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      10-11-2012, 06:17 AM   #1
michal12
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50d engine power not up to BMW figures??

I recently saw 2 independent dyno test of 550xd, neither of them reached claimed 381hp.
The result were remarkably similar. Has anyone else also seen some other dyno tests?
Still hard to judge – maybe the engines were not fully run in or the petrol quality was low. I was also wondering what is BMW’s acceptable manufacturing tolerance in % of the claimed hp output.
Attaching one of the charts. Also I am not sure why the curve is kind of sinusiod shape in higher rpm...

Red is power, blue is torque
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Last edited by michal12; 10-11-2012 at 07:32 AM..
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      10-11-2012, 10:38 AM   #2
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If that graph is to be trusted - it is certainly a bit disappointing.

Wonder how it would compare to a 535d with tuning box?
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      11-21-2012, 01:56 PM   #3
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BMW will quote power at the crank the dyno will be at the wheels. Therefore you would expect a loss through friction through the gearbox and drive line, especially with a 4WD car.

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      11-22-2012, 03:21 PM   #4
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Quote:
Originally Posted by Nick the Greek View Post
BMW will quote power at the crank the dyno will be at the wheels. Therefore you would expect a loss through friction through the gearbox and drive line, especially with a 4WD car.

I seriously doubt that dyno is for power at the wheels. If it was, taking account 15% losses, it means that engine is making over 400bhp and 850NM.
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      11-24-2012, 12:46 PM   #5
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I seriously doubt that dyno is for power at the wheels. If it was, taking account 15% losses, it means that engine is making over 400bhp and 850NM.
Where do you get 15% loss from? BMW are usually quite conservative on quoted power so a figure closer to 400 bhp for an engine quoted at 381 bhp would not be unreasonable. Look at the dyno figures for the new N20 engine conservatively rated at 242 bhp.

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      12-15-2012, 02:11 PM   #6
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Quote:
Originally Posted by Nick the Greek View Post
Where do you get 15% loss from? BMW are usually quite conservative on quoted power so a figure closer to 400 bhp for an engine quoted at 381 bhp would not be unreasonable. Look at the dyno figures for the new N20 engine conservatively rated at 242 bhp.

Yes agree that many BMW engines are under rated but i dont think this is one of them, I would say its the opposite to be honest based on the performance tests ive seen. The 15% drivetrain loss was taken from another thread here were a US member has his 550i on a dyno, im not sure on how accurate that figure is though.

Ill try and find them but there was a test between a M550d vs A6 BiTDI and the BMW was barely any quicker than the Audi. Also in another test between a 535d, M550d and Alpina D5, I was surprised in the little performance the M550d had over the other two and I think in a couple of tests the D5 was quicker.

Looking at the price difference between a M550d and 550i in Germany, i find it tough to justify why you would go for the M550d.
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