can someone with a custom MPFI setup let me know how they determined the angle and location of the injector bungs?
is it best to just aim directly down the port on the head
How far should they stick into the intake runners?

Also does anyone know what the internal diameter of those weld in holley injector bungs are?

Im in the early stages of a MPFI setup so i figured I would just stick to the holley design as close as possible.

has anyone done this on a tunnel ram intake? Im curious about streetability and idle of such a setup.

 

The aiming of the injector is just to get as much fuel as possible on the back of the intake valve. This helps to better vaporize it, and at low engine speeds can help some with emissions. It also allows for minimully less AE then poorly aimed injectors. but, for non emission applications, it's not a big deal in my book.

Big plenums take more AE, and can do better at evening out the cylinder filling. N/A engines can be touchy with what you do since there are such serious side effects to Helmhotz, or acoustic tuning. Some guys wind up with lousy idles, but good tuning can always min that. I've about doubled the plenum area on my car, and it still idles very well.

 

I agree with Grumpy. Its best to have it pointing at the valve. With some intakes its just not possible to do that though. The angle on mine points only slightly in the direction of the valve and works very well. The injector spray bounces off the bottom side of the intake runner, vaporises and gets carried down the runner when the intake valve opens.


You will have to copy and paste the links into your address bar to make them work.
http://www.fbody.com/members/workman/MultiPoint1.JPG
http://www.fbody.com/members/workman/MultiPoint2.JPG
http://www.fbody.com/members/workman/MultiPoint3.JPG

 

Here are some pics of my new manifold.

The injectors are almost vertical.
There have been those that didn't like the way engines idled with this manifold, but I didn't by it with idling in mind...

Once you get past 25% DC, on a street car, the injector location isn't really critical. ie not compared to a 12K RPM engine.

Small injectors spraying up by the intake valve will give best idle, and the expense of high HP numbers, and large ones at the very end of the runner will have a poorer idle, and better top end.

BEST answer is 2 injectors per cylinder pointed differently.

Or run a looser converter and get the engine up and into the RPM band quicker.

Autos have ALOT of advantages when it comes to EFI.

 

Another view.