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PT3 under research

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    PT3 under research

    Hello everyone,

    Even though I have just registered to this forums, I have been around sucking up information and sourcing my inspiration for at least a few years. The reason I registered was to start my own thread in order to exchange knowledge.

    After seeing and hearing all the hype about the mighty F22 I decided to dig into it the way I do Ė since I am a mechanical engineer and have access to a lot of useful machines, I like to go all the way and build an engine by carefully planning every detail.

    Previously I have built only motorbike engines for MX and SuperMoto, but since I drive an Accord myself, I figured why not build one hell of a daily driver. Since I am not in a hurry with this thing and my income has not reached the level that will allow me to speed this up, I will be taking my time and slowly posting the progress here.

    So I went on an picked this up at a local scrap yard





    The engine was actually an F20Z1, it is the european variant of F series, but it features the same, legendary, PT3 head casting, the camshaft has OE reference # identical to USDM F22A6, so do the valve springs, and practically the rest of the valvetrain.

    Cleaned it up a bit with a diesel bath and my soda gun





    And brought it to a laser scanner office
    The advertised single point accuracy of this machine is 0.028 mm (one thousandth of an inch), but with the method of generating a whole point cloud, I am able to split this number in at least two



    I am also scanning the camshaft and rocker arms to be able to work out the valvetrain specifics to extreme level of detail.











    I was able to recreate these with just the use of a MituToyo digital caliper



    More to follow...

    #2
    Nice work. I am very interested in your findings as I am also in the midst of a very time and cash consuming PT3 build myself.
    MR Thread
    GhostAccord 2.4L Blog

    by Chappy, on Flickr

    Comment


      #3
      That's really awesome, I imagine you can probably run FEA on the scanned in parts and find the weak points of the build? I would never leave the shop if I had that equipment at my disposal!

      Comment


        #4
        Amazing work, eager to see where this goes. And friend of mine and I would be in heaven with some equipment like that! Like Rusty said, we'd never be seen again.

        Comment


          #5
          Originally posted by GhostAccord View Post
          Nice work. I am very interested in your findings as I am also in the midst of a very time and cash consuming PT3 build myself.
          I know all about your project Ghost, I have been admiring it for a long time now.

          Originally posted by rustyaccord View Post
          That's really awesome, I imagine you can probably run FEA on the scanned in parts and find the weak points of the build? I would never leave the shop if I had that equipment at my disposal!
          Not only I can do Finite Element Analysis, I will do it also.
          But it will most likely not be related to structural integrity, because the only thing found on PT3 head that could come closest of concerning me for strength would be rocker arms. And I have seen plenty - these are not weak by any means.. At least from design standpoint. The FEA I have in mind is CFD.

          Originally posted by AhYesCB7 View Post
          Amazing work, eager to see where this goes. And friend of mine and I would be in heaven with some equipment like that! Like Rusty said, we'd never be seen again.
          Thanks! The equipment is not mine of course, but I still happen to know a lot of great guys around here in posession of all kinds of good stuff. I will be needing all of it.


          So here is the big and heavy .STL laser scanner file. Took me some 3 hours to get it scanned and I still could not work up enough patience to scan it completely. Anyway, as much as itís got is more than enough already for what I intend to use it.





          I also touch probed the cam and rocker shaft seats, spark plug holes, dowel pins and everything else I was able to find on that thing. It will become useful later on.



          Here is a complete CAD model of the PT3 ports.
          I usually hear a lot of confusion in people when reffering to scanning a part and creating a CAD (computer Aided Design) model. What the machine actually scans is a huge point cloud, imperfect, with holes, and contains absolutely no surfaces or solids, which is what CAD conists of. So in order to get a usable CAD file out of this, thatís a whole lot of work with a very advanced CAD system, manually recreating the surfaces from the scanned reference. Took me a good deal of about month or so.







          What I can already tell from this is that exhaust ports are small for comparison. The intake is big, with relatively small valves, but it is surprisingly smoothly tapered off. Very interesting.
          All four pots are identical and completely symmetric. The valves are very long and so are the valve guides - this is good because it allows more aggressive cam profiles to be run with much less problems than usual.

