Fuel Injection – Corvair flight engines reference page


Here is one spot where we have collected a number of different stories on Fuel injection for Corvair aircraft onto a single reference page. Like the other reference pages, it is a central starting point on the topic, and easy to keep updated or make additions to. If you are interested in learning more about this topic, read on, there is a significant amount of information here.

If I were to pick a single topic that new builders are interested in, but know little about the applications of, It would be Fuel Injection. This is a topic dominated by misconceptions and myths. Here is a quick check: Do you think that a port fuel injection engine or one with a carb on a long intake manifold makes more power? Would you be surprised to learn that the evaporative cooling effect of the carbs fuel delivery can give it a significant advantage? It does, and to learn this and many other points on reliability, read on. Unlike much of the info on the net from armchair experts, the information below is straight from experience and testing…in aviation settings, not in cars.




The information below is in the following order:


1) Links to stories I have written on FlyCorvair,net

2) A full print of my Group numbering system #3700 EFI notes.

3) A reality check story from 2008 on EFI failures

4) Notes on Internet ‘experts’ you should beware of

5) A 385 mph EFI plane and some final thoughts.


Above, a rear view of the Panther engine. Mounted on the intake is a Precision Mechanical fuel injection system. Initially, these was the planned fuel system for the Panther, but after careful evaluation, Dan Weseman opted to go with a very simple MA3-SPA carb. All of the aerobatic flights on video on the Panther site are done with a one barrel aircraft carb, not injection.




1) Links to stories I have written on FlyCorvair.net:


Click on the titles in color to read the full stories:


Mechanical Fuel Injection Testing

Compares Precision and Airflow performance instalations

Fuel Injected Corvairs

stories on 3 running EFI engines

Group Sources for the new numbering system.

Covers that EFI is Group  #3700 and Mechanical injection is Group #3800.

Panther Prototype Engine 3,000 cc/120 hp to OSH

Another look at the Precision system

Corvair Powered Davis DA-2, w/EFI

The only successful flying EFI Corvair powered plane. A hard won achievement.




2) A full print of my Group numbering system #3700 EFI notes:


3700- EFI (Electronic Fuel Injection)


Many people just arriving in aviation are interested in electronic fuel injection.  Some homebuilders are impressed with its performance in cars or have read about one of the handful of experimental aircraft flying with fuel injection. After listening closely to builders, I discerned their interest originated from five reasons: 1) They thought it would make the engine more powerful; 2) They thought it would reduce fuel consumption; 3) They felt that it would eliminate the possibility of carb ice and eliminate the need for carb heat; 4) They thought it would be more reliable than a carb, or; 5) They just wanted to try it. Experience has shown me that the first four are not true to any meaningful degree, and that #5 is the only reason that makes sense. If you are pursuing EFI for reasons #1-4, you are going to be disappointed, but if #5 is your motivation, then the project may be a success to you.

Let me first say that I am not against EFI, but I think that builders should know the facts before they pursue it. My background on EFI installations in planes is better than most. A guy who works on them all the time in cars, but doesn’t put them in planes, has a long way to go before he learns what he needs to know to be reliably and safely flying. I did a lot of work on Jim Rahm’s 427 cid V-8 Lancair IVP. It had the best EFI system in the air. We had the best people working on it, a nearly unlimited budget and experience that no homebuilder in his garage could match. It took a lot of very hard work to make it the reliable system. Just because Jim’s motor made 600 HP and you only want 120 HP doesn’t mean that solving the installation issues will only cost you 1/5 the time and money. And even if it did, we would still be speaking of time by the calendar years and money by the cubic foot. When I read discussions on the Net about EFI on experimental aircraft, I can quickly tell who has never assembled and flown a system.  95% of the advice on the Net is offered by people without flight experience. Out of the 30,000 experimental aircraft in the U.S., I am fairly sure that less than 300 of them have EFI. I cannot think of a single significant aviation record below 500 HP that is held by an EFI engine. There have been many clever people who put a lot of effort into EFI on planes, with little result. No matter what caliber of auto mechanic you are, experience says that you will find exceeding the performance of carbs or mechanical injectors very difficult, and EFI may never have the reliability record of the simple 1 barrel carb.

