TB questions?
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From: Harford co. MD
TB questions? So a few questions regarding TB choice for my build which is a TT LSX 427 with goals of around 1-1200whp what size TB should I go with had plans on a DBW NW 102mm however the sheet metal intake I have has a 95mm opening which I would have to open up and lose the o-ring seal and use a material gasket is that a issue? And how are DBW on FI?
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From: Norn Iron
95 will easily support those goals....and about another 5-600 I'm sure
Factory LS2 DBW unit is supposed to be very good, with a much stronger motor than some of the aftermarket stuff.
You do not need a big TB when blowing boost through it, and in most cases nor will it benefit you.
Factory LS2 DBW unit is supposed to be very good, with a much stronger motor than some of the aftermarket stuff.
You do not need a big TB when blowing boost through it, and in most cases nor will it benefit you.
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From: Harford co. MD
Just wondering if the gasket will hold up to say 20psi of boost. Peak Perf. has a nice 102mm gasket that's thick and has metal reinforcements they said it should be no issues.
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From: Harford co. MD
I just dont want to have a bottle neck at the TB being it would be the smallest diameter compared to the 4" charge pipe i know that dont matter much with FI though.
Last edited by 6togo; Oct 3, 2014 at 06:42 PM.
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From: Harford co. MD
The outlet of the turbos is 3" ea and i planned on having a custom intercooler made with two 3" in one 4" out which dont sound to big considering your basically merging both turbo's.
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From: Norn Iron
Strictly speaking it may not sound big given the in/out.
But for the power goals there is nothing there that would pose any restriction whatsoever unless there were dozens of 90deg bends
Not sure which turbo's your using, but almost sounds like a pair of BW's ? Some of them have a quite bulky 3" OD outlet, ID is still closer to a 2.5" though.
The pipework should be nice and efficient in terms of flow, some might like smaller pipes as they'd claim better spool as less pipework to fill. Hardly matter really though.
But there is absolutely no need for huge TB's when blowing through them, and they'll rarely offer any benefit unless pushing huge power.
But they can offer negatives to throttle resolution at smaller openings simply because they flow more air than the engine actually needs, so as an extreme example, 50-100% opening might not make any difference because at 50% it already flows all the air the engine can consume anyway.
But for the power goals there is nothing there that would pose any restriction whatsoever unless there were dozens of 90deg bends
Not sure which turbo's your using, but almost sounds like a pair of BW's ? Some of them have a quite bulky 3" OD outlet, ID is still closer to a 2.5" though.
The pipework should be nice and efficient in terms of flow, some might like smaller pipes as they'd claim better spool as less pipework to fill. Hardly matter really though.
But there is absolutely no need for huge TB's when blowing through them, and they'll rarely offer any benefit unless pushing huge power.
But they can offer negatives to throttle resolution at smaller openings simply because they flow more air than the engine actually needs, so as an extreme example, 50-100% opening might not make any difference because at 50% it already flows all the air the engine can consume anyway.
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From: Harford co. MD
Yes to the BW's which is probably what I will use or the comp 6767 units and I do understand what you saying about the TB being the are is being forced I'm just tying to make everything be uniform in size which may pose to be a challenge.
If I could find a DBW 95-96mm TB I would use one of those and not touch the intake opening!
If I could find a DBW 95-96mm TB I would use one of those and not touch the intake opening!
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From: Harford co. MD
I just checked out the itake opening and if i open it up any bigger in will not have enough material to support the gasket so it will have to be 95mm or smaller. I was hoping to get a TB that was pleasing to the eyes to go on the polished intake i guess a stock 90mm can be cleaned up and ported.
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was the cost worth the gain thats hard to say as some would just crank the boost up but in some cases that isnt always possible or best answer
with said my lsx427 has a 102mm tb
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From: Norn Iron
Perhaps the intake itself was the main restriction.
2 x 2.5" OD pipes have a CSA of 9.8sq in
1x 4" OD pipe has a CSA of 12.5sq in.
That's ignoring wall thickness and running off OD so actual numbers may be slightly less. But you can see the 4" has a far larger ability to flow air than the two smaller inlet pipes. So they are the main restriction in the system up to that point
Not the throttle.
A 3.5", ie 90mm OD has almost identical CSA to the two 2.5" pipes, just a fraction smaller.
