Whp to Bhp ( Drivetrain Loss )

JrStig · 06-08-2021, 12:15 AM

Got my M4 dynoed a few days ago

I got :
545whp and 770Nm

Those figures are to the wheels

Whats the drivetrain % loss for these cars ?

Normal cars are 15% however was told that its lower for our cars since we have CF driveshafts ?

If i were to use 15% loss then that would mean im making around

626bhp
885Nm

However i reckon its lower since our drivetrain loss is much lower than 15%

Any thoughts / input on the % loss ?

Kilabyte · 06-08-2021, 12:29 AM

Who cares about BHP unless you want to brag to a bunch of non car people

What mods do you have?

CanAutM3 · 06-08-2021, 05:21 AM

There is no such thing as standard loss number. Every dyno, install and run will be different depending on test conditions. Chassis dynos are not very accurate at providing absolute numbers to start with. They are useful though at giving an appreciation of the relative gains generated by modifications by doing before and after runs in similar conditions.

amrazM · 06-08-2021, 05:37 AM

its usually 15% for rwd and 20% for 4wd, having a cf drive is a neg difference.

CanAutM3 · 06-08-2021, 05:45 AM

Quote:

Originally Posted by amrazM

its usually 15% for rwd and 20% for 4wd, having a cf drive is a neg difference.

Gxmmtme · 06-08-2021, 08:36 AM

I thought the general thought is modern sporty cars are much more efficient at putting the power down so the loss can be much less than the larger percentages we still use from the 90s and before, and as others have said it can very from car to car to dyno to day. Imo using the largest loss these days is kinda ricer math.

Hopefully you flashed stock did some baseline stuff then flashed your tune so at least you can see your relative gains. Since the final # is meaningful but without knowing the dyno or anything else your torque looks spot on for the tune but the hp seems high so without knowing the dyno/type etc its tough to really tell other than your #s appear to be in the healthy expected range for this motor/mods/tune.

But i am wondering what the question of the day will be tomorrow!

kumkeet · 06-09-2021, 02:50 AM

Quote:

Originally Posted by Kilabyte

Who cares about BHP unless you want to brag to a bunch of non car people

What mods do you have?

So whp is for bragging to a bunch of car people

JrStig · 06-10-2021, 08:20 PM

Quote:

Originally Posted by Gxmmtme

I thought the general thought is modern sporty cars are much more efficient at putting the power down so the loss can be much less than the larger percentages we still use from the 90s and before, and as others have said it can very from car to car to dyno to day. Imo using the largest loss these days is kinda ricer math.

Hopefully you flashed stock did some baseline stuff then flashed your tune so at least you can see your relative gains. Since the final # is meaningful but without knowing the dyno or anything else your torque looks spot on for the tune but the hp seems high so without knowing the dyno/type etc its tough to really tell other than your #s appear to be in the healthy expected range for this motor/mods/tune.

But i am wondering what the question of the day will be tomorrow!

I did do that

So stock was ( with 93 Oct fuel )
405whp
620Nm

Stage 1 was ( no FBO ) ( 93 Oct )
503whp
710Nm

Stage 2 ( FBO + exhaust + custom tune on RaceGas )
545whp
770Nm

CanAutM3 · 06-10-2021, 08:34 PM

Quote:

Originally Posted by RoccoMarcellus

I did do that

So stock was ( with 93 Oct fuel )
405whp
620Nm

Stage 1 was ( no FBO ) ( 93 Oct )
503whp
710Nm

Stage 2 ( FBO + exhaust + custom tune on RaceGas )
545whp
770Nm

Here you go, you have the numbers that matter:

Stage-1: +24% in power, +15% in torque
Stage-2: +35% in power, +24% in torque

No need for fictive drivetrain loss numbers pulled out of nowhere

rmanm4 · 06-10-2021, 08:38 PM

Quote:

Originally Posted by RoccoMarcellus

Quote:

Originally Posted by Gxmmtme

I thought the general thought is modern sporty cars are much more efficient at putting the power down so the loss can be much less than the larger percentages we still use from the 90s and before, and as others have said it can very from car to car to dyno to day. Imo using the largest loss these days is kinda ricer math.

Hopefully you flashed stock did some baseline stuff then flashed your tune so at least you can see your relative gains. Since the final # is meaningful but without knowing the dyno or anything else your torque looks spot on for the tune but the hp seems high so without knowing the dyno/type etc its tough to really tell other than your #s appear to be in the healthy expected range for this motor/mods/tune.

But i am wondering what the question of the day will be tomorrow!

I did do that

So stock was ( with 93 Oct fuel )
405whp
620Nm

Stage 1 was ( no FBO ) ( 93 Oct )
503whp
710Nm

Stage 2 ( FBO + exhaust + custom tune on RaceGas )
545whp
770Nm

You got 405 HP and 457 ft-tq at the wheel on a stock M4????

405HP is about right but the torque seems high for stock.

