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R32 Plenum Makings.

salival

By salival,
in Fabrication

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salival Enthusiast

salival

Posted
Posted (edited)

Hi guys,

After my radiator build and my surge tank build, I thought i'd show you the plenum i'm building, or what I have so far atleast.

It's an RB20DE bottom half with the runners cut off, I've then welded in 50.8x3mm wall 55mm long extensions then welded on 5mm plate as my backing.. I haven't had much time to do much else yet, but I'll get onto the rest soon.. but I thought id give you some tease pictures..

I cleaned the plenum up, wire buffed the gasket goop off and used the chemical I normally use to clean alloy with.. Before welding it all together, I preheated it in our big bake oven to 380deg c for 15 minutes to stop any potential warpage.

Anyway, onto the porn..

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As my last posts of the stuff i've made, comments, complaints or anything..

Thanks,

Scott

Edited by salival
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salival Enthusiast

salival

Posted
  • Author
Posted
looks the good so far.

u planning on testing it after your done?

Hiya,

I'll pressure test it to 25psi.. but flow test? no..

It's only a poxy rb20.. I mainly want it for the look and the reduced pipe work.. I do all this work on saturdays at my work.. so it's costing me nothing (including materials)

salival Enthusiast

salival

Posted
  • Author
Posted
mate u might wanna throw some trumpets on each runner to increase air velocity/speed/distribution

I'm not using trumpets on this particular one..

I've welded inside/outside of each runner where it meets the backing plate.. I'm going to machine a radius on each runner so it merges nicely..

blv Contributor

blv

Posted
Posted
I'm not using trumpets on this particular one..

I've welded inside/outside of each runner where it meets the backing plate.. I'm going to machine a radius on each runner so it merges nicely..

thats exactly how i want to make my rb20 plenum, i just need an aluminium welder at work... damn not having one anymore...!!

  • 1 month later...
STR8E180 Proficient

STR8E180

Posted
Posted
I'm not using trumpets on this particular one..

I've welded inside/outside of each runner where it meets the backing plate.. I'm going to machine a radius on each runner so it merges nicely..

after doing some research i learnt that Actually flows more then having internal trumpets, the advantage that trumpets have is it has more air velocity and the air distribution is more even threw all cylinders

alot if not all of the jap brand plenums do not use thrumpets as they are more worried about air flow

  • 2 weeks later...
ISL33P Proficient

ISL33P

Posted
Posted

you will find that a radiussed bellmouth sitting on your base is the best for flow, which is the main reason why people go for a different plenum.

greedy 2jz, jun sr20 & maybe greedy rb26 all have raised bellmouths

  • 4 weeks later...
rb2240sx Newbie

rb2240sx

Posted
Posted

I want to see more! Im actually doing this same thing. Im using trumpets but am going to make the very outer tip of the trumpet flush with the plate instead of sticking out into the plenum. Its like what your doing but with less machining......hopefully. Are you putting yours into a 180sx? Im wondering how far mine can stick out without hitting the strut tower and giving me good clearance? Very nice job on the tig work too!

  • 2 weeks later...
Nigel. Rookie

Nigel.

Posted
Posted (edited)
whats the best way of cutting the cast runners of the flange??

How i've done this on the few that i've made has been to use a 'woodworker's' bandsaw then facemill all the runners to a uniform height. Usually at a 10deg. angle down to help with clearence around the brake booster and clutch master.

Trumpets / Bellmouths are an absolute must!! I made a die from 75mm BMS bar then pressed it into the alloy tube. (before welding)

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Edited by Nigel.
salival Enthusiast

salival

Posted
  • Author
Posted
i personally think u should have welded it on both sides (inside and out side) so that u can machine down the welds on the out side of the plenum so it looks like its all one peice from the out side

img1158b1l.jpg

Ah, but you see.. there is a flaw in your plan..

I love welds :(

  • 2 weeks later...
(--MeUnVmosT---) Newbie

(--MeUnVmosT---)

Posted
Posted (edited)
post-8270-1193540998_thumb.jpg

im at this same point with my manifold,. what are u going to do about the step in the runners? what tool u gonna use to even them out? cuz i did the same thing. used 2" tubes for runners but the stock runner is about 1.90" where as the tubes are perfect 2"? is there some kind of grinding tool that has some length to be able to get inside?

Edited by (--MeUnVmosT---)
  • 4 weeks later...
psi Experienced

psi

Posted
Posted

you guys are doing a great job..

I have started my project (11 months ago! lol) where i was using trumpets inside the plenum.

however, I have been looking at using shower form injection. This is where the injectors are mounted directly above, facing down the inside of the trumpet.

Indy cars do this. they say it helps build topend power.

The idea is that the 'shower' of fuel helps capture extra air and force it into the cylinder, this also gives better atomization.. which should mean more power for the same amount of fuel..

My plan is to use a shallower plenum with similar volume, with indents in the roof of the plenum above the trumpets for the injector bosses. LOTS of work! My current problem is tring to get manifold runner length while still leaving space for the injectors. I have been measuring and calculating how well it will work if i do a plenum that sits ontop of the existing runners.. I am concerned that the 'shower' of fuel may stall with the longer bent runners. i know somebody with a flow bench, so I have not touched the project until I do more research. cos i currently have to many variables.

did that hurt anybodies head? did mine!

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