Benefits of larger injectors

[zlexiss]

Tried a couple searches, didn't see this discussed yet - feel free to point me if I missed it.

What's the ideal injector size for a car?

If 2 injectors have the same spray pattern and the computer is programmed correctly for each size, will there be any performance or other noticable difference between the smaller one running at 80% duty and the larger one that runs at 50%?

I'm purposely picking numbers that say that the smaller one isn't being overworked, and I don't know if there's such thing as "too big" if the programming is right - bad idle or other effects?

Having read what I've written, maybe I'm really asking what the ideal range for injector duty cycle is over a car's powerband.

-Jeff

[Turbo V6 Camaro]

the only reson to add injectors is if your spraying or adding boost, or have a really big cam and are somehow maxing them out N/A.

the only advantage of having one injector at 50% and one at 80% would be you have room to upgrade, but at the same time your injectors are a bit big if thats all that you are using of them.

[Wicked 3800 V6]

Eh viper, i dunno. zl there must be some sort of "efficiency / accuracy at duty cycle" chart for an injector. Pick the cycle that gives the best spray pattern or whatever.

[Turbo V6 Camaro]

Originally posted by Wicked 3800 V6:
Eh viper, i dunno. zl there must be some sort of "efficiency / accuracy at duty cycle" chart for an injector. Pick the cycle that gives the best spray pattern or whatever.

umm that would be cool to see one i have never read anything that says you should keep the duty from % to % i know suppose to stay under 90% i have never seen a low barrier on them.... wonder if there is one anyone ever see one?

[Dominic]

Bigger injectors are controlled more coarsely than smaller ones. Basically you need something that can handle your maximum horsepower at 80% flowrate. If you put too large an injector, it'll idle very poorly even with computer control due to under or over fueling, and mixtures will be harder to control.

Standard injectors seem to be good to at least 400hp, so don't worry.

[Turbo V6 Camaro]

Originally posted by Dominic:
Bigger injectors are controlled more coarsely than smaller ones. Basically you need something that can handle your maximum horsepower at 80% flowrate. If you put too large an injector, it'll idle very poorly even with computer control due to under or over fueling, and mixtures will be harder to control.

Standard injectors seem to be good to at least 400hp, so don't worry.

57# cold car and 20* = my motor throws ses every time i cold start it lol

[AZ3.8Camaro]

Jeff,
The industry standard for injectors is to be able to be run continuously at 80% duty cycle. They operate more predictably at 80% than, say at 50%.
80% is the ideal peak duty cycle.

Larger injectors (running at lower duty cycle) will not benifit you at all (and can in fact hurt your idle) unless you are currently exceeding 80% duty cycle of your current injectors often.

Injectors also have a minumum cycle: not really a duty cycle, but a minimum pulse width that the computer can give, and the injector can handle.

Larger injectors will spray more fuel during this minumum time, and therefore, if too large, will spray to much fuel into the intake at idle, no matter how short of a pulse you provide.

Low impedence injectors have a shorter triggering time, and can provide a better idle than high impedence injectors, but you need to make a resistor box for them.

[ January 12, 2005, 01:36 PM: Message edited by: AZ3.8Camaro ]

[AZ3.8Camaro]

Also,
FYI - Stock 22lb/hr injectors.
Assuming 50PSI at the fuel rail, and a Brake Specific Fuel Consumption of .45-.50 (a little on the safe side), at 80% duty cycle, they are good for 225-250 HP.

The only way to get more power out of them would be to increase fuel pressure. I wouldn't go much past 65PSI at the rail consistantly, which gives us around 260-285 HP.

They aren't that big, and are actually sized quite well for our car.

[Wicked 3800 V6]

Ya Dom there's no way you could get 400hp out of stock injectors. You could, but you'd be waaaay beyond the 100% duty cycle, wouldn't you?

[Camaro2k]

how can i check what % duty cycles mine are running @...?

[Turbo V6 Camaro]

Originally posted by Camaro2k:
how can i check what % duty cycles mine are running @...?

autotap or HPT or DHP

[RGB]

some multimeters (from an automotive store) can do % duty cycle.

[Wicked 3800 V6]

I thought that the duty cycle bit was in our tech encylopedia?

[AllTheGoodNamesAreGone]

Yeah, its in there somewhere..

[AZ3.8Camaro]

It is under engine tech or something, I don't make a lot of sense of it though, without some way to moniter it.