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      11-26-2012, 07:15 AM   #1
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Cool 352 BHP out of stock?

So I've put my cars on dyno few weeks ago and was really surprised to see 352BHP (357PS) out of stock M Coupe. At least as far as I know there was no tune done before.


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      11-26-2012, 09:36 AM   #2
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When are people going to learn that chassi dynos do not give accurate readings are simply tuning tools or somewhat useful for measuring power differences.
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      11-26-2012, 10:22 AM   #3
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Quote:
Originally Posted by O-cha View Post
When are people going to learn that chassi dynos do not give accurate readings are simply tuning tools or somewhat useful for measuring power differences.
+1

Dyno numbers mean nothing by themselves. The whole point is to set a baseline and observe the delta as a result of mods.
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      11-26-2012, 11:00 AM   #4
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i never could figure out how a chassis dyno measuring rwhp can measure bhp when it has no idea what the driveline loss is.

i agree with the above... without a pre-tune dyno, this unfortunately doesn't give us much information other than the rev curve. any chance that can be provided as well?
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      11-26-2012, 11:18 AM   #5
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Quote:
Originally Posted by v3.2mc View Post
i never could figure out how a chassis dyno measuring rwhp can measure bhp when it has no idea what the driveline loss is.

i agree with the above... without a pre-tune dyno, this unfortunately doesn't give us much information other than the rev curve. any chance that can be provided as well?
Ehm I thought the driveline lost is defined by BMW.
Oh and the car is stock, it was only a dyno measuring, so basicly this is the pre-tune dyno.
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      11-26-2012, 11:46 AM   #6
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i've not seen anthing from BMW about what the driveline loss is. to my knowledge, every model is different. and if you change anything... trans, diff, fluid weight, or even putting on aftermarket bearings or seals (obviously negligible), it will change the loss due to changing friction variables.

any chance you could post a link to this info?
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      11-26-2012, 12:13 PM   #7
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Quote:
Originally Posted by O-cha View Post
When are people going to learn that chassi dynos do not give accurate readings are simply tuning tools or somewhat useful for measuring power differences.

exactly what i was thinking.....

Dyno figures are pretty inaccurate at the best of times, unless you take the motor out and do it on a engine dyno..... Then were talking ;-)
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      11-26-2012, 12:15 PM   #8
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I noticed the graph stated "PS" as well, instead of BHP? I know those are slightly different as well.
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      11-26-2012, 12:22 PM   #9
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Quote:
Originally Posted by mfanatic325 View Post
I noticed the graph stated "PS" as well, instead of BHP? I know those are slightly different as well.
True, PS was some weird 0.98 or something of BHP, because of inaccuracy back in the days in Germany. I'll update that.

Never worked with dynos, so no idea about the accuracy, all I could find was info that this MAHA LPS 3000 should be +-1% accurate, but that's most likely some marketing blabla.

Maybe someone with dyno knowledge could chime in and spread some wisdom.
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      11-26-2012, 12:28 PM   #10
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Quote:
Originally Posted by mfanatic325 View Post
I noticed the graph stated "PS" as well, instead of BHP? I know those are slightly different as well.
the chart below the graph lists both.

the 357 PS is hp(metric)
the 352 PS is hp(international)

basically, 357 hp(m) = 352 hp(i)

edit: i had them flipped. fixed now. online conversion here.
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      11-28-2012, 03:52 AM   #11
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Found some interesting info in M3 section:
Quote:
Originally Posted by Sal@Evolve View Post
There are two things we are looking at here;
1) Comparison of cars on different dyno's
2) Drivetrain loss calculation and what approximate flywheel calculation the S65 is making

So let's go over these briefly for now and any questions that follow we can then start looking at in some more depth.

1) Comparison of the same car (E92 M3) on the same and different dyno

I have found in the BMW community that not many dyno operators (and there are a few!) talk about this subject too much. I have spoken to dyno operators across the world and some have said they feel nervous about this subject because if people knew everything then people would not take them more seriously.
We think the opposite and have posted on many forums about the dyno. We believe people should understand. It is quite clear that this lack of understanding has created confusion in the community and worse still some people going to the point of saying dyno’s are useless.

I would hope that people would take our points seriously as we do dyno a very large number of M power cars all year round for quite some years now.

First thing first. We know that weather conditions have an effect on engine power. Humidity levels, barometric pressure and temperature all individually effect engine power.
The majority of dyno’s have SAE correction factors built into them along with a weather station which measures humidity, pressure and temperature. The values are input into a forumula and the end result is the correction factor.
The correction factor corrects for the atmospheric condition under which the engine is being tested under.
The problem we have found (as many other dyno operators have found) is that these correction factors assume all engines will respond in exactly the same way as each other given a change of any of the above mentioned variables in any permutation or combination.
This is not true unfortunately and this is part of the reason why we get varying numbers especially under extreme changes in weather condition where the correction factor will also change massively.

