What Fuel Pump And Injectors Tfs Top End

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by 90lxwhite, Mar 8, 2014.

  1. I'm putting together an improvised trick flow top end kit(170's). What's the typical size injectors and fuel pump guys are running with this setup? It will be tuned. If I change injectors do I have to change maf or can that be worked out in the tune? This is a 95 gt by the way
  2. Ive seen guys go with 24's and should be enough. Get a MAF calibrated for the injectors you get.
  3. I think 24's personally are a waste of money. I'd get a set of 30's with a matching MAF. It will give you room to grow. For fuel pump size a 155 is fine for up to 400hp+. Contrary to popular belief, you don't buy the biggest fuel pump- 255 or 320- as it will push too much fuel and the fuel will actually heat up, and your stock fuel lines are not big enough.
    88LX5.Oh likes this.
  4. Fuel injector sizing & injector photos

    Revised 11-Dec-2011 to add larger injector sizes to injector table

    Injector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

    19/.5 = 38, 38 x 8 = 304 HP
    24/.5 = 48, 48 x 8 = 384 HP
    30/.5 = 60, 60 x 8 = 480 HP
    36/.5 = 72, 72 x 8 = 576 HP
    42/.5 = 84, 84 x 8 = 672 HP

    The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

    19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
    24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
    30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
    36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
    42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

    Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

    See http://users.erols.com/srweiss/#jcalc to get the calculators used in these examples.

    Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

    If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

    If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

    With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

    Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure

    Diagram courtesy of Tmoss & Stang&2birds

    Copied from the FORD RACING PERFORMANCE PARTS catalog:


    Fuel Pumps
    The following information is presented assuming the above information has been taken into consideration regarding BSFC, fuel pressure and specific gravity of the fuel being used. Most fuel pumps for electronic fuel injection are rated for flow at 12 volts @ 40 PSI. Most vehicle charging systems operate anywhere from 13.2v to 14.4v. The more voltage you feed a pump, the faster it spins which, obviously, will put out more fuel. Rating a fuel pump at 12 volts then, should offer a fairly conservative fuel flow rating allowing you to safely determine the pump’s ability to supply an adequate amount of fuel for a particular application.

    As previously mentioned, engines actually require a certain WEIGHT of fuel, NOT a certain VOLUME of fuel per horsepower. This can offer a bit of confusion since most fuel pumps are rated by volume, and not by weight. To determine the proper fuel pump required, a few mathematical conversions will need to be performed using the following information. There are 3.785 liters in 1 US Gallon. 1 gallon of gasoline (.72 specific gravity @ 65° F) weighs 6.009 LBS.

    To be certain that the fuel pump is not run to its very limit, which could potentially be dangerous to the engine, multiply the final output of the fuel pump by 0.9 to determine the capacity of the fuel pump at 90% output. This should offer plenty of ‘cushion’ as to the overall “horsepower capacity” of the fuel pump.

    To determine the overall capacity of a fuel pump rated in liters, use the additional following conversions:
    (Liters per Hour) / 3.785 = Gallons
    Multiply by 6.009 = LBS/HR
    Multiply by 0.9 = Capacity at 90%
    Divide by BSFC = Horsepower Capacity
    So for a 110 LPH fuel pump:
    110 / 3.785 = 29.06 Gallons
    29.06 x 6.009 = 174.62 LBS/HR
    174.62 x 0.9 = 157 LBS/HR @ 90% Capacity
    157 / 0.5 = 314 HP safe naturally aspirated “Horsepower Capacity”

    Safe “Horsepower Capacity” @ 40 PSI with 12 Volts
    60 Liter Pump = 95 LB/HR X .9 = 86 LB/HR, Safe for 170 naturally aspirated Horsepower
    88 Liter Pump = 140 LB/HR X .9 = 126 LB/HR, Safe for 250 naturally aspirated Horsepower
    110 Liter Pump = 175 LB/HR X .9 = 157 LB/HR, Safe for 315 naturally aspirated Horsepower
    155 Liter Pump = 246 LB/HR X .9 = 221 LB/HR, Safe for 440 naturally aspirated Horsepower
    190 Liter Pump = 302 LB/HR X .9 = 271 LB/HR, Safe for 540 naturally aspirated Horsepower
    255 Liter Pump = 405 LB/HR X .9 = 364 LB/HR, Safe for 700 naturally aspirated Horsepower

    Note: For forced induction engines, the above power levels will be reduced because as the pressure required by the pump increases, the flow decreases. In order to do proper fuel pump sizing, a fuel pump map is required, which shows flow rate versus delivery pressure.

    That is, a 255 liter per hour pump at 40 PSI may only supply 200 liters per hour at 58 PSI (40 PSI plus 18 lbs of boost). Additionally, if you use a fuel line that is not large enough, this can result in decreased fuel volume due to the pressure drop across the fuel feed line: 255 LPH at the pump may only result in 225 LPH at the fuel rail.

