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D Series Cr

Discussion in 'Engine Building' started by CRX_Si, Mar 14, 2003.

  1. CRX_Si

    CRX_Si Senior Member

    i want to raise the compression ratio on my 91 crx si (d16a6) i figure if i put a d16y8 head gasket on it i can raise the CR but by how much? and what about pistons? i would prefer to go with honda OEM pistons because of the availability and price. and how high is too high? my motor has 135000mi but has no problems whatsoever. thanks in advance
  2. randerson165

    randerson165 Senior Member

    I think you can throw ZC pistons in there. You might check with somebody other than me to verify. I have a D16Y8 and just put ZC pistons in mine !!! There great.
  3. CRX_Si

    CRX_Si Senior Member

    anyone else know? and i heard zc pistons need machining to fit in a d series block is this true? and i also heard that zc pistons are hard to find but i guess i would just need to search for the integra pistons cause they are the same right? thanks
  4. randerson165

    randerson165 Senior Member

    Yes, they are acura pistons. You can get them from acura, call around, they will have non advertised deals at different times, just depends whats in stock. I bought a full bearing setup will all the motor bearings for like $52.00, I bought 5 and sold the rest !!! Just call around.
  5. phunky.buddha

    phunky.buddha Admin with a big stick Admin

    They're not necessarily the same piston... the Acura D16 DOHC pistons have a higher compression height but a lower volume dome, while the ZC has a lower compression height and a taller dome. They're not the same.

    86-87 D16A1 pistons (PG6B) = 1.181 inch compression height, 1.5cc dome volume
    88-89 D16A1 pistons (P29) = 1.141 inch compression height, 7.2cc dome volume
    88-91 ZC pistons (PM7) = 1.141 inch compression height, 7.2cc dome volume

    Make sure you get the P29 pistons if you're buying at the Acura dealership. They'll get you the same compression as the ZC pistons.

    You won't need machining (except maybe a hone job or bore if you're taking it .5mm larger) to get the pistons into your block. The psitons diameter is the same as your stock setup... unless you buy the OEM oversize pistons. The ZC pistons in the D16Y8 will give you about 12.8:1 compression, if I remember correctly.
  6. eludingu

    eludingu Junior Member

    thanks i think i will talk to acura and see what they have to say. which pistons would you recomend? i want to use a d16y8 head gasket to get more compression as well, with this head gasket which pistons would be the best without getting dangerously high CR? thanks alot
  7. CRX_Si

    CRX_Si Senior Member

    sorry that last post was on my friends name on this board cause i was at his house sorry for any confusion.
  8. S13Less

    S13Less Member

    i recommend doing a mini me. swap your cylinder head to a d16y8. using the d16y8 head gasket and head, you'll get a compression ratio of 10.33:1 and if you mill the head 0.020" the compression ratio will go up to 10.85:1. I did it without milling the head. I also use the d16y8 intake manifold with is match-ported to a b18b throttle body which is 60mm - 5mm bigger than the d16a6 throttle body. I also use an rpm-switch from MSD to activate the vtec at 4500rpm. lastly, i use a d16z6 fuel pressure regulator, and my ignition timing is at 15 degrees BTDC [i'm also using premium gas].

    swapping the head is a lot easier than swapping pistons. also this way you can get the added benefit of VTEC.
  9. CRX_Si

    CRX_Si Senior Member

    i have considered the mini me swap with a d16z6 head and y8 manifold but you are using the y8 for both? how does it work out? i dont want to mill the head b/c i dont know anyone who does good headwork. where did you get your cylinder head and IM? i think i am gonna use the ecu from the engine i take the cylinder head from and run a wire for VTEC, thanks.
  10. Jeef

    Jeef NO MA'AM Moderator

    What is a ball park hp gain for going up to 12.8:1 compression on a block with a stock top end?
  11. solblu

    solblu Senior Member

    Calesta do you have the total height, compression height and dome height of the PM6 pistons.
    and the total height and dome height of the PG6B, P29 & PM7 pistons

  12. dakinebrudda

    dakinebrudda Junior Member

    jeff i think 12.8:1 is a little high for an otherwise stock motor. you will have to run the best gas at all times and retard ignition timing to avoid detonation. also overheating in traffic may become a concern. also depending on valve-piston clearance, floating a valve at high rpm may result in piston-valve contact.

    i would try to stay under 10.6:1 for an every day street car personally. good luck
  13. phunky.buddha

    phunky.buddha Admin with a big stick Admin

    PM6 is the D16A6 (88-91 Si) piston... has:

    Compression height = 1.161"
    Piston to deck clearance = 0.020"
    Dome volume = -3.4cc

    In the Si head (38.0cc chamber) it yields 9.1:1 compression.

    These numbers are just references that I have lying around... they might not be 100% accurate, but I believe that they are. The other 3 pistons are listed earlier in the thread.
  14. phunky.buddha

    phunky.buddha Admin with a big stick Admin

    12.8:1 might be a little high for a stock engine, but think of this- a USDM Integra Type-R engine pushes 11.0:1 stock, and the new USDM Celica GT-S pushes 11.5:1 compression stock. Both have to run on 91 octane gas, and have to leave a margin of error for bad gas and variances in air quality, driver stupidity, etc... with more precise tuning and a watchful eye on maintenance, I don't see why you couldn't run 12.5:1 or even 12.8:1 compression on premium pump gas. I ran 12.6:1 compression on 93 octane gas with only aftermarket pistons and rods in my last setup, and it ran just fine. An extra 0.2 probably wouldn't have made any difference...
  15. solblu

    solblu Senior Member

    thanks for the help

    If you could look at my calculator. I need the specs missing in the chart on the right and a few for pistons that say enter volume in the Pistons section. any more help is greatly appreciated.


    is the link for my compression calculator.
  16. phunky.buddha

    phunky.buddha Admin with a big stick Admin

    There's nothing there... 404 error.
  17. solblu

    solblu Senior Member

  18. d16y8_93_civic_lx

    d16y8_93_civic_lx Junior Member

    so your saying if i put pistons from a d16a1 into my d16y8 using my curent connecting rods it will give me a 12.8:1 CR?? a d16a1 is the stock motor out of a 89 integra "USA version" right?? and if my math is correct that will take me from the stock 127 hp to 173 hp "give or take" what other preperations should i make for this if any... and why would putting those pistions into my motor raise the CR that much when they both have around 9:1 stock CR?
  19. sohcslammer

    sohcslammer Senior Member


    And if my math is correct......... you're out of your fucking mind :lol:

    Edit - I just gotta fucking know.... what math formula is that exactly? :D
  20. d16y8_93_civic_lx

    d16y8_93_civic_lx Junior Member

    simply take your current hp divide it by the current CR. that will give you the hp per CR. multiply that by the new CR to get the new hp give or take 10 hp. dont know if it works on hondas and such but i was 8 hp off when i put 10.5:1 CR pistons in my 350 based off of its previous CR and HP.

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