Best Performance Exhaust?
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Best Performance Exhaust?
Hi guys, I have 1985 Corvette with a Miniram and a lot of other things so I basically am shooting for power up high, over 3k but under 6k RPMs.
So, my current exhaust set up is Hedman Long Tube heads into the stock exhaust, (Y pipe into gutted catalytic converter out to a stock catback Y pipe) into two stainless steel Dynomax Ultra Flo mufflers.
When I purchased the Dynomax mufflers, it was used, I got a full Dynomax exhaust for $200. It was true duals all the way back, I believe 2 1/4 inch in diameter. When I put it on, I noticed a loss of throttle response, and the exhaust sounded blah.
When I put back the stock exhaust, it sounds pretty good, and it has good throttle response.
So, what is the best exhaust I can get for performance, and how much power gains will I get over what I already have?
Thanks!
So, my current exhaust set up is Hedman Long Tube heads into the stock exhaust, (Y pipe into gutted catalytic converter out to a stock catback Y pipe) into two stainless steel Dynomax Ultra Flo mufflers.
When I purchased the Dynomax mufflers, it was used, I got a full Dynomax exhaust for $200. It was true duals all the way back, I believe 2 1/4 inch in diameter. When I put it on, I noticed a loss of throttle response, and the exhaust sounded blah.
When I put back the stock exhaust, it sounds pretty good, and it has good throttle response.
So, what is the best exhaust I can get for performance, and how much power gains will I get over what I already have?
Thanks!
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
Convert your car over to use a STOCK 92-96 LT1 exhaust system.
I have a very good friend (CF member 93 ragtop) that I built a 383 LT4 for his 93 Vert. The car put down 462RWHP and is knocking on the 10's at over 126mph in the 1/4 mile.... All with a stock cat back exhaust.
The best exhaust for the money is a stock LTX system hooked up to a set of longtube headers.
On the TPI cars you MUST get rid of that single CAT Y Pipe exhaust system. It sucks for making power and is a huge restriction on cars with over 350hp. Back a few yrs ago I built a LPE SR 383 for a 91 6spd and the car didn't dyno anything spectacular (350RWHP) but it ran OK... Another good friend of mine's car.... I told him the single CAT exhaust sucked and was hurting it. He replaced the exhaust a few moths later with a true 2.5" dual exhaust and had to have me come over and drive the car because he couldn't believe how much more power the car had.
Will
I have a very good friend (CF member 93 ragtop) that I built a 383 LT4 for his 93 Vert. The car put down 462RWHP and is knocking on the 10's at over 126mph in the 1/4 mile.... All with a stock cat back exhaust.
The best exhaust for the money is a stock LTX system hooked up to a set of longtube headers.
On the TPI cars you MUST get rid of that single CAT Y Pipe exhaust system. It sucks for making power and is a huge restriction on cars with over 350hp. Back a few yrs ago I built a LPE SR 383 for a 91 6spd and the car didn't dyno anything spectacular (350RWHP) but it ran OK... Another good friend of mine's car.... I told him the single CAT exhaust sucked and was hurting it. He replaced the exhaust a few moths later with a true 2.5" dual exhaust and had to have me come over and drive the car because he couldn't believe how much more power the car had.
Will
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Definitely get rid of the stock exhaust. There should be nothing at all wrong with a true dual setup using either 2-1/4" or 2-1/2" pipe from the collectors back. Add an X-pipe in the same location where the main cat would sit.
I have this setup on my '87 with DynoMax mufflers and have not seen any issues. Are you still using the stock '85 cast iron heads?
I like those specific mufflers because they are fairly quiet at cruising speeds and there is no interior resonance even though my car has no carpeting or insulation in it. But at WOT in 3rd gear, the exhaust was measured at nearly 98dB.
Enough to get me warned about sound at a track day last year.
I have this setup on my '87 with DynoMax mufflers and have not seen any issues. Are you still using the stock '85 cast iron heads?
I like those specific mufflers because they are fairly quiet at cruising speeds and there is no interior resonance even though my car has no carpeting or insulation in it. But at WOT in 3rd gear, the exhaust was measured at nearly 98dB.
Enough to get me warned about sound at a track day last year.
