AFPR question - bucking at full boost??

[12sec92Tsi]

Ok, I just got my Full Throttle AFPR put on last week and everything seemed fine - no leaks, adjusted fine - so I set my base fp to 40 psi with vac line off. Here are the relevant mods:

Walbro 255 pump
Full Throttle AFPR
450cc injectors
14b turbo
stock ic system
3" turboback
Magnecore 8.5mm wires, BPR7ES plugs
boost set at 18 psi

Ever since I put on my regulator and set it to 40 psi, the car studders and bucks like it's running on 2 cylinders or something whenever I hit full boost in any gear. Driving around it is fine, just when it hits 18 psi is when the problem occurs. Never had the problem before the AFPR was put on. What could this be - bad plugs, too much fp, fuel cut??? Ignition coils are less than 1 year old as are the plugs, but could they be fouled from running too rich? I get around 820 C at redline for egt. Thanks.

 

[oldman]

The base setting for a 1g is 36psi, not 40psi.

 

[billdo_83]

The base setting for a 1g is 36psi, not 40psi.

Actually its 37.5 for a 1g not 36.

Try turning it down to the 37 range and see if that fixes the problem. If it doesnt turn down your boost a coupla pounds becuase its sounds like you may be hitting fuel cut.

Fuel cut feels like you hit a brick wall and a big cloud of black smoke will come out of the back of your car.

 

[oldman]

Actually its 37.5 for a 1g not 36.

Actually it's 36.3 psi to be exact. http://www.vfaq.com/mods/FPR.html

 

[billdo_83]

I got this from the Vfaq too...

Fuel pressures given below are at curb idle. 1G numbers are as follows: the first number is stock; the second number is with the fuel pressure regulator vacuum hose disconnected and plugged. 2G numbers are with everything connected.

http://members.shaw.ca/costall/1000Q/answers-specifications.htm#Stockfuelpressure

 

[oldman]

I got this from the Vfaq too...

Fuel pressures given below are at curb idle. 1G numbers are as follows: the first number is stock; the second number is with the fuel pressure regulator vacuum hose disconnected and plugged. 2G numbers are with everything connected.

http://members.shaw.ca/costall/1000Q/answers-specifications.htm#Stockfuelpressure

I didn't see 37.5psi as you originally claimed. The chart stated 27psi without vacuum, with vacuum at 18Hg like it's suppose to be, it should put you at about 36 psi. The second number will vary depend on your vacuum but the base setting should be at about 36psi though I don't think 1psi will make that much of a difference.

 

[billdo_83]

No it wont really matter between 36 and 37 psi.

I've always just used 37ish as a base for all of my cars that I have tuned.

 

[12sec92Tsi]

Okay thanks alot guys, that really helps out. I put the pressure at 40 because I thought that would help get more out of the injectors, but maybe that only applys to larger than stock injectors. I'll try turning it down to around 36 or 37 and see what happens, and I'm also replacing my spark plugs tomorrow too because I've got to get throug emissions in 2 weeks or my car comes off the road - I've already had 8 months worth of extensions, so I have to pass this time, though the AFPR would help since my 255 pump overran the stocker. Thanks again.