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At 12.5:1 Compression, Will We Need Premium Octane Fuel?

Discussion in 'Elio Drivetrain' started by Maurtis, Jul 23, 2016.

  1. Maurtis

    Maurtis Elio Addict

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    I was wondering this morning, with a high compression engine would the Elio need premium octane gas to make the 55HP and 84 MPG? I know that in a lot of modern engines requiring premium you can put in lower octane gas and the ECU retards the timing to prevent pre-ignition but that cuts power and MPG quite a bit. Apparently the 11:1 CR Coyote 5.0L Mustang engines are like that. They specify premium to get the advertised numbers but a lot of owners run regular to save money and just take the performance hit.

    Has there been any mention recently from Elio about what grade gas we will need? Searching online only turned up speculation from 2014.

    The difference between grades would mean an extra $2 per tank fill up. With the increased MPG over other cars it is still a big win.
     
    acamara likes this.
  2. skygazer6033

    skygazer6033 Elio Addict

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    The Elio engine was designed from the start to operate on regular unleaded gasoline. I believe all the Mazda Skyactive engines are 12 - 12.5 to one and operate on regular. I've read nothing from EM to the contrary so until we hear different regular it is.
     
  3. WilliamH

    WilliamH Elio Addict

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    I knew I had seen the answer to your question on an official site so I spent 5 minutes and dug it up.
    So here it is..........
    ---> https://www.eliomotors.com/features/#details <---
    Hope that answers your question.
    (Under 'Technical Features Include')
     
  4. Maurtis

    Maurtis Elio Addict

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    Awesome, thanks fellas, that is exactly what I wanted to know. Easier on the wallet and also means that an ECU tune for premium gas might be good for some more power too :)
     
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  5. pistonboy

    pistonboy Elio Addict

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    In the "old" day, any engine with a 12.5:1 compression ratio definitely needed high octane fuel. Today, who know? Things are much different. A lot of exhaust gas is recirculated. So, it appears there is a proper fuel-to-air ratio mixture added with a lot of inert exhaust gas.

    Wikipedia says: "exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. This dilutes the O2 in the incoming air stream and provides gases inert to combustion to act as absorbents of combustion heat to reduce peak in-cylinder temperatures. NOx is produced in a narrow band of high cylinder temperatures and pressures."

    Perhaps it also prevents pre-ignition (knocking) of the fuel mixture as well.as well.
     
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  6. electroken

    electroken Elio Addict

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    There is a bit of comparing apples to oranges here.

    Engines with direct injection like the above mentioned Mazda Skyactiv or my wife's Kia Optima are designed with 12.5:1 compression and run fine on 87 octane regular. The fuel doesn't pre-ignite simply because it isn't present in the cylinder yet and tends to cool off the compressed air in the cylinder when it does get there near top dead center.

    The Elio engine is not direct injected, instead using more traditional port injection. It will need to rely on EGR, and a good swirl design in the cylinder head to avoid pre-ignition.
     
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  7. Maurtis

    Maurtis Elio Addict

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    True, I keep forgetting the Elio motor is not direct injected to save on cost. I am good with port injection since we will not have to worry about valve coking issues in the long run.
     
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