Trials and Tribulations of an Alternate Engine Installation
Anytime some guy thinks he can come up with a better mouse trap and create an engine installation that is somehow better than the certified engines that have been flying around for 60 years there are bound to be some bumps in the road. I mean really, how can one guy who is not even an engineer, create an installation that compares favorably with an end product that is the result of decades of effort from teams of professionals from competing companies, especially when the one guy has to also work a regular job and has no budget to work with? The situation is not really that bleak. The idea is to use an engine that is tried and true, and install it in accordance with accepted principals – making improvements where possible. But many components had to be designed and fabricated from scratch, and compomises had to be made. The rest of my website is mostly about the good, so here it comes: the bad and the ugly. Given in chronological order except for….
COOLING (the ugly) – Ah the grail of alternative engine installations. Even though I was able to fly off my initial 40 hours in less than 3 weeks (while also being a medical resident) and continue to fly for 200 hours with very acceptable performance (>200mph) with the original cooling installation, there is no doubt (looking back) that cooling caused me the most headaches. It was all fixed when I decided to do one simple and obvious thing – over build the cooling system and accept some additional drag penalty and do the work I knew it would take to mostly re-build the lower cowl. Nothing magic or difficult, I just needed to stop trying to compromise on cooling.
After mounting the engine on the airframe and fabricating the intake and exhaust manifolds, it became to mount the coolers. I have 3 coolers to mount: an intercooler to cool the intake air after it has been heated by the turbo, an oil cooler, and the water radiator. For years I had toyed with potential locations for each cooler, but finally settled on putting the smaller oil and intercooler behind the stock cowl inlets and mounting the radiator below the engine. The smaller coolers mounted rather well and have caused me little issue.
Final lay-out. On Left is Oil, Right is intercooler
Oil Cooler Intercooler
Oil cooling has always been more than adequate and I have actually slowly reduce the size of my oil cooler in order to decrease drag/weight and bring the oil temps up. I use a Setrab oil coolers and like time because the are readily available and come in a variety of sizes and fittings, and are not overly priced. (but beware of a recurring manufacturing defect as outlined under the oil leak section). My original cooler was 12x13x2” but I now use the 7x13x2” and still never get the oil over 190 in any condition. Cruse oil temps are below 160.
My intercooler is the stock Mazda ’91 intercooler that came with my
engine. It has worked out well,
being the compromise that it is. A
bigger, more efficient intercooler would be required if I wanted to run
significantly more boost, but this one is light, fits easily, is robust, and
keeps intake temps below 140 (usually well below that).
A Unique Cooling system
The
trouble came when I went to install my radiator. I decided on a 2-pass rad from C&R racing that was
22x20x2”. I would highly recommend
C&R as they will make a custom rad to exactly your specifications for about
the same price as an off the shelf rad.
The quality is top notch.
The problem came when I tried to locate the radiator. If I moved it back far enough so that
it would clear the cowl, it did not leave any space for exit air. If I moved it forward enough to leave
space for exit air, it protruded a couple inches outside the line of the lower
cowl up near the spinner. That
would have required extensive modifications to the lower cowl, which I was
hoping to avoid. I then came up
with the idea of sliding the radiator back so it would not disturb the cowl,
and let the air exit DOWN through the radiator after coming into the cowl
through the 2 stock inlets. On one
hand this greatly minimized the cooling drag and the fiberglass work I would have to do – it was no longer
necessary to even make an intake plenum for the radiator. I just needed to make a simple mod for
the outlet. The obvious downside
to this scheme was that the radiator would be getting second-hand cooling air. My thought was that the oil and
intercoolers had oversized inlets and would not heat the air more than 10-20
deg. I also would need to take
care to seal the cowl so that the air was forced down through the radiator and
didn’t leak out. In the end my
water cooling was marginal and somewhat limited my top speed and dramatically
limited my climb rate on hot days, especially if the engine was heat
soaked. Also, I am convinced that
continuously running at the high end of the temperature range led to my issues
with stuck side seals as described below, not to mention my dead-stick landing
(discussed in detail below). Here
is a picture of that early installation.
