Effects of angled injectors

[Pete W]

Hi all, I was wandering whether anyone could help me decide whether there was any real performance advantage between having straight runners with angled injectors or angled runners with injectors firing straight into the cylinders for an engine air intake. After looking on the web all I have found are papers produced by patent offices, which you have to pay for. I would be greatly appreciative for any help what so ever. If you can't then can anyone offer any advice as to where I could direct my search http://fsae.com/groupee_common/emoticons/icon_smile.gif .

Thanks,

Pete

[Drew Price]

Any oppinion I have one way or another depends almost entirely on the specific intake port geometry and specific injector pintle you are considering, not all were created equal. OEM's (and well funded racing operations I imagine) usually play a role in the design of the injectors themselves in addition to their orientation in the intake system (which they also design) and to the intake port (which they also design).

Some intake port throats are angled more than others, sometimes you can see the top of the intake valve, sometimes not. Some injectors spray asymmetrically or spray differently depending on orientation (rotation). Pintle projection into the airstream likely plays a rols as well.

The way I understand it: There is definitely a performance (and economy) effect dependent on injector orientation / placement / angle, and it has a lot to do with atomization. The effects should become less as RPM's increase as flow becomes more chaotic, but that is a study into and of itself that you will have to decide on.

Many teams investigate at least some of these effects, but there are also many who do not and spend more time on the rest of the intake system geometry where there are arguably much greater gains (and losses) to be had.

I await for a few of the outspoken engine guys to chime in as well.

Best,
Drew

[jrickert]

We have never conducted a proper study on injectors but i will say a few words. Closer fuel injectors will give better transient response. There will be less manifold area that becomes wetted/unwetted. Further up injectors will give the fuel more time to vaporize especially at high RPM. In the stock GSXR setup the injectors are right above where the runners split. They have two spray patters that seem to be aimed at the valves. You can find fuel injectors with almost every spray pattern imaginable.

[Jayneel]

so i guess all we should do is keep the injectors close to the valves and such that they inject directly on them ?

[jrickert]

Motorcycle fuel injection handbook has some pretty good info on injector placement. Injectors further away from valves=better atomization. Injectors closer to valves=better transients.