Fuel injectors
Thread Starter
Racer
Joined: Jul 2007
Posts: 264
Likes: 0
From: Southern New Mexico
Fuel injectors
I tried a wikipedia search, but didn't find an easy answer. Just trying to understand the need for higher poundage injectors with supercharging--is it just to handle the increase in fuel pressure with the BAP? If my gauge states 61lbs of fuel pressure constantly, why wouldn't you use an injector rated for over 60lbs? Wouldn't the pressure go up under boost? Or is it always up with the new injectors? Just looking for some working knowledge.
Thanks ahead of time.
Thanks ahead of time.
Safety Car
Joined: Jan 2008
Posts: 4,711
Likes: 3
From: Middle of No where AK
The system demands more fuel under high hp and boosted applications. With out larger injectors you will starve you motor for fuel because a motor is basically an air pump. The higher the hp the more air it draws in so the more fuel you need for proper combustion. If your going with a super/turbo charger you will need a fuel boost pump as well as larger injectors to handle the high demand of fuel while under boost.
Melting Slicks
Joined: Mar 2008
Posts: 2,835
Likes: 5
From: Avon Park FLORIDA
St. Jude Donor '08-'09-'10
the more power you make the more fuel you need.
just like a carb and jetting for more power.
the fuel press in our cars is 58psi and the injectors open and close.
the ECM controls how long and how often they open.
just like a carb and jetting for more power.
the fuel press in our cars is 58psi and the injectors open and close.
the ECM controls how long and how often they open.
Drifting
Joined: Oct 2006
Posts: 1,569
Likes: 4
From: Phoenix AZ
St. Jude Donor '09-'10-'11
Fuel Injectors
Also, be mindful of the LS specific use of the injectors. LS3/LS7 Injectors are different than LS2 Injectors in that they provide a different spray pattern because of the spark plug position in the combustion chamber. 
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
You're not looking at it right. The injectors are rated in flow rate (pounds per hour). So 60# injectors flow 60 pounds per hour of fuel. Some injectors are rated in cc's of fuel per minute or gallons per hour which is more intuative. This is flow rate, totally different thant the 58 PSI of fuel pressure our fuel system puts out.
Injector flow rates are typically measured at 3 bar of fuel pressure, which is 43.5 PSI. We run 4 bar fuel pressure systems (58 PSI) so a 60# injector really flows like a 69# injector. The increased flow due to increased pressure is not linear. More info here: http://www.rceng.com/technical.aspx?...ZfFjqIFO6xDuai
These flow rates are also at 100% duty cycle. The rule of thumb is to stay under 80% duty cycle so as not to overheat the coil in the injector although this is debatable.
So the reason people get bigger injectors is because the stock ones only flow ~28#/hr and even at 100% duty cycle that is no where near enough to supply enough fuel for ~600 RWHP. You put bigger injectors in and they stay open for shorter durations when the extra fuel is not needed.
Injector flow rates are typically measured at 3 bar of fuel pressure, which is 43.5 PSI. We run 4 bar fuel pressure systems (58 PSI) so a 60# injector really flows like a 69# injector. The increased flow due to increased pressure is not linear. More info here: http://www.rceng.com/technical.aspx?...ZfFjqIFO6xDuai
These flow rates are also at 100% duty cycle. The rule of thumb is to stay under 80% duty cycle so as not to overheat the coil in the injector although this is debatable.
So the reason people get bigger injectors is because the stock ones only flow ~28#/hr and even at 100% duty cycle that is no where near enough to supply enough fuel for ~600 RWHP. You put bigger injectors in and they stay open for shorter durations when the extra fuel is not needed.
Last edited by 5 Liter Eater; Mar 8, 2010 at 11:46 AM.
Thread Starter
Racer
Joined: Jul 2007
Posts: 264
Likes: 0
From: Southern New Mexico
Finally an answer worth waiting for. And I pretty much understood it
THANK YOU!!!!!!
THANK YOU!!!!!!You're not looking at it right. The injectors are rated in flow rate (pounds per hour). So 60# injectors flow 60 pounds per hour of fuel. Some injectors are rated in cc's of fuel per minute or gallons per hour which is more intuative. This is flow rate, totally different thant the 58 PSI of fuel pressure our fuel system puts out.
Injector flow rates are typically measured at 3 bar of fuel pressure, which is 43.5 PSI. We run 4 bar fuel pressure systems (58 PSI) so a 60# injector really flows like a 69# injector. The increased flow due to increased pressure is not linear. More info here: http://www.rceng.com/technical.aspx?...ZfFjqIFO6xDuai
These flow rates are also at 100% duty cycle. The rule of thumb is to stay under 80% duty cycle so as not to overheat the coil in the injector although this is debatable.
So the reason people get bigger injectors is because the stock ones only flow ~28#/hr and even at 100% duty cycle that is no where near enough to supply enough fuel for ~600 RWHP. You put bigger injectors in and they stay open for shorter durations when the extra fuel is not needed.
Injector flow rates are typically measured at 3 bar of fuel pressure, which is 43.5 PSI. We run 4 bar fuel pressure systems (58 PSI) so a 60# injector really flows like a 69# injector. The increased flow due to increased pressure is not linear. More info here: http://www.rceng.com/technical.aspx?...ZfFjqIFO6xDuai
These flow rates are also at 100% duty cycle. The rule of thumb is to stay under 80% duty cycle so as not to overheat the coil in the injector although this is debatable.
So the reason people get bigger injectors is because the stock ones only flow ~28#/hr and even at 100% duty cycle that is no where near enough to supply enough fuel for ~600 RWHP. You put bigger injectors in and they stay open for shorter durations when the extra fuel is not needed.
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