primary, crossover, and downpipe sizing
primary, crossover, and downpipe sizing just wanted some pointers here, stock 5.3 with a tu1 or tu2 cam, edel vic jr intake eith elbow stock throttle body, decided im gonna run a s475, 96mm, 1.32ar. looking to make 7-750rwhp thru a th400 and 9inch. I have to build my own hotside since its going in an s10 and truck manis wont fit. so, im either going to build full headers, or I was thinking to save money on collectors, I could build manifold style headers, like the set that huron speed sells, with v bands on them. questions are, what size primary will I need? 15/8 or 1 3/4? surely not bigger right? and crossover seems to be ok at 2.5? down pipe is 5inch flange off the turbo, would it be ok to neck it down to say 3.5 inchs? I don't think 5inch will fit in the frame, and 4 inch will be really pushing it. I also want the system to be big enough if I decided to build a forged 370-408 or something one day. thanks for the help guys!
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Joined: Nov 2003
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From: Norn Iron
I read through that thread, and pretty much decided id be going with a 2.5 crossover, but im still wondering about the primarys and down pipe issue since its going in an s10 and packaging is tight, thanks!
9 Second Club
Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
You read through it and still made the decision of a 2.5" crossover for only 750hp ?
Strange.
2" would be more than enough for the crossover and spool faster.
Primaries cant see any reason to go bigger than 1 5/8"
As for DP, I'm sure a very similar question was asked recently. Whilst bigger is generally better, 3.5" would be fine for 750hp if that's all you can squeeze in
If you dump the wastegate either further back or to atmosphere, then it takes some of the load off the downpipe rather than if you were to vent this into the downpipe
Strange.
2" would be more than enough for the crossover and spool faster.
Primaries cant see any reason to go bigger than 1 5/8"
As for DP, I'm sure a very similar question was asked recently. Whilst bigger is generally better, 3.5" would be fine for 750hp if that's all you can squeeze in
If you dump the wastegate either further back or to atmosphere, then it takes some of the load off the downpipe rather than if you were to vent this into the downpipe
2" would be more than enough for the crossover and spool faster.
Primaries cant see any reason to go bigger than 1 5/8"
As for DP, I'm sure a very similar question was asked recently. Whilst bigger is generally better, 3.5" would be fine for 750hp if that's all you can squeeze in
Primaries cant see any reason to go bigger than 1 5/8"
As for DP, I'm sure a very similar question was asked recently. Whilst bigger is generally better, 3.5" would be fine for 750hp if that's all you can squeeze in
^^^ this is what I would build, it will support well more power than your looking for and have the best spool.
in fact a friend is doing this now.
Last edited by nxfirebird; Feb 16, 2014 at 07:58 PM.
at the end of my post I said id like to use the system in the future if I decide to build a bigger motor, possibly a forged 370 or something. once I build the motor, I think 900-1000 would be cool, would the 1 5/8 primary's and 2inch cross over be good for that kind of power also? and waste gate will be vented to the atmosphere, so that will help the downpipe situation
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at the end of my post I said id like to use the system in the future if I decide to build a bigger motor, possibly a forged 370 or something. once I build the motor, I think 900-1000 would be cool, would the 1 5/8 primary's and 2inch cross over be good for that kind of power also? and waste gate will be vented to the atmosphere, so that will help the downpipe situation
I wouldn't move up to something like 1 3/4 and 2.25 until a guy was building something with aftermarket heads with bigger exhaust ports.
you can do what you want with the down pipe and W/G, 3.5 down pipes have flowed more power than you are looking for.
Last edited by nxfirebird; Feb 16, 2014 at 10:44 PM.
was thinking about trickflow heads once I build the 370, I could always build another hotside once I go that route. so it seems like 1 5/8 primary's with a 2 inch crossover and a 3 1/2 inch downpipe is what would be best for me then. would log manifold style manifolds do the job or should I just spend the extras cash for collectors and build a true header? thanks for all the help guys