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Thread: 3A90 1.0L 3-cylinder Mirage / Space Star engine info (specs, specifications)

  1. #11
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    If the 1.2 has no EGR which eliminates the mixing of egr and pcv and the resulting tar like residue on the induction circuit, then I am sold on the 1.2, which with only pcv and no exhaust gases mixing is the much better choice in my opinion.

    regards
    mech


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        click to view fuel log View my fuel log 2015 Mirage de 1.2 manual: 55.7 mpg (US) ... 23.7 km/L ... 4.2 L/100 km ... 66.9 mpg (Imp)


  2. #12
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    The idea behind cold re-circulation EGR is that adding exhaust gasses allows to run lean mix ratios without generating too much NOx. Agree on EGR being long term liability, common problem on many cars like Mazdas, Priuses, etc.

    I think the reason 1.2 has lower compression ratio is b/c is it optimized for Regular 87 gasoline (91 RON) which is cheaper.

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        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 46.4 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.7 mpg (Imp)


  3. #13
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    Added 25Plus' dyno chart comparison of the 3A90 and 3A92.

    More info here:
    Driving performance diagrams

    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)


  4. #14
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    Quote Originally Posted by cyclopathic View Post
    The idea behind cold re-circulation EGR is that adding exhaust gasses allows to run lean mix ratios without generating too much NOx. Agree on EGR being long term liability, common problem on many cars like Mazdas, Priuses, etc.

    I think the reason 1.2 has lower compression ratio is b/c is it optimized for Regular 87 gasoline (91 RON) which is cheaper.
    Lower compression, jesus christ it is not a diesel engine. it has compression ration 11:1 which is a lot for an otto-engine. only mazda and their skyactiv has 15:1 ratio. otherwise it is normal to have 10:1 or below

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        click to view fuel log View my fuel log 2015 Mirage Intense 1.2 manual: 47.9 mpg (US) ... 20.4 km/L ... 4.9 L/100 km ... 57.6 mpg (Imp)


  5. #15
    Senior Member 25Plus's Avatar
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    10:1 was normal 10 years ago for cheap cars with low specific power output.

    Today, 10:1 is a normal compression ratio for turbos, 11:1-12:1 is normal for naturally aspirated engines and high performance naturally aspirated engines or enginges that work with atkinson cycle have compression ratios of 12,5:1-13.5 :1.

    Mazda has compression ratios of 14:1 maximum for both gasoline and diesel engines with Skyactive technology.
    Mitsubishi Space Star 1.2:
    Daihatsu Cuore L251:

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        click to view fuel log View my fuel log 2015 Space Star Klassik Kollektion+ 1.2 manual: 67.5 mpg (US) ... 28.7 km/L ... 3.5 L/100 km ... 81.0 mpg (Imp)


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    it is true but read something about 15:1 long time ago but it is 14:1

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        click to view fuel log View my fuel log 2015 Mirage Intense 1.2 manual: 47.9 mpg (US) ... 20.4 km/L ... 4.9 L/100 km ... 57.6 mpg (Imp)


  7. #17
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    Here are two pix of my 3A90 1.0L engine, with the air filter box removed for a better view. The MAF-sensor is also removed, as it is located on the removed air filter box.

    Compare these with the Mitsubishi drawings in the first post, the EGR section seems to be missing.

    Maybe someone wants to put these pix into the first post.

    Name:  3A90 engine from left.jpg
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    Name:  3A90 engine from right.jpg
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Size:  89.0 KB



    EDIT: The 1.0L 3A90 with AS&G has EGR, the same engine without EGR has no AS&G
    Last edited by foama; 11-01-2021 at 08:55 AM.

  8. #18
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    Quote Originally Posted by 25Plus View Post
    10:1 was normal 10 years ago for cheap cars with low specific power output.

    Today, 10:1 is a normal compression ratio for turbos, 11:1-12:1 is normal for naturally aspirated engines and high performance naturally aspirated engines or enginges that work with atkinson cycle have compression ratios of 12,5:1-13.5 :1.

    Mazda has compression ratios of 14:1 maximum for both gasoline and diesel engines with Skyactive technology.
    Since US gasoline has lower octane rating (87 R+M vs 95 R in EU) many manufacturers reduce compression ratio for US market.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 46.4 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.7 mpg (Imp)


  9. #19
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    I wonder if the higher compression ratio in the 3A90 is from the pistons, would be great if somebody could check it out. I'll try to get up on lunch break and go buy some measurement tools, give you guys some accurate specs and finally pictures of the 3A92 at least...



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