Turbo Corvair Conversion ..........Hypothetical

Discussion in 'Corvair' started by ekimneirbo, Jun 17, 2015.

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  1. Sep 16, 2015 #21

    Bill Clapp

    Bill Clapp

    Bill Clapp

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    Yes it has been done. It hs also been done for cars as well. However for that plane you have to look for reliability and simplicity. I would use a bendix mechanical system if I had to. However, consider the added cost and complexity. (fuel pumps, lines, injectors, spider, regulator, throttle and valve assembly) It surely can be done and I plan to make a system that would be as simple as possible. However for the turbo we plan a simple draw thru system that uses a slide carb. This atomizes the fuel air mixture very well. Our goal is turbo normalizing with a slight amount of boost available for low altitude take-offs (fixed pitch prop initially).
     
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  2. Sep 16, 2015 #22

    slevair

    slevair

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    Yes these were maximum effort engines, but the heat soaking issue can come from power, load, or duty cycle. Even high output race engine see higher vacuum at some point on the track to cool for a second, this rarely happens in a plane. No braking or shifting to get a rest. You would need a time to climb limit for maximum power usage.
    Yes there have been F.I. set ups made for Corvairs. Mostly one offs or custom adaptations. Several have used Holley Pro-jection. We have had a few through our shop. But, we don't build plane engines. There are others already doing a good job, why divide the pie into smaller pieces?
     
  3. Sep 16, 2015 #23

    slevair

    slevair

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    High load at low RPM has it's own set of problems. Combustion and exhaust temperatures are elevated in the chamber for a longer period. This is part of what leads to the heat soak and valve seat problems. And, on ground pounders, the fan is running slower. A small but useful amount of cooling comes from cycling intake air through the cylinder at a higher rate.
     
  4. Oct 26, 2016 #24

    DaveP

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    The Saberwing is now flying with a turbo-normalized package. The prop has been upped by four inches of pitch. There are videos on Azalea Aviation's facebook page. I'm sure that Bill will post more data as it becomes available.

    I read here that someone commented on cooling at 180Hp would be "marginal". It is my understanding that the Corvair won't cool more than 127Hp at continuous power. This was described as a limit imposed by the surface area available for cooling. Remember that an auto only uses the full power briefly in road driving.
     
    Last edited: Oct 26, 2016
  5. Oct 26, 2016 #25

    Bill Clapp

    Bill Clapp

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    I am glad Dave showed me this other link....I had forgotten about it. Here are some of the specs we have.
    Corvair 3.0 L - (1/4" stroked with .060 full fin cylinders)
    New JEI pistons - forged
    Compression ratio 8.5:1
    Timing 25' Max
    Turbo - Rajay 301 series - no wastegate - carbon seals
    Exhaust 302 stainless
    Carburetor - Aerocarb 35 mm
    No intercooler
    Larger oil cooler

    Performance: Before adding the turbo I flew the Saberwing to Oshkosh normally aspirated. With the lower CR you could tell the lower performance. After the engine had 15 hours on it I added the turbo package on the engine. Engine ran very smooth with very little carb adjustment from previous setup. The turbo comes on line at about 2200 rpm or so is when you can really see it make a difference. Because there is no wastegate you do have to carefully monitor the manifold pressure. I have a Vernier throttle just for that reason. During the first flights I limited the MAP to 30" on takeoff to monitor temperature and any spiking. First flights were kept to about 30 minutes. Post flight inspections were clean and non events. Climbout was not real impressive at the 30" MAP and takeoff roll seemed a bit longer than I liked. I am sure that at 30" on the Lower compression engine I am only getting about 100 HP at that setting. After 5 hour of testing I started testing higher boosted pressures and that is where I really saw a performance increase. If I am light (myself and 25 gallons fuel) I can take off at 35" - and rotate into a 1500'/min climb rate at 100mph. Really cool. I could take off and be close to pattern altitude by the end of our 5500 foot runway. Now that is pushing it and not recommended but good for testing. Higher angle of attack causes higher CHTs - but they still stayed below 400. If I didn't drop the nose to 120 mph or better I am sure the CHTs would climb more. At 120 MPH they stabilize well at about 350 degrees. At 7500 feet , 25" MAP the airplane cruises at 155 indicated burning 5.5 gal/hr and 3300 rpm. At 30" it was cruising 167 indicated at 6.2 gal/hr and 3450 rpm. At 35" (testing) it indicated 180 at 7.5 gal/hr and 3600 rpm. A low altitude pass (sea level day) showed us 189 indicated at 35" MAP. My biggest need was for more prop. I have since installed a 54/58 Sensenich which is dropped all my RPMs by about 200. More reasonable. At sea level there is a little bit of prop cavitation on rollout but it doesn't seem to affect it much at all. You do end up with higher fuel burn rates but plugs are much more even burning and engine runs very smoothly. Oil temp control is next...Temps are fine unless I run over 30 " for any extended amount of time. I have a big enough cooler - just improve inlet somewhat. I will be adding a Ram air inlet into the carb system soon to drop inlet air temps. That should improve efficiency a bit. All in all it has been a great experience and fun. I will be doing high altitude testing in the next week or so. Right now we are preparing for our November Syder Engine Workshop and have lots of work on the plate. Go to our website and facebook page for lots more and some videos....
    Ill take some questions....
     
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  6. Oct 28, 2016 #26

    mcrae0104

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    I'm curious, how did you arrive at this figure?
     
