Exhaust Size

[shelbynut]

Just received the 2001 GTS stock headers to install on my 94 RT/10, and upon inspection noticed that the outlet size is only about 2 1/4". I was planning on installing 3" high flow cats and 3" high flow mufflers, but since my restriction is already at the headers, is there any point? I already have 2.5" exhaust, with stock cats, and the mufflers replaced with resonators, and while I will definately be installing high flow cats, can't see how I would achieve any noticable gains in power by installing 3" everything behind that 2 1/4" header outlet. I have side exhaust, so it's a short run already. Not planning on $upercharging or turboing any time soon, might do the 1.7 RR's and 3.55's over the next year.

As always, any comments or experiences would be appreciated!

Jay

 

[SNKEBIT]

have them ceramic coated and you won't need the crappy heat sheilds. Getting rid of the cats and muffs,(stockers) is a big step!!!

 

[shelbynut]

Will check into the ceramic coating, would be nice to get rid of the shields!

Need the cats up here in Ontario, Canada, they test every two years, so I'll be going with high flow magnaflows.

It'll be alot cheaper if I don't have to buy new 3" pipe, 3" mandrel 90's, and mufflers (have to buy new cats either way, but can re-use the 2.5" resonators I replaced the stock mufflers with) but don't want to be sacrificing power for the sake of a few hundred dollars, just trying to get an idea as to how much of a difference going to 3" exhaust will make!

If there is little or no difference, I'll put the extra cash toward the 1.7rr's....

Jay

 

[ViperRay]

I can't answer your question directly with any dyno info but laws of physics tells us that both the diameter and the length of the tube matters (get your minds out of the gutter) in terms of flow and resistance.

The diameter is the more important (a squared value) though.
So, I would think that keeping the "restriction" as short as possible would be better, albeit not optimal.

 

[shelbynut]

Been thinking about this for the past few days and think I will take the complete exhaust system off, Put the Ceramic Coated Gen II headers on, new flexpipes, put a flange on so I can bolt the stock cat/resonator setup back on in two years to pass emissions, and put straight 2.5" or 3" pipe in with no cats and Magnaflow high flow mufflers.

Magnaflow 3"

Should breath just fine, and should sound awesome! Back to the same question, 2.5" or 3"?

Jay

 

[SNKEBIT]

2.5 should work just fine. I don't see any benifit from a 3 inch when it has to get through that little hole in the beginning.

 

[opnwide]

3" won't give any power benefit, but will increase sound. I put 3" initially on my '95 with factory headers, and the sound was bad, got minimum hp. I later went with bellangers. The sound was still too loud, but I had the power to back it up so I figured it was worth it.
I recommend 2 1/2" with factory pipes.

 

[Chuck 98 RT/10]

I can't answer your question directly with any dyno info but laws of physics tells us that both the diameter and the length of the tube matters (get your minds out of the gutter) in terms of flow and resistance.

True, but as you probably already know, that doesn't mean bigger is necessarily better (again, get your minds out of the gutter). Depends on the flow through the head (more gutter thoughts) and camshaft specs.

With side exhaust I imagine 3" would be way too loud with no HP benefit on a stock motor.

 

[shelbynut]

Thanks everyone, you've confirmed my suspicions that 3" would probably be too loud and result in little if any hp increase, will stick with 2.5".

Off to see my exhaust guy now for some parts!

Jay

 

[SNKEBIT]

I can't answer your question directly with any dyno info but laws of physics tells us that both the diameter and the length of the tube matters (get your minds out of the gutter) in terms of flow and resistance.

True, but as you probably already know, that doesn't mean bigger is necessarily better (again, get your minds out of the gutter). Depends on the flow through the head (more gutter thoughts) and camshaft specs.

With side exhaust I imagine 3" would be way too loud with no HP benefit on a stock motor.

pretty hard to get out of the gutter when that's where one resides....