So I'm looking to convert to an MPFI setup. I've specifically been looking at the FAST XFI 2.0 system as well as the Holley HP EFI system.

In the carb world, we always talk about ensuring your intake manifold matches your head/cam combo (i.e. Edelbrock Performer intake vs. Edelbrock Victor intake). For my setup, the max RPM I will reach is about 6200-6400 RPM or so.

Why is it that none of these companies offer different sized manifolds for different applications? It seems like they are all single plane manifolds that are geared more towards higher RPM applications.

I'm assuming manifold selection for EFI is equally important as compared to a carb setup.

Any thoughts?

Thanks.

 

Yes manifold design can be equally important but one thing efi has is fuel injection by pressure and computer timed injections, while a carb relies on a vacuum signal for fueling. Basically a constant metered fuel leak lol. Too big of manifold and too slow air velocity its hard to draw fuel thru the carb and keep it suspended in the airstream. Efi doesnt have that problem.

But the efi system can still be influenced by runner size, plenum volume, and runner length, just like any carb setup. There are books and computer programs that can help estimate ideal size for your rpm range.

It seems most single planes have runner lengths designed for 6000-7500 rpm power depending on engine cubes. They still can work well enough for other rpm ranges due to efi's fuel supply vs a carb. Other manifolds that fees from a common plenum like holley stealth ram, edelbrock pro flo xt, ram jet, etc usually have runner lengths ideal for peak power in the 5500-7000 range but can vary. Length alone may tune for an rpm range for a given engine size, but the amount of power will determine how big the runner area needs to be to pass the airflow required.

Without goin custom its hard to find a manifold to tune to your desired rpm range. You can find a manifold you like and measure its runner length and area and then build a motor around that. When length is right, the induction harmonic pressure waves that occur will be timed so that the waves arrive when the valve is still open, and thus "ram" the air charge into the cylinder. This is increased volumetric efficiency and makes more hp and trq than engines with manifolds out of tune.

Its like tpi intakes. Long length tunes for 4000-4500 rpm, and when you try to make more power higher in the rpm range it just doesnt happen. Now one reason is lack of area but length still has strong effects

 

Orr: has anyone modified a Weiand XCellerator single plane for EFI?

Seems it being low profile to allow hood fitment and on the smaller size on port size may be a decent choice?

 

http://xtremecarzone.com.au/index.php?showtopic=386

 

Someone probably has done it but i havent seen one. If its a smaller port and runner volume single plane it would likely fit the smaller cube motors well

Guys seem to really like the old strip dominator holley intakes, i believe 300-25 is the number. I would consider starting with that and porting as required for my build but its larger cubic inch and huge port. Out the box its still a good intake for smaller cubes. Makes good torque from recent tests i have read in magazines. Take that for what its worth but some good engine guys i talked to also have positive results with that intake. Edelbrock super vic 2 is also suppose to be good, but likely large for smaller motors, but in efi applications, i am not sure how much difference there is. Fuel isnt carried in the stream like a carb