Engine Temps in cold weather

bfisher · Post by **bfisher** » Thu Dec 15, 2011 8:46 am

I have a M7-235 and live in Nasville TN. When outside temps get below 40 degrees the cylinder head and oil temp get only 1/4 into the green. At those temps the cabil heat isn't adequate to keep the cabin warm. I have installed the plate on the oil cooler which helps a bit. Anybody have ideas on how to get the engine warmer in colder weather?

Mountain Doctor · Post by **Mountain Doctor** » Thu Dec 15, 2011 10:15 am

The cabin heat runs off the exhaust muff and is controlled by the EGT, not the CHT. OAT has little effect on the EGT.

If you have an engine monitor and are skilled in its use run at peak EGT and monitor parameters carefully. Do this at 75% or less power and you'll be warmer, have less plug fouling, burn less fuel, and engine longevity may also be increased.

NOTE:

Whereas this is true, it is controversial and a source of debate the last few decades, and will likely remain so fo years to come...

montana maule · Post by **montana maule** » Thu Dec 15, 2011 6:25 pm

If you go to my web site and click on Maule Operaters Blog at the bottom of that page there is a link to winterization kit. I have some pictures of what I have tried. With a few other mods I fly at -20F and can stay warm.

www.montanabyair.com

UP-M5 · Post by **UP-M5** » Thu Dec 15, 2011 9:59 pm

make sure your cabin is sealed up well (windows and doors)
and be sure your exhaust system is in good shape. flame tubes intact, muffler shrouds tight, and scat tubing not torn.

atlee dodge sells a new exhaust system that has a lot of angle steel welded to the muffler cans to increase the surface area and accordingly increase the cabin heat.

i regularly fly @ 20 below and find my cabin heat to be as good or better than any other single engine airplane i have ever been in.

Post by **andy** » Fri Dec 16, 2011 7:43 am

Before Maule Flight rebuilt my MX-7-180, I used the plate in the oil cooler to try and get oil temperature up a bit, but I abandoned that method in favor of putting a piece of metal foil duct tape across 1/2 of the inlet screen in the engine compartment. Easier to install and remove without removing the upper cowling and just as effective, plus you can vary the position of the tape to block off more or less of the screen with temperature changes.

Cabin heat is more a function of how air tight the cabin is than engine temperature. During the rebuild Maule Flight retaped the wing roots, installed new insulation and door/window weatherstripping. More than anything, that improved the cabin temperature since it got rid of air leaks. Even with oil temp around 150 degrees in outside air temps below 20 degrees, the cabin heat is adequate. I was worried that the addition of the observer doors in the front would make it colder and I was ready to put the removable pockets on, but I haven't had to do that at all. The AK guys would have a better take on how it feels in -30 degree temps, but it works fine down to 0F.

Island Flyer · Post by **Island Flyer** » Fri Dec 16, 2011 3:54 pm

I've have found the same thing, since rebuilding Island Flyer it is quieter and way warmer. Sealing all of the air leaks including some huge ones where the landing gear attaches to the frame and the brake lines come through the fuselage (see this blog entry http://web.me.com/rhysspoor/Site_2/Blog ... Shoes.html ). The other thing we did was to increase the heat coming in by putting studs on the muffler (look at the bottom of this blog entry http://web.me.com/rhysspoor/Site_2/Blog ... eller.html ) which is one of Tim's customized muffler systems.

Island Flyer · Post by **Island Flyer** » Fri Dec 16, 2011 3:55 pm

I've have found the same thing, since rebuilding Island Flyer it is quieter and way warmer. Sealing all of the air leaks including some huge ones where the landing gear attaches to the frame and the brake lines come through the fuselage (see this blog entry http://web.me.com/rhysspoor/Site_2/Blog ... Shoes.html ). The other thing we did was to increase the heat coming in by putting studs on the muffler (look at the bottom of this blog entry http://web.me.com/rhysspoor/Site_2/Blog ... eller.html ) which is one of Tim's customized muffler systems.

JLB · Post by **JLB** » Fri Dec 16, 2011 4:21 pm

I like the studs in the heat shrouds on the muffler. Did you do that yourselves or from the muffler company?

crbnunit · Post by **crbnunit** » Fri Dec 16, 2011 7:31 pm

Did you guys know there is an STC out there for a cockpit controlled cowl flap for the Maule? Someone here emailed the drawings to me. Pretty easy and straight forward. I think I still have it but the file is pretty big.

With two mufflers providing cabin heat, I can't say I've ever been cold even down to -20. In fact, there was one day at -15 I reached down to adjust some clothing and the seat belt buckle was hot to the touch from the heater blowing on it!

Island Flyer · Post by **Island Flyer** » Sun Dec 18, 2011 6:49 am

Tim sent it out for welding but I don't remember where. I know that he has made several design features that have made it heftier and works with a shop. I flew yesterday and that heater gets hot fast. One side bar however is that since the whole cabin is tighter potential CO leaks could be much more serious. I have noticed a big difference in the lack of airflow through and around seams. I did a little online research and settled on an electronic CO detector from Aircraft Spruce, it's the little key chain size portable one. Supposedly very accurate and fast and a fraction of the cost of some of the panel mounted. From what I read, the little stick-on CO detectors, by the time they turn any color (assuming you even noticed) your dead.

Engine Temps in cold weather

Engine Temps in cold weather

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