Non-Mandrel bends, but larger diameter
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Non-Mandrel bends, but larger diameter Was going to do a 2.5" mandrel bent true dual exhaust, but was thinking about instead doing 3" non mandrel bent true dual exhaust going under the axle. There are many reasons for my idea of doing this, but primarily, I'd like to know whether, in theory, flow would be comparable between these two setups. The shop has a Huth bending machine that makes good clean bends, and since it will be under the axle, the amount of bends will be minimal. From what I hear, a non mandrel bent 3" will flow like a 2.5" so I should be right where I originally wanted to be, right?
This is for a cammed LS1 Camaro btw. I'm not worried about leaving 5hp on the table or so, but if we are talking 5% here, then forget it.
Thanks and sorry for the confusing post.
This is for a cammed LS1 Camaro btw. I'm not worried about leaving 5hp on the table or so, but if we are talking 5% here, then forget it.
Thanks and sorry for the confusing post.
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The key words here are "minimal bends." if thats the case then it wont bother much. if you doing 45-90 degree then...well...
for my reference, i had an exhaust shop do my cat back on my 91 240sx when i was in the drift scene. I gave them a canister and they did the rest. was not mandrel but it was better than stock. again my bends were minimal and 35 degree at most
for my reference, i had an exhaust shop do my cat back on my 91 240sx when i was in the drift scene. I gave them a canister and they did the rest. was not mandrel but it was better than stock. again my bends were minimal and 35 degree at most
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From: Turnin' Wrenches Infractions: 005
You got a solid plan, I say run with it. However, being that I have fabbed up a 3 inch true dual system under the axle I will say it does cut down on ground clearance.
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From: Turnin' Wrenches Infractions: 005
It wasn't my car that I did these on. I helped a buddy extend his true duals out the back. Obviously, he chose the easy route and went under the axle. What we did was put a flange in front of the rear end so the back end pipes could be disconnected. Remember, the pipes will be in a fixed position and the rear end can move. But with pipes tucked under the rear end, then the rear end can only drop so far before hitting them. This means you cannot pick up the rear of the car and let the rear wheels sag as it will put a tremendous force on the rest of the exhaust. Anyway, we flanged his system before the rear end so he could drop the 2 back sections quickly and then he could let the rear end swing down without taking the entire exhaust off. What we did was actually pretty cool, we put two more mufflers in the rear section of pipe to further quiet the system + the out the back helped it tone down on the overall racket. He could unbolt the tail sections and bolt on flanged turndowns and run just the original true duals with 2 chambered bullets that were located under the car. So he could switch from 2 mufflers with dumps to 4 mufflers out the back with tips in less then an hour. It was pretty sweet. 
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It wasn't my car that I did these on. I helped a buddy extend his true duals out the back. Obviously, he chose the easy route and went under the axle. What we did was put a flange in front of the rear end so the back end pipes could be disconnected. Remember, the pipes will be in a fixed position and the rear end can move. But with pipes tucked under the rear end, then the rear end can only drop so far before hitting them. This means you cannot pick up the rear of the car and let the rear wheels sag as it will put a tremendous force on the rest of the exhaust. Anyway, we flanged his system before the rear end so he could drop the 2 back sections quickly and then he could let the rear end swing down without taking the entire exhaust off. What we did was actually pretty cool, we put two more mufflers in the rear section of pipe to further quiet the system + the out the back helped it tone down on the overall racket. He could unbolt the tail sections and bolt on flanged turndowns and run just the original true duals with 2 chambered bullets that were located under the car. So he could switch from 2 mufflers with dumps to 4 mufflers out the back with tips in less then an hour. It was pretty sweet.
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Unless someone can truly quantify the difference in flow between the two (e.g., bench flow, etc), its probably safe to say you're not going to have any truly measurable (dyno or butt-meter) gains/loses and any info you get here will be based primarily on theory and/or shortcut solutions based on budgets.
Is a straight pipe better than bent? Yep. How much? Dunno. What are your goals? Bracket racing 1/4 miler running full exhaust worried about shaving .001 on the time slip? If so, then we need to look at the ENTIRE exhaust system from the heads back. Or....are we talking about a budget restricted hot-rodder looking to save a buck? If the answer is the latter of the two, budget will always win so roll with your existing plan.
IMO FWIW, under the axle makes zero sense when you consider net performance gains (which again, are unproven) compared to money saved and vehicle system sacrifices (ground clearance, lifting car, etc). Off box now....good luck!
Is a straight pipe better than bent? Yep. How much? Dunno. What are your goals? Bracket racing 1/4 miler running full exhaust worried about shaving .001 on the time slip? If so, then we need to look at the ENTIRE exhaust system from the heads back. Or....are we talking about a budget restricted hot-rodder looking to save a buck? If the answer is the latter of the two, budget will always win so roll with your existing plan.
IMO FWIW, under the axle makes zero sense when you consider net performance gains (which again, are unproven) compared to money saved and vehicle system sacrifices (ground clearance, lifting car, etc). Off box now....good luck!
