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Budget 10:1 Piston Option (interesting)

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    #1

    Budget 10:1 Piston Option (interesting)

    Ok, I'm going to post this before I forget or lose interest (mostly for the benefit of this wonderful forum...you can thank me in free performance parts or something. haha).

    Anyways, I can't go into all the nitty gritty, but a very fun OEM brand piston that could potentially be used in our motors is... ...

    The piston from the genesis coupe 2.0L turbo. (Theta II).
    while the block is losely based off the EVO engine, it is not the same (different rods etc.

    Here's the fun part.
    Comes stock in 86mm (requires a bore out for our engines).
    Very very similar compression height (30mm to our 30.5).
    22mm wrist pin (same as ours).
    only 2.5cc dish...that means, about a 10:1 compression ratio.
    also fun...this is a piston designed for a turbo engine and should definitely withstand a hell of a lot more abuse than our f22 pistons. Reading up on the genesis forums, they found the stock limit of their blocks to be around 350whp or so...but probably limited by the rods for them. For a well built cast piston (probably hypereutectic and coated), i'd say somewhere near there is close.

    Here's what needs to be resolved...
    The genesis uses a slightly narrower Small end on the rod...it's possible the piston may not clear our bigger ends...this could be resolved fairly easily by having the ends shaved down a touch. I don't have the numbers on hand, but the differences was very minor.

    Valve reliefs...No idea on this, but for stockish cams at least we really don't have a lot of lift to worry about. It's a 4 valve design...must be close, right?
    Claying would be a good idea.

    What's also fun is I believe the pistons are only like $35 each from a hyundai dealer!

    Ok, now take this information...and go. Take it, and go.

    let me know what your research leads you to. I wanted to get the word out to start the discussion. I was very psyched back in the day to try and make dsm pistons work (the cheap cast ones), and was dissappointed I couldn't...but this looks very promissing.

    Side note, would make for 11.x:1 in an f23 I believe (also would be fun).

    Who thinks 10:1 in a turbo engine is a bad idea?

    Ok, that is all.

    Mark
    (no longer a Cb7 owner, but a cd5 now...close enough, right?)
    Tags: None
    #2
    The most intriguing part of this option to me is the likely beefier ringlands for turbo cars. Honda has enough options bridging over F/H/K motors that if you can't put together something with 10.0:1 static compression, you're doing it wrong. Question: what about the 4G63 pistons was it that you couldn't make work? They've been done a few times before.
    My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

    Comment

      #3
      He stated that he tried using the stock cast pistons... Only the stroker pistons work

      Comment

        #4
        Boring would concern me... the piston strength increases, but the cylinder wall strength would decrease. Plus, how much would a set of Genesis pistons go for?

        With the work necessary to do this, I'd think the cost wouldn't be that much greater to do inexpensive forged internals on the stock bore. 300-350whp is about all you would really want on a daily driven FWD car anyway.

        Still, it's interesting information. Always good to see people are thinking outside the box!






        Comment

          #5
          He believes the pistons are $35 a piece from the dealer... If so it seems like a worthy thing to try

          Comment

            #6
            True... that'd be about half the price of the cheapest aftermarket forged pistons I could find. Depending on the cost of the machine work, it may end up being a cheaper alternative.






            Comment

              #7
              I think it would b a pretty decent powerhouse if the head was shaved and a full bisi top end and exhaust

              Comment

                #8
                Originally posted by deevergote View Post
                Boring would concern me... the piston strength increases, but the cylinder wall strength would decrease. Plus, how much would a set of Genesis pistons go for?

                With the work necessary to do this, I'd think the cost wouldn't be that much greater to do inexpensive forged internals on the stock bore. 300-350whp is about all you would really want on a daily driven FWD car anyway.

                Still, it's interesting information. Always good to see people are thinking outside the box!
                86mm is only going .040 over.
                I <3 G60.

                0.5mm Oversized Stainless valves and bronze guides available. Pm me please.

                Comment

                  #9
                  Originally posted by bigpoppa694lyfe View Post
                  He stated that he tried using the stock cast pistons... Only the stroker pistons work
                  True. I guess I just didn't pay any attention to him saying that and assumed that he was using the stroker pistons.

