Fuel Pressure

    Wow
    This thread went down hill fast.
    There is absolutely no reason to talk crap about Dave or Kyle.
    They both have put many HARD hours into real world testing and trial and error is not cheap to do. We as watchers and key peckers then get the advantage of all their experience. These guys openly share their information with us all for free instead of sitting on it and slowing the further growth of the sport. In the Five years I’ve been with the slingshot since before we all got the first delivery, we have very few performance companies still in the game. I Thank You both for this and would run either set up in a second.



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    ARM  Dave@DDMWorks  Kyle D

    I'm glad to have all of this expertise from the Pros. :)


    At this time I'm willing to give up some HP, to avoid E85 or Haltech's Flexfuel. ARM  Kyle D I am aware of some E85 benifits from experience.


    I think we can all agree 450whp might be possible on 93 octane. I might even be OK with 425whp on 93 octane, before switching to water/meth injection, E85 or additional boost.


    Dave@DDMWorks Thank you for the 15-20psi boost recommended threshold for switching to manifold pressure referenced fuel pressure regulator (MPRFPR).

    ARM  Kyle D I am aware MPRFPR is not mandatory, but I think it will help with tuning and idle smoothness. Perhaps a personal preference... :)


    You guys/gals are great! :00000430:

    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

    IN THE WORD OF KID ROCK "THEY SAY I AM COCKY" WELL BOTH DAVE AND KYLE D CAN BACK THAT ATTITUDE UP WITH THE PERFORMANCE OF THEIR SLING SHOTS AND THEIR KNOWLEDGE.

    'It's about the ride not the destination"

    Fuel pressure is a mechanical issue. It has nothing to do with the ECU. You just have to make a return fuel system for the fuel to be able to flow back to the tank. Then install a boost referenced fuel pressure regulator. You want to set it at 55psi. The run your vacuum line (boost pressure) over to it. For every positive pound of boost the fuel pressure will increase to match it. It is a totally stand alone system.


    Now i didnt go back very far and read a bunch of the previous post so if i missed something just let me know.

    rabtech True. Thank you for the feedback. Luckily DDM Fuel Rail has enough extra ports for return line and fuel pressure sensor (which will go to my Haltech analog input, future)

    Do you have makes and models of the components you are running for the fuel system or recommended parts if you did it again?

    - Fuel Pump (to reach 55psi + Boost)

    - Manifold Pressure Referenced Fuel Pressure Regulator (MPRFPR)

    - Fuel Filter

    - Accessories


    Trying to build a road map for me and future 93 octane fuel system builders.

    Your support is much appreciated :)

    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 ARM

    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.

    i dont ever push mine past 16psi unless i have a 50/50 mix of 110 low lead / and 93 chevron super unleaded. The most i have seen is 20psi on the long runs and 23psi on brief highway passes. (With my butt clenched)


    I believe its possible to push a little more than 16psi on 93 but i have experienced some knock at 16psi even with the mixed fuel when trying to put more timing in it. Some will tell you how water/meth helps but i dont run it.


    I have the ability to watch every possible aspect except individual header temps. And i will tell anyone that pushing past 14 to 16 is eventually going to get into your pocket book.


    Here is my take on having a dependable fast and fun slingshot..... Build the engine and make it tough as nails. Then add boost and plenty of fuel. Never push it past 8 or 9 psi on an LE5 or LE9 block and never past 14 to 16 on the LEA block. Why???? Because we know the limits of 93 octane and what each block can stand. And the only reason to push these engines past 16psi would be if your were on a airfield holding the throttle pinned for 1/2 mile or further.


    Also there is no reason to change the fuel pump and make it a return style system if you keep the boost down to 14 or even 16psi. 14 is the happy spot. I have never seen or heard of an engine running lean at those levels with a centerfed fuel rail.


    That is my take on it.

    rabtech Great videos and detail! Thank you!


    1) What is the fuel pressure from the pump (before the regulator) at those flowrates? above 82psi, but wonder the actual... :)


    2) Looks like you are running about 12.8 AFR and 45% injector duty cycle. Do you think it is possible to run higher injector duty cycle and consequently 9-10 AFR, to significantly reduce cylinder temps and delay early combustion (knock)?


    3) Here the AFR is better, but the Ignition Timing is in the teens...

    Do you ever get the fuel injectors near 90-95% duty cycle @ 23-24psig manifold pressure?


    4) Do you have makes and models of the components you are running for the fuel system or recommended parts if you did it again?

    - Fuel Pump (to reach 55psi + Boost) = Stock Polaris (Max ??psig @ 24psiBoost/12.8AFR/45%InjectorDC)

    - Manifold Pressure Referenced Fuel Pressure Regulator (MPRFPR)

    - Fuel Filter


    My apologies if I am misstating something here. And thank you for your support and time. :)

    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

    RABTECH. I apologize for the mistake, You are in the same class as the others with your knowledge, I bow down to all of you on this board for your commitment and wiliness to share your knowledge.

    'It's about the ride not the destination"

    Airborne It would be better for you to reach out to Dave and let him give you the details. Dave@DDMWorks has invested an amazing amount of time and money getting my Slingshot to the point that it is now. Im sure you understand what im saying. Its just bad juju to walk on their toes. Dave will share with you whatever he feels is ok.


    I even have some special tuning and parts that were done by ZZP for my Slingshot. Kyle D would be the one at ZZP to give you that info.


    The parts I run are no big secret but the tune I run has been worked on till its literally flawless for what i do. Even my automatic transmission ecu has a tune in it that operates it like it came from the factory with a dual clutch tranny.