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Thread: My Turbo 3A92 Project

  1. #1
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    My Turbo 3A92 Project

    I wanted to compile one thread with all my turbo build info in one area since thereís not much info at all regarding the 3A93 and forced induction.

    I may be repeating info for some of you but for all others, Iíve taken a 2015 3A92 with 25k miles on it and transplanted it into a 1000lb dune buggy. I was running an AMR500 on this setup briefly but itís been removed to make way for an Audi A2 turbo. The turbo is essentially a GT1544 with a 37.8mm compressor inducer.

    Head work is being done as we speak. Currently running 300cc injectors and stock pump. We donít know at this point if the stock pump is up to the task of 10psi. My estimates are that I wonít need much more (if any) over 100LPH so stock pump might be good for the 130hp ďishĒ iím aiming for.

    Concerns so far are that I have no way to improve on the camshaft M cams from thailand are not available anymore and will not be made again. This leaves only the option of grinding the stocker and sourcing expensive buckets or using Web Cam, which will charge about a grand to weld and bring the stock cam.

    Valves and springs are a major concern as they appear to be very weak based on others experiences. I do not have my head and valves to measure them but I may have some custom valves made, or stick with stock valves and attempt some stiffer springs at the very minimum.

    As much as if love to squeeze 150hp from the OEM internals iím pretty well convinced the conrods will not sustain those kind of pressures. If I can get a steady 10psi and somewhere in the 130-135hp at the crank range I will consider it a huge success.

    Anyone with info on this engine to contribute itís greatly appreciated! Iíll keep you guys posted on the progress as the build comes together



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    Still Plays With Cars Loren's Avatar
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    So, are you running the stock fuel pump? Because stock fuel tank? I'd expect some kind of fuel cell in an off-road vehicle. What's the story?
    Simplify and add lightness.

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    Iíve got the stock fuel pump in a custom fuel cell. Going give it a try as is before a fit a larger pump

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    Thought you guys would like some pics!

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    Attached Images Attached Images  

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    Administrator Daox's Avatar
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    Very cool project! What made you go with the 3A92 vs the plethora of other options?
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

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        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


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    Size and weight mainly. Lightest production engine available, perfect for a light duty off road buggy. Huge availability on used engines ($500) replacement cost. If the 3A92 can handle 10psi reliability, the power to weight in a light off road project like this outperforms anything available from large manufactures like polaris/canam for a fraction of the cost

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    Hey guys wanted to update yíall with the most current info I have on the 3a92 boost project.

    As for upgrading the camshaft itís a no go. The guy who was making the cams for the 3a92 (Thailand) is not longer making them so no cams are available to my knowledge. The only other alternative is to have ďwebcamĒ in CA weld the lobes and put a new grind into it, which will run ya $1000. For me, going low boost the extra 1.5mm or so of lift Iíd get just wasnít worth the cost to have the cam welded and ground.

    Head bolts are wimpy and if going to a head stud its difficult to find any long enough to fit, my machine shop couldnít source any. The alternative would be to have a larger thread cut into the block. I will not be going this route myself as Iím trying to keep the engine in one piece minus the head. I will likely use the original head bolts with an extra 5-10lbs on them 😬

    Port/polish work is coming along and should offer a flow increase over stock. I donít know how great of an improvement this is going to make with the stock cam but I welcome any small improvements in flow.

    Valve springs are a major concern. The stock valve spring pressures were measured as 25lbs on the seat and 50lbs open. My shop found some springs that will work from a nissan which measure 50lbs seated and 75lb open which we will be swapping out. Thatís about it for now but should have the head back next week and iíll start the reassembly and building the turbo manifold soon!

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    Senior Member Wallythacker's Avatar
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    I look forward to the final incantation of the build. I remember valve springs of 175lbs. or more open back in the detroit iron era. I think a friend had 250lb. springs in an 454 LS6. These modern engines never cease to amaze me.

    I would love to turbo my 2nd Mirage but I'm still recovering from a busted hip and need to undergo a hand and foot reconstruction.

    Some advice to everyone here. Don't age if you can avoid it. It sucks.
    Zero, 2014 ES Plus 5MT, written off but not forgotten.
    Zero II, 2014 SE, 5MT, climate She's HOME now!
    Shelby AKA "Cute", 2017 ES 5MT, A/C.

    Mirage owners look at the world differently than everyone else, but in a better way
    We're driving the Beetle of the 21st century, the greatest small car now available!

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        click to view fuel log View my fuel log 2017 Mirage ES PLus 1.2 manual: 39.0 mpg (US) ... 16.6 km/L ... 6.0 L/100 km ... 46.8 mpg (Imp)


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  15. #9
    Hip, hand AND foot!? Did you get hit by a car?

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        click to view fuel log View my fuel log 2014 Mirage SE 1.2 manual: 66.3 mpg (US) ... 28.2 km/L ... 3.5 L/100 km ... 79.6 mpg (Imp)


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    Senior Member Wallythacker's Avatar
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    Quote Originally Posted by MetroMPG View Post
    Hip, hand AND foot!? Did you get hit by a car?
    TBH, I wish it was a car accident. The odds of having everything fixed by now would have been better. As they're discrete incidents I'm getting the health care shuffle. Covid has slowed things down to a crawl. Odd/horrible/ironic thing is the health care system caused 2 of the 3 things I mentioned.


    Zero, 2014 ES Plus 5MT, written off but not forgotten.
    Zero II, 2014 SE, 5MT, climate She's HOME now!
    Shelby AKA "Cute", 2017 ES 5MT, A/C.

    Mirage owners look at the world differently than everyone else, but in a better way
    We're driving the Beetle of the 21st century, the greatest small car now available!

        __________________________________________

        click to view fuel log View my fuel log 2017 Mirage ES PLus 1.2 manual: 39.0 mpg (US) ... 16.6 km/L ... 6.0 L/100 km ... 46.8 mpg (Imp)


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