Akrapovic Review

[mixja]

Had this installed a couple of days ago...construction is of extremely high quality.

The sound of this exhaust is very good for a full system - it is louder obviously than stock, but perhaps only 20% or so louder at full throttle and higher RPMs. The system does drone a little bit up to around 2500rpm, but the level of drone is very much related to how much throttle you are applying so it can be controlled. The good thing is that there are no specific RPMs where there is significantly more drone - unlike what I got with AA X-Pipe + Factory Exhaust, where it would resonate loudly and drone at 2500RPM, 3000RPM and 4000RPM.

That said, I do still prefer the stock exhaust sound of the M3 - it is very civilised, refined and has character - which I feel very much matches the nature of this car. I think with any aftermarket exhaust system, not just Akrapovic, that refinement tends to get lost particularly at lower RPMs where the exhaust sounds more agricultural and brutish.

Performance wise, the exhaust system definitely feels like it lives up to its claims of +24HP and +35NM. Using hand-timed performance measurements over various speed ranges, there is improvement of between 6-10%. Also on the track, my car with Powerchip Stage II, AA Pulley, Air Filter, Scoops and Akrapovic Exhaust was able to keep even pace with an M6 (and slightly quicker than an M5) on a straight where the vehicles accelerated from ~40MPH to ~140MPH.

Only downsides I'd suggest are potentially the look of the exhaust - the tips are quite big and really do stand out - no stealth here. Some may like this but not really me. Also the gold/bronze color of the exhaust probably doesn't really go too well with the color of my car (Moonstone), but again subjective.

[Nawaaz]

Good review. It will help many who are looking for a full exhaust system that does not eliminate all the cats, makes great power, isn't too loud, and is made of outstanding quality.

Thanks man!

[CSanto]

Awesome Review, I love hearing peoples unbiased opinion.

[Donbona]

Good review.. I agree on some points but I love the sound much more than the stock...
As for the tailpipes... check the image attatched... I burnt them myself....

Originally Posted by mixja

Had this installed a couple of days ago...construction is of extremely high quality.

The sound of this exhaust is very good for a full system - it is louder obviously than stock, but perhaps only 20% or so louder at full throttle and higher RPMs. The system does drone a little bit up to around 2500rpm, but the level of drone is very much related to how much throttle you are applying so it can be controlled. The good thing is that there are no specific RPMs where there is significantly more drone - unlike what I got with AA X-Pipe + Factory Exhaust, where it would resonate loudly and drone at 2500RPM, 3000RPM and 4000RPM.

That said, I do still prefer the stock exhaust sound of the M3 - it is very civilised, refined and has character - which I feel very much matches the nature of this car. I think with any aftermarket exhaust system, not just Akrapovic, that refinement tends to get lost particularly at lower RPMs where the exhaust sounds more agricultural and brutish.

Performance wise, the exhaust system definitely feels like it lives up to its claims of +24HP and +35NM. Using hand-timed performance measurements over various speed ranges, there is improvement of between 6-10%. Also on the track, my car with Powerchip Stage II, AA Pulley, Air Filter, Scoops and Akrapovic Exhaust was able to keep even pace with an M6 (and slightly quicker than an M5) on a straight where the vehicles accelerated from ~40MPH to ~140MPH.

Only downsides I'd suggest are potentially the look of the exhaust - the tips are quite big and really do stand out - no stealth here. Some may like this but not really me. Also the gold/bronze color of the exhaust probably doesn't really go too well with the color of my car (Moonstone), but again subjective.

[BMW-Motorsport]

Originally Posted by mixja

Had this installed a couple of days ago...construction is of extremely high quality.

The sound of this exhaust is very good for a full system - it is louder obviously than stock, but perhaps only 20% or so louder at full throttle and higher RPMs. The system does drone a little bit up to around 2500rpm, but the level of drone is very much related to how much throttle you are applying so it can be controlled. The good thing is that there are no specific RPMs where there is significantly more drone - unlike what I got with AA X-Pipe + Factory Exhaust, where it would resonate loudly and drone at 2500RPM, 3000RPM and 4000RPM.

