afpr psi

[geno414]

Hey so today i installed my afpr and my 255hp pump and i don't know what to set it at some one said around 40 ? and some one also said disconnect the vacuum to it two ? that's were im lost i have a 16g and a 2.3 stoker can some body help me out with the psi ??? and why the vac needs to be disconnected ??

 

[Bud92gsx]

Stock 2g fual pressure is 42-43 ish..

You need to add what your tuning with in your profile..

 

[geno414]

Stock 2g fual pressure is 42-43 ish..

You need to add what your tuning with in your profile..

Im tuning with safc and wide band but that's not hooked up yet its been raining here to much.

 

[kenamond]

If I remember correctly, stock 2g fuel pressure is 43.5psi.

 

[Calan]

If I remember correctly, stock 2g fuel pressure is 43.5psi.

That ^.

Your AFR's function is to raise (or lower) your fuel pressure at a 1-to-1 ratio with manifold pressure. If you are in vac, then it will lower pressure below the base pressure that it's set to. If you go into boost, it will raise fuel pressure above base pressure by the amount of boost you are seeing.

The reason you pull the vac line is so that you can set base fuel pressure without a vac or boost signal altering it.

Another method is to leave the vac line hooked up and manually turn on the fuel pump with the car not running, either with the test port in the harness or with ECMLink, etc. It's the same either way...you just want the AFPR to see neutral atmospheric pressure while adjusting the spring to set base fuel pressure.

 

[snowborder714]

2g fuel pressure is 42.6 psi with the vacuum line disconnected and plugged.

Craig, if you're talking about lowering on a 1:1 ratio, that is only when it comes out of boost. In relation to dropping and vacuum, your fuel pressure will drop 1 psi for every 2 inHg of vacuum. For example, if your idle vacuum is 20 inHg, your fuel pressure will drop 10 psi to 32.6 psi once you re-attach the vacuum line.

 

[Calan]

2g fuel pressure is 42.6 psi with the vacuum line disconnected and plugged.

42.6, 43, 43.5.... close enough for government work. Anything between 42 and 44 is well within the tolerance of most pressure gauges that an AFR will ever see.

Craig, if you're talking about lowering on a 1:1 ratio, that is only when it comes out of boost. In relation to dropping and vacuum, your fuel pressure will drop 1 psi for every 2 inHg of vacuum. For example, if your idle vacuum is 20 inHg, your fuel pressure will drop 10 psi to 32.6 psi once you re-attach the vacuum line.

I didn't want to make it more complicated than needed (and why I didn't say specifically how much it would drop during vac), but that is a valid point in the interest of accuracy. 1 in/hg at 60*F is roughly .49 psi, so yeah...you have to convert. It's still a 1-to-1 drop in pressure though; once you do the conversion to a common system of units (psi).

 

[TSiAWDRatlemstr]

Vacuum line unhooked, engine running, finger covering vacuum line - set it to 43psi and you're good to go! The injector flow rating from the manufacturer is done at 43psi.

 

[geno414]

thanks every one helped me out lot.