3rd or 4th gear for Dyno run

WTH · 09-23-2011, 09:58 AM

Going to get my car on a dynojet in the next couple days and was wondering if anyone could tell me whether I should have the pulls done in 3rd or 4th gear in a N54 335i with 6spd MT?

Rotorocious · 09-23-2011, 10:00 AM

4th

bye

Bleep · 09-23-2011, 10:57 AM

If I recall correctly it doesn't matter what gear you do the dyno in, the dyno will self correct to measure the correct engine torque numbers.

I presume most dyno operators run in 3rd gear to limit how long the pull will take (lack of airflow considerations) and to limit the speeds you'll hit. If you're doing a pull in 5th gear to 140mph and something messes up that can't be good. 4th is a good compromise too. 1st and 2nd are probably too short to get any decent data points.

tscdennab · 09-23-2011, 11:09 AM

Quote:

Originally Posted by Railgun

For ANY transmission, it's the gear that gives you 1:1, which is 5th in this case.

The 1:1 is 4th not 5th.

Papajim · 09-23-2011, 11:14 AM

Quote:

Originally Posted by tscdennab

The 1:1 is 4th not 5th.

Stop writing advices if you just think but not really know something...

BMW 335i MT

Gear Type 6 Speed Manual

Final Drive 3.08:1

1st Gear Ratio 4.055:1
2nd Gear Ratio 2.396:1
3rd Gear Ratio 1.582:1
4th Gear Ratio 1.192:1
5th Gear Ratio 1:1
6th Gear Ratio 0.872:1

For more realistic results go for the 5th on the dyno...

Rotary Rasp · 09-23-2011, 12:08 PM

Most people on here dyno in 4th, however I agree that it should be done with the gear closest to 1:1 (usually one down from the highest on manual transmissions). The problem with 5th gear is that it takes forever and the car will start to heat soak. All dyno software take gear ratios into account so the difference should be minimal between 4th and 5th.

AU335i · 09-23-2011, 12:36 PM

thanks for asking this question as I was wondering this as well.

I just recently got my car dyno'd and I was a bit skeptical of the results. The tuner dyno'd in 3rd gear, which he says was becuz it would cut down on heatsoak (makes sense) and that the power difference was very minimal. he did a 3rd gear pull and 4th gear pull while stock and they were very close.

was he right about the differences being minimal?

09-23-2011, 09:58 AM	#1
WTH Enlisted Member 3 Rep 38 Posts Drives: 2008 335i Sedan Join Date: Aug 2011 Location: Frederick, MD iTrader: (0)	3rd or 4th gear for Dyno run Going to get my car on a dynojet in the next couple days and was wondering if anyone could tell me whether I should have the pulls done in 3rd or 4th gear in a N54 335i with 6spd MT?
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09-23-2011, 10:00 AM	#2
Rotorocious Lieutenant Colonel 106 Rep 1,520 Posts Drives: 335xi Join Date: May 2010 Location: Colorado iTrader: (3)	4th bye
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09-23-2011, 10:57 AM	#3
Bleep First Lieutenant 9 Rep 369 Posts Drives: 3 Join Date: Jan 2011 Location: CT iTrader: (0)	If I recall correctly it doesn't matter what gear you do the dyno in, the dyno will self correct to measure the correct engine torque numbers. I presume most dyno operators run in 3rd gear to limit how long the pull will take (lack of airflow considerations) and to limit the speeds you'll hit. If you're doing a pull in 5th gear to 140mph and something messes up that can't be good. 4th is a good compromise too. 1st and 2nd are probably too short to get any decent data points.
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09-23-2011, 12:08 PM	#6
Rotary Rasp Lieutenant Colonel 242 Rep 1,857 Posts Drives: 2009 E92 335i 6MT Join Date: Aug 2008 Location: SoCal - Torrance iTrader: (6)	Most people on here dyno in 4th, however I agree that it should be done with the gear closest to 1:1 (usually one down from the highest on manual transmissions). The problem with 5th gear is that it takes forever and the car will start to heat soak. All dyno software take gear ratios into account so the difference should be minimal between 4th and 5th. __________________ Last edited by Rotary Rasp; 09-23-2011 at 12:13 PM..
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09-23-2011, 12:36 PM	#7
AU335i Captain 91 Rep 887 Posts Drives: 2008 335i E92 Join Date: Dec 2010 Location: Auburn, AL iTrader: (3)	thanks for asking this question as I was wondering this as well. I just recently got my car dyno'd and I was a bit skeptical of the results. The tuner dyno'd in 3rd gear, which he says was becuz it would cut down on heatsoak (makes sense) and that the power difference was very minimal. he did a 3rd gear pull and 4th gear pull while stock and they were very close. was he right about the differences being minimal?
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