Fuel injectors: injector angle in the runner

Don't know much about all the different injectors on the market.

But this question is about mounting them on the intake.

Do you want them to be vertical, or 90-deg to the runner, or ??

I see when people weld bungs onto manifolds the injectors always
seem to be vertical.
I'm guessing that the spray pattern/efficiency would be affected
by the angle.

Most are mounted vertical to make the fuel rail plumbing easy. Modern injectors work fine when the spray angle is at 45 degrees. It's better than 90 Degrees because you don't want to wet the runner wall on the other side.

Makes logical sense that you would want the fuel heading downstream as much as possible. So if 45* would be better than 90*. Would 30* be better than 45*?

Not necessarily. You want some turbulence to help with the atomization. An injector that has a narrow cone pattern would not be the correct choice for a low angle mount. Pro stockers played with injecting as far up the runner as possible to give more time for atomization and to help cool the charge and one that I know of tested the effect of injecting upstream.

I would imagine that a "big port" drag engine would want a long, wide pulse?

For what it's worth. I read an article a while back from a racer using port injection. He used 8 O2 and 8 EGT sensors. The mixtures between cylinders were all over the place. He worked moving the injectors and getting every cylinder equal. Said it actually slowed the car down a few hundredths.
Doug

Average guy should just put the injectors in a place where the plumbing and wiring is easy.

If you are building F1 engines, or NASCAR engines, or Pro Stock engines then you'll need to spend some time on the dyno and come to your own conclusions on where to put the injectors. I doubt anyone is going to tell you their secrets on that stuff.

There will be minor differences even with injectors at extreme placements/ angles. Even an optimized pattern/ angle/ distance is not going to be the best for the entire operating range of the engine.
If you favor great idle, get the injector as close to the intake valve as possible, and aim the injector angle at the intake valve head.
Idle will have the lowest air speed and air density. This means intake air will have much less effect on the shape of the injected fuel cone out of the injector. Sort of like adjusting for wind when target shooting, or peeing out of a car on the freeway😆
As density and air speed rise, injector angle gets less critical. The air will grab any fuel and move it where it wants to. The higher the rpm and density, the further from the intake valve the injector should be.
The best of both worlds is staged injection.

Full atomization (fuel vapor displaces air) is less damaging on a pro engine with huge air delivery. An engine with small ports needs to retain more droplets until the valve seat.

And we shouldn't overlook the effect of injector timing. This ability comes with sequential injection when you have both a Crank and Cam signal. At idle you want to inject well after the camshaft reversion pulse that pulses back into the intake runner. This primarily affects idle but it can be significant with a radical cam.

This is something I have yet to really dive into. Any pointers on what the data will look like when it is right?

I have heard of people doing this, even talked about it some in an EFI class I took but we didn't dive too deep into what it would look like when its right. My current combo has a lot of reversion and I am sure I could benefit from it. Currently I am using the default setting of 360* before the intake valve opening so I am sure its got some blowback.

It's best to start the injection pulse just after TDC when the piston is starting its intake stroke. The size of the injector is not a concern at idle because the pulse width is small and you have a lot of time. At higher RPMs the injection period will start to overlap the engines cycle but that doesn't matter at higher RPMs. The Holley system includes a way for computing the optimum injector end time based upon camshaft specifications. It's called Injector End Angle calculation.

Thanks rich, that sounds like a handy tool to have.