Cockpit heat thru oil cooler?

Has anybody directed the air from the back of the oil cooler thru the heat muffler and then to cockpit, instead of just the normal inlet from upper baffle section?

Was thinking it would save me 1 extra hole to cut in the baffles, and preheat the air into the heat muffler to help on those extra cold days instead of doing 2 heat mufflers in series?

Obviously would take a duct on the back of the oil cooler to adapt it to the tubing.

I have done just that but I have a little different configuration than most RV-9's. I run an IO-360 with cold air induction, piston oil squirters, and electronic ignition. All three of these features add heat to the oil instead of the cylinder heads but it also means I run a much larger oil cooler than most. I have a 13 row oil cooler mounted on the firewall and that is fed by a 4" duct from my baffles. The heater hose is on the back side of the oil cooler and I have a flapper valve on the very end of the outlet duct so that even when I have the heater duct completely closed I can get some heat from the bypass oil in the cooler. So far it has worked out ok but I have noticed that in the very cold days when the OAT is around zero degrees I have to run the engine at a little higher RPM to keep the oil temperature up enough to give me heat.

If you want to see my setup you can read this post on my blog. http://www.darinanderson.com/2018/09/oil-cooler-outlet-ducting-installed.html

Not so sure

I suspect that the airflow through the oil cooler is considerably more than an exhaust heat muff is designed for. You wouldn't want to restrict the flow through the oil cooler in any way. The SCAT hose diameters are very different.

I am very familiar with a plane that was plumbed as you suggest, and it suffered high oil temps until the oil cooler air exhaust was re-plumbed back to the traditional way. Oil temps went back to normal.

Proceed with caution...............

Check this post out http://www.vansairforce.com/community/showthread.php?p=262955&highlight=Flapper+control#post262955

My hangar-mate has an oil cooler-based cabin heat system and no muffs on the exhaust in his RV8A. To put it succinctly, there is sufficient heat to fly in the early autumn. There is almost no perceptible heat for true "winter" operations.

In our Glasair Sportsman I have the inlet cooling air duct to the oil cooler controlled via a Bowden cable-actuated butterfly valve. Even now in our "spring" temperatures that valve is in the fully closed (zero cooling air flow) position and I struggle to get the oil up to 180F. Thank goodness the airplane is plumbed with a 2" heating system taking warm air off the exhaust, otherwise we'd freeze.

Heat muff requires air flow

It is said that the exhaust pipe will destruct if covered with no air flow. So, if/when the oil cooler air flow is reduced or terminated for winter flying, the exhaust pipe under the heater muff might suffer. YMMV

I stuck a 1-1/2" scat duct up against the outlet of my oil cooler and ran it into the cabin via a shutoff valve. It seems to work just fine in the NC climate. Maybe not so much up North.