  7. Oct 28, 2016 #27

    Mark Z

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    Bill, are you using a 6 point engine monitor? I know that we are talking apples to oranges here but I'm making friends with an EDM 930 in my T-210 and am amazed at the functionality. I've always loved seeing experimenting with the Corvair. Put two turbos on it and you can pressurize that Saberwing. :-D
     
  8. Oct 28, 2016 #28

    Bill Clapp

    Bill Clapp

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    I am just using a single egt and single CHT right now. I can overcomplicate later :) I always liked the T210 - one of my favorite birds to fly but high cost per hour for my pocket.
     
  9. Nov 3, 2016 #29

    DaveP

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    As I said, it was my understanding. I heard it somewhere at a Corvair event. Don't remember who or when, just that it was why we cant run 150 Hp continuous. I'm sure some engineer-type could could research and prove/disprove it. I am just saying that it was my understanding.
     
  10. Dec 5, 2016 #30

    Bill Clapp

    Bill Clapp

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    Turbo Update : Now at around 20 hours on the turbo engine. All well and good as far as temperatures and performance. Once the weather clears I will be doing some high altitude performance checks. I have my on board oxygen ready and instrumentation about ready. (need to make a static port change due to fluctuations - screws up my autopilot in rough air) I hope to get some cruise numbers and service ceiling numbers. The new prop seems to work well so far. Once I am happy with our non-waste gate, fixed pitch prop combination, I will be doing some minor airframe maintenance and also trying a constant speed prop. I'm not sure how complicated I wanted to get with this because you can throw a lot of money after something that only improves performance nominally. However, our prop design will allow for full feather - something I will be need in my twin....

    If you have any questions about our turbo testing please shout out!
     
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  11. Dec 6, 2016 #31

    Mark Z

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    Thanks Bill for the update. What you are doing is homebuilt aviation at its best! See if that thing will fly on the lean side of peak.
     
  12. Dec 6, 2016 #32

    Winginit

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    In WWs manual he says that an engine with a fixed pitch prop can be turbo charged but not turbo-normalized. Any thoughts from anyone about that?
     
  13. Dec 6, 2016 #33

    TFF

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    Im guessing it is probably an engine overspeed management problem not a power problem. Automatically normalized is complex. Fixed pitch is a compromise. Having a controllable waste gate is like having a second throttle where you can taylor the conditions.
     
  14. Dec 6, 2016 #34

    Bill Clapp

    Bill Clapp

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    I guess it can com down to terminology. Stricly speaking WW might be right - Turbo normalization is defined as maintaining standard atmosphere up to service ceiling. From there on the MAP drops as a normally aspirated engine does. You would start by applying throttle until you reach 30" and as you climb increase the throttle until your service ceiling - or full throttle. If you have a wastegate, it can control this variable to some degree. It will bypass excess exhaust until fully closed. The drawback is that with a fixed pitch prop is screws with your rpms. If your prop is set up for good climb rate at sea level, when you reach the service ceiling the rpms will be much higher due to thinner air. Some props and engine are limited as to high rpms. If you have a cruise prop setup for say...10,000', then your engine will not be able to deliver good takeoff rpms due to the higher pitch and thicker air at sea level. Our installation is a compomise...as all aviation is. We use a prop that is pitched for good cruise at 10,000 - but at a slightly higher rpm than what you would consider normal. This is due to having a shorter prop and an engine that does not suffer from high rpms. So, at 9,500 and 30" MAP we turn the prop about 3400 rpms.
    Now at sea level, what we do is slightly boost the engine (up to 36" MAP for now) in order to have the RPMs we are looking for. Now, in our Saberwing, boosting to 35-36" of takeoff is giving us better perfomance than if we were running a normally aspirated 120HP engine. My climb rates are at leaset 500'/min better. WW's point is that to get prop advantage at altitude you would want to boost slightly at seal level.
    Now, a controlable prop can give you the advantage of adjusting your MAP and RPM on takeoff and then the prop will adjust to maintain this though its performance range. However you have more complexity and cost involved. We are going to be testing a couple constant speed props soon since our prop hub design allows us to do that. One prop design is also featherable (for a twin later and motor glider soon).
    Hope this helps a bit
     
  15. Dec 7, 2016 #35

    slevair

    slevair

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    Since turbos work on heat and load and most planes fly at a high percentage of power, you still have the problem of heat rejection of the larger valve seat with less heat sink area. Look at the bridge between the seats on a 140.
     
  16. Dec 7, 2016 #36

    mcrae0104

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    That is why inconel valves have been used in the past in this application. I do not know if they are currently available.
     
  17. Dec 8, 2016 #37

    Daleandee

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    Williams Wynne mentions these on his site in a story about turbo charging from July 2014. He seems to indicate that they are available from Mark Petz of Falcon Machine. Reference here (part 2):

    https://flycorvair.net/2014/07/01/turbocharging-corvair-flight-engines-pt-2/


    Dale
    N319WF
     
  18. May 10, 2018 #38

    DaveP

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    In reading this linked page, I found "built this exhaust System out of 321 stainless. Its future home is on Woody Harris’ 601 XL. He will be retrofitting his 2,850 cc engine with a turbocharger". Does anybody know Woody Harris and if he did indeed turbo his 601?

    Dave

     
  19. May 10, 2018 #39

    Daleandee

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    HI Dave,

    I don't know Woody but I've read quite a lot about his airplane and his adventures. To answer your question; it appears that he never went through with adding the turbo. I found this on WW's site:

    Found that here:https://flycorvair.net/2015/08/26/compression-ratios-fuels-and-power-output/

    Dale
    N319WF
     
  20. May 10, 2018 #40

    BJC

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    pictsidhe and BoKu like this.

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