RV9/A Flying in Summer

[N797EJ]

Hello all!

New RV9A owner. What an awesome airplane, it’s been great so far. We moved the airplane back home to Arizona. As you can imagine it’s starting to heat up here. We have noticed on climb out the airplane CHT’s and oil temp are getting hot. We have to lower the nose and pull back some power to help. Very slow climbs. We are trying to see if anyone has made any baffling modifications or and modifications at all to make these temps a little better has Arizona heats up?

On average we see about 425 degrees to 435 degrees something on a full power climb out. We don’t spend any time at that temp. We try out best to lower the nose and get those temps in the lower 400’s. On the oil temp we see something similar, 185 degrees on climb out and then in the low 170’s at cruise. Thank you all for any insights!

[MacCool]

I have the opposite problem here (Minnesota), but on hot days 90°+, (yes, we do get some hot days) I still have no CHT or oil temp issues on Vy climb-outs. Even on the the hottest days, I don't recall ever seeing CHTs over 400.

The firewall-forward builder (Don Swords) built a contained plenum with carbon fiber top rather than relying on baffling against the cowl. It works very well. I don't know if it would solve an Arizona-based heat problem, but I certainly suspect that sloppy or otherwise "problematic" baffle sealing will result in struggles with engine cooling under some conditions.

..

[maxmirot]

Originally Posted by N797EJ

Hello all!

New RV9A owner. What an awesome airplane, it’s been great so far. We moved the airplane back home to Arizona. As you can imagine it’s starting to heat up here. We have noticed on climb out the airplane CHT’s and oil temp are getting hot. We have to lower the nose and pull back some power to help. Very slow climbs. We are trying to see if anyone has made any baffling modifications or and modifications at all to make these temps a little better has Arizona heats up?

On average we see about 425 degrees to 435 degrees something on a full power climb out. We don’t spend any time at that temp. We try out best to lower the nose and get those temps in the lower 400’s. On the oil temp we see something similar, 185 degrees on climb out and then in the low 170’s at cruise. Thank you all for any insights!

I needed to add Antispat Aero's Cowl flap.

I suggest you do 2, one on both sides , for those 115 degree Scottsdale days

[scottmillhouse]

You may need to check and then retard the timing a degree or two below 25 to lower head temperatures. When my engine was new from Lycoming there was nothing I could do to have temperatures below 400. Turns out one of the new mags had drifted 7 degrees advanced. Once corrected I now rarely see over 350.

[blaplante]

Originally Posted by N797EJ

Hello all!

New RV9A owner. What an awesome airplane, it’s been great so far. We moved the airplane back home to Arizona. As you can imagine it’s starting to heat up here. We have noticed on climb out the airplane CHT’s and oil temp are getting hot. We have to lower the nose and pull back some power to help. Very slow climbs. We are trying to see if anyone has made any baffling modifications or and modifications at all to make these temps a little better has Arizona heats up?

On average we see about 425 degrees to 435 degrees something on a full power climb out. We don’t spend any time at that temp. We try out best to lower the nose and get those temps in the lower 400’s. On the oil temp we see something similar, 185 degrees on climb out and then in the low 170’s at cruise. Thank you all for any insights!

Read up on the endless baffle sealing threads available here. RV's don't have very big air inlets (or outlets) compared to a Cessna 172 or similar. The grossly sloppy baffle seals you'll see on those planes (done by certificated A&Ps) are not adequate when the air to work with is much less. On the typical Cessna you'll find several 1" square holes without looking hard. On the RVs, a single 1" square (or equivalent) air leak makes a big difference in engine temp.

One clue... where did the plane live before?

Oh, and fix the leaks before you start chopping holes for louvers or cowl flaps....

[Dugaru]

These are actually not wildly unusual temps for a -9A in warm weather, from what I can tell. Check out the temps they were seeing in that CAFE report on the -9A! IIRC they were getting 465 on climbout.

Are you leaving the mixture full rich during climb? That, louvers, a plenum, and a nice low-nose attitude tend to keep my hottest cylinder (#2) at 420 or below in the summer. 420 is the top of Mike Busch's "yellow arc" for Lycoming cylinders so I figure I can live with that during climb.

I also noticed an improvement when I tightened the "vertical" metal baffling firmly against the cooling fins at the top of the cylinders; I left a bit of a gap where it covers the bottom of the cylinders since the fins are less pronounced there.

As I continue tinkering, I'm starting to wonder if (a) I need a bit more, or less, of a "wall" in front of the #2 cylinder, and (b) if it might help during climb to close my oil cooler shutter, to keep more air on those two cylinders. My oil cooler is mounted behind #4.

Your oil temps seem fine to me, but maybe I've gotten used to too much heat - what range are you shooting for, and why?

Originally Posted by N797EJ

Hello all!

New RV9A owner. What an awesome airplane, it’s been great so far. We moved the airplane back home to Arizona. As you can imagine it’s starting to heat up here. We have noticed on climb out the airplane CHT’s and oil temp are getting hot. We have to lower the nose and pull back some power to help. Very slow climbs. We are trying to see if anyone has made any baffling modifications or and modifications at all to make these temps a little better has Arizona heats up?

On average we see about 425 degrees to 435 degrees something on a full power climb out. We don’t spend any time at that temp. We try out best to lower the nose and get those temps in the lower 400’s. On the oil temp we see something similar, 185 degrees on climb out and then in the low 170’s at cruise. Thank you all for any insights!

[Avanza]

I would check fuel flow >14 USG if 160 hp at take off.
Check ignition timing, usually 25 deg.
Normal oil temp on climb out in hot weather, expect 210-225 F.
Ad high temp sealant on ALL places where cooling air can bypass the cylinders.
A small string between cylinder heads will help.
Speed = higher differential pressure = more flow = better cooling.

https://siliconedepot.com/hi-temp-re...-gasket-maker/

Good luck

[ty1295]

As many have stated the baffles and rubber need to seal first.

Verify the aircleaner also has a rubber baffle so it doesn't pressurize the bottom side of the cowl.

If all that is ok, cowl flaps do work.

[Ed_Wischmeyer]

Lotsa good information here, and I had to do all these things (except mag timing) on my RV-9A. My IA also took a saw blade and removed some casting flashings from the cylinders, and found small items within the cooling fins. My problem was high EGTs, and those were contributing to the high CHTs.

The solution was to exchange the stock carburetor for an MA-4SPA 10-3678-32, where the 3678 indicates that it is a different model from the carb that came with the plane -- I think it was a stock Van's carb. The 3678 runs richer than stock, and mine was benched to be at the rich end of the spectrum.

That seems to have solved the cooling problem in Georgia summers, but I have to lean the O-320 aggressively, all the time. You're only up a thousand feet, so you might not see density altitude problems.

Good luck!

Ed

[Taltruda]

Ditto what Ed said.. check your carb model.. if it isn’t the one he pointed out, that may help..