3" exhaust ????

[turbo94hb]

what does anyone think about 3" exhaust on a civic h/b ls/vtec/turbo? Not enoght back pressure? Good for the turbo? anyone.... :lol:

[Tits McGee]

Originally posted by "TenaciousC"

and may i suggest thermal :thumbup:

Thermal Stealth pwnz j00.

[Just Dave]

A 2.5" pipe is good for over 300hp but isn't as "sexy" as a 3" pipe.

[Epicman]

Originally posted by "turbo94hb"

what does anyone think about 3" exhaust on a civic h/b ls/vtec/turbo? Not enoght back pressure? Good for the turbo? anyone.... :lol:

The turbo creates all the backpressure the engine needs. After the turbo anything else is just adding restrictions.

[turbo94hb]

thanks for all of your replys, thermal is a good way to go, might just have 3" mandrel bent, all depends on the dough.....

[FearThe4Doors]

i agree, on a turbo you want to have as close to 0 backpressure after the turbo as possible. 3" mandrel is tits. 3" crimp is alright. 2.5" mandrel is as small as i'd go. As far as it because the turbo creates all the backpressure the engine needs? I guess.. but thats not how i explain it.

BTW, what's thermal? Thermal wrap the pipe? That may not be a good idea.. i'll share my thoughts if thats what you guys mean.

[Epicman]

Originally posted by "FearThe4Doors"

As far as it because the turbo creates all the backpressure the engine needs? I guess.. but thats not how i explain it.

BTW, what's thermal? Thermal wrap the pipe? That may not be a good idea.. i'll share my thoughts if thats what you guys mean.

I said that because that's how I heard it explained once. How would you explain it? I'm always eager to learn more.

[FearThe4Doors]

well, i'm not trying to be a know-it-all or anything so dont think that... I've heard people explain it your way too. That just always makes me think that the turbo's purpose is just to be a big restrictor in the exhaust so the engine operates at its peak. When I explain it to people, I say that on a turbo engine, the major source of your power is coming from the turbo. The turbo creates the power off of the exhaust gas flow. So you want as much exhaust to flow thru the turbo as possible. Therefore, after the turbo, you want the exhaust gas to get the hell out of there quick, or else it will create backpressure and slow down the gas thats still before and going thru the turbo. Obviously we dont want that because that's costing us power. Ideally, we would want a vacuum after the turbo so it actually would PULL the exhaust thru and not have to waste energy from the engine having to push it thru.

As an example to how important a good flowing exhaust is to a turbo car, on my 86 Daytona, it had the bone stock exhaust (and everything else). By gutting the cat alone, the car picked up 1-2 psi. And thats with it still having the crappy 2" or whatever factory exhaust.

[Epicman]

Originally posted by "FearThe4Doors"

well, i'm not trying to be a know-it-all or anything so dont think that... I've heard people explain it your way too. That just always makes me think that the turbo's purpose is just to be a big restrictor in the exhaust so the engine operates at its peak. When I explain it to people, I say that on a turbo engine, the major source of your power is coming from the turbo. The turbo creates the power off of the exhaust gas flow. So you want as much exhaust to flow thru the turbo as possible. Therefore, after the turbo, you want the exhaust gas to get the hell out of there quick, or else it will create backpressure and slow down the gas thats still before and going thru the turbo. Obviously we dont want that because that's costing us power. Ideally, we would want a vacuum after the turbo so it actually would PULL the exhaust thru and not have to waste energy from the engine having to push it thru.

As an example to how important a good flowing exhaust is to a turbo car, on my 86 Daytona, it had the bone stock exhaust (and everything else). By gutting the cat alone, the car picked up 1-2 psi. And thats with it still having the crappy 2" or whatever factory exhaust.

Good explanation. I didn't think you were trying to be a know it all, I just wanted to know a different way of explaning it. I didn't know how to write my post without sounding like I was being an ass.

[FearThe4Doors]

thanks! :thumbup:

We were all admiring the Kia the other day at John's shop. I cant wait till everything's in order and its running again

[Epicman]

Originally posted by "FearThe4Doors"

thanks! :thumbup:

We were all admiring the Kia the other day at John's shop. I cant wait till everything's in order and its running again

You can't wait? I've been waiting 8 months now since the Kia last ran good. It hasn't been at Secret Services 8 months. It's just been 8 months since I decided to take the engine out.

[FearThe4Doors]

i know the feeling. My car has spent WAY more than it's share of time up on jack stands.. :(

[Just Dave]

Originally posted by "FearThe4Doors"

well, i'm not trying to be a know-it-all or anything so dont think that... [/quote

Me either :D


Ideally, we would want a vacuum after the turbo so it actually would PULL the exhaust thru and not have to waste energy from the engine having to push it thru.

Which is why some actually neck down the exhaust after the muffler. Some guys run 3 inches from the downpipe to the muffler, and 2.5 after that. The reason being that as the exhaust travels from the turbo, it cools down, and thus gets denser. If you keep the 3 inch all the way, the exhaust will continue to slow as it travels. If you neck down to 2.5, it will pick up the velocity, in effect giving a "vacuum" effect on the exhaust.


As an example to how important a good flowing exhaust is to a turbo car, on my 86 Daytona, it had the bone stock exhaust (and everything else). By gutting the cat alone, the car picked up 1-2 psi. And thats with it still having the crappy 2" or whatever factory exhaust.[/quote]

I certainly believe that. Many turbofords pick up a great deal of HP swapping to a 3 inch down pipe and exhaust.

Also, many V8 turbo cars have picked up as much as 50 RWHP (not a typo) by switching away from Flowmaster mufflers and going to a straight thru muffler such as the Dynomax ultraflow.

[FearThe4Doors]

thanks for the info!

And i agree, Flowmasters are TERRIBLE for turbo cars