Well, I finally broke down and bought a 3" exhaust system. After hearing the ear splitting LOUD sound levels of the 3" exhausts available from various DSM vendors, I decided to purchase the Thermal R&D 3" 2g AWD catback exhaust system. I based this decision on Thermal's strong reputation for build quality and refined sound. Since I also wanted a whisper quiet exhaust, I decided to cut the B-pipe in half and welded a Borla muffler (P/N 40085, 5" O.D. x 15" Long S.S.) in place. I'm currently running a 2.5" downpipe & testpipe with the new catback.
Installation:
The stock unmodified Thermal R&D 2g AWD catback exhaust is a cinch to install. The exception is that the rear 3" 3-bolt flanges allow no room for a socket. Trying to turn a long wrench on the bolt near the top of the flange near the chassis underbody was near impossible. I suggest bolting together the full exhaust off the car. Then sliding it into position and mounting the muffler hangers first. Then the 2 cat flange hangers and finally the B-midpipe hanger last. Because my exhaust is modified and has a Borla muffler welded into the midpipe, I needed to make 2 modifications. The first was to grind down the carrier bearing mounting stud on the drivers side. This was too long and was hitting the Borla muffler. The second problem was the way I positioned my Borla muffler. It was real close to hitting the carrier bearing steel housing. To solve this I just cut a 4" strip of textured vinyl/rubber sheetmetal edging (McMaster Carr) and pushed it onto the lip of the carrier bearing housing. If the exhaust sways it will just bounce of that soft edging. Clearance around the heatshields is actually perfect for my Borla 5" O.D. muffler and the entire exhaust sits real tight and close to the underbody.
Sound:
Man, shouldn't this thing be louder? I was looking forward to intimidating people with this exhaust but it sounds stock, with just a lower bass tone and a touch of drone at 3000 rpm. I could hear it getting quieter as I drove it. Perhaps the exhaust soot build up on the inside of the pipes & the muffler packing heating up helped quiet things down a bit.
I've heard the popular DSM vendor brand 3" exhausts and they sound disgusting when free revved in neutral. Those exhausts produce lots of popping on deceleration, resonances, raspyness, and just overall high decibel levels. This modified Thermal R&D exhaust on the other hand when free revved sounds like a stock exhaust with the cat removed. I was expecting LOUD and was completely shocked when I first started my car. You can hear the intake and all the little mechanical engine noises with almost no exhaust booming, no raspyness, & no resonances whatsoever. The downside of 3" pipework is a constant drone at 3000 rpm. Idling is pretty quiet and WOT runs are no louder than my Greddy SP 60mm catback. Overall, the exhaust sounds great and much closer in sound quality to the stock exhaust or Greddy SP catback when revved. Remember, an unmodified Thermal R&D exhaust will sound deeper and a littler louder if your into that sort of thing. If I wanted a completely silent exhaust I could always drop in a high flow 3" cat.
Power:
Low end torque seems to be completely unaffected. This thing about big exhausts causing low end torque loss is TOTAL bullshit. I can leave the line at part throttle and pull away with ease, same as before. Part throttle power is a good bit better above 4000 rpm. The maximum power output increase at WOT is hard to tell. I was VERY close to maxing out my turbo before the 3" exhaust install. I am however getting a very hard hit of power at WOT 4500 rpm that wasn't as noticeable before the catback install, especially in 3rd gear. The hit of torque is almost annoying now, as hard to believe as that sounds. This is in addition to running a T28, HKS cams, FMIC, VPC, etc. and almost every bolt on available. I've yet to do a datalog on the Thermal R&D catback to compare the horsepower and torque curves but will post results later when I get the chance. Spool up looks to be a touch better than the Greddy SP 60 mm catback exhaust but barely. The biggest difference though is that at highway speeds I need much less throttle or boost to get the car moving fast as compared to before with the Greddy SP 60 mm catback. I'd have to say driveability is much better, especially at highway speeds.
Specifications:
The Thermal weighs about 23.5 lbs stock, with my Borla muffler/resonator added in place it weighs 28.5 lbs. The cat flange measures 2.25" I.D. and is very close to the 2.375" I.D. of a 2.5" O.D. exhaust tube. So the neck down is fairly minor for somebody already running a 2.5" downpipe/testpipe. All bends are mandrel bent and the tube diameter is 3" O.D. and 2.875" I.D. accept as noted above. All tubes, mufflers, welds, hangers are mirror polished T304 stainless steel. The cat flange is stainless or a nonmagnetic steel, the 2 muffler pipe flanges are mild steel, the 02 bung is mild steel too. The muffler tip is dual wall stainless with a 5" O.D. and 3.75" I.D. with a nice Thermal R&D logo on the top. This may be the straightest exhaust system I've ever seen. All of the combined small angle bends total about 90*, from the cat to the muffler tip. The fit is absolutely perfect, no rubbing or hitting anything under WOT or idle. Both the Thermal R&D and Borla mufflers are 3" I.D. straight thru perforated core mufflers with NO neck downs internally.
The Thermal R&D muffler canister is pretty damned big for a round muffler, 7.3" O.D. and 16" long. There is a reason the Thermals are said to be quiet and its the muffler volume that does that. A good rule of thumb for MINIMUM total muffler silencer volume is 10-15 times 1 cylinder volume (i.e 30 cubic inches). The total volume of both mufflers on my exhaust is 748 cubic inches, thats what makes it as quiet as a stock exhaust with no cat. The stock unmodified Thermal R&D muffler has 560 cubic inches of volume. An Apexi N1 on the other hand has a total volume of 508 cubic inches including the muffler & 2 resonators. I highly recommend the Thermal R&D exhaust for 2g AWD owners. If your looking for a real quite 3" exhaust, just modify the catback like I did for great results. Cheers.