Out of the roughly 300 experimentals flying with EFI, the vast majority of them are using 1990s auto engines with EFI from the factory. In this case, the factory engineers did most of the work. If you think about it, there are very few motors like O-200s, VWs and Corvairs flying on EFI. And the ones flying can’t boast the flight record of carbureted engines. I have seen a number of these planes flying with 35psi fuel pumps inside the cockpit with barbed hose connections and hose clamps. No one should dream of flying things like this. Let’s examine the points one by one objectively to learn about the issues and make an informed decision.

1) I have seen claims that EFI makes the same engine 30% more powerful. Nothing of the sort is true.  Engines make power because they burn a mass of air mixed with the right amount of fuel. There is no way that an engine is going to inhale significantly more air because it doesn’t have a venturi carb. This advantage is slight, and would be well below 5% on an engine like a Corvair. To see any more difference than this, the cylinder heads and intake tract would need to be designed for it right from the start, by very smart people with a lot of sophisticated equipment (of the caliber found in Detroit factories). Slapping an EFI system on the Corvair will not have the same effect. Fuel injected motors are said to make slightly more power because the fuel is better atomized. But carbs, even simple ones, are surprisingly good at this. The amount of records still held in racing by carbs should tell anyone that the EFI power advantage is minimal. Carbs have a very serious advantage of vaporizing the fuel well upstream, and having the air/fuel mixture cooled and its density increased. In almost every case, this offsets any gain in power from atomized fuel. When running at power, Corvair intake manifolds are cold to the touch from vaporizing fuel. EFI does not have this effect.

2) EFI will not significantly reduce fuel burn in a Corvair engine. For best economy, engines need to run a lean mixture. EFI has the theoretical ability to atomize fuel slightly better allowing it to run slightly leaner mixtures than a carb could without detonating. In actual use, it is foolish to run an engine this close to detonation. Modern auto engines can do this because they have computer-controlled ignition tied to a knock sensor and the fuel injection. Without these devices, any significant fuel burn advantage is lost. Many of the well known auto power proponents, even those who work with computer controlled EFI engines, clearly state that EFI doesn’t significantly reduce fuel burn for a given HP in aircraft engines. The efficiency advantage in cars is gained by running in “closed loop” with air/fuel ratios near 14:1. Under this operation, the injectors are fine tuned by reading the O2 sensors many times a second. The reality that few new builders understand is that any engine running at 75% or more power has to be running an air fuel ratio of 12:1. At this setting, O2 sensors don’t reliably work, and the system will operate in open loop, forfeiting any efficiency gains while retaining all the complexity and vulnerability. I have never seen any EFI flight engine that will fly at cruise power in closed loop mode. They are all just operating off a set of pre-programmed values based on RPM and MAP. These can be very crude, as some aftermarket EFI systems have RPM increments as rough as 250 RPM. In cars this would be masked by the O2 sensor moderating the injectors, but it can’t when it is in open loop. It is technical reasons like this that allow carbs to often demonstrate smoother operation than EFI in experimental aircraft.

3) EFI is less prone to carb ice, but is not immune to this trouble. There are still conditions that can cause this trouble. Almost all injected engines have an alternate air source. Homebuilt aircraft in Canada are required to have heated alternate air no matter what the fuel system is, and there is good logic to this. For a more complete discussion of this, see the article on carb ice at the end of the Manual.

