My AC-Aero LIO390 engine uses liquid cooling rather than air cooling. Here’s the way I’ve done it.
The numbers are in, 38lbs 3.1ozs (say 38lbs) for all the extra cooling gear including the fluids. The engine came in at 259lbs dry weight (10lbs more than an 0-235L2C) Final engine weight 297lbs for my 255HP.
Hose sizes
Ideally after pump 2 it would be all AN-16 back to the engine but I didn’t have room. They are all Speedflow fittings and hoses.
Heat Exchanger
This is for the oil cooling so I’m using the coolant rather than an air cooler here
Expansion Tank and Overflow bottle
This might be overkill for some installs. I wanted to get a bigger tank volume and keep coolant in the system if I get too hot rather than venting overboard. We will see if this is OK with testing.
Sensors
One for each side just after exiting the engine (hottest) one just before returning after the radiators and pumps going to the bottom of the engine. I’m looking for a DeltaT of 16C or better. The other temp sensor on the RHS is to drive the pumps and fans via a controller. The pressure sensor will tell me if I loose too much pressure due to a leak or pump failure etc.
Fittings and Hoses
I used the best I could buy, all AN. You could go lighter and cheaper.
Pumps
These are Davis Craig (automotive) plumbed in series. One works from the controller and the other just has a manual on/off for backup and boost if required.
RADIATORS
How big do they have to be? Good question! …
These are as big as would fit. That’s my rule of thumb! They can always be made smaller if there is too much cooling. In my pusher configuration Long-EZ, keeping the engine happy is always a challenge and the room available under the cowl is minimal at best.
Lets do the numbers on what I have:-
LHS Radiator 18.7″ X 5.9″ X 2.65″ thick = 110.33sq” facing and 292.37cubic”
RHS Radiator 16.5″ X 5.9″ X 2.65″ thick = 97.35sq” facing and 257.97cubic”
Totals 207.68sq” and 550.34cubic” The PWR cores are a special high performance product. Using those, the tanks and lengths were custom made for my plane.
Here are some thoughts from the engine builder:-
1). 1 Horsepower = 2544.43 BTU/hr or 42.4 BTU/min.One Btu is the amount of heat required to raise one pound of water by one degree Fahrenheit. …
2). Roughly 1/3 of an engine’s BTUs ends up in the cooling system
3). Therefore, roughly 14.12 BTU/min per HP ends up in the cooling system.(42.4/3=14.12BTU/min HP)
4). This is where it gets even sketchier yet – In a single row efficient aluminium radiator, each cubic inch will cool approximately 11 BTUs (therefore, BTU/11 = approximate cubic inch of single row radiator).
5). Assuming that your single row radiator is 2” thick, then each sq in of radiator frontal area would cool approximately 22 BTUs (therefore, BTU / 22 = approximate sq in of single row radiator).
6). Approx BTU requirements 300HP X 42.4 BTU/min X 1/3 = 4,236 BTU/min.
We need 4236BTU a minute with a 2″ thick radiator we get /22 = 192square inches needed
OK, My engine made 255HP on the test stand so thats 255X 42.4BTU/min X 1/3 = 3604 BTU/min
If need to cool 3604BTU/min with a 2″ radiator (mine is 2.65″) we find /22 = 163.8square inches needed
We have 207.68sq” Happy days! ……or is it? Being a pusher and these numbers also being a bit of a wild guess really, we will see during the test flight program if it’s enough. Different websites I’ve been on have different numbers and estimates of what is needed to cool a given amount of HorsePower. Good luck with your estimates and if you have a better way to calculate all this I’d be pleased to update this page.
WHAT DOES ALL THIS WEIGH?
People keep asking, “How much extra weight does the liquid cooling add?” I’m guessing between 20 and 30 pounds? That’s a terrible answer!
Lets start with what we know. The engine was weighed when it was built, I have a picture!
This is 259lbs with both alternators, starter, flywheel, EFII fuel system and wiring, the ‘dry weight’. The Lycoming 0-235L2C, which the Long-EZ was designed for, is 249lbs dry. So 290lbs is what it will be with the water cooling systems or a bit less is a fair guess.
For comparison:-
AC-Aero LIO-390 255 290
Lycoming Engines HP lbs
| IO-320-B1A | 160 | 285 |
| O-360-A | 180 | 285 |
| IO-360-A | 200 | 324 |
| O-360-A1D | 180 | 284 |
| O-360-A3A | 180 | 285 |
| IO-360-A1A | 200 | 320 |
| IO-360-B1B | 180 | 299 |
This page is also for documenting the weight of components, so we really know. I’ll keep updating as I go until we arrive just before the first start of my cooling system. That’s when I see if any water leaks out before starting the engine! The last piece of the weight puzzle will be when I put the nice green liquid coolant in.
