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Thread: Piston design idea - Possible? Bad Idea? Or already been done?

  1. #1
    SC14'd Member Domestic Engineer nick.parker's Avatar
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    Default Piston design idea - Possible? Bad Idea? Or already been done?

    I have occasionally wondered if it would be possible to use a 'bearing system' (like the top shell of a camshaft bearing in the 4AGE) on a piston.

    The piston pin would not install from the side anymore - and one bearing would install on each end of the pin - with the con-rod in the middle.

    The idea being that you wouldn't have to worry about the pin intersecting the piston rings anymore (and hence having to be below the top two rings). This would be useful where you want to have the smallest possible compression height - probably because you are making a stroker setup and wanting to fit longest rod possible! The bearings would attach to the piston with fasteners.

    Does anyone know of somebody who has done this?

    Nick.
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  2. #2
    Junior Member Grease Monkey
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    In the camshaft (and crank) the clamshell part is not actually moving, just supporting the moving part. In your idea, it becomes reciprocating weight and that would be detrimental. Otherwise it seems posible, but you'd need fully custom pistons and I'm not really seeing the benefits.

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    Junior Member Too Much Toyota dnegative's Avatar
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    Aside from moving the fulcrum further up the piston its all negatives

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    anti blasphemy ! Carport Converter
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    -deleted comment-
    mind was some where else, and totally read you question wrong haha.
    Last edited by fixeruperer; 04-09-2012 at 09:56 PM.
    i dont have a funny or cool signature.

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    anti blasphemy ! Carport Converter
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    what stroke/rod ratio do you get when stroking the 4age ?
    i dont have a funny or cool signature.

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    SC14'd Member Domestic Engineer nick.parker's Avatar
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    Quote Originally Posted by fixeruperer View Post
    what stroke/rod ratio do you get when stroking the 4age ?
    Depends how much you increase stroke, and how much you can move the piston pin up in order to increase the rod length.

    Decreasing the small end (pin diameter) which is generally a bad thing, can also allow the rod to get a tiny bit longer too.

    eg: Go to 83mm (+6mm) stroke on a 4a, increase piston pin height 3mm, so you can use stock rods, now RS = 122m/83mm = 1.47,
    which is a bad rod stroke ratio - well bad if you care about the engine lasting 200,000km and revving as smoothly at higher revs (> 6500) as the stock engine did....

    Nick.
    == 4AGZE SC14 Supercharged ==
    Now flogg'n the SC14 @ 18psi....

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    Forum Sponsor Domestic Engineer Bazda's Avatar
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    Quote Originally Posted by nick.parker View Post
    Depends how much you increase stroke, and how much you can move the piston pin up in order to increase the rod length.

    Decreasing the small end (pin diameter) which is generally a bad thing, can also allow the rod to get a tiny bit longer too.

    eg: Go to 83mm (+6mm) stroke on a 4a, increase piston pin height 3mm, so you can use stock rods, now RS = 122m/83mm = 1.47,
    which is a bad rod stroke ratio - well bad if you care about the engine lasting 200,000km and revving as smoothly at higher revs (> 6500) as the stock engine did....

    Nick.
    Not ideal Nick lol.

    When you see our pistons and how much we are moving the gudgen up you will drool.
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    SC14'd Member Domestic Engineer nick.parker's Avatar
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    Cool Re: Piston design idea - Possible? Bad Idea? Or already been done?

    Yes Bazda - looking forward to that !
    == 4AGZE SC14 Supercharged ==
    Now flogg'n the SC14 @ 18psi....

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    Junior Member Backyard Mechanic J-M kujala's Avatar
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    123 rod lenght and 86.6mm stroke in a Pushrod T engine (N/A). rev limiter is 7200-7500 rpm.

    No problemos... I have near 200 laps with full throttle in a racing circuit where usually ~ 10 laps at each time. (lap times usually ~1.30+)
    and 50+ drag passes. car goes usually ~14.3 .

    And have been done couple of road trips from Finland through sweden to a Denmark. Totally like 3000-4000 km each trip.. + couple year full daily. So i dont see
    Any problems.... At short rod. But a littler longer if easily possible.
    And piston + rod had to be good quality ones.
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    Junior Member Backyard Mechanic J-M kujala's Avatar
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    Lower piston than 23mm start to be a problem also, half of piston pin, then rod thicknes, + clearance to piston + piston head thicknes..

    Also can be used like 3mm steel HG and drive piston 2mm over the block, what im doing in my engine.
    - Celica TA-22 -74 2T-G Turbo
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    SC14'd Member Domestic Engineer nick.parker's Avatar
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    Ok. Although you haven't done huge kms they have been tough kms - and you proved it can work. Thanks for the real world feedback.

    Consider the manufacturers who run their engines at a constant 6500 rpm for 200 hours and expect to see almost no wear _THAT_ is endurance.

    For a list of rod stroke ratio's :: http://users.erols.com/srweiss/tablersn.htm

    The lowest RS ratio Honda motors (2.2L 4 banger) get down to 1.46 : 1, I'd guess this is close to or about the lowest around for any OEM 4-cylinder.

    Based on these figures, it seems to that if you want a 7500+ rpm redline engine to last reasonable well then don't go below 1.6 : 1 (1.6:1 R/S approx = 4AG(Z)E, 3SG(T)E, 2ZZ etc).
    == 4AGZE SC14 Supercharged ==
    Now flogg'n the SC14 @ 18psi....

  12. #12
    Junior Member Backyard Mechanic J-M kujala's Avatar
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    Default Re: Piston design idea - Possible? Bad Idea? Or already been done?

    Yeap 1.6-1.8. Is a good area to play.

    I have open once my engine and no wear issue at anywhere. I will expect at least 50 000 km + without wear issue. Or measurable wear what means anything. But forged pistons in stock engine will wear faster than stock ones. bcz big clearance.
    - Celica TA-22 -74 2T-G Turbo
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