Modifications: Bigger oil cooler for IO-390-EXP119, try #2 (inadequate performance).

TLDR:  Oil temp was too high with EXP119 engine.  Installed larger 2007X, which failed in flight.  So I tried the Aero-Classics 8001652.  Read on to learn all the details, but keep in mind that the cooler described in this post was inadequate.  See the three other posts below, including the last post where I successfully tried the larger 8001643 with a more deliberately designed duct and oil cooler tray with integrated exit diffuser.

My "larger oil cooler" series:

• Initial larger oil cooler, 2007X.
• Airflow Systems 2007X oil cooler in-flight failure after 75.9 hours.
• Second larger oil cooler, Aero-Classics 8001652, which was inadequate (the post you're reading now).
• Third larger oil cooler, Aero-Classics 8001643, which is satisfactory.

Recall that I increased the size of my cooler from the 2006X to the 2007X since my oil temperature was prohibitively too high in the summer.  But why is this my second attempt at a larger cooler?  Because my "Airflow Systems oil cooler failed in flight".  So for try #2, I decided to use a different manufacturer's oil cooler.  

But first, the final result of this second larger oil cooler installation is shown below.  Then I'll get into some of the details.  For all of the details on why a larger oil cooler was needed, see the post that outlined the first larger cooler's installation.

The image on the left below shows Vans' stock oil cooler duct whilst the image on the right shows the duct I designed. 

Now let's get into some of the details on this second larger cooler installation.

I spoke with Aero Classics and opted to try the HE 8001652 (the "HE" is for "high efficiency"), a PMA'd cooler with a core dimension of 6"x6.29" and depth of 3.2" for $1,285.  Aero Classic's sentiment was that I should see a 10 - 15% increase in performance over the 2007X.  Even if it was 10% - 15% less, I was confident it would be sufficient for my needs.  The Aero Classics cooler has 3.5 square inches more cross-sectional area across the core (10% more) and about 3 cubic inches less volume in the core (2.5% less).  The Aero Classics engineer also believes their cooler has a better sealing interface to mitigate leakage around the core.

You can read more about the selection of that cooler and a poor-man's comparison of the 8001652 against the failed 2007X cooler towards the bottom of this post.

Here is the HE 8001652 (silver) next to the failed 2007X (gold).  Immediately, you can see difference between Airflow Systems' "drawn cup" design on their failed cooler and the "bar and plate" design on the Aero Classics cooler.  If the Aero Classics cooler fails, it won't be from a seam ripping open like what happened on the failed Airflow Systems cooler.  KitPlanes has a great article about different cooler designs.  The fins are very fragile and can be bent with the slightest touch.  Keep a toothpick handy to straighten out any fins that get upset.  The rows are also wider than the failed 2007X.

Since the HE 8001652 has slightly different dimensions than the failed 2007X, I needed to update my OnShape CAD models for the tray and duct.  Here is the model of all three (tray, cooler, duct) stacked together.  I ultimately removed the hole on the right support angle in the model in favor of match drilling.

Here's the new tray in place during final fitment.  Cost was $61.58 shipped from SendCutSend.  I then primed and riveted it together.  The image on the left shows initial placement.  The image on the right show how I setup to match drill the right support angle:  First, a 1.5" angle was fabricated from 0.063" 5052 aluminum and a #12 hole drilled on one side.  Next, a 0.058"x0.3125" T6 aluminum was cut to 0.6" to fabricate the spacer.  An NAS1149F0363P and NAS1149F0463P washer were place on either side of the spacer.  A #12 bit was passed through the hole and twisted enough to score the right support angle so that the hole could be then precisely located and drilled.

Here is the final try in place.  I got it (side-to-side) level to 0.4° degrees.

Here is the cooler in place with p-seals adhered.  Note that the outflow hose is shown fastened to the engine mount with two Adel clamps.  I ultimately removed those to ensure that the hose can offer up its slack when the engine moves during startup and shutdown.  You can also see the intake hose coming straight in to the cooler behind an engine mount support.  This was a custom length hose I had fabricated to try to mitigate vibration being transmitted into the cooler.  I discarded this approach as this hose had no slack to accommodate engine shake on startup and shutdown (see video in this post that shows just how significant this shaking is).

Below is the aluminum duct prior to priming for installation.   On my original design for the failed Airflow Systems 2007X cooler, I had the duct printed at 0.0625" thickness with the cooler flange at 0.125".  That was overkill and cost $314 shipped last year from CraftCloud.  The time around, I had the duct printed for this cooler at 0.04" thickness and 0.0625" at the flange.  This was $172.48 shipped, again using CraftCloud.  

As I discussed in the post outlining the failure of the Airflow Systems 2007X oil cooler, one of the items I was concerned about was the angle that the intake hose took to come in to the cooler.  Vibration from that hose may have exposed a vulnerable part of the "drawn cup" oil cooler design.  So I had FF-00020-1 fabricated at an inch shorter ($204.13 shipped from Aircraft Specialty) to account for the new cooler sitting further inboard than the stock cooler position.  This would reduce the torquing of the fitting by the hose.

