carlos_hiraoka

if the fuel pressure is increased to a 4 bar differential (that is 4 bar @ sea level) with a 1:1 fuel pressure reg on the 440's injectors, do they become equivalent to 500's ?????

Carlos H.

john banks

440((4/3)^0.5)=508

carlos_hiraoka

thanx for the reply

so let's round it to 505cc ..... and this should be good for how much ?????

Carlos H.

john banks

505*4/5.5*0.85=312 BHP

Based on BSFC of 5.5 cc/BHP and 85% IDC.

These appear to be conservative values, so either our dynos are giving b***sh** figures or the BSFC is lower than that

As a rough indication, a decat P1 with VF28 running 1.2 bar at 6000 RPM is reaching 92% IDC approx on 440s at standard fuel pressure running 870mV narrowband lambda voltages from my experience (although this is on a standard fuel pump which may well be dropping pressure at this demand). Dynos would probably average out at 325 BHP for this sort of setup IMHO.

My estimates only... as always pinch of salt. Hope it's useful.

carlos_hiraoka

OK but 85% ..... ..... let get real:

505*4/5.5*0.95=349 BHP

Carlos H.

john banks

They are probably not linear after 85% anyway, so if they go static at say 90% you are going to get full flow out of them then. But you might have a step change in AFR, but I've never seen it on wideband... usually too busy grabbing the next gear when running fully open injectors. Some people are getting more relaxed about running them wide open, but there is a risk of them failing mid open position.

carlos_hiraoka

never felt this step change.

Carlos H.

john banks

Me neither, but I wonder if the lambda sensor is quick enough to see it? The fuel should cool down the coils enough - I know Andy F held one wide open for 15 minutes on the bench and it was fine.

Anyway, what's a guy like you doing messing about with tiny injectors?

carlos_hiraoka

finding the limits of them on another one's car

carlos_hiraoka

I was after 650's or 740's ..... but ended up with 850's since there were none of the common ones available, and the price was the same. Got enough fuel now, but idle is on the high side

Bob Rawle

Temp rise in a high impedance injector is pretty low and not going to cause an issue for the length of time that they are likely to be open, used to run mine at an "effective" 126% before I changed to 740's (std engine). You can run them to the mid 90's no problem but fueling control is not quite as good.
edirted to add watch the fuel pump, if you increase the pressure the pump will deliver less flow so you could be losing not gaining, use an uprated pump to be sure.

bob

[Edited by Bob Rawle - 5/28/2003 10:29:22 PM]

carlos_hiraoka

hope that the Walbro is good enough ..... thanx Bob for your reply and in case you didn't read the 22b thread, a big THANK YOU once more for helping me out on the MOTEC sync/ref issue, no more problems (clean 8000 rpm ) now that the sensor 0 volts have been correctly connected and with the crank and cam sensor spaced using a lmm washer.

Carlos H.