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Thread: The Race Prepared Merlin Sound

  1. #1
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    Default 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?

    https://www.youtube.com/watch?v=es65gYhP2ms&t=244s

    https://www.youtube.com/watch?v=N5HWJLcMbx8&t=3s
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  2. #2

    Default 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 at 05:47 PM.

  3. #3
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    Default Re: The Race Prepared Merlin Sound

    Quote 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?
    *My Air Race Site*

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    Default Re: The Race Prepared Merlin Sound

    Quote 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.

  5. #5
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    Default Re: The Race Prepared Merlin Sound

    Quote 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

  6. #6

    Default 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 at 05:29 PM.

  7. #7

    Default 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 at 06:19 PM.
    "young" Thomas

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    Default Re: The Race Prepared Merlin Sound

    Quote 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.

    Quote 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 at 04:49 AM.
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  9. #9
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    Default Re: The Race Prepared Merlin Sound

    Quote Originally Posted by CubersWrist View Post
    Reno always sounds so epic! Anybody ready for September yet!!!!!!!!

  10. #10

    Default Re: The Race Prepared Merlin Sound

    Quote 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 at 07:04 AM.
    "young" Thomas

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