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Thread: How much HP can a VW engine produce

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    Registered User Joe Kidd's Avatar
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    How much HP can a VW engine produce

    As the lead in says how much HP can one get out of a VW 4cyl engine set up for an airplane? I know much of it depend's upon overall displacement but whats the upper end one can get? I've read that 80 HP was the top end but also have seen 85 and even 100 HP advertised? I know I'm still learning but I'd really tought that about 72 HP was the upper limit. What gives here? Is it the use of redrives or some truly custom machine work beyond the skill level of an average person? Will someone please clue me in because I really like the VW engine but I thought if you were looking for 80-100 HP you had to consider the CorVair engine, which I also like. Thanks, wasn't trying to rant, just confused.

    JK

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    Registered User PTAirco's Avatar
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    Re: How much HP can a VW engine produce

    In direct drive mode you can expect about 60 hp from a 1835cc VW, which is about as big as you can go with the standard crank. This is at about 3200-3400 rpm. With long stroke cranks you can get up 80 hp - anything beyond that and you need to have a re-drive to get at the extra hp the engine may (or may not) be capable of.
    "Aeronautical engineering is highly educated guessing, worked out to five decimal places. Fred Lindsley, Airspeed."

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    Registered User WurlyBird's Avatar
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    Re: How much HP can a VW engine produce

    I have actually been looking at these a bit lately as well. According to the Great Planes website, their 2276cc engine with a redrive will produce 105HP for take off and 73HP continuous. Download their catalogue which has a ton of info in it and have a nice read of it. I think they claim about 400 lb of thrust with that setup.

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    Registered User Firstscout's Avatar
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    Re: How much HP can a VW engine produce

    211hp @ 6000

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    Registered User WileEZ's Avatar
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    Re: How much HP can a VW engine produce

    Actually about 60hp or so, the biggest limitation is not how big (cc) nor how long the stroke is.

    The limitation is in how well you can cool the heads.

    You certainly can product globs of short term power, but once the heads hit the thermal limit, you have to power down or loss it.

    Most of the advertised HP one see out there is take-off HP, not sustained cruise HP.

    Keep the heads cool and it's a fine motor.

    P.S. The 100HP engine had water cooled heads, even then, the continuous HP is somewhat lower, I think 70-75 HP or so.

    P.P.S That 211 HP engine is made for the drag strip, it only have to produce for a few seconds. If that engine ran full power for more than five minutes or so, it will melt! Maybe it wouldn't even last that long!
    WileEZ
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    Registered User Joe Kidd's Avatar
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    Re: How much HP can a VW engine produce

    OK I'd read some of what PTAirco brought up, but he broke it down to a simpler level that makes sense. I've also read much of what WileEZ explained. I did know about the temp problem with the head's as well as the importance of baffeling the engine compartment and engine for proper cooling. WileEZ can you or PTAirco direct me to any detailed dyno work ups on these engines? Super information from everyone!

    JK

  7. #7
    Registered User rtfm's Avatar
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    Re: How much HP can a VW engine produce

    As with everything, there are compromises to be made. Yes, the cost of the engines are attractive, but realistically, the power is down and the weight is up. 161lbs is about as low as it is possible to get full FWF (the Sonex engine is a complete FWF package). And I note that the water-cooled engine is no longer being offered. So that didn't prove to be a winner.

    Bottom line, I think, is that if you want to take advantage of the VW price and reliability - you have to be willing to fly on lower power and higher weight. Which isn't the end of the world - they're not THAT heavy, after all. And their power isn't too bad.

    But for not too much extra, you might look at some of the alternatives.

    Just my 2c

    Duncan

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    Registered User WileEZ's Avatar
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    Re: How much HP can a VW engine produce

    Joe, I doubt seriously that most HP claims were done on a dyno, but is actually guesstimates. Doesn't matter what the engine is.

    Some of the HP guess is done by fuel consumption calculations, but it's mostly done by using some standard values and guessing at what percentage is lost through heat and out the exhaust. A lot of what I have read, even by "experts" apparently shows a serious lack of understanding energy transfers. All HP really is, torque times rpm divided by 5252.

    Right now, I'm thinking that torque is more important than HP, mainly because I don't understand how HP translate into thrust, while it can be shown there's a direct correlation between thrust and torque (in a proper setup).

    There is a lot more I can say about this subject, but I'll rather wait until I can prove/disprove my thinking and have some actual research to point to, either my own or by someone else. Research that can be performed by others and show to produce the same conclusions. When I can show that something is correct, then I'll say something. Else, I'll just ask questions and muse about some train of thoughts and how to verify the thinking.

    In the meanwhile, may I suggest you read this blog series by Robert S. Hoover. Start at the beginning and read all the way through.

    http://bobhooversblog.blogspot.com/2...6_archive.html

    Bob Hoover is a pilot, a homebuilder and a VW mechanic, among other things. What he has to say is very illuminating and I have learned quite a bit from his articles. (No, not that Bob Hoover, the other Bob Hoover!)

