walter
Well Known Member
I've been living with hight CHTs since my initial flight. Last weekend it
was pretty warm around here (70's) [don't say it, even if you do
live in WI] and I can *easily* get to 450 in a 500fpm climb at 6000'.
Several causes come to mind; one of them is the LASAR ignition which
aggressively advances the timing. But another, and I'm really starting
to suspect that *this* is the real culprit is the size of the exhaust
area of the cowl and all the crap in this area which includes the
nose gear attachment, exhaust hangers, vertical cowl attachment
(with it's flat top and bottom), and the lower firewall lip (RV8s have
a nice rounded lip dookickey. All of this junk is in the way of the
air escaping (don't tell me I should have built a TD) and, all of this
crap is either perfectly round (read: totally un-aerodynamic) or
perpendicular to the flow of escaping air.
So how to fix and test? Well I can't just add an aerodynamic leading and
trailing edge to all the round stuff. I could enhance the shape of the
aluminum parts that are perpendicular to the flow, but that would
probably not have any significant effects (cowl hanger). So I need
something else and this morning I read a post on the lycoming group
about Ron Lee adding louvers to the bottom of his cowl. He had a link
to http://www.attawayair.com/rv6a.htm and reading that link I read
that Robbie was able to drip his CHTs by 25 degrees **Celsius**,
dude that's 77 degrees F! That puts me in the high 300's, excellent.
Who else has added louvers? What was your experience with CHT and
was your speed affected?
I found this site which has two sizes of louvers, I might start with the
small ones and see what effect they have. http://www.raceace.com/
Thanks for your input.
was pretty warm around here (70's) [don't say it, even if you do
live in WI] and I can *easily* get to 450 in a 500fpm climb at 6000'.
Several causes come to mind; one of them is the LASAR ignition which
aggressively advances the timing. But another, and I'm really starting
to suspect that *this* is the real culprit is the size of the exhaust
area of the cowl and all the crap in this area which includes the
nose gear attachment, exhaust hangers, vertical cowl attachment
(with it's flat top and bottom), and the lower firewall lip (RV8s have
a nice rounded lip dookickey. All of this junk is in the way of the
air escaping (don't tell me I should have built a TD) and, all of this
crap is either perfectly round (read: totally un-aerodynamic) or
perpendicular to the flow of escaping air.
So how to fix and test? Well I can't just add an aerodynamic leading and
trailing edge to all the round stuff. I could enhance the shape of the
aluminum parts that are perpendicular to the flow, but that would
probably not have any significant effects (cowl hanger). So I need
something else and this morning I read a post on the lycoming group
about Ron Lee adding louvers to the bottom of his cowl. He had a link
to http://www.attawayair.com/rv6a.htm and reading that link I read
that Robbie was able to drip his CHTs by 25 degrees **Celsius**,
dude that's 77 degrees F! That puts me in the high 300's, excellent.
Who else has added louvers? What was your experience with CHT and
was your speed affected?
I found this site which has two sizes of louvers, I might start with the
small ones and see what effect they have. http://www.raceace.com/
Thanks for your input.