          Intake / Exhaust Port volume: 141.3 CC / 83.1 CC

          Port length: 91.07 mm / 78.21 mm

          Average port diameter: 44.44 mm / 36.79 mm

          When I said that I have access to a lot of useful machines, I forgot to add that flow bench is not one of them, so I will be using another approach for evaluating the flow potential Ė CFD (Computational Fluid Dynamics).
          I will post the CFD results later.

          Comment


            #6
            Remarkable work! You're going to spark a lot of new thoughts with regard to building and modifying these engines. Thank you for sharing this with us!

            I've seen the differences on the intake and exhaust ports, but only from a hands on perspective. This totally shines new light on the subject.
            1993 Accord DX | Rosewood Brown Metallic



            www.anthonypalileo.com
            www.anthonypalileo.com/watches (secret link)

            Comment


              #7
              Originally posted by KBA View Post
              Intake / Exhaust Port volume: 141.3 CC / 83.1 CC

              Port length: 91.07 mm / 78.21 mm

              Average port diameter: 44.44 mm / 36.79 mm

              When I said that I have access to a lot of useful machines, I forgot to add that flow bench is not one of them, so I will be using another approach for evaluating the flow potential – CFD (Computational Fluid Dynamics).
              I will post the CFD results later.
              Nice to see the CAD drawings for the ports, very good reference material. I'm sure there are quite a few people who will appreciate your work. Also nice to see some computer generated numbers for the port geometry that back up my earlier findings. I used the old school caliper and fluid measuring methods when I was figuring out my intake and exhaust manifold designs. I wasn't too far off...lol


              As far as flow bench s go. I set up a MAF sensor, MAP, IAT and barrow sensors hooked up to a shop vac with a fixed diameter plumbing fitting. Took recorded the initial readings. Then put it on the bench after each modification I did and recorded those numbers. I have a basic number but not the exact CFM that they flow. I do know the flow/velocity is better than it was from the factory. And most of all, I know that the numbers suit my camshaft, intake and exhaust manifold designs.
              Last edited by GhostAccord; 07-08-2017, 02:49 PM.
              MR Thread
              GhostAccord 2.4L Blog

              by Chappy, on Flickr

              Comment


                #8
                Originally posted by apalileo View Post
                Remarkable work! You're going to spark a lot of new thoughts with regard to building and modifying these engines. Thank you for sharing this with us!

                I've seen the differences on the intake and exhaust ports, but only from a hands on perspective. This totally shines new light on the subject.
                No problem, I'm always happy to share my findings
                Regarding the port size difference, as weird as it may seem, but I think Honda has developed them for a reason. If you study the difference in volume flow combined with valve lift, it appears the exhaust to intake flow capacity is roughly 75&#37;. Which actually coincides with a "general rule of thumb" for race engine development. At least according to Performance Trends and some other reputable companies / builders.

                Originally posted by GhostAccord View Post
                Nice to see the CAD drawings for the ports, very good reference material. I'm sure there are quite a few people who will appreciate your work. Also nice to see some computer generated numbers for the port geometry that back up my earlier findings. I used the old school caliper and fluid measuring methods when I was figuring out my intake and exhaust manifold designs. I wasn't too far off...lol


                As far as flow bench s go. I set up a MAF sensor, MAP, IAT and barrow sensors hooked up to a shop vac with a fixed diameter plumbing fitting. Took recorded the initial readings. Then put it on the bench after each modification I did and recorded those numbers. I have a basic number but not the exact CFM that they flow. I do know the flow/velocity is better than it was from the factory. And most of all, I know that the numbers suit my camshaft, intake and exhaust manifold designs.
                For the port volume I would trust your method more than mine, simply because a CAD surface cannot copy the real walls as good as a liquid can, there will always be some tiny error. My numbers should be closer to a port that has been cleaned up with a dremel tool, so will be the CFD results, but I don't really consider this difference significant.

                And thumbs up for your flow bench idea, definatelly could be worth a try sometime.


                OK so when all the components have been carefully recreated using some of the best tools I have in my CAD arsenal, I can finally slam all of this together and just feel happy how nice it all looks. I even felt the urge to render the image!



                By performing a simple motion analysis (twist the cam 360 degrees from TDC), I can log the valve travel. In this case I chose to log the movement in each degree of cam rotation. It is then some basic math to figure out the velocity at a given engine speed, and from that - valve acceleration. According to Mr. Newton and his second law of motion (Force = mass x acceleration) I will be able to figure out exactly how good are my valve springs and most importantly - up to what RPM is it safe to take them in combination with stock cam, or any other cam for that matter.


