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Thread: Turbo suggestions?

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    Turbo suggestions?

    Okay, so the whole roots style amr500 works but has some definite flaws... Iíve decided if I want reliable boot itís going to need to be a turbo. Really not much available for high quality turbos on 1.2L. Anyone recommend a brand that has something small and high quality?



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    Still Plays With Cars Loren's Avatar
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    Just like where the AMR500 came from, I'd be looking to the Japanese market. Europe, too.

    Here in the US, there are a couple of small-displacement turbo cars. The 1.0 Fiesta turbo comes to mind. But, as you know, we're not big on "small" here in the US.

    Motorcycles might be another possibility.

    There are a fair number of 1.4 liter turbo engines around that might have a small enough turbo. Fiat/Chrysler has a 1.4 turbo. Pretty sure GM has one, as well.
    Simplify and add lightness.

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    Smart used a turbocharged Mitsubishi engine similar to the 3A92.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.8 mpg (US) ... 21.2 km/L ... 4.7 L/100 km ... 59.8 mpg (Imp)


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    Senior Member ahausheer's Avatar
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    Quote Originally Posted by DirtGearTv View Post
    Okay, so the whole roots style amr500 works but has some definite flaws... Iíve decided if I want reliable boot itís going to need to be a turbo. Really not much available for high quality turbos on 1.2L. Anyone recommend a brand that has something small and high quality?
    Couple videos on youtube of guys turboing these things, most in Thailand. One guy supposedly was on stock internals and made 175hp. But I suspect something was lost in translation because that amount of power sounds way to high.

    You might reach out to the various turbo mirage videos, some of the posters are responsive.

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    Quote Originally Posted by ahausheer View Post
    Couple videos on youtube of guys turboing these things, most in Thailand. One guy supposedly was on stock internals and made 175hp. But I suspect something was lost in translation because that amount of power sounds way to high.

    You might reach out to the various turbo mirage videos, some of the posters are responsive.
    Iíve looked and have not found this video or any from thailand really... So iím actually using an Audi A2 turbo thatís suppose to be good for up to 200hp. Iím in the process of having head work and cam done. Iím shooting for 150hp on this setup with stock internals. Iíd very VERY relieved to see a 175hp setup in tact 😂

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    Still Plays With Cars Loren's Avatar
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    Stronger valve springs?
    Simplify and add lightness.

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    Quote Originally Posted by Loren View Post
    Stronger valve springs?
    Iíd love to, not sure what going to fit if anyone has suggestions

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    Still Plays With Cars Loren's Avatar
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    I'm definitely not an expert in that area, but I'm sure there are options.

    I just know that all it took was a very brief over-rev to get all of the exhaust valves in this engine to float right into the pistons. I would think that if you get to where you're spinning the engine up very quickly, with great gusto... you could probably do the same thing.

    The valves are TINY spindly little things. The valve springs can be compressed by hand... even with my wimpy hand. It's designed to rev to 6500, maybe 7500 rpm, but it's also designed to be as efficient as possible. Valve springs that even the slightest bit stiffer than absolutely necessary would create unwanted friction losses and reduce efficiency. That's how the car was designed.

    This might be an interesting read with a couple good engine internal photos:
    http://drivefast.org/forum/viewtopic...t=3386&p=60234
    (it's where we took out my busted engine to replace it)

    If you're doing head work... and going turbo where you don't need/want so much static compression (what's this engine, like 10.5:1?), maybe some custom pistons to lower the compression AND make it non-interference?

    Or... keeping with the theme of "stock internals", maybe a custom thicker head gasket (don't they make those out of copper or something?) to accomplish the same thing? Not sure if there's enough tolerance in the timing chain to allow for that.

    Ooooh... the 3A90, 3A91, and 3A92 all have the same 75mm bore. You could probably fit a 3A90 or 91 crankshaft to destroke the engine a little bit. Less compression, less piston height.

    I'm definitely not an engine engineer. I don't even play one on TV. Just thinking out loud.
    Simplify and add lightness.

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    Appreciate your feedback! Was actually just reading your thread about the overrev. I¬ím not surprised at the weak springs for Mpg sake. My soft limiter kicks in at.... 7400rpm I think... and i¬íve bounced off that plenty 😂😜

    I’m hoping the weak springs are not a forecast for weak rods. I think it might be more difficult for me to get the engine out of my Frankenbuggy than the Mirage, which is why the internals will stay stock. They are 10.5:1 but I intend to overcome the compression issue with E85

    The good news about this setup is what you already discovered. Pushing the 3a92 beyond its limits, at worst is only a $500 mistake

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    Still Plays With Cars Loren's Avatar
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    Yep, these engines are presently cheap and plentiful.

    I think that most modern drivetrain parts are overbuilt to the tune of 20-50%. I personally think 150hp is pretty optimistic for a Mirage engine. The DESIGN can probably handle it. But, as you noted... those rods are probably designed to be very light. No more mass than absolutely necessary. The stock 78hp plus 50% would be around 120hp. That "might" be a safer target.

    Also, especially when you go adding a bunch more boost... keep the revs down. I don't remember the math, but piston speeds (and thus the force on the pistons, rods and crankshaft every time the piston reverses direction) increase exponentially relative to RPM. Drop your rev limit to 6000-6200, enjoy the torques, and hopefully keep it alive a lot longer!

    I'm sure I'm not telling you anything you don't already know.


    Simplify and add lightness.

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