REFLECTOR: Cooling VG's

[J.F.Sheehan at larc.nasa.gov]

Chuck,
What did you make the 1/2 inch VG's out off?
How many did you install
How far in front of the begining 
of the NACA did you place the VG's?

Jack
> After reading the recent postings on cooling, I installed larger VG's in 
> front of my overhead NACA inlets and my CHT temps were lowered significantly 
> (20-30F). Previously, I had used the small VG's (1/4" tall) and my CHT's 
> would get up to 425F on climb out on a not-very hot day (75F). I made up a 
> set 1/2" tall VG's and my CHT never got up to 400F on an 85F day on climb 
> out, plus they cooled to 360-370F in cruise. Next I'm going to see if the 
> small VG's will reduce oil temp, although it's not a problem (climb out 
> 210F, cruise 185F).
> 
> At the Arlington Air Show, I talked for awhile with the Gary Garvens, CEO of 
> ECI (Engine Components, Inc-Titan cylinders www.eci2fly.com ) who said that 
> ideally you'd like your cylinder to run between 350-400F. Above that, you 
> start reducing the life because of the unique alloy that all the cylinder 
> head mfgs use. In WWII, the brits invented a high copper alloy of aluminum 
> which retains it stregth under hi temp, and it's still used today. Under 
> higher temps, the copper migrates from the crystalline structure to the 
> grain boundary when it causes cracks (technical term is intergranular stress 
> corrosion cracking). According to the Lyco manual you can go to 475F, but he 
> said they wouldn't likely last to TBO at these temps. Turbocharged cylinders 
> are hard on heads. He further recommended that you can rebuild your 
> cylinders one time, assuming they've not been run too hard or hot.
> 
> Chuck H
> Std RG IO-360
> 
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