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View Full Version : What is the difference between 3rd & 4th gear DYNO



aRIf
04-13-2007, 05:50 PM
What is the difference betwen them ?

I think they will result different numbers, am I right?

So which one is more accurate ?

Which gear is the best to get best result ?

Thanks

A4Rob
04-13-2007, 05:53 PM
audigeeks says 4th gear. I did mine in 3rd gear along with the rest of the local audi club.

aRIf
04-13-2007, 05:55 PM
4th Gear pull probably less numbers than 3rd, am I right ?

A4Rob
04-13-2007, 06:00 PM
I would assume, but I don't know for sure

Ewok_Fetus
04-13-2007, 06:07 PM
You want to do the dyno in your 1:1 gear which is supposedly 3rd gear for us. I could have sworn it was 4th gear but then again, that is what it was for all my other cars including VW's so I don't see why it is so different...

UCFQuattroguy
04-13-2007, 06:11 PM
IIRC It's 4th gear

mike-2ptzero
04-13-2007, 06:26 PM
Should be done in 3rd gear which happens to be the closest to 1:1. Now if you have a 6spd it would be done in 4th.

If you do a 4th gear dyno pull with a 5spd you will end up with slightly higher readings since there will be more load during the pull and the pull will take a bit longer.

offroader1006
09-03-2007, 03:45 PM
bumping this,

i read that our 4th gear is 1.029:1 and 3rd is 1.429:1

why would we dyno in 3rd?

Ewok_Fetus
09-03-2007, 04:14 PM
That is what I thought... I have never really seen a 5 speed do a run in 3rd... It has always been in 4th...

Ewok_Fetus
09-03-2007, 04:16 PM
Also, here is the FULL info...

Gear Ratios:
Manual (Automatic)
1st - 3.778:1 (3.665:1)
2nd - 2.176:1 (1.999:1)
3rd - 1.429:1 (1.407:1)
4th - 1.029:1 (1.000:1)
5th - 0.838:1 (0.742:1)
Reverse - 3.444:1 (4.096:1)
Final Drive - 3.889:1 (3.730:1)

offroader1006
09-03-2007, 05:39 PM
i guess so many dyno in 3rd to be able to compare data to logged runs like CAPS times.

Ewok_Fetus
09-03-2007, 06:15 PM
But then that would mean that everyone has been throwing out incorrect numbers then huh?!

mike-2ptzero
09-03-2007, 06:30 PM
bumping this,

i read that our 4th gear is 1.029:1 and 3rd is 1.429:1

why would we dyno in 3rd?

Is it a 1:1 ratio of crank shaft to drive shaft?

There are many reasons we dyno in 3rd gear, 1 big reason is MPH and the amount of time it takes to make the pull. Then there is the fact that there are dyno's out there that increase the load on the wheels as the mph increases, this can put way too much load on a car that doesn't make huge power.



But then that would mean that everyone has been throwing out incorrect numbers then huh?!

Yes and No. Running in a different gear isn't the only thing that effects the #'s. Tires play a big part in what the dyno reads out, increasing the tire pressure or running larger tires can give you a slightly higher whp reading. Even sticker tires like my BFG drag radials decrease whp readings because the tires are much softer causing more rolling resistance. 034 tested this on javad's 80 using BFG drag radials and a set of normal street tires, the drag radials gave a 40whp lower reading. Even putting in the wrong weight of the car will give you a incorrect whp readings.

onemoremile
09-03-2007, 10:20 PM
The dyno software can correct for any gear you are in or read in absolute torque. Since gears are torque multipliers the power at the wheels is very different gear to gear. This chart shows power in gear for 3 different final drive ratios. Swapping a1.8t trans out for a 2.8 unit has similar effects to a 6% final drive change. This chart shows why it is also often advantageous to hold a gear past the power peak. That mechanical advantage is just simple math. I run my K04 to the limiter on track and it really is quicker that way. Until the little turbo turns into a heat gun that is.

http://i23.photobucket.com/albums/b397/onemoremile/itrfds.jpg

offroader1006
09-04-2007, 11:25 AM
Is it a 1:1 ratio of crank shaft to drive shaft?

it is unless there is a reduction in the torsen unit.

is there?