That said, I do still prefer the stock exhaust sound of the M3 - it is very civilised, refined and has character - which I feel very much matches the nature of this car. I think with any aftermarket exhaust system, not just Akrapovic, that refinement tends to get lost particularly at lower RPMs where the exhaust sounds more agricultural and brutish.

Performance wise, the exhaust system definitely feels like it lives up to its claims of +24HP and +35NM. Using hand-timed performance measurements over various speed ranges, there is improvement of between 6-10%. Also on the track, my car with Powerchip Stage II, AA Pulley, Air Filter, Scoops and Akrapovic Exhaust was able to keep even pace with an M6 (and slightly quicker than an M5) on a straight where the vehicles accelerated from ~40MPH to ~140MPH.

Only downsides I'd suggest are potentially the look of the exhaust - the tips are quite big and really do stand out - no stealth here. Some may like this but not really me. Also the gold/bronze color of the exhaust probably doesn't really go too well with the color of my car (Moonstone), but again subjective.

Perhaps you should have gone for just the Akra X-pipe and stock muffler to keep the refinement you are looking for and satisfy your needs.
Ralf from krenzer performance parts did send me these pics two weeks ago - I guess it´s a good option for some of us.

[Brosef]

Originally Posted by mixja

Had this installed a couple of days ago...construction is of extremely high quality.

The sound of this exhaust is very good for a full system - it is louder obviously than stock, but perhaps only 20% or so louder at full throttle and higher RPMs. The system does drone a little bit up to around 2500rpm, but the level of drone is very much related to how much throttle you are applying so it can be controlled. The good thing is that there are no specific RPMs where there is significantly more drone - unlike what I got with AA X-Pipe + Factory Exhaust, where it would resonate loudly and drone at 2500RPM, 3000RPM and 4000RPM.

That said, I do still prefer the stock exhaust sound of the M3 - it is very civilised, refined and has character - which I feel very much matches the nature of this car. I think with any aftermarket exhaust system, not just Akrapovic, that refinement tends to get lost particularly at lower RPMs where the exhaust sounds more agricultural and brutish.

Performance wise, the exhaust system definitely feels like it lives up to its claims of +24HP and +35NM. Using hand-timed performance measurements over various speed ranges, there is improvement of between 6-10%. Also on the track, my car with Powerchip Stage II, AA Pulley, Air Filter, Scoops and Akrapovic Exhaust was able to keep even pace with an M6 (and slightly quicker than an M5) on a straight where the vehicles accelerated from ~40MPH to ~140MPH.

Only downsides I'd suggest are potentially the look of the exhaust - the tips are quite big and really do stand out - no stealth here. Some may like this but not really me. Also the gold/bronze color of the exhaust probably doesn't really go too well with the color of my car (Moonstone), but again subjective.

Excellent review.

[michaeldorian]

Originally Posted by BMW-Motorsport

Perhaps you should have gone for just the Akra X-pipe and stock muffler to keep the refinement you are looking for and satisfy your needs.
Ralf from krenzer performance parts did send me these pics two weeks ago - I guess it´s a good option for some of us.

This is interesting! Thanks for the update. I think this is definately an option. I wonder how much it affects the sourd. Do you know the cost?

[mixja]

Originally Posted by michaeldorian

This is interesting! Thanks for the update. I think this is definately an option. I wonder how much it affects the sourd. Do you know the cost?

Akrapovic don't sell just the down pipes - officially anyway. I wasn't able to - I've actually decided to only use this exhaust for track days etc as it's still too loud for my family so I put the stock exhaust back on today.

There are adapters you can get I believe that allow you to mate the Akrapovic X-Pipe section with the factory muffler...I may try this...

Here are pictures of the system off just three days later (and one track session later )

[mixja]

One thing I forgot to mention in the review was that the Akrapovic exhaust does cause a dip in low RPM torque (from around 1500-3000RPM).

Although I wouldn't take the comparisons below from my iPhone as gospel they do illustrate the differences in power delivery between stock system and Akrapovic system.

