Performance Question (MAFS, Air Filter, CPS, Etc)? - The Unofficial BMW M5 Messageboard (m5board.com)

SACM5 · 27th November 2006, 21:11

Okay, so you can see what I have done to my car in the bottom of this post.... I dyno'd my car after a majority of that work was done and it was right around 360hp at the rear wheels if I recall.

That being said I was interested in making a comparison to a stock M5. A friend of my brother has a bone stock 2000 M5 (aftermarket exhaust maybe, Dinan Software maybe). Regardless, my brother has driven both cars and felt just from the seat of the pants meter that the stock M5 was going to get destroyed. Being pessimistic, I told him is probably because my car is so much louder that he feels it is that much faster. So we got on a long straight road and compared head to head from a third gear roll. THE RACE WAS DEAD EVEN. SO close that who ever got the split second jump would prevail. My only strong point was I didn’t have to shift as quickly because my rev limiter is raised via Powerchip. Other than that it was dead even all the way to about 160mph where we backed off. Maybe at the higher speeds I had a little edge but it was not as great as I would have expected based on the mods vs. stock.

So... I started thinking of what the issue could be. So I first assumed the MAF's were the issue. I went out and performed DavidS's MAF test and was getting readings in the 130-142 range (corrected reading of approx 130-135). So based on that I don’t think the mafs are the issue??? I have the Dinan CAI and I noticed the K&N's looked a little dirty when I was installing the HID fog lights. Could the K&N's that are part of the CAI be causing that much of an issue if they are dirty and have about 30,000 miles on them? Other than that I was thinking maybe the clutch was slipping a bit? I am running the original OEM clutch. I don’t have any real problems with it; I notice that once in a while between quick shifts at higher rpms it will lag a bit. However, I am not hard on it and I always make sure it is hooked up before I get back on the gas hard. So I think the clutch was a non-issue, and from a roll in 3rd gear it should not be the culprit since the clutch was already hooked up.

The only other odd items are I recently started getting a strange resonance sound that sounds like it is coming from the floor in the middle to back seat of the car. Maybe something with the drive line?? Seems to be more noticeable when cold and only at higher rpms does it become more apparent?? Also, seems to go away as the car warms up more. Strange... Other than that I got a SES light for an Evaporative Emissions Purge Valve Functional Check, but the light went away after a few miles of driving.

I really thought the MAF's would be the culprit but it doesn’t seem so based on that self test. So I guess the next item might be the air filters. Could they cause that large of a variance at those speeds? Seems like I was minus about 40-60 horsepower somewhere. Basically my car was running dead even with stock (but making a ton of noise doing so through the SS headers and Dinan cans)...

Oh one more thing to note... I know this makes a difference but I still thought with that much more horsepower over stock it would be a non issue.... My brother jumped in the passenger seat of the stock M5 and the owner of the stock M5 had a buddy that jumped in the passenger seat of my car. I have golf clubs and baseball crap in the trunk that probably amounts to 50 pounds+/- and I weigh about 230 and my passenger is probably about 300 and I just topped off the tank prior to our comparison. So my car was PLUS about 580 pounds or so. The stock M5 had my brother and his buddy who each weigh about 150, so a total of 300 and I don’t think they had anything else in the car. So right there I am giving up about 280 pounds to them. I still think with 280 extra pounds the extra horsepower should have prevailed.

Like I said it was dead even.

gbogh3 · 27th November 2006, 21:31

There has got to be something going on, but have you thought about having your car back on the dyno again? The same dyno?
I ran against Olis months ago, his car produced 20+ to the rea wheels and he was pulling away from me almost from the beginning. The filters might be a small problem, having 30k on the them, but not 60hp!

Have you discussed with DA yet?

SACM5 · 27th November 2006, 21:37

Quote:

Originally Posted by gbogh3

There has got to be something going on, but have you thought about having your car back on the dyno again? The same dyno?
I ran against Olis months ago, his car produced 20+ to the rea wheels and he was pulling away from me almost from the beginning. The filters might be a small problem, having 30k on the them, but not 60hp!

