Fuel Pressure

    Was having difficulty finding a thread regarding Fuel Pressure. Point me in that direction and I will add to it. :)


    What is stock Fuel Pressure? (about 58psi?)


    rabtech  Dave@DDMWorks  Kyle D and All,

    - I'm trying to avoid E85, for a couple reasons... At what HP running 93 octane will I need to upgrade the fuel pump?

    rabtech I know you mentioned 450whp no problem (511whp peak bursts), but then I notice a thread where you replaced the fuel pump and I think you are running 93 octane?


    - At what HP/BoostPressure running 93 octane should go with a manifold pressure referenced fuel pressure regulator?


    - What is recommended constant fuel pressure at 500whp?


    - What is recommended injector size for suggested fuel pressure at 500whp?


    Note: I'm aiming for 500whp (on my current DDM Stage 3 Turbo) with future DF Project 324 8.6" LSD to lay it down.



    Kyle D, Thank you for the previous data which I will continue to refer to. :)

    DDM Stage 3 Turbo / Intercooler / Fuel Rail / Track Clutch

    Magnaflow Short Exhaust / GM 2 Bar MAP Sensor / 60# Fuel Injectors / AEM Air/fuel Gauge / Glow Shift Boost Gauge

    Stock: Radiator, Coolant Resevoir, ECU with Tune, Intake Manifold, Suspension, Brakes

    Stock: 305/45R18 Nitto NT555R not enough traction

    Fuel pressure is 60psi. You want to keep it at 50psi or above. You shouldn't need to upgrade your in tank pump. In my scenario,
    I ran E85 through my stock pump and it took me to around 400-450whp. E85 has a 20%-40% higher fuel demand and the stock pump was able to keep up just fine. The E85 killed the stock pump as it is not set up for that and the dryness of that fuel took the pump out. I then switched to the green AEM E85 pump which will flow E85 or gasoline and that pump has taken me to 550whp.



    - At what HP/BoostPressure running 93 octane should go with a manifold pressure referenced fuel pressure regulator? You're not going to need one. You're going to run out of fuel line flow capacity before you need a boost reference system. I'm JUST adding one this year as I go past 26psi running a blend of E98 and 110 with 160# injectors and I'm also now needing to upgrade the size of the fuel line to -8. Could probably use -6 but I don't ever want to do it again. I also did all this on the stock fuel rail.


    - What is recommended constant fuel pressure at 500whp? You always want your pressure to stay above 50-52psi regardless of power level.


    - What is recommended injector size for suggested fuel pressure at 500whp? To get to your goal you'd want to go to 80# injectors but again, you're not going to get to 500whp on just 93 octane. It's going to be hard to get that 7163 turbo you have to 500whp gasoline. Its peak efficiency is 25-27psi and it starts falling off pretty hard after that. You can do it on E85 but its a max effort build.


    Hope that helps a little.

    ZZPerformance EST 2000 - Go Fast Not Broke

    Stock fuel pressure that we have seen is 58psi on most Slingshots we have tested.


    I would say it is more of a boost pressure thing than a HP rating for when you will want to upgrade the fuel pump, not really need to change it. As you increase boost pressure in the intake manifold the pressure delta across the fuel injector (fuel pressure minus boost pressure) starts to decrease, therefor for the same injector pulse length, less fuel comes out of the fuel injector, this then requires longer and longer injector pulse lengths at higher boost pressures. by going to a boost regulated fuel pressure setup on higher boost setups, it makes tuning much easier and also the injector pulse length on the same set of injectors can be kept shorter allowing more headroom in the injector. The other thing that lower fuel pressure delta causes is poor atomization of the fuel compared to higher pressure. You can ask rabtech of his experience with this, but we have basically the same setup and were able to get 80# injectors to work very well at those power levels without going completely static.


    That being said, really as low as 15psi I would say you will start to see a benefit from going boost regulated setup on the fueling, not needed, but it is nice. I would definitely recommend it over 20psi, otherwise your fuel injectors are basically only seeing 38psi of pressure, which sucks for fuel atomization and flow.


