danmo349

So I'm making a custom intake manifold with plenum for my build. Its a bridgeported s4 with a borgwarner 300sx turbo my question is...since its for a drift build and the fact that it will be tuned for top end power I'm wondering If I in fact should use 4 intake runners off the plenum or if I could have the two runners going to the secondary ports and just have one going to the primary ports and the split will be at the port on the center iron, instead of the stock design that is split up to right before the throttle body. I will be using an aftermarket single butterfly valve throttle body. Any opinions?

Zenki FC3S

sounds dope. i would do 4 runners and a large cylinder plenum just like the 13bRE mani

danmo349

My thoughts are the separated runners are only for low rpm efficiency and idle being that this is a strictly track car it would save me a lot of time on fabrication to do one runner for the primary ports.

Zenki FC3S

yea dude the 4 tubular runners to a flange sounds reasonable when it comes to fabrication

sft3303

Read This:

http://www.stealth316.com/misc/grape...ionsystems.pdf

Many many many factors play into a well designed plenum-runner style manifold which you describe, and you can design yours to increase torque right where you want it just by doing some maths and planning ahead.

My offhand suggestion (should you not wish to read through the whole article) is a smaller plenum with long-ish runners. The longer runners will provide resonance-charging of the intake ports at lower rpms when the turbo isn't fully spooled, and the smaller plenum will help decrease turbo lag and increase throttle response. Exact specs should be left up to you, and are easily calculated using formulas in that paper.

-Note: I've never really thought of how it may effect a turbo car, but tuned exhaust runner lengths have this same affect. If you want to look into going to a tubular turbo manifold to create resonance-scavenging of the exhaust ports, the same principles could probably be applied there as well (although with the backpressure created by the turbo, I'm not certain how this would affect scavenging. Oh well.)

-Jim

danmo349

Thanks Jim I defenently will read through it all and I actually love math( I know kinda lame) I did do a lot of figuring for my divided exhaust manifold here's a picture.



I have build journal going I'm on the mobile app and don't know if I can post the link properly but here it goes

https://www.rx7club.com/build-thread...turbo-1049135/

Maybe this can help give ya an idea why I need to make a custom manifold space is tight.

danmo349

So I got it figured out I think it'll look real clean too. I'm a pipe welder and I work in the cryogenic industry and I was at work today fitting a vacuum jacketed line and it hit me. We do what we call clam shelling pipe that's were you cut it in half the long way to fit it around a smaller pipe mostly done on elbows and tee fittings. So my idea is to clam shell a 90 but weld a divider plate in between then weld the two half's together should fit up nice seeming how the port holes are elongated so it should minimize any porting to get a smooth transition from the manifold to the iron and in my opinion will be athsteticly pleasing. Added bonus us rotor guys are all about 3 right? 3 sides to a rotor 3 apex seals on a rotor and so on so would 3 intake runners look kinda cool too?