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Thread: Lightweight Flywheel

  1. #1
    Still Plays With Cars Loren's Avatar
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    Lightweight Flywheel

    Can't find one. Anybody got any leads?

    Barring that, anybody got access to a cheap used stock flywheel they could send me?

    I've done Fidanza and other lightweight flywheels on Miatas in the past. Love 'em! Yes, it makes launching the car a little harder, and they sometimes make a little noise. (Fidanzas are somewhat bell-shaped, and like to ring) Yes, there's probably some risk in removing some of that weight due to the fact that it's an naturally imbalanced 3-cylinder engine.

    I thought about that last bit REALLY hard. But, it seems that the Metro 3-cylinder guys have had zero problems with a lightweight flywheel. And so far I've at least found one photo somewhere (eBay Europe, or somewhere) of a 6G Mirage flywheel that indicates it's nothing special... just a plain ol' flywheel.

    So, unless I can find someone that sells one specifically for the Mirage, I'm exploring the options of either finding something that's close that can be made to fit. (maybe one for a Lancer, or anything that has the same starter gear ring) Or having a stock one lightened a little bit.

    When you have just 74 hp, every little bit helps. Shaving some flywheel weight will definitely improve acceleration.



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    Moderator Eggman's Avatar
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    Rkt Ship might have one from his old engine.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 50.1 mpg (US) ... 21.3 km/L ... 4.7 L/100 km ... 60.2 mpg (Imp)


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    Moderator inuvik's Avatar
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    My understanding of the Mirage’s 1.2 Engine (3A92) is that it is the same as the 4 cylinder (4A92) with one less cylinder. So the question is would a lightweight 4A92 flywheel bolt in?

    Also, it’s the same bore and stroke also so couldn’t you put the 11:1 compression pistons from the 4A92 replacing the 10.5:1 compression pistons in the 3A92?

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.6 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.7 mpg (Imp)


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    Still Plays With Cars Loren's Avatar
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    I'm not much of an "engine internals" tinkerer. I understand how it all works, I just don't much like doing it, and I like the relibility of an unmolested stock engine. Besides, this topic is about flywheels!

    It is very likely that the 4A92 flywheel would be compatible. Also remotely possible that it's not. The Mirage 3-cylinder was very explicitly designed for light weight and economy. Since the crankshaft is unique to this engine, it's possible that it uses a smaller bolt circle, possibly fewer bolts (photos indicate that it's 6-bolt), smaller bolts, etc. Anything to add to its lightness without reducing its reliability or adding excessive cost.

    And it's also possible that, unless the 4A92 fits the same transmission/bell housing, the starter ring gear could be different. But, both being small Mitsu cars... it's possible that there's some standardization. Most manufacturers like to stick with standards.

    So, unless someone else has already done it, I'd need to get my hands on a 3A92 flywheel, and a 4A92 flywheel... and compare them. Unless they happen to be the exact same part number, which they probably aren't.

    I'm hoping I won't have to spend a bunch of money to get somewhere with this idea. But, I'm feeling like I might have to.

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    Still Plays With Cars Loren's Avatar
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    Bah.

    When parts catalogs fail (no photos of flywheels in the Mitsu online sources), eBay is quite often a good source for visual and cross-reference info. Not 100% reliable, of course, but a good starting point.

    Flywheels can be disturbingly hard to find on eBay. But, flex plates are common. And the crankshaft bolt pattern will be the same, so we can look at that.

    So, poking around, it looks like all of the 2002+ Lancer flywheels are 7-bolt.

    The Mirage is definitely 6-bolt.

    There are some early Eclipses that had 6-bolt flywheels that could possibly be compatible.

    Of course, the bolt pattern could be redrilled by a good machine shop. Easier if it matches, but not impossible if it doesn't. More critical is probably the ring gear. Needs to be the same diameter and number of teeth. Only way I can think of to verify that would be to lay hands on it and measure, unfortunately.

    Well, this is interesting:
    http://www.ringgear.co.nz/Our_Products.shtml

    Not useful in this case, but interesting. If we can find a reference that lists more Mitsu products, and NEWER cars...

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    Im wondering about this, too. I hate how the rpm hangs on shifts and takes ages to come back down..
    2018 mirage ES manual

        __________________________________________

        click to view fuel log View my fuel log 2018 Mirage Es 1.2 manual: 41.6 mpg (US) ... 17.7 km/L ... 5.7 L/100 km ... 50.0 mpg (Imp)


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    Moderator Eggman's Avatar
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    Quote Originally Posted by Timinator View Post
    I hate how the rpm hangs on shifts and takes ages to come back down..
    This may be due to emissions.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 50.1 mpg (US) ... 21.3 km/L ... 4.7 L/100 km ... 60.2 mpg (Imp)


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    Moderator inuvik's Avatar
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    Quote Originally Posted by Eggman View Post
    This may be due to emissions.
    That was my thought also.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.6 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.7 mpg (Imp)


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    Senior Member stevedmc's Avatar
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    Sorry about the dumb question but what is the point of a lightweight flywheel? Are you trying to save weight, or does this affect shifting somehow?

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    Light weight flywheel helps the rpms go up and down faster, less rotational mass for the motor to get spinning


    2018 mirage ES manual

        __________________________________________

        click to view fuel log View my fuel log 2018 Mirage Es 1.2 manual: 41.6 mpg (US) ... 17.7 km/L ... 5.7 L/100 km ... 50.0 mpg (Imp)


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