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PatJr
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Joined: August 09, 2010
Posts: 253
Location: earth
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 Posted: Mon Sep 11, 2023 10:08 am Post subject: Speed of Air pistons |
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anyone seen these?
https://s19529.pcdn.co/wp-content/uploads/2021/05/3516diesel.jpg
pistons with golf ball dimples ?
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SGKent 
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Joined: October 30, 2007
Posts: 42403
Location: at the beach
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| Posted: Mon Sep 11, 2023 10:49 am Post subject: Re: Speed of Air pistons |
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never seen it. Only thing I can think is that it increases surface area of the piston and conducts away heat. It may also cause more air mixing, which would reduce unburned HC. My instinct tells me there is no measurable gain in performance. It may increase efficiency slightly and reduce CO just like Honda did by introducing turbulence into their engines with 3 valves. Besides, the world is going to EV and these engines will all be obsolete in a few years. Your kids will ask, daddy, what was it like to drive a car powered by gasoline or diesel?
In diesels https://www.motortrend.com/news/golf-ball-dimple-diesel-piston-engine-technology/
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TXHCBeetle
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Joined: October 07, 2021
Posts: 177
Location: Boerne, TX
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| Posted: Tue May 07, 2024 4:41 pm Post subject: Re: Speed of Air pistons |
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You probably would have gotten a lot more replies if you posted this in the performance/engines/transmissions forum.
Icon pistons offers a Speed of Air upgrade, you can see dimpled T1 pistons on page 4:
https://www.thesamba.com/vw/forum/viewtopic.php?t=...p;start=60
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Wildthings
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Joined: March 13, 2005
Posts: 52284
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| Posted: Wed May 08, 2024 3:20 am Post subject: Re: Speed of Air pistons |
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One article refers to a light truck, which is what an F350 pickup is as a heavy duty diesel and another claims a 15% increase in power which I would say it likely BS. As for aircooled engines, I think it is possible that dimples might lead to cooler running pistons and if it worked for the piston, it should do the same for the heads.
Cooler pistons and heads could mean more resistance to knock, which would allow for the use of higher compression, which would increase power and mileage a bit.
It would certainly be easy to build an engine with two stock pistons and two identical pistons that have been dimpled and compare the head and exhaust temps, maybe tightening the deck a bit on the dimpled pistons to keep the compression the same. |
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aeromech
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Joined: January 24, 2006
Posts: 17615
Location: San Diego, California
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| Posted: Thu May 09, 2024 7:59 am Post subject: Re: Speed of Air pistons |
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Interesting bit of trivia.
My university physics teacher invented those dimples in golf balls. Made the ball go further. The PGA outlawed them for tournament play. My instructor sued and won a million dollars.
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NASkeet
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Joined: April 29, 2006
Posts: 3186
Location: South Benfleet, Essex, UK
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| Posted: Thu May 09, 2024 12:29 pm Post subject: Re: Speed of Air pistons |
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| aeromech wrote: |
Interesting bit of trivia.
My university physics teacher invented those dimples in golf balls. Made the ball go further. The PGA outlawed them for tournament play. My instructor sued and won a million dollars. |
I think the purpose of the golf-balls' dimples, was to trigger turbulent-flow, so that flow-separation occurred much further around the ball, and hence reduce drag. I think this is also the reason why aircraft wings have, or at least had, small fences on the wing surface.
https://www.livescience.com/32446-why-do-golf-balls-have-dimples.html
https://en.wikipedia.org/wiki/Wing_fence
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NASkeet
Samba Member
Joined: April 29, 2006
Posts: 3186
Location: South Benfleet, Essex, UK
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| Posted: Thu May 09, 2024 12:35 pm Post subject: Re: Speed of Air pistons |
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| SGKent wrote: |
never seen it. Only thing I can think is that it increases surface area of the piston and conducts away heat. It may also cause more air mixing, which would reduce unburned HC. My instinct tells me there is no measurable gain in performance. It may increase efficiency slightly and reduce CO just like Honda did by introducing turbulence into their engines with 3 valves. Besides, the world is going to EV and these engines will all be obsolete in a few years. Your kids will ask, daddy, what was it like to drive a car powered by gasoline or diesel?
In diesels https://www.motortrend.com/news/golf-ball-dimple-diesel-piston-engine-technology/ |
If I am not mistaken, purpose-built electric vehicles simply have a forward & reverse selector, rather like the Van Doorne variomatic transmission on my father's 850 cc DAF 44. If driving-school cars in the United Kingdom adopt such purpose-built electric vehicles, driving-test candidates will ONLY qualify to drive cars with automatic transmission! Most diesel and petrol engined vehicles in the United Kingdom have manual transmission
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Nigel A. Skeet
Independent tutor (semi-retired) of mathematics, physics, technology & engineering for secondary, tertiary, further & higher education.
Much modified, RHD 1973 VW "1600" Type 2 Westfalia Continental campervan, with the World's only decent, cross-over-arm, SWF pantograph rear-window wiper
Onetime member, plus former Technical Editor & Editor of Transporter Talk magazine
Volkswagen Type 2 Owners' Club (Great Britain)
https://vwt2oc.co.uk |
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raygreenwood
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Joined: November 24, 2008
Posts: 23102
Location: Oklahoma City
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| Posted: Thu May 09, 2024 1:40 pm Post subject: Re: Speed of Air pistons |
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| NASkeet wrote: |
| aeromech wrote: |
Interesting bit of trivia.
My university physics teacher invented those dimples in golf balls. Made the ball go further. The PGA outlawed them for tournament play. My instructor sued and won a million dollars. |
I think the purpose of the golf-balls' dimples, was to trigger turbulent-flow, so that flow-separation occurred much further around the ball, and hence reduce drag. I think this is also the reason why aircraft wings have, or at least had, small fences on the wing surface.
https://www.livescience.com/32446-why-do-golf-balls-have-dimples.html
https://en.wikipedia.org/wiki/Wing_fence |
Not quite on the wing fences. But they do work with the boundary layer air.
The dimples on the ball...yes...correct...they create uniform micro vortices which create a boundary layer around the ball reducing drag.
Nice explanation:
https://www.scientificamerican.com/article/how-do-dimples-in-golf-ba/
The wing fences (boundary layer fences) do exactly what they look like. Because of the sometimes not so sophisticated wing chord shape in the early jet days...coupled with a sweep back angle that is not always ideal, there was a tendency for the airflow that is going over the wing to slide sideways toward the wing tip, dumping lift. The wing fences literally halt this flow and force the air to move rearward over the top of the wing the way this air is supposed to go.
This mainly is an issue as airspeed drops toward the stall point and the nose angle has to pitch up. That lateral air movement loss along the wing can cause the plane to stall early.
https://en.wikipedia.org/wiki/Wing_fence#:~:text=B...%20energy.
Ray |
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jlrftype7
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Joined: July 24, 2018
Posts: 4518
Location: Chicago
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| Posted: Fri May 10, 2024 12:37 pm Post subject: Re: Speed of Air pistons |
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Metric Mechanic was offering those on their BMW engines years ago if I remember correctly. I doubt I still have their literature from the early '90s on their offerings of BMW engine performance upgrades.
I just checked their website, they don't seem to mention or offer that service anymore. They're doing things differently to the older BMW engines these days. No idea when they stopped offering the 'dimples'.. 
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