Generally it's about 450-460 HP and torque at crank which correlates to 400-410 at the wheel for both HP and Tq

JrStig · 06-11-2021, 12:00 AM

Quote:

Originally Posted by rmanm4

Quote:

Originally Posted by RoccoMarcellus

Quote:

Originally Posted by Gxmmtme

I thought the general thought is modern sporty cars are much more efficient at putting the power down so the loss can be much less than the larger percentages we still use from the 90s and before, and as others have said it can very from car to car to dyno to day. Imo using the largest loss these days is kinda ricer math.

Hopefully you flashed stock did some baseline stuff then flashed your tune so at least you can see your relative gains. Since the final # is meaningful but without knowing the dyno or anything else your torque looks spot on for the tune but the hp seems high so without knowing the dyno/type etc its tough to really tell other than your #s appear to be in the healthy expected range for this motor/mods/tune.

But i am wondering what the question of the day will be tomorrow!

I did do that

So stock was ( with 93 Oct fuel )
405whp
620Nm

Stage 1 was ( no FBO ) ( 93 Oct )
503whp
710Nm

Stage 2 ( FBO + exhaust + custom tune on RaceGas )
545whp
770Nm

You got 405 HP and 457 ft-tq at the wheel on a stock M4????

405HP is about right but the torque seems high for stock.

Generally it's about 450-460 HP and torque at crank which correlates to 400-410 at the wheel for both HP and Tq

Yeappp , my buddies got their cars dynoed at the same place as me , they got around 430whp and 590Nm

I know my torque is a little high for stock. Surprised me too

Kilabyte · 06-11-2021, 12:31 AM

Quote:

Originally Posted by kumkeet

So whp is for bragging to a bunch of car people

WHP is knowing what the upgrades I installed added to the baseline, but ok.

06-08-2021, 12:15 AM	#1
JrStig Private 14 Rep 61 Posts Drives: F82 BMW M4 Join Date: May 2021 Location: Singapore iTrader: (0)	Whp to Bhp ( Drivetrain Loss ) Got my M4 dynoed a few days ago I got : 545whp and 770Nm Those figures are to the wheels Whats the drivetrain % loss for these cars ? Normal cars are 15% however was told that its lower for our cars since we have CF driveshafts ? If i were to use 15% loss then that would mean im making around 626bhp 885Nm However i reckon its lower since our drivetrain loss is much lower than 15% Any thoughts / input on the % loss ?
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06-08-2021, 12:29 AM	#2
Kilabyte I'm Batman! 3948 Rep 1,477 Posts Drives: Mineral White M3 6MT Join Date: Jun 2019 Location: Massachusetts iTrader: (1)	Who cares about BHP unless you want to brag to a bunch of non car people What mods do you have? __________________ S55, 2JZ, M48.00
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06-08-2021, 05:21 AM	#3
CanAutM3 General 21117 Rep 20,741 Posts Drives: 2021 911 turbo Join Date: Jan 2012 Location: Montreal iTrader: (1) Garage List 2022 Audi RS6 [10.00] 2021 Porsche 911 turbo [10.00]	There is no such thing as standard loss number. Every dyno, install and run will be different depending on test conditions. Chassis dynos are not very accurate at providing absolute numbers to start with. They are useful though at giving an appreciation of the relative gains generated by modifications by doing before and after runs in similar conditions. __________________ Porsche 911 turbo 2021 992 GT Silver Previous cars: M4cs 2019 F82 Limerock Grey / M4 2015 F82 Silverstone / M3 2008 E92 Silverstone / M3 2002 E46 Carbon Black
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06-08-2021, 05:37 AM	#4
amrazM mTekMods 2142 Rep 2,901 Posts Drives: like a granny. Join Date: Jan 2010 Location: Manhatan iTrader: (1)	its usually 15% for rwd and 20% for 4wd, having a cf drive is a neg difference. __________________ 2011 Frozen Black/Fox Red E90 M3 650+WHP G-Power Supercharged First DCT to Manual Conversion Worldwide KW CS, BBS RI-A, BW Headers, Snow 2.5
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06-08-2021, 08:36 AM	#6
Gxmmtme New Member 26 Rep 22 Posts Drives: Car Join Date: Aug 2014 Location: Wisconsin iTrader: (1)	I thought the general thought is modern sporty cars are much more efficient at putting the power down so the loss can be much less than the larger percentages we still use from the 90s and before, and as others have said it can very from car to car to dyno to day. Imo using the largest loss these days is kinda ricer math. Hopefully you flashed stock did some baseline stuff then flashed your tune so at least you can see your relative gains. Since the final # is meaningful but without knowing the dyno or anything else your torque looks spot on for the tune but the hp seems high so without knowing the dyno/type etc its tough to really tell other than your #s appear to be in the healthy expected range for this motor/mods/tune. But i am wondering what the question of the day will be tomorrow!
	Appreciate 1 TideMD291.50 Quote