William Wynne

"The Corvair Authority"
5000-18 HWY 17 #247
Orange Park, FL 32003


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January 5, 2005

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Subj: Your Corvair/KR Cowling
Date: 1/4/05

Rumor has it that you may be going to offer a cowling for the KR to use with the front starter??

Eric Pitts, Terre Haute, Indiana

Reply from WW:

Our latest issue of The Corvair Flyer newsletter has photos and a story on our Corvair powered KR project. Did you get your copy yet?
Subj: Fuel System
Date: 1/3/05

I'm plumbing my fuel system on a Dragonfly firewall, which as you know is tiny. I've changed my mind several times and ended up with the KISS principal, using a gravity feed from a header tank and a backup Facet pump in case gravity ain't enough.

Reading Tony Bingelis' Firewall Forward, he stresses that there should be no reversals in the fuel flow between the gascolator and the carburetor. I notice in your 601 fuel system, you've got the fuel flowing up from the gascolator through two Facet pumps then back down to the carb. That sort of configuration may be one of the few that would fit in my airplane, but I wonder if the reversal will make the system vulnerable to vapor accumulation or other problems associated with the high spot.

You've got a lot of flying time on different fuel systems, so what is your experience with that configuration? Are you able to do the reversal because your system isn't gravity-fed?

Thanks!, Dave Morris, Dragonfly, Texas
Reply from WW:
Tony Bingelis stands out as the individual who did more to improve the quality of your plans built homebuilts than any other person in the first 50 years of homebuilding. His magazine articles and four books are the standard for detail design information on homebuilts. Tony passed away several years ago, but most of his information is timeless. After 15 years of homebuilding, I could point to a few small items in his books that I'd disagree with in some circumstances. This doesn't mean Tony was wrong, it means that he was writing for all homebuilders, and seeking to define systems which would work in all homebuilts.

In some instances, the reversal of the fuel line is not an issue. Here's why: Think of the gascolator as a sink trap. If it's anywhere in the system, it will trap any water passing through that point until it is full of water. If I got more than a few CCs of water out of the gascolator, I'm going to drain a lot of fuel out of it and run the engine extensively to ensure the system is clear. If there were water in the reversal, you'd find it. One or two ounces of water going through a system will be strained out by a quality gascolator. If you have this much water in your gascolator, you need to stop and investigate before you go flying. My personal preference in fuel systems is no fuel lines in the cockpit under pressure, gascolator ahead of the firewall but above the bottom edge of it (this is especially important on an aircraft like a Dragonfly, which could break the canard in a hard landing and lay on its belly). Use a quality gascolator like the Andair. If you're going to use a fuel pump, it should come after the gascolator so the gascolator is not subject to pressure.

The main issue with the line between the pump and the carburetor is that it be a quality AN-style line, and have enough slack to allow for the movement of the engine. Preferably, you would firesleeve this line. This will give it additional resistance to heating the fuel with engine compartment air. Keep in mind that fuel has a boiling point around 170F under standard temperature and pressure. But it is significantly higher than this if it's subjected to only a few psi. If you're using a float type carb, the only real good candidate for a pressure system is an MA3-SPA. Keep in mind that once the fuel gets to the float chamber, it is no longer subjected to pressure, and its boiling point would return to 170F. In our airplane, the engine compartment air runs about 100F hotter than ambient. However, the MA3-SPA runs significantly cooler because the air flowing through it is outside ram air, and it has fuel vaporizing in it continuously while it's running. Write us back and let us know what type of carburetor you're thinking of using so we can discuss a few more details.

Subj: Turbocharging
Date: 1/3/05

Hi Mr. Wynne. I just ordered a Kitfox Series 7 and want to put a 164 cid Corvair in it with aftermarket turbocharging. I have your Manual and the Chassis manual. Can you advise/direct me to the info I need to build one. Obviously I need names of parts, specific engine modifications outside the ordinary for the non-turboed 164. I finally found an engine here in Montana. Boy it wasn't easy out here! Thank you very much.

Terry Calderwood, Kitfox 7, Missoula, MT
Reply from WW:
Not a lot of Corvairs found their way to Montana. I suspect it's easier to find 1960s pickup trucks in your state than 1960s cars. Glad you were able to track one down.

