What should my base fuel pressure be with afpr?

[Sk8er07999]

I just got my aeromotive afpr from slow boy and would like to know what you guys would suggest for a base fuel pressure. With or without vacuum line connected? Here are my mods: Apexi N1 Cat back and downpipe. Greddy Type-S BOV. punishment racing O2 housing, dejon race fmic, walbro 255, pte 780cc injectors, aeromotive afpr, exedy ceramatalic clutch, act flywheel, apexi safc 2, greddy profec b spec 2, dejon 3 inch intake w/ 3 inch k&n, 3 inch gm mas with maft.

Also, would you guys suggest different fuel pressures if I was running the stock 450's as compared to the 780's. Right now I put the 450s back in because I couldn't get the car to run right with the 780s. I have a race on sunday and was hoping to get the car tuned with a friends pocket logger using the 780s for sunday. Thanks for the help guys. Kevin.

 

[Ronin17]

Search could have given you the answer.

http://www.dsmtuners.com/forums/showthread.php?t=76962&highlight=1g*+fuel+pressure

That took me all of 30 seconds to find. Also I am not trying to be an ass, just some advice on future questions. Searching can answer about 90% of your questions.

 

[Kevin Jewer]

You should really make an effort to set up the AFR for what the ECU expects. 1g ecu, ~38 psi, 2g 43 psi. Adding pressure to make up for small injectors is a piss poor solution, and at high boost becomes a problem since pump flow goes down with pressure.

Those values given are base pressure, that means hose off. Hose on, take your idle vacuum in inches Hg, divide by two, and subtract from base pressure. Example, a 2 with 15" of idle vac should be at ~35-36 psi with the hose on. If it doesnt drop that low with the aeromotive, time to upgrade the return line. Very common requirement on 2Gs. I used 3/8th brake line (1 5 foot section from napa) and 3/8" ID fuel line for my application.

 

[Sk8er07999]

do I bypass the stock fuel pressure regulating solenoid? Is this going make it easier to tune?

 

[Kevin Jewer]

That wont affect tuning at all. In fact, it doesnt really affect anything at all (its there to raise fuel pressure on hot starts by preventing manifold vacuum from reaching the reference port on the fuel pressure regulator). Many poeple get rid of it just to clean things up.

 

[Sk8er07999]

I also ordered that stainless steel fuel line kit from slowboy and I can't get the stupid fittings over the hose! It's driving me crazy. I want to do this install tomorrow

 

[sp00ln]

You should really make an effort to set up the AFR for what the ECU expects. 1g ecu, ~38 psi, 2g 43 psi. Adding pressure to make up for small injectors is a piss poor solution, and at high boost becomes a problem since pump flow goes down with pressure.

What if you have 660cc and dont want to lean your AFC settings out too much?

 

[lowridin2g]

i have my afpr set at 44-45 base fuel pressure with the vac line on it kinda bounces between the two........goddamn big cams and lumpy idle

 

[Sk8er07999]

well I went to the track yesterday with the fuel pressure set at 45 psi with vac line disconnected. I had the 450's in running 16-17 psi of boost on the 14b with 93 octane and ran a 14.3 with a 1.9 60 ft, then a 14.6 with a 2.0, Now I wasn't getting enough fuel. with the all the setting on the afc and the gm maft I was hitting fuel cut really hard. but if I went negative in the correction I was getting a little knock. most I saw was up to 7 counts on mmcd. So I switched out the injectors with the 780's. Did a half as tune and ran a 13.9 with the worst launch of the day. 2.1. was going 101 mph through the traps. not bad but I was knocking like crazy even though my o2's read .850-.930. Could this be rich knock because the car was ####ing flying and running way faster and better then with the 450s.

 

[Revolution]

This thread might help ppl out.

Some intersting tid bits of info, that you should look at for shure.



http://www.ca.dsm.org/ubb/ultimatebb.php?ubb=get_topic;f=16;t=000820