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M6 Kelleners / Schrick Cams, Active Autowerke CAM ECU, Supersprint X-Pipe & Mufflers

9K views 54 replies 34 participants last post by  Gustav 
#1 ·
Its been 2 FULL weeks since Active Autowerke started working on my M6.

Before I get started, I just wanted to direct anyone interested in my vehicle's cam progress to my previous thread that I started back on December 1st, 2006. This way, you guys can get an overview of the preparation I went through before Active started on my car. Here is the thread:

http://www.m5board.com/vbulletin/showthread.php?t=85676

Even though I asked Active to take photos of the install as it progressed, they were so focused on the job; they didn’t even end up of taking photographs at all! Sorry guys....no pictures! :sad1:

Anyhow.....here are the latest updates on my car thus far:


Using the BMW instructions, the required special tool set, and replacement gaskets I provided, Active began breaking down the engine for the cam upgrade. Shortly after they started, they realized that I never provided them with the instructions for the vanos adjustments required to complete the install! So, they had to do some research and picked up the additional required documentation to continue the job.

The install moved along and the driver’s side cams were pulled and replaced without any issues. But when it came time to pull the final cam on the passenger side, for some reason, the special jig wouldn’t fit over the cam to remove it. Active spent two days between repair books and speaking to some of their contacts at BMW before they came to realize that the 4th cam on my car was never aligned correctly from the factory! Therefore, it couldn’t be removed with the special tools through conventional means.

Here was the email Karl from Active sent to me last week:

"...Scrappy and I are still here working on your car, we did the driver's side cams quite easily, but the passenger side is giving us a warm time. We were here on Tuesday night as well. We are taking our time to check, double check, triple check everything and that is why we are taking so long. The problem we encountered on the passenger side cams was the factory alignment of the exhaust camshaft was off, the jigs would not fit and after trying like 4 times we came to the conclusion that the vanos gears were never aligned properly from the very beginning. So here we are on Wednesday night making our own special tools to take apart the vanos cam helical gears to align them before installing. We are getting somewhere!!......"

GEEZE! This means my car was never running the way it should have been from the very instant I drove it off the lot!

After picking apart a number of dyno runs I located online, I noticed my stock DynoJet dyno pass at 422 to the wheel with the carbon air filters removed was about 10 whp lower than what most of the other M5s & M6s were putting down. Even my latest DynoJet pass at 459 WHP after the SS headers & cats w/ AA ECU seemed a bit off when compared to another M5 with the similar mods.

After discussing this issue over with Active last week on Friday, we figured we may very well see "higher than normal gains" from the cam upgrade since the last dyno pass was run with the incorrect stock cam timing.

So, I waited for the weekend to pass and called Active on Monday late afternoon to see how things were coming along. The car was back together and they were already working on the cam ECU tuning. They said my car put down 448 wheel horsepower on their Mustang dyno! For those of you who don’t know about Mustang dyno statistics, Mustang dyno numbers always show lower HP numbers than DynoJet dynos. If you take a look at my SS Headers/Cats thread at:
http://www.m5board.com/vbulletin/showthread.php?t=79620

You will see my best Mustang dyno run put down 410 hp to the wheels

--------------------------------------------------------
The Mods on my car when the 410 hp was produced were:

Carbon air filters removed
Supersprint Headers
Supersprint Cats
AA Header/Cats ECU Tune
(Slightly compromised exhaust cam timing)

--------------------------------------------------------

The Mods on my car when the 448 hp was produced were:

Carbon air filters removed
K & N stock filter replacement
Supersprint Headers
Supersprint Cats
AA Cam ECU Tune
3.91 Dinan Differential (doesn’t effect HP)
Schrick Kelleners cams
(Correct exhaust cam timing)

--------------------------------------------------------

After my last conversation with Karl on Monday afternoon, he explained to me that my car was running a bit too lean in the midrange and that they are still working on getting the timing and fuel ratios perfect. In addition, they were also working on trying to figure out how to crack the code in the ECU to raise the rev limiter. According to the dyno sheets, Active is certain that if they can get the motor to spin a few hundred more RPM they will squeeze another 5-10 HP out of the car. Raising the rev limiter will cause the RPM on each up shift to fall into a higher more optimal power range when running through the gears under full throttle.

Once Active is done with the tuning on the Mustang dyno, they will run the car over to a DynoJet dyno near their shop and get a final HP number.