    On all of the boost regulated setups we have done, we set the pressure to 58psi.


    We are running 80# fuel injectors on ours and it is working great.


    As for the EFR 71623 in the Stage 3 kit, even if you run it wide open with no wastegate control you will not see over 26-27 psi at the airflows you will be seeing, rabtech has done it and we have maxed it out also, it just can not flow more pressure than that on the 2.4L.


    Give a call or let us know if you have any other questions,

    Hope that helps,

    Dave

    Kyle D Definitely some golden info in there. Thank you!

    (FUEL) Regarding manifold pressure referenced fuel pressure regulator, I believe as manifold pressure increases then fuel pressure differential across the injector decreases.


    Example:

    Provided 60psig = 74.7psia and estimating maximum 26psig boost

    (NA) 74.7psiaFuelRail - 14.7psiaManifold = 60psiaInjectorDifferential

    (Boosted) 74.7psiaFuelRail - 40.7psiaManifold = 34psiaInjectorDifferential

    Although injector pressure differential is not super linear with respect to flow vs pressure changes. Assuming a linear relationship, we might need bigger injectors with 76% greater flow rating to achieve the same job, without the application of a manifold pressure referenced fuel pressure regulator.


    I think ECU tuning injector pulse width and maintaining a smooth idle may be easier by avoiding 76% larger injectors and providing a constant injector pressure differential.


    (AIR) Regarding Max whp on 25-27psig, I think I am are running about 300whp at 9psig (23.7psia) at current unknown temp.

    Example:

    At constant manifold temp, changes to absolute manifold pressure is proportional to changes in air mass.

    Assuming I can maintain similar manifold temp, through extra cooling, at 9psig (23.7psia) to 26psig (40.7psia).

    26psig of boost will be about 515whp, potentional air mass.


    Do these values seem logical?


    Kyle D Great information and I appreciate your feedback, on this journey :)

    DDM Stage 3 Turbo / Intercooler / Fuel Rail / Track Clutch

    Magnaflow Short Exhaust / GM 2 Bar MAP Sensor / 60# Fuel Injectors / AEM Air/fuel Gauge / Glow Shift Boost Gauge

    Stock: Radiator, Coolant Resevoir, ECU with Tune, Intake Manifold, Suspension, Brakes

    Stock: 305/45R18 Nitto NT555R not enough traction

    Dave@DDMWorks

    Any recommendations on the fuel system components to match 26psi boost? I don't think there was anything posted on the website.

    I'm assuming Rabtech was running 511whp on 93 octane, considering the 80# injector, if I'm putting the puzzle pieces together correctly. :)

    DDM Stage 3 Turbo / Intercooler / Fuel Rail / Track Clutch

    Magnaflow Short Exhaust / GM 2 Bar MAP Sensor / 60# Fuel Injectors / AEM Air/fuel Gauge / Glow Shift Boost Gauge

    Stock: Radiator, Coolant Resevoir, ECU with Tune, Intake Manifold, Suspension, Brakes

    Stock: 305/45R18 Nitto NT555R not enough traction

    A little off-topic, but I LOVE pictures just like this one. They help me understand the anatomy of my Slingshot without having to tear the damn thing apart! ...lol Thanks! :D

    "If I were a Jedi, there's a 100% chance I would use the force inappropriately!"

    Quote from Airborne

    Dave@DDMWorks

    Any recommendations on the fuel system components to match 26psi boost? I don't think there was anything posted on the website.

    I'm assuming Rabtech was running 511whp on 93 octane, considering the 80# injector, if I'm putting the puzzle pieces together correctly. :)

    I can get you the list of what we did to our Slingshot for the system, shoot me over an email - dave@ddmworks.com


    As far as I remember rabtech was on 93 octane for that run, I am sure he can answer for sure.

