What size injectors?
Thread Starter
Staging Lane
Joined: Nov 2004
Posts: 66
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From: SoCal
What size injectors? I'm starting to build my new motor (based on an A&A forged short block).....target is 410-425 rwhp NA......and then keeping my NOS 5177 dry kit with the 125 shot.....for an end goal of 500+rwhp on nitrous. Would SVO 30# injectors do.....or do I need bigger ones? What fuel pump should I run?
Id do a tad bigger. The shot itself wouldn't require it, but you have alot of power already so a little bigger is what I would do. Get a Racetronix In Tank Fuel Pump kit too. You'll be set, and haulin ***.
Not disagreeing with the above posts just making a statement. I'm running a h/c package, all the bolt ons 400+ rwhp and a 125 dry shot on 28.8 lb injectors and a Walbro 255 lph intank fuel pump and have had no problems.
Thread Starter
Staging Lane
Joined: Nov 2004
Posts: 66
Likes: 0
From: SoCal
Originally Posted by nostyta
Not disagreeing with the above posts just making a statement. I'm running a h/c package, all the bolt ons 400+ rwhp and a 125 dry shot on 28.8 lb injectors and a Walbro 255 lph intank fuel pump and have had no problems.
Yet.
Thread Starter
Staging Lane
Joined: Nov 2004
Posts: 66
Likes: 0
From: SoCal
Originally Posted by Robert56
The math, 550hp x .5 / 6.4 = 40.62lb-hr min size injectors (to meet recomended 80% duty cycle)
Robert
Robert
Isn't your math a little off though.....for 550 x .5 / 6.4 I get 42.98.
Am I missing something?
And assuming I need 40-42's.....any recommendations? I was gonna get the SVO 30's (and aren't they equivalent to 36 on our fuels system?) stang store but now it appears they aren't big enough. I thought maybe 36's then, but all they show is besides 30's is 42's......and that would be overkill, right?
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My bad, it must be all the pot I smoked as a kid. My calc comes up with 42.97 rounded off. You can get 42lb'ers that are made for our pressure, rather than the SVO that use 45psi. Racetronics may have em.
Robert
Robert
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Originally Posted by nostyta
Not disagreeing with the above posts just making a statement. I'm running a h/c package, all the bolt ons 400+ rwhp and a 125 dry shot on 28.8 lb injectors and a Walbro 255 lph intank fuel pump and have had no problems.
Injectors for nitrous setups (dry) always seem to be able to support more in real life than thier calculations show. The math Robert did is a good starting point and will keep you safe. Also...dont forget the SVO 30, 36, and 42 lb injectors as well as most other injectors are rated at 42.5 psi. LS1s run 58 psi. So you must calculate the new injector rating based on the 58 psi.
I feel that either SVO/Accel injectors in either 36 lb or 42 lb green tops will work fine for you. You may squeeze buy with some 30s but if your going to purchase injectors you may as well get some that give you ample room. 42 lbd injectors and walbro 255 lph intank pump has gone 700 rwhp total many times all through the injectors. Its nice to ensure that injectors are not going to be a problem.
I agree with what Al said. Here is my take, the 80% duty cycle rec is based on a longevity/failure rate idea. For the occassional 1/4 run, going past 80% is not a problem. Would be if you were doing it all the time, it just shortens their life. Now I don't rec going static with injectors however, that can lead to problems for sure. I also like the room to grow idea, as us hot rodders are never satisfied. 
Robert
Robert