Cams and tuning complete…………NEXT...........the M6 goes back to Active immediately to get the Supersprint X-Pipe (with SS resonator) and the Supersprint Sport Mufflers installed. They may touch up the tuning some once the new exhaust components are installed. Lastly, one last trip back to the DynoJet for a Grand Finale pass.

** (Just to let you know, that since my M6's factory cam timing was off, the car was putting down approximately 12 less horsepower to the flywheel than normal. Therefore, my HP conversions were off when I calculated 50 flywheel hp for the Supersprint headers, cats and ECU. In reality, the M5/M6 e60/e63 will put down 40 additional flywheel HP with these upgrades.)
--------------------------------------------------------
So all and all, my M6 upgrade components will consist of:

Carbon air filters removed
K & N stock filter replacement
Supersprint Headers
Supersprint Cats
Superprint X-Pipe w/ SS Resonator
Supersprint Sport Mufflers
AA Cam ECU Tune
3.91 Dinan Differential
Schrick Kelleners cams
--------------------------------------------------------

I am projecting a DynoJet final number of 490-505 HP to the wheel! With the correction factor applied for drive train loss, my car will be producing between 575 to 592 Flywheel HP!

Final results and initial driving reports coming soon! I will post all the dyno charts once Active is done with the car. Then I am off to the drag strip for some quarter mile runs!

Keith
 
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#4 ·
Wow!!!

Please, please, please take video clips before x-pipe and mufflers. I would like to hear what the beast sounds like before these mods. I am considering the same mods (minus x-pipe and mufflers) but I do not want the thing to sound too obnoxious.

Cheers ///
 
#6 ·
KeithTa said:
The install moved along and the driver’s side cams were pulled and replaced without any issues. But when it came time to pull the final cam on the passenger side, for some reason, the special jig wouldn’t fit over the cam to remove it. Active spent two days between repair books and speaking to some of their contacts at BMW before they came to realize that the 4th cam on my car was never aligned correctly from the factory! Therefore, it couldn’t be removed with the special tools through conventional means.

Here was the email Karl from Active sent to me last week:

"...Scrappy and I are still here working on your car, we did the driver's side cams quite easily, but the passenger side is giving us a warm time. We were here on Tuesday night as well. We are taking our time to check, double check, triple check everything and that is why we are taking so long. The problem we encountered on the passenger side cams was the factory alignment of the exhaust camshaft was off, the jigs would not fit and after trying like 4 times we came to the conclusion that the vanos gears were never aligned properly from the very beginning. So here we are on Wednesday night making our own special tools to take apart the vanos cam helical gears to align them before installing. We are getting somewhere!!......"
:eek:h:
That is not good! Trusting their assessment, which you have every reason to, means that this technological masterpiece of an engine gets put together wrong?

Good luck, too!
 
#8 ·
Thanks for being a leader in this area. There may be some motors not put together correctly? That will be too bad for my lease return. Ha.
 
#10 ·
A fascinating project - it'll be interesting to see how reliable the car is after all that work.

All the best.
 
#14 ·
Intresting, have you talked to some'one @ BMW about this?grrrrrrr
 
#15 ·
BostonRocket & 6speed: A few of the guys as Active are telling me the car has a mild "cam" rumble. Almost sounds stock but if you listen closely you can hear the cam somewhat. I will be taking video clips with sound when I pick up the car.

6speed: I didnt add the standard SS X-Pipe, instead I went with the SS Resonator. The SS Resonator is basically the SS X-Pipe with a high flow resonator in the center for a softer exhaust note. I am also going with the SS Sport mufflers which will also carry a milder exhaust note compared to the SS Race Mufflers.

Flyinbysti: I will certainly post an update to this thread with initial driving impressions after the drive home from Active this Friday.

----------------------------------------------------
Once my car is returned, I have a local M6 without carbon air filters lined up for a base line race against my car before he installs Nitrous. Will post video as soon as possible.
 
#16 ·
Keith...Congrats on the cam job. I will be patiently awaiting the final dyno results.
 
#19 ·
6speed: I didnt add the standard SS X-Pipe, instead I went with the SS Resonator. The SS Resonator is basically the SS X-Pipe with a high flow resonator in the center for a softer exhaust note. I am also going with the SS Sport mufflers which will also carry a milder exhaust note compared to the SS Race Mufflers.

