Driveloss Question

hl0m4n · 03-08-2009, 09:33 PM

what is the drive loss % for 355i auto and manual? so we just multiply this # with dyno # and that gives us crank (engine) correct? thanks guys.

TurboFan · 03-08-2009, 11:42 PM

Sort of. I've seen a bunch of numbers thrown around, I think you can search for them to see.

The important thing to remember is that drive line losses are not linear. If you are at 18% for the MT, and you add 100 hp, you don't necessarily lose 18% of the added power. However, for the sake of most arguments, and the relatively small changes we are usually looking at (no one is doubling the output on a stock tranny), you can assume they are linear, and your equation above would hold.

I think I remember 18% for the MT?

Lotus99 · 03-08-2009, 11:52 PM

You sure it's that high? I thought I've seen stock dynos around 270 WHP, which would suggest 10% if 300 HP is true, and slightly over that, if BMW has in fact under-rated their engine and the true crank HP is more like 310 or so.

TurboFan · 03-08-2009, 11:54 PM

Not sure at all. I've not been able to dyno mine (xi), so I'm not sure at all.

Rotary Rasp · 03-09-2009, 12:08 AM

xi is going to have a higher drive train loss then rwd models.

rlb · 03-09-2009, 12:09 AM

Pretty sure DT loss is 13%(MT) and 15%(AT).

TurboFan · 03-09-2009, 12:10 AM

Quote:

Originally Posted by Rotary Rasp

xi is going to have a higher drive train loss then rwd models.

Yeah I know. Lower power cars can run 15% - 18% on a manual, but I think the BMW may run less.

MrWhite1015 · 03-09-2009, 12:13 AM

i would love to know the loss on a 6MT XI ?

sd390r · 03-09-2009, 01:06 AM

whats up dan

ive heard 6MT rwd is around 12% and 6AT is around 15%

I usually multiply dyno numbers x 1.12 to get the approx crank hp

if you have an xi, thats a whole different story

edo · 03-09-2009, 01:55 AM

Quote:

Originally Posted by Lotus99

You sure it's that high? I thought I've seen stock dynos around 270 WHP, which would suggest 10% if 300 HP is true, and slightly over that, if BMW has in fact under-rated their engine and the true crank HP is more like 310 or so.

Well, I dynoed my 335i MT on a dyno, which shows crank hp. It was 319hp. Another two 335i's MT - 315hp and 340hp (something's "wrong" with the car as he killed me by 4-5 car lengths 30-130mph).

I'd say it's 15-18%.

munters · 03-09-2009, 02:58 AM

No. 12% MT and 15% AT is right

edo · 03-09-2009, 03:20 AM

Quote:

Originally Posted by munters

No. 12% MT and 15% AT is right

In such case my stock 335i puts down 281whp, and acquaintances' of mine - 277 and 299 whp accordingly.

munters · 03-09-2009, 05:48 AM

Yep that sounds about right.

RiXst3r · 03-09-2009, 08:14 AM

Quote:

Originally Posted by munters

No. 12% MT and 15% AT is right

+1

12% MT and 15% AT for the 335i

MrWhite1015 · 03-09-2009, 11:05 AM

what about MT & AWD ?????

munters · 03-09-2009, 11:25 AM

If you see JPsimon and his numbers, he has about 10 hp less then another with the same mods and 2-WD. It's amazing... Not a big different.
But we don't know jet.

MShao825 · 03-09-2009, 11:34 AM

Quote:

Originally Posted by sd390r

whats up dan

ive heard 6MT rwd is around 12% and 6AT is around 15%

I usually multiply dyno numbers x 1.12 to get the approx crank hp

if you have an xi, thats a whole different story

The correct calculation should be your dyno number divided by 0.88 to find crank hp.

Proper Motion LLC · 03-09-2009, 11:46 AM

MT = 16%
AT = 18%

415 HP M3s dyno around 350rwhp. Which would indicate 16% drivetrain loss for the M3. And their is no reason to believe a 335s drivetrain is more efficiant than an M3s

BavarianBullet · 03-09-2009, 12:36 PM

Quote:

Originally Posted by hl0m4n

what is the drive loss % for 355i auto and manual? so we just multiply this # with dyno # and that gives us crank (engine) correct? thanks guys.

Be very careful in trying to account for drivetrain loss. As others have stated, it is not linear and there are a ton of variables from tire pressure to trans oil temps etc that will throw it off a lot. Rumors of AWD having a significantly higher drivetrain loss vs RWD are typically exaggerated IMO.

Tobias1980 · 03-09-2009, 12:43 PM

This is the best data i have seen on drivetrain loss: http://www.dinancars.com/assets/File...A%20EDITED.pdf

See the end of the sheet where loss is given per RPM and more or less linear between 8,5% (2500 RPM) to 13,5% (7000 RPM) I don't know if this is a manual or auto.

