Yet another VW power argument. Again.

Discussion in 'Volkswagen' started by BoKu, Nov 18, 2015.

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  1. Nov 20, 2015 #41

    dino

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    How well does the type 3 magnesium crankcase handle the bore of 94mm? I understand from their website the case has been modified. Besides machining for bore and clearance, is there anything else involved?

    Dino
     
  2. Nov 20, 2015 #42

    Pops

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    Well said.
    You can build a VW engine and not have one part built by VW. Same for a Small Block Chevy, etc. About the only VW make parts in my VW engine is the crank and block and heads.

    Dan
     
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  3. Nov 20, 2015 #43

    Jake Levi

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    Fascinating thread, my expertise isnot engines, its critters, how they are built, not remotely mechanical.

    That said I have been thinking of a 2100 VW engine to provide ` 70 HP for my low and slow homebuilt, with up to 80 for take offs etc and throttle back f or flight. The Revmasters are beautiful, but almost half more then what I want to spend.

    So is the 2100 VW wishful thinking or doable for a nice long life?

    Inquiring mind wants to know , just what is doable, not pie in the sky, or in my eye.
     
    Last edited: Nov 20, 2015
  4. Nov 20, 2015 #44

    Topaz

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    Talk to Great Plains Aircraft. Talk to AeroVee. Talk to Hummel. Given that you're looking for an engine on the very top of the power band for a VW, you don't want to try doing this conversion on your own, unaided. If you wanted a 50-60hp engine, sure, knock yourself out. But if you're wanting 70 hp continuous, you want a conversion by someone who knows what they're doing.

    Hummel Engines price list: hummel (All power ratings are takeoff power. Write them for continuous ratings. I did. They're very helpful.)

    Great Plains Aircraft: Welcome to Great Plains Aircraft! (Probably the most-experienced converter out there. Their kits can save you a lot of money.)

    AeroVee: AeroConversions Products -- Power to the Sport Pilot! (AeroVee is saying that they get 80hp continuous from their engine. They also note a TBO of 700-1200h, so obviously this engine is being pushed harder than the others.)

    Here's where it pays to define your terms. Does "doable for a nice long life" to you mean 2000h TBO, because that's what certified engines get? Or is 1200h TBO acceptable? I've already noted that 1200h is more than the entire life of many homebuilts and, at any rate, about 10-12 years of use for the average pilot. If 1200h is long enough, and you use a reputable conversion from an experienced vendor, installed properly, yeah, you'll very likely be just fine. AeroVee's engine seems to have a shorter real-world TBO but, then again, a VW overhaul is pennies on the dollar of that for a certified aero engine, and we're still talking 7 to 10-12 years of average usage before overhaul. Up to you which way you want to go.

    The other thing to think about is if this is really a good engine for your airplane. If 70hp is the bottom end of the recommended installed power for it, this is probably a bad choice. We had a guy in here once who "had a friend" who put a mid-sized VW (I think it was 1835cc?) into a CH750, because, at the time, Zenith was saying the airplane "could be flown" with as little as 60-70hp. Now, Zenith says you need 80-120hp for that airplane. Well, this whiz-kid burned up his VW because he obviously had to run it pretty much WOT all the time, surely blowing through the takeoff power duration operating limitations in the process. And then his friend came here onto HBA and was screaming what awful engines VWs were, and how unreliable they were, and how he just happened to be developing a head kit that would allow them to produce "more than 50hp, which is all they can really make, according to ..." you guessed it, Bob Hoover. Was burning up a too-small engine installed in too much airframe the engine's fault? Nope. You could arguably say it was Zenith's fault for low-balling the installed power spec, but it was really the pilot's fault. He's the one that burned up the engine with his own hand on the throttle. The operating limitations have to be respected. Period. Or you'll burn up your engine. That's true of any operating limitation on any engine.

    If your airplane can really be comfortable with 70hp or so, including on a long, extended climb-out, then yeah, you should be okay. If your airplane really needs 80-100hp, and you're just trying to save some money, don't do it. You're going to be disappointed in the end.
     
  5. Nov 20, 2015 #45

    Pops

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    Revmaster has been in the VW aero conversion business far longer than anyone else. 1959.

    ยป Company



    Steve at Great Plains said to prop your VW to cruise at 21" of MP. Steve knew what he was talking about in most anything about VW's. Just like Bob Hoover, Steve is going to be missed.
    Dan
     
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  6. Nov 20, 2015 #46

    Jake Levi

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    Thanks Dan

    Your comments of 1200 hrs TBO is what I'm hoping for, figure ~ 4mos a year I wont be flying, cold winters here. And 70 mph av flight is fine with me with 80 or so at climb out, most closer to 50. As I said low and slow, with a plane weight of approx. 720-800lbs empty , and a STOL wing.

    Thanks for the links, I'll be studying all of them. My first thoughts were with a Corvair or Mazda but was seeing a lot of good things written about the VW.
     
