As several of you are aware, I've been experiencing dyno woes ever since Dinan installed their cold-air intakes. On the dyno, my HP had dropped from 332 RWHP (with just exhaust) to 290-302 RWHP after the CAI was added. At first I suspected a problem with the Dinan CAI, but after speaking with Steve Dinan personally was convinced that the problem lay elsewhere. I was left with a mystery, however -- on the dyno, even with the DSC fuses pulled as I had previously done, the car ran very rich and made only about 300 RWHP.
Last Friday I brought my M5 up to Sacramento dragstrip for a test 'n tune night to try to get a definitive answer on whether the car was making full power or not. The math is simple enough -- a 3950 lb M5 making 330 RWHP in 60-degree weather should run the 1/4 at 105-106 mph, while one making 300 RWHP should run it at 100-101 mph. I had previously run 13.5-13.8 @ 104-106 at the dragstrip with just the exhaust installed, so I had good baseline figures to compare to.
What I found was very interesting. My best run was 104.3 MPH in 85-degree weather, so my M5 is making all the horsepower it is supposed to. However, this run was accomplished with no wheelspin at launch and no wheelspin in the 1-2 shift. EVERY TIME I HAD ANY WHEELSPIN, THE POWER LEVEL WOULD DROP FOR SEVERAL SECONDS. This was most noticeable during one run with a C4 corvette in the lane next to me. I had a little wheelspin on the launch, and the corvette and I were dead even through first gear, and dead even through second gear. About a second after I shifting into third, I felt the M5 surge forward and left the corvette behind. The 'vette and I had similar shift points, so the most logical explanation for this was that the M5 ECU had decided I was no longer having traction problems and had re-engaged full power. Similarly, when I did a burnout before my launch, 1st gear felt quite sluggish, and the car would wake up again in 2nd. If I had wheelspin in the 1-2 shift, 2nd gear would feel dead and the power would return sometime while in 3rd.
Conclusion: (1) The traction control software has definitely changed sometime in the past year. You can no longer completely turn off traction control, even by pulling the fuses or by the console switch. Based on my dyno results, with traction control off I believe the ECU ******s timing and/or richens mixture to reduce power when it senses wheelspin, usually to the tune of 30-40 RWHP. Optimal acceleration in the M5 with this software thus involves avoiding wheelspin on the launch, and babying the 1-2 shift to again avoid wheelspin.
(2) There's nothing wrong with the Dinan CAI or software. I can't state what HP gain is obtained with the CAI, but my car's still making approximately the same power it used to.
I will be speaking with Dinan this Monday about a fix for the traction control disable. I'll post any information I receive.
Thanks, Ben - very interesting. Are you saying that you think this "feature" crept in when Dinan loaded the new software into your car, or was it there always? My car is fairly early - a Feb'00 build - and I don't THINK it ******s power at all when DSC is switched off.
Greg -- I don't know when this DSC characteristic crept in. My car's also a Feb '00 build, and I wasn't getting any DSC when I ran my 13.5 @ 106 last year, as I recall a fair bit of launch and 1-2 shift wheelspin on that run. I've had my car to BMW perhaps 10 times for various services, and they could have updated the software at any point. My current build's "2/1-30" according to the "Set" menu -- what build do you have?
Regarding the CAI, even Dinan claims only 5 HP from the intakes. That's too small a difference to notice anywhere except the dyno...
------------------
Cheers, Ben ('98M3'99RX300'00M5'01RT/10'01GP1200AndNoGarageSpaceLeft!)
THANK YOU BEN!!! I am relieved, I thought it was clutch slippage.
I was at the strip last month and experienced exactly what you describe...
"I spun hard in 1st. Shifted into 2nd, again - spinning and bouncing off the rev limiter.
What really mystified me was the shift into 3rd. I swear I may have heard the limiter again. The car also felt as if it paused for a moment, then took off again. This gave the (turbo) Civic the momentum to reel me in.
The closest seat-of-the-pants sensation I can compare it to is DSC kicking in, but it was certainly off.
I was highly suspicious of the clutch, but it seemed fine on the drive home. Plus, there was no clutch smell evident after the run."
That was a 14.0 @ 102...that 2/3 shift let all the air out of my sails - plus I worried about my clutch for like a week.
Mystery solved! I'm gonna try again and make sure my 1/2/3 shifts are not too butch so as to stay out of traction control.
Would still like to be able to turn it completely OFF - please keep me posted.
Regards
Alps
[This message has been edited by alpywhite (edited 11 June 2001).]
Very interesting! According to the manual, turning off DSC is supposed to turn off the traction control, but seeing hat the traction control system consists of two functions (individual control of each rear brake to emulate LSD and torque control), perhaps only the LSD function is actually turned off?. On my 6/00 build, I can play a game with the DSC button that is neat:
1. Push DSC button (warning light turns on)
2. Continue to hold for about 5 seconds (DSC warning light turns back off)
3. Let go of DSC button
4. Subsequent to this procedure, the DSC appears "locked" in some manner - pushing the button again (and again, and again...) will not cause the DSC warning light to turn on. The system does not unlock until you turn off the car and restart it. I haven't had a chance to romp since I discovered this, but now I'm wondering if just maybe it disables torque control? Has any one else tried this?
Isn't it true that even with the DSC switch turned off, the traction and stability is not completely turned off but rather EXTENSIVELY minimized? I thought for safety reasons, these systems are never 100% disengaged
Reza
Motor trend had an article with a 330 in which they were experiencing a similar problem with the DSC off, but the traction control was still engaged when the rear wheels spun. What they did was pushed the DSC button and held it for another couple of seconds, i think. It was a while ago and i don't really remember what exactly they did.
It seems like DSC is similarly setup to the Active handling in the corvette. You can have it fully on, or in competition mode. In the vette it shuts off the active handling but leaves the traction control on. In both you have the option of shutting the whole system down. I'm not quite sure why BMW has to be so discrete about this. I figure they don't want people to get too out of line by installing that traction control with the DSC off, but they don't want to totally restrict the car as well so they keep quiet about the method to shut it off.
Can someone explain to me how it is possible to todo smoke your tires completly and to drift with all 4 tires if traction control and/or DSC is not completely of.
I'd say its either on or off.
The clucth can slip some due to high temperature and when it cools off it's fine again.
Can you have lost power due to very warm temperature either outside or near your car? Maybe you stood lined up waiting to race with your engines running and around you other guys with their engines running, imagine what this does for intake air temperature!
Cheers,
/Johan
[This message has been edited by johann (edited 11 June 2001).]
Linear Mode
