Exhaust question
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From: All humans are vermin in the eyes of Guru VA
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Exhaust question
is 2.25" true dual exhaust system restrictive for a sub 400hp small block application?
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
Most guys are putting on 2.5 inch systems, with H or Y pipe crossovers, and some sort of muffler system,
I use stock mufflers, as I got tired of the droning at 1800 rpm and lugging traffic.....
any header manufacturer will say that adding even straight pipes without ANY muffler will kill any affect the headers have, and you gain absolutely nothing from them at that point....
having passed on that comment, I have headers, for clearances on the rack/pin install, and plug wires, engine get cooler quicker when stopped also....
GENE
I use stock mufflers, as I got tired of the droning at 1800 rpm and lugging traffic.....
any header manufacturer will say that adding even straight pipes without ANY muffler will kill any affect the headers have, and you gain absolutely nothing from them at that point....
having passed on that comment, I have headers, for clearances on the rack/pin install, and plug wires, engine get cooler quicker when stopped also....
GENE
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From: All humans are vermin in the eyes of Guru VA
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OK thanks guys. Looks like I can plan on a hefty restriction.
The goal is a turbocharged 383. The reason I ask about 2.25" exhaust pipe is that, I am using grand national turbos and their inlet is a 2.25" circle, so plumbing to the turbos becomes very easy.
So the plan is to use a pair of shorty sanderson headers which arent that much worse than long tubes. So The plan is to plumb some 2.25" pipe from the headers to the turbos. Then some 2.5" or 3" exhaust from the turbos.
Looks like I can plan on losing some HP.
Thanx
The goal is a turbocharged 383. The reason I ask about 2.25" exhaust pipe is that, I am using grand national turbos and their inlet is a 2.25" circle, so plumbing to the turbos becomes very easy.
So the plan is to use a pair of shorty sanderson headers which arent that much worse than long tubes. So The plan is to plumb some 2.25" pipe from the headers to the turbos. Then some 2.5" or 3" exhaust from the turbos.
Looks like I can plan on losing some HP.
Thanx
Thread Starter
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From: All humans are vermin in the eyes of Guru VA
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It might not be that bad, either. The LS1 f-bodies are running a single 3" pipe for all kinds of power. and thats about the same as dual 2.25" pipe.
So we shall see.
So we shall see.
Team Owner
Joined: Jun 2001
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From: Virginia USA
Originally Posted by Gordonm
If you are putting a turbo on a 383 I hope you are looking for more than 400 HP. A 400 HP naturally aspirated 383 is a mild motor. A turbo 383 I would be expecting 600HP.
at least
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From: All humans are vermin in the eyes of Guru VA
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700hp is reasonable.
But NA is important because of my turbo mapping software.
The less restrictive I can make it the better. But the reality of the matter is that the turbos want a 2.25" entrance. So I could probably plumb 2.5" or 3" pipe into a megaphone down to 2.25" Not really sure if that would be less restrictive as just plumbing in 2.25" pipe.
Oh well.
But NA is important because of my turbo mapping software.
The less restrictive I can make it the better. But the reality of the matter is that the turbos want a 2.25" entrance. So I could probably plumb 2.5" or 3" pipe into a megaphone down to 2.25" Not really sure if that would be less restrictive as just plumbing in 2.25" pipe.
Oh well.
Melting Slicks
Joined: Dec 2000
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From: Eastern Connecticut
What size outlet is the header? If it is 2.5 then some kind of reducer is necessary regardless, and maybe you can put that right before the turbo, to make a nozzle, increasing the velocity into the turbo. It'll be custom made pipe either way. Where are you mounting the turbos?
Either way, you want as big as possible behind the turbo to prevent backpressure from slowing the turbos down.
Have fun, invest in tire company stock! LOL Joe
Either way, you want as big as possible behind the turbo to prevent backpressure from slowing the turbos down.
Have fun, invest in tire company stock! LOL Joe
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From: All humans are vermin in the eyes of Guru VA
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The outlet will be 2.5 or 3" depending on which shorties I buy.
3" pipe has the same area as 4 1.5" primaries. So a 3" outlet from the shorties into a reducer into the turbo would probably be best.
The ultimate plan is to mount the turbos above the oil pan. so I can gravity drain them. I also have to avoid all the steering linkage. But its really not that big a deal.
3" pipe has the same area as 4 1.5" primaries. So a 3" outlet from the shorties into a reducer into the turbo would probably be best.
The ultimate plan is to mount the turbos above the oil pan. so I can gravity drain them. I also have to avoid all the steering linkage. But its really not that big a deal.
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From: All humans are vermin in the eyes of Guru VA
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OK so I am looking at some header companies online.
I notice that on some of the headers they go into a smaller collector than the exhaust system. Does this have some kind of scavenging effect?
I notice that on some of the headers they go into a smaller collector than the exhaust system. Does this have some kind of scavenging effect?
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From: All humans are vermin in the eyes of Guru VA
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What would be nice is developing something that would add a scavenging effect behind the turbo, which would lower the restriction of the turbo itself, but also spool it up faster.
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From: All humans are vermin in the eyes of Guru VA
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I am not sure that the downpipes will be 3" I dont think the turbos will accept a 3". 2.5" maybe. And depending on how I arrange things in the engine compartment I might be able to put a reducer from the turbo into the 3" exhaust.
Melting Slicks
Joined: Jul 2002
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From: Boulder Creek California
Something I learned with my first true dual exhaust, quality of the bends is every bit as important as the diameter. Not knowing better (and probably okay for the mostly stock engine) I got a 2" system bent, $300. Didn't quite fit under the passenger side rear lower strut so they crushed that 2" diameter tube to what must've been half the diameter. In any case, non-mandrel bends are very bad. Sounds like you're doing something pretty major, but that's general advice for everybody here. My homemade 2.5" duals are cut at an angle and welded. $53.80 20' 2.5" aluminized tubing + $170 Flowmaster 50 DF's
Good luck
-Chris
Good luck
-Chris