Fuel injector sizing
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Tech Contributor
Joined: Sep 2005
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From: New Market AL
Fuel injector sizing
I did a quick scan on my '99 last night after installing the FAST intake to go along with my 226° cam, headers, Vararam... I noticed when I did a third gear pull (wasn't able to keep traction in 1st and 2nd 
) that my injector duty cycle topped out at 98%. Right now I still have the stock LS1 injectors (24# aren't they?). Would the stock Z06 injectors (28#) be sufficient, or should I step up to 30#?
) that my injector duty cycle topped out at 98%. Right now I still have the stock LS1 injectors (24# aren't they?). Would the stock Z06 injectors (28#) be sufficient, or should I step up to 30#?
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Joined: Jul 2006
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From: Simi Valley CA
I'm pretty sure your 99 used the 26# injectors as did my '00. It's not worth going to 28s. Just get a set of SVO 30s (or bigger depending on your future plans) and be done with it. You do have to program for the injectors.
Here's how to calculate for injectors... (from ls1tech)
Well here's the easiest way to tell if you ma get into trouble.
(Projected flywheel HP x .5) / 6.4 = min inj to meet 80% DC rule
So we first need to turn your projected hp into BHP. We just subtract 15% from your anticipated 385rwhp + 100rwhp shot = 485rwhp.
485 - 15% = 412.25bhp
412 x .5 = 206
206 / 6.4 = 32.18 injector to meet the 80% duty cycle rule. So, your 30's will be fine at these hp levels. Don't worry about going over 80% on a short 1/4 run, won't cause any issues, we just don't want static (100%).
I would still log a/f and kr on intial runs.
Here's a spreadsheet to use to calculate it and a spreadsheet to calibrate the tables for new injectors. And the answer to your next question is "no".. (there are no negative effects on running slightly larger injectors than needed)
Here's how to calculate for injectors... (from ls1tech)
Well here's the easiest way to tell if you ma get into trouble.
(Projected flywheel HP x .5) / 6.4 = min inj to meet 80% DC rule
So we first need to turn your projected hp into BHP. We just subtract 15% from your anticipated 385rwhp + 100rwhp shot = 485rwhp.
485 - 15% = 412.25bhp
412 x .5 = 206
206 / 6.4 = 32.18 injector to meet the 80% duty cycle rule. So, your 30's will be fine at these hp levels. Don't worry about going over 80% on a short 1/4 run, won't cause any issues, we just don't want static (100%).
I would still log a/f and kr on intial runs.
Here's a spreadsheet to use to calculate it and a spreadsheet to calibrate the tables for new injectors. And the answer to your next question is "no".. (there are no negative effects on running slightly larger injectors than needed)
Thread Starter
Tech Contributor
Joined: Sep 2005
Posts: 1,731
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From: New Market AL
Nicely documented answer plus attachments, with only a 24 minute response time. You could qualify as an emergency response technician! Thanks for the help. I will be looking for some 30# injectors.
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Joined: Sep 2003
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From: Cape Coral FL
One other thing I'd like to add is the SVO 30lb/hr injectors are rated at 3 bar ot 43psi. The fuel pressure in the C5 is 4 bar or 58psi, so they calculate to approx. 34.64 lb/hr.
This is a good source for injector flow info I've found:Injector work sheets
This is a good source for injector flow info I've found:Injector work sheets
