Upper/Lower injectors

Hi all

Has anybody got a feel for the sorts of improvements you can get using upper (mounted outside of the throttle valve) and lower injectors?

I have only done one engine like this so far and got about 10BHP plus better idling, but this was on a full race 9500RPM 1.7L 4A-GE and might not have been a typical example.

Thanks in advance.

I've got this setup on a 3SGE engine.

440cc inboards and 1000cc outboards.

I dont start switching across to the outer ones until after 5000rpm as there's a major reversion harmonic at about 4500rpm.

Also I've found that its best to have my injector timing transition across at higher rpm.

At lower RPM my injector timing is best spraying well before the valves open. Then as it phases across to outer injectors, its injecting during the induction event (hence 1000cc injectors, to get a short pulsewidth)

Mine is a mostly standard engine but it revs out nicely to about 8200rpm or there abouts before the power falls off a bit.

Not sure if that's more to do with valvetrian float or whatever than anything else!

I havent had this car on the dyno yet though but it'll be interesting to see how it goes when I do.

But yeah since I've got standard sized injectors in the head, idle and everything else is great because the outer injectors arent doing anything when they're not needed.

Sorry havent answered your question at all, haha. But someone in Aussie who's tried same thing on a beams motor has reported somewhere in the region of 15-20hp gain from midrange onwards with a well setup staged injection on beams motor.

It's a lot of effort for not much gain, but thats the way of life with NA engines haha.

Thanks Davidv...some food for thought there.

Never thought about using the upper injectors for something other than just distance from valve....reducing pulse width, varying spray pattern and harmonics might also help my "track day" engine produce that bit extra without making it unreliable/unusable on the road...something I am VERY keen to avoid.

Yeah I'm all about the idea of a good "all rounder"

If I used 1000cc injectors only, with these particular injectors.

I'd need a good short pulsewidth adder table setup as they would be idling pretty close to the non linear portion of operation.

Where as 440cc are nice and linear down to well below normal idle operation.

There's a good webinar on injection timing, basically I have done back to back runs with different injection timing settings.

Then you look for whatever injection timing makes your engine run richest with no other changes.

The only downside is that I had to spend $$$ on the Xtreme version of the G4+ in order to get 8 injector drivers. But I wanted lots of inputs and outputs to tinker with anyway.

When testing the injector timing, a fairly clear pattern emerged:

I ignored the 8025rpm reading and kept all of the high rpm injector timing at end of spray 250deg BTDC