I guess you could call this the “ugly”
When
I was planning my installation all previously flying rotaries were having
problems with oil cooling but not the water cooling. This was despite what
seemed to be adequate airflow to the oil coolers (based on known heat load of
the oil). I decided that I would eliminate any possible oil cooling issue by
installing a large oil cooler and feed it plenty of fresh air (It worked - my
oil temps rarely get above 150F). Similarly, the intercooler fit nicely in the
left cowl cheek and also needed fresh cool air to be effective. Having located
the oil and inter-coolers in the cowl cheeks, the plan was to then mount the
large water radiator under the engine and have a separate inlet for water
cooling in the lower section of the cowl. Air would flow up through the
radiator, mix with the other cooling air and vent all together.. But when
trying to locate the exact location for the radiator, I realized that there
would then be no good location for the exit air
Original Cowl Intermediate Cowl
(the good) After the engine out, I decided to fix the cooling situation for good. I bit the bullet and made the bottom of the cowl from scratch, provided a large inlet and cowl flap, and increased the thickness of the radiator to 3”. The result is fantastic cooling. I keep the cowl flap closed all the time and never see coolant temps above 190 on hot days with steep full power climb-outs. Coolant temp is closer to 150 in normal use. The obvious downside is increased cooling drag, though it has not slowed the plane down any or made a noticeable dent in fuel efficiency. Here are some pictures of the latest installation
Final Cowl.
I am convinced the given the time I could come up with a very good design that would really minimize cooling drag. But there is no way I am going to mess with something that is working as well as it is working now.
Chronological list of problems and issues (the bad) –
Before first flight – would not circulate coolant. (early 2004) After discovering the joys of first engine start and some brief taxi testing, I quickly discovered that my coolant kept boiling over after a brief high power run. The coolant temp was not particularly hot, and the radiator was cool to the touch. I thought I might possibly not have enough space in my over-flow can, so I installed a larger one that did not fix the problem. I have no thermostat installed and there is a custom water pump housing that seals the return passage – so that was not the problem. Neither the radiator nor any of the hoses were plugged; so I blamed the water pump itself. I took it off and inspected it but could find nothing wrong but installed a different one any way – still no fix. One day I finally overheated the engine and was getting coolant in the combustion chamber so I had no choice but to take the engine off and tear it down. Low and behold the coolant passages in the iron housings had long since rusted shut. I had bought the engine ‘new’ about 1.5 years earlier from Dave Atkins and it did not appear to have any water in it at the time. It looked new from the outside. Perhaps it had been run with at the factory and no-one bothered to get out all the water. Anyway, Atkins denied any culpability and refused to provide any compensation at all. I was left with a good engine except for all the iron housings, which were scrap. I installed another ’91 turbo 13B that I had built up myself and it ran fine and the coolant circulated properly.
Coolant Passages Rusted Solid
Before first flight – smoke in the exhaust.(early 2004)- After fixing that issue I started doing some high power testing but discovered that not too long after start-up the exhaust would start to smoke. Oil could be found dripping around the turbine housing so that narrowed the culprit to the turbo. All the turbo makers call for a 0.5 inch or greater oil return line, but I had used AN-6 fittings and line because 1) they fit well and were easy to install and readily available, and 2) because the feed line was -4 and also had a restrictor so a -6 return line surely should have been large enough. The turbo itself was freshly re-built but I even sent it back for a second $600 re-build. But I still had the same problem. The solution was to increase the diameter of the return line to greater than ˝ inch with continuous descending flow. Apparently having just the slightest amount of blow-by will back-up that oil and make it spill past the bearing. I should have listened in the first place.
Before first flight – small coolant leaks everywhere. (May 2004) The same guy who welded up my alternator bracket also welded my water pump housing but left a bunch of pinholes in all the welds. Once found, that problem was fixed with a good cleaning followed by using a vacuum to suck JB weld into the holes. Has been working great for 320 hours. At this point you can imagine that I am really sick and tired of draining, refilling, and otherwise having anything to do with antifreeze!!!
JB Weld Sealing the Pinholes
Hour 5 – Alternator mounting bracket weld failed. (July 2004) I caught this one on pre-flight. The problem was both a faulty weld (almost no penetration – though done by a ‘professional’ welder) and bad design. The bracket shown in the picture now has re-enforcing gussets on both sides. The original did not have those and the long weld along the base failed. Would have led to an engine out if not caught on pre-flight. This is the ultimate example of problems that can really get you when you design and fabricate your own parts.
Alternator Bracket now with gussets on both sides (4 days after first flight)
Hour 50 – leaking oil cooler. (Sept. 2004) Around hour 45 a small oil leak sprang up that I could not find until about hour 50 when it got bad enough to trace to the oil cooler. At the time I blamed poor installation that allowed some vibration and stress on the oil cooler mounting flange. I designed a better mount and in put in a new oil cooler (which was also smaller). It developed a leak in the same spot at hour 200, so I put in a 3rd cooler (smaller still) and reduced the weight of the oil lines. But that cooler leaked again right away from the SAME spot. I tore apart the second cooler and found what appeared to be bad brazing between the core and the end chamber. The 3rd cooler appeared to have no brazing in that area. I called the company but they didn’t believe me. I sealed the area with JB weld, which has held fine for 125 flight hours so far. I keep a close eye on that one.