Stock System:
- Both runs are from a standard start in 2nd gear (DCT) in S5
- Blue line is acceleration in G's (i.e. proportional to torque)
- On this run the car made 298WHP (note my test track is on a small incline, so don't take these results as absolute)
- Peak G's on stock system were 0.48G
- Air temperature was around 12.0C
- Ignore the power bump at the end - this is DCT surge on change from 2nd to 3rd gear - so only look at the point up to where the car makes just under 300WHP


Akrapovic System:
- On this run the car made 313WHP
- Peak G's on Akrapovic system were 0.50G
- Air temperature was around 14.5C


Comparing the Two:
- Stock system has more low RPM torque and smoother acceleration (stock speed plot is almost linear, where as Akrapovic speed plot has a curve to it).
- I'd suggest the stock exhaust system is making more torque up until around 3500RPM.
- On Akrapovic Mid to High RPM acceleration is definitely stronger, hence the higher power result
- Note the dip on the Akrapovic system, which is around 6000RPM

[ching]

You intend to switch exhausts every time you go to the track? That's got to get old real fast. Sounds like time for a dedicated track car!

[stylinexpat]

I wonder if a custom tune would sort these dips and power losses out. Was supposed to get an answer from this from ESS but never did. Would have been nice to see a Dyno graph from ESS or some other tuner on this.

[Lemans_Blue_M]

Originally Posted by stylinexpat

I wonder if a custom tune would sort these dips and power losses out. Was supposed to get an answer from this from ESS but never did. Would have been nice to see a Dyno graph from ESS or some other tuner on this.

Nope...

The dip can be slightly minimized through custom software tuning, (to a certain extent) but not completely eliminated.

The increased exhaust flow from all the aftermarket exhaust configurations on the market, will only make the low-rpm dip more pronounced. (vs. stock)

This issue cannot be 'solved' through any software ECU tweaking. It's a flow vs. back pressure reality of the S65B40 V8 engine. (with the stock headers)

The only thing that may actually eliminate this low rpm dip...is a set of custom tuned exhaust headers. AFAIK only RD Sport and one other company (whose name escapes me at the moment) make an aftermarket version for the M3. (because the stock headers flow so well)

Aftermarket exhaust headers are the only exhaust hardware component that hasn't been changed out by anyone to date. (unless I missed the thread?)

A nice long tube exhaust header may erase this dip. And even that might not work...

It seems that every conceivable exhaust configuration (from the header output flange back) has the dreaded low-rpm dip in the dyno graph.

In fact, the custom ECU tune thread about Powerchip software shows the same low-rpm dip as well:

http://www.m3post.com/forums/showpos...42&postcount=1

[sales@ESSTuning]

Originally Posted by stylinexpat

I wonder if a custom tune would sort these dips and power losses out. Was supposed to get an answer from this from ESS but never did. Would have been nice to see a Dyno graph from ESS or some other tuner on this.

With all the data we collected from the local car we tested we believe the issue is caused by something not related to backpressure or AFR's. Before we had a chance to spend some time with the car and work on a fix the customer sold the exhaust system. The dyno below shows where the dip in power occurs with the exhaust system. The exhaust is very good thru the mid range and up top and the build quality it top notch.

[mixja]

Originally Posted by Rom3n

With all the data we collected from the local car we tested we believe the issue is caused by something not related to backpressure or AFR's. Before we had a chance to spend some time with the car and work on a fix the customer sold the exhaust system. The dyno below shows where the dip in power occurs with the exhaust system. The exhaust is very good thru the mid range and up top and the build quality it top notch.

So what could it be caused by then?

Over scavenging (which I'd guess could be caused by decreased backpressure) - meaning an adjustment in valve timing is needed?

[mixja]

Originally Posted by ching

You intend to switch exhausts every time you go to the track? That's got to get old real fast. Sounds like time for a dedicated track car!

Not really, turn around time is half a day and I only get charged for a couple of hours labour...this system doesn't have bad drone but even so stock exhaust is a better daily driver, which is what I do 99% of the time...

[BMW-Motorsport]

Originally Posted by michaeldorian

This is interesting! Thanks for the update. I think this is definately an option. I wonder how much it affects the sourd. Do you know the cost?

I guess he sells it for around 2k Euros, but I don´t remember exactly.

[datbimmerdoe]

Great review!