injector size for built 358?
Thread Starter
Burning Brakes
Joined: Nov 2003
Posts: 1,011
Likes: 1
From: Marietta Pa
St. Jude Donor '10-'11-'12-'13-'14
injector size for built 358?
AS you may know, I'm going the heads/cam/superram route, and was wondering what injectors I may need.
The heads flow 280cfm, the cam is a 222/230 duration with .55x lift. I have an AFPR and pink top Bosch injectors right now (22lbs).
If I plan on making peak power at around 5800RPMS, and shifting around 6k, but no higher, so I go with #26 or is what I have ok. I would really like to make sure before I put the superram on, as I don't want to have to take that off...ever.
The heads flow 280cfm, the cam is a 222/230 duration with .55x lift. I have an AFPR and pink top Bosch injectors right now (22lbs).
If I plan on making peak power at around 5800RPMS, and shifting around 6k, but no higher, so I go with #26 or is what I have ok. I would really like to make sure before I put the superram on, as I don't want to have to take that off...ever.
Thread Starter
Burning Brakes
Joined: Nov 2003
Posts: 1,011
Likes: 1
From: Marietta Pa
St. Jude Donor '10-'11-'12-'13-'14
Sounds good.
Thanks guys!
Edit: Does anyone know what the stock impedance and fuel pressure is on them? Also, can you use different impedance injectors than whats stock?
Thanks guys!
Edit: Does anyone know what the stock impedance and fuel pressure is on them? Also, can you use different impedance injectors than whats stock?
Last edited by 1990dtgL98; Mar 27, 2008 at 04:04 PM.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
BTW I vote for the 30 lb injectors and an AFPR.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
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What is a 358?
Thread Starter
Burning Brakes
Joined: Nov 2003
Posts: 1,011
Likes: 1
From: Marietta Pa
St. Jude Donor '10-'11-'12-'13-'14
It's a typo....357 (4.04 bore x 3.48 stroke).
Sheesh!
I'll probably wind up going 30's or 32's. No need to go larger, as the only other thing I could add is a supercharger, in which case I'd need bigger than what I should have now.
Sheesh!
I'll probably wind up going 30's or 32's. No need to go larger, as the only other thing I could add is a supercharger, in which case I'd need bigger than what I should have now.
Race Director
Joined: Jan 2008
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From: oregon
make sure to check what psi they are rated at also. the fords are at 39psi so running them at 45psi like i do = something like a 26 {guessing} i know with pressure going up, so does the fuel delivery capability. i've actually seen as much as 390rwhp 430ftlb on ford 24s, 30s offer a nice safety margin though. i think you could go either direction and be just fine. before you buy anything, talk to whoever is going to tune the car and ask their preference.
Safety Car
Joined: May 2006
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From: Salem NH
-- Joe
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
make sure to check what psi they are rated at also. the fords are at 39psi so running them at 45psi like i do = something like a 26 {guessing} i know with pressure going up, so does the fuel delivery capability. i've actually seen as much as 390rwhp 430ftlb on ford 24s, 30s offer a nice safety margin though. i think you could go either direction and be just fine. before you buy anything, talk to whoever is going to tune the car and ask their preference.
I can link you to the test charts we posted years back.
-- Joe
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
seriously? wow, i had no idea, i'm sure you've heard the 39psi more than one. do you know off hand about how many psi is needed for 1 lb gain in injector size? say 24lb@44psi, what would it take to hit 25lb, 26 etc
Safety Car
Joined: May 2006
Posts: 4,290
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From: Salem NH
http://www.rceng.com/technical.aspx
So, lets say you need a 26# injector, but you have 24# injectors. All injectors are rated at 43.5PSI, simply raising the pressure to 51 psi will
make a 24# injector deliver 26# of fuel per hour.
Be careful, because you can exceed the ability of the pump as pressure goes up. The pumps volume is rated at 43.5 psi as well, so as pressure at the rail goes up the pumps volume will go down. If the volume goes down beyond the flow requirements you'll run lean.
for example:
http://www.autoperformanceengineerin...l/fpspecs.html
This shows how the volume relates to the pressure. A stock GM fuel pump is about 160lph, or 42 gallons per hour. We know a gallon of gas is about 6 lbs, so roughly 252 lbs per hour.
So we know the stock fuel pump has the ability to drive 8 31# injectors
at 43.5psi to go static.
Now glancing at our chart, we see that by bumping up the fuel pressure
to 50 psi, we take a hit of about 10%. So now our volume capability is only 226 lbs per hour, or 28# per injector.
This is important, because once you get to 60psi you can only deliver 25# per injector, meaning you've exceeded the flow ability of the pump at that high a pressure, so you're no longer making up for smaller injectors. (since now your delivering less fuel at 60psi than you were at 50psi)
-- Joe