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From: Franklin Lakes, NJ
Unless someone can truly quantify the difference in flow between the two (e.g., bench flow, etc), its probably safe to say you're not going to have any truly measurable (dyno or butt-meter) gains/loses and any info you get here will be based primarily on theory and/or shortcut solutions based on budgets.
Is a straight pipe better than bent? Yep. How much? Dunno. What are your goals? Bracket racing 1/4 miler running full exhaust worried about shaving .001 on the time slip? If so, then we need to look at the ENTIRE exhaust system from the heads back. Or....are we talking about a budget restricted hot-rodder looking to save a buck? If the answer is the latter of the two, budget will always win so roll with your existing plan.
IMO FWIW, under the axle makes zero sense when you consider net performance gains (which again, are unproven) compared to money saved and vehicle system sacrifices (ground clearance, lifting car, etc). Off box now....good luck!
Is a straight pipe better than bent? Yep. How much? Dunno. What are your goals? Bracket racing 1/4 miler running full exhaust worried about shaving .001 on the time slip? If so, then we need to look at the ENTIRE exhaust system from the heads back. Or....are we talking about a budget restricted hot-rodder looking to save a buck? If the answer is the latter of the two, budget will always win so roll with your existing plan.
IMO FWIW, under the axle makes zero sense when you consider net performance gains (which again, are unproven) compared to money saved and vehicle system sacrifices (ground clearance, lifting car, etc). Off box now....good luck!
edit: I did some research online, and it seems like turbulance is the big issue with non-mandrel bends, not necessarily the amount of flow. Think in terms of fluid dynamics, that makes sense. Mandrel bends is a must then. Now the only issue is whether to go below, or above the axle. Roads aren't here aren't the greatest, but I don't daily drive the car either. I guess we'll see. Thanks for the input guys!
Last edited by qwikz28; Nov 7, 2010 at 10:31 AM.
Damn... alot of guys here are so quick to give opinions but have never experienced it. I had them for over 2 years and I can only remember a handfull of times that I scraped. And it was from the x pipe not from the pipes under the axle. Like I said above, it all comes down to the guy that does the bends. I will try and find better pics. My car was also lowered on Eibach Sportlines. I loved the exhaust sound and was comfortable daily driving it. I had hooker headers, hutto lanes true dual with moroso spiral flows and then had the muffler shop add the rear bends under the axle with corsa clones. I'd say do it and you will be happy. The sound is awesome.
Here are the pics of the car on sportlines like I said above.
Here is a pic so you can see the clearance I had.
Here is a close up pic and you can't see any scrapes on the pipes....
Here is another close up pic and you can also see the red sportline springs and all the clearance I had. It all depends on how good your muffler shop is. If they say they can't do it, then believe them. You need someone who isn't afraid to do it.
Here is a pic so you can see the clearance I had.
Here is a close up pic and you can't see any scrapes on the pipes....
Here is another close up pic and you can also see the red sportline springs and all the clearance I had. It all depends on how good your muffler shop is. If they say they can't do it, then believe them. You need someone who isn't afraid to do it.
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DG - thank you for the lengthy reply. I noticed too that everyone telling me not to do it never had any experience, but everyone I spoke to that had it told me to do it. Bizarre right? In any event, I think I'm going to do it. I sourced a great exhaust shop in Baltimore (it's a hike!) but they're work is top notch. I would rather travel and get it right, then have a disaster. Thanks again for your posts and the supplied pics, I'm probably going to email the shop some of them before I go down there so they know what they will be dealing with.
And my car isn't a daily btw, so it shouldn't be too much of a hassle. Even if it is, I"ll have them reroute that bad boy!
And my car isn't a daily btw, so it shouldn't be too much of a hassle. Even if it is, I"ll have them reroute that bad boy!
What were you crushing? the pipes? I ran it for over 2 years with no issues. It all depends on how good of a job the muffler shop does.
Have you personally tried the under the axle setup? Or are you another one of the guys that jumps on the band wagon? Not trying to single you out but from your post it doesn't sound like you have personal experience.
Damn... alot of guys here are so quick to give opinions but have never experienced it. I had them for over 2 years and I can only remember a handfull of times that I scraped. And it was from the x pipe not from the pipes under the axle. Like I said above, it all comes down to the guy that does the bends. I will try and find better pics. My car was also lowered on Eibach Sportlines. I loved the exhaust sound and was comfortable daily driving it. I had hooker headers, hutto lanes true dual with moroso spiral flows and then had the muffler shop add the rear bends under the axle with corsa clones. I'd say do it and you will be happy. The sound is awesome.
Have you personally tried the under the axle setup? Or are you another one of the guys that jumps on the band wagon? Not trying to single you out but from your post it doesn't sound like you have personal experience.
Damn... alot of guys here are so quick to give opinions but have never experienced it. I had them for over 2 years and I can only remember a handfull of times that I scraped. And it was from the x pipe not from the pipes under the axle. Like I said above, it all comes down to the guy that does the bends. I will try and find better pics. My car was also lowered on Eibach Sportlines. I loved the exhaust sound and was comfortable daily driving it. I had hooker headers, hutto lanes true dual with moroso spiral flows and then had the muffler shop add the rear bends under the axle with corsa clones. I'd say do it and you will be happy. The sound is awesome.
