High Oil Temps----Problem Solved

[airguy]

Originally Posted by db1yg

Hi Greg,

Ref your fuel vapor issue--another way of reducing this is to increase the "head pressure" by going down in injector restrictor size. I believe the stock injector restrictors for the 180 hp Lyc (or clone) are 028. I went down to 024 and reduced about 80% of my issue (stumbling on low power approaches and stumbling when taxing in after a flight in hot conditions). Don Rivera of AFP did the calculations for me and said I could go all the way down to 023 and still have sufficient flow for up to (speaking from memory here) 185hp.

Cheers,

db

Now THAT is definitely an interesting piece of information, and I'll follow up on it, thanks!

[Zuldarin]

Hey Greg, let us know what you find out on the injector size issue. I could definitely use a little love in the hot fuel flash department as well.

[rightrudder]

Hey Greg,

Have you considered going to a cowl flap? ASA makes that really trick electrically actuated one...you could open it during climbs to lower temps. Maybe a last resort after other options are exhausted, but another arrow in the quiver...

[airguy]

Originally Posted by rightrudder

Hey Greg,

Have you considered going to a cowl flap? ASA makes that really trick electrically actuated one...you could open it during climbs to lower temps. Maybe a last resort after other options are exhausted, but another arrow in the quiver...

Ready to order that one if I can't solve it another way - my primary goal was to accomplish the cooling without adding drag, but cowl flaps are always the nuclear option.

[BillL]

Originally Posted by airguy

Ready to order that one if I can't solve it another way - my primary goal was to accomplish the cooling without adding drag, but cowl flaps are always the nuclear option.

Hi Greg, I'm not sure you posted it already, but a good measurement of upper and lower cowl pressures with a digital manometer (vs airspeed) would greatly help the to quantify the effects of possible solutions.

If the upper is low then the inlet diffuser is controlling, if the lower is high then the exit is restricted.

[rv7charlie]

Have you tried 'exit ramps' at the bottom of the firewall? I know it will be a bit harder to do with a nose wheel strut, but might be worth the effort before you start with cowl surgery.

Charlie

[N941WR]

Originally Posted by airguy

... I'm going to insulate my FWF fuel delivery line as well. It works fine with 100LL but running 91 premium auto fuel (with the higher vapor pressure) it absorbs too much heat during low power operatings (lower fuel flow, more time spent in the line picking up heat) and has a tendency to flash into vapor between the servo and the injectors where the pressure drops...

Please do that before you next flight.

This thread explains why that is so important.

[airguy]

Originally Posted by N941WR

Please do that before you next flight.

This thread explains why that is so important.

Heh, funny you should post that, I read that old thread about a week ago. Yes, I'm very aware of the dangers posed by hot fuel flashing into vapor in the lines. Until I am absolutely sure it is resolved I'll be doing all my landings and takeoffs with 100LL and using the high-vapor pressure fuel only for cruise. The time that I really pushed it for the previous tests I was at KBPG with their very long runway, it gives me plenty options for a low-altitude engine failure on takeoff, I'll continue to do my testing there.

[N941WR]

Fly safe my friend!

What really got me were the extended flights at low speeds. The low fuel flow and low cooling air did me in.

The good news was that the insulation solved the problem.

[Bruce]

Originally Posted by airguy

Yes, the inlet dams are unchanged from the pics on my build site.

Next step is cutting the cowl exit even with the firewall and flying that, and I'm going to insulate my FWF fuel delivery line as well. It works fine with 100LL but running 91 premium auto fuel (with the higher vapor pressure) it absorbs too much heat during low power operatings (lower fuel flow, more time spent in the line picking up heat) and has a tendency to flash into vapor between the servo and the injectors where the pressure drops.

I'm going to do both of those things this week and fly again this coming weekend, then the next step is going to be a lengthy one - plenum inlet fiberglass surgery. It needs to be cleaned up anyway, even if it's not one of the major contributing causes (though I believe it is), it's going to change. I think cutting the exit opening wider is going to be my major contributor.

Greg,
I see something is working.
How is it going in phase 1???

Boomer