Fuel pressure vs. pulse width

[kjones6039]

Well, here I am going back to B&G 2.98 again..... Just don't need all the functions in the Extra Code.

The info on my setup is pretty well covered in my signature, except for the code of course.

After minimal tweaking (cranking PW, WUE, etc.) the engine starts very reliably (cold) and idles well (warm) at 900-1000 RPM. After warm-up with the fuel pressure at 21 psi the idle PW is only about 1.7 ms. I am nervous about the PW getting too low and approaching the injector open time. This question should be right down Lance's alley. I think he used one of these TB's in the past.

My question is:

If I lower the fuel pressure to, say 14 psi, will I be able to increase the PW in any appreciable way?

Thanks in advance as always!

Ken

[Bernard Fife]

Ken,

Pressure affects pulse widths as the inverse of the flow rate, and that is covered here: http://www.megamanual.com/v22manual/minj.htm#flow

So the increased pulse width at 14psi would be:

sqrt(21)/sqrt(14)*1.7 = 2.08 or about 2.1 milliseconds

Lance.

[Bernard Fife]

Whoops, I have that wrong - you need to subtract the opening time, make the adjustment, then add the opening time back in.

So if the opening time is 1.0, it should be:

sqrt(21)/sqrt(14)*0.7 + 1.0 = 1.86 or about 1.9 milliseconds, so not much improvement (unless your opening time is shorter than 1.0).

Lance.

[kjones6039]

Great help as always, Lance!

Thanks,

Ken