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Just had my 1999 E39 M5 :M5launch: on the rolling road.
I had it dyno'd last year before I found out that you have to pull fuses 17 and 30 to gain full rpm, and was disappointed with an engine output reading of only 347hp.
This time the figures show 432hp at the engine and 323hp at the wheels.
My question is - is 111hp a realistic transmission loss, or is the dyno over estimating the engine output ?
Anyone else had similair results, or have any comments ?
I have owned the car for 2 years, and haven't carried out any engine mods, although I am considering a remap.
I think that the previous owner must have removed the speed limiter as I have seen an indicated 175mph (although that is probably only about 155 real mph).
If anyone has any suggestions for performance mods, I would be more than happy to hear from you !
 

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Your results sound pretty normal for a stock M5. I think 432 crank is way too optomistic for 323 at the wheels, the number i hear thrown around is 18% driveline loss.
Mike
 

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Talking about losses as a percentage doesnt make sense, two cars at the same roller speed with the same weight over the axle and similar tyre pressures will have the similar losses regardless of engine output, is it right to say that a car with 400BHP loses twice as much as one with 200BHP at the same roller/engine speed?

The losses on a rolling road are not the same as those experienced on the road. One of the main losses on the RR is through the tyres, the relatively small diameter rollers produce unnatural compressions of the tyre wall which result in much higher losses than those sustained on the infinite radius of a road surface. I have data from 000's of RR runs and have never seen losses higher than 60BHP (as measured with coastdown testing), that said the losses are generally proportional to roller/tyre speed so measurements taken at high roller speeds tends to result in higher losses, this makes the selected gear very significant.

Unless the RR you use has a coastdown facility to *measure* the rolling losses then the estimate of losses is just guesswork and to express this as a percentage is flawed.

My guess is that 100BHP losses is too high.

If you want to win an 'at the wheels' power contest, inflate your tyres to 60PSI (reduces rolling resistance) and take the run in 2nd gear where roller speed will be relatively low, dont give much hope for you traction though.

Dave
 

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I was quoting the figure i'd seen discussed on this board many times, and had assumed we would all understand I was referring to an M5. I'd imagine a different car with a different drivetrain would have a different percentage drivetrain loss. But, i would also argue that a car with 400hp will loose more hp thru drivetrain friction than a car with 200 hp. (but i think that would be a different thread)

In my limited experience, it seems that whp is higher in numerically higher gears. Every dyno i've seen (from dynojet dynos) has a higher whp in 5th vs 4th and also higher in 4th vs 3rd.
Mike


Dave Andrews said:
Talking about losses as a percentage doesnt make sense, two cars at the same roller speed with the same weight over the axle and similar tyre pressures will have the similar losses regardless of engine output, is it right to say that a car with 400BHP loses twice as much as one with 200BHP at the same roller/engine speed?


Dave
 

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Phil_m5_scotland said:
Just had my 1999 E39 M5 :M5launch: on the rolling road.
I had it dyno'd last year before I found out that you have to pull fuses 17 and 30 to gain full rpm, and was disappointed with an engine output reading of only 347hp.
This time the figures show 432hp at the engine and 323hp at the wheels.
My question is - is 111hp a realistic transmission loss, or is the dyno over estimating the engine output ?
Anyone else had similair results, or have any comments ?
I have owned the car for 2 years, and haven't carried out any engine mods, although I am considering a remap.
I think that the previous owner must have removed the speed limiter as I have seen an indicated 175mph (although that is probably only about 155 real mph).
If anyone has any suggestions for performance mods, I would be more than happy to hear from you !
325 to 345 is very normal and it varys because of engine varinces and dyno's along with air temp and the cars computer. How the computer comes up with 111 hp loss is beond me, no way the car is putting out 430hp, The car stock as you say; so thats 394 at the crank. So at 332 whp thats 62 hp or 16 percent driveline loss, within reason with all the normal variences.

Let me ask you this...Does the car feel as normal as it did from day one? If so whats it matter about the numbers?
 

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mottati said:
In my limited experience, it seems that whp is higher in numerically higher gears. Every dyno i've seen (from dynojet dynos) has a higher whp in 5th vs 4th and also higher in 4th vs 3rd.
Mike
My results were the opposite, both 4th gear runs were better than 5th gear runs.Difference of 6-7 hp. It might be an anomoly because I am running a taller diff, so 5th is like pulling stock in 6th and 4th is like pulling stock in 5th.
Regards,
Jerry
 
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