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  • Cams and Intake manifold

    I'm think about doing an Exintake swap on the 1.8, I know I'm going to get a squaretop and a nice header as well. Has anybody on here done this if so how was the idle and did you notice and real gain from the swap.


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  • #2
    I did an exhintake swap on a '99 NB1.

    How does it idle? On the stock ECU (I have a Megasquirt for 90% of the year), it idles like a small block Chevy with a big cam, "lub, lub, lub" instead of "silky smooth". It's not a problem, except it would always throw a code, and I couldn't get it to pass the OBD II test until I put the stock cam back in.

    Did I notice any difference? Again, on the stock ECU, it doesn't seem as "dead" as I remember but that is probably more due to minds-games than anything else. Running on the MS with the turbo engaged, it does still seem a bit "brighter" (if that makes any sense) in the midrange. But, again, that might just be me justifying a cam swap once a year.

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    • #3
      Originally posted by rwyatt365 View Post
      I did an exhintake swap on a '99 NB1.

      How does it idle? On the stock ECU (I have a Megasquirt for 90% of the year), it idles like a small block Chevy with a big cam, "lub, lub, lub" instead of "silky smooth". It's not a problem, except it would always throw a code, and I couldn't get it to pass the OBD II test until I put the stock cam back in.

      Did I notice any difference? Again, on the stock ECU, it doesn't seem as "dead" as I remember but that is probably more due to minds-games than anything else. Running on the MS with the turbo engaged, it does still seem a bit "brighter" (if that makes any sense) in the midrange. But, again, that might just be me justifying a cam swap once a year.
      LOL sounds like a waste of time mostly. :)
      sigpic

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      • #4
        Originally posted by rwyatt365 View Post
        it idles like a small block Chevy with a big cam, "lub, lub, lub" instead of "silky smooth".
        The only way to get that kind of idle quality is to have 30 or more degrees of overlap. Stock BP4W is 17 degrees. http://www.solomiata.com/cams.html

        Did you redrill the dowel pin to take away some of the overlap as supposed to do?

        [LOL sounds like a waste of time mostly
        Hundred of people have successfully done it.
        92 Italia "Competizione Speciale". 91 BRG, '69 Corvette "Mojo". '14 F150 Coyote 5.0. Looking for something blue.

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        • #5
          Originally posted by rwyatt365 View Post
          ... But, again, that might just be me justifying a cam swap once a year.
          That's dedication.
          '01 BRG #2807 FS: 4 nice black Chaparral's, $400

          Build log: http://forum.miata.net/vb/showthread...02#post7862902

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          • #6
            Originally posted by rwyatt365 View Post
            I did an exhintake swap on a '99 NB1.

            How does it idle? On the stock ECU (I have a Megasquirt for 90% of the year), it idles like a small block Chevy with a big cam, "lub, lub, lub" instead of "silky smooth". It's not a problem, except it would always throw a code, and I couldn't get it to pass the OBD II test until I put the stock cam back in.

            Did I notice any difference? Again, on the stock ECU, it doesn't seem as "dead" as I remember but that is probably more due to minds-games than anything else. Running on the MS with the turbo engaged, it does still seem a bit "brighter" (if that makes any sense) in the midrange. But, again, that might just be me justifying a cam swap once a year.
            By cam swap once a year do you mean it wipes out the cam shaft?


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            • #7
              Originally posted by metalman View Post
              LOL sounds like a waste of time mostly. :)
              Yeah, for the most part. But what the hell, it's in there.
              Originally posted by Dynra Rockets View Post
              The only way to get that kind of idle quality is to have 30 or more degrees of overlap. Stock BP4W is 17 degrees. http://www.solomiata.com/cams.html

              Did you redrill the dowel pin to take away some of the overlap as supposed to do?
              Yep, re-drilled the cam gear - used a template found on M.net.
              Originally posted by DavidC View Post
              That's dedication.
              Every year, to prep for the "Emissions Test" I have to;
              - Plug the stock ECU back in
              - Swap the 650cc injectors for stock ones
              - Remove the exhintake cam and put the stock cam back in
              - Take out the GM coils for the stock coils
              - Plug the EGR valve back in
              - Wire the turbo wastegate open
              - Then go through the drive-cycle to get the readiness codes to go green

              After the check, I "revert" back to Turbo-Mode and enjoy the rest of the year!
              Originally posted by GTOTT97 View Post
              By cam swap once a year do you mean it wipes out the cam shaft?
              See above.

              Since I have to remove the injectors ('cause the stock ECU won't run the 650cc injectors properly), it's just a few more bolts to take out the cam. I can get the whole thing done in about an hour. To me, 2 hours of wrenching and about a week of road-work for the readiness codes to reset is worth the effort.

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              • #8
                Ohh ok, I have a 91 so I wouldn't have to worry about that


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                • #9
                  Originally posted by Dynra Rockets View Post

                  Hundred of people have successfully done it.
                  Not debating what people have 'successfully' done. People successfully do lots of things that are mostly a waste of time, and for which there is often no significant benefit...and this seems to be one of them....but by all means, have at it. :)
                  sigpic

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                  • #10
                    Having dumped thousands of dollars into an N/A build... it's been fun but it's a long expensive Road!

                    If you're not planning on adding a standalone like MS Or similar I wouldn't go further than intake/header/exhaust mods if I were you.
                    The only thing that oughta be hella flushed is a toilet.
                    http://www.miataramblings.blogspot.com

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                    • #11
                      Adding it in after the fact is a days worth of work, basically a simplified timing belt job. Don't even have to pull the crank pulley.

                      Your build has hit enough snags already. Stop complicating it for the moment.

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                      • #12
                        Originally posted by Stealth97 View Post
                        I wouldn't go further than intake/header/exhaust mods if I were you.

                        Originally posted by iscariot View Post
                        Your build has hit enough snags already. Stop complicating it for the moment.

                        Solid advice, right here.
                        Chris and Lola

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                        • #13
                          Originally posted by Stealth97 View Post
                          Having dumped thousands of dollars into an N/A build... it's been fun but it's a long expensive Road!

                          If you're not planning on adding a standalone like MS Or similar I wouldn't go further than intake/header/exhaust mods if I were you.
                          MS but that's a few months out.


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                          • #14
                            Had a similar situation with a '99 track day miata. Owner had us install the RB header, squaretop, and MSM intake cam. It made a noticeable difference, but nothing mind blowing.

                            Later, the car received a DIYPNP to help extract more out of the goodies. It's not really worth it unless you're only looking for modest power gains and don't want to change how the car drives otherwise.

                            I wouldn't put too much more into an NA Miata motor than what this person did, personally.
                            Originally posted by Beastinthebushes
                            Do lots and lots of reading and research. Lots of vendors sell suspension, not just FM.

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                            • #15
                              The early 1.8 engine only needs compression with a mild 252-260/9mm intake cam and it wakes right up for street duty. Since you are building the shortblock anyway just add the 01+ 10:1 stock pistons (or 10.5 JDM units). Forget the other stuff
                              92 Italia "Competizione Speciale". 91 BRG, '69 Corvette "Mojo". '14 F150 Coyote 5.0. Looking for something blue.

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