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Thread: Wakarimasen

  1. #101
    Veteran bigm's Avatar
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    Fine work there chap!


    nothing but the best here!

  • #102
    Site Supporter Low Style's Avatar
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    so clean!!!! i must come around soon

  • #103
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    Love the precision and caution taken in the engine assembley!

  • #104
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    Thanks for the kind words guys, i will have another epic post tomorrow - today was a good day,
    4AGE & 7AGE Forged Connecting Rods - Lightweight Flywheels - And Much More



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  • #105
    Veteran johl's Avatar
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    Show me the moneeyyyyyyyyyyyyyyyyy!!!!!!!!
    stroked 2L ca18-ae86 in the build...eta xmas 2012?

  • #106
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    Yes, i can do that




    Okay, this is another epic post that will be boring as batshit to most of you. This basically details how to (affordably) measure the compression ratio on ANY motor, if you didn't know ANY of the details (unknown pistons/headgasket/how much the head and block have been shaved/port work done). I know some of you will look at the post and go 'fffffffuuuuuuuuuuuuuuuuuuuuuuu', but if you follow it step by step and stay cool, ANY of you can do it. If you can borrow someone's dial indicator and stand, this job will cost you around $10, and a good few hours of your life.

    Okay, the tools you will need for this particular job are:
    -Two blocks of wood, the same width (or as they are pictured, the same "height").
    -An accurate syringe or burette - i have used both, and this little 20ml/cc syringe is far easier to use, and still very accurate. Buy off ebay for $3.
    -Dial indicator + stand
    -A flat, transparent surface with a small hole drilled near the centre. - i used a CD case (be careful, as most cd cases have a small lip around the outside edge - this is not suitable - i chopped them off).
    -A cup of water, dyed any colour.
    -And a container of vaseline (there's no way to say vaseline without sounding suss).



    Prop the head up on the two pieces of wood - do it on a nice flat surface - stupidly expensive granite table? Yep, that'll do.



    We're going to start by measuring the combustion chamber of cylinder number 1. You need to do this to each of the chambers - not only will this help us work out the compression ratio of the motor, but you can also check that you have removed the same amount of material from each chamber when you ported it.



    Now, get some of your trusty vaseline, and coat the valve where it will touch the valve seat - use about this much, and spread it the whole way around the valve.



    Do this will all of the valves, and put them in. Make sure you remove ANY excess vaseline from the combustion chamber, as this will fudge your results.



    Spread some vaseline around the entire combustion chamber. Again, try not to use too much.



    Lay down your CD case/other, and give it a good press around to make it seal up with the vaseline - as you can see here, i used too much of the stuff, and vaseline has made its' way into the combustion chamber - not ideal.



    Fill up your burette/syringe with the coloured water - make sure there are NO bubbles, and make sure you have it on an exact measurement - here, it's 20ml/cc.



    ..and start filling. Record your measurements as often as possible - it's easy to lose track and forget things.



    My combustion chamber took almost exactly 2 lots of 20cc, making it a 40cc chamber. I repeated this with all 3 other chambers and got almost identical results - with robo's motor, i had a variation of almost 2cc between chambers and had to do some more grinding - it pays to check!












    Next step is measuring the headgasket. Make sure your dial indicator is aligned vertically/horizontally fairly well..



    And lower it so it is touching the table at least a bit (preload). It doesn't really matter how much, as long as it's touching. With it touching the table, reset the dial to 0.



    And slip the headgasket under it - measure the graphite part of the gasket, not the metal rings. My measurement was 0.06" (1.52mm). Also measure the bore of the headgasket (not pictured) - in my case, 82.5mm (stock BT headgasket).












    And the final step - measuring the block/pistons. The first step here is finding the true TDC of the motor (where the piston is at its' absolute highest position in the bore). Simply put the dial indicator a little bit down the bore (doesn't really matter how much)...



    ...and start turning the crank and watch the dial indicator at the same time - the measurement will go up and up .. and then almost all of a sudden start going back down. The point of transition is TDC.



    Now that we have TDC, we can measure the deck height of the piston. Deck height is simply the tiny distance from the deck of the piston (do not measure the dome of the piston if it is high-comp, and dont measure the dish of the piston i.e. GZE). The best place to measure, is usually around the edge of the piston, where it meets the cylinder wall.

    Zero out your gauge...



    ...and then move the gauge over to the block deck. The measurement shown on the gauge is the deck height. In my case, 0.019" (0.482mm).

