backed off 2 deg i was still getting some knock reading.

road tune is essential after dynoage

[Dale FZ1]

road tune is essential after dynoage

Definitely agree on this one. I had the same experience and found the ignition map needed some of the advance taken out to tame down any knock readings coming up.