I'm building an L92 headed LQ9 for my IROC, and the LS3 intake/rails/injector take-offs on Ebay are looking pretty appealing. What kind of horsepower levels can the stock LS3 injectors support? My goal for the engine is 450-ish RWHP.

 

The LS3 vette has ~430hp so I think you're good at 450hp with the LS3 injectors.

 

I thought I read that they use LS7 injectors somewhere. But just open the tune file and check injector flow stats.

 

im in the same boat as you. also interested to know.

 

my truck makes 458rwhp and 435rwtq . using a 230-242 size cam stock truck intake manifold . and bolt ons.... @ 6100 my injectors were at 91% and 6700 they were at 102% using a lenient 18% drive train loss even with 22'' wheel's my motor makes around 540hp and 513tq at the crank ..

so we can just say anything over 550 at the crank ur asking for trouble!






dunno if this helps but theres my 2 pennies

 

FWHP vs. RWHP. Big difference.

 

I have 440'ish on LS2 injectors and havent had a problem.

 

Bringing this back to the top in hopes of getting some realistic numbers. I see a lot of RWHP cam-only C6s, but my 403 LS3-headed stroker may be a bit above that number. What horsepower can stock LS3 injectors support?

 

My combo with ls3 injectors made 520rwhp through a stalled auto at 95% duty cycle and stock fuel pump .. Then made 550 rwhp with stock fuel pump but upgraded to zr1 injectors but still at 92% duty cycle it that helps...the 550 was with new exhaust and vacuum pump...

 

Sounds a little too close for comfort to me. I guess I can add injectors to my list.

 

FWIW..... SuperChevy (Nov2010) built a 440 LSx stroker w/ FAST 44lb injectors that put down 645- FWHP

 

Mine had no problems @ 505rwhp. ~72% duty cycle @ 58psi

 

Wow, that duty cycle is a lot lower than others I was seeing at around the same RWHP. Maybe there's hope for the stock injectors yet.

 

N/A motors use less fuel then FI motors. Remember the LS7 uses the same injectors as the LS3... there's room to grow.

 

I don't think you were looking at the best data a couple years ago when the LS3 was a much newer engine than it is now. Like DietCoke said, they have LS7 injectors on them, it's not like the days of the LS1 4th gen, when a 1999-2000 LS1 car was just about out of room in the fuel department once it had bolt ons.

 

My truck had an LQ9, CNC LS3 heads, small cam (219@ .050), and made 400-410rwhp with stock LS3/7 injectors at ~80% DC.

 

See, that's why I'm confused. SweetS10 had an 80% duty cycle at 400wrhp, and DietCoke had 500RWHP at a 72% duty cycle. What makes SweetS10's motor so much less efficient that it needs way, way more injector (comparatively)?

 

Maybe auto vs manual? Fuel pressure differences?

 

I just sent my stock Ls1 fuel injectors resized by stiegemeier porting ( yea I know they do a lot of ford stuff) but they also do a lot of Fuel injection services and they resized mine to 63lbs for my application. Not bad for 175 bucks. IMHO so if your having doubt I'd just resize instead of buying newer or bigger and used stuff.

 

Manual versus auto, different fuel pressure, different target AFR at full throttle, and if they're basing their target/tune on lambda of their pump gas like they should, alcohol content in the fuel...more alcohol means higher IDC...and possibly someone isn't calculating IDC correctly?...or at least doesn't have a PCM in their car that is outputting the correct and actual pulsewidth through the data stream in order to get it calculated.