    The other thing with the respect to fuel injector sizing that is not mentioned above is RPM of the engine. As engine RPM increases the time for the injector pulse width (intake valve opening) gets shorter and shorter, so this all becomes even more important as engine RPM goes higher also and needs to be considered also.

    you're forgetting that required drive pressure on the turbine side increases as boost pressure goes up, and it does so at a faster rate than the boost is climbing. Your guesstimations are only accurate if you had a magic turbine that used the same drive pressure at any boost level.
    At 9psi it's likely you're near or even under under a 1:1 backpressure ratio. at 26 on a 7163 you're going to be well beyond 1:1, likely seeing backpressure in the mid 30's at high rpm.


    To make 500 wheel on a 7163 with pump 93, you're going to have to push to the ragged edge and STILL hunt for the happiest dyno you can find. I know that's not what you want to hear, but that's the reality.

    also, this talk of atomization at high boost is kind of silly when you're spraying on the back of a closed valve any time you're past 25%idc. the fuel mostly vaporizes from the heat of the valve and the remaining liquid is atomized as soon as the valve cracks open. Hell OEMs have been spraying on the back of the valve on PURPOSE for decades in a lot of cars.
    Yeah you need a usable pressure differential, but it's simply because you have to be able to hit your mass flow. These cars/bikes need a feed line upgrade long before a referenced regulator IME.

    [quote='Airborne','https://slingshotinfo.com/index.php?thread/9110-fuel-pressure/&postID=305970#post305970']

    Dave@DDMWorks

    Any recommendations on the fuel system components to match 26psi boost? I don't think there was anything posted on the website.

    I'm assuming Rabtech was running 511whp on 93 octane, considering the 80# injector, if I'm putting the puzzle pieces together correctly. :)

    [/quote]

    From what I remember from talking to rabtech anytime he was making numbers in the 500+ neighborhood he was running a blend of 93 and race gas. From what he’s told me E85 isn’t available in his area. But he would be the one to confirm that.



    ZZPerformance, Go Fast Not Broke
    EST 2000

    ZZPerformance EST 2000 - Go Fast Not Broke

    Quote from ARM

    also, this talk of atomization at high boost is kind of silly when you're spraying on the back of a closed valve any time you're past 25%idc. the fuel mostly vaporizes from the heat of the valve and the remaining liquid is atomized as soon as the valve cracks open. Hell OEMs have been spraying on the back of the valve on PURPOSE for decades in a lot of cars.
    Yeah you need a usable pressure differential, but it's simply because you have to be able to hit your mass flow. These cars/bikes need a feed line upgrade long before a referenced regulator IME.

    From tuning experience at ZZP then, the fuel atomization on a boosted 2.4L engine running an EFR 7163 at 25psi of boost pressure using #80 fuel injectors with a 33# pressure delta is considered acceptable? You consider 33# of fuel pressure a usable pressure differential at the fuel injector?

    ARM

    DDM Stage 3 Turbo / Intercooler / Fuel Rail / Track Clutch

    Magnaflow Short Exhaust / GM 2 Bar MAP Sensor / 60# Fuel Injectors / AEM Air/fuel Gauge / Glow Shift Boost Gauge

    Stock: Radiator, Coolant Resevoir, ECU with Tune, Intake Manifold, Suspension, Brakes

    Stock: 305/45R18 Nitto NT555R not enough traction

    Quote from Dave@DDMWorks

    From tuning experience at ZZP then, the fuel atomization on a boosted 2.4L engine running an EFR 7163 at 25psi of boost pressure using #80 fuel injectors with a 33# pressure delta is considered acceptable? You consider 33# of fuel pressure a usable pressure differential at the fuel injector?


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    Quote from Dave@DDMWorks

    From tuning experience at ZZP then, the fuel atomization on a boosted 2.4L engine running an EFR 7163 at 25psi of boost pressure using #80 fuel injectors with a 33# pressure delta is considered acceptable? You consider 33# of fuel pressure a usable pressure differential at the fuel injector?

    did you even read what I said? If it’s enough to get the required mass flow, then it’s enough.
    kyle is the fastest in the world with a ~33psi differential.
    Real world trumps keyboard thumping.

    Quote from ARM

    did you even read what I said? If it’s enough to get the required mass flow, then it’s enough.
    kyle is the fastest in the world with a ~33psi differential.
    Real world trumps keyboard thumping.