Team Owner
Joined: Sep 2001
Posts: 62,153
Likes: 1,731
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Power gains are all about the same on a stock engine (10-15 headers, 5-10 cat elimination, 5-10 catback), and would be similar on a modified engine unless youre radical. From your posts, I would not say you are that radical.
Run full headers into true duals would be my vote, and pick whatever catback you like based on sound and your ability to deal with resonance.
Run full headers into true duals would be my vote, and pick whatever catback you like based on sound and your ability to deal with resonance.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Power gains are all about the same on a stock engine (10-15 headers, 5-10 cat elimination, 5-10 catback), and would be similar on a modified engine unless youre radical. From your posts, I would not say you are that radical.
Run full headers into true duals would be my vote, and pick whatever catback you like based on sound and your ability to deal with resonance.
Run full headers into true duals would be my vote, and pick whatever catback you like based on sound and your ability to deal with resonance.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
What do you expect for HP and torque figures from the build? Will they be verified on an engine dyno?
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
It will be a Miniram, AFR 195 heads, flat tappet version of zz409 camshaft, hedman longtube headers, I believe they are 1 5/8 non emission headers, 58mm throttle body and bunch of other small mods and all free mods. But that is the main part.
Pro
Joined: Sep 2019
Posts: 716
Likes: 135
From: Buchanan, Michigan
Convert your car over to use a STOCK 92-96 LT1 exhaust system.
I have a very good friend (CF member 93 ragtop) that I built a 383 LT4 for his 93 Vert. The car put down 462RWHP and is knocking on the 10's at over 126mph in the 1/4 mile.... All with a stock cat back exhaust.
The best exhaust for the money is a stock LTX system hooked up to a set of longtube headers.
On the TPI cars you MUST get rid of that single CAT Y Pipe exhaust system. It sucks for making power and is a huge restriction on cars with over 350hp. Back a few yrs ago I built a LPE SR 383 for a 91 6spd and the car didn't dyno anything spectacular (350RWHP) but it ran OK... Another good friend of mine's car.... I told him the single CAT exhaust sucked and was hurting it. He replaced the exhaust a few moths later with a true 2.5" dual exhaust and had to have me come over and drive the car because he couldn't believe how much more power the car had.
Will
I have a very good friend (CF member 93 ragtop) that I built a 383 LT4 for his 93 Vert. The car put down 462RWHP and is knocking on the 10's at over 126mph in the 1/4 mile.... All with a stock cat back exhaust.
The best exhaust for the money is a stock LTX system hooked up to a set of longtube headers.
On the TPI cars you MUST get rid of that single CAT Y Pipe exhaust system. It sucks for making power and is a huge restriction on cars with over 350hp. Back a few yrs ago I built a LPE SR 383 for a 91 6spd and the car didn't dyno anything spectacular (350RWHP) but it ran OK... Another good friend of mine's car.... I told him the single CAT exhaust sucked and was hurting it. He replaced the exhaust a few moths later with a true 2.5" dual exhaust and had to have me come over and drive the car because he couldn't believe how much more power the car had.
Will
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From: Hartford WI
Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
If you look at the pipes as they enter/exit the mufflers of the 92-96 lt systems they choke down to under 2.5" I.D. seems to me if it was faster with it, by adding better mufflers and removing the necked down sections of pipe it would pick up even more. Wonder if your friend did any changes after adding the system? Hardly seems adequate for anything over 425 fwhp? By adequate I mean it would have ran. Even faster with larger pipes and mufflers.. yes?
Bill, FWIW while the muffler does neck down, keep a few things in mind.
1. Its for a short distance.
2. Its towards the end where the gases have cooled down some.
The car that Rklessdriver was speaking about is mine. The motor dynoed at 462 rwhp on a magnaflow exhaust.
Over time I have switched back and forth between the stock exhaust, (minus manifolds and converters) to the magnaflow.
The butt-o-meter shows no difference
Track times seem to be identical, with the best mile mph being on the stock exhaust. 97.3mph.
Now, this is JMO but, buy exhaust based on sound. There is little to nothing to be gained hp wise on a LT1. If emissions are not a concern, spend your money on LT headers and tie into the stock (92-96) exhaust.
Rklessdriver gave me a custom made 3in exhaust with 3in straight through mufflers turned down at the differential. I had planned on putting them on and making a few passes to see if there would be any difference but have never got around to it. Maybe some day!!