Exact same location and defect found on 3 coolers (even brand new one)
Hour 70 – failed turbine wheel. (October 2004) There I was, inverted, over the Grand Canyon and having a ball. Anne and I were headed back to San Diego flying westbound at a ground speed of 194 KTS at 14’000 when the MAP suddenly dropped from 33” to 17”. We landed at a local airport and eventually found a broken turbine wheel to be the problem: I attributed it to overspeeding of the stock (series 5) T3 turbine in a high heat environment. I simply blocked off the oil feed to the turbo and flew for the next 70 hours normally aspirated until I could find a replacement turbo. Coming soon (well, someday anyway) is a separate page about turbo selection. I have since installed an electrically actuated valve where-by I can shut off oil to the turbo in flight and continue flying normally aspirated if needed.
Beaten and Battered Turbine Wheel as found
Hour 140 – failed relay in EFI
computer and broken PSRU. (July 2005)
One day during normal run-up for take off I switched from Computer A to
Computer B and the engine began to miss, stumble and backfire. I switched back to computer A for the
taxi back from the run-up area.
During further testing the problem continued intermittently and I also
began to notice that I required a lot of RPM to taxi around. Inspection showed that the prop was now
free-wheeling from the engine. It
turns out that a relay had failed in the EC2 ignition controller, and the
backfires had broken the rosette welds holding the input shaft to the sun gear
in the RD-1B gear drive (both items from Tracy Crook and Real World Solutions).
Rosette Weld between Sun Gear and Input Shaft that failed due to backfire
Hour 150 – Stuck and broken Side seal. (Sept. 2005) Not long after finally getting the plane back in the air after the failed PSRU, we discovered oil coming out the side of the cowl that had apparently come out the blow-by tube (that had blow off the attached diversion line). The turbo was also loosing oil into the exhaust again. There was a palpable loss of compression in at least 2 faces of one of the rotors. Once again I commenced to remove and tear down the engine. That revealed the problem as a stuck and broken side seal. At the time I chalked it up to just bad luck, or possibly detonation, and I re-built the engine (I can re-build the engine myself in a day for about $600 in parts). Looking back, this was probably the first case where my continuous tolerance of near maximal coolant temps caused a problem. The seal was caked in oil grime and broken. The oil grime may have been due to excessive temps. Or more likely, high temperatures had caused detonation that had broken the seal. Then leaking combustion gasses caused the oil grime. I had been experiencing a sudden dip in power at high power settings. At the time I thought it was turbo surge but I should have recognized it as detonation because the MAP at which it occurred was inversely related to the coolant temperatures. Coolant temps should not affect turbo “surge” (compressor stall). It used to be quite easy to get into detonation, but now that my cooling system is more robust it has only occurred in the highest boost (over 38”) and hottest days and only when I forget to enrich the mixture.
Stuck and broken Side Seal due to detonation (probably)
Hour 160 – cracked AN-6 aluminum
coolant line (Dec 2005). On
the way to Mammoth one day we started to smell coolant so landed at
Hour 165 - Same coolant line cracked in same place. (Jan.
2005) This time while on a
formation flight at
Hour 180 – Frozen/cracked radiator followed by in flight loss of coolant and dead-stick landing on a highway (Feb 2006) Basically more follies from pushing the limits of a cooling system that was less than I wanted. This one is so good it gets its own web page… Coming Soon.
Removing Wings at Bishop for trip back to San Diego
Hour 215 – Excessive thrust bearing
wear on PSRU. (Oct 2007)
Hour 216 – The second and third oil coolers produce leaks (Nov 2007) This one was described above.
Hour 270 – Second Turbo gives up the
ghost (June 2008) I was
pushing it a little harder than usual to get to Brownwood TX for a formation
clinic and the second turbo decided it had done enough. This turbo was properly sized, and I
attribute the failure to high heat from running continuously at peak EGT (will
stop doing that – the engine can tolerate it fine, but I guess the turbine
wheel no-like). I couldn’t keep up
with the formation guys with a turbine wheel stuck in the housing, but at least
I could just flip the turbo oil shut-off switch and fly home from
Hour 285 – Burned exhaust hole through the cowl. (July 2008) The new turbo shows up and I install it but somehow failed to properly install the exhaust flex line. That allowed an exhaust leak which burned a hole through the cowl. Oh well, its only fiberglass work eh? Yuck!
That covers all the major issues that have anything to do with the engine or its systems. Seems like a lot, and I am sure there will be more. But since the major overhaul of the engine and systems, they seem to be getting fewer and further between as well as less serious and easier to deal with. I am still glad I installed the rotary, would probably do it again if I build another plane (now that I have learned most of my lessons).
The Hobbs stands at: 320 hours as of Sept. 2008.
Worth Every Moment – Note the Islands: Catalina, Santa Barbara, and even San Nicholas Island that is more than 100mi. away. Picture taken from Above El Toro at 14,000ft on the way to Mammoth.
