Now I have been doing some configuring on the S15 injectors, which are listed at 480cc, but have been flow tested at 444cc by Andreas. Here's where things get tricky. I used the Injector sizing formula if you want to make 320bhp on turbo car:

Formula:

Horespower X B.S.F.C.
#injectors x duty cycle

320
x.60(BSFC turbo car)
192

4 injectors
x.80(duty cycle %)
3.2

192
3.2

60lb/hr x 10.5= 630cc injectors

So you would need 630cc injectors to handle 320bhp, which is only around 280whp, given a 15% drive train loss.


Next formula is for figuring flow rate of injectors after increasing fuel pressure from 3bar to 4bar.

New Pressure
Old Pressure
(Square Root) X Old Rate= New Rate

58.9
43.5
(1.3540)=1.1636 x 444cc= 516cc

So with all that in mind, 444cc injectors even at 4bar can't support 280whp. If that is the case, how did Dave Racer make 320whp, which is roughly 368bhp given 15% drivetrain loss? Or do I have something completely jacked up here? It is late, but I tripple checked my calculations.

I did assume that maybe they were 480cc injectors, but even then @ 4bar they are still only 558cc injectors.

You're only using 80% duty cycle in your formula. Though not recommended, many people do push the injectors to 100% duty cycle. Also, I would say that FWD losses are typically less than 15%. I'd GUESS more in the 10%-12% range.

You're only using 80% duty cycle in your formula. Though not recommended, many people do push the injectors to 100% duty cycle. Also, I would say that FWD losses are typically less than 15%. I'd GUESS more in the 10%-12% range.


Ok, I plugged in 90% duty cycle and 95% duty cycle. I also changed the drive train loss to 12%.

90% duty cycle means you would need 548cc injectors

95% duty cycle mean you would need 518cc injectors

That would be for 280whp, which equates to around 313bhp. So either way, those injectors are at the limits.

Have a look at this http://www.sr20forum.com/showthread.php?t=142897

Something is wrong in your calculations. I made 282whp on 370cc injectors at 4 bar. A/F varied about 12-12.5

Always remember that real world testing is *** more acurate than trying to calculate it. A calculation gives you a rough starting point and then you go on from there.

My figures come from tried and proven dyno runs. Not only from myself but from other on this forum and JWT.