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Frequently asked

questions about

Superior's XP-Engines


XP-Engines versus certified engines

Q: Are Experimental, XP-Engines, new, zero-time engines?
A: Yes they are. All XP-Engines are brand new, zero time engines designed to meet the increasing demands of the Sport Aviation market. Each XP-Engine comes with an Operator’s Manual, new logbook and an XP-Engine Data Plate.

Q: Are XP-Engines FAA-certified?
A: No. Although the majority of components are FAA-PMA approved, XP-Engines have not been type certified as a complete engine. Therefore, once assembled, the engine falls in the experimental category.

Q: What do you mean by the majority of parts are certified?
A: Superior holds FAA Parts Manufacturer Approval (PMA) approval on all major components and the piece parts with the exception of some standard hardware, some new-generation accessories including our state-of-the-art cold air induction sump and roller lifters.

Q: What is a XP-360 PLUS Engine?
A: The XP-360 PLUS incorporates a revolutionary new camshaft and roller lifter design, which is based on proven automotive racing engine technology. The new camshaft features a more efficient lobe profile along with roller lifters to provide many performance advantages over the standard flat tappet camshaft design.

Q: Who builds my XP-Engine?

A: You have four options:

#1: You can have your XP-Engine assembled by our engine builders here in our engine build shop.
#2: You to come to our facility and attend our XP-Engine Build School and watch as one of our trained staff assembles your engine.
#3: You to come to our facility and attend our XP-Engine Build School to assemble your own engine under the supervision of our trained staff.
#4: You can have one of our authorized engine builders assemble and test your XP-Engine for you.


XP-Engine Performance

Q: What is the maximum continuous horsepower rating of this engine?
A: Max continuous horsepower depends on engine model and configuration. Please see XP-Engine Specifications page for specific information.

Q: What effect does altitude have on this rating?
A: None. All aircraft engines are rated by the amount of horsepower they produce at sea level at standard ISA conditions. As with any naturally aspirated engine, as pressure altitude increases, available horsepower decreases, however, this effect does not change the rated horsepower of an engine.

Q: Are there performance curves available for the engine and how do I get them?
A: Yes. Superior has an XP-Engine specifications sheet that provide dimensional data as well as power curves. They are available on our web site at XP-Engine Specifications.

XP-Engine Characterestics

Q: What is the difference between Superior XP-Engine and a typical Lycoming engine?

A: Quite a bit. The XP-Engine includes the latest improvements in technology and many other custom enhancements, yet unavailable on standard Lycoming factory engines. A detailed list can be found at XP-Engine Specifications.

Q: What is the type and minimum grade of fuel?
A: XP-Engines are approved for 91 octane unleaded auto fuel* and a minimum of 100LL aviation fuel. Superior recommends 100LL, although this is not a requirement.

Q: Does this mean I can use auto gas?
A: The XP-320 and XP-360 can operate and perform at rated power using unleaded automotive fuel*. When operating on unleaded fuel, Superior recommends using fresh, premium auto fuel available at a major brand, reputable gas station. Acceptable fuels are specified per ASTM D-4814 (European EN228). 

* NOTE: Use of auto fuel blended with ethanol or gasohol is forbidden with XP-400 Engines equipped with cylinders with compression ratios greater than 8.5:1.

Q: Is there special or specific oil approved for the engine?
A: The recommended oil must meet MIL-L-22851, ash less dispersant grades. Multi-weights (15W50 or 20W50) are recommended for all temperatures and straight weight oils are recommended for various average ambient air temperatures.

Q: Are XP-Engines available in 12-volt and 24-volt configurations?
A: Yes, both configurations are available.

Q: Can I use my existing engine mount?
A: The engine mounts for the XP-Engine series were designed as a direct “drop-in” replacement for a Lycoming engine.

NOTE: It is imperative to determine whether your existing engine mount is designed for #1 or #2 dyna-focal mount or a conical mount style engine. The various mount types are part of the engine crankcase and cannot be modified once the engine is assembled.

Q: What is the dry weight of the engine?
A: That depends on the particular engine and its accessories. Please see the XP-Engine Specifications page. 

Q: My aircraft requires a forward mount induction system. Will the XP-Engine fit?
A: Superior has developed a new state-of-the-art horizontal forward-facing cold air induction system that is designed for fuel injection applications. The Cold Air Induction System is now available only from Superior as an option and will work with forward induction cowls on most aircraft. Contact: sales& for details. 

Q: Does the engine come with an oil filter and an oil screen?
A: Yes, XP-Engines are supplied with a full flow oil filter and an oil suction (finger) screen.

Q: What is the XP-Engine’s RPM range?
A: Redline RPM is 2,700 RPM. Normal cruise RPM is 2,300 – 2,500 RPM.

