making an intake manifold
06-03-2008, 09:54 PM
#14
0.0 BAR
Join Date: Oct 2003
Posts: 0
Re: making an intake manifold
Originally Posted by Big J
Fluid dynamics says they work better off the floor, but the stacks are modular and install flush using a 3" hole saw. Garrett GT3071R says the air will be motivated to flow regardless, so an X% loss of flow of 1 vs the other I can live with.
There's no well defined formula for intake design that won't make you head explode due to math overload. I went with 1.75" id runner material because it didn't require any extra/special fab to fit when smashed to an oval, and it's about 1/4 larger in diameter the the stock runners (at the middle of the manifold). Granted there isn't an ideal, or any for that matter, taper built into the runners. The funny thing is the factory runners are smaller towards the plenum and open up towards the head, *** backwards of anything I know about intakes and velocity.
The plenum is about 3.1L, about 80% larger than the stock plenum and about .6L larger than the displacement of the motor. The long runners on the stock manifold are about equal, volume wise, to the volume each cylinder displaces. It's part science and part guess work. The runners will be how ever long they can be and fit under the hood and behind the valve cover, probably about 12". My guess peak TQ will be about 5-6k, but factor in the 272/264 cams and I have no clue, lol.
Worse case it overloads one cylinder and blows the motor, or is nothing more than a shiny underhood ornament. Judging by the crap I've seen major companies have put out as intake manifolds (not for this car and probably never) I'm willing to bet it'll do ok.
There's no well defined formula for intake design that won't make you head explode due to math overload. I went with 1.75" id runner material because it didn't require any extra/special fab to fit when smashed to an oval, and it's about 1/4 larger in diameter the the stock runners (at the middle of the manifold). Granted there isn't an ideal, or any for that matter, taper built into the runners. The funny thing is the factory runners are smaller towards the plenum and open up towards the head, *** backwards of anything I know about intakes and velocity.
The plenum is about 3.1L, about 80% larger than the stock plenum and about .6L larger than the displacement of the motor. The long runners on the stock manifold are about equal, volume wise, to the volume each cylinder displaces. It's part science and part guess work. The runners will be how ever long they can be and fit under the hood and behind the valve cover, probably about 12". My guess peak TQ will be about 5-6k, but factor in the 272/264 cams and I have no clue, lol.
Worse case it overloads one cylinder and blows the motor, or is nothing more than a shiny underhood ornament. Judging by the crap I've seen major companies have put out as intake manifolds (not for this car and probably never) I'm willing to bet it'll do ok.
06-03-2008, 10:10 PM
#15
3.0 BAR
Join Date: Oct 2005
Location: St. Augustine FL
Posts: 3,936
Re: making an intake manifold
Originally Posted by weiRtech
the cosworth engines in champ cars made over 800hp on 2.65L engines boosting only 6psi and their velocity stacks almost touch the roof of the plenum.
06-03-2008, 10:51 PM
#17
0.5 BAR
Thread Starter
Join Date: Dec 2006
Posts: 141
Re: making an intake manifold
Originally Posted by weiRtech
i agree there is no well defined formula that works, that is why fluid dynamics theory might say they work better on the floor, but real world application might say otherwise... i'll just look at what others are using and what works for them and try to use their research and hard work to my advantage. the cosworth engines in champ cars made over 800hp on 2.65L engines boosting only 6psi and their velocity stacks almost touch the roof of the plenum. i don't know about anyone else, but that says something to me.
06-03-2008, 11:07 PM
#18
3.0 BAR
Join Date: Jul 2006
Posts: 2,349
Re: making an intake manifold
Something about a S type motion that helps velocity.
where as a 90 motion dose something to the flow.
The was a flow pattern vid i saw a long time ago about sitting offf the floor was a better idea.
I think that was for N/A apps.
I don't know from first hand so im going to STFU now.
where as a 90 motion dose something to the flow.
The was a flow pattern vid i saw a long time ago about sitting offf the floor was a better idea.
I think that was for N/A apps.
I don't know from first hand so im going to STFU now.
