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11-26-2012, 06:15 AM | #1 |
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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, 08:36 AM | #2 |
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11-26-2012, 09:22 AM | #3 | |
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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, 10:00 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, 10:18 AM | #5 | |
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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, 10:46 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, 11:13 AM | #7 | |
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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, 11:22 AM | #9 | |
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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, 11:28 AM | #10 | |
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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, 02:52 AM | #11 | |
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Found some interesting info in M3 section:
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12-02-2012, 01:46 PM | #12 | |
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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, 05:29 AM | #13 |
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"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, 06:17 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, 03:18 AM | #15 | |
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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, 03:58 AM | #16 | |
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12-04-2012, 05:17 AM | #17 |
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12-04-2012, 08:51 AM | #18 |
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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, 09:09 AM | #19 | |
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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, 09:28 AM | #20 | |
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http://www.goodspeedperformance.com/dyno.php |
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12-04-2012, 09:52 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 09:58 AM.. |
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12-04-2012, 11:32 AM | #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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