Could someone comment on my calculations. This is from info I have collected from various sources including the TGO boards. I chose numbers that lean towards a worse case as far as psi requirements.

1. (425x.5)/(2x.85)=125

425=hp
.5 =BSFC
2 =# of injectors
.85 =duty cycle
125=injector size required @ 13psi


2. (125/80)x(125/80)x13=31.7 psi
(125/90)x(125/90)x13=25.1 psi

This is the desired inj.(125) divided by available inj.(80 or 90), squared and then multiplied by original psi to yield required psi for the available injector.

With 30psi being the often stated limit, 425hp requires the 90s. Working the number back for the 80s would limit them to 413hp and 464hp for the 90s.

 

I created this excel sheet a while ago, you may find it useful...

http://users.bigpond.net.au/ben_p/co...ctorsizing.xls

 

Good, the stuff I ran into is good info then.

Do you have a calculation that describes idle quality? I have seen on here that bumping up the injectors hp capabilty (size and pressure) has an adverse effect on low end fueling.

Also, any formula for injector longevity per increase in psi?

 

I run my 90 lb/hr injectors at 18psi, i suspect they will be at 20psi when i finish tuning. The PW at idle is short, but still controllable. There's a short discussion on that topic here: https://www.thirdgen.org/techbb2/sho...hreadid=290728

I can't comment on injector lifespan, but i haven't had a problem..

 

You probably will have an easier time controlling idle with a 383 as it natuarally can use the fuel. Imagine a smaller engine that needs your level of top end fuel trying to idle on your setup. Would you say it would be difficult or are you not that close the the limit with the 383? Going to 20 psi should make it worse too.

 

Ran my 90# injectors @ 20+ psi, couldn't get great performance though, put on a 750 cfm carb (jetted down) and it was like bolting on another 75hp.