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    • Renntech releases Mercedes SLS AMG long tube headers, +20 horsepower, $8200

      Renntech has released their Mercedes SLS AMG long tube headers. They don't come cheap, MSRP being $8200. They seem to be a quality piece that is ceramic coated. Power claims are 20 horsepower and 20 pound-feet of torque but there are no dyno or performance numbers to substantiate any power claims. The headers include 200 cell sport cats and we wonder what the gains and price would be without the integrated cats.


      This article was originally published in forum thread: Renntech releases Mercedes SLS AMG long tube headers, +20 horsepower, $8200 started by Sticky View original post
      Comments 16 Comments
      1. Sorena's Avatar
        Sorena -
        damn ,each HP costs $410 !
      1. Even Money's Avatar
        Even Money -
        LOL......20 hp? Stupid integrated cat. Seriously?
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Even Money Click here to enlarge
        LOL......20 hp? Stupid integrated cat. Seriously?
        They have buyers lined up they say...
      1. 930chas's Avatar
        930chas -
        Click here to enlarge Originally Posted by Even Money Click here to enlarge
        LOL......20 hp? Stupid integrated cat. Seriously?
        x2. That is hilarious.
      1. V12Godspeed's Avatar
        V12Godspeed -
        I am almost certain this brings a pack of lube to go with the installation. Seriously. Click here to enlarge
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by V12Godspeed Click here to enlarge
        I am almost certain this brings a pack of lube to go with the installation. Seriously. Click here to enlarge
        I can't really understand why the price difference would be so much higher than the M156 headers but... it's Renntech.

        People who do not know better will buy it. It definitely will be a quality piece just overpriced compared to what headers for this motor should cost. SLS tax in effect.
      1. MSIZZLE's Avatar
        MSIZZLE -
        guys as i have said before i frequent a race shop and i know what it cost to make things, now i understand because of the price of the car and how rare it is the r&d must cost more money, but that ends after a point!!!i have 4500 evo sport headers in my car and i think thats expensive!!! i know shops that build headers with cad and is able to check the gas flow and temp all on the computer so they dont even need a car to test it or fabricate it
      1. Sonny's Avatar
        Sonny -
        Click here to enlarge Originally Posted by Even Money Click here to enlarge
        LOL......20 hp? Stupid integrated cat. Seriously?
        At first I was like, "well, I can understand for emissions purposes, the integrated cat will serve a purpose." But, then I remembered that if satisfying CARB is their intent, it's violative to even remove the primary cats on a car, so really, like you said, what's the point?
      1. Exeenom's Avatar
        Exeenom -
        Click here to enlarge Originally Posted by Sonny Click here to enlarge
        At first I was like, "well, I can understand for emissions purposes, the integrated cat will serve a purpose." But, then I remembered that if satisfying CARB is their intent, it's violative to even remove the primary cats on a car, so really, like you said, what's the point?
        There are a few reasons to have some type of cats in place (although they may not be best for maximum performance):

        - Going catless on the 6.2L engine makes the exhaust sound way too loud for some people. Having a catalytic converter in place controls some of that sound.
        - Sometimes there is an added gas smell without cats.
        - Maintain some type of back pressure or torque levels.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Exeenom Click here to enlarge
        There are a few reasons to have some type of cats in place (although they may not be best for maximum performance):

        - Going catless on the 6.2L engine makes the exhaust sound way too loud for some people. Having a catalytic converter in place controls some of that sound.
        I would think there are 2 sets of cats? So, even if the cats in the headers are eliminated, there should still be a set downstream?
      1. Sonny's Avatar
        Sonny -
        Click here to enlarge Originally Posted by Exeenom Click here to enlarge
        There are a few reasons to have some type of cats in place (although they may not be best for maximum performance):

        - Going catless on the 6.2L engine makes the exhaust sound way too loud for some people. Having a catalytic converter in place controls some of that sound.
        - Sometimes there is an added gas smell without cats.
        - Maintain some type of back pressure or torque levels.
        Very good points.

        Regarding "going catless making exhaust too loud" I would think adding some resonators would be a better option for reducing sound while maintaining performance benefit from no cats. But, that would still trigger the issue of smell, which many people would not like for DD or at least weekend driving.

        As far as maintaining back pressure goes, I ran a catless setup on my last car for a few weeks (blower, LT's, catback) and when I installed the LT's, which removed the cats, my torque rose. Obviously, that's from the LT's but these are headers for the SLS and I would think torque wouldn't be a problem.

