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High comp or low comp what is a girl to do??

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    #1

    High comp or low comp what is a girl to do??

    Hey guys I'm getting ready to drop pistons and rods in the f22b. I've always thought I would go with a low compression piston but I've heard recently that I might be able to go as high as 10.1 on this build. Now let me be the first to say I'm not looking for tons of power a respectable 300 hp would be great I really just want a safe ( well as safe as a turbo can be) yes I kno they aren't safe I've had the car turbo'd on the stock engine for yrs. The turbo I have on the car is an ar 70 w a 60 something trim. I'm wanting to run 13-15 psi. Can I get some pros and cons about running a low compression piston vs the high compression piston. Pretty please 
    Tags: None
    #2
    11:1 compression, Injector Dynamics 1000cc fuel injectors, Bosch 044 fuel pump, tuned on E85.

    SOHC Non-VTEC F-series for life

    "It is the fools prerogative to utter truths that no one else will speak."
    -Morpheus (The Sandman)

    Comment

      #3
      http://www.rbracing-rsr.com/compression.htm

      Running 13 pounds of boost on 10 to 1 compression will give you a compression ratio between 17.79:1 (13 pounds of boost at 5280 feet, if you live in the mountains) to 20.2:1 at 15 pounds at sea level. The car won't be very practical though, it can only be run with a really good engine management system because of the fact that E85 mixtures vary a lot (sometimes they may actually be E70 or E80 or whatever). Also I'm not sure if E85 is even good enough at that high of compression.

      Don't run 11:1 and turbo. If you run 11:1 like F22Turbo702 suggested you'll be running a minimum of 19.67:1 compression (13 lbs at 5280 ft) to 22.22:1 compression (15 lbs at 0 ft). I'm not sure if the block can survive that without Darton sleeves. Not to mention you'd need racing fuel.

      Comment

        #4
        Most of the turbo builds we've done in the last year have been between 10.2-11.5:1, all running E85, and either Hondata S300, AEM EMS, or HKS F-con V-Pro. We haven't had any issues.

        It's all a matter of tuning. The E85 mix we have out here in Nevada is pretty consistant, if you live somewhere where it gets really cold than the mixture may be different in the winter.

        Stock F-series blocks are pretty stout. I think you would be fine at 10:1 and 15psi. But it will depend on what size turbo you're running....15psi on a 14b is a lot different than 15psi on a GT30r...

        -Kyle
        SOHC Non-VTEC F-series for life

        "It is the fools prerogative to utter truths that no one else will speak."
        -Morpheus (The Sandman)

        Comment

          #5
          How high of compression is E85 good to?

          Comment

            #6
            What other supporting modifications are you planning on having? Are you sleeving the block? Would it be possible to go with a lower compression piston *i went with bisi 8.1:1* and more boost where you need it? I know with the hondata S300 you can alter the ammount of boost with each gear that your in. I've not looked at how it works but I assume it works with the PWM (pulse width modulation) controller and an external wastegate. How it tells what gear your in, I'm not sure, I need more research into it.

            But I think that an option open to you.
            Been a long time. Still alive...

            Comment

              #7
              Originally posted by WilliamW View Post
              What other supporting modifications are you planning on having? Are you sleeving the block? Would it be possible to go with a lower compression piston *i went with bisi 8.1:1* and more boost where you need it? I know with the hondata S300 you can alter the ammount of boost with each gear that your in. I've not looked at how it works but I assume it works with the PWM (pulse width modulation) controller and an external wastegate. How it tells what gear your in, I'm not sure, I need more research into it.

              But I think that an option open to you.

              I'm pretty sure the S300 compares MPH, RPM, and MAP to determine what gear you're in.

              8.1:1 is really low...I'm running stock 8.8:1 compression and I think that's too low. I would go min. of 9.0:1 on any turbo motor. It's better to run a higher CR than more boost, especially if running crappy 91 octane. Plus, the higher the compression the faster boost response.

              Just my opinion.

              -Kyle
              SOHC Non-VTEC F-series for life

              "It is the fools prerogative to utter truths that no one else will speak."
              -Morpheus (The Sandman)

              Comment

                #8
                Is this a USDM or JDM F22B? If it's USDM I would grab some of Bisi's 9.0:1s and call it a day. Keeping in mind that the stock C/R is 8.8:1 so you're gaining power in an all motor sense. If it's JDM your C/R is 9.3:1 but I've heard of some JDM F22Bs making close to 9.7:1. I would say leave that alone. Not sure where you would find F22A/B pistons in 10.0:1 C/R in the first place, so you'd have to throw down extra money to have a custom set made from scratch. Another way to raise compression is to also find a thinner headgasket or you can mill the head. There are also high compression valves out there as well that can raise C/R up .5:1; but not sure if they would be available for the F22. Bisi's valvetrain might can offer something similar.

                My recommendation would be to stay with what you have, and either swap the H23 intake manifold OR get the adapter that would allow you to fit either the H22 Euro R manifold or the Skunk2 intake manifold. Then get as big as a throttle body as you can find as I've heard that can be HUGE under boost. Bisi has a mild cam and gear designed for boost for a very nice price; drop that in as well. And of course, it's all in the tune....

                But the other guys are right, don't lean on the turbo too much, try to support it as much as possible. Remember that when you pull off the line the turbo won't be able to help you until it's spooled up; until then it's all motor. Don't wanna have a gutless engine without boost.
                '94 JDM H22A: 178whp 146wtq

                Originally posted by deevergote
                If you say double dutch rudder, i'm banning you...

                Comment

                  #9
                  F22B motor can't use the H23 manifold.

                  Comment

                    #10
                    she has a JDM DOHC F22B, If all you want is 300whp, i would stick with stock block just buy extra supporting mods.

                    Comment

                      #11
                      Higher compression = Less room for error while tuning.

                      Something to think about. I'm sure with some 10.1 pistons would work with 13-15 PSI on a really really good tune, assuming the engine has been built to accommodate that high of compression in other areas.

                      Is this a stock block? What other things have been done to the engine?
                      R.I.P. Veronica - JDM F20A swapped 2.0 Si wannabe.

                      Comment

                        #12
                        Ya it's a jdm f22b - my lovely husband blew the rings in it so I gotta build. Not planning on sleeving the block. I saw bisi has some 8.2 to 1 I was thinking those might work. I use crome as our engine management. Gonna run w 550cc injectors. I have a pretty large turbo it's a ar 70 with a 60 something trim.

                        Oh I'm not gonna race it- it's more just a fun car go fast on the highway but not beat on it at the track.

                        I've seen bisi"s cams yes I want n the future - big throttle body huh? What others fit this car? I got plenty of h23 intakes sitting round should I switch to the h23?

                        It's damn near impossible to get any gas over 93 here even that is only at a few stations e85 would be out of the question.
                        Last edited by midnightrayne; 02-21-2010, 03:19 AM.

                        Comment

                          #13
                          Do h23 pistons work in the f22b? If so I found some weisco pistons that are 9.1

                          Comment

                            #14
                            I would def go higher than lower

                            Just need a competent tuner

                            There are people boosting stock H22s & B18C5s no problem.


                            Originally posted by lordoja
                            im with you on that one bro! aint nothing beat free food and drinks any day of the week, even if its at a funeral

                            Comment

                              #15
                              So do the h23 pistons fit in the f22b?

                              Comment

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