running extra inlectors.

[utevanwgn]

Hi .
Straight to the point.
Can my delco ecm/pcm run extra injectors. Ie 2 or 4 extra just parralled in.
The reason I ask is because I have a bucket load of standard injectors and am too tight to just go out and buy bigger ones.
But I do have plenty of time and adding extra injectors to my 286 camed 304 seems worth trying.
Or am I wrong.
Cheers.

[turbo_will]

Might work ive done it on an ford ef ecu with the auxilleries activated under boost. Not sure how the drivers would handle it long term though. Maybe you could up the fuel pressure a bit if needed.

[antus]

which pcm? will need to be a non-sequential one. assuming 808, then it can run 8, beyond that you might get away with a couple, but it'll make everything harder and you wont be able to evenly distribute any extra fuel between all cylinders and because your cylinders arnt balanced wideband readings will be hard to interpret. not recommended.

[utevanwgn]

OK , yes 808 and or 838 or 424.
Fuel distribution ? even if I use an injector plate mounted just behind the throtellbody possably infront . Or are the std manifolds that bad.
I don't mind fabricating stuff. I have plenty to play with ,dead commies are piling up like old fridges at the local tip.
Cheers.

[antus]

The problem is that its multiport injection, it fires all injectors together, and the fuel should sit in the runners behind the valves then get pulled in to each cylinder 1 by one as the valves open. If you put them in the throttle body the first cylinder will get all the fuel and the rest none (more or less). When you run throttlebody injection the injectors fire for every cylinder to obtain even distribution. But your not going to be running in that mode. If you try it, its going to become a giant pain in the butt to get right as you just wont be doing it right. I dont think anyone here will be able to tell you everything you'll need to tweak to get it close to right. If you dont understand this and tune based on wideband you'll have some over rich cylinders, and most lean as the exhaust will mix before the sensor and you'll have no viability what is happening except it wont be running well.

[Holden202T]

I have to agree, I'd either be increasing the fuel rail pressure or just get bigger injectors.

[utevanwgn]

So if I understand correctly . Mounting one injector up stream will not pulse fast enough to fully saturate the air stream thus causing lean / rich conditions.
Thank you ANTUS for your insite.
I don't know why I keep trying to reinvent the wheel.
Q what frequency do the injectors run at (or do they fire as per engine rpm)
Im only asking as I don't know exactly how the fuel metering is achieved).
Cheers

[VL400]

They fire once per engine rev on a standard tune. The memcal tells the ECU how many pulses per rev to expect from the dizzy/crank pickup - so on a V8 it will have 4 pulses from the dizzy each engine rev, on each 4th pulse (or every 4 cyls) the injectors get fired.


So from that this from the post by antus should make more sense and answer your question on if the injectors do not operate fast enough...

If you put them in the throttle body the first cylinder will get all the fuel and the rest none (more or less). When you run throttlebody injection the injectors fire for every cylinder to obtain even distribution.

Will get lots of fuel in some cyl and not much in others.

[utevanwgn]

Cool , I now understand, .
It looks like Il be using a set of 42 lb injectors I was saving for my turbo 253 sandman project.
No moor waisting time trying to be creative.
Thanks for all the help.
Cheers NATH

[VL400]

Its certainly not wasting time being creative and putting ideas out there, there is more than one way to do things and a bit of discussion can often bring out some good ideas.

In this case its just the way the factory ecu works that means mixing a port injection and throttle body injection setup won't work well.

A set of 42lb injectors will work much better, lots of headroom for more mods too