What do you guys think of this exhaust idea?
What do you guys think of this exhaust idea? I’ve been thinking about doing this here lately. Right now I have a single 3” from my turbo that splits off to two 2.5” pipes (slp loudmouth with a magnaflow muffler instead of the bullets) and exiting out the back. Probably restrictive for a turbo exhaust. Here’s my plan:
3” from turbo to a nice high flow but quiet muffler, then after the muffler step it up to 3.5” right before the rear end. Then exit out as one pipe in 3.5”. BUT..... on the down pipe put a 3” cut out and route the pipe from the cutout to merge into the 3.5” pipe. Why?
1) Because I’d rather not have a cutout rattle the **** out of my car
2) it would be similar to a dual mode exhaust that I could change how loud it is
3) I think it would sound better and pick up powa!
3” from turbo to a nice high flow but quiet muffler, then after the muffler step it up to 3.5” right before the rear end. Then exit out as one pipe in 3.5”. BUT..... on the down pipe put a 3” cut out and route the pipe from the cutout to merge into the 3.5” pipe. Why?
1) Because I’d rather not have a cutout rattle the **** out of my car
2) it would be similar to a dual mode exhaust that I could change how loud it is
3) I think it would sound better and pick up powa!
TECH Apprentice
Joined: Apr 2012
Posts: 333
Likes: 4
From: New Zealand
Nicely made exhaust, how much power are you wanting to make? I think if you are happy in the 500's at the wheels what you have will get the job done.
That cross over needs heat shielding or you will over heat the power steering. Ask me how I know that? lol I've had to add a power steering oil cooler on mine and my turbos are out back. Power makes heat and the Commodores/GTO's power steering is a weak link. Looks like you could run a sleeve and lose a bit of heat soak into the bellhousing/back of block as well.
The muffler is the restriction, so if you want to go to 3.5" you should do it as soon as you have room and run a 3.5" muffler straight through design and get one as long as you can fit if you want it quiet. They need volume to reduce noise, so a 3.5" long bullet would be too skinny to meet your noise requirements. An alternative if you can't get long ones is to run 2, a mid and a rear, the important thing is they are free flowing (smooth walled inside not ribbed) and match the pipe size. Stepping up after muffler helps flow, reduces velocity, but again the muffler is the choke point so no advantage IMO
That cross over needs heat shielding or you will over heat the power steering. Ask me how I know that? lol I've had to add a power steering oil cooler on mine and my turbos are out back. Power makes heat and the Commodores/GTO's power steering is a weak link. Looks like you could run a sleeve and lose a bit of heat soak into the bellhousing/back of block as well.
The muffler is the restriction, so if you want to go to 3.5" you should do it as soon as you have room and run a 3.5" muffler straight through design and get one as long as you can fit if you want it quiet. They need volume to reduce noise, so a 3.5" long bullet would be too skinny to meet your noise requirements. An alternative if you can't get long ones is to run 2, a mid and a rear, the important thing is they are free flowing (smooth walled inside not ribbed) and match the pipe size. Stepping up after muffler helps flow, reduces velocity, but again the muffler is the choke point so no advantage IMO
Nicely made exhaust, how much power are you wanting to make? I think if you are happy in the 500's at the wheels what you have will get the job done.
That cross over needs heat shielding or you will over heat the power steering. Ask me how I know that? lol I've had to add a power steering oil cooler on mine and my turbos are out back. Power makes heat and the Commodores/GTO's power steering is a weak link. Looks like you could run a sleeve and lose a bit of heat soak into the bellhousing/back of block as well.
The muffler is the restriction, so if you want to go to 3.5" you should do it as soon as you have room and run a 3.5" muffler straight through design and get one as long as you can fit if you want it quiet. They need volume to reduce noise, so a 3.5" long bullet would be too skinny to meet your noise requirements. An alternative if you can't get long ones is to run 2, a mid and a rear, the important thing is they are free flowing (smooth walled inside not ribbed) and match the pipe size. Stepping up after muffler helps flow, reduces velocity, but again the muffler is the choke point so no advantage IMO
That cross over needs heat shielding or you will over heat the power steering. Ask me how I know that? lol I've had to add a power steering oil cooler on mine and my turbos are out back. Power makes heat and the Commodores/GTO's power steering is a weak link. Looks like you could run a sleeve and lose a bit of heat soak into the bellhousing/back of block as well.