Thanks for the info. I did not know SS sold an x-pipe with a high flow resonator. Also, did you specify the 90mm tips for the sport mufflers? There is quite a difference in size and they look great!


Cheers ///
 
#22 ·
Ok….get ready for a LONG POST………here it goes:

Just before I picked up my car from Active Autowerke on Friday, I had a disturbing conversation with Karl Hugh (one of the owners).

He explained that after the Kelleners/Schrick cams were installed and the ECU tuning was complete, they ran my M6 on the DynoJet and found that it actually LOST power!!!!!!!!! From their view it seemed to have lost 5-10 whp in the mid range and lost about 1 whp on the top!

WHAT ??!!! I LOST it over the phone...

Baffled, I asked, "How could that possibly be?!? My car just put down 448 whp on your Mustang dyno yesterday - 38 whp MORE than the base line run we did 4 months back....then you bring my car over to the DynoJet and it shows a LOSS in power????? What gives?????!"

Mustang dyno from 9/7/06: 410 whp
Mustang dyno from 1/16/07: 448 whp (after cams and tune)

DynoJet dyno from 9/7/06: 459 whp
DynoJet dyno from 1/17/07: 458 whp (after cams and tune)

Karl pointed the finger at a recent software update they had applied to their Mustang dyno that evidentially changed the HP calculating algorithms giving us false hope for big DynoJet numbers!

So now what????!!!!

Active did nothing wrong.....they did exactly what I asked them to do. They installed the cam shafts based on the factory specs as discussed......At this point, I had to call the tuning shop Kelleners Sport (who originally sold me the cam shafts) in Germany to find out what the hell was going on.

Patiently, I waited till the next morning and phone Kelleners. After an in-depth conversation with Ralf Kelleners I was now clear that cam ONLY swap was to affect the M5 and the M6's as follows:

A 5-7 engine hp LOSS between 4,000-6,000 RPM
NO increase or decrease in hp between 6,000-7,000
A 15 engine hp GAIN between 7,000-8,250 RPM

(The above specs are in line with cam upgrades from my past experiences - I was ok with this information) (And just to let you know, the bigger cammed M5 HP numbers we have been seeing around the boards for some time were produced from Kelleners’ COMPLETE power upgrade package which included a few other mods along with the cam shafts).

But fine.......great......Why in the world did my car LOSE 1 HP on the top???? Where are these 15 supposed ponies then?? Definitely not in the car according to my dyno sheets!

Ralf Kelleners really couldn’t tell me what I wanted to hear....The only thing he kept referencing was the fact that we were relying on an old base line run from 4 months ago and that I should have baselined the car the day before the cams were installed to get a clearer picture of hp movement. I agreed there. Nevertheless, he tried to dig deeper and asked me what changes were applied to the car since the last Dynojet pass of 459 whp on 9/7/06. I explained that the paper filters were replaced with a set of K & N filters and I installed the Dinan 3.91 diff. He said those upgrades really wouldn’t have done much to horsepower figures and that unfortunately driving the car at this point would be the only REAL test I could do. Dissatisfied and aggravated we finished our conversation in a civil manner and I hung up the phone.

I immediately called Active and told Karl that nothing came of the conversation between myself & Ralf Kelleners and that I needed time to think about what I am going to do regarding the cam issue.

In the meantime, I had some Supersprint exhaust components sitting at Active's shop that I needed to get installed to complete the job on my car. So, trying to push aside my frustration and disgust, I asked Karl to proceed with the install. And in 24 hours the Supersprint Resonator (Supersprint's X-Pipe w/ high flow resonator) and the Supersprint Sport Mufflers were installed. The car then went back to the DynoJet and ended up producing a measly 1.5 whp more from the exhaust components.

Ludicrous! Lost 1 hp from the cams and gained 1 back after adding the exhaust. Go figure.....when it rains it pours!

So.....I took the day off on Friday and drove to Active to pick up my completed car. I took it for a ride and it felt strong but I couldn’t really tell if it picked up or lost any power...............figures!!!..........right in line with a ZERO horsepower gain.

After road testing the car, I then sat down in the office with Karl before I left his shop and began picking apart the dyno charts.....we were changing around some Correction Factors in the DynoJet viewing software to see if we could uncover anything at all....the search was unsuccessful - so I told Karl that I would take all the dyno charts home and analyze them over the weekend and that I would catch up with him next week. So I hit the road and started home.

