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I own a E60 M5 and E46 M3, before purchasing my M5 I thought the M3 was fast. Needless to say I have a new standard for what I consider fast. :haha: The M3 is very sentimental to me and I do not plan to ever sell it. The problem with owning an M5 is that (practically) everything else pales by comparison, particularly with regard to the brutal power the M5 puts down to the pavement.

I decided to spice up the driving experience of my M3 with a multitude of modifications and with the ultimate goal of making the M3 faster than my M5. I recently invested $15,000 on a 8.5 psi Vortech Supercharger kit, headers and high flow cats - a combination that included an advertised whp increase from the stock 260 whp to a very impressive 470 whp.

At a rated 504 crank hp and 414 whp (assuming a 18%) drivetrain loss, and 400 - 500 lb weight disadvantage, I was confident that the M3 would now easily beat a stock M5. It didn't happen. Why? There's basically only two explainations: 1) There's something wrong with my car or supercharger and it's not working properly (this is my hope) 2) BMW and the manufacturer of the supercharger kit are applying different standards when measuring their rated horsepower estimates. (this would suck)

After three weeks of troubleshooting no one has been able to identify any problems with my car, other than the air fuel ratios being off by about 1 point to the rich side. Unfortunately the company that I purchased the kit from is about 1500 miles from me and can't do a lot more without me having to ship my car to them, which I really really don't want to do. The car appears to be putting down about 80 - 100 whp less than I was expecting, based on dyno results and comparisons to a stock and modded M5.

At 370 whp my M3 is just barely getting pulled by a stock M5 and more convincingly by a modded M5. I do not want to imply anything and purposely did not mention the company that manufactures the supercharger until I can come to a more definitive conclusion.

I am hoping some of you can assist me in attempting to validate this one way or the other. The company has stated very adamantly that based on being pulled by an M5 and the dyno results that there is definitely something wrong with my car. At this point I honestly do not know.

General feedback is definitely welcomed, if anyone has any first hand knowledge or experience with runs vs supercharged M3's with similar whp claims that would be great. Unfortunately the supercharger kit is relatively new and I'm aware of only one other car in my area that has it about 300 miles from me. I'm trying to arrange some testing with that car, but it would be helpful to have some additional comparisons.

As stated previously I do not think it is unreasonable to expect a 470 whp E46 M3 with a 60 whp and 500 lb advantage be able to easily pull a stock or lightly modded M5. I also do not think it is unreasonable to expect a 470 whp car to record a higher rating on a dyno than a 413 whp car. If anyone thinks those are unreasonable expectations please let me know! I'm also looking for volunteers that would be willing to hook up with some M3 owners that own the same kit that I have for some dyno comparisons and other testing if a safe venue is available.

At present there is an individual in the Durham, NC area that is planning to hit the dyno next week and is looking for an M5 for comparison. Due the expected variances in dyno results from one machine to another it's very helpful to get a back to back comparisons on the same dyno and on the same day. To those that either have dyno runs planned or would be interested in participating in my national M5 dyno challenge, please PM your email and or phone number to me. Many thanks.

Regards,

Scott

http://www.youtube.com/watch?v=c5SojoYR7A4
http://www.youtube.com/watch?v=kOm6VZtw8UM
 

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Scott you dynoed only 370?! hmmmm something def is not right man. I'm at work now or else I'd be at the meet today talking to you about it. Go to the RKC meet tomorrow and lets talk it out.

First off do you know if you're making full boost or not? What gauges do you have? (I don't recall if you put any on your car yet)

The only thing I can think of is maybe we can run my m3 vs your m3. Yours should walk away from mine. The dyno on my car on 91 oct was 432 whp and 328wtq. BUT my car is much heavier than yours. With the 20" rims and the 300 lb stereo in the trunk it should be quite a disadvantage. If you walk away from my car at 370 whp I would like to assume that your dyno numbers are not correct. If we are even I would assume it would be correct and we need to figure out what's going on. Have you checked all the hoses to make sure you don't have any leaks?

If you have a boost gauge try seeing what the vacuum pressure is at idle. Also might want to check/hear for a slipping belt?

Just throwing out a few ideas. I'm happy to do a couple short runs with you if you want. I do not want to run the car too hard since my car is sold and will be leaving soon =(
 
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