    My Comments:

    A lot of people oversize the fuel pump by buying a 255LPH pump thinking that the fuel pump regulator will just pass the excess gas back to the tank. It does, but… Did you ever consider that circulating the fuel around as a 255 LPH pump does will cause the gas to pickup engine heat? What happens to hot gasoline? It boils off or pressurizes the fuel tank! With most of the 5.0 Mustangs having the carbon canister removed or disabled, the car stinks like gas, and the gas mileage drops since the hot fuel evaporates away into the air.

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

    Ignition switch wiring

    Fuel, alternator, A/C and ignition wiring

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

    Vacuum diagram 89-93 Mustangs

    HVAC vacuum diagram

    TFI module differences & pinout

    Fuse box layout
  5. The 95 cobra had 24 lb injectors and doesn't it use the same maf as the gt of that year and the "tables" were corrected with tune? Couldn't I do that if I used 30 lb'ers? Or would I have to buy a maf? Also while i great tech sticky do I just guess how much power I will make and hope I guessed right when I purchase say 24 lb injectors? Fuel pump, so the gt fuel pump won't feed a motor w 24 lb and trick flow heads? Seems at the end of the day the vortech v3 kit might be the way to go, I think it'd come out cheaper since I'd be paying labor on heads and buying all the other necessary crap...
    #6 90lxwhite, Mar 9, 2014
    Last edited: Mar 9, 2014
  6. I think you need to stop worrying about the money and plan for whichever way you rather it be.
    The money is a wash, both ways are expensive, both ways are going to go over budget. If money is this much of a concern, honestly you shouldn't be doing it at all.

    I've yet to do any project that didn't go 50-100% over budget by the time i was done. Stuff happens when you take your car apart and you better be prepared when it does.
    tannerc91gt likes this.
  7. I invite any of the 255 (+) lph naysayers to provide objective evidence that it actually does produce a measurable negative effect, MPG or otherwise, over a smaller pump. I understand the logic, but I have a hard time believing it produces anything noticeable. I'be been running a 255 on stock lines for ~3 years now, and the car is no stinkier or worse on gas then it was on the stock pump.
    tannerc91gt likes this.
  8. Word.
  9. It's only $.... Was trying to stay around $3500 because that's what I have. If I did the v3 I could be up and running (w my "bandaid") What scares me about the topend is what happens if I get er all torn apart and I have to have pistons notched or some crap, there goes more money but then again what kind of fool worries about such things!? If all goes smoothly i believe I'm looking at $1000 for labor and tune. Also with the 95's there's the whole possible hood clearance issues. I dunno..
    Edit: ps: which way I want to be, whichever is less. 100 hp is 100 hp whichever way it comes. To those who say "forced induction are poweradders, not power substitutes, I say potato patatoe.
    #10 90lxwhite, Mar 9, 2014
    Last edited: Mar 9, 2014
  10. x infinity!!!

    Agreed. Don't see the big deal with running the big pump either. We run a return style fuel system. What isn't used, is sent back to the tank.

    I've heard fairytales about "super-heating fuel", but that seems to be nothing more than internet folklore. I have yet to see a single shred of proof to back these claims.

    I'd got the 255lph high pressure pump in my tank, feeding 30lb/hr injectors and it operates steadily and quietly while the car still knocks out 20-25mpg on the highway with ease.
  11. tannerc91gt likes this.
  12. Not in my budget.... I had to settle for 235#'s lmao (still saw 74% duty cycle with those o_O)
    A5literMan likes this.
  13. I'd be very cautious with anyone that is going to install a HCI setup and tune it for $1000.
    Sounds way below market value. Some guys get $750 alone for the chip and dyno tune alone.
  14. Why would Ford stick with a small pump when they could use a single lager pump and cover all the vehicles they make? Reducing the number of different SKUs reduces inventory and cost. The answer has to be that it has an effect on emissions and fuel mileage. Most of us here don't have a 4 year degree in Mechanical Engineering and years of experience with computer controlled engine & emissions management. For that reason, I would follow their lead. The Coyote DHOC engine proves that they can get big HP and still keep in in the area where it passes all the MPG & emissions requirements. They must know how to do it right to have that kind of success.
  15. That's still not what I would call objective evidence, it's anecdotal at best. There are a lot of other variables that could influence fuel pump selection for individual vehicles.

    Even though it's apples and oranges since the Coyote uses a returnless-style fuel system, it's worth noting that the Boss 302 used the same fuel pump as the base V6 cars of the same year.
  16. For sake of argument Id think that a 320lph pump on the tfs 170/"gt40" and typical cam with no future mods planned would be like driving a dually to deliver a bag of play sand, but everyone seems to go with the walbro 255 and then complain its noisy. does anyone have experience with the tre or highflow or some other brand? and would 255 be a good middle ground or a 155-190?
    there's always the high probability boost may follow in any build and dropping the tank is a pain....
  17. If you're going to take the time to drop the tank and change the pump, I'd go nothing smaller than a 190lph unit...and even then only in a N/A application.
    89oem and A5literMan like this.
  18. For a TFS (H/C/I) top end, would a 190lph, 30# injectors w/ 75mm MAF (recalibrated to 30's) & 70mm TB work well together?
    A5literMan likes this.