Dyno Gear..

GT500R · 01-10-2025, 06:53 PM

Does anyone have a recommendation as to which gear to dyno in? I know 6th is 1:1 and is ideal but I think that will hit the 155mph limiter… anyone?

Also, no quirks on these cars like dyno mode etc. right?

Edit: I think 5th will get me to just under the 150mph mark…

eelnoraa · 01-10-2025, 07:18 PM

I don't think dyno work like that. You don't get to choose because in order to sweep HP/torque reading across RPM, you need to be able pull all the way to redline. So you need a gear allow the car to reach redline. 6th isn't possible. In manual car with 6 speed, it is usually 3rd. For 8 speed auto, probably 4th. This one is my guess only because I haven't done any dyno with auto before.

If we ignore parasitic lost for 1st order analysis, torque reading is where gear matters. Because engine torque = wheel torque (what get measured) / resultant gear ratio. For HP, gear actually doesn't matter much because energy is conserved Power generated by engine = power at wheel. Then people tag on a estimated drive chain lost, add 15-20% to measurement.

crabman · 01-10-2025, 08:33 PM

My experience is that they'll want to go direct, if it can reach redline.

GT500R · 01-10-2025, 08:50 PM

You’re both right, but you want to be as close to 1:1 ratio to get the most accurate hp… so I think 5th will get me closest to 1:1 (even though it’s 1.30) to get me closest to accurate ho while going to redline.

I’m really trying to get secondary downpipes and x pipe to see gains.

01-10-2025, 06:53 PM	#1
GT500R Major 851 Rep 1,278 Posts Drives: BMW X5M Join Date: May 2018 Location: NE iTrader: (0)	Dyno Gear.. Does anyone have a recommendation as to which gear to dyno in? I know 6th is 1:1 and is ideal but I think that will hit the 155mph limiter… anyone? Also, no quirks on these cars like dyno mode etc. right? Edit: I think 5th will get me to just under the 150mph mark… __________________ 25’ X5M Brooklyn Grey Former - X3M Alpine White 10.84@127.43 / +1912 DA NH Dragway
	Appreciate 0 Tweet Quote

01-10-2025, 07:18 PM	#2
eelnoraa Brigadier General 2866 Rep 4,779 Posts Drives: G05 X5 Join Date: May 2022 Location: SF Bay Area CA iTrader: (0)	I don't think dyno work like that. You don't get to choose because in order to sweep HP/torque reading across RPM, you need to be able pull all the way to redline. So you need a gear allow the car to reach redline. 6th isn't possible. In manual car with 6 speed, it is usually 3rd. For 8 speed auto, probably 4th. This one is my guess only because I haven't done any dyno with auto before. If we ignore parasitic lost for 1st order analysis, torque reading is where gear matters. Because engine torque = wheel torque (what get measured) / resultant gear ratio. For HP, gear actually doesn't matter much because energy is conserved Power generated by engine = power at wheel. Then people tag on a estimated drive chain lost, add 15-20% to measurement. __________________ 2022 G05 B58/PHEV + a few very old BMWs
	Appreciate 0 Quote

01-10-2025, 08:33 PM	#3
crabman Major 497 Rep 1,142 Posts Drives: 2024 X5M Join Date: Dec 2011 Location: WA iTrader: (0)	My experience is that they'll want to go direct, if it can reach redline.
	Appreciate 0 Quote

01-10-2025, 08:50 PM	#4
GT500R Major 851 Rep 1,278 Posts Drives: BMW X5M Join Date: May 2018 Location: NE iTrader: (0)	You’re both right, but you want to be as close to 1:1 ratio to get the most accurate hp… so I think 5th will get me closest to 1:1 (even though it’s 1.30) to get me closest to accurate ho while going to redline. I’m really trying to get secondary downpipes and x pipe to see gains. __________________ 25’ X5M Brooklyn Grey Former - X3M Alpine White 10.84@127.43 / +1912 DA NH Dragway Last edited by GT500R; 01-10-2025 at 10:06 PM..
	Appreciate 0 Quote