Diameter

[845ste]

hi folks, I finally installed my ls7 tuned with many modifies for 8000rpm (cam, valves, pistons, connecting rods, rods, rocker arms, etc.).
I would like to understand which external diameter of the exhaust manifolds do you have?

now i have about 44mm but i think it is too few.
corvette with ls7 with compressor has 48mm.

I thought 50mm but if it is too much, I lose torque in low rpm, vice versa (small diameter) I will lose hp at high rpm.

tks all

[BogBeast]

I am thinking about an LS7 upgrade as well.

I was planning on building a set of headers and I got looking at https://www.youtube.com/watch?v=lBmjU83kaow

That pointed towards a http://www.spdexhaust.com/.

I was planning to get them to suggest a diameter and primary length - they seem to offer a pre-sales service based on the information you supply in http://www.spdexhaust.com/pdfs/Header_Spec_Sheet.p...

From what I understand, bigger is not better for normally aspirated as that is likely to reduce scavenge effect. Also the bigger the tubes the harder to it will be better to fit in

[ROWDYRENAULT]

I just had my second set of headers built by Greg Holman in Nevada. The first set left when I sold Ultima 1.0 they were equal length 8 into 1 and they were absolutely glorious but I have to admit a little to load above 3000 RPM for my 70-year-old ears. Ultima 2.0s headers are also by Greg. This time they have 9 inch primaries at 44.9 mm transitioning to 48mm pipes as short as possible to a merged x pipe into two separate pipes with a muffler each. I don't quote the length of the 48mm pipes because in theory, they should have been shorter but the packaging of the GTR dictates otherwise. Greg has only built headers as a living since the late 70s to include NASCAR and Indy car teams and he felt that this was the best compromise possible given the restrictions of the primaries being too long. This is on a 7 Liter L.S. 677 HP 645 FT. LBS

[dandare]

845ste said:

hi folks, I finally installed my ls7 tuned with many modifies for 8000rpm (cam, valves, pistons, connecting rods, rods, rocker arms, etc.).
I would like to understand which external diameter of the exhaust manifolds do you have?

now i have about 44mm but i think it is too few.
corvette with ls7 with compressor has 48mm.

I thought 50mm but if it is too much, I lose torque in low rpm, vice versa (small diameter) I will lose hp at high rpm.

tks all

If I'd gone to the trouble of building a high-revving engine, I wouldn't worry about the low-end torque. The car isn't very heavy. I would check what others have done first, of course, but larger diameter sounds like the way. Otherwise you'll be negating the high-revving specifications.

[845ste]

thanks all.
Lee i remember your sound in yellow gtr: fantastic but excessive

I have watched many videos on the topic: it seems that too small you lose hp at high speeds, even up to 10%.

But even if too big, you lose scavening and therefore hp.
very difficult to say.

I thought that many responded by indicating which ext diameter they have with a tuned ls7.

we did a survey, useful to everyone.

here is the video of mine;

https://youtu.be/8qFfFovluVA

however from pc (megasquirt) it seems that it is going very well as it is now, because we had to give it an ocean of gasoline beyond 5000rpm up to 8000rpm.

before I had an ls3 tuned: up to 4 / 5000rpm the amount of petrol was quite similar, but the huge difference is over 5000rpm