Fuel cutoff at 100? - The Unofficial BMW M5 Messageboard (m5board.com)

SeanMD · 24th March 2005, 23:26

I know there has to be a perfectly logical reason for it, but I noticed today that exactly at 100 (observed in a closed course and controled environment of course). It occured under the following conditions exactly

1st: "speed limit" was set to on w/o my realizing it and was set to 100, after this occurance, the engine bogged and it seemed like the fuel maps were set to U L T R A conservative, as it actually would bogg down if I applied the accelerator and actually "sputter", prompting me to drive in 6th until finally turning the car off after parking.

2nd: 100 mpg "speed limit" turned off through the NAV options and cut off again exactly @ 100, this time though, the fuel curves did not seem as extreme though I did not test it at all before shutting down again.

3rd: manually set "speed limit" settings to max (186) and still occured, shut down immediately after slowing to stop.

4th: manaully at 186 and turned off "speed limit" option....same results.

I have yet to be provided with the factory book as I'm picking up the odds and ends from the dealer this weekend so I'm unable to look through that to see what the issue might possibly be. Any help or information would be GREATLY appreciated.

Sean

mottati · 24th March 2005, 23:32

something is not right with the car. THe speed limit function on the obc has nothing to do with the actual top speed of the car, it simply sets off a "gong" at whatever speed you have set to let you know you have exceeded your set limit. Must be something else going on.
Mike

dmz · 24th March 2005, 23:46

Can you tell us what tire size are you running front and rear? This sounds like a tire OD mismatch problem where the DSC kicks in when it senses the rear tires turning faster than the fronts. Have you tried the test with DSC off?

SeanMD · 24th March 2005, 23:53

Quote:

Originally Posted by dmz

Can you tell us what tire size are you running front and rear? This sounds like a tire OD mismatch problem where the DSC kicks in when it senses the rear tires turning faster than the fronts. Have you tried the test with DSC off?

Tires/rims are OEM sizes so I don't believe that should interfere, though admitedly I have not tried with the DSC or the wheel control off (either one). Would either of those have ever been known to affect the fuel maps after being triggered in a case like this?

mottati · 25th March 2005, 00:28

Quote:

Originally Posted by dmz

Can you tell us what tire size are you running front and rear? This sounds like a tire OD mismatch problem where the DSC kicks in when it senses the rear tires turning faster than the fronts. Have you tried the test with DSC off?

good call, i was thinking about that too... kind of like running on the dyno with the dsc fuses in. Maybe there's an abs sensor problem.
mike

SeanMD · 25th March 2005, 01:13

Thanks much for the suggestions, I'll try the DSC next time to see if that is the source of the problem. Though in the case that it's not, what would be a good starting point for diagnosing if it is a sensor or is that something that I would want to have the techs hook up to find out?

Many thanks for the responses

Mike: as far as the dyno goes, if I were to happen to be going soon to hook the beast up for a baseline, what would I need to make sure was prepped prior to making the runs?

mottati · 25th March 2005, 01:24

Quote:

Originally Posted by SeanMD

Mike: as far as the dyno goes, if I were to happen to be going soon to hook the beast up for a baseline, what would I need to make sure was prepped prior to making the runs?

I'd suggest a search to verify this, but i think you want to remove fuses 17 and 30 to disable the dsc for the dyno.

If there were an abs sensor issue, i'd think you'd have an abs light.

As for the original problem, does it matter what gear you're in?
Mike

SeanMD · 25th March 2005, 04:26

Quote:

Originally Posted by mottati

I'd suggest a search to verify this, but i think you want to remove fuses 17 and 30 to disable the dsc for the dyno.

If there were an abs sensor issue, i'd think you'd have an abs light.

As for the original problem, does it matter what gear you're in?
Mike

it was in 4th in all instances, rpms were not anywhere near redline. I can do some more testing to determing if it the gearing has a part to play in it (both with and w/o DSC enabled)

SeanMD · 25th March 2005, 22:17

same results no matter what gear I'm in.