                (the numbers in this graph are based on 6500 RPM crank speed)

                Now for all of this I will also need the component masses of course. Knowing the material and density it is easy as 123 to ask the computer for weights, but I just felt it to be more accurate if I could use my kitchen scales for that.

                F20Z1 & F22A6 Intake / Exhaust

                Valve weight: 46.5 g / 44 g

                Retainer weight: 11.5 g / 11.5 g

                Spring weight: 50 g / 48 g

                Lock weight: (below the kitchenwear resolution - 1 g)

                Rocker moment of inertia: 70319 g*mm^2 / 51181 g*mm^2
                (obtained by weighing the rockers, adjusting the material density until CAD weight matches the real piece, and asking for moment of inertia around rocker shaft axis)
                Last edited by KBA; 07-10-2017, 05:22 AM.

                Comment


                  #9
                  I had to use a fair bit of imagination to evaluate the stock springs properly. I have seen information online that F22A6 intake springs are taller than exhausts. I have found that it is not true. I used a very simple way to describe these springs - stationed it on a surface, put a retainer on top and hanged a couple of batteries so that their weight is pulling on a string, attached to the retainer. By carefully weighing the batteries and measuring the spring length changes in three steps, I was able to list down the following information:

                  F20Z1 & F22A6 Intake / Exhaust valve springs:

                  Free length: 52.6 mm / 55.6 mm

                  Seat length: 44.2 mm / 44.4 mm

                  Rate: 24.0 N/mm / 17.14 N/mm

                  Seat pressure: 45.3 lbs / 43.2 lbs

                  I have to add that these measurements might differ from others who have done it and most notably from new springs since the ones I used were old and had god knows how many miles on them. But anyway, should not be that far from truth.

                  Here's a graph how spring pressure changes with valve lift.

                  Comment


                    #10
                    And the promised CFD results:
                    Test pressure: 28" H2O
                    Air temperature: 20 deg C








                    You can already tell that exhaust port needs more work than intake. For me it is easier to look at it this way - lower flow velocity at a given region means there is a "dead space" that either needs to be filled, or the surrounding area modified to introduce flow into it.

                    CFM values:
                    Note - as I already explained, these results will be closer to ports that have been cleaned with a dremel tool, simply because CAD surface is unable to copy the wall texture.



                    Comment


                      #11
                      That dead air on the long wall in front of the valve stems and guides on the exhaust ports is strange. I do remember that there was a big lip just after the exhaust valve seat on my PT3 head. Is that the cause of this dead area behind the valve on the long wall /port roof on this sim?
                      MR Thread
                      GhostAccord 2.4L Blog

                      by Chappy, on Flickr

                      Comment


                        #12
                        Well, I am by no means a porting expert, but I have donated my fare share of time to this subject.

                        To answer your question, I would say it is about 40&#37; because of that lip. The other 60% is because there is such a difference in length between short side radius (SSR) and long side radius (LSR). The flow is very lazy. It will always take the shortest path possible, in this case - the port floor where the radius is much smaller. This leaves the big "cavity" along the ceiling uninhabited. More so because of that lip. The flow will just go along the SSR and escape as quickly as possible. You can see something similar happening on the port floor somewhere in the middle. That probably means the floor is not continuous and the blue area points to a slight dip.

                        I have discovered my own formula for designing ports - keep the floor with as large of a radius as possible (even if it means to lift it), and keep the ceiling as straight as possible. You can then make the port wider to account for the smaller cross section. I have done exactly that in my SuperMoto build and realized the port with 5 axis CNC. Scored a CFM increase by 40%, but I had to weld quite a lot to accomplish it.
                        Last edited by KBA; 07-11-2017, 02:29 AM.

                        Comment


                          #13
                          I went with 1mm larger exhaust valves and seats. Ported the SSR to take as much of that hard curve out as possible. I don't have access to a HF tig welder for aluminum. I have not yet been able to play around with flattening out the LSR. Although, going with the larger seat opening allowed for more work to be done around throat of the LSR. That along with raising the port roof, did increase flow quite a bit. I would assume my port may have a bit less of a dead air space before the valve guide now but filling it in would be nice.

