To Boost - or not to Boost

  • so adding turbo throws off the gas mileage by how much?

    Fuel economy in the Slingshot is measured by injector pulse. So when you add a larger injector that pulses less than the factory you will actually see the fuel economy increase which is a false reading. However, I know with both DDM and ZZP, we both have corrected that data in our supplied tunes so your mileage really shouldn't change much unless you keep the pedal all the way down with the new found power.

    ZZPerformance EST 2000 - Go Fast Not Broke

  • Due to the direct link between RPM and boost that SCs have, I'd expect lower mileage since you're going to use more fuel as RPM/Boost increases. Turbos lack the direct link between RPM and Boost, so driving more carefully and keeping boost off, it should be possible to drive w/o experiencing the additional gas flow boost brings. If you have larger injectors, there will be more fuel flowing thru the injectors, but in vacuum conditions (no Boost), although the larger injectors are injecting more fuel than the stock injectors would, the engine should still be using less fuel than when under boost.

    Before I installed my Hahn Stage 2 Turbo kit, I got around 28 MPG with my Twist Dynamics Top and MadStad Single Adjustable 13" windshield. After the install, driving the same roads and in a similar style (rapid acceleration from stops and occasional boosted periods when passing), my MPG dropped to around 26. I sometimes see MPG drop as low as just under 25 MPG and sometimes a little over 27 MPG, but most of the time, I see around 26 MPG.

    Edited once, last by BKL ().

  • I bought mine to have fun. I don’t watch mikes per gallon. I do watch the fuel gauge go down quickly but nothing like listening to the V8 rumble.



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  • Due to the direct link between RPM and boost that SCs have, I'd expect lower mileage since you're going to use more fuel as RPM/Boost increases. Turbos lack the direct link between RPM and Boost, so driving more carefully and keeping boost off, it should be possible to drive w/o experiencing the additional gas flow boost brings. If you have larger injectors, there will be more fuel flowing thru the injectors, but in vacuum conditions (no Boost), although the larger injectors are injecting more fuel than the stock injectors would, the engine should still be using less fuel than when under boost.

    Before I installed my Hahn Stage 2 Turbo kit, I got around 28 MPG with my Twist Dynamics Top and MadStad Single Adjustable 13" windshield. After the install, driving the same roads and in a similar style (rapid acceleration from stops and occasional boosted periods when passing), my MPG dropped to around 26. I sometimes see MPG drop as low as just under 25 MPG and sometimes a little over 27 MPG, but most of the time, I see around 26 MPG.

    I believe this is incorrect. In fact, I know it. The supercharger tune for the big injectors has adjusted and will still monitor air/fuel ratio. My Slingshot now has the lighter blow off spring, and blows off all boost if driving easy, even up into higher RPM (got it from Painter , thank you Dave@DDMWorks ). The SC does use a little power to turn it, so that will drop the MPG by a small amount. But I have the larger injectors, they only dump what I am calling for.... the air/fuel is still held (but can put plenty in it needed). If I'm revving up high with the pedal down, then yes.... the larger injectors will supply plenty of fuel (still within the air/fuel ratio that's programmed). But at lower or light throttle at most all RPM, it won't be dumping more fuel in unless boost is added..... only enough more to run the SC.

    I've gotten as low as 23 with the MeanSling Top at 80 MPH into a headwind. If I would push it, I'm sure it could be in the teens easily. But normal driving with some spirited hits along the way, I will get 25 up to 28 mpg. I've gotten as high as 30, but it was a gentle back roads day. My plugs look great, little soot if any. Only issue I have is at cold (engine) temps, I either let it warm enough or have throttle hesitation until it warms. I have the original tune sold with the Big Kahuna package. I'm very happy with it all, so I've left it alone!

    I don't look at this thing as a Prius. Within reason (mine does this with ease), MPG matters much less when compared to the the fun I get from it. Right foot down, if it puckers your tail then it's enough! This one is enough.... Smiles for miles!

  • I believe this is incorrect. In fact, I know it. The supercharger tune for the big injectors has adjusted and will still monitor air/fuel ratio. My Slingshot now has the lighter blow off spring, and blows off all boost if driving easy, even up into higher RPM (got it from Painter , thank you Dave@DDMWorks ). The SC does use a little power to turn it, so that will drop the MPG by a small amount. But I have the larger injectors, they only dump what I am calling for.... the air/fuel is still held (but can put plenty in it needed). If I'm revving up high with the pedal down, then yes.... the larger injectors will supply plenty of fuel (still within the air/fuel ratio that's programmed). But at lower or light throttle at most all RPM, it won't be dumping more fuel in unless boost is added..... only enough more to run the SC.

