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aint right... Bcar
05-12-2003, 10:44 AM
Ok, so several have taken their cars to the dyno right? I was just looking at a post down a few lines. It shows 270 and 274 rwhp.

Well take a look at that number, something is very wrong. If the car is only putting down 270, that is a 23% Driveline loss? NO FREAKING WAYYYY!!! Id guess in the 11-13% range. I bet my M3 that there is not a 23% driveline loss. No chance, one would loose a little from air flow (ram air) but not more than 5hp, 10hp at most (in a dream)!

One of two things:
1. some M3s are under powered or
2. someone needs to have their dyno calibrated in a bad way.

Just some observations...

-B

sgalaba
05-12-2003, 11:05 AM
The numbers are something like this:

6-Speed loss is 16%
5-Speed loss is 12%

so for our 6-Speed (and the same for the SMG) cars take the RWHP # and multiply it by 1.1905% for crank #, some just use 1.20%.

<br><img src="http://www.sgmotorsports.com/m3e46/images/signature.jpg">

lincoln30
05-12-2003, 11:06 AM
When I use 274 and a 17% drivetrain loss I get 331 (which is damn close to 333 IMHO). 17% is the number most tuners seem to use for BMW.

Ferris
05-12-2003, 11:09 AM

Ferris
05-12-2003, 11:10 AM

sgalaba
05-12-2003, 11:17 AM
The tuners I have spoken with who are the big guys, the ones that are writing the code and have the most dyno time on the E46 M3, say 12% and 16%. The problem that comes up so often is which the correct number to use, it's like do you want to hear the truth or let's use a number that inflates the dyno result numbers.<br><img src="http://www.sgmotorsports.com/m3e46/images/signature.jpg">

Bcar
05-12-2003, 11:26 AM

Bcar
05-12-2003, 11:28 AM
wants to give us the correct numbers its all a guesstimate.
Regardless, 23% is a bit on the high side IMO...

sgalaba
05-12-2003, 11:30 AM
I have even heard that some will use 18% loss. Get hold of JimC and ask him.<br><img src="http://www.sgmotorsports.com/m3e46/images/signature.jpg">

lincoln30
05-12-2003, 11:33 AM
I think your splitting hairs. I've always heard 17% for this car and most people I know who have dyno'ed on a dynojet that is setup properly (not many are) are getting 274-281. I've seen a few higher then 281, but none lower then 274. Even the cars that didn't seem to want to cooperate (cut off at 6500) where pulling 260-265 @ 6500.

Bcar
05-12-2003, 11:35 AM
I believe you, no doubt. But from my experience and from the other engineers I have spoken with, losses that high are not realistic. My largest data point is from GM powertrain, they said typical numbers are around 12% +/- 2%. And these guys know exactly what they are doing. Wonder how they compare to BMWs, Id guess that BMW would have more efficient drivelines, but one never knows...

Dan Law
05-12-2003, 11:41 AM

sgalaba
05-12-2003, 11:41 AM
as I told Bcar, get hold of JimC. I have heard of everything from 10% to as high as 18%. As JimC if he has calculated the drive train loss on the dyno for this car. The other issue at hand is between 16-18% we have so many dyno's reading a little difference between them that too is splitting hairs.<br><img src="http://www.sgmotorsports.com/m3e46/images/signature.jpg">

KJ-TypeR
05-12-2003, 11:41 AM
My old Integra Type-R had 15.4% drivetrain loss. (195HP flywheel, 165HP at the wheels)

The S2000 has 16.7% drivetrain loss (240HP flywheel, 200whp)

The M3 making 270hp would equal 18.9% drivetrain loss (I don't know where you got 23% from).

As you can see, all the cars from my experience don't even come CLOSE to 11-13%. In fact, I think you'd be hard pressed to find cars that actually exhibit that little drivetrain loss on the dyno. Sandbagged cars excluded of course.

sgalaba
05-12-2003, 11:42 AM
<br><img src="http://www.sgmotorsports.com/m3e46/images/signature.jpg">

lincoln30
05-12-2003, 11:43 AM
The Z06 and Camaro SS might have small drivetrain losses in the 12-18% range, but I know for a fact that the full size trucks (with auto trannys) have losses of 25% or more. The 5.3 is rated at 270-285 depending on year and they consistently dyno in the 190 range. That's about 27% on the low side and 30% on the high side.

gregwminmmoregon
05-12-2003, 11:44 AM

theRock
05-12-2003, 11:57 AM
even using 270, your math is way off

333-270= 63
63/333= 19%

Where you're getting 23% is beyond me.
And I've never heard of 11-12% drivetrain loss on any car..that's wishful thinking. 15-20% is about the norm.

