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    #61
    Explain requested

    Originally posted by SgtRauksauff
    I'm still hoping from an explanation of WHY a change in cam timing will have anything to do with compression. Compression (static, as is the subject under discussion) occurs when the cylinder reaches TDC and the valves are closed, right?

    Changing to the exhintake setup might change the lift and duration, but you will STILL have that period of time when the valves are closed and the contents of the cylinder are being compressed. The only way you're going to change that is by making the combustion chamber smaller. the only way to do that is to change the shape of the piston, or shave the head. Shaving the head also introduces a slight bit of timing change.

    but in no way does a cam profile change static compression. That's just not how engines work. If it is, please explain.


    --sarge
    Props for your projects bro, excellent in everywhere... even the family wagon is awesome sleeper and a plus plus for solo testings.

    Back to the question...

    Honestly dont ask me, I did the swap by the book like the other guy explained and even knows I asked him questions. I dont question he did the swap, what I question the gains he states. First, our cylinder heads work with hydraulic lifters, not like Sentras or Hondas which REALLY get the benefits of performance cams.

    I performed the swap and a friend asked me alleged stupid question of; What was your compression? I was skeptical, but could not resist not able to answer it. TO my surprise the compression did went down by 40psi. I tried different degrees to see if maybe I was a little off on any teeth or something. Checked the crankshaft was alligned, my timing, all good. Went back and check ALL cylinders and the compression was still the same 180 (remember I got Miata 2001 with shave head) from 230psi of what I usually have.

    I even got scared because I drove the car like that for a while and said to myself the engine was losing compression from before or I bent some valves; just something to give some light to my results. So, immediately I took the ExIntake cam and installed the factory Intake cam, did the test and compression was a healthy 230.

    Double check torque for the cams, any little thing. I honestly dont have any other answer than to say, you do the swap and see that what I say is not BS. The car ran fine and had no bad idling. This is what I am going to do. In the next few days do the swap again and take pics and if possible a video.

    Anyway, just do the swap and see the results.

    Comment


      #62
      psiturbo, the static compression ratio is a fixed, mechanical ratio completely determined by the ratio of the swept volume of the cylinder plus the volume of the combustion chamber to the volume of the combustion chamber when the piston is at TDC. Being a fixed mechanical constant, the static CR is not subject to modification by such things as changing valve overlap-this does not change the ratios involved. The ONLY way to raise static CR is to change the ratio of the volumes through such means as higher compression pistons, milled heads, thinner head gaskets, etc. Likewise, the only way to lower the static CR would be to change the ratio of the volumes in the opposite direction as in the case of switching to lower compression pistions.

      Happy Motoring!
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      Comment


        #63
        Originally posted by psiturbo
        Thats why this forum is so lame.

        First, we got a dude with a signature of a BMW.
        Yes, it's a BMW M3. *I* took the picture while working the 2003 Rolex 24 Hours at Daytona as a pit marshall. I liked the picture, due to the lack of a front tire and the car still made it back into the pits and was maybe 30' from where I was standing at the time.

        This I do know; compression is compression and does not lie. The question was shoot to the air to reveal if he really was talking the truth or not. Of course he/she or both is not telling the truth because compression DOES go down by changing the Intake Exhaust swap. The same way people do compression test to see if piston rings are bad OR OR OR>>> the valves are sticking or staying half way open.
        Static compression vs. dynamic compression. Nobody is argueing that dynamic compression doesn't go down with larger overlap and more aggressive cams. I'm pretty sure the tech articles that were put up here some years ago have covered that. A compression check gives you dynamic compression.

        Static compression, as goldstar has stated, has ZERO do with cams.
        "Never run out of real estate, traction & ideas at the same time"
        -93 MR2, 129 ES
        ClubProtege.com Tech Articles

        Originally posted by WTF
        Remember low compression makes more space for AIR, HEEELLOOOO!

        Comment


          #64
          Originally posted by psiturbo
          About cam strength, taken from Miata owners who compete in SOLO events and other races. This is the information posted from testing...
          First...before you throw Randy's website around more, let's begin with the fact that I've actually met and talked to Randy, the author of your magical webpage that you can't interpet worth a crap. And while we're at it, I'm also good friends with David Coleman, one of the FE3 page authors that are linked off of Randy's pages.

