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Author Topic: Gas Mileage  (Read 6978 times)

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Offline Painlesstom

  • Painless Tom
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  • Engine: EX21 w/17 head - ES
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Re: Gas Mileage
« Reply #15 on: December 08, 2012, 12:53:35 AM »
Welcome to the forum.  :)

From what I've read about the fuel injection used on those motors, it is very limited and not as much of a benefit as intended. I also have read that it has a built in rpm limiter that could be difficult to bypass. The only way you would really get the fuel efficiency of a real fuel injection system, is for it to be a closed loop speed density, or MAF, system that would utilize an O2 sensor. The fuel injection used on those EX motors is a rpm based Alpha-N type, open loop, non-feedback system. It cannot compensate for any change in air temp (other than for cold enrichment/choke) or altitude, and does not adjust fuel mixture based on anything but it's base program. The ECU looks at RPM only.

The electric start parts would probably swap over no problem though, I know the EX motors with carbs can swap parts between ES and Non ES.

No need to pop the hood to pull the choke, that's what the choke cable is for under the hull before your steering handle. ;)




Offline Hillbilly

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Re: Gas Mileage
« Reply #16 on: December 08, 2012, 11:19:43 AM »
Hello Dragon, and welcome.
Subaru came out with the fuel injected motor a few years ago. My thoughts were like yours, but it just didn't work.  They used it on a power washer sold at Home Depot.  The starting procedure was multiple steps, if it would start even then.  Reliability was poor, as was performance.  They have pulled it from the market, I think.
The Mokai factory looked at it, and found it to be totally unsuitable for the boat.  During a visit to Mokai, I spoke with Louis about the motor and he happened to have one on his dyno.  He started it and showed me just how it fell short for our application.
Hopefully, the people at Subaru are staying with the idea and will come out with a system that will work.  There are a couple of aftermarket, closed loop  EFI systems available for small one cylinder motors.  Maybe a Mokai person will show us all how to use one in our boats.
The EX motor comes off the shelf with a top mounted fuel tank and gravity feed, like other industrial motors.  Mokai adds the plastic Mikuni fuel pump, which works well with the stock EX carb.