Here are a few pics of the modified Thermal R&D 3" exhaust:
Installation:
The stock unmodified Thermal R&D 2g AWD catback exhaust is a cinch to install. The exception is that the rear 3" 3-bolt flanges allow no room for a socket. Trying to turn a long wrench on the bolt near the top of the flange near the chassis underbody was near impossible. I suggest bolting together the full exhaust off the car. Then sliding it into position and mounting the muffler hangers first. Then the 2 cat flange hangers and finally the B-midpipe hanger last. Because my exhaust is modified and has a Borla muffler welded into the midpipe, I needed to make 2 modifications. The first was to grind down the carrier bearing mounting stud on the drivers side. This was too long and was hitting the Borla muffler. The second problem was the way I positioned my Borla muffler. It was real close to hitting the carrier bearing steel housing. To solve this I just cut a 4" strip of textured vinyl/rubber sheetmetal edging (McMaster Carr) and pushed it onto the lip of the carrier bearing housing. If the exhaust sways it will just bounce of that soft edging. Clearance around the heatshields is actually perfect for my Borla 5" O.D. muffler and the entire exhaust sits real tight and close to the underbody.
Sound:
Man, shouldn't this thing be louder? I was looking forward to intimidating people with this exhaust but it sounds stock, with just a lower bass tone and a touch of drone at 3000 rpm. I could hear it getting quieter as I drove it. Perhaps the exhaust soot build up on the inside of the pipes & the muffler packing heating up helped quiet things down a bit.
I've heard the popular DSM vendor brand 3" exhausts and they sound disgusting when free revved in neutral. Those exhausts produce lots of popping on deceleration, resonances, raspyness, and just overall high decibel levels. This modified Thermal R&D exhaust on the other hand when free revved sounds like a stock exhaust with the cat removed. I was expecting LOUD and was completely shocked when I first started my car. You can hear the intake and all the little mechanical engine noises with almost no exhaust booming, no raspyness, & no resonances whatsoever. The downside of 3" pipework is a constant drone at 3000 rpm. Idling is pretty quiet and WOT runs are no louder than my Greddy SP 60mm catback. Overall, the exhaust sounds great and much closer in sound quality to the stock exhaust or Greddy SP catback when revved. Remember, an unmodified Thermal R&D exhaust will sound deeper and a littler louder if your into that sort of thing. If I wanted a completely silent exhaust I could always drop in a high flow 3" cat.
Power:
Low end torque seems to be completely unaffected. This thing about big exhausts causing low end torque loss is TOTAL bullshit. I can leave the line at part throttle and pull away with ease, same as before. Part throttle power is a good bit better above 4000 rpm. The maximum power output increase at WOT is hard to tell. I was VERY close to maxing out my turbo before the 3" exhaust install. I am however getting a very hard hit of power at WOT 4500 rpm that wasn't as noticeable before the catback install, especially in 3rd gear. The hit of torque is almost annoying now, as hard to believe as that sounds. This is in addition to running a T28, HKS cams, FMIC, VPC, etc. and almost every bolt on available. I've yet to do a datalog on the Thermal R&D catback to compare the horsepower and torque curves but will post results later when I get the chance. Spool up looks to be a touch better than the Greddy SP 60 mm catback exhaust but barely. The biggest difference though is that at highway speeds I need much less throttle or boost to get the car moving fast as compared to before with the Greddy SP 60 mm catback. I'd have to say driveability is much better, especially at highway speeds.
Specifications:
The Thermal weighs about 23.5 lbs stock, with my Borla muffler/resonator added in place it weighs 28.5 lbs. The cat flange measures 2.25" I.D. and is very close to the 2.375" I.D. of a 2.5" O.D. exhaust tube. So the neck down is fairly minor for somebody already running a 2.5" downpipe/testpipe. All bends are mandrel bent and the tube diameter is 3" O.D. and 2.875" I.D. accept as noted above. All tubes, mufflers, welds, hangers are mirror polished T304 stainless steel. The cat flange is stainless or a nonmagnetic steel, the 2 muffler pipe flanges are mild steel, the 02 bung is mild steel too. The muffler tip is dual wall stainless with a 5" O.D. and 3.75" I.D. with a nice Thermal R&D logo on the top. This may be the straightest exhaust system I've ever seen. All of the combined small angle bends total about 90*, from the cat to the muffler tip. The fit is absolutely perfect, no rubbing or hitting anything under WOT or idle. Both the Thermal R&D and Borla mufflers are 3" I.D. straight thru perforated core mufflers with NO neck downs internally.
The Thermal R&D muffler canister is pretty damned big for a round muffler, 7.3" O.D. and 16" long. There is a reason the Thermals are said to be quiet and its the muffler volume that does that. A good rule of thumb for MINIMUM total muffler silencer volume is 10-15 times 1 cylinder volume (i.e 30 cubic inches). The total volume of both mufflers on my exhaust is 748 cubic inches, thats what makes it as quiet as a stock exhaust with no cat. The stock unmodified Thermal R&D muffler has 560 cubic inches of volume. An Apexi N1 on the other hand has a total volume of 508 cubic inches including the muffler & 2 resonators. I highly recommend the Thermal R&D exhaust for 2g AWD owners. If your looking for a real quite 3" exhaust, just modify the catback like I did for great results. Cheers.
Here are a few pics of the modified Thermal R&D 3" exhaust:
