#19 injectors....why?
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Senior User
Joined: Nov 2005
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From: Lathrop, MO
#19 injectors....why?
I've seen several posts, here and other forums, were someone has "upgraded" from stock 14# injectors to 19# injectors. Then added an adjustable fuel pressure regulator to dial the delivered pressure down from 58-60 to 37-40. And nothing else appears to have been done.
My question is simply this...Why? The stock injector rating of 14#, as others have noted, is at a delivered pressure of 40psi. At the 60psi delivery they are actually operating at roughly 17# per hour. When using 19# injectors at 40psi your only getting a 2# per hour increase. Without any other changes to improve airflow the computer should detect a rich condition and reduce the injector duty cycle. This should effectively leave you with a 0 net gain for your efferts.
What am I missing in the picture?
My question is simply this...Why? The stock injector rating of 14#, as others have noted, is at a delivered pressure of 40psi. At the 60psi delivery they are actually operating at roughly 17# per hour. When using 19# injectors at 40psi your only getting a 2# per hour increase. Without any other changes to improve airflow the computer should detect a rich condition and reduce the injector duty cycle. This should effectively leave you with a 0 net gain for your efferts.
What am I missing in the picture?
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Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
From a pure power production stand point there is really no benefit. The only benefit is better throttle response. The stock injectors are maxed out very quickly once you start modding the engine.
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Senior User
Joined: Nov 2005
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From: Lathrop, MO
On an un-modified engine I wouldn't think that the differences would be noticable outside of a dyno. Including throttle response.
With a cleaned up head, exhaust and Intake coupled with a cam difinetly. With a modified set of maps/tables the computer can then use the high flow of the injectors.
With just the injectors stand alone isn't computer constantly having to back off the duty cycle to lean out the mixture to acceptable levels? In addition, isn't the injector vapor lock issue being reintroduced?
With a cleaned up head, exhaust and Intake coupled with a cam difinetly. With a modified set of maps/tables the computer can then use the high flow of the injectors.
With just the injectors stand alone isn't computer constantly having to back off the duty cycle to lean out the mixture to acceptable levels? In addition, isn't the injector vapor lock issue being reintroduced?
Postmaster
Joined: May 2002
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From: Broken Arrow, OK
I've had 19's on my truck for a few years and have never had any vapor lock issues, and the throttle response is noticably better with them. The computer does constantly reevaluate what's going on and make adjustments, but it guesses at the WOT settings based on what it sees at part throttle. It is programmed for 14 lb injectors running at 45 psi at idle and 60 psi WOT. When you substitute a 19 lb injector with a 5.0L regulator you set it to about 35 psi at idle with 45 psi WOT. The fuel flow at part with vacuum on the regulator is about the same as it was stock, so the PCM doesn't do too much adjusting. This is also when it makes its guess what to do at WOT. However, the 19lb injectors at 45 psi flow more fuel and the PCM isn't expecting that so it ends up richening the mixture.