The inflow hose fitting is at 90 degrees pointed forward.  As a reminder, always use steel fittings on aluminum to prevent galling (AN822-8), despite what the Van's plans say.  Here is what the fittings look like on the cooler (when installed, this would be the inboard side of the cooler). 

Here I show the intake hose going in to the cooler.

The outflow hose could be rerouted to come in from the top using a 90 degree elbow fitting clocked at 12 degrees clockwise.  With this configuration, the oil cooler won't twist and does not want to translate in any direction when it isn't bolted down.  Thus, the outflow hose is perfectly situated. 

Here is the aluminum duct in place where you can also see the outflow placement.  Again, note that the outflow hose is shown fastened to the engine mount with two Adel clamps, which were ultimately removed.

Final installation shown below.  Maybe this coming winter I'll design a carbon fiber transition duct from the baffle so that a straight section of SCEET tubing can be used.

Turns out that this cooler was horribly inadequate, yielding a cruise OilT of 223°F at an OAT of 85°F and a peak OilT of 230°F at an OAT of 86°F in a low power descent!  So I dispensed with this cooler and set out on my third attempt at finding a satisfactory cooler.  It's worth noting that Aero-Classics would offer me only about $150 in credit to exchange this cooler.

Cost comparisons: 

Aero-Classics 8001652:

• Cooler:   $1,285.00
• Tray: $61.58 +  $3.42 (nutplates)
• Duct:  $172.48
• Hose: $204.13
• Total:   $1,726.61

 Van's 2006X (as of 27-Jul-25):

• Cooler:  $940.82 (EA00002/2006X)
• Tray parts:   $35.40 (FF-01404A, FF-01404)
• Duct:  $135.25 (FF-01406E, FF-01406C)
• Hose:   $258.24 (FF-00020-1)
• Total:   $1,369.71

Avionics: New indicator lights circuit board.

I decided to preemptively replace my Plane Power AL12-EI60 alternator at 513 hours.  It whines like a coyote whereas my backup B&C BC410-H is as quiet as a mouse.  Late last year, B&C released the SF601 internally regulated alternator which is what I went with.  

That new B&C alternator doesn't have an indicator output so I redesigned my indicator circuit board to make the ALT indicator a low voltage light and also made each flight flash when they are enabled (other than the pitot heat light, because that would be annoying) to help grab my attention.  The new board also uses quick-connect tabs to make servicing it easier and it has less exposed trace area.  And since the ALT light is now a low voltage light, I won't need that tiny circuit board I made to ensure the ALT light always indicated the status of which of the two alternators was selected.

Here's what the new board looks like in CAD (easier to make out the details with the CAD rendering than with an actual image of the board).  The other side of the board attaches to the LEDs and indicator test push button.  After I soldered it up, I sealed it with lacquer.

The following schematic outlines what I designed.  A 555 timer is used for a T_On of ~0.7 s and a T_Off of ~0.3 s.  Since the 555 can't source much current, it controls a high side PFET which connects and disconnects +12 V from the LEDs in concert with the 555's Q output.  The Canopy Open and Oil Pressure LEDs will thus blink when enabled (active low). 

Q2's base is pulled high by the PFET output which normally enables the ALT LED.  But a 13 V Zener diode with a few resistors will break down above about 13.7 V, causing Q1 to turn on which turns off Q2, which shuts off the ALT light.  Thus the ALT light will be off when the main bus voltage is about 13.7 V and higher and blinking when it's lower than 13.7 V, indicating a low voltage situation on the main bus.

A 1 μF bypass cap on the power input was necessary to clean up the 555's output.  And a 3.3 μF cap was necessary across the ALT LED since when the PFET turns off, the LEDs' power line drops below 13.7 V, causing a dim and momentary flash on the ALT LED even when the bus voltage is higher than 13.7 V.  That 3.3 μF cap across the ALT LED holds the voltage high enough for long enough during the T_Off phase that the LED won't briefly try to turn on.  Since it's only 3.3 μF, it doesn't cause the ALT LED to fade off when being illuminated.  Capacitors across the Canopy Open and Oil Pressure LEDs aren't necessary since when they are not illuminated, their cathodes are floating so there is no current path available.

As before, an "indicator test" input will momentarily turn on all LEDs to verify they work.  This would cause the Oil Pressure, Canopy Open and ALT LEDs to flash and the Pitot Heat light to turn on solid.

Video showing canopy being locked/unlocked with lights flashing.

Circuit board parts list:

• 555 timer:  Texas Instruments SE555DR
• Capacitor 3.3 μF:  Nichicon UVR2A3R3MDD
• Capacitor 1 μF:  Nichicon UPX1V010MPD
• Diodes:  Kyocera AVX SD1206S040S2R0
• PFET:  Infineon Technologies:  IPP120P04P4L03AKSA2
• Quick connect tab, 0.25":  Keystone Electronics 4902
• Resistor 4.7 k:  Panasonic Electronic Components ERJ-8GEYJ472V
• Resistor 10 k:  Panasonic Electronic Components ERJ-8GEYJ103V
• Resistor 270:  Panasonic Electronic Components ERJ-8GEYJ271V
• Transistor:  onsemi MMBT2222ALT1G
• Zener 13 V:  Microchip Technology 2EZ13D5

Avionics: Oil quantity sensor installed.

