LSx header/exhaust design for road/race car

[Omerta]

Just making decisions about exhaust design before making up the engine mounts.

It's a (road legal) race car being built for tarmac rally events here in NZ. Engine is currently making around 450hp. I'd like the exhaust I fit now to be capable of supporting up to 550/600.

4-1 short headers would fit the space available like this example (this is not my car, but also an LS into a Cerbera):



Would this be a reasonable design for a race application? I've read that 34" give or take is optimal so I'm thinking a bit longer than this with 1 3/4" primaries into 3" collectors.

From the collectors through to the back box, not sure if it will be 2 pipes with a X or H-pipe, or a single big pipe through to the back box. Are there power pros and cons or is it just a matter of going with what fits best and ensuring there's enough flow?

Making these decisions this week so appreciate any advice!

Don

Edited by Omerta on Thursday 11th September 01:22

[stevieturbo]

In all honesty, you'll get better info on this asking either here....

www.ls1tech.com

or here.

www.ls1.com.au

in the relevant sections of course.

For a n/a setup like that, probably full long tube's, circa 1 5/8" to 1 3/4" would be the best bet.

Although these engines just make power anyway lol. Just make them as free flowing as possible, and Im sure they'll work just great. Without proper testing, you wont know what is optimum anyway.

[Omerta]

I know you're right about LS1tech, there is some great expertise there, but I find it hard to filter the good stuff from the homeboy bks. Having been here a while I feel know where the good advice comes from on PH (mostly), and I guess I'm looking for more of a trusted opinion so I know I'm at least in the right ballpark for the decisions I need to make.

[tvrolet]

4:2:1 won't have much benefit on a Chevy unless the '4' are taken from different sides of the V. 4:2:1 only works when there are equal pulses on the '4', thus a normal 4 cylinder or a flat plane crank V8 (as per a Cerbera)...but not a Chevy.

If you want longer primaries have you thought about going 'up, forward and the back' as opposed to down and back?

OK, you won't be looping both through the wing/sill, but if it's length in the primaries you want.....

[Brummmie]

From what research i came up with, 32" primaries with 13/4" or if big cubes then 17/8", i tried to get mine as long as possible, mine are around 25ish" long, but seems to go well enough.

[300bhp/ton]

Omerta said:

Just making decisions about exhaust design before making up the engine mounts.

It's a (road legal) race car being built for tarmac rally events here in NZ. Engine is currently making around 450hp. I'd like the exhaust I fit now to be capable of supporting up to 550/600.

4-1 short headers would fit the space available like this example (this is not my car, but also an LS into a Cerbera):



Would this be a reasonable design for a race application? I've read that 34" give or take is optimal so I'm thinking a bit longer than this with 1 3/4" primaries into 3" collectors.

From the collectors through to the back box, not sure if it will be 2 pipes with a X or H-pipe, or a single big pipe through to the back box. Are there power pros and cons or is it just a matter of going with what fits best and ensuring there's enough flow?

Making these decisions this week so appreciate any advice!

Don

Edited by Omerta on Thursday 11th September 01:22

How are you going to be making power? If it's by boost then I don't think the primary length will matter that much. It will be more about flow and suitable bore to maximise exhaust gas velocity and flow rate.

All of the headers that I've seen make good n/a power have been of the long tube variety with 4 into 1 merge collectors or similar with a 3" collector.

As for X or H. Well it's an old battle. But what I've read tends to follow this.

X tends to have better scavenging ability at higher rpm levels, while the H favours lower rpms.

Performance between the 2 is not always noticeable, not when employed on equal setups, although as a rule higher rpm performance favours the X more so than low rpm performance favours the H.

The biggest area appears to be sound, or tone. The X offers up a more exotic revvier exhaust note, where as the H tends to keep more of an old school V8 rumble.

[ringram]

Have a look at Nascar exhausts they are try-y these days fwiw.

[Brummmie]

This was my solution, they are not equal in length, but it was about the best thing i could come up with, with the freebie box of bends i had!