sen2two

heres a pic of a manifold i want to fab up. (and quick description)



the plenum will be 4 inch tubing barely wider than the stock top manifold.



the runners will be 90% bends about 7-8 inches. havnt really mocked anything up yet. maybe about 9-10 inches...(not sure what size tubes to use for the runners, any tips?)



the tube from the plenum to the throttle body will be about 2 inches long and equal (or a little larger) than the back side of the throttle body. (looking at using the stock FD throttle body for simplicity with the throttle cable and TPS. but we'll see)



i know where to get some weld in injector boss... i wanted to keep it just 2 injectors in my upper manifold. for simplicity again. stay with just 4 injectors. im not sure if my Apex-i PFC can handle extra injectors...??? anyways...let me know what you think.





oh...dont be an *** hole. educated responces only. people with experience and knowledge. thank you...

sen2two

oh...also, i wanted to put velocity stacks inside the plenum. how would i go about sealing them in? cut the plenum in half then weld the velocity stacks in and then weld the plenum closed??? seems the wrong way to go...but this is my first intake manifold...

1Revvin7

Educated responses from the internet forums......... right..



you don't want velocity stacks on forced induction engines.

TYSON

Why? They work, airflow is airflow, under pressure or not.

Lynn E. Hanover

Since you have not published the exact criterium for not being an *** hole, nor the amount of experience needed to qualify as a source for your answer, responses cannot be educated, so my guess is that you want an educated responder?



For a 4 port engine, I would form up the ideal manifold from childrens modeling clay. You can put in turbulance generating devices and the bosses for your injectors. I would avoid the plenum, or log manifold.



Once you have your 180 section built up, let it sit for a few days and coat it with epoxy and fiberglass tape,

and once that hardens, wash out the clay with Kerosene. The inside finish will be amazing.

Epoxy in a short length of steel tubing as below.



Combine the port runners from each housing within 8" of the port. I would keep the stock runner cross section through the collecter and then just a bit above that cross section over the engine to smaller individual TBs. So if you measure the two port faces feeding the front housing as having a total of 4 square inches, I would join those two runners and continue the run to the TB with a tube of slightly more than 8 square inches. Say about 9 or 9 1/2" square inches. The idea is to have a rather constant velocity through the manifold, with the highest velocity just at the port face. So now the horizontal run could, if you like, have a slip joint like a trombone slide to play with for finding the ideal length for your application.



If your plan is for huge power up high, go ahead and make the runners a constant taper up to your TB size and maintain that size in your hoeazontal run of tubing.



Make the inside of the bends flat, so the runner looks like a "D". Much better flow and less turbulance drag.



A similar method is used to make tabs and brackets of fiberglass reinforced epoxy. Most of the clay can be reused. Let it dry out, wrap it in plastic wrap and put it in a cool place. You can make great looking air horns this way as well. Make up the clay form so it makes the ID of the horn.



There you go.........



Lynn E. Hanover



a 64 year old kid.



Its 11:00 PM. Do you know where your TDC is?

j9fd3s

if anything most really high hp apps keep the stock (ported) manifolds, if anything the upper gets shortened by a couple inches

sen2two

what about using a lower manifold like this usually made for webbers?

sen2two

and then just making a top manifold like this....?

j9fd3s

thats what mazda did in 81... intake design isnt critical on a turbo, if anything you want to focus on the exhaust, and turbo sizing

sen2two

so my little idea is dated huh??? lol....



i just really dont want the stock intake manifold. and im sure that second set-up would make more power...plus since i would be making it myself, it could accually come out cheaper when i sell the FD stock set up...