building an intake manifold, input needed

[sharkey]

thanx for the link, some good info to consider.

[treeZ24]

wow guys, way to give good a good informative discussion on building an intake plenum.

http://www.sdsefi.com/techinta.htm

http://forums.hybridz.org/showthread.php?t=100261&highlight=intake+design

i realize thats not exactly what you wanted to see, but its the only link i have on the laptop. the rx7 manifold was for race only, for street use i'd go with longer runners.

i'll put up a couple more later.

http://www.dune-buggy.com/turbo/intake.htm

http://www.physicsforums.com/showthread.php?t=80364

[bszopi]

Well, here is some more info I dug up...

http://www.60degreev6.com/showthread.php?t=26304&highlight=plenum+theory

124 posts (some off topic) of some plenum theory discussions we had here about 2-3 years ago.

[Superdave]

http://www.trueleo.com/images/fiero_frt_qtr_vac_on_neck2.jpg

http://www.trueleo.com/

nice plenums...


there was a guy a while back that combined a 350TPI plenum and a stock Fbody plenum.. it looked pretty neat too. If i can find the link i'll post it... *edit* found it...

http://www.angelfire.com/crazy3/jimsfirebird/34install.htm

So Sharkey, educate me (and maybe us) on the iron head lower intakes. what's the difference between the early Jbody ones, the fiero ones and the Fbody ones.. anything? any one of them flow better?

Could you pick up a TBI or carb one, get a TB neck that'll bolt to it, make the propper holes for the injectors with a custom fuel rail..


maybe something like this?








good discussion here: http://www.thirdgen.org/techboard/al...t-efi-intakes/

[sharkey]

the lower intake on the mpfi ironhead motors is pretty much the same between fiero, j body and f body. there are some differences in the middle and upper, the j-body one actualy has one bank with 12" runners (from the valve) and one with 19" runners.

with all gen 1 mpfi intakes though, the problem is the tight bend at the top and the port size between the middle and upper. the port size of the head is 2.34 sq/in, were between the middle and upper is 1.42 sq/in, and you have a 135* bend there. this is a huge flow restriction and limits the rpm, however helps the motor make big torque. if i can increase the port size in the middle intake to the same size as the head, it should be able to drasticly increase the rpm range and top end power, it will however sacrifice some bottom end (its a 2.8l, its meant to rev).

the only intake thats "better" is the 3.4l. its a once peice middle/upper and avoids the big 135* (or bigger) bend , but from what i have heard is that it only flows about 10cfm more than the others.

i could use a tbi or carb intake and mod it for mpfi. the problem is, all the carb intakes suck and have very short ports and relitivly small plenum.

as for that camaro intake, it looks cool but realy does nothing but add a big throttle body. it still has the restrictive ports between the 2 intakes and big bend, and small middle runners.

[FallenZ24]

I think the Trueleo Intake is about the best way to go. It gets rid of the middle and upper intakes and all the air-flow problems. Many of the Fiero guys use them on the 2.8/3.4Ls and love them. The only downside is the $600 pricetag.

Maybe you can get some design "cues" from them and make your own. A bigger cam would deffinately help your situation also, maybe the H-272.

-Joseph

[torq455]

yeah baby!!! 272!! that's a cool intake but us j-bods can't use them. hood clearance problems.

[sharkey]

yea i lready have marks on my hood from the fiero intake. i looked long and hard at the trueleo intake, but its just too tall.

i would have gone with the 272 cam, however i have emmissions testing here and was afraid it wouldnt pass. and why bother going with a bigger cam when i cant flow enough air through the intake as it is???

[torq455]

higher velocity!! those smaller runners, with a bigger cam, will have much higher velocity to fill the cylinders with. that will make more lower-mid torque. i've talked to a couple of guys with a stock intake +62mm TB that have said awesome idle and amazing down low torque. with headers it would pull strong to 5500 rpm, but that about it.

[sharkey]

well, with a 60mm throttle body it pulls decent from about 3000-5000, but it just falls off. the stock intake aparently only flows enough air to 4500rpm with a stock cam. sure the small ports and high velocity give good low end, however its just a dog higher up. the other downside of the stock intake is the runners in the middle intake are way smaller at the top, effectivly slowing the port velocity down before it mixes with the fuel and enters the cylender. this is also part of the reason for the bump in the intake port on the head, because the port velocity slows down so much it creates a dead spot in the runner.

[torq455]

sad!

[geoffinbc]

Well that Trueleo Intake has good intentions but the execution is all wrong. First off I don't think I would have used a round plenum. It works but looks ugly. Also I think I would have stuck to rectangular runners. The runners should start at the lower intake and match whatever size the user ports them to and the taper out from there. But at no time should it go to a round tube. Infact I would start with a rectangular piece of tubing at the largest dimension I wish to have and then cut sections of the tubing out and taper the runner gradually to the final size of the ports. I would then build a box plenum with a removable top for any blending or addition of vacuum ports or nitrous ports I wish to add. It just makes cleaning the inside easier. The the last step is actually getting someone to weld it properly. Those welds look like the fell on top of the metal they do not look good at all. Especially for something costing $600.

[ForcedFirebird]

I agree on some points about the Trueleo intake. With mods, I heard of people outflowing their capability.

Sharkey, do you need some flanges to get started? These are machined to a Fel-pro gasket, I mad 5 sets for boostedrs, and he may still have some left (I think he was trying to sell them). Otherwise I could dig up the program and make more. They are 1/2" aluminum...
http://i158.photobucket.com/albums/t...d/100_2707.jpg

[torq455]

agreed! you don't see muscle car intakes that are round from Edelbrock! all rectangle.

wouldn't those flanges act as spacers to add a little more volume and help take that 135* bend out some--make it more gradual?

[86euro]

I like the original idea. If you based the design off of the Lingenfelter TPI, but shrank it down a bit, I think it would work out well for what you want.