Q: Can either a fixed-pitch and constant speed propeller be used?
A: Yes, Superior offers models of the XP-Engine configured for a fixed-pitch propeller and models configured for a constant speed propeller.

NOTE: Installing a constant speed propeller on engines configured for fixed pitch propeller requires modifications to the engine. Installing a fixed pitch propeller on an engine configured for a constant speed propeller requires engine modifications as well.

Q: Which propellers are approved for the engine?
A: There is no approval process for propellers on the experimental engines.  However, Superior engines are made up almost exclusively of PMA parts.

Q: Are there any propeller restrictions with the XP-Engines?
A: That depends. Some of the propellers that are approved for the XP-Engine series do not have any operating restrictions. There are however some propellers that do have operating restrictions. These restrictions can be obtained by contacting:

Q: Are XP-Engines fuel injected or carbureted?
A: There are XP-Engines models available with an experimental RSA-5A fuel injector option or an MA-4-5 carburetor option. Various other aftermarket fuel system options are also available.

Q: What lifters are used in the XP-Engines?

A: XP-Engines can be built with the traditional flat tappet lifters or with Superior’s advanced roller lifter technology. Our roller lifter-equipped engines incorporate a revolutionary new camshaft and roller lifter design, which is based on proven automotive racing engine technology.

One unique feature of the Superior roller lifter system is the ability to remove the lifters without having to split the crankcase.

Q: Is Superior’s roller lifter technology more durable than standard flat tappet design?
A: Typically, yes. Roller lifter technology is more durable than standard flat tappet designs. There are two reasons for this. First the profile of the camshaft is very gentle and allows for smoother operation. Second, the roller lifter rolls over the camshaft lobes instead of sliding across them.

Q: What types of Accessories come standard with the engine?
A: The standard XP-Engine includes the following new accessories:
• Slick magnetos and ignition harness
• Champion spark plugs
• Sky-Tec starter
• Precision Fuel System (carburetor\Fuel Injection)
• and an Aero Accessories fuel pump.

Q: Can I request optional accessories for the standard XP-Engine package?
A: Yes. Superior has several optional accessories available and will continue to add to the options as they become available to the market. Currently we offer packages for:
• Light Speed Ignition Systems
• PMag Ignition Systems
• Airflow Performance Fuel Injection Systems

Q: Does a vacuum pump come with the engine?
A: No. Superior does not include a vacuum pump with the XP-Engine. Because of the various applications the engine may fit in the kit plane market, some customers may not require a vacuum pump. Since vacuum pumps are readily available in the marketplace and to keep the cost down, we allow the customer to make the decision as to whether he needs a vacuum pump.

Q: Where does the alternator mount?
A: Although the XP-Engine is not supplied with an alternator, a provision has been provided to mount a bracket to the lower right front portion of the engine. Because of the various applications the engine may fit and the different requirements for electrical systems and to keep the costs down, Superior does not supply an alternator with the XP-Engine.

Q: Is there a provision on the XP-360 Engine for bayonet style cylinder head temperature probes?
A: Yes. The Superior Millennium Cylinders installed on XP-Engines have provisions for bayonet style cylinder head temperature probes.

Q: Can I buy replacement accessories from Superior?
A: Not directly. Aftermarket replacement accessories and spare parts are available from Superior’s worldwide distribution network. For Distributor’s and their locations see our Distributors.


XP-Engine TBO

Q: What is the TBO of the XP-Engine?
A: Superior has established a recommended 2000-hour TBO for the XP-Engine series.

XP-Engine Service and Maintenance

Q: What are the scheduled maintenance requirements for this engine?
A: The individual Engine Operators Manual outlines the required maintenance inspections including pre-flight inspections, the initial 25-hour inspection, and routine re-occurring 50, 100 and 500 hour inspections.

Q: Who is authorized to perform maintenance on the engine?
A: Because the XP-Engines are experimental, no specific FAA license is required to do maintenance or inspections. However, for the owner’s safety and peace of mind, Superior strongly encourages owners to have a licensed mechanic work with an owner for the first inspections for the purpose of training and to insure the engine is thoroughly inspected.

Q: Are replacement parts readily available for the engine?
A: Yes. Superior has a network of Authorized Superior Distributors Worldwide that carries a large assortment of inventory. For a list of our Distributors, please visit here

Q: Are there specific break-in procedures for the engine?
A: Yes. Superior has a published Service Letter 96-08D that applies to our XP-320, XP-360 and XP-400 Engine. Procedures are also included in our Operator’s Manual and can be found on our web site at

Q: What oil change frequency does Superior recommend for XP-Engines?
A: We recommend you change your oil and filter every 50 hours or 6 months whichever occurs first.