          Randy *USED* to run Atlanta region Solo events, but I haven't seen him around in a number of years.

          About solid CAMS Strength;

          "The stock 99-00 cams are actually quite strong from the factory. They will easily support higher hp levels with more lift adn duration than the 90-97 HLA cam. Mazda also makes an intake cam specifc to the home Japanese market. It has the same specs as the USA cam but the cam timing is advance a few degrees. If is part number BP5A12420. "
          Next, the term "strong" in the above paragraph means that the cams are more aggressive, not that they are physically stronger. Cams do NOT see huge loads, and most cams have enough bearings to not see shear stresses large enough for failure. Modern exceptions would be Toyota's 1ZZFE, which doesn't have an end bearing on one cam, and they have failures fairly frequently.

          [/quote]"Mazda reverted back to the solid billet design from the 1.6 instead of the hollow design of the 90-97 1.8."[/quote]

          Yes, and I'll gaurentee you that it's based on a financial basis rather than a strength basis. The cams aren't made out of any good steel anyway. It's actually pretty soft, which is why the lifters, even the HLAs will wear the cam lobes down over time.

          About High lift and duration cams when using hydraulic lifters and sotck ECU;

          "The 1.6 and 94-95 1.8 factory ECU settings are really not all that bad but they cannot recognize the substantial airflow increases needed for those HP levels (adding cams and such that take the ECU out of it's operating range can actually lower HP)."

          I, psiturbo, highly recommend reading this website again and again. Keep it in your favorites as a means of technical reference.
          SOLO MIATA CLUB
          The only point of the quoted paragraph from Randy's page is that the factory ECU and airflow monitoring system cannot detect the airflow changes from running hot cams. It has NOTHING to do with the cams itself, but the ECU's inadequacy for people running high lift/duration cams.

          Read the page again, actually think about what it's saying.
          "Never run out of real estate, traction & ideas at the same time"
          -93 MR2, 129 ES
          ClubProtege.com Tech Articles

          Originally posted by WTF
          Remember low compression makes more space for AIR, HEEELLOOOO!

          Comment


            #65
            incase your wondering PSI turbo the overlap does increase from the stock 19° up to 21° which could be the reasoning for your loss of PSI/cylinder.
            ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

            1992- project FE3..... 313 WHP @ 9.3psi




            I pet my dash when I get into the car..."good car"
            he actually has a mazda tree, parts grow on it

            Comment


              #66
              Originally posted by JesseSays
              First...before you throw Randy's website around more, let's begin with the fact that I've actually met and talked to Randy, the author of your magical webpage that you can't interpet worth a crap. And while we're at it, I'm also good friends with David Coleman, one of the FE3 page authors that are linked off of Randy's pages.

              Randy *USED* to run Atlanta region Solo events, but I haven't seen him around in a number of years.



              Next, the term "strong" in the above paragraph means that the cams are more aggressive, not that they are physically stronger. Cams do NOT see huge loads, and most cams have enough bearings to not see shear stresses large enough for failure. Modern exceptions would be Toyota's 1ZZFE, which doesn't have an end bearing on one cam, and they have failures fairly frequently.
              "Mazda reverted back to the solid billet design from the 1.6 instead of the hollow design of the 90-97 1.8."[/quote]

              Yes, and I'll gaurentee you that it's based on a financial basis rather than a strength basis. The cams aren't made out of any good steel anyway. It's actually pretty soft, which is why the lifters, even the HLAs will wear the cam lobes down over time.



              The only point of the quoted paragraph from Randy's page is that the factory ECU and airflow monitoring system cannot detect the airflow changes from running hot cams. It has NOTHING to do with the cams itself, but the ECU's inadequacy for people running high lift/duration cams.

              Read the page again, actually think about what it's saying.[/QUOTE]


              If thats the way you want to VIEW things, GOOD for you.

              Look at the websiter closely and it shows a picture of cams side by side to represent a hollow cam against a solid cam.

              Its great how you can convince yourself. In fact I know Randy too. LOL He used to sing with the Dandy Warhols!