        Anyway, just adding my thoughts. I think you make valid points.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Sonny Click here to enlarge
        As far as maintaining back pressure goes, I ran a catless setup on my last car for a few weeks (blower, LT's, catback) and when I installed the LT's, which removed the cats, my torque rose. Obviously, that's from the LT's but these are headers for the SLS and I would think torque wouldn't be a problem.

        Anyway, just adding my thoughts. I think you make valid points.
        I don't really agree with the backpressure "myth" so to speak. I gained torque going catless as well.
      1. Exeenom's Avatar
        Exeenom -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I would think there are 2 sets of cats? So, even if the cats in the headers are eliminated, there should still be a set downstream?
        On the M113k (E55, CLS55, S55, etc...) and current M156 cars (63 engine), yes there are two sets of cats installed by the factory, but on newer cars, Mercedes seems to have eliminated one set. Either way, I think in order to make the long-tubes long enough (true long-tube design), at least one set of cats have to get eliminated or at least pushed back significantly.

        Click here to enlarge Originally Posted by Sonny Click here to enlarge
        Very good points.

        Regarding "going catless making exhaust too loud" I would think adding some resonators would be a better option for reducing sound while maintaining performance benefit from no cats. But, that would still trigger the issue of smell, which many people would not like for DD or at least weekend driving.
        When these companies design the long-tube headers, they are sometimes forced to replace the resonator with an X-Pipe, an H-Pipe, or even just straight pipes in order to help their design. So having a resonator does not become a suitable option. However, even when they do keep the resonator in place, the resonator usually kills the sound way too much compared to cats - and people almost always want louder sound than the resonator can offer but they do NOT want it too loud (as in the case without cats). That's why the cats are a good compromise: a good set of sport/race cats can lower the sound just slightly and can control smell while giving the car a nice raspy sound and feel. By the way, the smell is not just gas smell, it also contains sulpher and other noticeable smells. I've smelled it many times at the track from standing next to other cars. And you're absolutely right.... a person with a luxury sedan or sports car would not want that smell all the time.

        Click here to enlarge Originally Posted by Sonny Click here to enlarge
        As far as maintaining back pressure goes, I ran a catless setup on my last car for a few weeks (blower, LT's, catback) and when I installed the LT's, which removed the cats, my torque rose. Obviously, that's from the LT's but these are headers for the SLS and I would think torque wouldn't be a problem.
        Anyway, just adding my thoughts. I think you make valid points.
        Thank you... your questions were exactly the same as my questions when I called RENNtech a few months back to inquire about their headers Click here to enlarge

        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I don't really agree with the backpressure "myth" so to speak. I gained torque going catless as well.
        Regarding back pressure, it is very important to get this balanced just right especially on modern cars due to the advanced electronics that are always adjusting and responding to a million other variables in order to protect the car and keep everything in check. There are a couple of members on mbworld with E55s with long-tubes and 200 cell race cats (and even slightly larger exhaust diameter: went from 2.75 to 3.0 inches to further reduce back pressure). Anyways, they wanted to see if they could gain more hp, so they removed the cats all together and ended up losing just over 25 ft-lbs of torque. This was done at a performance shop and was tested immediately on the dyno and then reverse tested with the same results. I'm not sure if this is the case with the M156 engine, but I do know you can lose a good amount of torque (specifically in the lower rpm range) if you remove the cats from E55s/CLS55s.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Exeenom Click here to enlarge
        Anyways, they wanted to see if they could gain more hp, so they removed the cats all together and ended up losing just over 25 ft-lbs of torque. This was done at a performance shop and was tested immediately on the dyno and then reverse tested with the same results. I'm not sure if this is the case with the M156 engine, but I do know you can lose a good amount of torque (specifically in the lower rpm range) if you remove the cats from E55s/CLS55s.
        I'm a bit surprised to see that as the backpressure argument has usually been for NA motors.

        Did the dyno results have their air fuel ratios? I'm wondering if the cars were running super lean and they simply weren't tuned for the missing cats.
      1. Exeenom's Avatar
        Exeenom -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I'm a bit surprised to see that as the backpressure argument has usually been for NA motors.

        Did the dyno results have their air fuel ratios? I'm wondering if the cars were running super lean and they simply weren't tuned for the missing cats.
        No, both cars were not re-tuned. They only tested the with and without cats. They both had pullies, long-tubes, airboxes, and tune to begin with though. I'll go back and check the air fuel ratio, I don't think it changed too much. I think the software adjusted for the change.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Exeenom Click here to enlarge
        No, both cars were not re-tuned. They only tested the with and without cats.
        This is a very large variable. They would need a tune and some time to adapt.

        I just know in my experience, large gains going catless.