    Is that a Yes to both questions?


    ARM with your tuning at ZZP, Kyle only has the fastest speed in the 1/2 mile for now, a great accomplish for sure. However, maybe you are not aware we have a faster speed recorded in the 1 mile and faster than even Kyle thought anyone would go before the event.

    Quote from Dave@DDMWorks

    Is that a Yes to both questions?


    ARM with your tuning at ZZP, Kyle only has the fastest speed in the 1/2 mile for now, a great accomplish for sure. However, maybe you are not aware we have a faster speed recorded in the 1 mile and faster than even Kyle thought anyone would go before the event.

    You can drop the passive-agressive BS at any time, You've been that way to me from day one and it's pretty annoying.
    Anyone that looks at the results can easily tell you were only the fastest because kyle wasn't there. Your 1/2 speed wasn't even close.

    REGARDLESS....


    This thread is about a guy being fed false hope that he's going to make a true 500whp on pump 93. And somehow people have convinced him that he just needs enough pressure? It's absurd.
    There's a hundred different calculators online that convert mass fuel flow into approximate HP. Witchhunter is a good start. However, flowing 500hp worth of fuel does not mean you're going to make 500hp; those calculators are assuming you're NOT knock limited. It's disturbing that people would sit here leading him on, as if buying the right fuel system parts is somehow going to get around that.

    Quote from ARM

    You can drop the passive-agressive BS at any time, You've been that way to me from day one and it's pretty annoying.
    Anyone that looks at the results can easily tell you were only the fastest because kyle wasn't there. Your 1/2 speed wasn't even close.

    REGARDLESS....


    This thread is about a guy being fed false hope that he's going to make a true 500whp on pump 93. And somehow people have convinced him that he just needs enough pressure? It's absurd.
    There's a hundred different calculators online that convert mass fuel flow into approximate HP. Witchhunter is a good start. However, flowing 500hp worth of fuel does not mean you're going to make 500hp; those calculators are assuming you're NOT knock limited. It's disturbing that people would sit here leading him on, as if buying the right fuel system parts is somehow going to get around that.

    Not sure if you have me confused with someone else, but this thread is the first time I have ever responded to any of your comments on this forum.


    As to wether Kyle would have been faster or not at the same track on the same day is debatable since traction is going to be a big factor in the 1/2 mile speeds and that traction changes from track to track. Kyle set his record at one place, we set ours at another place, he may have been faster at the event we were at, just as we may have been faster at the event he was at.


    That also brings up another point with 500hp at the wheel builds and traction of the rear tire on the street. From all the 425+ rear wheel HP builds we have done here, at that power level usually you can break the rear tire loose at almost any speed in 4th gear. So if he makes 485HP or 515HP at the rear wheel with all the weight he has removed from that Slingshot, there will be even less traction on the rear tire and he will not be able to put that power down anyway. Once he gets to the top of 4th gear, the aero loads with that exposed frame is also going to be pretty high.


    Even at a road course like the racetrack in Savannah we were at this last time we were only running 17psi on the 7163 with a Toyo R888R on the back and stayed in 4th gear the entire lap since we could break the tires loose at any RPM above 2200. Until traction is taken care of you can make all the power you want, but the Slingshot will not be faster. In the video you can hear the rear tire breaking loose coming off the turns and on the straight -


    Quote from ARM

    You can drop the passive-agressive BS at any time, You've been that way to me from day one and it's pretty annoying.
    Anyone that looks at the results can easily tell you were only the fastest because kyle wasn't there. Your 1/2 speed wasn't even close.

    REGARDLESS....


    This thread is about a guy being fed false hope that he's going to make a true 500whp on pump 93. And somehow people have convinced him that he just needs enough pressure? It's absurd.
    There's a hundred different calculators online that convert mass fuel flow into approximate HP. Witchhunter is a good start. However, flowing 500hp worth of fuel does not mean you're going to make 500hp; those calculators are assuming you're NOT knock limited. It's disturbing that people would sit here leading him on, as if buying the right fuel system parts is somehow going to get around that.

    Oh Well, I just added another to the block