Question about wheel dyno curves

dapperdan · 02-07-2013, 08:50 AM

I have a question about the wheel dyno curves I have seen for the M5. They all show a fairly steep rise to about 3000 RPM, and then it flattens out to around 5750 RPM. BMW claims that brake torque is flat from 1500-5750 RPM.

What is going on at the low end? Is that just an artifact of how wheel dyno's work, or does the torque not actually get to flat until 3000 RPM?

B-1Pilot · 02-07-2013, 10:33 AM

I dont know, but look forward to your explanation when you find out. Your M5 blog is awesome, and I just spent a good while reading the whole thing!

dapperdan · 02-07-2013, 12:13 PM

Thanks! It's a little labour of love for me.

GTR-Dad · 02-07-2013, 08:26 PM

Dyno curves are typically performed in a middlish gear with a set rate of rpm increase. Because this process is dynamic, the torque recorded is typically a bit lower than it would be if the engine were fully loaded at a particular rpm. Imagine the engine 'running away' from the resistance required to develop full torque...
This and the fact that the turbos need a minimum rpm to fully 'spool up' contribute to the shape of the torque curve.

dapperdan · 02-08-2013, 12:45 AM

Thanks! Seems reasonable.

B-1Pilot · 08-10-2013, 10:16 AM

found him. Dapperdan, your blog is getting some attention in this thread...

http://f10.m5post.com/forums/showthread.php?t=871586

any chance you might add to it now that you have had the car for a few months, or are you having too much fun with it?

02-07-2013, 08:50 AM	#1
dapperdan New Member 4 Rep 20 Posts Drives: '22 F90 LCI M5 Join Date: Feb 2013 Location: Toronto iTrader: (0)	Question about wheel dyno curves I have a question about the wheel dyno curves I have seen for the M5. They all show a fairly steep rise to about 3000 RPM, and then it flattens out to around 5750 RPM. BMW claims that brake torque is flat from 1500-5750 RPM. What is going on at the low end? Is that just an artifact of how wheel dyno's work, or does the torque not actually get to flat until 3000 RPM? Attached Images __________________ BMW 2022 F90 LCI M5 Competition, Aventurine Red Metallic, Tartufo Extended Merino Leather, Ultimate Package See my M5 Car Blog at http://m5carblog.blogspot.com
	Appreciate 0 Tweet Quote

02-07-2013, 10:33 AM	#2
B-1Pilot Yankee Air Pirate 151 Rep 978 Posts Drives: '14 M5 w/CP Join Date: Aug 2012 Location: In a Hot Place iTrader: (0)	I dont know, but look forward to your explanation when you find out. Your M5 blog is awesome, and I just spent a good while reading the whole thing! __________________ 2020 ///M5 \|\| 2019 540XI \|\| 2014 ///M5 w/CP \|\| My Epic ED trip report\|\| \|\| 2009 BMW R1200RT
	Appreciate 0 Quote

02-07-2013, 12:13 PM	#3
dapperdan New Member 4 Rep 20 Posts Drives: '22 F90 LCI M5 Join Date: Feb 2013 Location: Toronto iTrader: (0)	Thanks! It's a little labour of love for me. __________________ BMW 2022 F90 LCI M5 Competition, Aventurine Red Metallic, Tartufo Extended Merino Leather, Ultimate Package See my M5 Car Blog at http://m5carblog.blogspot.com
	Appreciate 0 Quote

02-07-2013, 08:26 PM	#4
GTR-Dad Driver 8 Rep 210 Posts Drives: 2012 M5 - DCT Join Date: Oct 2007 Location: Beaumont, AB iTrader: (0)	Dyno curves are typically performed in a middlish gear with a set rate of rpm increase. Because this process is dynamic, the torque recorded is typically a bit lower than it would be if the engine were fully loaded at a particular rpm. Imagine the engine 'running away' from the resistance required to develop full torque... This and the fact that the turbos need a minimum rpm to fully 'spool up' contribute to the shape of the torque curve. Last edited by GTR-Dad; 02-09-2013 at 12:11 AM..
	Appreciate 0 Quote

02-08-2013, 12:45 AM	#5
dapperdan New Member 4 Rep 20 Posts Drives: '22 F90 LCI M5 Join Date: Feb 2013 Location: Toronto iTrader: (0)	Thanks! Seems reasonable. __________________ BMW 2022 F90 LCI M5 Competition, Aventurine Red Metallic, Tartufo Extended Merino Leather, Ultimate Package See my M5 Car Blog at http://m5carblog.blogspot.com
	Appreciate 0 Quote

08-10-2013, 10:16 AM	#6
B-1Pilot Yankee Air Pirate 151 Rep 978 Posts Drives: '14 M5 w/CP Join Date: Aug 2012 Location: In a Hot Place iTrader: (0)	found him. Dapperdan, your blog is getting some attention in this thread... http://f10.m5post.com/forums/showthread.php?t=871586 any chance you might add to it now that you have had the car for a few months, or are you having too much fun with it? __________________ 2020 ///M5 \|\| 2019 540XI \|\| 2014 ///M5 w/CP \|\| My Epic ED trip report\|\| \|\| 2009 BMW R1200RT
	Appreciate 0 Quote