Oilcooler Blog

Second Oil Cooler Upgrade


Unleashed has always been plagued by one problem, high oil temperature.  The original setup for racing in 2006 included a water spray bar on the oil cooler.  This did help, but made it very difficult to manage.  Nothing like one more quantity to maintain during flight!  I have constantly been working to improve the oil temps, but nothing really solved the problem.  I had it to the point where we could eliminate the water spray bar, but if you did a long climb, or the OAT was high, the oil temps would go to redline if not managed with power.  The best thing I found was retard the timing on the engine.  This did sacrifice some power but it was worth saving the engine in general.  If we were going to race at Reno this year, this problem had to be solved.

The original oil cooler was only 9 rows and for most 180-200 hp engines that would work, but maybe not enough for UNLEASHED.  In general it was thought that adding a bigger oil cooler would solve the problem.  But, with the tight cowling I was unable to install a bigger oil cooler in place of the old one.  So the next step was to add a second oil cooler, and just for good measure I would add 6 more rows of cooling capacity.  In theory this had to solve the problem.

To be sure all of the oil was cooled, we plumbed the second oil cooler in series with the first cooler.  The only space available was on the firewall in the same location the original oil cooler was located.  Then we began the debate about bringing cooling air off the rear baffle or from the outside of the cowl with a NACA duct.  In regards to CHT’s the engine is very cool and the plenum I made works very well.  Sometimes CHT’s are not warm enough.  So with all of that in mind, I thought it would be ok to use some of that plenum air to use on a second oil cooler with no noticeable rise in CHT’s.  This second oil cooler would not need much air to provide that little bit of extra cooling we needed.  For that reason we used a 2″ sceet tube from the #4 baffle. (#4 had the lowest CHT’s also)

So, how to get air from a tube 2″ in diameter to cover an oil cooler?  Build another plenum.. again  Your probably used to this part.  Get some polypropylene foam, shape it up, cover it in glass, melt the mold, glue it on.  Done.  And for that first amazing test flight when all would be solved and oil temps would be in the green?  Didn’t happen.  Oil temps remained as high as before.  That was a dream crusher,  let me tell ya..  So now I knew something was very wrong.  Next step was to remove the vernatherm to test that it was working properly and forcing oil to the oil cooler when needed.  Well, that engine is so tight in that little Lancair that I couldn’t remove the vernatherm without taking off the entire oil filter adapter.  4 bolts, some oil lines, tach cable and a big mess later, adapter was out.  First thing I notice is the gasket from the adapter to the accessory case is clearly not correct.  I mean,  it isn’t even close.  And to top it off, that gasket is blocking 75% of the port that allows oil to flow to the oil cooler, as well as letting oil bypass the vernatherm.  Amazing..  simply amazing.

So, $3 gasket later, oil temps are 40 degrees cooler.  You can do a max power climb as long as you want and never see much over 200.

  1. Scotty G
    Scotty G01-31-2011

    Points off to Superior.

  2. Hans

    Good day Sir,
    I have an angle valve IO360 in a RV 8 with a James plenum. I have changed oil coolers and changed the airflow and finally fitted a 13 row cooler with 4 inch scat tube from the plenum. The oil temp did not change one bit. I am sure I have the same problem as you had. The problem is I am on a contract abroad and I can only get to the aircraft in November. I simply can not sleep now. Well done for trouble shooting. Do you know how the wrong gaskets land up in there?. One more question, did you remove the old oil cooler or do you run both. I use two lightspeed ignitions and I think the advanced spark does not make things better. It would be great if you would drop me a note if you think I have the same problem.
    Best regards

    • admin

      No idea why the wrong gasket was originally used. I left the second oil cooler. I don’t need it for 99% of my flying. But, racing at Reno with very high RPM and very high OAT, the second cooler is a must. It is just enough cooling I don’t need a spray bar like many others have. Timing is very important and can very easily contribute to your problem. I’d start there actually, before I checked the case gasket.. Advanced timing can cause detonation, which causes very high temperatures in the cylinder. Angle valve motors spray oil on the piston from the bottom, this absorbs more heat to the oil than a parallel valve motor. Check your timing..

  3. Hans

    Hi Tom,
    Thank you for the fast response. I have done the timing thing up and down and I have spoken with Klaus from lightspeed many times. The cyl temps stay in 350 to 375 and the engine is very smooth . I also find that the oil runs hot even with a low power setting. The only way, is to run very rich mixture. By the way, my field is at 5000 vt and detonation should be less of a problem. I hear you and I am very mindfull of messing with timing. I run two lightspeed ignitions. So far I thought I was having an airflow problem through the cooler but nothing changes if I swop coolers etc. After your find, I am so hoping that I find the same.

    One more thing, do you think that it is possible to trap air in the top of an oil cooler with the hoses running from the lower area.? This debate is ongoing on the internet. I hope you dont mind all the questions but right now you are my best new friend.

    • admin

      Sorry I didn’t notice your reply till just now. Understand all of it. I think you are right, the next thing to check is your vernatherm / filter gasket area.

      As for the air bubble in the cooler. Uhhhh I doubt it. That has some pretty good pressure behind it, so I would think it would fill all the voids pretty quickly and push the air out. But… Neither of my coolers have fittings below the cooling body. Well, one does, but the oil exit is on the top, so it would push any air out. So, moral of the story, It is possible, but I doubt it. Email me a picture of your installation and that would speak a thousand words.


      • Hans

        Good day Tom,

        Great ! Will make up a bundle of photographs and send them over to you.

  4. Kelly

    Just recently found your site……Very informative………I do not have a race plane but my Dyke Delta
    has a angle valve Lyc IO-360 and will soon have a plenum cooling system like yours………I am also
    interested in where you sourced your second oil cooler………..It was listed on your site as a 15 row
    cooler and I have found a 13 row cooler from “Niagara” that might be enough cooling for my stock
    IO-360 but I would prefer to use just one large cooler if possible………

    Best Regards,

    • admin

      What I intended to mean is I have 15 rows total. A 9 row cooler in the front, and a 6 row cooler in the back. If there were a 15 row cooler, I don’t think it would fit anywhere firewall forward on my airplane. haha


  5. Kelly

    Thanks Tom for clarifying the cooler size issue……..You have a beautiful and very fast
    ship and your site is a treasure of tested cooling and drag improvements for any a/c……..

    I crewed for a friend who raced Formula One at Reno at Reno in the late 90’s………Great fun !!

    Happy Holidays,


  6. James

    What was the exact gasket (part number) that solved your problem?

    • admin

      James, I never did find an exact part number. There are many it turns out, from many sources. Just make sure the 2 important ports are not blocked in any way.