Hey Guys,
This past weekend, I had an opportunity to dyno my 2003 M5. Taking advantage of this, I pulled the car onto the dyno, got my RPM signal, put O2 meter in the exhaust, turned off the traction control, ran up to 4th gear and made my pull.

The surprise came when the car hit the rev limiter at 5500 RPM's instead of 7K. What further confuses the issue, is my late 2002 Dinan M5 ran upto the normal rev limit when I pulled it last year.

I am still learning about BMW's and welcome any suggestions/advise. I am sure there must be a logical explanation but did not see any related threads on this forum.....Please help, I would like to dyno the car again to get a true baseline.

Thanks,
Msh

How cold was the motor? What about the RPM lights?

All the RPM lights were off....the car was up to temperature.

Msh

Did you go over 155mph? What were the hp and tq numbers?

To my knowledge I did not go over 155. As a troubleshoot on the dyno, we repeated the run in 3rd gear to rule out velocity; again the rev limiter kicked in at the exact same RPM in 3rd as it did in 4th (5500); I will check with the dyno shop to see what my actual speed was but for this discussion, I think we can rule out velocity.

Well at 5500 RPM's the car was around 330...out of frustration, I didn't even look at the torque.

Great questions....next... ;-)

I wonder if it has a seperate limiter due to the lack of resistance, as in a seperate mode of DSC in the event of total loss of traction? I have heard that holding the button in for 10 seconds deactivates the DSC to a greater degree but I have not verified it. The tip came from a Dinan tech.

On second thought the dyno wheel is pretty heavy and provides more resistance than a wet road...

I'm pretty sure you need to pull a fuse for something or other...I can't recall what though, maybe a search on m5board?

I have heard that holding the button in for 10 seconds deactivates the DSC to a greater degree but I have not verified it. ...

I just read the same thing on an old post relating to clutches, so I will definately keep this in mind...not just for the dyno, I would be curious what benefits/detriments (whole other subject) this has at an autoX or open track events.

My '02 Dinan was an S1 (programmed chip); I am a bit concerned that Dinan set the program to allow dyno pulls....any thoughts on this?

Does anyone know what fuse ///M_trackstar is referring to.

Thanks,
Msh

I just read the same thing on an old post relating to clutches, so I will definately keep this in mind...not just for the dyno, I would be curious what benefits/detriments (whole other subject) this has at an autoX or open track events.

My '02 Dinan was an S1 (programmed chip); I am a bit concerned that Dinan set the program to allow dyno pulls....any thoughts on this?

Does anyone know what fuse ///M_trackstar is referring to.

Thanks,
Msh

Re: DSC button: an individual who works for the company that manufactures the DSC for BMW M cars has said repeatedly that the system in the E39 M5 is on/off with one push. Holding it down will not do anything. In fact, one member tried it and now he cannot disable the DSC at all (button is unresponsive).

And here is your answer regarding the dyno:
http://www.m5board.com/vbulletin/showthread.php?t=59701&highlight=dyno+fuse

I would presume your previous M5 did not have these issues due to the Dinan software.

God Bless the E34M5.:angel

///M trackstar...Thanks for the link; I appreciate your attention to this question and I can now go back to the dyno with a game plan.

Funny thing, went to m5board for the first time per your suggestion and got sucked into reading their great debate about shifters...the thread was plenty interesting, but not sure if I will ever get that hour of my life back :-)

Thanks to everyone else who added their 2 cents worth.

///Msh

God Bless the E34M5.:angel man, I miss mine:(

could it be because the front wheels are NOT spinning?

I know many cars do this.....

An example

My friends RSX type s. She wanted me to show her how to do a burnout in her car. I pulled up the ebrake, selected 1st gear reved the car up and dumped the clutch. The car would hit off rev limiter at 5500 rpm instead of 8000 because its a safety precaution. All 4 wheels need to be spinning in order for the car to rev to its true red line.

Maybe its the same on the M5.

You need to pull fuses 17 and 30 to fully disable the DSC. Turning it off with the switch won't do this. Without it, you hit the 5k revlimiter.

There is suppose to be a trick to killing the DSC by holding the button and switching the ignition on and off in a sequence but the dyno operator couldn't get it to work so we ended up doing the tried and true method of pulling fuses ;)

what else is disconnected by pulling the fuses? Can you run the car day to day with the fuses out?

I wouldn't run it day to day, the DSC is also tied into the ABS system. If you just want to spin the tires, simply use the switch to turn the DSC off. The problem on the dyno is (as mentioned above) the front wheels aren't moving so the onboard systems go into a "safe mode" and limit the revs. You need to pull fuses to disable those.