i dont think ive mentioned really, but im working on a custom intake manifold. itll use the stock throttle body for now. but im ditching the upper plenum and cutting the top part of the lower plenum off(where the upper plenum bolts on). holy crap are those ports opened up when its gone. im going to weld on 3" aluminum piping. itll be shaped like the 3.4 intake basically, but with a hell of a lot more flow. then im gonna port out the intake manifold. ok its not me, its a guy i work with, hes doing all the work, but its my intake for my car, lol. im hoping itll be completed within the next month or so. ill try to post pics of it soon.

 

i saw an intake like this on the fiero boards, it seemed to work well . . . are you planning on having the TB in the stock location? what about an H design for even cylinder distribution? I had some ideas similar to this for mine later down the road, let me know how it goes.

oh what runner length do you think you'll end up with? its probably going to need some head work and a cam to be really effective if you cut too much off the runners. keep us posted!

 

the tb will be in the stock location. they havent been shortened too much. im hoping to put a cam in before spring comes around, but i dont know if ill be able to. it should have even cylinder distribution since its a Y shape, itll be just like the 3.4 intake.

 

You should test in intake as is to prove it works well with stock parts first. 90% of the possiable buyers aren't gonna be doing a cam swap too.

 

I'll give you guys a heads up on building an intake- unless you do head work also, you are wasting your time.

I have raised my entire powerband about 500rpms over the stock intake and it is better married to the exhaust sacavage potential in upper rpms But the power output will not get any higher until I get extensively modified heads. The intake is not the major hurdle, the heads are.

 

yah pretty much, the problem is that it isnt just the heads either, its both . and the heads are only going to do so much with our cam(for the 2.8 at least, 3.4 cam would probably be pretty good).

the first thing(if anything) i'm gonna get for engine performance is some heads, probably super6, id think about headers, but if i have to convert to AIR to pass CA smog with my t5 then the headers are out.

i have a q though, do any of the Al head upper manifolds have the same bolt pattern as ours? probably not, but if so that'd be sweet, cuase i might be able to slap a stocker plenum on top just to make it look legit for smog. i would much rather get some aluminum heads than super6, but i would also like to be able to register my car, so yeah.

 

The intake and the exhaust are the major blockups...

After that, our stock cam is completely tiny. A jump with stock intake/exhaust to the MTC-5 camshaft, and new valve springs added a nice chunk of midrange power.

The heads do need attention, but according to the V6 Performance Bible that Dean posted, 1.5hp/ci is possible, with minor porting work.

I do agree, though, get in there and smooth everything out - it certainly won't HINDER performance!

 

I was under the impression that the intake side on our engines is what suffered. From the heads to the air filter.

2.8 cam and 3.4 cam are so damn similar, you wouldnt notice the difference.

What guys do on the gp board who are under siff smog laws is port the manifolds and smooth them out a bit.


I think the only FWD intakes that are close or similar to ours is the early FWD ones that still used the iron heads. But its worth reasearching.

 

I gasket match ported the intake, while still w/ the 2.8, and also I gasket match ported and polished my heads. and did not really notice any serious gains, but we also added the larger cam...

But the new intake and TB really opened up the cars TQ... we will see on the HP once I get the A/f fixed up!

 

i didnt get a chance to get out to my buddies shop until tonight to get these. theyll give you rough idea of what im going for. i have a couple more pics that i didnt post where you can see that the lower plenum was shaved to open the ports and allow to accomodate the new pipes, i can post them if anyone is curious. heres the link to my site:

http://www.cardomain.com/ride/461596/3

 

heck if you finish making this and it works good what would you charge to make another?

 

After looking at the pics... you are really gonna have to open up the runners thru porting... I know you think you opened them up just by cutting them, but effectively you have not. Yes you cut out the turn in the stock intake which is a bit of a restriction. But its like taking a straw... the opening and what it will flow is the same if you cut the opening straight like it comes, or on a angle... Though the angled cut will look like the opening is larger, it really is the same size. Its only the perception of the size that has changed.

So my thought is you can reall port the runners without the angled part to open them up! Go for it.

 

I was just about to say the same thing, but you worded it much better and with an anolgy.

