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CR -- how high is too high for pump?

Discussion in 'General Tech and Maintenance' started by daveholiday, Sep 23, 2007.

  1. daveholiday

    daveholiday Do work

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    First off, does anyone have a super reliable compression calculator? I used one that I found on the internet, it actually may have been on here, said with an a6 block and a y8 head, my compression would be at 10.3:1. However, I was doing a little research and there is a guy who did the a6/y8, and got a CR of around 11.1. Anyway, my main question is how high is too high for pump gas? I've started running premium on just my stock a6, just to do it, because of all the stuff it supposedly burns cleaner and all that other junk, and just decided to start running it so that's no problem, I just don't know how high is too high? Honestly, I don't know much about compression anyway, or how increased compression adds power, I just know that having a super high compression with poor octane gas is bad, and you'll blow your motor.


    Also, this is a little off the main subject, but what are suggestions as far as tuning the fuel and whatknot for the minime? That's another thing that I don't know too much about, like how lean is too lean before it gets dangerous? I mean hell, with even an aftermarket intake, unless you tune it with that you're running lean.

    Thanks guys.
     
  2. scottp11

    scottp11 The Seniorest Member....

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  3. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    How high you can go with your static compression is all dependant on your tuning skills and your head setup. I ran 13:1 on 93 octane pump gas, but that was with a LOT of tuning. With aggressive cams it's easier.
     
  4. daveholiday

    daveholiday Do work

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    I ended up with 10.3 again? a6 block, y8 head, a6 pistons, y8 head gasket, a6 piston to deck height


    and I guess I'm ending up in the low 10's as far as my compression. I planned for this, at least for the time being, to be run on a stock y8 head, pretty much just pulled off, cleaned, put back together, and put on. Would there be as much tuning involved with this? Honestly, the only reason I ask is because I don't know too much about tuning. My brother has a 91 dx with a nice ls/v in, and he has an Apexi vafc 2 I think? and I think that with those you can adjust your air fuel ratio, i'd ask him but he bought the car as is, but I mean his compression is I believe in the high 12's and he runs 93. As far as either of us know, his computer isn't chipped or anything, but then again, like I said, I don't know much about tuning. More or less the only thing I know about doing this as far as modifications is that I need an adjustable cam gear to advance the timing 4.5 degrees because of the y8 head being slightly higher, and I need a d15b7 timing belt.
     
  5. scottp11

    scottp11 The Seniorest Member....

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    Dude, 10.3:1 is fine... My B16 has a stock CR of 10.4:1 and I run 91 octane....

    Also, you can't tune an engine with an Apex-i VAFC 2....
     
  6. K2e2vin

    K2e2vin Senior Member

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    The most accurate calculator was the Zealautowerks; but it's gone. There's a backup of the D-series part on some Russian server.
     
  7. daveholiday

    daveholiday Do work

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    is 10.3:1 fine without any tuning? also, I guess for some reason, I thought you could tune your air/fuel stuff within it, I guess I was wrong. I actually don't know where I even got that idea, but yeah.


    I'm really glad you said that, I remember getting that from someone in the past, (it may have been you actually, its on some russian server) and I remember now that I had it bookmarked.

    Êàëüêóëÿòîð êîìïðåññèè äëÿ D-ñåðèè ìîòîðîâ
     
  8. rosalien12

    rosalien12 Banned

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    I think zealautowerks is not the most accurate calculator
     
  9. K2e2vin

    K2e2vin Senior Member

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    Nice rebuttal; that comment swayed a lot of people. :rolleyes:

    That calculator(Zealautowerks), as far as I know and concerning D-series, was the only one that updated information so it was correct and takes into account as much variables as it can. This was discussed plenty of times on D-series.org.
     
  10. daveholiday

    daveholiday Do work

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    what would you say is the most accurate then? I don't mind you saying its not the most accurate, but if its not, then what do you use or whats more accurate?
     
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