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      06-05-2010, 08:04 AM   #1
e.n335
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Muffler(s) - axleback exhausts

Hi,

Is it simply a fact that you can gain max. 5 whp by doing a muffler / axleback upgrade ? Is it all about sound and weight ?

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      06-05-2010, 08:11 AM   #2
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There are all kinds of different claims on this board. If I was you I'd just be doing it for sound. Even the minor amount of weight is insignificant. If you do a full system, I'm sure you pick up some good power by eliminating the cats, and then you have more weight involved, so if you combine that with other weight saving mods there will be an advantage.
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      06-05-2010, 08:15 AM   #3
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Even Akrapovic says 3 hp for the axleback ...
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      06-05-2010, 08:23 AM   #4
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Gintani is in the +10 range for just the axle back. I think most would agree Gintani generates the most HP for just an axle back.
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      06-05-2010, 08:29 AM   #5
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Quote:
Originally Posted by AMPowerJ View Post
Gintani is in the +10 range for just the axle back. I think most would agree Gintani generates the most HP for just an axle back.
Eisenmann Race claimed 16hp. IND posted a thread about this awhile back. But it's easy to have +/- a few hp depending on the car and the dyno and a bunch of other stuff so you can't really say definite which produces more hp when there's only a few hp difference to begin with.
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      06-05-2010, 08:38 AM   #6
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Now, Remus is claiming 10 hp with the sport-version. Akrapovic 3 hp. Both street legal. Is this something feasible ? hmm ...
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      06-05-2010, 08:55 AM   #7
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I agree it's mostly about the sound. If you add up all the gains you get from bolt ons there will be some difference. I think everyone would agree that the fact that bolt ons only net you so much gains speaks volumes about how well tuned the M3 is from the factory.
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      06-09-2010, 01:24 PM   #8
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Quote:
Originally Posted by e.n335 View Post
Even Akrapovic says 3 hp for the axleback ...
That's a manufacturer's claim. 3 hp sounds honest though at least.

Quote:
Originally Posted by AMPowerJ View Post
Gintani is in the +10 range for just the axle back. I think most would agree Gintani generates the most HP for just an axle back.
With exhausts and intakes, it's really hard to measure gains since the conditions all come into effect on the numbers.

With just the axle back, you're not going to feel it like you would with a HFC upgrade and etc.
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      06-09-2010, 03:38 PM   #9
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yea, you won't notice the gains with just a rear section (mufflers)...I have Dinan rear mufflers and the MS filter. I just ran my car on a dynojet (w/sae correction) and it registered 341whp. That seems to be about 5-10 more hp than stock M3's. So, I guess there are some gains there, but so small that you can't notice. It's all for sound really...
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      06-11-2010, 03:12 PM   #10
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Quote:
Originally Posted by Fen335i View Post
yea, you won't notice the gains with just a rear section (mufflers)...I have Dinan rear mufflers and the MS filter. I just ran my car on a dynojet (w/sae correction) and it registered 341whp. That seems to be about 5-10 more hp than stock M3's. So, I guess there are some gains there, but so small that you can't notice. It's all for sound really...
Good to know, thanks. It confirms the current power claims as well. So, on the exhaust side, it's all about catalysts.
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      06-11-2010, 04:24 PM   #11
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I dyno'd my car with filter and stock exhaust, then with filter and eisemann race. First 3 runs lost 2-3whp...next 3 runs gained a few
Below is max gain run, some decent torque gains thou
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Last edited by TheKosherStogie; 06-11-2010 at 10:40 PM.
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      06-12-2010, 02:33 AM   #12
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I had Remus sport and I couldn't feel a thing, just drone in the base of my balls

all the axel back will do is reduce around 60% back pressure, so Remus claims.

HFCs and resonators on their own generate around 15whp
I would guess that the only real gain with axel back will be Felt once the restrictions with oem cats is removed?

I wouldn't believe any claims over 3hp which akra claims.
Since this is proably the best crafted exhaust, I find it hard to believe any other could generate more power.

Burt, any comments?
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      06-12-2010, 03:04 AM   #13
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Considering there is at least 1 supercharged car making 560rwhp through the stock muffler (with no cats) I would say axle backs offer no gains other than the gain of sounding great.
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      06-12-2010, 03:45 AM   #14
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Quote:
Originally Posted by FStop7 View Post
Considering there is at least 1 supercharged car making 560rwhp through the stock muffler (with no cats) I would say axle backs offer no gains other than the gain of sounding great.
i believe drew made more power with the aftermarket muffler but kept the stock muffler on because he didnt want it to be loud.
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      06-12-2010, 03:47 AM   #15
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Quote:
Originally Posted by Bob MG View Post

I wouldn't believe any claims over 3hp which akra claims.
Since this is proably the best crafted exhaust, I find it hard to believe any other could generate more power.

Burt, any comments?
i would disagree just because the Akra muffler is super quiet, so maybe whatever design and insulation they used kept noise and power gains down, due to more restrictive flow
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      06-12-2010, 04:19 AM   #16
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Quote:
Originally Posted by sammyrusso View Post
i would disagree just because the Akra muffler is super quiet, so maybe whatever design and insulation they used kept noise and power gains down, due to more restrictive flow
Or they may just give the minimum gain?

The full system delivers at least what they claim when tested fairly and consistently.

Rear Mufflers definately do something as soon as you fit them as you can see the fuel trims change.

Basically - you can get a short period where the engine will run slightly leaner and give that little more power.

The interesting thing to note here is the following:

Stock car averages 335RWHP
Add Axle Back and you get around 340RWHP

If we leave the rear section stock and use an X-Pipe from Akra, AA or our own we see 360+RWHP.

SO you would expect that if we add an axle back now we should see another 5-10RWHP.

We get very very little every single time. We haven't carried out this test just once either!

To sum it up, we have cars running full system and we have some running just decat/x-pipes. They make roughly the same power.

From this you can make your own conclusion.

Bare in mind that we would love to say that axle back systems consistently make much more power as we would sell more. However, the results are very inconsistent (fuel trims) and therefore we cannot make this statement.
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      06-12-2010, 01:03 PM   #17
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^ cant argue w/ that i guess
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      06-12-2010, 01:31 PM   #18
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Moral of the story: Don't get an axle back if you're looking for HP gains.
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