4) Many people feel that EFI will free them from things like carb ice, reducing their level of risk in flight. While the risk of carb ice would be reduced for a pilot too careless to use carb heat, many new risks are introduced. EFI requires high pressure pumps, regulators and lines; it can be stopped by a piece of trash in the fuel that a carb would easily pass; its numerous electrical connections are prone to failure by corrosion or poor crimping; and the whole thing is so electrically dependant that most people fly with two batteries. Contrast this with a gravity feed fuel system in a plane with distributor ignition which will run for hours on a small battery with no input from an alternator. You cannot focus on the one possible advantage of a system without considering all the downsides that come with it. Automotive EFI installations are reliable today because auto makers spent literally billions to make them so. Brilliant people in Detroit who are specialists in dozens of details of the installations and privy to incredibly accurate statistical data on failures allow them a great corporate body of experience to tap into with every installation. It is my feeling that anyone looking into EFI who states that it is more reliable is making an argument for the car, not what an individual homebuilder can do in a plane, where a single detail of installation may compromise the system.

My observations on reliability are simple: Any system that uses lower pressure fuel is less likely to leak. Gravity is better than 5 PSI, and 5 PSI is better than 40 ; any system that uses no electricity is better than one that uses  a little, and one that uses a little is better than one that uses a  lot, especially if the one that uses a lot needs it to be a  certain voltage; any system that has less parts and connections is less likely to  fail,; digital electronic connections, working a low voltages, are very sensitive  to corrosion, temperature, and vibration, things planes produce more than newer  cars.

5) Being an experimenter at heart and wanting to address the challenges of an EFI installation is a valid reason for trying it. You know a good, reliable and airworthy system is quite a challenge because you don’t see them often. Anyone who achieved this could be justifiably proud of his creation and would learn a lot along the way. A person who is motivated by this will be satisfied when it works, whereas people motivated by #1 – #4 are bound to be disappointed when EFI cannot live up to the overblown claims many armchair/Internet experts make for it. The only good reason to work on an EFI Corvair is because you want a challenge, and this is more important than finishing your plane soon, or operating at a lower risk level. This is a valid position, and I support anyone who knowingly makes it.




3) A reality check story from 2008 on EFI failures:


” A Christmas story”

 At 8 a.m. on December 24th 2008, I was driving my 175,000 mile EFI S-10 up I-95 at 75mph. I had promised my parents that I would make it to their house for Christmas Eve dinner. I had never had a bit of trouble with this EFI engine. Near Richmond, Va., it quickly died out, and I was only able to coax it into a truck stop at 10% power. A morning of diagnosis showed that the pressure regulator had died. It was not in an easy place to get to, no one had a replacement and the truck was worth maybe $500 before it was broken. I gave the truck to a 20-year-old tow truck driver wearing a Chevy hat and a Jack Daniels sweatshirt, as a trade for a ride to a car rental place. We got there 10 minutes before they closed. The driver asked me several times if I was really giving him the truck and if I really was from New Jersey. The experience was counter to many things he had been told about people from N.J.  After some reservation, he took the gift of a truck from a Yankee on the eve of the birth of Jesus to have special significance.

 Such a warning less failure in a plane might prove to be lethal. Note that aircraft carbs almost always run even when they are having an issue.  A good look inside Pat Panzera’s Contact! magazine issue #96 shows a destroyed homebuilt aircraft, product of a sudden EFI failure. Here is a story of a guy who may have felt that carbs and engines without O2 sensors were stone age. Maybe, but stone age tools are noted for reliability. I am glad the builder was not more seriously hurt. Over the years, a number of people have written to explain that they are going to engineer their own EFI systems, or use something called “shareware” to program one (the blind leading the blind on the Net). Out of perhaps 50 people who have written this, not a single one of them went on to produce a running EFI engine. Experience tells me that people who arrive with a big flourish and little consideration for what has been accomplished have a very low chance of flying anything.




4) Notes on Internet ‘experts’ you should beware of:


A modest search on the internet will reveal many people speaking about EFI for Corvair powered planes. Armed with the information I have printed above, you can debunk most of the claims people make. Still, there are people who present a case to new builders as if they are some type of experienced expert to be followed.

