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Discussion Starter #1
Hi

We measured my M5 (3.6 Euro) today and I only got apx 200Hp and 240 lb-ft (330Nm). It seems after 4000 rpm the Hp curve is really flat.
I am missing 100Hp. The engine have been rebuild 2 years ago.
What can be the problem?
- Fuel pressure
- dirty Injectors
-?????
result


Thanks
Zolka
 

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So is it 143bhp @ wheels?

Can't believe you wouldn't have noticed such a drop off in performance. Does the car feel very slow? With only 143bhp at the wheels, I'd expect it to be very sluggish!

Dyno results are always contentious...............
 

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Discussion Starter #5
I think I have problem with the fuel pressure.
After 4000rpm we measure on full accel. oxygen sensor shows 1.4.....(lamda)
 

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Himizoli said:
I think I have problem with the fuel pressure.
After 4000rpm we measure on full accel. oxygen sensor shows 1.4.....(lamda)
Himizoli
The power graph you have attached looks like it is indicating 143 bhp @ the wheels.
Is this correct ?
The graph also appears flat & consistant which would tend to rule out the wheels slipping on the dyno rollers which tends to show as sharp spikes in the curve.
I agree with Rob in that frictional losses on a perfect 3.5 would give between 240 TO 260 BHP @ the rear wheels.
Taking into account the high ambient temps that rolling roads tend to generate, which M5s dont respond well to, I would say you should expect 80 to 90 bhp more conservatively.
The Curve on my 3.8 showed a steady increase in BHP after 4500 rpm peaking at 272 bhp @ the wheels just before 6,800 rpm with torque curve levelling after 4800 rpm.
Admittedly this was taken 3 yrs ago & a lot of mileage has occured since then but the theory of frictional / parasitic driveline losses are generally quite consistant.

Definate problem but I would have thought the people running the rolling road should be able to diagnose. Thats the primary use of a rolling road.
Ultimate power can only be relied upon using a Engine dyno IMHO...

It must be ignition or fuelling...

Good luck

Regards
Farrell
 

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Himizoli said:
Hi

We measured my M5 (3.6 Euro) today and I only got apx 200Hp and 240 lb-ft (330Nm). It seems after 4000 rpm the Hp curve is really flat.
I am missing 100Hp. The engine have been rebuild 2 years ago.
What can be the problem?
- Fuel pressure
- dirty Injectors
-?????
result


Thanks
Zolka
Hi Zolka
i have a 3,8. 92.
I had a dyno test last year - which ended up in me replacing the whole engine, we noticed the power was at 315 - I cannot remember what it was at the wheels. We thought this was a bit low so we did it again, unfortunately this must have excerbated a hidden problem, and I melted a piston. I was running a chip too.
I would reccomend you fix any problems before you go back on the dyno.

Let us know what happens, or what your findings are - it would be interesting to know.

Rgds
J
 

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I really don't know much about dyno's but how come his torque output is so close to stock since his HP is so way down?
 

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WylM5 said:
I really don't know much about dyno's but how come his torque output is so close to stock since his HP is so way down?
WylM5
I am making the assumption that the 332 figure on the graph is measured in Nm Torque force which is some 235 lbs ft of torque from memory. That figure is 40-50 lbs ft short of what I would expect to see had the torque & power curve been unaffected but as the problem occurs from 4000 rpm both the peak torque & power are capped.
From 4000 rpm upwards I would expect to see the power curve cross the torque curve around 5000 rpm as the torque curve drops away & power climbs.

Most of the torque is deveoped in the first 60 % of the rev range while the power is all developed in the upper reaches of the rev range.

The dyno graph itself tells a story.
The symptoms indicate something holding back the fuelling be it ignition or emission based like an oxygen sensor or fuel starvation which could be a bag load of things.



Regards
Farrell
 

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Discussion Starter #10
The power curve in KW units

The diagram shows the power in KW units so the maximum is 142*1,36=200Hp on the wheels. The problem is at 4000Rpm I already have 190Hp and between 4000rpm - 7000rpm the is no significant Hp gain.
I changed the ingnition coil and the spark plugs.
 

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Re: The power curve in KW units

Himizoli said:
The diagram shows the power in KW units so the maximum is 142*1,36=200Hp on the wheels. The problem is at 4000Rpm I already have 190Hp and between 4000rpm - 7000rpm the is no significant Hp gain.
I changed the ingnition coil and the spark plugs.

Himizoli
Have you had the DME checked for fault codes ? It sounds like fuelling affected by either a engine /emission sensor or restriction in the fuelling system itself.

I wish you well & I hope it is just something reletively straight forward.

Regards
Farrell
 
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