    A very important thing to note here, is that the piston (especially while cold) will "rock" in the bore at TDC, meaning the measurements aren't always the same the entire way around the piston. Take a good 6-8 measurements around the piston, and average the result - i got something like 0.020/21/19/19/18/19/19 etc, and then averaged it out to 0.019".



    The final part of this equation is measuring the piston CC volume. I know this might confuse a few people - how the hell do i measure the CC of a piston that sticks out of the bore?!? If you see some TRD/wiseco high-comp pistons for a 16V, this would scare you even more. Well, there's a very very simple way to work it out.

    With your dial indicator back on the piston, zero it out again..

    ..then start moving the crank, and measure an exact distance down the cylinder. The amount you measure doesn't really matter (as long as it's exact, and you record it) - basically, as long as the very top of piston is below the top of the block. I chose 0.2" down.



    Now, without pushing on the piston too hard (or touching the crank, we don't want the piston to move!), you want to put vaseline around the edge of the piston, to form a seal. Again, same rules apply like the head - all leftover vaseline should be removed, so the results aren't fudged.



    With the vaseline cleaned out from in the bore, you want to the same thing again like with the head - vaseline around the edge.. not too much.



    Put your cd case/other on, and start filling..



    ..and once you're complete, record your measurement. Mine was 23cc.

    (please note, you can see a bit of the measuring liquid had leaked into where the cd case was - the seal was crappy because i was just trying to get a photo)



    Now, you're probably wondering where the easy bit of finding out the piston volume is, right?

    Well, in primary school maths, we learned a simple equation - volume of a cylinder. IF the piston in that bore was dead flat, then the volume that we just measured should be ::::::: Pi x r2 x h.

    In this case, that equals 3.1414 x 4.05 (half the bore size, in cm) x 4.05 x 0.508 = 26.176cm3, or 26.176cc

    So, if our measurement was actually 23cc, and if it were a flat piston it should be 26.176cc .. then you have a piston dome volume of 3.17cc. Easy!!!!





    Okay, now you have ALL your measurements, you can calculate your compression ratio.

    You need to work out three quick equations first.

    Cylinder volume (cc) = cylinder bore diameter (mm) 2 x stroke (mm) x 0.0007854

    = 81 x 81 x 85 x 0.0007854

    = Cylinder volume = 438.00cc


    Gasket volume (cc) = Gasket bore (mm) 2 x 0.0007854 x installed gasket thickness (mm)

    = 81 x 81 x 0.0007854 x 1.2

    (i have put the measurement of the gasket as 1.2mm, as it is believed that most graphite gaskets crush by 0.3mm when torqued up - metal headgaskets have no noticeable change in size)

    = Gasket volume = 6.18c


    Piston to deck volume (cc) = Bore (mm) 2 x 0.0007854 x piston to deck height (mm)

    = 81 x 81 x 0.0007854 x 0.482

    = Piston to deck volume = 2.483cc


    AND THE FINAL EQUATION!!

    Cylinder Volume (cc) + Combustion Chamber Volume (cc) + Gasket Volume (cc) + Piston-to-Deck Volume (cc) + Piston Dish Volume(cc), or - Dome negative Volume(cc)
    /
    Combustion Chamber Volume (cc) + Gasket Volume (cc) + Piston-to-Deck Volume (cc) + Piston Dish Volume (cc), or - Dome negative Volume (cc)

    =

    438 + 40 + 6.18 + 2.483 - 3.17
    /
    40 + 6.18 + 2.483 - 3.17

    = Static Compression Ratio = 10.627 : 1



    Thanks for reading, you've probably visibly aged if you read this from start to finish.
    4AGE & 7AGE Forged Connecting Rods - Lightweight Flywheels - And Much More



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  • #107
    Veteran blake.'s Avatar
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    Wow that's awesome. Pretty smart.
    Quote Originally Posted by Gunner View Post
    Id explain more but there people on here I dont like, and i want to see this shit on thsir supposedly awesome masterfully built but stock power making 20v
    bursting ovaries since 92'

  • #108
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    Good stuff mate, Although I would use a 6mm piece of Acrylic perspex next time will make life faaaaaaaaaaaaaaaaaaaar easier

  • #109
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    ^ I had one piece .. but it shattered into a million pieces when i drilled it I decided to go with the next available thing
    4AGE & 7AGE Forged Connecting Rods - Lightweight Flywheels - And Much More



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  • #110
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    my brain.... it hurts.... awesome write up tho. maybe sticky in tech threads?
    stroked 2L ca18-ae86 in the build...eta xmas 2012?

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