On the brighter side, the exhaust note was improved. On the ride home I noticed the exhaust sounded a bit deeper and smoother than what the stock resonator and mufflers sounded like before. Also - that "raspy pennies in a can” sound that my exhaust gave off before was GONE. The overall look of the exhaust with the 90mm tips and weight saving were a plus. But STILL for the money I spent.....this just WASNT RIGHT!

As I continued home, I phoned Fynetune Performance to schedule a DynoJet run for Saturday morning. This was the same exact DynoJet that Active used to test my car each time any upgrade was applied. This time, I wanted to be there while the dyno passes were performed.

I spent most of Friday evening breaking down all the dyno charts and ended up uncovering something very interesting. Remember...........I had a set of dyno runs from when I added the SS headers, cats and ECU on 9/7/06 BEFORE all this work was done. I then had the cam only runs from 1/17/06. AND I have the runs with the cams, resonator and mufflers together that were done on 1/19/06.

So I started to pick the runs apart. Here we go....

The highest of 7 runs with the cams only was approx. 459 whp. The highest of 7 runs with cams and exhaust together was 460 whp. Pretty much no real gain.

BUT…… what I found was that the AVERAGE of all the “cam only” runs was 452 whp. The AVERAGE of all the “cam with exhaust” runs was 459 whp.

So, by calculating averages, the rear section of the Supersprint system actually produced 7.5 whp. Ok were getting somewhere.....But why was this 459 whp cammed run so different than the average cammed run of 452 whp??? BAM! The gear ratios!

The time I got the 459 whp run with the cams only was when the car was in 5th gear. All of my runs with exhaust & cams were done in 4th gear! So I was comparing a 5th gear cam only run against a 4th gear cam with exhaust run. That’s why the addition of the rear section of the exhaust showed no power gain.

The more I looked at the different dyno charts, the more I realized that the lower the gear the lower the HP reading on the dyno! I also noticed that after breaking down the "gear ratio thing" even more I noticed that the Dinan 3.91 Diff was reducing my horsepower numbers as well! I called DynoJet to confirm this and they reinforced my findings as true. They told me that anytime you add a "steeper" rear end on a vehicle it will show a reduction in horsepower readings on the dyno. Not because the M5/M6 engine actually loses power but because the car loses some HP through its drivetrain and does put down all of its power until in the higher gears. Also chassis dynos take into consideration the actual speed of the car in MPH when its spinning the dyno rollers and it also considers the RPMs of the engine. Since both of these variables change in proportion to each other when the 3.91 diff is in our cars, horse power figures will be skewed for the worse!
_________________________________________________________________

So.........Saturday comes around and I get my car on the DynoJet at FyneTune performance. I asked the owner Andre, to run the passes in different gears to prove my point.

This was the result:

Top figure - 5th gear
Middle figure - 4th gear
Bottom figure - 3rd gear



As you can see above there was quite a difference in the power my car makes from gear to gear.

Then on top of these figures, I am running the 3.91 diff which is further negatively impacting my HP numbers by a projected (7-20 whp + or -) depending on the test gear. I wanted to try a 6th gear pass to see what happened there but ran out of time.

_________________________________________________________________

Ok….on to the “BEFORE Cams AFTER Cams” DYNO SHEETS.

Here were my mods on the pass dated 9/7/06 (457.51 whp – 4th gear pass):

Carbon air filters removed
Supersprint Headers
Supersprint Cats
AA Header ECU Tune



Here are my mods on the pass dated 1/17/06 (451.98 whp – 4th gear pass):

Carbon air filters removed
Supersprint Headers
Supersprint Cats
AA Cam/Header ECU Tune

Kelleners/Schrick Cams
Dinan 3.91 Differential



As you can see from the dyno sheet above, my car shows a loss in power after adding the cams. But if you look at the SPEED in MPH on the bottom of the chart, you will see that the runs were not “matched up” or “merged” over each other since they started and stopped at different speeds. This is due in part to the Dinan 3.91 diff. The gearing change from the diff hurt the HP numbers on the cammed run.