 

if i may id like to point out a few things, u have a good idea there but there are a few downfals to ur design, the first and biggest one is is short runner lenght, thats great for building low end tq but its gonna hurt u alot on the top end. that design would benify greatly by etending the lowe rplenum runners up about 2-3 inches. the shorter the runner u will make more low end tq but hp will suffer and it will run out of brathe at mid to high rpms, theres actually a formula for figuring out runner lenght for rpm range and such.ill have to see if i cant find it for u.And also that design would benifit from 2 seperate plenums/throttle bodies

 

You have that backwards. Longer runner promotes low RPM torque while shorter runner promotes higher RPM HP.

 

tell that to all the guys that use long runner manifolds in drag racing,but whatever im not here to argue with anyone

 

Yeaa just look at high rise manifolds for carbs... They all say for high rpm's.. What do you guys think about 6 inch runners??

 

Sounds like the dual plane and single plane intake debate.

single is of course better let the fur fly.

 

the 2.8 motors fall off bad at 4,200 rpm badly so u need all the help u can get at upper rpms, and since displacment is down u need to rev high to make good power, look at my motor granted i have that huge cam but i make all my power above 3,000 to 7,500, though my stock manifold is still hurting me badly. though mine is heavily ported and modified

 

Your 2.8 might but not mine. It pulls hard from 2500-6000+ with no signs or feel that your out of the power band. Red line is the only thing that makes me shift for safety sake. Though if I am racing I don't even look and rev it like a dirt bike. As high as it wants to go until it stops pullin

 

Id just like one so i can access the fuel rail and all the stuff under the plenum without having to remove everything.

 

gumby i meant stock 2.8's fall off around there mostly due to intake design and the small lil cam

 

Actually look again, they are pretty short.

Tunnel ram is for a different purpose, to get the shot from the carb barrel directly to the intake port, also where split carbs became popular.

Case in point:

Taurus SHO, with the Yamaha 3.2 and 3.0L engines, they used the long runners at lower RPM and when the throttle was opened Vacuum would drop and then switch over to the shorter runner.

There was another engine that does this, but don't recall it.

Then in the new Cobalts, they have this similar deal, but is electronically controlled, to switch between the long and short runners.

 

im not talkign about tunnel ram manifolds but whatever ive buillt more then enough engines to know what works and what dosent

 

yeah, short runners are for rpm hp and long runners are for more tq. the 2.8 actually should be a pretty high revving motor with the shorter stroke that it has. the heads and intake kill it...headers help but the heads and intake are a big problem. but, rpms aren't going to hurt that motor too easily.

 

The Chysler 300 V6's also have electronically switched long to short runners when the rpms increase.

 

i will be porting out the intake plenum and manifold as well as adding the MTC-5 cam. i found the cam through summit for $60 and a Crower kit w/ lifters, springs, retainers and timing chain for $170 so im pretty sure thatll be my final setup. i have also come across a co-worker who does custom chips. he said hed hook me up for nothing more than parts if i help him swap an engine!!!

 

Well the truleo intake I am now running with was a VERY VERY significant TQ builder (even with horrible A/F ratio!)... the runners are longer & did away with the sharp turns of the stock plenum and mid section... The HP gains are pending my computer tune...

The darn guys I was originally trying to get to extrude hone my intake... well they said they would only port more then the standard 1mm clean up on a drag set up because of the TQ it would loose, opening up the stock ports without increasing the runner length. They told me I was nuts to open up the airflow on the car at all (dumb girl syndrome) Never listened that is was a cammed 3.4 with headers, still running a 2.8 intake. Argued the idea with the guy for about 20min. That and the high price they wanted made me go with the Truleo design... longers runners, larger and claener turns... ability to mate up a larger TB!
Anyway.... the extrude hone place's summary... TQ = longer runner length & HP = Larger intake & runners.

I also think this proposed design, shortening of the runners in any way will hurt more then help. Though the design would look amazing with twin TBs... HEHEHE (sinister laugh) The pics just gave me that vision

 

well the intake wont cost me anymore than parts so i thought wed give it a shot. itll probably be a couple months or so before i get a chance to try it and it probably wont be anything more than the dragstrip. but i dont have the time to run it w/ just the intake and then just the cam so it wont be accurate at all. sadly i wont have anything to base it on other than the cam and intake together. maybe ill get a chance later on down the road to reinstall the original intake and see what the differences are. but with going back to college, ill see what i can do for you all. i wish i could get dyno numbers to show though