3" exhaust myth????
#1
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Car: 1992 RS Polo Green Coupe 86 IROC
Engine: 305 TBI
Transmission: Automatic
Axle/Gears: Yes it has some!!!
3" exhaust myth????
Hey all, I'm going through my 92 and doing as many upgrades as I can to it. It was suggested to improve the air in and the exhaust out. It was recomended to me to go 3" all the way. Suggestions of hooker headers and Dougs D901 y pipe were perfect fits for my 92. I just got them and noticed that the out let pipe on the y is 2.5" So is there any true 3" all the way exhausts. The hooker y pipes also reduce as well. Trying to see why change the headers if I already have a 2.5" exhaust on the car now. Is just changing the headers and y pipe going to make that much of a difference. I'm still choking it down. Maybe I was confused. Thought flow was the whole point? Suggestions please.
#2
Supreme Member
Re: 3" exhaust myth????
I think dyno don has a full 3" Y pipe. Most people who get the D901 cut the 2.5 pipe off at the merger, open up the terrible merging and weld on a 3" pipe. There are a bunch of 3" catbacks
Example
https://www.thirdgen.org/forums/exha...ke-3-inch.html
Example
https://www.thirdgen.org/forums/exha...ke-3-inch.html
#3
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Car: 89 Firebird
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Re: 3" exhaust myth????
I have the same exhaust. Hookers and D901 Y. Had my guy cut the 2.5 in merger and put in a flowmaster 3in merger. Several companies make that y, think I got mine on Amazon
Last edited by dmccain; 03-01-2022 at 07:58 PM.
#4
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Re: 3" exhaust myth????
I’m looking at doing a true dual 3” all the way. But I’m running into a complete lack of room. Sorry to ask this question here, but what are some thoughts on trimming this area?
Just enough to get them to fit through.
I saw in another thread that someone removed that top black bar. I don’t think that’s a good idea but I’m not sure. I could really use some good input here.
Just enough to get them to fit through.
I saw in another thread that someone removed that top black bar. I don’t think that’s a good idea but I’m not sure. I could really use some good input here.
#5
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Re: 3" exhaust myth????
#6
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Car: Resto-Mod 1987 IROC-Z Clone
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Re: 3" exhaust myth????
I would pass on a Dual 3.00" Exhaust System unless you are knocking on the door of 500+ HP.
Dual 2.50" goes a long way...
and Single 3.50" or 4.00" would be my recommendation (on 3rd-Gens; due to fitment) if you are in the 500+ HP range.
Single 2.50" Systems are plenty for your Stock 305.
Dual 2.50" goes a long way...
and Single 3.50" or 4.00" would be my recommendation (on 3rd-Gens; due to fitment) if you are in the 500+ HP range.
Single 2.50" Systems are plenty for your Stock 305.
The following 2 users liked this post by vorteciroc:
George Klass (05-10-2022), T.L. (03-17-2022)
#7
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Re: 3" exhaust myth????
Also remember that the pipes are going to move around slightly. If you only have just enough room, you might run into rubbing and unpleasant vibrations.
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Bills87IROC (10-11-2022)
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Car: 1992 Camaro RS
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Re: 3" exhaust myth????
I’m looking at doing a true dual 3” all the way. But I’m running into a complete lack of room. Sorry to ask this question here, but what are some thoughts on trimming this area?
Just enough to get them to fit through.
I saw in another thread that someone removed that top black bar. I don’t think that’s a good idea but I’m not sure. I could really use some good input here.
Just enough to get them to fit through.
I saw in another thread that someone removed that top black bar. I don’t think that’s a good idea but I’m not sure. I could really use some good input here.
#9
Senior Member
Re: 3" exhaust myth????
@QwkTrip Your suggestion was perfect!
I got a UMI Panhard Relocation Bar and that is exactly what I needed!
Before and After.
And a further back view of the whole area before and after.
Although I agree that dual 3” is a bit hard to route, I don’t think it’s overkill. Just complicated. I will be making about 530 HP so it’ll be functional.
I got a UMI Panhard Relocation Bar and that is exactly what I needed!
Before and After.
And a further back view of the whole area before and after.
Although I agree that dual 3” is a bit hard to route, I don’t think it’s overkill. Just complicated. I will be making about 530 HP so it’ll be functional.