The internet is an odd storage device. I holds more old trash better than any landfill on earth, and it keeps it fresh, even long after the project was abandoned. Let me share by example: Don’t waste the time to look it up, but there is a long detailed website run by “Haynes Engineering.” Sounds official, but it was just one guy in a barn who had never built a flying plane before, offering a long how to session on putting EFI on a Corvair in a Zenith 601. I never met the guy, but I did email him several times, and he spent a long time on Mark Langford’s discussion list, where he had many fans who eagerly awaited Mr Haynes demonstrating all the things he promised from is Harley Davidson salvaged system. Although I offered to publicly test run his engine at a college, Mr. Haynes soon despised me, probably for not recognizing his brilliance. His website is all about putting a Corvair on a 601, but makes no mention of Our success with doing this, or my work at all.

If you have built planes, it was easy to see that Haynes didn’t know much about planes, but had the kind of ego that didn’t like admitting that. He was a foolish cheap skate, ‘rebuilding’ his engine with a used cam and worn gear, and using angle iron to build a motor mount. His EFI system had hard aluminum lines where it needed flex ones, and he spent a lot of time trying to use a little outboard starter. In the end, after getting many green guys excited, he couldn’t make the engine run, and instead started it for 5 seconds on starter fluid, and then wrote a post to the internet silmaltainiously declaring victory and quitting airplane building altogether. Does this sound like a stable person who you can learn from? Is it the kind of information that you want to bet your life on? This was years ago, yet I saw the website just last week, with no mention of the system never working or the whole aircraft project being abandoned.

If you are new to home building, the quicker you learn never to be distracted for real progress by day dreamers and fools without experience, is the quicker that you will learn what really works, and how to incorporate these skills into your own experience and your own plane. The internet will provide an endless stream of people like that. 80% of the people who start a homebuilt do not finish. Be determined to be in the 20%. One of the things that the 20%ers all have in common is not getting sidetracked by fools.




5) A 385 mph EFI plane and some final thoughts:


I’m known for advocating simplicity in aircraft engines. This recommendation comes  from my experience on the opposite end of aircraft powerplants. Above,  Arnold Holmes (host of CC#17,#25, #29) and I stand behind the engine installation on a V-8 powered Lancair IV-P.  This is an EngineAir package that I helped develop from 1993 to ’98. It’s 450hp, geared,  injected, intercooled and turboed, and features air conditioning. Get a good look at the size of the 5-blade MT propeller.

  Eventually, about a dozen of these took to the air. They were stunning performers. I flew  from Oshkosh to Daytona Beach in three hours and five minutes in our first airplane, N420HP. This aircraft is on the cover of Sport Aviation in July ’97. If someone suggests I don’t understand EFI, ask them if they have flown in a 385 mph EFI plane they helped develop and build.

 The development of this engine took the work of many clever, dedicated people, and one  guy with cubic yards of money, Jim Rahm. It worked, but taught me that homebuilders at all levels  tremendously underestimate the effects of complication, primarily its delays and expenses.  Whenever I read discussions about electronic injection or computer controlled engines, I  can tell in an instant who has no practical experience with attempting to prepare these  systems for flight.

Evaluate your interest in fuel injection carefully. for most builders, it is a distraction, for some it will become a stumbling block, for a tiny number of people it may become a dangerously complex part of their plane, a part they thought would be the most reliable, but turned out to be the part they trust the least. This is pretty far from the goals that most people have when the first think about putting EFI in their plane.-ww

One Reply to “Fuel Injection – Corvair flight engines reference page”

  1. Thank you for putting my feet back on the ground about EFI. I forgot that in flight you can’t pull over and pop the hood when an electrical gremlin bites your fuel system. I especially appreciated your comment about the internet:

    “The internet is an odd storage device. I holds more old trash better than any landfill on earth, and it keeps it fresh, even long after the project was abandoned.”

    This sounds much like Haynes Engineering which you referred to regarding his EFI expertise. As an engineer keeping simple yet functional makes a great deal of sense. The Lord has blessed you with an abundance of sense (I almost referred to as common which it no longer is) and a quick whit.

    God Bless,

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