  7. Nov 20, 2015 #47

    Jake Levi

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    Hi Dan

    A LOT of food for thought here, one thought is that I don't want to get over-engined, I don't see making any trips over ~ 650 miles total, that's about what it is to Oshkosh, and a cruise ~ 65-70 mph is fine with me, a lot of beautiful country to fly over on the trip, and no heavy traffic on the roads. Once a year is about all that would be.

    To make a long story short, 70 mph would be a near max cruise, 80 mph take off would be good, and throttle back to slow cruise. I can see a lot of 60 mph, or slower flight speeds.

    Thanks for your comments, I'll be looking hard at your links, the Hummel is interesting, we shall see.
     
  8. Nov 20, 2015 #48

    Dana

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    Power affects takeoff performance and rate of climb far more than it affects cruise speed.

    Dana
     
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  9. Nov 20, 2015 #49

    Pops

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    My little single place airplane cruises at 75/80 mph, climbs 1200 FPM and burns 3 GPH at cruise. I have flown cross country with my 2 neighbors in their Pietenpols. I have to run back to 2450-2500 rpm to stay back with them from my normal cruise of 2700 rpm. I can out climb then by quite a bit at my cruise power when they are at WOT.
    Dan
     
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  10. Nov 21, 2015 #50

    Klrskies

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    The vw engine has evolved dramatically from it's humble beginnings...in the changes VW made to it and what the aftermarket has provided. The crank case itself provided by vw came in two different grades of magnesium alloy. The early case was die cast from AS41. it was adequate for early models that didn't generate more heat than the case could endure. Since a portion of the heat generated by combustion is transferred by the oil and cooled as it gets dissipated about the inside of the case and thru the oil cooler, the case can only handle so much heat...less than some of the modern synthetics can tolerate. As emissions restrictions forced leaner/hotter combustion temps, and the displacement increased, VW changed over to a stronger, more temperature resistant alloy, AS21. that change was costly as AS21 is more difficult to machine than AS41. the material type is cast on the side of the case so one can distinguish between the two. Magnesium alloy is great for weight reduction but as it's temperature is elevated, it looses it's strength. If the material begins to weaken at high loads under high temps, it allows distortion. The head studs can pull out of their threads, the case halves can begin to shuffle against each other at the parting lines, called fretting...this rubbing of the case halves against each other, displaces material, causing case studs to loosen and pound the main bearings into the soft case. Heat is the enemy of the VW. it's a testament to those who have sorted out many designs that contribute to minimizing temperatures and extracting it efficiently. The new aftermarket ALUMINUM cases are much more heat resistant. The type 4 case is aluminum for that reason...despite it's increased weight. The aftermarket cases allow more room for stroker cranks and bigger cylinders, and extra head studs. The engine has evolved incredibly over it's 80 year existence.

    The engine was conceived as a big bore/ short stroke configuration to reduce friction...another source of heat that would need to be dissipated. High torque/low rpm applications like having stroke to generate force to turn the heavy, long mass of a propeller. Bigger crankshaft main journal diameters handle the torsional resonance induced by the firing impulse of individual cylinders against the mass of a propeller. That resonance has to be controlled by a strong crankshaft and engine case. Over heating MAGNESIUM alloy makes that impossible. The trick in the engine being able to endure high loads is in understanding how much heat the materials can tolerate and improving upon handling it's dissipation.

    Its not fair to compare the humble original configuration constraints of the early automotive applications to the re-engineered, aviation configurations. I think Bob Hoover would agree.
    Ken
     
    Last edited: Nov 21, 2015
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  11. Nov 21, 2015 #51

    Pops

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    Yes, I think Bob Hoover would agree.

    Dan
     
  12. Nov 21, 2015 #52

    Jake Levi

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    Dan and Dana, rate of climb is also contributed to by plane configuration, I am a neophyte in this, but do know that the STOL wing, with its thickness, chord length and ailerons will assist the climb considerably. Which is why I have been looking at the 1835 or just larger for my project. Low and slow is my venue, not speed. Its also a 2 seater. That said, I am enjoying this thread, thanks for all of your input.
     
  13. Nov 21, 2015 #53

    saini flyer

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    What Dan did is a very good example of how to go about solving this problem. Use a large prop but constrain yourself to lower RPM. You loose power but gain thrust where its needed. You are not going fast anyways. Have you looked at the double eagle and cabin eagle with the VW.

    I also saw your other post on Jabiru2200. I am not an engine guy and am always looking for a complete FWF setup. Different engines have different issues. Jabirus are not perfect either as evident from the recent events. Just like you, I want to compare the 80-85HP VW to the 85HP 2200. SOnex website gives the same empty weight of the finished aircraft with both the engines. The VW is some 30 lbs heavier and I think that is where the comparison starts and ends. Both running at 3400 to 3600RPM and same volume gives the same HP.

    I really want to know if there is a magic bullet that builders use to decide between VW and 2200 besides weight and cost. Why bother with spending $10k more on 2200. What am I missing?
     
  14. Nov 21, 2015 #54

    Topaz

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    Couple of things, from my point of view.