Kitfox Series 7 has a reputation as a well developed aircraft. A turbo 164 would likely provide outstanding performance while remaining within the weight restrictions for the aircraft. Our turbo testing is still undergoing detail work. But here is what we've established: Most important, the engine is clearly strong enough to take it. Second, it has enough cooling capacity so that cooling's not an issue. These are important points that stop other engines from effective turbocharging. The Corvair is the only production engine I can think of that was built to be turbocharged without the use of electronic controls on the ignition or fuel system, or a wastegate. These systems can be used to protect an average engine from hurting itself when turbocharged. Typically, however, homebuilt aircraft do not utilize these systems and it's better to have an engine of robust construction and plentiful cooling like the Corvair.

It should go without saying that a turbo engine needs to be a first class rebuild. It should have connecting rods with ARP bolts from Clark's or SC Performance. The cylinders should either be Clark's, or preferably, bored by Ray Sedman at American Pi. The rings have to be chrome. The exhaust valves should be stainless steel and have bronze guides. I'd be very tempted to have the seats and guides done by Wheelerizing in Brea, California. The only significant internal difference is the use of a TB-10 cam from Clark's in place of the OT-10 cam. This cam is a version of the OT-10 specifically for turbocharged engines. We have dyno tested this camshaft in two different naturally aspirated Corvairs to verify that it does not significantly reduce the engine's output when it is not turbocharged.

We still have to develop and fly several external systems to come up with a combination that is easy to operate, affordable and reliable. We'll be doing these tests in the coming months. The above recommendations are enough to go on to build your engine for now, and we'll supply the systems information as we further develop it.

Subj: 601 Cowling
Date: 1/3/05

Are you planning on putting out prints for cowlings to match the Corvair engine installation? I need to know how much overhang on the side skins do I need to leave?

Roger Parnow, 601XL Taildragger, Crestline, OH
Reply from WW:
We're currently working on prints for the sheet metal parts of the 601 cowling. These sheet metal parts go between the 601 fuselage and our Nosebowl. We made two prototype sets, and studied them for ways to make them simpler, lighter and easier to fabricate. The drawings will reflect these improvements rather than be simple copies of the prototype cowl on our plane. We're also going to offer cowling kits with all of the bending work prefabricated. We have an extremely nice Whitney industrial finger break in house, and will be able to offer these at an attractive price. The plans will be available free to anyone who's purchased a Nosebowl from us. We'll have pictures of the cowling kits on the Web site in a few weeks. Our own 601 has 2" on the sides ahead of the firewall. I've seen several builders' planes that are closer to 4" and would need to be trimmed later. Our intention is to leave the cowling long on the aft side to allow for builder variation. It's a very simple matter to trim it.

Subj: Oil Pan, Auto Gas
Date: 1/3/05

I have read your Manual for hours and am surprised how comfortable I am getting regarding building my engine. I have a core and have taken it apart. After reading about the mods you provide, I plan to use your system for the 601XL. I have completed my rudder and was pleased with the results.

My question is regarding the oil pan. I have what appears to be a good steel pan, and have a question regarding your pan. What are the advantages of having additional oil if cooling is not a problem? It seems that using the stock pan, and changing the oil more often would be an advantage for using the stock pan. Am I missing something?

For the future, I plan to use LL100, but if none is availabe, does it hurt the engine to mix auto gas with LL100, until you can get to a location where the avgas is available?

Thanks in advance, and am looking forward to begin ordering parts to complete my conversion. I still need to build the airplane, but am hoping to finish by July of this year.

Regards, John Butterfield, Zenair 601XL, California
Reply from WW:
Traditionally, Corvair engines used a modified stock oil pan for Pietenpol flight conversions. This worked and logged a lot of hours in Pietenpols. Many Corvair cores have damaged pans because it occasionally functioned as the skid plate on the car, and careless mechanics used it as a jack point. Because of this, few stock pans are good candidates for the traditional welded modification. (This mod is available in plans form from the Pietenpol family.) Today, the Corvair engines we build produce more power, and we expect them to last longer. Our oil system modifications are based on these points. Our Deep Sump Aluminum Oil Pans bolts right on and works with aircraft motor mounts. The additional oil capacity has the effect of making the engine run cooler, and extending the intervals between oil changes. The oil carried lower in the pan's sump allows the oil pickup to remain submerged in uncoordinated flight. For these reasons we install our Pan on every engine we build.

You can mix 100ll and 93 octane auto fuel. The engine can be tuned to run on 93 continuously. I have more than 100,000 miles of driving Corvair engines on the road, and this was all done on unleaded auto fuel. I prefer avgas in flight applications for a number of technical reasons outlined in great depth in the Conversion Manual, but people who have better access to 93 octane fuel can utilize it with minor tuning changes to the engine.

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