07-02-2014, 09:42 AM | #1 |
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M4 dyno run - 500 hp?
Hey guys,
my name's Michael, I live in the motherland of BMW and the automobile in total, Germany. I do not own a M4, nor do I intend to buy one in the near futur. Right now I'm driving Golf R MK7 since 04/16/2014, so the M4 might become some option in maybe 3 to 4 years - especially since the prize tags are pretty much over the top in europe. Anyway, I've found a video on youtube with some M4 on a dyno. The sheet in the end shows ~ 411 hp at the wheels, which would result in something around 500 hp. What do you think about that? As far as I'm concerned, european union only allows a deviation of +/- 5% compared to the standard power - which would be 453 hp at max. Cheers Michael
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07-02-2014, 09:48 AM | #2 |
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If we take standard 14% drive loss into account, 411hp at the wheels = 468 bhp at the crank. Impressive, but not exactly 500.
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07-02-2014, 09:53 AM | #3 |
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@jbraslins
I think you're calculation is wrong. I've heard of 18% drive loss, but ok, lets assume it's only 14%: 411/86*100 = 478 hp at the crank. Nonetheless 468 or 478 hp, I think both is quite unrealistic, isn't it? I don't think the tolerances in the maunfactoring process are that high, not mentioning the legal circumstances.
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07-02-2014, 09:56 AM | #4 |
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You're right. I did the * 1.14 which was wrong. Gobs of power any way you look at it.
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07-02-2014, 10:53 AM | #5 |
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If you search, there are quite a few threads on the topic.
I doubt BMW "underrates" their engines. My guess is that the high numbers we see on dynos have to do with different things. The Sport Auto test on a rather accurate Maha dyno showed 24 more ps than the official rating (465ps vs 431ps). I think that some of it has to with the standards/methodology for official power ratings. The engine might be behaving differently while in steady state and while accelerating. For example, when the engine runs in steady state for the official rating, all the accessories need to be running, but when doing a WOT acceleration run on a dyno, the ECU dissengages the accessories. That can be worth a few ponies. I think that there is also more to it (engine management, turbo characteristics, etc...), I just have not put my finger on it yet. Further, BMW has done efforts to reduce rotating mass (crank shaft, drive shaft, wheels), when testing a car on a chassis dyno while accelerating, inertia has an impact, so the so-called "drivetrain losses" can be less than we are used to seeing. Last edited by CanAutM3; 07-02-2014 at 11:16 AM.. |
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07-02-2014, 12:38 PM | #7 |
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Not less loss in the true sense, but less inertial impact. I did mention it in my post .
Last edited by CanAutM3; 07-02-2014 at 01:27 PM.. |
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07-02-2014, 02:23 PM | #8 |
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Whether it's 480, 465 or 430hp I don't know. What I do know is that on the same dyno EAS recorded 50 whp more for F80 than E92 M3. That's a lot.
This car is performing at a level above that of a 430hp car that weighs almost 1600kg. Some sort of M black magic going on here......
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07-02-2014, 02:27 PM | #9 | |
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07-02-2014, 02:29 PM | #10 |
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07-02-2014, 06:47 PM | #11 | ||
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07-03-2014, 04:31 PM | #12 |
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I'll just leave this here:
Tune+E30 530whp, 570wtq
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07-04-2014, 11:04 AM | #13 |
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07-04-2014, 11:22 AM | #14 |
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It is possible that N/A cars are more difficult to dyno when you're talking about a 12:1 compression ratio and 91 octane and made worse by high temperatures. Most of the N/A dynos I've seen so far that log parameters show extremely rich running engines and significant timing pulling. Under those conditions, there is no way 414 bhp to the flywheel is going to happen. With a T/C motor, the compression of air will help offset some of this particularly if the engine is a lower compression one, where will be more forgiving with 91 octane. In the dyno above, the 363 bhp stock S65 looks like the engine is producing around 420 bhp, which appears to be very close.
I have logged data using my BT tool on the road where full cooling air and heat exchange effects are present and A/F and timing parameters are much closer to target vs any datalogging I've seen on here. Also the BT tool shows the "Actual Moment" or Torque in NM calculated by the ECU given all parameters calculated by the ECU (e.g. temperature, pressure, mass flow rate etc). Stock engine is right around 415 bhp and with my tune and bolt ons, I regularly achieve 435 bhp-440 bhp. I corroborated this with my Dash dyno tool with open road logging and also get ~370 whp on a flat stretch of road at sea level, which also corroborates the 435-440 bhp (two independent data sources giving the same info). This, in conjunction with the dyno testing done by Rototest and Dinan, who both attempt to simulate for full wind tunnel effects (Rototest has a full wind tunnel), all suggest the S65 stock is around 414 bhp. I personally think many of these at the wheel dynos are giving lower bhp for the S65 vs on the open road. Last edited by FogCityM3; 07-04-2014 at 11:29 AM.. |
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07-06-2014, 06:20 AM | #16 | |
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However, the S55 that is amazingly strong at 414whp... Last edited by CanAutM3; 07-06-2014 at 09:19 AM.. |
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07-06-2014, 09:27 AM | #17 | |
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Even better would be to plot power vs road speed. You need gearing to do that, but it would better depict the difference between the two powertrains. |
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07-06-2014, 11:53 AM | #18 |
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Sorry, I wasn't exactly clear in my post. I believe that the referenced EAS stock dyno for the S65 is the highest or near the highest recorded (at EAS). Most of the EAS dynos appear to be 10-20 whp lower for stock S65. Same with other Dynojets, up to 30 whp lower stock. In another thread someone suggested that the S65 was overrated. So was trying to say the S65 may be a trickier car to dyno as needs full air cooling/heat exchange effect and high compression ratio is not forgiving to high ambient temps and 91 octane, and where altitude, pressure are critical to achieving timing targets, thereby explaining a possibility that the S65 dynos low compared to situations where have full heat exchange effects (e.g. rototest, dinan, open-road logging with BT).
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