Have you discussed with DA yet?

I have not had it back on the same dyno again, but the thought had crossed my mind. Maybe at those speeds the air filters and extra weight are creating a bigger problem than I realize. I know an extra 500 pounds in the car is supposed to slow it down my about half a second based on a 1/4 mile calculator online that someone ran for me.

olis1 · 27th November 2006, 21:41

Is you car still running as strong as it was when you dyno'd it. That would be my first concern. Check to make sure nothings wrong. Maybe even re-dyno it.

Keep in mind it might have been a strong stock M5 with maybe 330-340 hp at the wheels. My Dinan S1 put down 344 hp but more importantly 340 ftlbs of torque with as much as 330 ftlbs of torque coming on down low at around 2000 rpms. I'd be interested in seeing your dyno graph. Peak horsepower is nice but how high is the torque curve across the rpm range. This is what pulls the car most of the time.

The combination of the extra weight, a strong M5 with decent torque curve versus maybe a slightly lower torque curve (guessing here) on your car might have evened things out.

As a data point Gogh and me raced from 3rd to about 120 and I put about 3-4 car lengths on him. His car dynod the week after mine and was putting down 310 hp I believe so the 34 hp or so showed up in the run. Weight were basically equal I believe.

olis1 · 27th November 2006, 21:43

Quote:

Originally Posted by gbogh3

There has got to be something going on, but have you thought about having your car back on the dyno again? The same dyno?
I ran against Olis months ago, his car produced 20+ to the rea wheels and he was pulling away from me almost from the beginning. The filters might be a small problem, having 30k on the them, but not 60hp!

Have you discussed with DA yet?

By the way, at the time of the run with gbogh3 and when my car was dyno'd I had 30k mile old Dinan CAI filters on there and since have changed them with new ones. When I changed them and drove the car I though I noticed a difference but now I couldn't say.

SACM5 · 27th November 2006, 21:44

The car feels just as strong to me as it did when I Dyno'd. People who had taken a ride in mine vs the stock one we compared cant see how it was even close.

SACM5 · 27th November 2006, 21:54

I just found my actual Dyno sheets. I made a couple software adjustments. Intially I was running 353.7 rear wheel hp and max tq was 308.7. Then I messed with the A/F and the horsepower went to 360hp and the torque dropped to 300.9.

So last time it was on the dyno it ran 360 rear wheel hp and 300.9 tq.

phillym5 · 27th November 2006, 22:01

I had headers and all that on my old M5 and ran 12.97 @ 110 at the track. ELEVENS had a Bone stock M5 with just a Tubi exhaust and ran 12.7 @108.

So... maybe it was the driver in your race........

SACM5 · 27th November 2006, 22:04

Maybe, but from a roll in 3rd gear, just in third gear, both cars WOT it was even. To me, that removes any driver issues for the most part.

Maybe the combination of air filters being fairly dirty and the extra weight make that big of a diffrence? Maybe I can get him to do it again without me having the beef in the car with me.

I have run a 13.2 at the track without beating on the car at all. Anotherwards I didnt launch it that hard and wasnt slamming gears. So I am sure if I drove it like ELEVENS explained I would have been in the high 12 range most likely. I also did not change anything tire pressure wise, full tank of gas, golf clubs in the trunk etc, etc. Just like I would drive it around on the street.

gbogh3 · 27th November 2006, 22:13

Quote:

Originally Posted by olis1

As a data point Gogh and me raced from 3rd to about 120 and I put about 3-4 car lengths on him. His car dynod the week after mine and was putting down 310 hp I believe so the 34 hp or so showed up in the run. Weight were basically equal I believe.

this makes me feel better

Beamer_usa · 27th November 2006, 23:02

Driver, correct launch, wheel spin, all big factors in time.

SCC · 28th November 2006, 03:28

When was the last time you replaced your spark plugs? When I replaced mine last month I noticed a fairly significant difference? Otherwise I would go with the added weight you had in your car including the full gas tank.