298bhp M5 Touring

Infinicar said:

I had the M5 Touring Rolling Roaded at the weekend and it made 298.1 bhp - I dont trust rollers as far as I can throw them, but it was free so I didnt care - the operator said all the M Cars (especially the E34 M5 and the E36 M3) never make anywhere near the manufacturers figures. He did comment that my car was lower than normal (about 310 for a 3.8) - he said it was overfuelling (which I kind of knew see previous thread)......

Ive changed the temp sensor and did the ECU unplugging trick, both of which obviously havent worked......

Its going to the 'Ring on Friday.....doesnt appear to be consuming unusual levels of pretrol, so I think Ill just live with it......unless anyone has experiences to share........

Cheers
Paul

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Hi Paul
These things do run rich when they get hot.
I had intermittant problems with mixture & overfuelling.
I did the temp sensor & wiring which was brittle anyway.
I had the fault codes checked on the DME & it listed a o2 Lambda error.
Cleared the fault & wiggled the wire. No more fault.
I put a new flylead & connector on & that cured the problem.

Poor connections & bad o2 sensors will cause overfuelling in many cases & E34 M5 are susceptable to this.

Whilst im sure that this aspect would not cause problems on a few laps round the Nurburgring, I would check the above.
Abit of work with a soldering iron & some shrink wrap & you are sorted.

Regards
Farrell

Cyrus said:

My M5 was only shy 9 bhp from official figures last time I dynoed it and it was overfuelling at top end because it was getting hot in the test area.

The M5 dyno day showed alot of 3.8's made very near stock figures.

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Hi Cyrus
Thing is with Rolling roads that you could take a bunch of cars and test them in one place & the yardstick is that all the comparative ouputs were done under similar conditions such as ambient temps etc so you can compare those vehicles outputs on that day. That is a given except for the tyres each vehicle has fitted.

You could take those same cars to a different rolling road & all the figures could be much lower though remain comparable.

But the fact is with the above that it requires the tyres of each vehicle to remain in contact with the rollers. All tyres have differing compounds & therefore the frictional / slip coefficients play a part in how much direct power is put down. Even a slightly slipping tyre will allow some power loss & the LSD to start transferring power back & forth across the axle.
If its really spikey then it can show on the readout but if its consistant slippage & the slip percentages of the diff are 23% and above across the axle a lot of transitional power slip can be masked & the operator wont always pick it up.

Good tyres play a huge part here & make a difference on rolling roads I have experience with.
An engine dynometer measures power @ the crankshaft.
No friction losses to take account of.
True output from one engine dyno to another can be achieved as long as the variables like fuel & intake charge temp to name a couple are consistant.

Power ouputs from certified engine dynos can be compared... but you can forget that with rolling roads.

It is also known that many certified engine dyno power outputs from O/E manufacturers dont always make the quoted ouput once the engines are installed in the vehicle.

This power output thing is intriguing though. I have also heard that most 3.8's dont make their quoted power & that roumour appears to be driven from ouputs taken from a number of rolling roads.
Mine did not make its quoted power. I did not expect it to. It was overfuelling at the top end once wide open throttle in 4th was achieved.

However a car that may have worn out cats could make more power as the mixture @ WOT could be a little leaner due to increased exhaust gas speeds.

I would like to see some figures from an engine dyno for these 3.8 's but its seems unlikely that will happen.
I have access to the facility but the dynos are emission & durability certing 24/7 so even I would not get a look in.

Regards
Farrell