But as the intake will have longer smaller diameter runners, smaller intake valves that are only open for a short period of time etc etc. More often than not the pipework, throttle etc will rarely be the main restriction with boost.
Besides all that, people have run deep into the 8's with stock LS6 intake and TB. So there has to be a value for money aspect considered. Clearly it can make lots of power without any difficulty. Can others do better ? Probably, but it's still seems rare to see genuine back to back comparisons proving so.
Only recent one I recall was someone removing their fast to go back to an LS6, and it made no difference whatsoever. I dont think he posted graphs though to see if that was the case everywhere in the rpm range, and also how part throttle etc might have been affected. Which is after all where street engines spend a lot of their time.
2 x 2.5" OD pipes have a CSA of 9.8sq in
1x 4" OD pipe has a CSA of 12.5sq in.
That's ignoring wall thickness and running off OD so actual numbers may be slightly less. But you can see the 4" has a far larger ability to flow air than the two smaller inlet pipes. So they are the main restriction in the system up to that point
Not the throttle.
A 3.5", ie 90mm OD has almost identical CSA to the two 2.5" pipes, just a fraction smaller.
But as the intake will have longer smaller diameter runners, smaller intake valves that are only open for a short period of time etc etc. More often than not the pipework, throttle etc will rarely be the main restriction with boost.
Besides all that, people have run deep into the 8's with stock LS6 intake and TB. So there has to be a value for money aspect considered. Clearly it can make lots of power without any difficulty. Can others do better ? Probably, but it's still seems rare to see genuine back to back comparisons proving so.
Only recent one I recall was someone removing their fast to go back to an LS6, and it made no difference whatsoever. I dont think he posted graphs though to see if that was the case everywhere in the rpm range, and also how part throttle etc might have been affected. Which is after all where street engines spend a lot of their time.
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Perhaps the intake itself was the main restriction.
2 x 2.5" OD pipes have a CSA of 9.8sq in
1x 4" OD pipe has a CSA of 12.5sq in.
That's ignoring wall thickness and running off OD so actual numbers may be slightly less. But you can see the 4" has a far larger ability to flow air than the two smaller inlet pipes. So they are the main restriction in the system up to that point
Not the throttle.
A 3.5", ie 90mm OD has almost identical CSA to the two 2.5" pipes, just a fraction smaller.
But as the intake will have longer smaller diameter runners, smaller intake valves that are only open for a short period of time etc etc. More often than not the pipework, throttle etc will rarely be the main restriction with boost.
Besides all that, people have run deep into the 8's with stock LS6 intake and TB. So there has to be a value for money aspect considered. Clearly it can make lots of power without any difficulty. Can others do better ? Probably, but it's still seems rare to see genuine back to back comparisons proving so.
Only recent one I recall was someone removing their fast to go back to an LS6, and it made no difference whatsoever. I dont think he posted graphs though to see if that was the case everywhere in the rpm range, and also how part throttle etc might have been affected. Which is after all where street engines spend a lot of their time.
2 x 2.5" OD pipes have a CSA of 9.8sq in
1x 4" OD pipe has a CSA of 12.5sq in.
That's ignoring wall thickness and running off OD so actual numbers may be slightly less. But you can see the 4" has a far larger ability to flow air than the two smaller inlet pipes. So they are the main restriction in the system up to that point
Not the throttle.
A 3.5", ie 90mm OD has almost identical CSA to the two 2.5" pipes, just a fraction smaller.
But as the intake will have longer smaller diameter runners, smaller intake valves that are only open for a short period of time etc etc. More often than not the pipework, throttle etc will rarely be the main restriction with boost.
Besides all that, people have run deep into the 8's with stock LS6 intake and TB. So there has to be a value for money aspect considered. Clearly it can make lots of power without any difficulty. Can others do better ? Probably, but it's still seems rare to see genuine back to back comparisons proving so.
Only recent one I recall was someone removing their fast to go back to an LS6, and it made no difference whatsoever. I dont think he posted graphs though to see if that was the case everywhere in the rpm range, and also how part throttle etc might have been affected. Which is after all where street engines spend a lot of their time.
now ppl are going faster with SBE and baby cams so whats wrong with trying something that works little better?
every boosted setup ive done either had a 90 or 102 mm tb on it and always noticed it made more power with less boost then the other guy who used smaller TB and intake.
this also goes along line that all builds have used a 4" pipe feeding the TB vs smaller that many run