Injector Question for LS1

**jeremy_m70** · 09-19-2007, 06:05 PM

Does anyone know what lb ratio per HP for LS1. Also how much overkill on injector size can you have before hurting anything. I'm just tring to figure out when I have maxed my injectors capabilities and how larger I can go to prepare for future mods.

From what I have read, the formula: Injector size (ex 28lb) / ratio per hp (ex. 0.5) x number of injectors (ex 8) - 10% for idle time = Max HP injectors can handle. In this example 403.2 (crank HP??) will be all my injectors can handle if ratio is 0.5.

Or if someone was wanting to produce 600 hp, then (600 x 0.5)/ 8 then add 10% = 41.25 or 42 lb injectors.

**jeremy_m70** · 09-21-2007, 04:28 PM

Anyone??

**jrgswhitels1** · 09-22-2007, 06:56 AM

Normally, if your stock with some mods, you want to stay within that 10% window of increase. Going up 2 pounds would be sufficient: 30lbs. This will allow much easier tuning and wont upset most tunes. Going greater than this will allow the over-sampling of the injector!! You WILL run tooo rich to the point that you could run like crap, push the limits of your existing tune to the point where you start losing power just to compensate the extra fuel. On the other hand, your duty-cycle will drop which will not only give you more available hrsepower (approximating) but increase the injector life. How much larger can you go? Depends on you mods!! Disconcerable difference for bolt-ons,..... The need for power adders like blowers, heavy nitrous, turbo's are real incremental levels of work! They WILL require much larger injectors! So, what mods are you planning?

**Frost** · 09-22-2007, 06:54 PM

injector tuning is easy, just don't swap without tuning. Run some 42s if you don't think you will ever go FI or HUGE DRY hit.

**jeremy_m70** · 09-27-2007, 02:02 PM

Thanks everyone,

I think I found on LS1tech what I was looking for.....

0.45 N/A
0.55 Supercharger
0.65 Turbo

Lb of Fuel per HP factor's.

Right now I'm probably going to build the drive and suspension, send car to EPP for engine rebuild (car has 122k currently) then more than likely power adder, favoring supercharger over turbo for exhaust sound. I'm just was trying to put a list together for the budget for my goals. Based on my finding the factory injectors should be fine for typical bolt-ons, just wanted to by the proper injectors for down the road when needed.

**Doc99SS** · 10-11-2007, 05:13 PM

The constant that you are talking about is the BSFC,, this might stand for "Brake Specific Fuel Consumption or Constant" . Anyway I have from an engine book:
BSFC = 0.5 NA engines
BSFC = 0.6 power adders

The equation is: flywheel Hp = (inj flow rating) x (# of injectors) x (duty cycle) / BSFC

To calcualte the required injector flow rate for any wanted Hp is:
(inj flow rating) = [(desired Hp) x BSFC] / [(# of injectors) x (duty cycle)]

For duty cycle most people use 80% or 0.80 in the above equation.

Therefore, for a 600 Hp engine the required injector to maintain 80% duty cycle at WOT is: inj size = [600 x 0.5] / [8 x 0.8] ==== 46.875 so buy a 47 or 48#/hr injectors.