                  Originally posted by wed3k View Post
                  86mm is only going .040 over.
                  I don't think he was calling that extreme, just saying that it adds to the cost of these versus 85mm forged F22 pistons.
                  My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

                  Comment

                    #10
                    Ya, stroker pistons pretty much equal custom pistons price wise.

                    The main reason I look at this is to get a "reasonably" strong CAST piston. Why would anyone want a cast piston??? Well, longevity mainly. This sounds counter-intuitive, but in reality, provided you are working within a reasonable power level, the cast piston will ast longer. The main reason being tight piston-wall clearances. less skirt wear, less piston slap, etc.

                    I for one think around 250whp is about perfect for a daily driven street car. Decent traction, fun, turbo size equates to something that spools decently, can probably be done on stock rods, etc.

                    I'm only worried about being able to safely tune this setup. 10:1 and turbo isn't a very common setup. Many say it's fine (B16a, b18c, h22...all engines that get turbo'd often and can last provided they are tuned right). I do have access to 94 octane which is a bonus too.
                    Anyways, my engine build is slow and steady.
                    Acquired chiped ECU, ostrich emulator, injectors, spare f22b2 (for my cd5), transmission, turbo manifold, turbo, gasket kit, and more.
                    still need
                    F22a6 head/Intake manifold
                    exhaust pipes
                    head studs,
                    bearings
                    and more.

                    I think I may just have to try this though. I was going to go with F22a speed-pro hypereutectics (which i've had decent success with before (see 2-3 year old post, haha)), but i think this has to be done. $35 to clay a piston would be worth it in my opinion. Worst case scenario: pistons don't fit, out $35. Pistons do fit, complete build, too much pinging under boost...lower boost and live with a more snappy high compression F-series turbo (5-8 lbs predicted).

                    Anyways, I'm rambling now, but wanted to keep this alive and spur more discussion!

                    Regards
                    Mark

                    Comment

                      #11
                      That's true, you don't need all 4 pistons to test a theory. I am looking forward to this thread as I think it could be pretty exciting. I hope you are able to go through with this.
                      My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

                      Comment

                        #12
                        So has anybody done anymore research on this? Only thing I see missing that would make an impact on usability is wrist pin location... If it's too high on the piston u got a compression drop and too low then u might see valves and potentially head being destroyed. I'm about to start my rebuild within the next couple days and if this fits and bumps compression up then I'll take this route and save boost for next year.

                        Comment

                          #13
                          tuning 10:1 will not be a problem
                          we're not in 1998 no more
                          there are 11.7 compression s2000 making 700whp
                          Originally posted by deevergote
                          Just do what PR CB7 said.

                          "I'm Going For Wood" (Clickey Clickey)

                          Comment

                            #14
                            Originally posted by bigpoppa694lyfe View Post
                            So has anybody done anymore research on this? Only thing I see missing that would make an impact on usability is wrist pin location... If it's too high on the piston u got a compression drop and too low then u might see valves and potentially head being destroyed. I'm about to start my rebuild within the next couple days and if this fits and bumps compression up then I'll take this route and save boost for next year.
                            This "wrist pin location" you speak of is known as compression height. I mentioned it in my first post. It's the proper measure and I wouldn't have been able to calculate compression ratio without it. Again, main thing that needs to be checked is mostly valve reliefs, but I feel it won't be an issue (unless you are using an aftermarket cam).

                            Comment

                              #15
                              Originally posted by PR CB7 View Post
                              tuning 10:1 will not be a problem
                              we're not in 1998 no more
                              there are 11.7 compression s2000 making 700whp
                              I think i'll have to "Just do what PR CB7 said.".

                              Busy renovating a suite, rebuilding a datsun 260z with a skyline engine, and trying to fix up my other car to be sold (Gs400 needs motor mounts and front suspension). This isn't high on my list, but as discussed I wanted to make sure my research was not forgotten and wanted to start the discussion.
                              Saw some more pics of the pistons somewhere...nice coated skirt. Seems really promising.

                              Side note: Either the price of the piston went up or I was looking at the 3.8L ones, but these pistons are closer to $46 I think. Still budget oriented and have the tight clearance pro's I'm after.
                              Also need to find out ring sizes if I can buy aftermarket instead of the expensive hyundai rings ($160 i think?)

                              Mark

                              Comment

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