Bcar
05-12-2003, 12:12 PM

Bcar
05-12-2003, 12:13 PM

m3guy35
05-12-2003, 01:34 PM
should be able to reduce parasitic losses of hp better than Acura.

Wouldn't you agree?

m3guy35
05-12-2003, 01:36 PM
transmissions usually...not 6 speed.

In addition, some parasitic hp loss occurs due to inexact pulleys and so forth and less hp type cars. I would think BMW engineering should be at the low end of hp loss between the crank and rear wheel.

m3guy35
05-12-2003, 01:40 PM
horsepower with a plus or minus 10 hp error.

I get sick of this back and forth deal between hp at the crank and rear wheel hp.

I remember when the Boss 302 was rated at 290 "net" horsepower. It was rated this way for insurance purposes.

Another way for car manufacturers to mislead people.

Vadim@evosport
05-12-2003, 01:43 PM
eleven stock S54s we have dynoed at our shop, no two are alike. There were couple that were down in low 260s, there were couple that were in high 280s, one at 291. The rest are in mid 270s. They were tested under very similar conditions, weather in Huntington Beach, CA varies very little.

If we assume 15% loss, than 333FwHP should be 333x0.85=283HP. Each car is different, we have seen the same varience on E39M5s, C32 AMGs, Z06s and other cars as well.

Bcar
05-12-2003, 01:47 PM

CBsaksiri
05-12-2003, 04:17 PM
RWD is going to have more parasitic loss than FWD. FWD cars have no driveshaft and associated bearings... the path that the power travels through is much more direct in a FWD or mid-engined car.

as for which company has more efficient cars, i would guess Honda.<br>
<B>CBsaksiri</B> Sunnyvale, CA
<A HREF="http://members.roadfly.org/cbsaksiri"><IMG SRC="http://members.roadfly.org/saksiri99/sig_sm.JPG" border=0></A>

theRock
05-12-2003, 04:20 PM
jeez.

KJ-TypeR
05-12-2003, 04:23 PM

KJ-TypeR
05-12-2003, 04:28 PM
Someone has to start doing it. That manufacturer will look like they have cars with low HP vs. their rivals. Also, 4wd cars always show lower numbers on a dyno (since more wheels are being driven).

Another reason manufacturers don't adopt this is because it would prevent car makers from Sandbagging (saying the car is slower/weaker than it really is) their cars.

The new Dodge Neon SRT-4 has 215hp flywheel and 232hp at the wheels.

Sound impossible? Of course it is. Obviously Dodge is understating the Neon's power so it won't take away sales from it's other cars.

If they had to report WHP, this "lying" would not be possible. =)

CBsaksiri
05-12-2003, 04:58 PM
m3guy was saying BMWs should have lower loss than even the FWD Acura. anyway, i was getting at the Acura vs. BMW thing...

i think we're saying the same thing... the RWD S2000 and BMWs should compare favorably...<br>
<B>CBsaksiri</B> Sunnyvale, CA
<A HREF="http://members.roadfly.org/cbsaksiri"><IMG SRC="http://members.roadfly.org/saksiri99/sig_sm.JPG" border=0></A>

CBsaksiri
05-12-2003, 04:59 PM
m3guy was saying BMWs should have lower loss than even the FWD Acura. anyway, i was getting at the Acura vs. BMW thing...

i think we're saying the same thing... the RWD S2000 and BMWs should compare favorably...<br>
<B>CBsaksiri</B> Sunnyvale, CA
<A HREF="http://members.roadfly.org/cbsaksiri"><IMG SRC="http://members.roadfly.org/saksiri99/sig_sm.JPG" border=0></A>

Bcar
05-12-2003, 05:16 PM


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