Injector size

What size injectors are people running?

Looking for some recommendations.

im running 850cc injectors. coarse thats on a turbo 4 cylinder

thats a pretty broad question your asking, injector sizing depends on a lot of things. what sort of power are you looking to make?

The injectors you buy might depend on what platform you're starting with. The cars and trucks generally use different injector bodies and seats, and different electrical connectors. I'm building an L33 that came as a full drop-out with harness and ECU, and didn't want to change the electrical connectors for my injectors, or use small, pre-wired adapters.

A bit of research seemed to indicate that the truck flex fuel injectors are about a 33 lb injector and my OE injectors were about 24 lbs. I have a set for my swap now, but everything is still in a huge pile of boxes on the floor, so no results yet.

Here's a good page to reference: [You must be registered and logged in to see this link.]

Injector size depends on supporting mods.......

Here's mine...
383 LT1
42lb injectors
edlebrock heads
edlebrock intake
edlebrock 58mm throttle body
CC306 cam
1.6 roller rockers
callie 4 bolt main caps
eagle forged crank
eagle forged rods
ross (9:1) forged pistons - I'm planning on going rear mount turbo in the future!
ECU tuned with tunercats.... This summer's gonna be fun!

Mine are the stock '99-'00 Camaro injectors, 26.2 lbs at 58 psi. Engine is an LS1 with LS6 intake and long tube headers, makes just shy of 400 hp.

Yup, I ran stock injectors on my '02 LS1 making 400rwhp. On my current 383 I'm running 50# injectors, making a class limited (and cam limited) 425rwhp.

Thanks gents, appreciate the input!

Going to stick with the 36lb injectors I am running. Tuner wants me to bump it up to 42lb injectors but I'm really happy with how the car is running.

Your tuner is probably looking at the injector duty cycle. If you're getting values over 80% you should go bigger. My injectors are 22 lb (measured at the usual standard 43.5 psi) but I don't know the duty cycle they reach in my engine. On the dyno my mixture looks good at peak power.

wanczykj wrote:Thanks gents, appreciate the input!

Going to stick with the 36lb injectors I am running.  Tuner wants me to bump it up to 42lb injectors but I'm really happy with how the car is running.

what sort of power are you putting down?

ill second that guess that your hitting more than 80% dc. if thats the case, if you should upgrade or not depends on a few factors. is the car just for the street, or is it a track car, and does it spend a lot of time at higher rpm?

the whole thought is above 80% duty cycle the injector will start getting hot, and at higher duty cycles fuel control isnt as accurate. on a street car its not as big a concern if your 85-90% duty cycle at peak power because you may hit that for a few seconds and then it drops again. however, in a track car it could be an issue. if your tearing down a long straight your at wide open throttle and near peak power for quite a long time, the high duty cycle can cause the injector to overheat, burn out the coil or stick the pintle.

myself, i have no problem with 90% duty cycle on the street. my cobalt ss from factory hit 97% duty cycle at peak power, dead stock. its quite common for them. if it caused damage gm would have had larger injectors from factory. flip side is the gm stage 1 upgrade kit consists of a large set of injectors and a reflash and you gain 25hp.

I'm not sure what kind of power I'm putting down as the car was not tuned using a dyno. The car is going lean towards the top end, but I am not tracking it so I'm completely happy with the results.

it going lean could be caused by 3 factors. first, could be the tune, although id rule that out being the tuner recognizes it and wants you to upgrade. second, could be the fuel pump, it may be too small of a pump and causing the lean condition. ive seen many times where people try to mask a fuel pump problem by putting bigger injectors in. its an easy to test, toss a fuel pressure gauge on the rail and stick it on the hood and go for a burn, see what it does. the 3rd thing, if the pump is good, then the injectors are maxed and need upgrading.

if the car is going lean thats a problem that needs to be addressed. my last post about injector duty cycle is only relevent for an engine that isnt going lean.

just playing around with an injector size calculator. 36lb injectors run at 58 psi should be good for almost 500 hp at the crank with 80% duty cycle.

id be interested to know a bit more about your setup. what engine, what engine mods, fuel rail setup, fuel regulator, fuel pump, those sorts of things. this has peaked my curiousity.

Bought the engine off a gentlemen that had it rebuilt and was going to put it into a 55 chevy.

Motor is a steel block 5.3 liter that has been bored out. Not sure to what dimension, has forged pistons, 843 heads that have been ported and polished, upgraded cam, an LS1 intake with a MTI racing 85mm throttle body. 36lb injectors, AFM fuel pump, Aeromotive fuel regulator set at 58psi, aftermarket fuel rails, kooks headers that y into a 3 inch resonator to a 3 inch muffler. PSI wiring harness, spec 1 clutch, hard mounts for the transmission, etc etc etc.

The car belonged to my father and was bought new in Germany in 1984. It's the euro version and has the smaller bumpers front and rear.

The body has just over 100k miles on it, and the car will rip the tires loose in 1st, 2nd, and 3rd gear without dropping the clutch.

I'm running a set of 235/35/19 in the front, and a set of 255/35/19 in the rear.

Wish I could figure out to post pictures. Have followed the instructions but just can't get them to post.

sounds like a decent setup.

it is plausible that your maxing the 36lb injectors. id still try and get a fuel pressure gauge to a place you can see it so you can make sure your not losing fuel pressure.

Have a fuel pressure gauge on the regulator. Not to sure if I'm loosing fuel pressure towards the top end and am happy with that set up.

The tuner is the one wanting me to go to a 42lb injector. I am happy where I'm at, not going to explore anything right now as its a street car and I have no plans on tracking it.

Not tracking it still doesn't solve the issue that its running lean. I wouldn't want to run lean period. Injectors are cheap a new motor isn't.

The car isn't running lean all the time, just at the top end when you are wide open throttle.

wanczykj wrote:The car isn't running lean all the time, just at the top end when you are wide open throttle.  

That may be where you discovered the lean condition but that isn’t accurate. Lean conditions aren’t sensitive to RPM or throttle position it’s sensitive to load. When a fuel system can’t keep up with an engine’s demand it goes lean. During lean conditions, combustion temperatures go stupid high and the pistons can literally melt to the cylinder walls. This happens to drag cars all the time in just a few seconds. A street car is just as likely to go lean in 5th gear on moderate grades at moderate speeds and low/moderate RPMs (high load).

I agree with Doc, a set of injectors isn’t worth betting your engine on.