Hello,

To find out if im right or the other guy is. Here is a poll!

I say a dyno pull should be in fourth gear! Because its closer to the 1:1 gear ratio!

The other say we should dyno in 3rd gear! For whatever reasons!

Who is right?!

 

Use fourth.

 

Fourth.
EVIL

 

fourth

 

you forgot to add 1 more choice on your poll...doesn't matter...

4th because it's the closest one to a 1:1 gear ratio but if you compare dynos, there's not much of a difference in the output....

 

Correct. Not much difference at all. (Maybe 1 or 2 hp gain in 4th gear)

 

The one time I dynoed my car I did it in 3rd, I wish I had new that forth gave you more realistic #'s because of the 1:1 gear ratio.

 

i got all my work done in AREA51, and i think they always use 3rd gear.

 

Yep, for the exact reason that you stated.

 

3rd is the correct way to dyno a R with stock gears. Anyone who knows their dyno's will agree unless they use a different dyno system. IE: mustang dyno, dynapak, etc... New dynojet's (248's) are the best way to go for dynoing. Oh yeah they also have a rpm signal tap with will calibrate itself for a 1:1 gear ratio. So it really doesn't matter the gear. However on some cars (mostly boosted ones) dyno'ing in a higher gear will give higher numbers since the speeds will be higher and generating more boost, etc...
Really though it doesn't matter because a dyno is really used to determine if the car is running correctly and correctly tuned by looking the at the dyno graph curve, not just the peak power reading.

 

3rd here. No difference between 3rd and 4th for my car. The reason I choose 3rd is that I spend most of my time in a 1/4 mile in 3rd gear...


Jason

 

I would rather see my car dyno at 3rd than 4th. As long as the dyno number is consistence and I gain power after the dyno session, I would be happy. Who care what is the exact number is.

 

3rd.

The dyno knows actual wheel speed and RPM, so gearing doesn't matter. It has to calculate actual torque at the crank anyways (minus drivetrain losses).

No reason to put extra strain on the motor in 4th unless your car is so insanely fast that you get better resolution dynoing in 4th gear.

 

Yeah, I'd vote for a "Doesn't Matter" choice. Runs in 3rd and 4th gear on a Dynojet. Very close curves.




[Modified by SurferX, 2:28 AM 7/20/2002]

 

Yeah, tosoe are fairly close to identical...

 

Exactly on newer dynojets, they auto adjust the gear ratio from reading the tire speed and rpm/ignition pulse.
However like I said on boosted cars it does make a difference. Why? The faster the engine is spinning can cause more boost, etc... However also by dynoing in a higher gear you start to pick up more noise in the tires, etc... which can make the curve appear jaggy.
Here's a dyno I did from a long time ago which shows that difference. Sorry for the poor quality, it was a really old file which has been saved a ton of times and lost its quality. Its a 3rd vs. 4th gear run right after each other.



[Modified by Rboosted717, 10:17 PM 7/29/2002]

 

We have been over this topic.

And i am telling EVERYONE.

It does not matter. NO way.

3,rd 4th, 5th, whatever. 2nd even.

Similar graphs.

YOu dyno a car based on 1 thing:

Which gear is comfortable for the power your putting down.

Guideline:

0-100 WHP use 2nd gear
101-240 WHP use 3rd
241-700 use 4th.

Never had a car over 700, so I don't know.

You get wheelspin trying to dyno turbo cars in the 300's in 3rd.

Also, Like boosted said...if your dyno in 4th gear, the graph is jagged because the dyno has 2x longer to read the pulses.

If your dyno graph is perfectly smooth in 4th gear, with smoothing off, that means your car is tuned pretty damn good.

Have a good one.

Jeff

 

not much of a diff. 3rd is quicker as it doesn't take as long to reach 8,000+rpms

 

not only wheel spin but how fun would it be trying to let off in time when the car you are driving has 500whp and is FI and the tach climbs in the blink of an eye

but at the dyno shop i just went to ... the person dyno's in 4th... so that gets my vote

 

3rd=more runs in the same amount of time. value ownz

 

That is 100% correct!

 

I have to use 5th, cause I make so much power, the dyno wheel is sliping when using 4th gear.

 

I always get a 3rd gear pull and a 4th gear pull to compare them. Generally 3rd gear shows a few more HP and torque for whatever reason stays pretty close, maybe a few Foot lbs more in 3rd...
M

 

I dynoed yesterday.
3rd and 4th gear gave exact same numbers.
Conclusion: it doesn't matter.