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-   -   Hot CHTs? (http://www.vansairforce.com/community/showthread.php?t=144485)

Tiger 74 11-30-2016 02:52 PM

Hot CHTs?
 
Got hot CHTs?
Fit these, they lowered my CHTs by 30 degrees with no noticeable loss of speed and look **** sexy too!!
http://s58.photobucket.com/user/dont...tml?sort=3&o=7
http://s58.photobucket.com/user/dont...tml?sort=3&o=6
http://s58.photobucket.com/user/dont...tml?sort=3&o=5
http://s58.photobucket.com/user/dont...tml?sort=3&o=4

DanH 11-30-2016 03:36 PM

Quote:

Originally Posted by Tiger 74 (Post 1130788)
they lowered my CHTs by 30 degrees with no noticeable loss of speed

Lowered 30 from what original temperature, at what OAT?

g zero 11-30-2016 03:47 PM

CHT
 
Dan do you ever feel that you are beating a dead horse when it comes to high CHT's and Hot Oil ? You have a lot of patience 😩

Marc Bourget 11-30-2016 04:23 PM

Fell like he's beating a dead horse ???

Maybe if he had a God Complex.


Good Guys value themselves on how they can help others be the best that they can be. I see this in Dan by the effort he expends and the intellect he lends to those tasks.

Way to go, DanH !!

g zero 11-30-2016 05:31 PM

CHT
 
Dan definitely knows how cooling works . And he definetly cringes at bandaid cooling fixes like louvers.
I'm just surprised he doesn't get tired of trying to educate builders that do the same stuff over and over .

Tiger 74 11-30-2016 09:15 PM

Thanks for the friendly words guys! Sorry if I have offended the purists!
CHT temps were up around 410-415 F oil up to 210 in climb.
Have Showplanes cowl, 10:1 Pistons on a Superior IO360, James plenum chamber (modified to fit and seal properly), standard Vans oil cooler.
OAT was around 70F at the time of testing.
P-Mags were set to 25c.
Everything looked to be set up right, but the temps were too high.
I added the louvres to get the problem solved during flight testing to get the permit to fly.
It worked. CHTs now steady and balanced at 370-380 in climb, oil no higher than 180.
I saw no noticeable reduction in speeds, so drag penalty seems low. Why not keep these on permenantly? They don't look too bad (pretty good actually).

Bevan 11-30-2016 10:17 PM

Are the louvers fixed or can they be closed?

Bevan

Tiger 74 12-01-2016 02:41 AM

They're fixed

N941WR 12-01-2016 04:09 AM

Quote:

Originally Posted by Tiger 74 (Post 1130901)
...P-Mags were set to 25c.
...

With the jumper in, the P-mags are set to 26.2* BTC when timed to TDC.
If you programmed them, with a -1.4 offset, then you are at 24.8* BTC.

On an engine with a tight cowl (Show planes or Sam James) and high compression pistons, dropping the timing that 1.4 degrees can make a big difference without a lose of power. In fact, as you raise your compression ratio, you should move the timing event closer to TDC.

Toobuilder 12-01-2016 07:00 AM

Quote:

Originally Posted by Tiger 74 (Post 1130901)
CHT temps were up around 410-415 F oil up to 210 in climb...

Everything looked to be set up right, but the temps were too high...

I saw no noticeable reduction in speeds, so drag penalty seems low...

What did the temps do in cruise? A transient temp of 415 is not out of line, but at 70 OAT should be better, admittedly.

Do you have the bypass ducts on #3 and #1 to address the well known "zero fin depth issue"? Also, did you tune up your intercylinder baffles to seal ALL air leaks, or are they just installed staight out of the box?

Ignition timing is also a big factor.

Concerning the drag penalty, adding a massive increase in outlet area certainly hurts you. There's no way around that. Or more to the point, if you missed some of the details mentioned above, you have a lot of air running through the cowl that is not contributing to cooling, and THAT is where the drag is.


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