    I've gotten as low as 23 with the MeanSling Top at 80 MPH into a headwind. If I would push it, I'm sure it could be in the teens easily. But normal driving with some spirited hits along the way, I will get 25 up to 28 mpg. I've gotten as high as 30, but it was a gentle back roads day. My plugs look great, little soot if any. Only issue I have is at cold (engine) temps, I either let it warm enough or have throttle hesitation until it warms. I have the original tune sold with the Big Kahuna package. I'm very happy with it all, so I've left it alone!

    I don't look at this thing as a Prius. Within reason (mine does this with ease), MPG matters much less when compared to the the fun I get from it. Right foot down, if it puckers your tail then it's enough! This one is enough.... Smiles for miles!

    Looks Like a rethink on my part is in order as what you posted makes sense. I sometimes start typing before I fully think thru something!:/ I enjoy the extra acceleration available with my turbo, although I do try to minimize rear tire spin as I prefer to minimize how often I buy new rear tires. I also try to minimize rear wheel spin since I've been pulled after my rear end slid sideways (only a little, I swear), and the officer felt I hadn't maintained control of my vehicle, but I do enjoy the boost!;)

    Edited once, last by BKL ().

  • Forget MPG

    Hours to add fuel is they way to go. Just like a boat

    Every hour wide open = XX gallons. After about 2.5+ hours of hard running I look for a fuel stop. Most importantly due to the position of the fuel pick up. if low on fuel and in a hard turn I can see the possibility of starving the motor of fuel. Even temporarily that could be a bad and ex$pensive oops.


    But I still love every minute of it................................

    The more people I meet

    The more I love my Dog!

  • Quick question, after modding, how often do all of you sell off the stuff you removed from your sling or do you just discard it? I have the INJEN CAI that i can sell but the rest i am not too sure what to do with it besides donate to coleman powersports so if they need to fix someone elses sling? I have the stock oil pan, absolutely nothing wrong with it, and the stock header, which of course everyone knows how rusted those get, but still nothing wrong with it. and i was wondering what to do with this stuff. now of course everyone would like to recoup some of the money they spent, but, who might need or want it?

  • Quick question, after modding, how often do all of you sell off the stuff you removed from your sling or do you just discard it? I have the INJEN CAI that i can sell but the rest i am not too sure what to do with it besides donate to coleman powersports so if they need to fix someone elses sling? I have the stock oil pan, absolutely nothing wrong with it, and the stock header, which of course everyone knows how rusted those get, but still nothing wrong with it. and i was wondering what to do with this stuff. now of course everyone would like to recoup some of the money they spent, but, who might need or want it?

    Hmm? After mods are done...you can trade...or you can give them away. I have tried to give them away...but alas...I will keep them till a make a planter out of them! :thinking_face:

    Always Remember...You can drive it like you want to drive it tomorrow! 8)

    :HEADERSS::SUPERCHARGERSS::COILOVERSS::ROTORSS:

  • Quick question, after modding, how often do all of you sell off the stuff you removed from your sling or do you just discard it? I have the INJEN CAI that i can sell but the rest i am not too sure what to do with it besides donate to coleman powersports so if they need to fix someone elses sling? I have the stock oil pan, absolutely nothing wrong with it, and the stock header, which of course everyone knows how rusted those get, but still nothing wrong with it. and i was wondering what to do with this stuff. now of course everyone would like to recoup some of the money they spent, but, who might need or want it?

    Keep in case you trade up, you can put all of the pieces back on the old Sling

  • Keep in case you trade up, you can put all of the pieces back on the old Sling

    I agree with this and I also kept my original coilovers as a backup set just in case I were ever to need to send my JRI's in for a rebuild - - wouldn't want any downtime waiting for them to come back and having the originals would help avoid this.


    :thumbsup:


    Edit as a side note If I were to ever part with my slingshot I think I would rather re install the stock parts first and then give my friends here the mods - - - much better than just wasting them

    Cage Free - 2016 Pearl Red SL

    DDM Short Shifter, Sway Bar Mounts & Master Cylinder Brace

    Twist Dynamics Sway Bar, JRI GT Coilovers, Assault Hood Vent

    OEM Double Bubble windshields & various other goodies