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Discussion in 'Lawn Mowing Equipment' started by GMLC, May 4, 2013.

  1. GMLC

    GMLC LawnSite Platinum Member
    Posts: 4,353

    Im sorry I forgot to post this a month ago. The 52" XF1 and XF2 use the same exact factory high lift marbain blades.



  2. puppypaws

    puppypaws LawnSite Fanatic
    Posts: 8,915

    I find this strange, I've been running a Kohler efi since 2006 and I've never heard it run anything but perfect, and has always started at what seems instantaneously no matter the temperature cold or hot.

    I can start the engine and within 5 seconds engage the blades at its idle rpm's, with it hardly changing sounds.

    I find it odd that your efi would act cold, I've never seen this, and I've started mine at 20° while sitting in an open shed. The engine turned over and it was running perfectly, completely different from a carburetor type engine where you need to play with the choke.

    My 35 Kawasaki cranks very good in cold weather, choke it, spin the engine maybe 3 times, push the choke down 75% and it's running, but it is no where comparable to the way my efi starts and runs.

    TLS, you've had a great deal of experience with the Kohler 28 efi, and now your new Kohler BB with the Delphi system, how do they crank and act in comparison?
  3. GMLC

    GMLC LawnSite Platinum Member
    Posts: 4,353

    Puppy does the Kohler EFI start in open loop? If so it would run a bit different until it goes into closed loop. I have never run one.
  4. puppypaws

    puppypaws LawnSite Fanatic
    Posts: 8,915

    Yes, all efi's with closed loop starts in open loop, that's why I was confused about what Kawasaki said concering the hybrid system they spoke of.

    This will explain EFI in detail:

    The Electronic Fuel Injection (EFI) system is a
    complete engine fuel and ignition management
    design. The system includes the following principal
    • Fuel Pump
    • Fuel Filter
    • Fuel Rail
    • Fuel Line(s)
    • Fuel Pressure Regulator
    • Fuel Injectors
    • Throttle Body/Intake Manifold
    • Engine Control Unit (ECU)
    • Ignition Coils
    • Engine (Oil) Temperature Sensor
    • Throttle Position Sensor (TPS)
    • Speed Sensor
    • Oxygen Sensor
    • Wire Harness Assembly & Affiliated Wiring,
    • Malfunction Indicator Light (MIL)
    The EFI system is designed to provide peak engine
    performance with optimum fuel efficiency and lowest
    possible emissions. The ignition and injection
    functions are electronically controlled, monitored and
    continually corrected during operation to maintain the
    theoretical ideal or “stoichiometric” air/fuel ratio of
    The central component of the system is the Motronic™
    Engine Control Unit (ECU) which manages system
    operation, determining the best combination of fuel
    mixture and ignition timing for the current operating
    An electric fuel pump is used to move fuel from the
    tank through the fuel line and in-line fuel filter. A fuel
    pressure regulator maintains a system operating
    pressure of 39 psi and returns any excess fuel to the
    tank. At the engine, fuel is fed through the fuel rail
    and into the injectors, which inject it into the intake
    ports. The ECU controls the amount of fuel by varying
    the length of time that the injectors are “on.” This can
    range from 1.5-8.0 milliseconds depending on fuel
    requirements. The controlled injection of the fuel
    occurs each crankshaft revolution, or twice for each 4-
    stroke cycle. One-half the total amount of fuel needed
    for one firing of a cylinder is injected during each
    injection. When the intake valve opens, the fuel/air
    mixture is drawn into the combustion chamber,
    ignited, and burned.
    The ECU controls the amount of fuel being injected
    and the ignition timing by monitoring the primary
    sensor signals for engine temperature, speed (RPM),
    and throttle position (load). These primary signals are
    compared to preprogrammed “maps” in the ECU
    computer chip, and the ECU adjusts the fuel delivery
    to match the mapped values. After the engine reached
    operating temperature, an exhaust gas oxygen sensor
    provides feedback to the ECU based upon the amount
    of unused oxygen in the exhaust, indicating whether
    the fuel mixture being delivered is rich or lean. Based
    upon this feedback, the ECU further adjusts fuel input
    to re-establish the ideal air/fuel ratio. This operating
    mode is referred to as “closed loop” operation. The
    EFI system operates “closed loop” when all three of
    the following conditions are met:
    a. The oil temperature is greater than 35°C (86°F).
    b. The oxygen sensor has warmed sufficiently to
    provide a signal (minimum 375°C, 709°F).
    c. Engine operation is at a steady state (not starting,
    warming up, accelerating, etc.).
    During “closed loop” operation the ECU has the
    ability to readjust temporary and learned adaptive
    controls, providing compensation for changes in
    overall engine condition and operating environment,
    so it will be able to maintain the ideal air/fuel ratio of
    14.7:1. The system requires a minimum engine oil
    temperature greater than 55°C (130°F) to properly
    adapt. These adaptive values are maintained as long
    as the ECU is “powered up” by the battery.

    During certain operating periods such as cold starts,
    warm up, acceleration, etc., an air/fuel ratio richer
    than 14.7:1 is required and the system operates in an
    “open loop” mode. In “open loop” operation the
    oxygen sensor output is not used, and the controlling
    adjustments are based on the primary sensor signals
    and programmed maps only. The system operates
    “open loop” whenever the three conditions for closed
    loop operation (above) are not being met.
    Last edited: Jun 20, 2013
  5. GMLC

    GMLC LawnSite Platinum Member
    Posts: 4,353

    Im just wondering if what PCS is feeling is when its still in open loop. Once in closed loop the computer is adjusting the fuel mixture based on actual readings. I don't know how advanced Kohlers closed loop system is or how long it stays in open loop?
  6. GMLC

    GMLC LawnSite Platinum Member
    Posts: 4,353

    Puppy I just saw the additional info you posted, thanks. So it is a pretty advanced system. It doesn't appear to use heated oxygen sensors and that means it will stay in open loop for a few minutes before going into closed loop. I bet that is what PCS is feeling.
  7. puppypaws

    puppypaws LawnSite Fanatic
    Posts: 8,915

    I've only had experience with two Kohler efi engines, and they have both cranked and run to perfection. Maybe if someone reads this that understands open and closed loop a little better than me, they can explain how an engine with efi technology can start in open loop so much better than a carburetor type engine.

    I guess it's possible they don't all start equally, and I have been fortunate to get two that has been exceptional. I would say the big blocks may start differently, and that is why I would like TLS to answer this question, he's had experience with both.
  8. ProStreetCamaro

    ProStreetCamaro LawnSite Platinum Member
    Posts: 4,140

    That is my guess a well. It runs smooth at first start but if I try to move the mower right away at anything less than half throttle it will chug a little. Not really a problem just an observation.
  9. GMLC

    GMLC LawnSite Platinum Member
    Posts: 4,353

    Even when in open loop EFI is still waaay more precise than a choke covering a carb venturi. The computer still uses some data from sensors in open loop just not the oxygen sensors.
    Posted via Mobile Device
  10. GMLC

    GMLC LawnSite Platinum Member
    Posts: 4,353

    Oops I keep calling PSC, PCS sorry....
    Posted via Mobile Device

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