_________________________________________________________________

If you merge the same two runs by RPM instead of SPEED in MPH, you can see the difference between the 2 runs more clearly. Again, the TRUE HP of the Cammed run is “skewed” or distorted since the gearing is different. The question is…….. How much did the diff affect the run?????? (See chart below)



_________________________________________________________________

Now change the HP correction factor from SAE to UNCORRECTED (an adjustment in the dyno viewing software) and the cams start to show a bit more power at the very end of the RPM band. (How much more HP would they have shown in this cart if the rear end gears were identical??) (See chart below)



_________________________________________________________________

Now take a look at this UNCORRECTED dyno sheet run:
This dyno chart shows a completely different cammed run that was done in 5th Gear with the 3.91 diff. The 5th gear gave the cammed run an advantage over the non-cammed run which was run in 4th gear.



Now the cams are showing power. But this isn’t a fair assessment.


_________________________________________________________________


The final chart below is set to a correction factor of “standard”.






The 1st run of 484.97 (Was a 5th gear pass with the 3.91 diff)

Upgrades:
Carbon air filters removed
K & N stock filter replacement
Supersprint Headers
Supersprint Cats
Supersprint X-Pipe w/ SS Resonator
Supersprint Sport Mufflers
AA Cam ECU Tune
3.91 Dinan Differential
Schrick Kelleners cams


The 2nd run of 470.11 (Was a 4th gear pass with the stock diff)

Upgrades:
Carbon air filters removed
Supersprint Headers
Supersprint Cats
AA Header ECU Tune


The 3rd run of 432.87 (Was a 4th gear pass with the stock diff)

Upgrades:
Carbon air filters removed

So in this dyno chart, the dyno pull in 5th gear (the 484.97) had a HP advantage compared to the other runs since it was in a higher gear.
_________________________________________________________________

OK…..enough of that…………..


Kelleners claims about a peak of 15 hp at the crank with their cams. Every conversation I have had with them, they were adamant that their cams have a positive affect on the M5 and the M6 in the last 7,000-8,250 RPM range.

Here is a dyno chart they sent me with a stock M5 baselined without the cats. Then they added the cams without any ECU upgrade for a follow up pass. The top run is corrected - the bottom run is uncorrected. Not sure what their correction factors were….Anyhow, the runs were both done in 5th gear and the diff was unchanged for both runs.







Bottom line…

I will never know what power the cams added to my M6 since a proper baseline Dyno run was never done before the install. I figured that since a baseline was done months ago, there wouldn’t have been a need for another. If I knew that the rear diff upgrade and gear selection would have skewed the results like it did, I would have baselined the car – no questions asked.

So. The big question…

If my car was baselined properly, would the cams have shown power increase? My educated guess……I think the power would be close to the same on the top (maybe a small increase) with a loss in the mid range and lower rpm. But the gears may be throwing my projections off more than I know.

Could my car have made an additional 8-12 whp with the cams somewhere in the upper RPM band as Kelleners suggests? Yes. It is possible after reviewing the dyno graphs. Or…on the other hand, could the cams have caused a loss in power on the top or not have made any power at all? ……………This is also possible.

Bottom line, I’ll never know. (If you guys see something I don’t, let me know.)


***************************************************
***************************************************

NEXT Topic: Supersprint Resonator & Supersprint Sport Mufflers.
(Supersprint Resonator is the Supersprint X-Pipe with a high flow Supersprint resonator)

Why I chose these components: I chose this setup to reap the benefits of higher horsepower with a quieter more reasonable exhaust tone.

Many members on the board have pointed out that cat back exhaust systems for the e60/e63 M5 and M6 do not produce any power and if they do the gains are negligible. This is likely due to the fact that the factory header is too restrictive to allow the rear section of the exhaust to become a bottle neck. But once the factory headers and catalytic converters are substituted for higher flow Supersprint headers and cats will the factory rear section of the exhaust be efficient enough to flow the air?

I baselined the car with the following in (4th gear):

Carbon air filters removed
K & N stock filter replacement
Supersprint Headers
Supersprint Cats
AA Cam ECU Tune
3.91 Dinan Differential
Schrick Kelleners cams


The average run produced 451.98 whp

I then added the SS Resonator and Sport Mufflers (no other changes to the car) and ran a dyno pass again in (4th gear as well) The average run produced 459.34 whp

RESULT: 7.5 whp gain
ACTUAL gain to the engine/crank: 9 hp gain

After examining the dyno charts, there were areas in the power band that showed as much as a 10 whp gain on the top and other areas in the lower portion of the RPM band showed a 5 whp gain.