                          I would love to put some material in there and work with making more of an shark fin/hump transition just in front of the valve stem/guide. TRhen carry that to the exit of the port.

                          HF tig machine is my next purchase for the garage.

                          What do you use for adding material to your aluminum heads?
                          Last edited by GhostAccord; 07-11-2017, 08:23 PM.
                          MR Thread
                          GhostAccord 2.4L Blog

                          by Chappy, on Flickr

                          Comment


                            #14
                            I remember I once tried to get some good results by playing around with those shark fin transitions around valve guides. Since flow bench and spare head were not an option, I used my bike's laser scanned head file and CFD'd the hell out of it. One CFD run on single valve lift takes about an hour to complete on my i7 SSD equipped laptop. I did literally hundreds.. What I found was one of two cases:
                            - either I really could not design a proper shark fin transition
                            - or it really does not help that much in general

                            I found that the best results can be obtained simply by cutting those guides and leaving a naked valve stem. For my bike that was not an option since the guides were already super short from factory, but I see the PT3 is a whole other story. I have never seen guides this long.

                            Here's a quick sketch of what I did to my bike's intake port that I described earlier:






                            (The CFM of this head was obtained @ 12" H2O. When converting to 28" standard, the result would be ~282 CFM @ 0.400 lift. 36 mm valves)

                            Notice the dead area just behind the valve? This is just about as good as it gets with a tiny little hump of naked valve guide out of the ceiling. Adding shark fins only made it worse, but removing the valve guides completely made it a little better.

                            About the welding - since getting an electrode inside that tiny hole proved to be too much of a challenge for local masters, I went the Techno-Weld (soldering) route. Had to take the head to the other side of the country for that, thank god Latvia is small . Here's the result:



                            Conclusion: I will not go this way ever again.. Unless I really have to. The process is very hard, time consuming, and cost me ~200$ for a single cylinder engine. The head is subject to a lot of heating during that process, and the end result is full of flaws, not to mention that the thickness that was added later made the CNC machine cry for help when spending countless hours eating that hard soldering layer away. If I had not been a student at that time with free access to CNC, it would have cost me a fortune to get that thing done. And if that was not enough, I had to pull the head after the very first race because obviously the heat from soldering had warped it. I saw the coolant leaking through the head gasket just before the last run. Next time I will do it like I always have - using JB Weld epoxy. That stuff has proven to work really well with intakes.

                            You can find the full thread of my bike's build here: http://supermotojunkie.com/showthrea...nversion/page2

                            The porting story starts in page 2.

                            Comment


                              #15
                              Back to the topic:

                              I have used the data previously shown, to create analysis file in excel.
                              Purpose - to evaluate the RPM ceiling of any potential valvetrain.



                              Here you can see that it all depends on component weights, cam profiles and spring data. The values you can see at the moment are complete F20Z1 & F22A6 stock - as measured (milage unknown).

                              In the graph above you can see three curves:
                              - Lift [mm]
                              - Required spring force [N]
                              - Actual spring force [N]

                              What is important is that required spring force stays below the actual spring force. If that does not happen, the valve gets tossed and damages itself, the rocker, and the cam lobe. Given enough RPM, valve toss can result in collision with the piston causing the ultimate engine damage.
                              I have found that these engines are equipped with 6500 RPM redline for a reason - because the valve toss (at least at this milage) occurs just below 6600 RPM.

                              I have also messed around with some springs from ebay and equipped the file with "plug & play" functionality. Allows me to virtually swap the springs and cams and see what happens. All the other cam profiles that you see at "the cam shelf" are the result of my boredom and nothing close to what is available. Regarding "the spring shelf", these are what's found on ebay, except for Bisimoto. I have emailed them a while ago asking for the specs on their springs, but they do their best to ignore me.

                              F20Z1 & F22A6 Intake / Exhaust cam specs:

                              (Lash): 0.25 mm / 0.30 mm
                              Centerline: 112 deg / 116 deg
                              Duration @ 0.050" /w lash: 188 deg / 194 deg
                              Lift @ 0.050" /w lash: 9.20 mm / 9.15 mm
                              Overlap @ 0.050" /w lash: 0 deg
                              Last edited by KBA; 07-12-2017, 04:10 AM.

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