I will be making a custom upper+lower manifold for my fd3s.
This is my first drawing of the upper.

The runners will be 40mm on secondary and 32mm on primary, inlet 75mm. material will be aluminum.

Any suggestions?

 

Are you going to be making a custom throttlebody or how do you plan on attaching and sealing the stocker?

 

What are your goals for this?

It seems to my untrained eye that the runners should be attached flush to the manifold. The manifold is much larger than the runners, which would appear to be quite turbulent where the flow would enter the runners.

But it all depends what you're trying to do.

Dave

 

^
yeah, i'm curious as to what purpose this would serve? how do you plan on mounting it to the throttle body and the lim?

 

Will use a single throttle for this one.

 

My goals for this is to obtain better flow than the stock
upper+lower manifold (especially the lower). I know the stock will flow for well over 600hp but id like to keep my boost as low as possible. Will hopefully be hitting 500rwhp at only 15psi (on e85).

You are absolutly right, i will make the stacks flush since its proven to be better. The volume for the plenum right now is about 3.5liters.

This is not the final design, this is just a first drawing to get some feedback! what plenum design would you prefer?

 

I would like to see the sides of the plenum flush with the outer sides of the intake runners as well.

 

Why not just get a cosmo UIM&LIM...thats what i did

 

^that's what i have for sale too, cerma-coated w/ all gaskets and block off plates

sorry to *****

 

it is not as much fun :P more fun to build something that not everyone have on their car.

 

fyi - look for posts from rotarygod here and on nopistons. he shared a lot of info on intake manifold design. there have been a few threads on other parts of the forum about this too if you want to search for them.

good luck on your project.

 

And this is how it ended up.. not exactly like the first drawing

not finished yet though.

 

**** that thing is huuuuuuuuuuuuuge!!! The final product should be great!!! I wonder how much extra lag that will cause...you'l probably gain a shitload of torque and hp top end but lose a fair bit further down the rev range...

 

I don't get it. Looks like a stock intake manifold hacked in half with a fabbed up box welded on it. I guess the proof will be in the dyno numbers, or perhaps some way to measure flow to see if it increased/improved anything. If anything I suppose it may be slightly lighter ?

 

what kind of car is it going in??

For sure not going to fit in an FD.. I'm no expert, but I would start off by maximum size intake port you are going to use and the biggest TB you are going to use.. I think you also need to consider how this volume of air is going to be moved inside and thru the runners and where you are going to mount the injectors.. If you are going to mass produce this item, there will be few people who's willing to port match..
ANyhow, I think its a good start!! Good luck with your project!

 

i think honestly you will see an improvement considering the factory manifolds have no plenum for which to store pressurized air. i myself have always wanted to see a custom project with shorter runners and a larger plenum. btw, what is the volume of just the plenum you have built? ie. how much water could you fill it with? In most cases you would want a volume equal to the engines displacement. i think just by looks alone that is approx 2.5 liters which depending on how you calculate the 13b's displacement is a good size.

 

Who did the welds on that manifold?

 

alot of experts on this forum!

This intake fits in an FD. (i think pictures makes everything look bigger?) Total area of runner is also same as stock.

if you look at a stock manifold and throttlebody both primary ports are fed by a a single 45mm throttle (which i see is a big restrictor for my big primary ports) now all ports gets fed as much as they need and there are flush velocity stacks inside the plenum.

Did a flow test in one secondary runner and it gained 25CFM against just flowing the port, gained 10% compared to a stock manifold. With better designed primary runners total flow will be much better

we'll see what it will perform on the dyno!
I've done all the fabrication and welding, bought my TIG one month ago, that explains the look of the welds... the intake will not be mass produced, it is for my own car and if there is something that needs to be modified, no problem!

 

haha, alright just making sure a shop didn't give that back to you with welds like that. TIG sure is fun, isn't it?

 

one of the keys is reversion and runner length. i learned this running a 2 liter 4 cyl race motor w two DCOE Weber 45s. we varied the runner lengths which situated the standoff just inside the butterflies. at times we had the standoff outside the airhorns!

by changing the runner length we moved torque around and it had a major effect on hp.

i wouldn't have a clue as to what would be the hot setup for the rotary. plus since it is turbocharged it would be impossible to see where the standoff situates.

you'd have to do it on the dyno.

congratulations on doing something creative. please do keep us informed.

howard coleman

 

Love both of the manifolds, finally someone has done something. I will be very interested in seeing some numbers! Keep us updated

 

Not to discourage creativity, but my biggest question is why? Ppl have made almost 800rwhp on the stock manifold...so what's the necessity of going through all that trouble to design a different one?

 

Why upgrade to single turbo when you can achive 350-400hp with twins? why port the engine for better flow? people have made over500rwhp on a stock engine.

It is all about reliability, to achive highest hp with as low boost as possible. even if i only get 3-5% better flow with this manifold its still better than stock, 5% on a 600hp car is 30hp, why boost 1.5-2psi more to achive the same power?

This is my hobby, i love my car and i don't see it as "trouble i have to go through", its fun to create something. Since im doing all the work myself its only my time i invest.

 

No harm in trying something new. Looks great! Interested in seeing performance - keep us posted.

 

Good to see you posted here Gustav! Now let's test a stock stage 1 ported FD manifold vs yours on the RotoTest soon! Oooh just remember we have to build your stage 2 streetport motor first of course! Wonder if Chrispeed has anything to say about the 3 quart of plenum volume?

/Lasse