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The Race Prepared Merlin Sound

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  • The Race Prepared Merlin Sound

    Quarantine has me watching a lot of Reno videos. I've always been curious why Ghost had a different sound than Strega/Voodoo (first video). I was hesitant in thinking it's something about the way Shanholtzer preps them, but then I watched one of Jason's old videos of Miss America and I could be trying to convince myself, but it sounds a lot closer to Ghost than Strega/Voodoo (second video).

    Only thing is Miss America sounds closer to Strega/Voodoo the past few years than it does to the 2002 video.

    Any thoughts?

    Here is Jimmy Leeward ripping off a 465mph qual lap during the early part of the week, Reno 2011.


    Skip Holm takes the legendary P-51D Mustang 'Dago Red' up for the qualification attempt and ends up as the fastest qualifier for 2002 at 497 mph.Brent Hisey ...
    Reno from '99 to '22

  • #2
    Re: The Race Prepared Merlin Sound

    My first thoughts are that neither Ghost nor Miss A are pulling the rpm's or MP that Voodoo/Strega typically pull. I will bet the speeds showed that too.

    The last year (two?) Miss A showed up with a far more serious race prep I understand. I thought that was discussed on here at the time.

    FUn to watch the clips though!

    GP
    Last edited by gp70442; 04-07-2020, 05:47 PM.

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    • #3
      Re: The Race Prepared Merlin Sound

      Originally posted by gp70442 View Post
      My first thoughts are that neither Ghost nor Miss A are pulling the rpm's or MP that Voodoo/Strega typically pull. I will bet the speeds showed that too.

      The last year (two?) Miss A showed up with a far more serious race prep I understand. I thought that was discussed on here at the time.

      FUn to watch the clips though!

      GP
      Good thoughts. Jimmy's focus was definitely on air frame over engine modification, so that does make sense. I'm 99% sure Ghost wasn't running a tube engine either, at least I have photo evidence of that in 2010. That would pretty much end up being the same engine that Miss A runs I think..?

      I'm not sure how much more serious Miss A's prep has been. Without it being a tube engine, there is only so far you can go right?
      Reno from '99 to '22

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      • #4
        Re: The Race Prepared Merlin Sound

        Originally posted by GRNDP51 View Post
        Good thoughts. Jimmy's focus was definitely on air frame over engine modification, so that does make sense. I'm 99% sure Ghost wasn't running a tube engine either, at least I have photo evidence of that in 2010. That would pretty much end up being the same engine that Miss A runs I think..?

        I'm not sure how much more serious Miss A's prep has been. Without it being a tube engine, there is only so far you can go right?
        Please explain the "tube engine" mod. I've heard explanations, but not sure if I got good info. Thank you.

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        • #5
          Re: The Race Prepared Merlin Sound

          Originally posted by Reever View Post
          Please explain the "tube engine" mod. I've heard explanations, but not sure if I got good info. Thank you.
          A Tube Merlin replaces the whole aftercooler assembly with a big tube. Less restriction to airflow, and possibly allows better ADI injection (I don't know for sure.) The aftercooler assembly is quite heavy.

          I'd guess this is the reason the race engine sound different.

          Will

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          • #6
            Re: The Race Prepared Merlin Sound

            Tube or no tube, I would have to say the difference in the sound of engines in the clips the OP posted are due to purely the sound of the props. Once they start pulling MP required to move a P-51 490 mph or so, 90% of the sound you hear is the prop howling, then the increased exhaust note once the aircraft has passed you. A 450-460 mph lap just doesn't sound anything like a 490 lap. The only anomaly in the clips is Risky Business making a lot of prop noise but Risky was never more than a 450 mph airplane to my knowlege. I'm willing to have my fading memory refreshed though.


            GP
            Last edited by gp70442; 04-08-2020, 05:29 PM.

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            • #7
              Re: The Race Prepared Merlin Sound

              RPM plays a very large part of the sounds we hear. This has been mentioned a couple times on this site with regards to the future electric racers.

              It's also a sign of energy being wasted. Best example is Sport #30 compared to #39. #39 sounds louder and "better" but to my ears #30 being quieter is a sign that our propeller is more efficient when it comes to turning hp into thrust rather than noise.



              I bet the echo/roar from the VoS would sound similarly good if the T-6 swarm came down the VoS.
              Last edited by CubersWrist; 04-08-2020, 06:19 PM.
              "young" Thomas

              http://teamonemoment.com/

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              • #8
                Re: The Race Prepared Merlin Sound

                Originally posted by gp70442 View Post
                Tube or no tube, I would have to say the difference in the sound of engines in the clips the OP posted are due to purely the sound of the props. Once they start pulling MP required to move a P-51 490 mph or so, 90% of the sound you hear is the prop howling, then the increased exhaust note once the aircraft has passed you. A 450-460 mph lap just doesn't sound anything like a 490 lap. The only anomaly in the clips is Risky Business making a lot of prop noise but Risky was never more than a 450 mph airplane to my knowlege. I'm willing to have my fading memory refreshed though.