Following my experience with the failed Airflow Systems 2007X cooler, I wanted to have an indication of how much oil was in the sump during flight.  Aircraft Extras makes just such a product.  The sensor, contained in a tube welded to a fitting, is placed in an unused drain plug.  The sensor wires are routed through the firewall into the electronics box which, following calibration by the user (filling an empty sump with a series of known increments of oil), in my case connects to my EFIS for display of the oil quantity.  I also got the optional temperature sensor since...well...why not?  

Below is an image of the sensor as delivered for my engine (Lycoming IO-390-EXP119) and the electronics box (pic from Aircraft Extras).  The design of this sensor is exceptional and seemingly all possible use cases were thought of by Aircraft Extras.  E.g., separate indicator lights (if not used in conjunction with an EFIS) can be accommodated and a remote programming button is supported should the electronics box be mounted in an inaccessible location.

To order the sensor, one needs to make a measurement to determine what length sensor is appropriate for the engine.  Below shows the oil plugs for my engine (IO-390-C/EXP119) looking up at the sump where the top of the figure is the aft side (taken from the Lycoming maintenance manual, MM-IO-390-C Series, page 72-20).  The oil drain plug is circled in red whereas the right forward plug is circled in green.  For reference, my sump is Lycoming part 56B28511.

 

 

Below left is an image of my sump before it was installed (from back when I changed my engine to the -EXP119 variant) and the right shows the engine without the sump.  Based on these two images, it seemed reasonable that the right forward drain plug would capture a significant volume of oil via the sensor (the plug next to the oil screen, the lowest spot on the sump, is used for draining and is thus unavailable).  I measured 4 and 5/16" from the bottom of the sump to the ceiling.  Thus my sensor length was 4.065"  and I thought 60" length cables were appropriate for my installation. This yields Aircraft Extras part S4.06-1/2NPT-C60.  

Below shows the sensor installed.  I added heat shields along the two nearest exhaust tubes (only one of which is visible) to help deflect heat away from the coax.

I calibrated the sensor using 0.5 quart increments up to the max of 7 quarts.  Following calibration, my sensor output about 4.2 V (out of 5 V possible) at 7 quarts.  Obviously, that's not the full 5 V output.  So using a 7/5 scaling, that translates to about a maximum of 5.9 quarts readable (i.e., the remaining 1.1 quarts were above the top of the sensor and not available for measurement).  That's great since I don't usually fill beyond 6 quarts so I would be able to see a meaningful reduction in oil in flight (however, read the last paragraph below to understand how to interpret the sensor's indication in flight).  On my next oil change, I'll recalibrate the sensor up to a 6 quart max so the sensor output has more resolution.

My panel just doesn't have space to mount the electronics box anywhere other than in the map box cutout.  It wasn't practical to use screws, so I cinched it down with wire ties to the SkyRadar mount (which is now a Stratux mount).   After this image was taken, I used a pair of right-angle SMA adapters to better route the coaxes.  I didn't have the right tool to cleanly crimp the sleeves on the connectors, so the former look a little flat.  If you're curious why there's a USB power socket adjacent to the electronics box, go here.

Wiring map for the electronics box is below.  It shares its power by connecting to my Aircraft Extras Fuel Guardian and thus is protected by that 1 A fuse (which also powers my CO Guardian).  The sensor is configured to have 0-5 V outputs for both outputs with 0-300 °F scaling for the temperature output.

Here is an image from my EFIS in flight showing the sump temperature and oil quantity (bottom right two meters).  It's interesting that the sump temperature (where oil collects before the oil cooler) shows only a few degrees higher than at the oil cooler exit.  I would have expected a larger temperature difference between the two locations.  However, these sensors may not have similar accuracies.  An explanation for the oil quantity indicating lower than actual follows.

Here is a graph from a flight showing the oil pressure, oil quantity and sump temperature.  The x-axis is the time in minutes since start.  It's interesting any time the OilP goes up, the oil quantity goes down.  I think this is because at high OilP there is a high volume of oil moving out of the sump.  Thus, the oil may not have enough time to settle and collect at the front of the sump (where the sensor is) before the oil pump pulls it through the screen (I presume high OilP translates to a high volume of oil moving).  

Thus, in my case, the sensor always gives an artificially low number when the engine is running and as power increases, the indicated oil quantity is reduced accordingly.  I have the EFIS "low oil" alarm set to 3 quarts for now (which translates to maybe 5.6 quarts of actual volume in flight).  I will experiment with that setting over time to get me an active alarm around 5 quarts of actual volume in the engine in flight.