03-08-2009, 09:33 PM	#1
hl0m4n Major General 2158 Rep 5,623 Posts Drives: BMW Join Date: Nov 2006 Location: NY iTrader: (58)	Driveloss Question what is the drive loss % for 355i auto and manual? so we just multiply this # with dyno # and that gives us crank (engine) correct? thanks guys. __________________ Cars: 07 335i ► 08 328i ► 11 328xi ► 13 M3 ► 17 M4 ► 14 M6
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03-08-2009, 11:42 PM	#2
TurboFan Ski bum 317 Rep 6,198 Posts Drives: sideways Join Date: Aug 2007 Location: Knee deep in the pow iTrader: (8)	Sort of. I've seen a bunch of numbers thrown around, I think you can search for them to see. The important thing to remember is that drive line losses are not linear. If you are at 18% for the MT, and you add 100 hp, you don't necessarily lose 18% of the added power. However, for the sake of most arguments, and the relatively small changes we are usually looking at (no one is doubling the output on a stock tranny), you can assume they are linear, and your equation above would hold. I think I remember 18% for the MT? __________________ 1999 e46 328i Ti Silver / Black[retired] 2007 e90 335xi Jet Black / Black[retired] 2011 e70 X5 35d Vermillion Red / Cinnamon 2011 e92 M3 LeMans / Fox Red extended
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03-08-2009, 11:52 PM	#3
Lotus99 Colonel 628 Rep 2,808 Posts Drives: 19 M2C & 18 X3 M40i Join Date: Jul 2007 Location: Canada iTrader: (1)	You sure it's that high? I thought I've seen stock dynos around 270 WHP, which would suggest 10% if 300 HP is true, and slightly over that, if BMW has in fact under-rated their engine and the true crank HP is more like 310 or so.
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03-08-2009, 11:54 PM	#4
TurboFan Ski bum 317 Rep 6,198 Posts Drives: sideways Join Date: Aug 2007 Location: Knee deep in the pow iTrader: (8)	Not sure at all. I've not been able to dyno mine (xi), so I'm not sure at all. __________________ 1999 e46 328i Ti Silver / Black[retired] 2007 e90 335xi Jet Black / Black[retired] 2011 e70 X5 35d Vermillion Red / Cinnamon 2011 e92 M3 LeMans / Fox Red extended
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03-09-2009, 12:08 AM	#5
Rotary Rasp Lieutenant Colonel 241 Rep 1,857 Posts Drives: 2009 E92 335i 6MT Join Date: Aug 2008 Location: SoCal - Torrance iTrader: (6)	xi is going to have a higher drive train loss then rwd models.
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03-09-2009, 12:09 AM	#6
rlb Private First Class 5 Rep 117 Posts Drives: 335i, 300ZX Join Date: Feb 2007 Location: Northern NJ iTrader: (0)	Pretty sure DT loss is 13%(MT) and 15%(AT).
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03-09-2009, 12:13 AM	#8
MrWhite1015 Major General 166 Rep 6,020 Posts Drives: MINIVAN Join Date: Aug 2008 Location: Westchester NY iTrader: (21) Garage List 2008 335Xi Coupe [0.00]	i would love to know the loss on a 6MT XI ? __________________
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03-09-2009, 01:06 AM	#9
sd390r Lieutenant Colonel 61 Rep 1,654 Posts Drives: AW M3 Join Date: Aug 2008 Location: North Jersey iTrader: (9) Garage List 2008 E90 335i [0.00]	whats up dan ive heard 6MT rwd is around 12% and 6AT is around 15% I usually multiply dyno numbers x 1.12 to get the approx crank hp if you have an xi, thats a whole different story __________________ 2008 E90 M3 - Sold 2006 Evo IX SE - Sold 2008 E90 335i - Sold
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03-09-2009, 02:58 AM	#11
munters Captain 11 Rep 677 Posts Drives: E91 335XI AT Dakota Black M Join Date: Jun 2007 Location: Switzerland iTrader: (0)	No. 12% MT and 15% AT is right __________________ 59 Corvette, 72 240Z, 73 Espada, ZXR
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03-09-2009, 05:48 AM	#13
munters Captain 11 Rep 677 Posts Drives: E91 335XI AT Dakota Black M Join Date: Jun 2007 Location: Switzerland iTrader: (0)	Yep that sounds about right. __________________ 59 Corvette, 72 240Z, 73 Espada, ZXR
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03-09-2009, 11:05 AM	#15
MrWhite1015 Major General 166 Rep 6,020 Posts Drives: MINIVAN Join Date: Aug 2008 Location: Westchester NY iTrader: (21) Garage List 2008 335Xi Coupe [0.00]	what about MT & AWD ????? __________________
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03-09-2009, 11:25 AM	#16
munters Captain 11 Rep 677 Posts Drives: E91 335XI AT Dakota Black M Join Date: Jun 2007 Location: Switzerland iTrader: (0)	If you see JPsimon and his numbers, he has about 10 hp less then another with the same mods and 2-WD. It's amazing... Not a big different. But we don't know jet. __________________ 59 Corvette, 72 240Z, 73 Espada, ZXR
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03-09-2009, 11:46 AM	#18
Proper Motion LLC Custom Powder Coater 147 Rep 2,784 Posts Drives: White 335i Sedan Join Date: Dec 2008 Location: Orange County CA iTrader: (2)	MT = 16% AT = 18% 415 HP M3s dyno around 350rwhp. Which would indicate 16% drivetrain loss for the M3. And their is no reason to believe a 335s drivetrain is more efficiant than an M3s __________________ www.propermotion714.com
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03-09-2009, 12:43 PM	#20
Tobias1980 Read the manual please, just do it before asking! 11 Rep 397 Posts Drives: F31 328i, F55 Cooper Join Date: Jan 2008 Location: Sweden iTrader: (0)	This is the best data i have seen on drivetrain loss: http://www.dinancars.com/assets/File...A%20EDITED.pdf See the end of the sheet where loss is given per RPM and more or less linear between 8,5% (2500 RPM) to 13,5% (7000 RPM) I don't know if this is a manual or auto.
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