    First of all, virtually all the VW-derived engines out there that put out "80-85 hp" are doing so as takeoff power ratings, not continuous power. I cannot stress enough that you must recognize and respect that operating restriction on VW's. I'm not sure on the Jab, but it's likely able to put out 85hp all day long as a continuous rating. That means the "two" engines are not actually comparable at all - the Jab can maintain 10-15 more hp than even the largest VW conversions. AeroVee's conversion says 80hp continuous, but that's paid-for with a lower TBO.

    (Pops, I'm not speaking to the newer Revmasters simply because I don't know much about them. I know of the older versions that the company put out in the 1980's, but not the "new" Revmaster's products.)

    Secondly, the Jab is lighter. In weight-critical installations, that can be a deciding factor.

    The point in using a VW in a given installation is that the purchase and life-cycle cost will be much lower than pretty much any other engine in the power class. You "pay" for that cost savings with a concrete operating limitation on how the engine is used, somewhat more-frequent overhauls (that cost far less, however), and more weight for the power.

    You spend $10k more on a Jab if your airplane simply cannot accomodate the weight of a VW, you really need the extra 10-15hp beyond takeoff (extended climbs, for example) in your particular use-case, or you insist on a purpose-designed airplane engine.

    If your airplane needs 85hp continuous power for the way you use it, a VW is probably a very poor choice. You'll end up flogging the engine to death, and that death is going to come fairly quickly. 85hp is just asking too much of too small of an engine. A Jab is worth the extra $10k in that case, because you really don't have much of an alternative available.

    On the other hand, if you've got a really small and light airplane, in the vein of the Double Eagle or a KR-2 built and operated to the original weight specifications, a Sonarai (same weight comment), or suchlike, an appropriately-sized VW can be a very economical choice.
     
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  15. Nov 21, 2015 #55

    Dana

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    Yes, of course climb is affected by configuration. My point was in response to you saying you don't want to be "over engined" and then talking about speed... a bigger engine won't make you go much faster, but it will have a big difference in your ability to get out of a small field, or climb over mountains between here and there.

    Dana
     
  16. Nov 22, 2015 #56

    Vigilant1

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    The Sonex community experience may be of interest. According to the Sonex LLC database, the total of all completed reciprocating-engine models (Sonex, Waiex, Xenos, Onex) is 536. Of those:
    Jab 2200: 62
    Aerovee (normally aspirated): 250
    Revmaster: 2
    Great Plains: 0
    VW "Other": 20

    Bigger engines:
    Jab 3300: 186
    Corvair (all displacements): 1
    Rotax 912 S: 1
    Rotax 912 ULS: 1
    UL Power UL260iS: 1
    D-Motor (all): 0
    Aerovee Turbo: 2

    The numbers above are not 100% accurate--they were logged when a builder told Sonex what they had finished and flown, and not everyone did that, and owners often didn't notify Sonex if they later changed engines to something else. Also, some owners aren't eager to self-identify to Sonex that they've put something unusual in the plane. But the Jab 2200 and the Aerovee were installations that were both fully supported by Sonex, and you can see that the Jab 2200 was not nearly as popular as the VW-based engines of similar TO power. Also, I think a higher proportion of Jabs were sold in Aus (where it is made) and in places that might not have a robust VW aftermarket. Also, the Jabiru 2200 puts out its max HP and max torque at lower RPMS than a typical VW, so it might be more attractive in a plane that flew slower but swung a bigger prop than these Sonex models.

    But the answer to your question about Jab 2200 vs VW engines might be found above. In the US, the VW-based engines are a very attractive value proposition when it comes to purchase price $/hp and also in the cost of repair parts. A new head for a VW (for two cylinders, with all new valves, seats, springs, tapped for a second spark plug per cyl, etc--ready to bolt on) generally costs about $300 = $150 per cylinder. A head for one cylinder for a Jab 2200 costs about $700. Similar costs differences exist for valves, gaskets, etc--about anything you might need to keep an engine running.
     
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  17. Nov 22, 2015 #57

    Pops

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    Can do a major overhaul on a VW for about $700. That includes new pistons, pins, cylinder, rings, rod-main-cam bearing, gasket set, oil pump, valves and valve guides and something to drink while you are doing the work.

    The 1835/1914 VW engine is the most bang for the buck.


    Dan
     
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  18. Nov 22, 2015 #58

    radfordc

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    Another reason the Jab 2200 isn't used as often in Sonex's is that it's too light and makes for an aft CG situation.
     
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  19. Nov 22, 2015 #59

    Turd Ferguson

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    Good luck with your project. A plane that will carry two full sized US adults on VW power is an elusive bird. If you can pull it off, you'll have a hit.
     
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  20. Nov 22, 2015 #60

    Klrskies

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    They are taking an aggressive stance on modifying the vw based engine to withstand full loads...redesigned case, crankshaft, cylinder heads...must cost a fortune, but hp ratings are high. It's interesting to see how heavily built it evolves into with the design focus becomes reliable, sustainable, maximum, obtainable power. But it comes at a price...money and weight.
    Ken
     

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