Results 1 to 9 of 9

Thread: 255lph intank fuel pump and T-REX (190lph) external fuel pump combo question!

  1. #1
    Senior SCH Member
    Join Date
    Dec 2002
    Posts
    102

    255lph intank fuel pump and T-REX (190lph) external fuel pump combo question!

    Okay... I have heard mixed reviews about running a 255lph intank fuel and the vortech T-Rex (190LPH) together...

    Some people say it is a solid combination, whereas the external fuel pump keeps the fuel pressure constant incase the internal fuel pump becomes incapacitated at anytime plus other added benefits of running the two pump in conjunction with each other...

    Whereas some people say the obvious... For example if you were to have a 255 lph intank fuel pump and a 190LPH T-REX external fuel pump, the T-REX would be restrictive and lessen the flow rate of a 255 lph intank fuel pump since the external T-REX pump flows mathematically "65 LPH" less than the 255 lph intank fuel pump.


    That is the general feedback I have been getting from many people when I ask for their opinion on that particular subject


    SO...


    What it boils down to is...

    Some say it works! Some say it won't work!


    Okay VortechPower.com peeps, chime in with your input.

    Will the external T-REX pump restrict a 255lph intank pump? Will Batman ever let Robin cruise the Batmobile? Will we all get free vortech superchargers if we promise to put vortech stickers all over our stangs?


    -Chris
    -Chris

    1991 Ford Mustang LX Sport 5.0
    Goliath
    (Novi 1000/Nitrous Works Powered)
    R.I.P. its been fun friend!


    1993 Ford Mustang SVT Cobra #4549
    No Name Yet...
    (Vortech S-Trim Powered!)

  2. #2
    SCH Member
    Join Date
    Jan 2003
    Posts
    98
    1. I don't think that it will. I ran this combo on my car and it worked very well. I made 425hp with it and my a/f was good. I held fuel pressure steedy at any rpm.

    2. Robin will never get to drive tha Batmobile.

    3. If they would then I would.:p
    93 LX
    R331/AFR 205/Vic 5.0/? psi

  3. #3
    Junior SCH Member
    Join Date
    Jan 2003
    Posts
    36

    My guess: t-rex is the bottleneck

    I would have to see the pump curves for both pumps (if available)and calc the system hydraulic requirements to confirm thou.

    Under certain conditions, like using a high ratio fmu, an intank 255 lph may not have the capability to flow 255 lph at max conditions because now the pressure required of the pump is like 115 psi (pure guess, system loss = 35 psi + backpressure at the injectors = 80 psi = 115 psi required of the pump). Same applies to the 255 lph/t-rex combo which may not flow the 190 at the high backpressure the fmu exerts. I think the pumps are typically rated at 70 psi discharge, except for the GSS-340 high pressure which I think is rated 20 psi higher?

    Typically, with any given non-positive displacement pump system, pressure produced is inversely related to flowrate. Increase the pressure the pump is required to develop and capacity is reduced. Or conversely, increase the flowrate of the pump ( say the rated 255 goes to 300 lph) and it may be able to do that but at like 30 psi discharge pressure. There may be a crossover point in which increasing the backpressure would cause the 255 intank to flow less than the 255 intank/t-rex combo.

    Not sure if that answers your question or causes more confusion, but I'd need to do the system hydraulic calcs and check the pump characteristics of the specific pumps to give you a much better answer.
    '91 GT (Original Owner)
    SC-trim w/ bypass, TFS Street intake, 65 mm FMS TB, 7" crank pulley, Morpheus pipe, 30# FMS injectors, 255 GSS340 Walbro, 3.55's, 1 5/8 shorties, Magnaflow catback


  4. #4
    Junior SCH Member
    Join Date
    Jan 2003
    Posts
    33

    Re: 255lph intank fuel pump and T-REX (190lph) external fuel pump combo question!

    Originally posted by Goliath 5.0
    Will the external T-REX pump restrict a 255lph intank pump? Will Batman ever let Robin cruise the Batmobile? Will we all get free vortech superchargers if we promise to put vortech stickers all over our stangs?
    I honestly don't know. Thats the exact combo I run, and the few miles i have put on my car with them both, seemed fine. None of those miles were with boost.

    I don't think so!

    Maybe? I'll take a free sticker!
    **93 Calypso Green LX 5.0, 1 of 654**
    BBK Ceramic coated shorties, Stainless H-pipe, Flowmaster catback, underdrive pullies, and 3:55 gears!

    **89 LX 5.0**
    Vortech S-Trim with AFM Powerpipe, Pro-M with 36lb injectors, Kirban AFPR, FMS ceramic coated headers, Hedman Offroad H-Pipe, Flowmaster Catback, Steeda Tri-Ax Shifter, 3.73 gears, and a few gauges!

    **90 LX 2.3**
    88hp of one wheel spinning fury. The best 835.79 spent so far!

  5. #5
    Senior SCH Member Trey's Avatar
    Join Date
    Jan 2003
    Location
    Salida, Colorado
    Posts
    115
    Very interesting guys. I have a 255 intank right now and a T-Tex sitting on my work bench. What to do....What to do......:D
    1998 GT
    S-Trim
    DSS Forged Short Block
    PIs
    Murillo Tuned
    347hp 354ft/lb

  6. #6
    Senior SCH Member
    Join Date
    Jan 2003
    Posts
    110
    i have a 255 intank and a t-rex in my car and my air/fuel is dead consistant
    --
    93 GT

  7. #7
    Junior SCH Member
    Join Date
    Jan 2003
    Posts
    5
    FWIW, the LX out in the garage has a 255/T-REX combination. The 255 was added sometime after the original SC install.

    When the car fist came to me it had an adjustable FMU on it that was a used unit from someone somewhere and it never seemed to work right. Anyway with a FP guage on the car when boost was first built the FP would spike to over 90psi and then drop steadily to about 65psi@6000rpm. That tells me the fuel system is not completely capable of supplying the engine demand. How much of that drop is fuel pump related and how much is due to stock lines I don't know.

    I've removed the erratic FMU and run 36's where it had FMU/30's before. After I get some sort of Tuner/Tweecer I'll move to 42's or something and get some real fuel line in it too.
    Parker

    1990 LX w/S-trim
    1990 Cougar XR7 (3.8 SC)

  8. #8
    SCH Member
    Join Date
    Jan 2003
    Posts
    84
    I have heard that a 255 in tank will be plenty for 400 or so horsepower and you don't even need a T-rex. My car with an adjustable FMU and 36 pound injectors would always hold perfect fuel pressure under boost,with or without the T-Rex. I didn't ever dyno tune it though and now it is apart with the new motor on the way in. P.S I think I was running way on the rich side cause I cranked the FMU up so it would have like 70 lbs under boost. I might try it without a FMU next time. It is going straight to the dyno before I run it had. In conclusion, I don't think I will run the external fuel pump.
    93 LX Convertible, Saleen body kit & decals, Balanced 306, B303, 1.7rr, TRW Forged pistons, Explorer intake, GT40p heads,Head studs, 70mm T.B,

  9. #9
    Senior SCH Member
    Join Date
    Feb 2003
    Location
    Houston
    Posts
    189
    I've made over 500rwhp with a Walbro GSS340 intank and T-REX inline pump, with no problems.

    Troy
    1995 Mustang Cobra
    302-10.77 @ 127.76
    new motor being built
    redsnk@yahoo.com

    owner/moderator
    http://www.stangtuning.com

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •