Scott Hersha
Well Known Member
This is not exactly a 'new' thread, since there has been countless posts relating to this subject, and I have read them all --- twice. What I need is opinions from those in the know on one of problems relating to oil temps. My situation is not critical, but uncomfortable for me. I have an RV-8 with an ECI Titan O-360, carbed, one electronic ignition, and 9:1 pistons. My cruise oil temp up high with OAT's in the 55-60 degree range are running 200-207. Temps increase in the traffic pattern or during formation flying, with temps reaching 210-217. My baffles are tight - they would hold water if turned upside-down. I've RTV'd every possible opening around my oil cooler (Van's FWF Niagra 2002A). Today I removed my vernatherm and found out that it only touches the seat on about half of the circumference of the tapered valve surface. What I need to know is, does this make that much difference? Even though it doesn't seat all the way around, there can't be that much of a gap in the area not making contact with the seat. How much will that effect oil temperature? I know this oil passing past the seat is not going through the cooler, but how much oil is getting bypassed? And how bad is that? There is a procedure where you can lap the seat up to .010, but then the temp where the vernatherm makes contact and starts cooling through the oil cooler is higher. The alternative is to get another seat - ie. oil filter adapter - and hope this one is seated correctly. I installed and flight tested another new vernatherm today and there was no change.
Another thing I tried after talking to a friend who got this idea from ECI. He said any Van's airplane could get a 20 degree improvement in oil cooling by putting a blocking plate over the #4 cylinder cooling fins where they almost touch the oil cooler on the Van's baffle. Theoretically, the #4 cylinder exhaust valve which is about an inch from the bottom of the oil cooler and experiences temperature approaching 1400 degrees, has a negative effect on oil temps because air passes over this area of the fins and some of it is sucked through the oil cooler. Even though putting a plate in front of this area of the cooler, thereby deflecting the cowl air down through the fins with none going through the oil cooler - effectively blocks about 1/3 of the oil cooler, this is still better than having very hot air going through the oil cooler. Well, I made this modification, and I curved the top of it to 'catch' some air and send it down through the fins to cool the exhaust area of the fins. Net result: zero.... it made absolutely no difference, good or bad. No noticeable difference in #4 CHT or in oil temperature.
My friend Jon Thocker with an almost identical airplane, but a SW8406 cooler is getting 10-15 degree cooler oil. He doesn't have the electronic ignition either. That gives me a higher CHT, because of more complete burning of the gasses in the combustion chamber due to earlier ignition timing, and lower EGT's, because there is less burning going on heading down the exhaust pipe. These numbers are verified in side by side testing with out two airplanes.
What I need is advice on what I can do to lower my oil temps. Obviously, I need to figure out the vernatherm issue first, even if the difference is small. Next, should I get another cooler? The SW8406 is possibly good for 10 degrees or maybe more. The 8432 will give me even more, but I have to remove and modify my rear baffle. I'd like to fix this problem without spending my wife's future windfall if possible. The 8406 is $615.00, and the 8432 is $661.00 at Pacific (both are more at Spruce). I've thought about trying a Mocal/Setrab, but haven't gotten the gumption yet. It would require some engineering and a lot of unknowns - but this is summer and I want to fly.
Suggestions??? I mostly want to know about this vernatherm issue....
THANKS,
Another thing I tried after talking to a friend who got this idea from ECI. He said any Van's airplane could get a 20 degree improvement in oil cooling by putting a blocking plate over the #4 cylinder cooling fins where they almost touch the oil cooler on the Van's baffle. Theoretically, the #4 cylinder exhaust valve which is about an inch from the bottom of the oil cooler and experiences temperature approaching 1400 degrees, has a negative effect on oil temps because air passes over this area of the fins and some of it is sucked through the oil cooler. Even though putting a plate in front of this area of the cooler, thereby deflecting the cowl air down through the fins with none going through the oil cooler - effectively blocks about 1/3 of the oil cooler, this is still better than having very hot air going through the oil cooler. Well, I made this modification, and I curved the top of it to 'catch' some air and send it down through the fins to cool the exhaust area of the fins. Net result: zero.... it made absolutely no difference, good or bad. No noticeable difference in #4 CHT or in oil temperature.
My friend Jon Thocker with an almost identical airplane, but a SW8406 cooler is getting 10-15 degree cooler oil. He doesn't have the electronic ignition either. That gives me a higher CHT, because of more complete burning of the gasses in the combustion chamber due to earlier ignition timing, and lower EGT's, because there is less burning going on heading down the exhaust pipe. These numbers are verified in side by side testing with out two airplanes.
What I need is advice on what I can do to lower my oil temps. Obviously, I need to figure out the vernatherm issue first, even if the difference is small. Next, should I get another cooler? The SW8406 is possibly good for 10 degrees or maybe more. The 8432 will give me even more, but I have to remove and modify my rear baffle. I'd like to fix this problem without spending my wife's future windfall if possible. The 8406 is $615.00, and the 8432 is $661.00 at Pacific (both are more at Spruce). I've thought about trying a Mocal/Setrab, but haven't gotten the gumption yet. It would require some engineering and a lot of unknowns - but this is summer and I want to fly.
Suggestions??? I mostly want to know about this vernatherm issue....
THANKS,