Thread: If you could make your own intake manifold

Curious to know what everyone thinks about the length of the runners/velocity stacks on their intake manifolds. Short? Long? We are talking boosted here...

Tempted to keep the stacks short to make up for the turbo lag down low but at the same time I want the intake to be able to keep up with the demands up top.

You want the runners to be longer for down low power due to the Helmholtz resonance. Long runners are not good for top end NA power due to the air restriction. But when your turbo, forcing the air in does help overcome that.

Airbox

Short runner large plenum. Larger the runners the better. Velocity stacks arnt really necessary on boosted applications either. Also large throttle body. Simple as that. Runner length does play some part in what rpm band you want but not as much as n/a application.

The runners on mine are pretty large. The flange is a VE flange that was also ported to match the size of the runners. Ill be porting the head out to match it. Turbo again the larger the better. Plenum size should also be based on the size turbo your running. My plenum is a 3L plenum which is good for up to 67mm turbos for the most part. BMC has a 6L plenum which the guys using 72mm turbos use.

That's a very nice manifold!!!

Please correct me if I'm wrong with this:
Now if you are going with a big enough of a turbo, runner length and width would be a bigger concern due to off boost times.

For NA here are some general sizes

Short Runner = Higher RPM power
Long Runner = Lower RPM Power (torque)
Wide Runner = Higher RPM Power
Shall Runner = Low RPM Power (torque)

At lower RPM's you have to rely more on Helmholtz resonance to make power. You don't need nearly as much air, thus having it bounce shallower and longer runners means the pressure wont be too far out when the valve opens again.

For higher RPM's those shallow and long runners will choke the engine and you will loose power. Thus you need wider and shorter ports (compare VE vs DE/DET runners). VE's are built for higher RPM big cam operation. While DE's are built to be turbo motors, which shipped with small turboes that ran out of breath by before even 7,000 rpm.


DE/DET Runner



VE Runner

you got things mixed up mate

on the exhaust side if u have short runners it will help with response but on the intake side its works the other way around

longer runners on the intake will help with response and low down toque
short runners on the intake manifold will help with top end

this is mine

quad throttle
internal trumpets
injector placement is as close to the cylinder head as possible
injector angle is directed to spray fuel right behind the backs of the valves

hypertune billet intake manifold

3 piece billet inlet manifold
internal trumpets
injectors are placed as close to the cylinder head as possible
injector angle is directed to spray fuel behind the back of the valves

Going to be building my own manifold...but wow^^^ that thing looks robot built. Amazing.

Where are you getting your flanges from? or are you making your own? exhaust flanges are a dime a dozen but intake is a different story. Do you have any shots down the throat of that thing str8e180? And yes...you're right. Those injectors are definitely as close as possible.

Welds look awesome on the BMC you have Ashton. No reason to keep them on the inside though, I would have rather seen them filed down smooth for flow.

and here's my intake side of the head for good reference...

Those injectors be squirting all over that head. That manifold looks sex