About the LS3
LS3 Engine Information
LS3 Percentage of Power
The common misconception is that automotive engines are not designed to run at 90-100% power for extended periods of time. The fact is automotive engines are never operated near 100% power in an aircraft application. The operation of automotive engines in an aircraft is similar to that in a car, as seen with how the LS3 is operated.
The LS3 Chevrolet engine has 430 HP at 5900 RPM. When used in an experimental aircraft the most horse power we recommend is 367 HP at 4500 rpm for takeoff. Throttling back to a high cruise setting RPM of 3400 is about 270 HP of the available 430. A low cruise setting of 2800 RPM is only 187 HP. This constitutes conservative use of the engine, extending engine life and offering exceptional fuel economy. Operating the LS3 at slightly higher engine RPM can be done successfully, however higher engine RPM will increase fuel burn with very little gains in performance, and push the propeller to its RPM limits. It would then be left to the pilot’s personal preference to determine if the additional fuel burn is worth the negligible improvements in performance, increased, costs, risk, and maintenance.
Using the LS3 in this conservative way affords us a large portion of reserve power when used in aircraft. Compare this to traditional aircraft engines which typically operate at or near 100% power. LS3 engines also offer 30% better fuel burn vs IO-540 as proven in April 2011 during a head to head fly off between two Raven 500 aircraft, one with an IO-540 and the other with an LS1, conducted by Rick Lundstrom.
The engine operating range that we recommend for the Chevrolet LS3 for the best performance and fuel burn is between 2800 (187 HP) and 4500 RPM (367 HP), therefore we refer to 4500 RPM as our 100% power setting. This simply means that 4500 RPM is the top of the power range we use of the available power we have, leaving more HP in reserve.
But Isn't the LS3 Heavier Than an Airplane Engine?
The answer is NO. GM lists the 6.2L Chevrolet LS3 engine as weighing in at 411 lbs right out of the crate. We remove the cast iron exhaust manifolds and other accessories not utilized in aeromotive application and end up with an engine weighing 376 lbs. Once we add our engine mount, ECU and harness, radiators and all accessories, PSRU, oil and water, we end up with a ready to fly weight of between 489-493 lbs depending on the airframe application.
We have weighed an Eggenfellner six cylinder turbo right off the airplane on certified aircraft scales, also ready to fly, at 510 lbs.
Most IO-540's out weight the LS3 FWF package by 22 to 30 pounds. At take-off power the LS3 produces 20% more HP and torque at the propeller flange than the IO-540. This higher torque equates to higher propeller pitch angles and more thrust which equals faster climb and higher air speeds, all while burning less fuel.
In fact, most certified manufacturers will not even tell you how much torque is actually applied at the prop, but it can be calculated from the HP and RPM. The Auto PSRU's LS3 FWF engine package delivers over 716 ft lbs of torque and 367 HP to the prop at 4500 RPM for take off, and at a cruise of 3400 RPM it produces 657 ft lbs of torque and 273 HP. Check out the nearly flat torque curve on this engine in the link above.
LS3 Costs - Installation and Operation
The number one question from interested builders is “Why an automotive engine conversion?” Our answer is simple - more reliability, less cost to install, less cost to operate per hour, and less weight. The actual results will vary with different engines comparisons so let’s focus on the LS3. With the BW350 and an LS3 V8 replacing either a Lycoming 540 or a Continental 550 it works out like this. For reliability the TBO of an LS series of engines has been reported to easily reach 3000 hours with the same simple routine maintenance given to them when installed in a car. Based on inspections of the highest time BW350 and 200Z PSRU’s they should last at least that long following similar routine maintenance. This is at least 50% longer than either certified engine. The cost advantage is on both installation and operation. The initial cost of the installation for everything between the firewall and propeller is only 35% of the certified engines. With longer “TBO”, lower cost parts for maintenance with longer maintenance intervals, on an engine that burns 30% less fuel per hour results in the hourly operating costs of 70-75% less than the certified engines using Avgas, and 110-120% less if you use AutoGas. The Lycoming IO-540-K with exhaust, accessories, oil and engine mount comes in at 597 pounds for 300 hp. Compare that to an LS3 engine with accessories, oil, radiators filled with antifreeze, engine mount, and the BW350 with lubricant weighing in at 575 pounds for 367 hp. The LS3 installation is 22 to 24 pounds lighter (depending on installation details for different airframes) allowing builders to easily add a backup alternator, a backup battery, air conditioning, a prestart engine oiling system, dry sump oil systems, or a combination of those. At the propeller flange the LS3 and BW350 PSRU delivers over 20% more horsepower and torque than either certified engine for less weight and less cost. The more horsepower and torque allows for higher pitch angles on the propeller which equals better take-off, climb, and cruise performance.
Our question to builders is “Why use a certified engine in an experimental aircraft?” With the right PSRU and engine you can get more reliability and better performance at a fraction of the cost. Obviously this is a personal decision for each builder. But one universal goal of every pilot/builder is to find ways to reduce the cost of flying without sacrificing reliability. We think looking at the facts makes the decision a lot easier to make.
The following charts layout the details. They are based on Manufacturer Suggested Retail Prices. Anyone can shop around on the internet, flea markets, etc., and find lower costs. MSRP was used on everything to keep the comparisons as close to apples and apples as possible. Service hours are also based on the manufactures recommendations. A basic rule of thumb to convert miles to hours for auto conversions is to divide miles by 50 mph as an average speed.