                GP
                There’s a lot in your answer, but this makes sense too. I think if we had more footage of Ghost doing around 500 we might get a better idea. I still think it would have that more muscular sound since the MP isn’t as high as Strega doing 500. I went and listened to the Risky qual again and it’s interesting how much different it sounds than Miss A. Risky only qualified at 401 that year. Miss A had to be pretty close to that but the sound is different. That’s what got me started with thinking different builders prep different sounding engines.

                Originally posted by CubersWrist View Post
                RPM plays a very large part of the sounds we hear. This has been mentioned a couple times on this site with regards to the future electric racers.

                It's also a sign of energy being wasted. Best example is Sport #30 compared to #39. #39 sounds louder and "better" but to my ears #30 being quieter is a sign that our propeller is more efficient when it comes to turning hp into thrust rather than noise.



                I bet the echo/roar from the VoS would sound similarly good if the T-6 swarm came down the VoS.
                Never really noticed this difference until the video. Always thought they sounded pretty similar but 39 does have a louder presence.
                Last edited by GRNDP51; 04-09-2020, 04:49 AM.
                Reno from '99 to '22

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                • #9
                  Re: The Race Prepared Merlin Sound

                  Originally posted by CubersWrist View Post
                  Reno always sounds so epic! Anybody ready for September yet!!!!!!!!
                  Random Air Blog

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                  • #10
                    Re: The Race Prepared Merlin Sound

                    Originally posted by GRNDP51 View Post
                    Never really noticed this difference until the video. Always thought they sounded pretty similar but 39 does have a louder presence.
                    Yep, the smaller diameter, swept tips, and extreme twist angle are all designed for 400+mph.
                    Click image for larger version

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                    Here is the drag curve for ballistics. Same thing applies with the blade tip speed. As you get closer and closer to Mach 1 the drag rise is exponential. So if you can decrease the diameter and slow the tip speed just a little you can do a lot for reducing the drag on the propeller blade as its spinning through the air.

                    Now having said all of that, it is possible the smaller prop hurt our performance the first couple years. Because the prop is built on the assumption that we were going 400mph. If you don't reach 400mph, you aren't in the design window. Now we are flying around with a smaller diameter which means we have less blade area to generate thrust.
                    Last edited by CubersWrist; 04-10-2020, 07:04 AM.
                    "young" Thomas

                    http://teamonemoment.com/

                    Comment


                    • #11
                      Re: The Race Prepared Merlin Sound

                      Originally posted by CubersWrist View Post
                      Yep, the smaller diameter, swept tips, and extreme twist angle are all designed for 400+mph.
                      [ATTACH=CONFIG]24597[/ATTACH]
                      Here is the drag curve for ballistics. Same thing applies with the blade tip speed. As you get closer and closer to Mach 1 the drag rise is exponential. So if you can decrease the diameter and slow the tip speed just a little you can do a lot for reducing the drag on the propeller blade as its spinning through the air.

                      Now having said all of that, it is possible the smaller prop hurt our performance the first couple years. Because the prop is built on the assumption that we were going 400mph. If you don't reach 400mph, you aren't in the design window. Now we are flying around with a smaller diameter which means we have less blade area to generate thrust.
                      Is Jeff's prop a relatively stock Hartzell?
                      Reno from '99 to '22

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                      • #12
                        Re: The Race Prepared Merlin Sound

                        Jeff and others have been using Hartzell's race prop

                        Article from a couple years ago: https://www.kitplanes.com/prop-war-reno-races/
                        "young" Thomas

                        http://teamonemoment.com/

                        Comment


                        • #13
                          Re: The Race Prepared Merlin Sound

                          Originally posted by CubersWrist View Post
                          Jeff and others have been using Hartzell's race prop

                          Article from a couple years ago: https://www.kitplanes.com/prop-war-reno-races/
                          Haven't seen this article before, good stuff thanks
                          Reno from '99 to '22

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                          • #14
                            Re: The Race Prepared Merlin Sound

                            Originally posted by RAD2LTR View Post
                            A Tube Merlin replaces the whole aftercooler assembly with a big tube. Less restriction to airflow, and possibly allows better ADI injection (I don't know for sure.) The aftercooler assembly is quite heavy.

                            I'd guess this is the reason the race engine sound different.

                            Will
                            It's not about "better" ADI injection. ADI is not used on the aftercooler engines. ADI injection essentially replaces the aftercooler.

                            The main reason for the aftercooler delete is that it doesn't survive extremely high MAP. The cooling vanes of the aftercooler tend to crack. It is thus replaced with a tube and ADI injected...

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