Lets start with the two water pumps that live in the hellhole. Davis Craig EPW150 pumps. These weigh in at 2lbs 10.7oz each. One has the controller system which covers the pump and my fans. They are rated at 162liters per minute each.
5lbs 5.4 ozs Total so far… 5lbs 5.4ozs (I’ll keep a running total)
OK This is a really interesting one. I’m using a water to oil heat exchanger instead of an air cooled radiator. The model is a Laminova ECD54-250. It is double core and biggest one I could fit. Bigger is better here. The suppliers tweak the unit for your particular installation and have a wealth of technical knowledge.
This weighs in at 3lbs 15.8ozs. The radiator I WAS going to use weights in at 4lbs 3ozs. So would you agree that this is no change really from air cooled to liquid cooled for the oil? I am not going to count the nearly 4lbs in the extras from liquid cooling totals here.
This is the Left hand side (LHS) radiator with fittings and its duct so thats pretty close to the final weight. I am adding a couple of nutplates and the AN3 bolts. Since this pic I’ve remade the duct, twice. How pedantic do I need to be? The radiators were custom built to fit by Race Radiators here in Melbourne (Australia)
5lbs 2.3oz LHS Radiator raw This makes 10lbs 7.7ozs (running total)
The LHS (left hand side) radiator was finally ready last month (April 24) with the overflow tank.
With the duct and tabs and brackets added we have:-
6lbs 0.9ozs (its slightly bigger than the RHS) So thats 16lbs 8.6ozs (running total)
Here’s the expansion tank and its pressure sensor. The tank was just an internet purchase that fits some car and was the right size for my plane. It was well made and seriously altered by my radiator guy to fit my needs. Did I say I have a lack of space under the cowl?
1lb 12.5ozs So thats 18lbs 5.4ozs (running total)
Next up is this Y fitting and the hoses and that sensor.
1lb 9.8ozs So thats 19lbs 12.2ozs (running total)
This is the sealant I used for the sensors, Loxeal 58-11. To my surprise Loctite 567 was the source of leaks in NPT threads. 58-11 fixed it and I used it on the injectors as well.
Here’s the -12 hose from the outlet of the pumps to the Laminova heat exchanger.
8.7ozs That’s 20lbs 4.9ozs (running total)
The two radiators has SS supports. This one was 1.5ozs. I worked out that I have 6ozs total with 6 lengths of the stuff including two really stubby ones. Then I worked out the weight of the nuts and little bits of 90 degree brackets and came up with 2.4ozs.
8.4ozs That’s 20lbs 13.2ozs (running total)
This big -16 top hose came in at 11.2ozs and I have a second one on the other side almost the same weight. So thats 1lb 5.4ozs together.
That’s 22lbs 2.6ozs (running total)
Here’s the overflow bottle and bracket, 5.8ozs. There are a couple more things that go with this. The lower bracket and a bit of rubber hose. I’ll add them later as miscellaneous. The square bottle is a Rotax part. Probably almost anything would be fine. You just have to have it heat resistant and fit your plane.
That’s now 22lbs 8.4ozs (running total)
This is the last pipe to weight. Its AN-16 so we have big fittings. 9.1 ozs
We are up to 23lbs 1.5ozs (running total)
Here are the final two items before the ‘water’. Yes, being a pusher configuration I am using two fans, one for each radiator. This is to add to my cooling if I’m stuck on the ground for protracted periods. The fan and fasteners and the brackets I’ve made come in at 1lb 0.8ozs Both fans would be 2lbs 1.6ozs.
We are up to 25lbs 3.1ozs (for our running total).
The last item will be the weight of the coolant water. I put 5 Liters in but just under 6lts will make it full. That’s 13lbs or about 6 kilos
We are up to 38lbs 3.1ozs (for final total).
With one radiator and bayonet fittings where is probably a good 5lb saving or more to be had. Another two pounds for the fans that might not even be necessary. I have the dual electric pumps, dual radiators and the best quality AN fittings I could get. I ditched all the stuff (that I paid a lot for) that came with the engine. They just didn’t feel right and I suspect they were very cheaply made. The threads just didn’t seem to do up easily on the fittings and when I needed more hose it was not compatible with what was available here in Australia. All my water system hoses and fittings are Speedflow. Quality was not cheap.