Fuel Injector Size Calculator & FUEL PUMP Chart

ZL1Killa · 03-21-2005, 09:25 PM

Yo!

Please note:
Most injectors will max out at 80% duty cycle and this is the accepted industry standard.

I did not make this up! This is from SAE - Society of Automotive Engineers.

The website article is http://www.rceng.com/technical.htm

and of course the website is http://www.rceng.com

Fuel Pump quick reference chart

onfire · 03-21-2005, 10:40 PM

RC is a respected company in FI. Now a sticky.

ZL1Killa · 03-22-2005, 01:06 PM

gracious, I know a lot of people will be using this; or asking about it

ZL1Killa · 03-23-2005, 08:02 PM

Also i wanted to add

Please let all know that this company can make any injector size. Custom injectors can really optimize performance and fuel economy and ENGINE LIFE.

TeeKay · 03-24-2005, 02:57 AM

rceng has the expertise! FWIW, I have found, that some engines don't fit the math. For instance the GN Buick 3800 OEM injectors go static at WOT. They are reputed to be designed that way. Now the math is really no bull, but some applications defy the math; I guess due to other factors. So I accept the formulas with a grain of salt. WOT is only one regime of engine operation, drivability and overall tuning is another. In 40 years of hot rodding I have found that nothing is absolute. I hope that adds something to the discussion.

ZL1Killa · 03-29-2008, 09:38 PM

Ok here is the formula to calculate your new injector rating based on the ACTUAL FUEL PRESSURE you have VERSUS what fuel pressure THE INJECTOR IS RATED AT

injector lb/hr RATING * (SQRT ( YOUR FUEL PRESSURE / RATED FUEL PRESSURE) )

For EXAMPLE:

an injector is rated 32 lb/hr @43.5psi

your fuel pressure is 60psi

To find out the new lb/hr flow rate the formula is:

32* (SQRT (60 / 43.5) ) = 37.58 lb / hr

onfire · 07-09-2008, 09:04 AM

Originally Posted by Lonnies Performance
I figured I would elaborate on your post.....

What you are saying is very good advice to those buying injectors. Just be clear that there is no problem with 60's in particular, but rather the use of injectors too large for the application.

Due to the efficiency of a stock LS1 engine, (this typically includes all with a stock cam) they do not require much fuel at idle & will typically be on the edge of idle control on this engine. A larger engine and/or bigger cam generally allow these injectors to work well. Sometimes a slightly higher idle speed is all that is required.

NOTE: This is still not an excuse to use an injector significantly larger than needed. Only buy the size that properly supports your power requirements. This is where the problem lies.

Convesely, a high boost application on a mild cammed stock cube LS1 motor can require these 60# injectors, but may still be on the edge of idle quality. This is rare, since most higher output motors are also built with bigger cams etc., but still none-the-less possible. Some additional adjustment can be had with adjusting (lowering) fuel pressure & obviously boost referencing to get the most out of the injector.

One thing I must say is stay away from the old Rochester/MSD style 50# injectors. These are potentially the worst injector to setup/tune on an LS1. Can they work.... YES, but plan on a lot of work as they are slow responding & highly voltage sensitive. For mail order tuning, forget it. They make 42's & 48's so use these instead of torturing yourself with 50's.