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  #31  
Old 12-02-2016, 01:11 PM
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I should also add, it isn't just the surface area, there are other factors affecting the airflow between rough finishes and smooth. Dan and others have documented them, but it would take a bit of searching for the "complete" scientific explanation.
I suspect your cylinder outer surfaces are "normal" and as designed.
I am scared of over simplification les I be smote by the Cooling Gods!
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Last edited by JonJay : 12-02-2016 at 01:19 PM.
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  #32  
Old 12-02-2016, 01:15 PM
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Tiger 74 Tiger 74 is offline
 
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Dan
"
Quote:
Ummmm.....178 KTAS at WOT, 1000 ft, standard day? Dave, assuming good airspeed calibration, that is really slow. A Showplanes fastback on a clean -8, with 185~195 HP from a 10:1 IO-360 parallel valve should be good for 190 knots plus. Are you sure of engine health? Perhaps ignition timing?
Really? Maybe I'm loosing more speed than I thought. I do have an MT 3 blade prop. That takes another 2-3 knots right?
Engine seems healthy, no signs of anything wrong. Ignition timing was checked. No flashing between fins. Oil cooler standard set up, without ducting to the rear. Plenum well sealed.
Maybe I'll have another look.
I knew I shouldn't have posted this thread!!!! There goes any free time over Christmas!
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  #33  
Old 12-02-2016, 02:45 PM
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Quote:
Originally Posted by Tiger 74 View Post
Dan
"
Really? Maybe I'm loosing more speed than I thought. I do have an MT 3 blade prop. That takes another 2-3 knots right?
Engine seems healthy, no signs of anything wrong. Ignition timing was checked. No flashing between fins. Oil cooler standard set up, without ducting to the rear. Plenum well sealed.
Maybe I'll have another look.
I knew I shouldn't have posted this thread!!!! There goes any free time over Christmas!
Not sure about the MT.

Double check me on the speed. Vans says top speed is 214 mph for 180 hp and 222 mph for 200 hp...186 knots or 193 knots.

P-mags are easy to time...just blow in the tube. Want to conduct a simple experiment? Go fly a top speed run, record TAS and CHTs. Now retard timing 5 degrees and repeat the flight. Just put the crank on 5 degrees ATDC (rather than TDC), do the timing set procedure, and go fly again. If I recall correctly, you'll be at 21.6 with the jumper in.
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  #34  
Old 12-02-2016, 02:54 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by DanH View Post
...P-mags are easy to time...just blow in the tube. Want to conduct a simple experiment? Go fly a top speed run, record TAS and CHTs. Now retard timing 5 degrees and repeat the flight. Just put the crank on 5 degrees ATDC (rather than TDC), do the timing set procedure, and go fly again. If I recall correctly, you'll be at 21.6 with the jumper in.
Assuming this flight is best power mixture and low altitude, my prediction is no change in speed and the CHT drops 5-10 degrees across the board.
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  #35  
Old 12-02-2016, 05:12 PM
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Quote:
Originally Posted by DanH View Post
Double check me on the speed. Vans says top speed is 214 mph for 180 hp and 222 mph for 200 hp...186 knots or 193 knots.
Just for comparison, I have a stock airframe -8, stock factory Lycoming IO-360-A1B6 (650 TTSN), slick mags, and 74" Hartzell BA prop.

At Reno this year, I qualified at 222.681 mph, slightly better than Van's numbers but on a closed course.

I have cooling drag to lose because my CHT's never go above 380, and during a hot Reno race (95+ degrees) the max CHT I've seen is 365!

Skylor
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  #36  
Old 12-02-2016, 05:15 PM
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Quote:
Originally Posted by skylor View Post
Just for comparison, I have a stock airframe -8, stock factory Lycoming IO-360-A1B6 (650 TTSN), slick mags, and 74" Hartzell BA prop.

At Reno this year, I qualified at 222.681 mph, slightly better than Van's numbers but on a closed course.

I have cooling drag to lose because my CHT's never go above 380, and during a hot Reno race (95+ degrees) the max CHT I've seen is 365!

Skylor
Impressive.
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  #37  
Old 12-02-2016, 05:28 PM
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Default Respectable.

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Originally Posted by JonJay View Post
Impressive.
It's respectable. Jason Rovey was impressive in 2013 when he qualified his stock -8 in the 225 mph range! My point is, the original poster may have something going that that his both hurting his performance as well as causing high CHT's. The louvers are a band-aid to get temps under control but he still has either poor engine performance or high (cooling) drag, or both...

Last edited by skylor : 12-02-2016 at 05:33 PM.
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  #38  
Old 12-02-2016, 05:43 PM
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Originally Posted by skylor View Post
It's respectable. Jason Rovey was impressive in 2013 when he qualified his stock -8 in the 225 mph range!
Both darn respectable, given Stead's elevation and temperature. The 6000~7000 ft density altitude means they go even faster near sea level.
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  #39  
Old 12-02-2016, 06:02 PM
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Originally Posted by DanH View Post
Both darn respectable, given Stead's elevation and temperature. The 6000~7000 ft density altitude means they go even faster near sea level.
Conditions for my qual run this year:

Temp: 73F
Baro: 29.88
Wind: 10G19

That works out to be about 7300' DA "on the course"

Last edited by skylor : 12-02-2016 at 06:07 PM.
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  #40  
Old 07-05-2017, 12:24 PM
Love2fly Love2fly is offline
 
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Default Where did you buy those vents for the lower cowling?

I have the same problem and want to buy a set and get them installed this week. Any guidance is appreciated!
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