aircon vs full throttle

[Jan]

I had my 540 touring on a dyno today. I had it measured 2 times, with and without the aircon on. With the aircon on, it has about 10hp lower fro 1000 to about 3500rpm and after that it has the same as with out the aircon on.

Does anyone know if it shuts off the aircon pump at full throttle at around 3500 rpm, it seems like it.......

[525iZA]

My parents had a '99 Mercedes E240.

That V6 loved to rev right up to the red line and when you floored it to overtake cars on the high way, you got that funny smell when the A/C has just been switched off... So yes, in that Merc a/c was switched off under full acceleration.

Could probably also be the case with your BMW!

[repenttokyo]

It's a standard feature on Crown Victoria police cars. Full throttle = air con cutout.

[BMWDriver]

I think torque is more at cause here. The a/c gives resistance to the motor, and the engine translates the power in torque to counter that resistance. Past a certain RPM, torque is sufficiently high to free up the power of the engine and drive the a/c comfortably. But mileage will suffer a bit.

This will not answer the question though, but it would not surprise me if the a/c was not turned off.

The M50 is pretty slow to start in low revs because the torque is too low there. That engine really wakes up above 3000 rpms, I find.

[pingu]

Eh? The a/c gives, in effect, some extra friction to the engine. The torque (i.e. energy) that gets used up in overcoming this a/c friction can't be used to drive the dyno and thus won't be measured by the dyno. Or did you mean something else?

[genphreak]

Eh? The a/c gives, in effect, some extra friction to the engine. The torque (i.e. energy) that gets used up in overcoming this a/c friction can't be used to drive the dyno and thus won't be measured by the dyno. Or did you mean something else?

... FW(L)IK.... the ECU shuts down the AC when it so chooses... and on the Motronic 1.3, I am sure this means near and at WOT only.

[Jan]

Here are the 2 dyno runs, the highets numbers are from the run with the aircon on.
It´s a stock 540 with about 270.000km

[pingu]

That's so impressive I want to make sure I've not missed something:

- the 540 M60 is spec'd at 286 bhp.

- and a 540 with 270,000km (about 160,000 miles) still manages to achieve about 286 bhp?

Impressive - and good to know!

[Jan]

That's so impressive I want to make sure I've not missed something:

- the 540 M60 is spec'd at 286 bhp.

- and a 540 with 270,000km (about 160,000 miles) still manages to achieve about 286 bhp?

Impressive - and good to know!

You have not missed anything

This is my second 540 and the other one as dynoed at 285,1hp and 398nm, with about 250.000km.

[pingu]

Did you done anything (e.g. cleaning up the intake manifold) to the engines other than just routine replacement of oil/filters?

My car has had no major work other than routine stuff (oil, filters, thrust arm bushes etc). Those figures are so impressive I just want to make sure that they would apply to me!

Thanks!