Comparing Engine Weights

Dj Merrill

Original Study Mar 2009

Last Update 05 Apr 2009

I've decided to perform an academic excercise to compare the complete firewall forward weight of the E6 3.0 Subaru package for a Sportsman to a Lycoming installation that might also be installed in a Sportsman.

I'm trying to be as scientific as possible, meaning that the data points I am willing to look at are those that are measured from an actual scale, or that are weights provided by a manufacturer's spec sheet or similar. In other words, "I think it weighs about 3 lbs" isn't good enough. There are far too many guesses when it comes to this topic to make that kind of data useful.

An O-360 A1F6 complete FWF installation, including prop, fluids, baffling, exhaust, etc. pulled from Frank Minnick's Sportsman was weighed at 474 lbs on a set of scales.

In an attempt to validate the accuracy of the 474 lb weight, I've created a list of items that are a part of a typical Lycoming installation, along with weights and references. Please let me know if I've forgotten anything. If you have references with weights of items that I am missing, I'd greatly appreciate it if you would send them to me.

According to Lycoming, the IO-360-A series of engines have dry weights not including accessories from 324 to 335 lbs

Sportsman engine mount - 9.5 lb not including the nuts and bolts - Harry Delong, Glasair Aviation, scale

engine rubber shock mounts - 1 lb each, 4 lbs total - Barry Mounts, Omar Filipovic, scale

engine rubber shock mounting bolts -

oil cooler - 2.65 lbs - Dustin Paulson, Positech Model 4211, scale

oil hoses -

starter - 9.4 lbs - Skytec High Torque, Aircraft Spruce website

alternator - 8.5 lbs - B and C 60 Amp

gascolator - 0.5 lbs - ACS, Aircraft Spruce Website

fuel pump -

fuel pump cooling shroud -

boost pump -

fuel hoses -

fuel injection servo - 5.25 lbs - Precision Airmotive SilverHawk website

mags - 3.75 lbs each (times 2 = 7.5 lbs) - Slick brand, Aircraft Spruce website

spark plugs - 0.26 lbs times 8 = 2.08 lbs - Champion REM40E, scale

spark plug wires -

air intake -

air filter assembly - 1 lb - Brackett BA-100 or BA-101, Aircraft Spruce website

air filter hoses -

engine cooling baffles -

exhaust system - 9.75 lbs - Dustin Paulson, Crossover Exhaust made by Larry Vetterman (per phone conversation with Larry)

cabin heat muff - 1.2 lbs - Homebuilder's Heat Muffs, Aircraft Spruce website

vacuum pump - 2.5 lbs - Sigma Tek Model 1U128B, scale

vacuum pump hoses -

scat hoses -

miscellaneous clamps (scat, fuel, oil hoses, etc) -

electrical wiring (starter, alternator, mags, etc) -

oil - 2 lbs per quart times 8 quarts totals 16 lbs - Aeroshell 15w-50, scale

hydraulic governor - 2.16 lbs - Dustin Paulson, Czech Governor, installation manual

constant speed prop - 55.4 lbs - Hartzell HCC2YK-1BF/F7666A-2/SM8, Glasair Aviation web site

prop extension -

Total of calculated weight: 460.39 to 472.39 lbs not including the dozen or more items I don't yet have weights for in the above list.

As we can see, even though we do not have weights for all of the FWF items, the calculated weight of the entire FWF package is already getting close to that of an actual installation that was weighed on scales (within 14 lbs). Based on this, I believe the 474 lbs to be an accurate representation of one example of a complete FWF Lycoming installation on a Sportsman. I'd still like to fill in the rest of the data, so please let me know if you can help with references for any of the missing weight information.

My local EAA Chapter 87 recently purchased a set of aircraft scales. With the help of my friend Leo Leclair, we weighed the complete FWF Subaru package.

Engine package weight: 435 lbs (436 lbs minus 1 lb for the straps)
This includes: coolant (NPG+), coolant radiators, coolant reservoir tank, coolant hoses, gearbox (PSRU), engine mount, engine rubber shock mounts and mounting bolts, oil cooler, oil hoses, starter, alternator, fuel hoses, fuel injection, electronic ignition, spark plugs, spark plug wires, exhaust system - everything you see in the pictures

Ivoprop Magnum 3 blade prop - 26.7 lbs -

Oil - 2 lbs per quart times 6 quarts totals 12 lbs

SDS ECU (Gold Box) - 1.12 lbs - scale

Andair firewall fuel filter (gascolator functional equivalent) - 0.25 lbs - scale

air filter bracket - 0.93 lbs - scale

air filter - 0.56 lbs - scale

Total: 476.56 lbs

The complete FWF installed weight of the 2009 E6 Eggenfellner Subaru engine package for a Sportsman is nearly identical to that of a Lycoming O-360 A1F6 complete FWF installation that was installed in a Sportsman, at a difference of two and a half pounds (2.5 lbs).

Is it possible to build a Lycoming installation lighter than the E6 Subaru installation? Is it possible to build a Lycoming installation heavier than the E6 Subaru installation? The answer to both of these questions is yes.

The data suggests that the complete E6 Subaru installation falls within the same weight range as a Lycoming installation, and does not appear to be "grossly overweight" as some people claim. Hopefully the data shown above will help to dispel those myths.