Here is an example of an S62B50 V8 engine (BMW E39 M5) tested on our dyno dynamics machine.
Exactly the same tyres and fuel:



Notice how the graph shapes are almost identical! Small differences are there because slightly different ignition targets are reached due to the ECU actually taking some of the atmospheric conditions into account but not as much as the dyno is assuming! The dyno SAE correction factor is simply ‘over compensating’ because what it thinks should happen simply is not happening with this engine. What the dyno software should be doing is showing the car to make the same power on these two very different days..... that's what correction factors are meant to do! This is not an isolated example. This is however an extreme example but you get the point.
We have also seen different brand of tyres, final drive ratio’s and of course strap tension cause skewing of the dyno graphs.

What also can make a big difference is the gear used and I know for a fact that some dyno operators prefer to use 4th and some prefer 5th. You simply cannot compare.

Fuel of course plays a major role but this we all know and don’t really need to discuss here as we are talking about the comparison of cars with the only variable being the atmospheric conditions (hence the correction factor) and dyno operator.

There are further variables at play too which I have discussed very recently which are the type of cooling fan used, allowing ignition targets to be met and generally allowing the inlet, oil and coolant temperatures to reach an equilibrium. We will discuss this in more detail.

Just from the above brief information I am sure you can deduce that the same car can read so so differently on even the same brand of dyno on different days! Even the very same dyno can have varying figures on the same car because someone decided to change from normal street tyres to semi slick. Yes gentlemen, this also makes a difference.

Luckily for many, we do have some excellent dyno operators around who are also lucky to have very consistent weather conditions.
Typically the effects of using different types of tyre, final drive and the correction factors playing a role will skew the dyno graph. The shape of the graph will not however change and more emphasis needs to be put on studying the shape.

What also needs more emphasis is the logging of ignition advance and AFR. Thanks to certain members of the community this has been highlighted but only a handful of people look at this information correctly.

The dyno should be used in a more detailed way and is really for comparisons of upgrades and more importantly from our point of view as a development and test rig.


2) Drivetrain loss calculation and what approximate flywheel calculation the S65 is making

There are many dyno brands which attempt to calculate the flywheel power of an engine from the rear wheel horsepower made.
Two such dyno’s are the Dyno Dynamics and MAHA.
Dyno Dynamics uses a simply percentage addition to the RWHP which is set by the shootout mode selected.
For the S65 it’s shoot 8 (meaning 8 Cyl NA engine).
The MAHA uses a completely different method where the RWHP along with the coast down frictional losses. These are are combined to work out the flywheel power.

Why am I talking about this?

Well, both read fairly close to each other in terms of RWHP and the calculated flywheel calculation. They also both read very close to the stated manufacturer stated power and torque if used correctly.

Let us take some examples from our Dyno Dynamics readings across different BMW models and from there you can make up your own mind if it’s realistic or not.

Average Dyno Dynamics readings on Evolve Dyno for different STOCK BMW models:

BMW E36 M3 3.2 (Euro)
Stated Power – 321PS / 316HP
Average Tested Wheel Result – 250HP
Flywheel Calculation – 310HP

BMW E46 M3 (Euro)
Stated Power – 343PS / 338HP
Average Tested Wheel Result – 265HP
Flywheel Calculation – 330HP

BMW E39 M5
Stated Power – 394HP
Average Tested Wheel Result – 325HP
Flywheel Calculation – 395HP

BMW E60 M5
Stated Power – 507HP
Average Tested Wheel Result – 408HP
Flywheel Calculation – 497HP

BMW E92 M3
Stated Power – 414HP
Average Tested Wheel Result – 335HP
Flywheel Calculation – 410HP

I can post numerous (hundreds for some cars!) dyno graphs of the above cars to confirm all of this.

What’s more interesting is that the dyno graphs related to the above tests show calculated torque figures to be very very close to the stated torque from factory which in my opinion really does suggest that the calculation of around 18-20% drivetrain loss is very very accurate. I have never ever seen anyone look at it from this angle and those of you who are intelligent will agree that if both the flywheel calculated HP and torque are close together then it’s a very good estimate.

Hopefully the above will generate some more questions and we can look at certain areas in more detail.
http://www.m3post.com/forums/showpos...9&postcount=13
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      12-02-2012, 02:46 PM   #12
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Quote:
Originally Posted by SmartBastard View Post
Ehm I thought the driveline lost is defined by BMW.
Oh and the car is stock, it was only a dyno measuring, so basicly this is the pre-tune dyno.
It's not "defined" by anyone, it is simply your particular car.

And I can make a dyno read 500hp for your car if I wanted.

The point is that what you are posting means literally nothing.
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      12-03-2012, 06:29 AM   #13
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Quote:
Originally Posted by O-cha View Post
It's not "defined" by anyone, it is simply your particular car.

And I can make a dyno read 500hp for your car if I wanted.