The muffler is the restriction, so if you want to go to 3.5" you should do it as soon as you have room and run a 3.5" muffler straight through design and get one as long as you can fit if you want it quiet. They need volume to reduce noise, so a 3.5" long bullet would be too skinny to meet your noise requirements. An alternative if you can't get long ones is to run 2, a mid and a rear, the important thing is they are free flowing (smooth walled inside not ribbed) and match the pipe size. Stepping up after muffler helps flow, reduces velocity, but again the muffler is the choke point so no advantage IMO
the rack has a heat shield on it. Look closely and you’ll see it. The pipe has a good gap from the tras also. After an hour drive I can dip my finger in the fluid reservoir and it doesn’t burn me. I figure there’s not much more heat in the trans from the pipe running like that because my trans fluid temps are the same as they were and so are engine temps. I’ve akready taken it on a road trip and no issues. I am under it at least once a week checking things out and all seems good. I’ll keep it as is because I purposely tried to avoid wrap in areas that could soak up oil from any sort of fluid leak that could potentially catch fire. I’ve seen this first hand. Trans Fluid was soaking into my buddies header wrap and caught the car on fire. If you have a drip leak you’ll smell it before it has a chance to puddle and catch fire (my theory anyways).
The reason for tge step step up in pipe size after the muffler would be in theory, to have a freer flowing path that the cutout pipe would dump into. It’s basically like bypassing the muffler.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
I'd rather see a 3.5" DP or front section than stepping up at the rear after the smaller 3" DP. Although do appreciate space may be tight up front but that is exactly where you want the larger section.
Holdener did a test a while back on the dyno where a full 3" system vs a 4" open pipe...and really there was only around 70hp difference. Something like 846 vs 919 or so ?
Really, you'd have thought a full 3" system would have done far worse ! but it was free power everywhere, and only a 12psi run, so not exactly a crazy build or anything.
Holdener did a test a while back on the dyno where a full 3" system vs a 4" open pipe...and really there was only around 70hp difference. Something like 846 vs 919 or so ?
Really, you'd have thought a full 3" system would have done far worse ! but it was free power everywhere, and only a 12psi run, so not exactly a crazy build or anything.
I'd rather see a 3.5" DP or front section than stepping up at the rear after the smaller 3" DP. Although do appreciate space may be tight up front but that is exactly where you want the larger section.
Holdener did a test a while back on the dyno where a full 3" system vs a 4" open pipe...and really there was only around 70hp difference. Something like 846 vs 919 or so ?
Really, you'd have thought a full 3" system would have done far worse ! but it was free power everywhere, and only a 12psi run, so not exactly a crazy build or anything.
https://www.instagram.com/p/BnG2eCNg...ichardholdener
Holdener did a test a while back on the dyno where a full 3" system vs a 4" open pipe...and really there was only around 70hp difference. Something like 846 vs 919 or so ?
Really, you'd have thought a full 3" system would have done far worse ! but it was free power everywhere, and only a 12psi run, so not exactly a crazy build or anything.
https://www.instagram.com/p/BnG2eCNg...ichardholdener
well all I am considering a 3.5” oval down pipe
TECH Apprentice
Joined: Apr 2012
Posts: 333
Likes: 4
From: New Zealand
I agree with Stevie, if you can fit that 3.5" oval up front do that first.
I hear you re the oil/fire - I track my car and do closed road events so the heat issue is far bigger than anything I have encountered on the street - it's night and day - esp hot lapping.
The sleeve material I will use on upgrading will be fire retarding.
Reminds me of a funny story when I took my then girlfriend out for a few laps. She had never been around a track before, and had never been in a 780hp car. Into the 1st lap 2 loud F's were given, and then on the 5th lap she called out a 3rd F bomb. The 1st was when I floored it, the 2nd was when I braked, and the 3rd was when we caught fire. Hahaha. There was a cloud of smoke behind me (which is never a thing to bring a smile) and luckily I was approaching the exit so pulled in. Thought it was power steering oil, turned out to be a leaking clutch cable, lucky it was just smoke and it had burned off by the time I pulled in and shut down lolz. We drove home and she loved it.
I hear you re the oil/fire - I track my car and do closed road events so the heat issue is far bigger than anything I have encountered on the street - it's night and day - esp hot lapping.
The sleeve material I will use on upgrading will be fire retarding.
Reminds me of a funny story when I took my then girlfriend out for a few laps. She had never been around a track before, and had never been in a 780hp car. Into the 1st lap 2 loud F's were given, and then on the 5th lap she called out a 3rd F bomb. The 1st was when I floored it, the 2nd was when I braked, and the 3rd was when we caught fire. Hahaha. There was a cloud of smoke behind me (which is never a thing to bring a smile) and luckily I was approaching the exit so pulled in. Thought it was power steering oil, turned out to be a leaking clutch cable, lucky it was just smoke and it had burned off by the time I pulled in and shut down lolz. We drove home and she loved it.
