2002 Toyota MRS Electric Power Steering Pump conversion, alternate wiring - Page 2

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  1. #11
    CelicaSupra.com Member Funkycheeze's Avatar
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    Remember, you are looking at the extra draw on the electrical system from the new EHPS system, you don't get that power for free.

    The fluid needs to be for the pump - using the fluid that matches the mk2 rack will burn out the pump (see this all the time in the MR2 world when people use regular PS fluid in the EHPS system). The 'special' fluid isn't for different seals, it actually has a different viscosity for the electric pump.
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  3. #12
    Whistles racerxj220's Avatar
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    That's what the Mechman 240A alternator is for. I've got a Walbro 450, Magnafuel 4303, this Toyota pump, and a large single 2013 Ford Focus cooling fan. Those are the big electronics, and I can run the headlights and heater, and still show 13V on the dash, with no hiccups.

    I kept reading everywhere that it was not much of a gain, but at least the engine doesn't bog down when turning the steering wheel, or need any kind of raised idle valve for it.

    What most people don't realize, is they aren't turning the steering wheel on the dyno, so it's tough to notice how much the pump is draining from the engine's power.

    The viscosity of Pentosin is much thinner in colder temperatures vs. Dextron, and I think this is when it does the most damage.

    I drove quite a bit today, and the pump operated flawlessly. It felt great, I actually did not think about the system until now. It works that well.

  4. #13
    CelicaSupra.com Member Funkycheeze's Avatar
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    Glad you are happy with it. My only point would be that the power for the EHPS system will put more draw on the alternator, which will cause the same parasitic load to the engine that a standard belt drive pump would. The EHPS might be slightly more efficient as it runs at a constant speed, as opposed to the vane pump which bypasses quite a bit of flow at high RPM.
    '84 P-type, 5spd, torrid red, black/grey leather
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  6. #14
    Whistles racerxj220's Avatar
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    I've read on some forums, the EHPS not taking anymore than 40A. I've got an 80A relay and fuse, just in case.

    Good points about the alternator picking up the slack, and I am not familiar with the parasitic loads they create. I'm on a standard billet alternator pulley, Fluidampr harmonic damper, and stock water pump pulley. I deleted the factory belt tensioner (using a 37 inch belt). This doesn't mean a lot in terms of drains or gains, just disclosing the full setup.

  7. #15
    CelicaSupra.com Member SupraFiend's Avatar
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    WELL, I don't know if I'd make that generalization. Granted, I once did back to back dyno runs with my electric fan off and then on and I made about 2hp with it off. That said, I would not say that the electrical drain from an electric motor spinning a hydrolic pump would suck down the same amount of HP via the alternator as a mechanically driven pump. Could be pretty close.

    Also if we're going to nitpick, that 240amp alt of yours probably produces a lot more parasitic drag while freewheeling with no real drain then the stocker too.
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  8. #16
    Whistles racerxj220's Avatar
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    Injector battery offset by voltage with a proper standalone, can correct for both spark and fuel injector correction at a given voltage. There is a curve that effects the fuel injectors when loads are placed on the electrical system, so you can correct for it. Some standalone's offer this feature, and it makes a difference with keeping the power consistent with all electronics on, and off.

    I've still not seen any data on how much horsepower is required to turn a 240a vs a factory alternator.

    I'd be interested to see that.

  9. #17
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    In a perfect (DC) world, power is V x A. So simply speaking @ 12V, 240A would be 3KW. 746W or 0.746KW = 1HP. So 4 HP in a perfect world or 3 HP more than our stock 60A units, assuming full output and a perfect conversion. I would assume somewhat less than perfect, so factor that in.
    But alternators don't just "put out" full load. They deliver power based on demand (load). So if you just swap in a bigger alternator and don't change the load (or anything else), nothing really changes.
    It's easier to just figure the real HP "difference" based on the additional load you're adding. Using the above, 12V x additional amps = X Watts / 746W/HP = additional HP. This must be a bit more efficient than a belt driven pump.

  10. #18
    Whistles racerxj220's Avatar
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    Some good info, Ray.

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