XP-Engine Cost and Availability

Q: What is the cost of the engine and what is included in the cost?
A: Due to the various options available on the XP-Engines, Superior recommends calling our toll free number (800-277-5168) or 972-829-4600 and ask a sales representative for a quote.

Q: What is the cost of various options for the engine?
A: Due to the various options available on the XP-Engines, Superior recommends calling our toll free number (800-277-5168) or 972-829-4600 and ask a sales representative for a quote.

Q: Can I order an engine today and whom do I order it from?
A: Yes! Call Superior at 800-277-5168 or 972-829-4600 and ask for an engine sales representative. Our sales representatives can assist you in determining the exact engine you want and answer any questions you may have. We have many options available to you, including being present at the factory and viewing the assembly and testing of your engine.

Q: If I ordered an engine today, when can I expect delivery?
A: The only way to determine delivery dates is at the time of order. Once the engine is ordered, depending on the backlog of owners ahead of you, we can give you a firm date for delivery.

Q: Is a deposit required and is it fully refundable?
A: Yes, a $5,000.00 deposit is required to place your order into our production plan. Superior will contact you as your engine nears completion for final payment. Deposits are refundable prior to starting the engine build process. Once the build begins, the deposit is no longer refundable.

XP-Engine Miscellaneous Subjects

Q: I have read about an SV- and the XP-, what is the difference between the two engines?
A: The SV-360 is the designator for the FAA Certified 180-horsepower Vantage Engine. This certified engine is built and tested by Superior under a FAA Type Certificate and Production Certificate. The XP-Engine is the designator for the experimental engine. This experimental engine is built and tested by Superior and is supplied with an XP-Engine data plate, a Superior logbook and Operator’s Manual and is primarily for use in an experimental airplane.


XP-Engine Q&A’s from our customers

Q: Please can you give me the dimensions of the XP-320 conical mounts - Distance between the centers. I want to confirm that it will fit on my engine mount - The aircraft is a UK homebuilt.
A: The conical mount is 9.560 vertical center distance, 11.5 horizontal center distance, and it is 4.56 from the bottom mount centers to the crankshaft centerline

Q: After break-in can I use a synthetic or semi-synthetic blend oil? What are your recommendations?
A: We approve the use of any FAA approved aircraft engine oil.

Q: Does the injected engine require a fuel return line?
A: The standard XP-Engine fuel injection system is the Precision Silver Hawk system. This system does not require a return line. If you purchase an XP with the optional Airflow Performance system, this system does require a return line.

Q: I am building a RV-7A. Is the Sensenich O-360, 2 1/4" spacer, 1/2" bolt, 85" pitch suitable for this use?
A: RV kits shipped since late 1993 require a 2 1/4" extension. The bolt size for the O-360 is 1/2".

Q: What is the bolt size used to fix the propeller on an XP-360?
A: The bolt size is 1/2"

Q: I am buying an RV-7A kit and intend to use a XP-360 Engine. I´m going to use a fixed pitch propeller but would like to have the option to change for a constant speed prop in the future. What is the best engine version to buy?
A: The best and most economical way is to purchase a constant speed XP and have us build it in a fixed pitch configuration. This will save you a lot of money in the long run and bring more value to your aircraft when you sell it.

Q: Do you have any type of program where you might take a low time engine in on trade-in?
A: We only sell our engines outright. This gives you the opportunity to sell your core engine for best value.

Q: Does an XP-360 with fuel injection need to be primed for starting?
A: No. In a fuel-injected model you use the electric boost pump to get fuel to the flow divider and cylinders before start up. No primer lines or system is required.  


*NOTE: Superior XP-Engines are approved for 100LL Avgas per ASTM D910, 91/98 (lead optional) and motor gasoline with a minimum antiknock index (R=M/2 method of 91 per ASTM D4814 (European EN228). Use of auto fuel blended with alcohol (ethanol) is forbidden.

  • The XP-360 Engine® series, when operated with pistons of 8.5:1 or lower compression ratio, can operate and perform at rated power using unleaded auto fuel. Engines with a compression ratio of 8.5:1 must be operated on a minimum of 91 Octane auto fuel. Engines with compression ratios of 7.2:1 or lower can operate on a minimum of 87 Octane auto fuel.

  • The higher the octane used in the XP-360 Engine®, the greater the detonation margin during high power and/or hot operation. When operating on unleaded fuel, Superior recommends using fresh, premium, auto fuel available at a major brand, reputable gas station.

® XP-Engine, XP-320 and XP-360 are Registered Trademarks of Superior Air Parts, Inc.
® Millennium Cylinder is a Registered Trademark of Superior Air Parts, Inc.
® Vantage Engine is a Registered Trademark of Superior Air Parts, Inc.

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