Anyone know how to calculate this? I'm trying to determine what size injectors I need using the worksheet at the bottom of this site: http://www.rceng.com/technical.htm. I don't know if this matters, but I will be using a 190 lph Walbro fuel pump. Thanks in advance.

 

how much hp are you trying to make? how big of a engine?

 

Oh my bad...B18c motor, prob no more than 300ish in hp, and I just plan on boosting about 8-10 PSI

 

Anyone? I just need to know how to calculate the system fuel pressure @ the fuel rail. Is it a standard # or does it change depending on other factors?

 

340 BHP puts you in the realm of 300 wheel no problem,

 

So to make 300 whp you would need at least 677cc injectors? I'm a little confused. A lot of people on here say that 300whp could be done with 440 - 550cc injectors. Is there something that I'm missing?

 

search i have posted the math for this b4 but to help you an cause im bored here you go

injector size= (BSFC) ( crank HP ) / (duty cycle) ( # of injectors)
al the math is the same as above but ill show you step by step how to do it

size = ( .60 ) ( 360 ) / (.85) ( 4)

size= 216 / 3.4

size= 63.529 lbs/hr to convert to cc/min multiply by 10.50
size = 667cc/min

got it good now the people who are using 440's or 550's may be running higher than 43psi of fuel if you want to increase the flow of your 440's theres is a formula here it is

PRESS new = ( PRESS old ) ( Flow new / Flow old)^2

Press = ( 43psi ) ( 680/440 )^2
press = 103psi
your new fuel pressure to get 680cc/min out of 440cc/min injectors needs to be raised to 103psi for me that more than i would go so try getting 550's and raising the fuell pressure.
hope i helped or gave you something useful to go by

 

Almost all injectors under 880cc are the same price - so just get the largest one and have room to spare. The hondata, Neptune, AEM, crome, etc will all run a 880cc injector just fine and idle like a dream.

liam

 

Sweet. Thanks for the info guys.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liam821 &raquo;</TD></TR><TR><TD CLASS="quote">
Almost all injectors under 880cc are the same price - so just get the largest one and have room to spare. The hondata, Neptune, AEM, crome, etc will all run a 880cc injector just fine and idle like a dream.

liam</TD></TR></TABLE>
very good point...
I bought rc 440's and they work fine... but they're damn near maxed out and need an upgrade for the new setup

O and thanks to Tony for the calculations!
Those could def. be very helpful in this situation