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Re: Dyno numbers on my '88 750iL (archive)
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Posted by W. McKay on January 29, 2001 at 12:48:57:

In Reply to: Dyno numbers on my '88 750iL posted by RobWilson on January 28, 2001 at 22:56:17:

I see you have the same Owner's Manual as I do. The quoted torque of 376 ft-lb appears to be a typo as all sources agree on 450 N-m (including the manual) which calculates to 332 ft-lb of torque which is posted everywhere else. There is also a mix on engine BHP numbers as well in that they vary between 296 and 300 depending upon the source.

Since this is a naturally aspirated engine, the performance is usually based upon air pressure at sea level. Elevations higher than that will degrade the performance. Some other things I can think of that might be holding it back:
- dirty air cleaners?
- partially plugged cats or mufflers?
- O2 sensors?
- transmission fluid?
- fuel pressure?

'88 750iL


I took my '88 750iL to a local chassis dyno shop yesterday. Here are the numbers measured at the rear wheels:

209.6 hp @ 5100 rpm
249.6 ft-lb @ 4100 rpm

Assuming 20% losses through the drivetrain that equates to 262 hp and 312 ft-lb at the motor. This is a little lower than the owner's manual says that the car should have (300 hp and 376 ft-lb). The dyno curve is a little rough, which usually indicates an ignition problem. From what my mechanic tells me, the car would probably be helped by new plug wires on the driver's side. I probably also need to have the injector's cleaned. Any other guesses as to where I could get back the lost horsepower? The car 224,000 km on it. It is losing a little oil from the driver's side valve cover as well. I've considered doing a couple of performance upgrades down the road, but I want to get it back in shape first. :) It has a few little things that need to be taken care of before I spend any money on performance upgrades (including the oil leak, new suspension accumulators, plug wires, A/C recharge, and the reverse lights).

Rob Wilson
'88 750iL




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