              By the way, dont turn this thread toward me, still waiting for the DYNO chit from BPT323...

              Comment


                #67
                I don't get it??? Josh (Gen1GT), who was the *1st* one - that I'm aware of - to post the 'exhintake' cam idea on any public forum tested it and got 8whp. That's not just hearsay - he has posted the actual charts. I'm using the exhintake cam on my mildly built motor and I'm now at 133whp/118ftlbs. bpt323 hasn't posted a chart, but is there any real reason not to believe him?????
                Last edited by naprotejay; 04-12-2006, 12:31 AM.
                Original owner: 1991 Protege LX (now w/SOHC) and a few more BG's ....

                Comment


                  #68
                  thank you jason
                  ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

                  1992- project FE3..... 313 WHP @ 9.3psi




                  I pet my dash when I get into the car..."good car"
                  he actually has a mazda tree, parts grow on it

                  Comment


                    #69
                    Dyno chart- Here you are PSIturbo.... the **** works plain & simple.
                    Attached Files
                    ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

                    1992- project FE3..... 313 WHP @ 9.3psi




                    I pet my dash when I get into the car..."good car"
                    he actually has a mazda tree, parts grow on it

                    Comment


                      #70
                      Thanks for posting the chart Ryan

                      So 127whp/116ftlbs with the following, correct?? (anything I'm missing?):

                      Exhintake cam
                      Cam settings of EXHINT +5 EXH -1
                      17 degrees advanced timing (92 octane I assume???)
                      Cut intake manifold
                      RX7 meter
                      Cone filter
                      (Manifold back??) 2.5" exhaust w 3" cat
                      OEM 4-1 tubular manifold?

                      and Josh got 125whp/115ftlbs with the following:

                      Exhintake cam
                      Cam settings of EXHINT -6 EXH 0
                      18 degrees advanced timing (92? octane)
                      Tuned RX7 meter
                      Cone filter
                      Manifold back 2.5" exhaust
                      OEM 4-2-1 cast manifold

                      That's very nice numbers for not having dropped any $$$$ on a rebuild......

                      A few differences to especially note between my ~10:1 rebuild with the exhintake cam (currently 133whp/118ftlbs) is my stock ecu controlled timing of only ~8 degrees advance, and I've got a 2" exhaust..........
                      Original owner: 1991 Protege LX (now w/SOHC) and a few more BG's ....

                      Comment


                        #71
                        i don't believe i had my 2.5" on the car at that point & time, & i ran 18° w/ 89 octane. yes OEM early cast manifold.
                        ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

                        1992- project FE3..... 313 WHP @ 9.3psi




                        I pet my dash when I get into the car..."good car"
                        he actually has a mazda tree, parts grow on it

                        Comment


                          #72
                          bump your timing up to 18° if your on the stock ECU
                          ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

                          1992- project FE3..... 313 WHP @ 9.3psi




                          I pet my dash when I get into the car..."good car"
                          he actually has a mazda tree, parts grow on it

                          Comment


                            #73
                            lol, this is very funny thread :rofl:
                            Last edited by Lobo; 04-28-2006, 06:40 AM.
                            1997 323F 1.8 16V N/A 173whp

                            Comment


                              #74
                              glad im not the only one who enjoyed it.
                              ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

                              1992- project FE3..... 313 WHP @ 9.3psi




                              I pet my dash when I get into the car..."good car"
                              he actually has a mazda tree, parts grow on it

                              Comment


                                #75
                                Ok I hate to bring this subject back up. I know for some it might be getting old. First a little background. I race a egt on a circle track in a 4 cyl class that is supposed to be all stock. I'm looking to get everything out of this engine I can without a ton of $ and being totally illegal (bending the rules is ok tho). I've been wanting to do this cam swap for a while now so I went out tonight to do it and I was going to document my findings and post them on here. I really want this to work and I'm not trying to say its not true about the hp gains. First I measured the lift on my cams from the 93 donor motor and they were both the same lift. Then I measured the cams from my 96 motor and they were both the same lift. So I'm expecting the lift to be more on the exhaust cam and its not. Are the power gains achieved from a different duration or overlap? If anybody knows please let me know. Thanks

                                Comment

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