Which Injectors for a Performance LS

[ADiCarlo]

Hey All:

I'm starting to piece together my intake manifold for my motor. I have LS3 heads so I'm running the factory LS3 manifold.

When doing some research I found 3 options, factory LS3 injectors, the Fast series (which appear to be the same lbs as the factory ones), and a set of Siemens injectors that will work but are 85 lbs.

Has anyone maxed out there factory injectors on a NA motor or found limitations during tuning due to the factory set up.

I would think that the 85lbs injectors would be beneficial when running boost which I might down the line but would this be overkill on a factory set up.

Just trying to wrap my head around the needs of a performance LS.

[protour]

85lbs are a massive injector for what you are talking about...

80-85lb injector have not so **** hot idle characteristics due to you cannot close them long enough, their spray pattern sucks at idle as well. They will support 1300rwhp in an LS1 based boosted combo

60lb seimens I have made 700rwhp with them. Many others in the 8-900rwhp range.

35-40lb injectors sound like what you are looking for. Factory injector is fine.

[Solid LT1]

OEM LS3 injectors are 42LB/HR same for 505HP LS7. So I guess you plan on making 800+HP and having low speed/idle tuning challenges if you go with those 85 injectors.

[71RS/SS396]

You need to look at how the injector is rated, some are rated at 60 psi and some are rated at 42 psi. I would not buy 85's until you actually need them for your boosted application, they will idle terrible. 600 hp n/a is about as far as I would go with the stock LS3 injector.

Here's how you calculate proper injector size to get you at 80% duty cycle;

Expected max horsepower x 1.2 x .5 for n/a ( .65 for boost) divided by the number of cylinders.

Example for 800 n/a : 800 X 1.2 = 960 X .5 = 480/8 = 60 so you would need a 60 lb/hr injector for an 800 hp n/a engine.

[ADiCarlo]

Thanks everyone for the input. I'm probably going to go with 60lbs injectors as the motor makes 510 right now so i'm approaching the top of the range for the factory set up.

Anyone recommend a specific brand for LS3?

[71RS/SS396]

Thanks everyone for the input. I'm probably going to go with 60lbs injectors as the motor makes 510 right now so i'm approaching the top of the range for the factory set up.

Anyone recommend a specific brand for LS3?
You are fine with the stock 42 lb injectors at 510 hp. I'm running a 60 in my 760 hp engine. I can't stress enough how much trouble your going to have trying to tune with injectors that are way to large for the application. The injector is at it's worst at on and off, it will drool when it starts and stops, with an injector that is too large the on cycle ends up being very short and the off time being long.