60 lb injector swap on Radix 2004
05-09-2005, 12:41 PM
#41
TECH Veteran
alot of this issue got started by me. not directly what has been done to the H2 at hand, but going from some work i have been doing. we recenlty had an 04' and an 03' radix truck at the shop. to make the story short from some helpfull information from bigtex and what we found after was some help in the area. i was told a bunch of 42's are big enough more than a few times when changing a pulley on an 04' truck. well, they aren't on an 04'. the 03' with the same pulley on it would overfuel. if you ran a fuel pressure test on the 03' with the vacuum/boost line to it disconnected it would read less fuel pressure than when it was connected. oddly enough the 03' fpr would add fuel pressure when it was under boost. injectors are named by their flow rating, but it's just that, a rating. a 42lbhr injector under higher fuel pressure than it was rated for is larger than 42lbhr. this is why the 03' truck with the smaller pulley would fuel without issue and had room to spare. the 04' truck on the other hand ran roughly the same or less pressure (+/- 1psi) at wide open as the 03' with the fpr not recieving a boost signal. it's for this reason that the 42's are big enough on the 6.0L under standard 6psi and a stock tune, but aren't under high boost and a good tune. many with 04's have a custom tune and small pulley (although not many with a 6.0L), but have never been checked with a wideband. i've been waiting yet for someone to show me otherwise that this information is incorrect. i've gotten a ton of people telling me that they have no problems, all of them of course having 03' and older trucks. i'm more than interested in hearing from someone running any boosted application (one flowing enough cfm to max the maf) that is an 04' and newer truck running a stock type fuel system with 42lb'ers and having no problems.
for you guys running 03's and older, what is your fuel pressure if you have a gauge at peak boost?
for you guys running 03's and older, what is your fuel pressure if you have a gauge at peak boost?
05-09-2005, 12:53 PM
#42
i think zippy just nailed it.
the 42's are only 42's where there is a 59psi diference across them that is what the fuel presure regulator is for. it ups the fuel presure when there is boost in the intake and pulls fuel presure when there is a vacume in there keeping a 59psi diference at all times.
if you have an 03 and are seeing 6psi then you fuel presure will be up around 65psi. sounds to me like if you have an 04 your fuel presure may actualy go down a little to 57-58psi. the 42's will actualy flow less on the 04.
a boost a pump probably wouldn't do anything since it only speeds up the pump but the regulator at the tank keeps the presure down to 59psi.
the 42's are only 42's where there is a 59psi diference across them that is what the fuel presure regulator is for. it ups the fuel presure when there is boost in the intake and pulls fuel presure when there is a vacume in there keeping a 59psi diference at all times.
if you have an 03 and are seeing 6psi then you fuel presure will be up around 65psi. sounds to me like if you have an 04 your fuel presure may actualy go down a little to 57-58psi. the 42's will actualy flow less on the 04.
a boost a pump probably wouldn't do anything since it only speeds up the pump but the regulator at the tank keeps the presure down to 59psi.
05-09-2005, 04:45 PM
#43
Originally Posted by parish8
i think zippy just nailed it.
the 42's are only 42's where there is a 59psi diference across them that is what the fuel presure regulator is for. it ups the fuel presure when there is boost in the intake and pulls fuel presure when there is a vacume in there keeping a 59psi diference at all times.
if you have an 03 and are seeing 6psi then you fuel presure will be up around 65psi. sounds to me like if you have an 04 your fuel presure may actualy go down a little to 57-58psi. the 42's will actualy flow less on the 04.
a boost a pump probably wouldn't do anything since it only speeds up the pump but the regulator at the tank keeps the presure down to 59psi.
the 42's are only 42's where there is a 59psi diference across them that is what the fuel presure regulator is for. it ups the fuel presure when there is boost in the intake and pulls fuel presure when there is a vacume in there keeping a 59psi diference at all times.
if you have an 03 and are seeing 6psi then you fuel presure will be up around 65psi. sounds to me like if you have an 04 your fuel presure may actualy go down a little to 57-58psi. the 42's will actualy flow less on the 04.
a boost a pump probably wouldn't do anything since it only speeds up the pump but the regulator at the tank keeps the presure down to 59psi.
not sure if this is true either, I have 63psi at idle in my 05 6.0, not the regulated 59psi you speak of.....
Volume at Pressure... More Pressure less volume.