    Yes sometime he wander a bit, it's a blog after all, but it's mostly about the VW engine, building airplanes and related matters. It's worth taking the time to read it all if you really want to understand the VW engine as an areo engine. Heck, it's even worth reading if you have an air cooled VW automotive.
    Last edited by WileEZ; June 28th, 2008 at 12:32 PM. Reason: Removed one too many "S"es and fix grammar & spelling.
    WileEZ
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  9. #9
    Registered User Joe Kidd's Avatar
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    Re: How much HP can a VW engine produce

    Thank's WileEZ, I've read through Hoover's material which is one of the reason's I've brought forward my questions on VW engines and actual HP. You make an excellent case for torque, which explains a lot to me. So we have a viable engine for small lightweight single seat and to a point two seat airplanes, just as rtfm say's. I'd really like to learn more on this because I'm leaning towards a single seater airplane due to fuel and materials cost.

    JK

  10. #10
    Registered User rtfm's Avatar
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    Re: How much HP can a VW engine produce

    Hi,
    I think most of us have had to traverse the twisted path you are currently on at one time or another, so you are among fellow sufferers!

    As for me - I was very keen on either the Sonex VW kit or the GPA VW kit. The Sonex was more simple in that it was a complete one-off purchase for everything. The GPA comes very well spoken of, but there was some fiddling about with the basic engine and then additive sub-kits. I decided I'd go with the very sexy-looking Sonex version.

    Then I got to thinking about alternate engines, and the two which looked most promising were the HKS and the RotaMax.

    The HKS seems to be completely devoid of a bad comment - every report on the engine is glowing. It costs a bit more and weighs 121lbs. I was strongly drawn to it.

    The RotaMax appealed to me because being a rotary engine, it has no dramatic failure modes, and one of my missions is to fly across the Tasman from New Zealand to Australia, so reliability ios a major factor to consider for me. It weighs only 110lbs (redrive included), but to that you have to add the weight of the radiator. The single rotor version puts out 65hp, 55 continuous - about the same as the HKS.

    So it came down to cost. And size. The jury is still out, and my cowl is being designed to accommodate either engine. Both are bed-mount.

    So what am I trying to say in this somewhat rambling post?

    If cost is an absolute show-stopper - then I'd go for the Sonex VW engine. If you can reach that little bit further, I'd strongly conside either of the two engines I have mentioned. Thney are both designed from the ground up as aero engines.

    Regards,
    Duncan

  11. #11
    Registered User WileEZ's Avatar
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    Re: How much HP can a VW engine produce

    If cost is an absolute show-stopper, then I'll build one from scratch!

    I would build a flywheel prop engine and last time I looked, following Hoover's suggestions, including the "HVX mods", I think I can build a very nice and solid ~2400cc engine for under $3000. Not counting the starter. Including an aluminum case rather than the stock magnesium case.

    The starter is the only bugger here, but Great Plains sells a starter system for a flywheel end engine.

    I would go with 8.5:1 to 9:1 compression ratio, I think the exact ratio will depend a lot on what plane I'll put it in and my personal "pucker factor"!
    WileEZ
    "All of my ideas are suspect until proven otherwise!"


  12. #12
    Super Moderator Midniteoyl's Avatar
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    Re: How much HP can a VW engine produce

    eh?

    I'm missing something.. I read the blog page linked to and it was about steel tubing, a flashlight, and a tool box...
    Jim

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    Express 2000FT (hopeful - Again)

  13. #13
    Registered User Joe Kidd's Avatar
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    Re: How much HP can a VW engine produce

    Quote Originally Posted by Midniteoyl View Post
    eh?

    I'm missing something.. I read the blog page linked to and it was about steel tubing, a flashlight, and a tool box...
    Try this link, a lot of the Bob Hoover blog information isn't as avaliable as before.
    http://groups.google.com/group/rec.a...72e9a8bcf1c1be

    JK

  14. #14
    Super Moderator Midniteoyl's Avatar
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    Re: How much HP can a VW engine produce

    Ahh... thank you.


    Have to say, I agree with him. I, WileEZ, have my own thoughts on torque and HP in an airplane engine.. and the 'claims' made by peeps selling them.
    Jim

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    Express 2000FT (hopeful - Again)

  15. #15
    Registered User WileEZ's Avatar
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    Re: How much HP can a VW engine produce

    Quote Originally Posted by Midniteoyl View Post
    eh?

    I'm missing something.. I read the blog page linked to and it was about steel tubing, a flashlight, and a tool box...
    Hmm, that was just the first blog. You'll have to read all of the blogs. Yea it takes time, but I did it! And I'll do it again because I know I've forgotten some of them.

    As of today there are 271 blogs (yea I counted them), the blog I linked to is only the first blog, there's another 270 blogs after that!

    Look on the left side up near the top and you'll see links to additional blogs, start with the oldest and read your way to the newest.
    WileEZ
    "All of my ideas are suspect until proven otherwise!"


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