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S50 bhp?

Discussion in 'Performance' started by z3cade, Jan 30, 2012.

  1. z3cade

    z3cade Zorg Guru (III)
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    I've heard that when an S50 in standard form is dyno'd it rarely reaches 321bhp.. Is this true? And why would this be?
     
  2. r37

    r37 Dedicated Member

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    the 321BHP will be measured at the flywheel on a BMW testbed. Things such as ABS, AC and power steering are engine driven and sap some power, you also lose some power in the clutch, gearbox and the rear diff, typically for a modern car the loss is about 10% at the drive wheels. Thats why people list their cars performance in WHP (wheel horse power) because thats where a dyno measures from. Some dynos do compensate for drivetrain losses and can give you a flywheel HP. The engines are also measured at optimum conditions in the BMW factory which will never be replicated on the road. I'd expect a low mileage s50 to come in at just under 300 WHP, same way i expect my 2.8 to produce 175-180 at the back wheels.
     
  3. z3cade

    z3cade Zorg Guru (III)
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    Will find out Sunday.. ;)

    I suppose the only hp that matters is Whp like you say.. :coolsteer)
     
  4. Aceman

    Aceman Moderator
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    From ones I have seen on the rollers you will be lucky to get one to be over 300bhp standard but the odd good one does exceed this figure.

    Also bare in mind the word "dyno lottery" as figures can vary widely from operator to operator so if you are planning on doing mods and do dyno runs after each mod make sure it is the same place you take it to otherwise the readings are meaningless. You also get variations through atmospheric conditions ie. cold days usually mean more bhp but other factors can come into play which is where an experienced operator comes into play.
     
  5. z3cade

    z3cade Zorg Guru (III)
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    Very true Aceman and I agree with you on different rollers etc..

    I do have a dyno read out from evolve from before the cams were fitted at 320bhp..
    Will be interesting to see if it's any different now..
     
  6. HornelZ3M

    HornelZ3M Zorg Addict
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    I read up on this the other day and it has been said that when BMW do the dyno test on the new engine they use 100 octane fuel and can achieve the 320bhp, so with age and not the high octane fuel they read around 290 bhp.
    It is only the S54 engines that are actually the bhp they claim to be. :(
     
  7. DangerousDave

    DangerousDave Dedicated Member

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    As said, dynos are only for comparison and you will only really know the ranking of your car amongst the group.

    If the test is in any gear other than 5th (1.00:1), there will be power losses in the gearbox.

    Temperature and barometric pressure need to be known. These can be compensated for in the final figures. High air inlet pressure = more power (hence turbochargers). Low air inlet temperature = more power (hence intercoolers). High ambient temperature = more power (fluids are less viscous).

    Interesting to find out the effects of turning on ancillaries (lights, A/C, fan, etc), especially on the lower powered cars.

    The shape of the curves is of more importance than the absolute figures. I'm looking forward to the results - I expect to see a very flat and level torque curve from 2000rpm to 7500rpm.
     
  8. Phil

    Phil Zorg Addict

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    The S50 were supposed to be 321 and the S54 325 bhp
    The torque 258 v 261
    The engine capacity 3201 v 3246
    Look under the bonnet and the engines are totally different.
     
  9. deano1712

    deano1712 Zorg Addict

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    My old S50 gave 301 at the dyno. I thought the car was marginally slower than S54's on the road but there was not much in it at all.

    Suspect the Vanos gives variable performance plus you have the dyno operators take on transmission loss to cloud the issue.

    I think it would be much better to quote/compare RWHP which is more easily measured.

    Sent from my GT-I9100 using Tapatalk
     
  10. Aceman

    Aceman Moderator
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    I remember that day well. :)
     
  11. shantybeater

    shantybeater Dedicated Member

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    as said above dyno's are a bit of a lottery. If you are doing it liam ask a few people doing runs at the time what their expected out is & what they get. This should give you a good benchmark so you know if the numbers add up.
     
  12. HornelZ3M

    HornelZ3M Zorg Addict
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  13. Garythefish

    Garythefish Dedicated Member

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    Just make sure the torque and BHP curves cross at 5250rpm

    Where are you taking the car ?

    My remap and dyno was done at Evolve.
     
  14. z3cade

    z3cade Zorg Guru (III)
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    My M has been mapped and dyno'd at Evolve.. But since it's had schrick 284 cams fitted..

    I'm taking it to the rolling road meet on Sunday that's posted on .net
     
  15. z3cade

    z3cade Zorg Guru (III)
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    Wow.. Looks like I need to book it in for the final map.. As its at stage 3
    340-350bhp sounds =p~
     
  16. DangerousDave

    DangerousDave Dedicated Member

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    An interesting comment. Surely, the cross-over point is irrelevant as it is determined by the scales and units of the y-axes.

    The most interesting thing about the Evolve read was the order of doing the upgrades -

    Stage 1 = Standard + Chip
    Stage 2 = Stage 1 + Exhaust + Induction + New Chip
    Stage 3 = Stage 2 + Camshaft + Con-Rods & Bolts + New Chip

    I suspect that very few people do this as they probably try to go straight to Stage 2.
     
  17. Garythefish

    Garythefish Dedicated Member

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    You're correct, the axies will make a difference, that's why it's important that the cross over is at 5250rpm or the figures can be fudged to improve the end figure.
     
  18. Garythefish

    Garythefish Dedicated Member

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    My ended at 347bhp after a little tweek here and there, not bad for standard spec :coolsteer)
     
  19. DangerousDave

    DangerousDave Dedicated Member

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    Good idea - did you just make this number up, or is this a trade standard that dyno tuners use?

    BTW, 347 is damned impressive :-bd
     
  20. Garythefish

    Garythefish Dedicated Member

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    I had another Dyno at another company and the Guy said the calculation for BHP is.....

    Torque X RPM divided by 5252 = BHP @ the wheels, add 20% for approx Flywheel BHP