Exhaust????
Thread Starter
Racer
Joined: Nov 2006
Posts: 270
Likes: 4
From: columbia mo
Exhaust????
I have been talking to some forum members about an intake but we have to the conclusion that I need an exhaust more importantly. I was going to just get new mufflers and a cat. Now I think I want to do pipes as well. Sooo... I want to get 3" exhaust and flowmasters and the cat is up in the air if I "need" it anymore. I dont like the loud harley pop sound but I do want some loudness over the stock exhaust. Would the 3" be alright without the cat or would that give me the poppy sound that is terribly loud.
Also one more thing. Should I start the 3" piping from the headers back or after where the cat is. Will there be that much more hp if it is the whole exhaust at 3"?
Thank you guys so much, you are really helping me out a lot!!!!!
Also one more thing. Should I start the 3" piping from the headers back or after where the cat is. Will there be that much more hp if it is the whole exhaust at 3"?
Thank you guys so much, you are really helping me out a lot!!!!!
Pro
Joined: Nov 2006
Posts: 729
Likes: 0
From: Concord North Carolina
Originally Posted by favrefan2k4
I have been talking to some forum members about an intake but we have to the conclusion that I need an exhaust more importantly. I was going to just get new mufflers and a cat. Now I think I want to do pipes as well. Sooo... I want to get 3" exhaust and flowmasters and the cat is up in the air if I "need" it anymore. I dont like the loud harley pop sound but I do want some loudness over the stock exhaust. Would the 3" be alright without the cat or would that give me the poppy sound that is terribly loud.
Also one more thing. Should I start the 3" piping from the headers back or after where the cat is. Will there be that much more hp if it is the whole exhaust at 3"?
Thank you guys so much, you are really helping me out a lot!!!!!
Also one more thing. Should I start the 3" piping from the headers back or after where the cat is. Will there be that much more hp if it is the whole exhaust at 3"?
Thank you guys so much, you are really helping me out a lot!!!!!
Why 3"? Most use 2.5., I use true dual. Flowmasters are loud all the time but not classy loud. Hooker headers. And I like the sound of borla if you want to have a muffler. Magnaflow is also a good brand. Bassanni X pipe seems pretty popular. I run no cats and muffler eliminators and mine is loud. If you have the spare $$, then go ahead and put a high flow cat on there if you choose. Catco and random tech are good brands. Good luck. You must have a cat though if you have sniffer emission testing.
Race Director
Joined: Jun 2004
Posts: 13,957
Likes: 706
From: WI
3" dual or single? A 3" dual system would be to much and you would lose velocity of the exhaust flow. It's best to tune the pipe size to what the engine breathes. The best system will start large, have a cross over pipe, and get smaller at the end to keep the cooling exhaust gases velocity up. A 2.25" dual system won't flow any more then the stock single system.
Racer
Joined: May 2006
Posts: 281
Likes: 0
From: Urbana OH
I'm running 2.75" piping from the mainfolds back. Had a local shop just chop it and run the straight back with an H pipe to even out the banks and magnaflow mufflers on the back side. I don't have that raspy backfire sound you're talking about and I picked up quite a few ponies. I kinda had to do it with mine because my exhaust rusted through and dropped and I needed a fast replacement to get back on base but if I could do it over again I would do the exact same thing with an X-pipe instead of the H. I got mine done (just piping because I already had the mufflers) for $110. And that's out here in Cali where labor is expensive.
The reason I could do it is my car is registered in Ohio and we don't have e-check. If ya have any questions halla back.
Semper Fi,
Merritt
The reason I could do it is my car is registered in Ohio and we don't have e-check. If ya have any questions halla back.
Semper Fi,
Merritt
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Your exhaust system should flow about 2.2cfm per chp, for example a 300chp engine needs 660cfm of flow.
A 2 1/2" pipe will flow about 560cfm; you can do the math for a 3" pipe if interested.
To match your exhaust to the engine you need to consider flow in each of the components to be sure there is sufficient flow available.
If you are thinking about using a single cat, it will likely be the liminting factor in exhaust system performance.
A 2 1/2" pipe will flow about 560cfm; you can do the math for a 3" pipe if interested.
To match your exhaust to the engine you need to consider flow in each of the components to be sure there is sufficient flow available.
If you are thinking about using a single cat, it will likely be the liminting factor in exhaust system performance.
Thread Starter
Racer
Joined: Nov 2006
Posts: 270
Likes: 4
From: columbia mo
the precats are already gone!!! 
I talked to an exhaust shop and I think we are going to stay with front y-pipe but have 3" outlet into 3" hi flow cat. then 3" custom y-pipe to 2.5" pipes to flowmasters. How does that sound? Will this add the hp?
I talked to an exhaust shop and I think we are going to stay with front y-pipe but have 3" outlet into 3" hi flow cat. then 3" custom y-pipe to 2.5" pipes to flowmasters. How does that sound? Will this add the hp?
Last edited by favrefan2k4; Dec 7, 2006 at 05:19 PM.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Some, not a lot. Just guessing 5 to 10 HP. You won't add a lot without headers. You will add sound! But you can add headers and a front pipe later.
Last edited by BADDUCK; Dec 7, 2006 at 05:46 PM.
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Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by favrefan2k4
the precats are already gone!!! I talked to an exhaust shop and I think we are going to stay with front y-pipe but have 3" outlet into 3" hi flow cat. then 3" custom y-pipe to 2.5" pipes to flowmasters. How does that sound? Will this add the hp?
I talked to an exhaust shop and I think we are going to stay with front y-pipe but have 3" outlet into 3" hi flow cat. then 3" custom y-pipe to 2.5" pipes to flowmasters. How does that sound? Will this add the hp?
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by favrefan2k4
what about no cat?
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Originally Posted by favrefan2k4
what about no cat?
Thread Starter
Racer
Joined: Nov 2006
Posts: 270
Likes: 4
From: columbia mo
That's the first time I have heard that. Everyone has told me that as long as there are no precats and the front y-pipe has a 3" collector to the 3" cat, that would be good.They say thats why they sell systems that are only the back have of the exhaust.
If you think about it since only one side of the engine is blowing to each side it is a 4.5" exhaust going into the 3".
If you think about it since only one side of the engine is blowing to each side it is a 4.5" exhaust going into the 3".
Thread Starter
Racer
Joined: Nov 2006
Posts: 270
Likes: 4
From: columbia mo
That's the first time I have heard that. Everyone has told me that as long as there are no precats and the front y-pipe has a 3" collector to the 3" cat, that would be good.They say thats why they sell systems that are only the back have of the exhaust.
If you think about it since only one side of the engine is blowing to each side it is a 4.5" exhaust going into the 3".
If you think about it since only one side of the engine is blowing to each side it is a 4.5" exhaust going into the 3".