atmospheric pressure and AFPRs

[crimsondragon]

I've installed my brand new Fuelab in, set the pressure to 43.5psi, locked it down with the locknut and did my daily drive to NY. I leave my car in the Palisades where I'm guessing the altitude is maybe 1000ft higher than central NJ. I checked the base fuel pressure again and it dropped down to 42 psi. The locknut is tight still. The only thing I can think of is atmospheric pressure. Since it can range from 28.00hg to as high as 31.00hg, I believe the decrease is because of the higher altitude and changes in the atmosphere. What do you guys think? With that said, would it be best to wait to adjust it at an altitude close to sea level and on a day when the standard atmospheric pressure of 29.92hg is present? Or does it hardly matter?

 

[bastarddsm]

proably don't matter. The change in flow goes as sqrt(new psi/old psi) so going from 43.5 to 42 nets you a
net change of -2% meaning your injectors act like they are 2% smaller. shouldn't really matter. i would guess your old regulator did the same thing, you just never noticed it because you didn't have a gauge before.

if your tuned on the ragged edge of destruction it might be a problem, otherwise your good.

 

[crimsondragon]

My next concern however, is whether if the AFPR is faulty. I've come to learn from experience that just cause something is new, doesn't mean it isn't broken. I would also definitely like to do an experiment on this and monitor atmospheric pressure and how it affects the base pressure on AFPRs.

 

[Fast-Orange]

adjust it to meet your conditions, if you drive that route regularily adjust it half way and only have a +-1% fluctuation. but i really cant see it making a difference much, and thats your base fp, does it still reach the same fp peaks and average when crusing?

 

[Fast-Orange]

yes the atmosphere will affect it humidity will affect it, changes in density and so on

 

[bastarddsm]

actually hahahahahaa it dosn't matter at all.. i missed the ball. the regultor works to keep the pressure differential across the injector constant, whether in vacuum, or boost. so the guage only looks at one side of the picture.. i'll bet if you have a vacuum gauge it will show the same change in vacuum at cruize.

the gauge moving is correct operation. you need to set the bfp when the baro is exactly 1atm..

 

[Fast-Orange]

yup im guessing it peaks at 55-60psi under wot