New tank is in, and new pump has different pressure. I cannot remember how to set the variable regulator. I cannot remember if I should set it with reference vacuum line on or off. Pressure is too high now, as AF ratio is now too high. It was running about 42 psi at idle, and now is closer to 50.

Preignition is gone entirely! So maybe I should start over and just tune the cruise cells leaner, and leave pressure alone. There must be a million permutations and combinations for how to tune one of these things.

Sam

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Normally, it's set with either the line off, or the engine off.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

What is a recommended pressure with the reference line unhooked?

Sam

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MPFI injector flow numbers are usually rated at 43psi - I power the pump with engine off and adjust until I get that.

I did what you said Pierre, but then when I hooked up the reference vacuum line, the pressure dropped to 35 or so, and it did not want to idle well. I actually think it has been tuned with this lower pressure in the past, but I decided to try a higher pressure based on the idea that the injectors do not atomize well if under 43 psi. But you hear a lot of things, and you have to wonder who really knows, or is the authority. So how do we reconcile this all of this?? Why would we adjust the pressure to be 43 psi with vacuum off, knowing it was going to drop below that, if in fact, these injectors do not work well at lower pressures?

I went ahead and adjusted the pressure regulator to idle at 43 psi. It then goes up to around 50 psi when accelerating. Is there anything wrong with that? Is this hard on the injectors in some way? I know I will have to re-tune the base fuel map for the higher pressure readings.

For now, at least, it seems to run very nicely. But while I have not had time to check out the AF ratio at full warm-up temp while cruising around, as Lou and I did a month ago. If it is running rich, and if prior experience is any indicator, the economy will not be good until I get it dialed back down.

The most encouraging fact is that the few times I stepped on the gas in 1st and 2nd gears, it did not go into pre-ignition, and the fuel ratio was not that off-the-chart rich. It seems to me it did not go richer than 11.5:1 or so under WOT conditions in boost.


Sam

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If it was tuned for a higher pressure, I'd just leave it there. The only problem is that if you go too far with the pressure, the injectors won't open.

It's the pressure difference that counts for atomization, not the absolute pressure.

_________________
"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair