How to determine injector size if unknown?

[n0dih]

I have a 99 K2500 454 Suburban and somewhere in its life, someone swapped in larger injectors. How much? No idea. I suspect to run moderate to high doses of E85, but I cannot be sure. It was a corp vehicle at one time, for around 80K miles of its life.

Is there anyway that I can calculate what they might be?

Stock is around 18-19 lbs/hr @ 43.5 psi (but GM forces 63 psi on them, they are really 22 lb/hr flow). I am tempted to put in my old good LT1 injectors (24 lb/[email protected] psi) simply because I know the flow rate. Or get a set of LS1 injectors and use them, again, for a known flow rate. I really don't want to be stuffing $$ into good injectors to replace good injectors if you know what I mean.

What I see on my datalog is it is ALWAYS 18.0% rich (both banks -18.0% LTFT, precisely 18.0%, almost NO variance at all). Always unless in decel or a couple rare times, it is pretty stable, but always 18% rich.

I can lean it out with a healthy does of E85, but that is only a tank by tank fix.

I don't have a tuning program yet, so I can't tune it myself, else I would just take slow steps to guess it out that way. My tuner is mail order and will fix when I tell him what I need.

Is it as simple as plugging in 18% fatter injectors into the injector flow constant? If running on pure gas, I get rich bank 1 and 2 DTC's, if running 10% ethanol, it helps slightly, but stays rich and sometimes trips DTC's. If I run 50-60% E85 and the rest gas, I get nearly dead on perfect LTFT. Sheesh, on cold start it blows black smoke out the tailpipe. And mpg sucks even for a 454.... And if you are wondering, everything else checks out fine, FPR, MAP sensor, Vapor Canister, new O2's, etc, and not a single one of those would lead to a perfect 18.0% rich condition, on both banks.

Thanks!

[redhardsupra]

option 1: take pictures and post them, someone should recognize them
option 2: send them for flow testing and cleaning

[WS6FirebirdTA00]

look at the part number

[n0dih]

Unfortunately they are a pain in the caboose to pull and look at, they are under the intake manifold:



Look where the oil filler neck is, from the viewing angle through that to the underside of the intake is the injectors. I can see part of one, but not enough to see well enough any digit of the part number. I tried to take some pictures of them once, but I couldn't even get it to focus on it.

They LOOK like my LT1 injectors, half grey, half black, fat body style. I'll see what I can get on it. It is just a major ordeal to pull the intake. If I do, I would just swap in my LT1 injectors and have the PCM tuned at once, I can't afford for the truck to be down.


I guess I could pull one, and send it off and put in another that I have that is the correct injector size (the old Cadillac 4.9L ones that were very prone to failure)....

No thoughts on how to calculate it from LTFT?

(anyone with creative ideas how to make a cold air box for this? I did this the other day playing around, compared to the stock air box with the worst bends in existance, this is a LOT better, runs better too....)