[leew88]

Was interested in what she was putting out so put it on the dyno today at Surrey Rolling Road and made 244.3 bhp and 248 lbs/ft this was calculated flywheel figures by the way, using standard 95RON fuel.

The car runs fine no logged faults and always felt the same since I've owned it and to be honest I was only expecting around 250-260 bhp @ flywheel from a N53 judging by other dyno results off the net so not too far off as this is only an estimated BHP at the flywheel, I was actually putting at around 210bhp at the wheels and the fuelling ratio is spot-on according to the operator. Just for comparison, they dyno'd a Z4 3.0 before mine and that made around 250bhp @ flywheel too.

What actually impressed me the most was that I was making very usable good torque from 2500 - 4500 rpm and is overall fairly flat all the way throughout the rev-range which is what I would expect from a NA 3.0.

Anyone else with a similar engine please post your dyno graphs for comparison, thanks.

[Dormermike]

Is that the 272ps n53 ? Down a fair bit on power if so isn't it?

[leew88]

Originally Posted by Dormermike

Is that the 272ps n53 ? Down a fair bit on power if so isn't it?

Yes it is, according to them they told me it's rare for the N53 to reach the manufacturers quoted peak power for whatever the reason and you need to allow a percentage of error. The only thing in spec and actually better than stock figures is my mid-range torque.

You can also see that the inlet manifold DISA valve is switching OK from around 4500 rpm so this can be ruled out.

[richk84]

Didn't the Z4 still use the N52 engine though?

[Tr1ppy]

I got similar figures for my 330i N53 when I dyno'd it over a year ago. I assumed it was needing a service and a walnut blast but from reading around others have similar figures.

It would be interesting to see difference for those who have changed to the latest injectors (index 11) to see if that makes any difference.

[stevesingo]

On these dynos, the flywheel power is determined from wheel power plus an fixed %, not by a coast down phase of the test where the time for the drivetrain to stop turning after declutching is used to give a measured approximation of drivetrain losses.

Drivetrain losses are mostly tyre to roller losses. Gearboxs, propshafts, diffs, driveshafts are pretty efficient. Given that the bulk of the losses are tyre related, the deformation of the tyre and the speed have great influence. Deformation is related to how the care is tied down and tyre pressures. Speed is obviously related to what gear is used and the faster the wheels turn the higher the losses.

What matters is the calculated losses must be proportional to load and speed, yours are not.

The dyno has calculated a peak torque of 248lbft (141.6hp) @3000rpm which is 8lbft (4.6hp) more than stock, but at the same time 244hp @6250rpm is 26hp down @ 500rpm lower. The % added to the measured peak wheel torque figure at 3k rpm has outputted a greater number than the same % added to the measured peak wheel power above 6k rpm.

I would suggest that either too high a gear was used or tie down was too tight.

[leew88]

Originally Posted by stevesingo

On these dynos, the flywheel power is determined from wheel power plus an fixed %, not by a coast down phase of the test where the time for the drivetrain to stop turning after declutching is used to give a measured approximation of drivetrain losses.

Drivetrain losses are mostly tyre to roller losses. Gearboxs, propshafts, diffs, driveshafts are pretty efficient. Given that the bulk of the losses are tyre related, the deformation of the tyre and the speed have great influence. Deformation is related to how the care is tied down and tyre pressures. Speed is obviously related to what gear is used and the faster the wheels turn the higher the losses.

What matters is the calculated losses must be proportional to load and speed, yours are not.

The dyno has calculated a peak torque of 248lbft (141.6hp) @3000rpm which is 8lbft (4.6hp) more than stock, but at the same time 244hp @6250rpm is 26hp down @ 500rpm lower. The % added to the measured peak wheel torque figure at 3k rpm has outputted a greater number than the same % added to the measured peak wheel power above 6k rpm.

I would suggest that either too high a gear was used or tie down was too tight.

Thanks for your great explanation, there seems to be so many variables that could alter the reading from different Dyno. I guess I can only use this as a rough guide rather than 100% true accurate reading.