Fueling & Injection - Stock injectors Maxxed Out?

I just orderd Texas Speed's 228r. I will be installing ported 243's along with this cam. I already have all the supporting mods. I'm just wondering if my stock injectors will be maxxed out??? If so, i know where i can get 36LB injectors. Is that a good size?

I made 430whp on a dyno dynamics with 799s/TReX cam/fast92 6spd. I think you will be fine. Mine were the 28.6s though.

I have the same setup and I was at 100% duty cycle with my stock injectors.

im only making 405rwhp with T-rex and STOCK 853 heads, and i'm apparently peaked my duty cycle. Not to argue with oneoverwrx, but if you're going with that setup which you'll have to tune anyways, i say you might as well play it safe and spend a couple hundred more on injectors. 36s should be fine, SOME might even suggest 42s which will leave you room for future go fast mods :)

Absolutely. All cars are different. A little room with an injector is a good idea. Mine were at 96% duty at 6700rpms. I was ok with it as the car was not living up there. Most tuners won't take injectors up to those duty cycles but we did and had good success. Good luck with the build.

http://www.youtube.com/watch?v=fxJ3c0eJWa0&feature=youtube_gdata_player

either grab 37# or 42# injectors and you will be fine. Like everyone has said, the 42# will leave plenty of head room for more later.

also, FYI, the factory 190Lph pump maxes out at a 38LB injector (set of 8).
and a 255 Lph pump maxes out at a 51LB injector (set of 8).

SO, if you go beyond 38LB per hour injectors and you ACTUALLY require that much fuel, your fuel supply pressure will drop off.

Absolutely. All cars are different. A little room with an injector is a good idea. Mine were at 96% duty at 6700rpms. I was ok with it as the car was not living up there. Most tuners won't take injectors up to those duty cycles but we did and had good success. Good luck with the build.

http://www.youtube.com/watch?v=fxJ3c0eJWa0&feature=youtube_gdata_player

a little off topic... but that is a SICK ASS car! Kudos!!

either grab 37# or 42# injectors and you will be fine. Like everyone has said, the 42# will leave plenty of head room for more later.

also, FYI, the factory 190Lph pump maxes out at a 38LB injector (set of 8).
and a 255 Lph pump maxes out at a 51LB injector (set of 8).

SO, if you go beyond 38LB per hour injectors and you ACTUALLY require that much fuel, your fuel supply pressure will drop off.

That's actually really good to know, so when i stop being lazy and upgrade to 42s, i'll go ahead and upgrade the pump

I think I'm going to go with 36LB injectors for now. The main reason being i can get a brand new set of bosch 36LB injectors that were going to go in an LS1, but never did for cheap. Thanks for the help fellas.

It will be close. I have a bigger cam and ported 243 heads and my car barely maxed out the stock injectors at peak. It made 447rwhp. It would be worth it to swap them out just in case if you have the cash.

I managed to max out my 28# with cam and bolt ons.

Makes me wonder if there isn't some kinda of hidden issue...fuel pressure is great.

I managed to max out my 28# with cam and bolt ons.

Makes me wonder if there isn't some kinda of hidden issue...fuel pressure is great.

I don't think you read my post correctly, or understood it. A set of 8 , 38# injectors would yield a 190Lph pump at its maximum, beyond that you would have a drop in fuel pressure.

you maxing out your 28# injectors with a cam and bolt ons makes perfect sense. The injectors are maxed out, not the fuel pump. I have seen this many times, no strange issue. A cam and bolt ons can push a ls1/ls2/etc 30hp+ beyond stock and already the stock injectors are around 68~75% DC.

Get a set of FIC rejetted stockers. Good insurance.

So generally speaking the factory 28.8# injectors typically are done by 405-
415 rear wheel SAE and STD dynos will say 420-430 before pressure begins
to drop ?????

roughly yes.

My stocker's were running about 95% on my 02 Formula with a Cam headers and a Lid. While it was a healthy cam its not a TREX by any means. Also a dyno dynamics this was at 350hp through a 4L60E. I later put a FAST102 on the car and am using some 60lber's just cause I already had them on the shelf and now there is plenty of fuel haha. The 60's are only running around 45% duty haha.

All dyno's read differently but generally speaking on ours the stock 99-00 injectors physically stop adding fuel on a 6spd car right at 355rwhp. The 98 and 01-04 injectors will support a bit more at 380rwhp. But like I said all dyno's are different and you just have to go off of what your local tuner/dyno has experience with.

So I had my car dyno tuned and it made 390rwhp. The stock injectors are at 95% and i was told that this was fine unless i did anything else.

SAE standards anything above 80% duty cycle the injector doesn't have enough time to fully open and close and ends up staying technically staying open. I suggest upgrading, but that is up to you

What about a set of Ford 24lb injectors (EV6 connector) on a cam only 5.3? that flow rate is at 39.5lbs. I am not sure if the flow will be enough.

What about a set of Ford 24lb injectors (EV6 connector) on a cam only 5.3? that flow rate is at 39.5lbs. I am not sure if the flow will be enough.

so they are rated 24 # at 39.15psi ? ( ?? 2.69 bar ?? )
So how do you get 39.5 # at 58psi?

sqrt ( 58 psi / 39.15 psi ) * 24 #rating at 39.15psi = 29.2 # injector

sqrt is 1.217 * 24 = 29.2 #



similarly sqrt of 58/43.5psi is 1.1547 * 24 LB = 27.7 #


Those aren't really any bigger than ls1 stock injectors.... on a CAM only 5.3L those would work, but I wouldn't invest my money in them, I would go with something bigger such as a 32# or 36# and be done, even if you added heads or some other mod.