The point is that what you are posting means literally nothing.
"Defined" was the wrong word here, what I meant was "stated by BMW", but that doesn't matter now anyways since the MAHA LPS3000 calculates the drivetrain loss by it self.
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      12-03-2012, 07:17 AM   #14
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You cannot 'calculate' drivetrain loss.
You can only make an estimate.
What was the power measured at the wheels? (I see a lot of numbers with descriptions all in czech or something).
Only the measurement at the wheels has some meaning although different dyno's give different numbers (also due to different means of measurements). Rwhp is usually within 5-10% accurate.
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      12-04-2012, 04:18 AM   #15
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Quote:
Originally Posted by GuidoK View Post
You cannot 'calculate' drivetrain loss.
You can only make an estimate.
What was the power measured at the wheels? (I see a lot of numbers with descriptions all in czech or something).
Only the measurement at the wheels has some meaning although different dyno's give different numbers (also due to different means of measurements). Rwhp is usually within 5-10% accurate.
It's possible to measure the drivetrain loss, that's exactly what that MAHA LPS3000 is doing. Problem with RWHP is that it depends on the conditions - temperature, pressure, air humidity etc, that's why there's "standard" conditions at which HP are stated. Depending on the actual conditions the dyno compensate for the difference to this standard and calculates what the engine BHP would be. Some dynos are better and some worse at this ofc.

To answer your question the RWHP was 255,8 or 188kW. The measured drivetrain loss was 96HP (metric) or 70kW.
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      12-04-2012, 04:58 AM   #16
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Quote:
Originally Posted by SmartBastard View Post
It's possible to measure the drivetrain loss, that's exactly what that MAHA LPS3000 is doing. Problem with RWHP is that it depends on the conditions - temperature, pressure, air humidity etc, that's why there's "standard" conditions at which HP are stated. Depending on the actual conditions the dyno compensate for the difference to this standard and calculates what the engine BHP would be. Some dynos are better and some worse at this ofc.

To answer your question the RWHP was 255,8 or 188kW. The measured drivetrain loss was 96HP (metric) or 70kW.
What gear were the pulls done in? ~255rwhp baseline seems on the lower side. Average seems to be 270rwhp for S54 motors on both the E46 M3 and the Z4Ms.
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      12-04-2012, 06:17 AM   #17
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Quote:
Originally Posted by mfanatic325 View Post
What gear were the pulls done in? ~255rwhp baseline seems on the lower side. Average seems to be 270rwhp for S54 motors on both the E46 M3 and the Z4Ms.
In fifth.
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      12-04-2012, 09:51 AM   #18
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Quote:
Originally Posted by SmartBastard View Post
It's possible to measure the drivetrain loss,
And how would you do that?
If you don't measure at the crank and at the wheels you don't know the loss.
You cannot mesure the loss with only measuring the power at the wheels.
So its an estimate that 70KW (which is a lot; so much that it would be impossible to touch anything on the drivetrain becouse of the heat)

That's why a lot of tuners (like ESS) use an estimated standard loss value of 0,15 (which is still a lot imho especially with more powerful cars)
Somehow your tuner manages to double that figure.
If you think that figure is correct, than you have a serious drivetrain issue.
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      12-04-2012, 10:09 AM   #19
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Quote:
Originally Posted by GuidoK View Post
If you don't measure at the crank and at the wheels you don't know the loss.
You cannot mesure the loss with only measuring the power at the wheels.
+1

bhp is measured with the engine out of the car on an engine dyno

the only way a chassis dyno is going to calculate bhp is if the tech doing the run knows the manufacturer supplied bhp number before running the test, and then subtracts the measured rwhp from the manufacturer supplied bhp. this would only work if the car is bone stock, and is still ultimately a guess.
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      12-04-2012, 10:28 AM   #20
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Quote:
Originally Posted by GuidoK View Post
And how would you do that?
If you don't measure at the crank and at the wheels you don't know the loss.
You cannot mesure the loss with only measuring the power at the wheels.
So its an estimate that 70KW (which is a lot; so much that it would be impossible to touch anything on the drivetrain becouse of the heat)

That's why a lot of tuners (like ESS) use an estimated standard loss value of 0,15 (which is still a lot imho especially with more powerful cars)
Somehow your tuner manages to double that figure.
If you think that figure is correct, than you have a serious drivetrain issue.
"This dyno measures drivetrain loss during each run cycle."
http://www.goodspeedperformance.com/dyno.php
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      12-04-2012, 10:52 AM   #21
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yes... well that says it all then... doesn't it.

Some commercial chitchat is the perfect reason not to use your brains.....

Strange that the manufacturer website states something different:

"Projection of engine power according to DIN 70020, EEC 80/1269,ISO 1585,JIS D 1001,SAE J 1349 (optional)"

At least they're a bit more precautious with their statements.

Anyway, the 71kW drivetrain loss seems a bit exaggerated to me.
A lot of small cars don't even produce that amount of power.

Last edited by GuidoK; 12-04-2012 at 10:58 AM.
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      12-04-2012, 12:32 PM   #22
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Yeah in any case, the BHP figure that the dyno is generating vs. the RWHP seems off. It's estimating on the high side for BHP, yet on the low side for RWHP.
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