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Car: 84 TA orig. 305 LG4 "H" E4ME
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Re: 3" exhaust myth????
Please keep us posted.
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skinny z (10-09-2022)
#11
Supreme Member
Re: 3" exhaust myth????
Off topic but I'd like to see how level the panhard bar will be once the suspension is fully loaded.
EDIT: Having a better look it would appear the weight is on the suspension. Just through the jack stands.
You might be wanting to add the adjustable bracket for the axle side of the panhard bar so as to restore it to a level condition.
EDIT: Having a better look it would appear the weight is on the suspension. Just through the jack stands.
You might be wanting to add the adjustable bracket for the axle side of the panhard bar so as to restore it to a level condition.
Last edited by skinny z; 10-09-2022 at 11:05 AM.
#12
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Car: '91 Firebird Formula
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Re: 3" exhaust myth????
Hey all, I'm going through my 92 and doing as many upgrades as I can to it. It was suggested to improve the air in and the exhaust out. It was recomended to me to go 3" all the way. Suggestions of hooker headers and Dougs D901 y pipe were perfect fits for my 92. I just got them and noticed that the out let pipe on the y is 2.5" So is there any true 3" all the way exhausts. The hooker y pipes also reduce as well. Trying to see why change the headers if I already have a 2.5" exhaust on the car now. Is just changing the headers and y pipe going to make that much of a difference. I'm still choking it down. Maybe I was confused. Thought flow was the whole point? Suggestions please.
Last edited by SbFormula; 01-24-2023 at 09:53 AM.
#13
Senior Member
Re: 3" exhaust myth????
Possibly. I’m only aware that the Panhard bar controls the left and right sway of the diff. I have no idea how tilted or level it should or should not be. Let’s hear about it.
#14
Supreme Member
Re: 3" exhaust myth????
Short story is that the bar should be level at ride height.This way as the suspension unloads or compresses, the axle moves equally in either direction.
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NoEmissions84TA (10-09-2022)
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skinny z (10-09-2022)
#16
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Re: 3" exhaust myth????
Lots of good tech in there for sure.
#17
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Re: 3" exhaust myth????
Dual 2.5 vs Dual 3 inch, hp difference on our 3rd/4th Gen cars at 500 to 600 hp flywheel hp?
Probably about 3 percent in favor of the Dual 3 inch system based on what Hooker shared when discussing their BlackHeart true dual 2.5 inch exhaust vs true dual 3 inch.
On LS1Tech saw a post where someone's car made just over 600 whp. He swapped out a Kook's true dual 3 inch for a BlackHeart true dual 2.5 due ground clearance issues.
He said Dyno showed the car lost ~17 whp peak to peak. Car gained ~5 wtq. The BlackHeart 2.5 fixed the ground clearance issues. Car owner said that was worth the hp cost.
So about ~3% hp difference and that matched pretty well with what the Hooker tech had said seems reasonable at ~600whp and probably even less at 400 whp.
Probably about 3 percent in favor of the Dual 3 inch system based on what Hooker shared when discussing their BlackHeart true dual 2.5 inch exhaust vs true dual 3 inch.
On LS1Tech saw a post where someone's car made just over 600 whp. He swapped out a Kook's true dual 3 inch for a BlackHeart true dual 2.5 due ground clearance issues.
He said Dyno showed the car lost ~17 whp peak to peak. Car gained ~5 wtq. The BlackHeart 2.5 fixed the ground clearance issues. Car owner said that was worth the hp cost.
So about ~3% hp difference and that matched pretty well with what the Hooker tech had said seems reasonable at ~600whp and probably even less at 400 whp.
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NoEmissions84TA (10-13-2022)
#18
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Re: 3" exhaust myth????
Sounds like those numbers are within the range that I see (which varies quite a lot)...
#19
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Re: 3" exhaust myth????
I have 3" true duals and my only regret is not working on a different muffler configuration. I am using two bullet style mufflers due to the space constraints around the fuel tank. However, I may try to configure a dual inlet/outlet muffler in the stock location and have both exits to one since (they are tucked under). The sound is incredible, but will blow your ears out. The drone at highway speeds is enough for you to lose your mind. I have to run with the windows down and ear protection on. It's murderous on long drives. I need to make changes.
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