Here is the dyno chart:




_________________________________________________________________


Here are some video links to some footage after the car was returned with the cams and exhaust:

Video1)
M6 Dyno Run after all work was complete:
http://www.youtube.com/watch?v=D8lPVH7D2Ng

Video 2)
Close up of the Dyno Pass Results with Dinan 3.91 Compromising the HP output
http://www.youtube.com/watch?v=i5ikTEcbBfI

Video 3)
Later that day, M6s owned by ReconM6, NobleCasa, & Keithta Meet off the Highway: http://www.youtube.com/watch?v=QmdB2oLFZL0

Video 4)
ReconM6 Takes off from 75 mph
http://www.youtube.com/watch?v=7n_PGxbFz4M

Video 5)
Stock 2006 M6 with Carbon Air Filters Removed vs. 2006 M6 Modified after cams and full SS exhaust:
(Night video)

(M6 being filmed is completely stock with the carbon air filters removed which adds 7 hp. The video is shot from an M6 that has the Carbon Air Filters removed as well, but also has K & N Air Filters, Supersprint headers, Supersprint high flow cats, Supersprint Resonated X-Pipe, Supersprint Sport Mufflers, Dinan 3.91 Differential, Active Autowerke ECU, & Kelleners/Schrick Cam Shafts.)

The difference between the 2 cars in approx. 53 HP

507 HP vs. 560 HP

Race is from 2nd gear at from 50 mph - 160 mph. The 507 HP M6 lets off the throttle during the final part of the race due to a car ahead.


http://www.youtube.com/watch?v=ivQ-nb1J9IY

Video 6)
My M6 w/ Supersprint Headers, Cats, Resonator, & Sport Mufflers
http://www.youtube.com/watch?v=8iG02SZT6TA

Video 7)
1st BMW M6 Full Throttle Drive By with Supersprint Exhaust
http://www.youtube.com/watch?v=W5zT1jcZwI8

Video 8)
2nd BMW M6 Full Throttle Drive By with Supersprint Exhaust
http://www.youtube.com/watch?v=wD-xF66vQzU


That’s all for now…

** Anyone out there reading this thread that has a good amount of experience with dyno runs. I have a request. Based on the information I provided, Id like to get some feedback as to whether or not you feel the cams were beneficial or if they were counter productive.
 
#24 ·
I agree with Keith about gear set have effect of dyno horse power number. I had base line on my E46 M3 @ 270whp then upgraded Supersprint header, the dyno came out to be 300whp. After that I put on "3.91 gear set", Delage Air box, reprogram ECU and Schrick cams and number was 310whp. Now 310whp is consider very low for the upgrades. Other 3 cars with same upgrades was show 325whp with similar base line number. BUT they all did not have 3.91 gear set.

I had sold the car for a while now and puzzled why my dyno number was low. Now after I read this post I totally uderstand and agree 100% that change gear ratio does have effect on dyno numbers. Some should dyno an E60 M5 before and after 3.91 and see what kind of difference does it make on the dyno.

Good luck to Keith, I can't wait to get my SS header. But I kinda want to wait and see more company offer ECU tunning solutions first.
 
#25 ·
Keith,

Thanks a million for the in-depth write-up. I feel bad for you with all the money you invested into your car to have only the modest gains you are showing. Good luck. I hope you are able to get something out of your beast for all the money you invested. My question is (and I hope for an honest answer)--Do you feel the full Kelleners tune with a set of evosport headers would be worth the money?
 
#26 ·
One thing every ///M car has in common.. is that investing alot of money is not going to buy you alot of HP, unless the money goes into Forced induction

Im really sorry for all the money spent and dismal resaults..

A respectible (not to all though) German tuner told me last summer (in person) that the V10 was producing around 515-530hp stock on most dynos, and what Tuners tend to do is to mess around with the air temp and humidity in the facility to try to get the dyno to show 507 (or there about), then they would do another dyno with optimal conditions and their stuff installed, showing a result that is faar better than what the actual equipment is showing.

Forced induction cars can be tuned with ease, but NA BMW M motors were usually producing peek HP unless you were willing to spend serious money.

An exhaust will give you sound, headers can give you better midrange torque, but usually you just get a different soundtrack. For serious HP gains you need to force air into the Sxx motor, or you need to do some serious internal work.

just my 2cents.
 
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