nigelspeedy

nigelspeedy

Well Known Member
I'm at the firewall forward stage on my RV-8 and trying to get a handle on how an IO-360 oil system works. I see quite a few posts around where folks describe using various covers or shutters in winter to reduce the effective area of the oil cooler in order to get engine oil temperatures up to normal operating values. I was under the impression that the Lycoming engine has a vernatherm that regulates the flow of oil through or bypassing the oil cooler to some degree (like the thermostat in a car cooling system).

Why the need to cover up the oil cooler if there is a valve to reduce flow?
Are the fitted valves ineffective even if operating correctly?
Would a thermostat spiced into the oil cooler lines be an alternative to plates or variable shutters?

Thanks for any info you can offer.

Regards

Nigel
 
The vernatherm does not completely shut off all oil flowing thru the cooler. Some amount of oil is always circulating thru the cooler. It does not work exactly like a car engine's thermostat... instead when the vernatherm expands under high heat, the tapered end seals off a port that is really an oil cooler bypass passageway, thus forcing the oil to flow thru the cooler's plumbing instead of thru the bypass.

With an IO-360 engine, some sort of airflow control device on the cooler will generally be effective in helping get the oil temps up sufficiently on a cold winter day.

On my carbureted O-320, however, even with both front and rear of the oil cooler blocked off with plates, on a cold winter day I cannot get the oil temps up to 180.

On my friend's RV-8 with ECI Titan IO-360 we had issues at both ends of the temperature spectrum. On hot days we had trouble keeping the oil temps down enough, and ended up having to put a large expensive cooler on... and we still have high oil temps on the hottest days. On cold winter days, we couldn't get the oil temps up enough, so I conjured up an electric servo-operated door to open and close off the airflow on the back side of the cooler and a rocker switch under the instrument panel to adjust how much it's opened of closed. During summer, we remove the door completely to ensure no hindrance of airflow thru the cooler and re-install the door for winter flying... a simple piano hinge wire and one cotter pin on a clevis arm is all it takes to install/remove the door. Pics of this Rube Goldberg contraption can be seen here: http://imageshack.us/g/691/img4686k.jpg/
 
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Welcome to VAF.

There are a lot of good threads relating to the cooler system. See the search function. Here is one -

http://www.vansairforce.com/community/showthread.php?t=76725&highlight=thermostat

There is a company marketing a true thermostat system. Could'nt find the exact thread but it is on here somewhere.

Making the system work well is a balance between many factors - sizing the cooler, getting the airflow right (through the whole cowling system). Some are better (luckier??) at getting it right than others. Read up, persevere and consult with those that have gone through it, here on VAF and better yet, with local builders.

The average system built to average standards will probably work fine in average conditions. Getting it to work at the extremes is the challenge - thus the other measures adopted (variable cowl outlets, doors etc). Have fun and Good luck with your experiment.
 
Thanks for the quick responses

Chaps that helps out a lot and gives me a much better understanding.
Dan, nice work on the schematic.

Regards

Nigel
 
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