Turbo plenum design

[Scottymac]

Currently thinking about building a custom plenum for my 3sge+t beams engine . What things should i look out for? Do i make body large with small runners or large body with long runners ? I would like to get a good throtle reponse rather than high rpm power. Anyone had any success with making plenums?

[Roman]

Any reason not to run altezza one? Youd struggle to make a better one.

[flyingbrick]

Hi there.

Usually it seems that if it looks right...it will be close enough.

[mjrstar]

If you can get away with a factory cast inlet manifold it will last better than a custom sheet aluminium folded unit.

[Yowzer]

[Yowzer]

And now here's some actual helpful information other than "Just use a stock one"

 

http://www.urbanracer.com/articles/anmviewer.asp?a=3344

 

Seriously guys, this is tech talk. Get techy on this shiz.

[flyingbrick]

Good link Jess!

I should care a little more as need to make a plenum for my ls3 intake base..

[Yowzer]

Duel plenum intakes intrigue me. Shall do more research into their design once I find a computer.

[kpr]

As  Roman Dave said, isn't that easy to make an inlet manifold better than a late model factory one.  if power delivery is good, likely have trouble making something better.

But

once you get to a certain point they can make a huge difference. tuning running lengths to work at high rpm to suit big turbos etc..

when building there's lots to get right to make a good inlet manifold.  bellmouths, small amount of taper to increase velocity, length for correct rpm tuning.  plenum volume and shape.

 

if you want throttle response  don't run a big plenum.   they are fine once you have a few rpm on, but low rpm not so good.   if i ever get around it. my next inlet manifold will run itb's, with a fairly large  plenum(possibly a dual) . so the initial throttle response doesn't suffer

[RUNAMUCK]

Boom!
http://horsepowercalculators.net/intake-manifold-design/intake-manifold-design

 

(Link will take aaaages to load btw, but fully worth it)

[Roman]

As  Roman Dave said, isn't that easy to make an inlet manifold better than a late model factory one. 

Oh yeah I should have elaborated a little better, but reasons I say stick with the factory one when it comes to the Altezza:

 

It has bellmouths on the end of the factory runners, and a runner length that's optimized for about 7000rpm... The only way to get that rpm lower is to run longer runners, which no one ever does when making an aftermarket one. Especially for turbo.

 

Yowzer have you ever noticed how an Altezza intake manifold has the throttle body a lot lower than the height of the runners...

It uses that same trick as per your picture, to balance the flow to the runners, but by making the air wrap around a corner slightly to the bellmouths.

 

It's also got an effing big throttle body on the front of it. (72mm outlet)

 

It also has a rubber isolator as a lower part of the intake manifold which stops the engine temp from heatsoaking the manifold.

Sooo....

 

-It flows well into the runners

-It flows well into the throttle body

-It acheives a good balance of flow between cylinders

-It acheives good engine response (Converting the throttle body to 100% cable pull makes it a bit nicer, rather than ECU controlled)

-It's thermally isolated from engine heat soak

 

I cant think of any part of it which would need upgrading to stuff a lot more air in it, unless the plenums split in half when they have a big stack of boost added. But I dont think I've heard of anyone doing that before.

There are plenty of cases where making a new inlet manifold with bellmouths etc is a big improvement over the factory item. Especially for rough cast manifolds. But this is one example where the cost outweighs the (potential) benefit in my opinion.

 

I'm not a "Toyotas done everything perfect already" fanboy, there are plenty of parts on an Altezza engine worth replacing or modifying (oil pan, flywheel/clutch, exhaust manifold, few other things)

But the inlet side of things is pretty fancy already... Why spend time and money if you dont need to.

[Scottymac]

Thanks for all the info guys has given me a good starting point. Only problem with the factory one is that it doesnt fit in my corona it is pretty cramped hence needing to make a custome one or butchering the factory one a bit.

[Roman]

A bit tight near the master cylinder?

 

Yeah they're a big bastard. Haha.

 

Maybe see if you can bandsaw the runners and chop a bit of length out and weld back up.

Otherwise if you do make a completely new one, retain the two lower portions of the runners, the alloy bit on the head and the rubber part.

 

Bolt what you make on to that.

 

another option is that you can use a FWD beams plenum, chop the runners off and turn it around 180 degrees... You end up with a low mount plenum instead that is closer to the side of the motor, with throttle body out the front.

[Rookie]

What do you guys use to work out inlet lengths? Pipemax?

[Testament]

First principles dave, get out your calculator

[Yowzer]

In a boosted application running ITBs, would you run as big a plenum chamber as practical, as you wouldn't have the low down throttle response issues of a single TB on a large plenum?

[Yowzer]

Just reread KPRs post which pretty much confirmed that for me