Hi Chris, Info on the VW as an aircraft engine has been a minor obsession of mine for the last few months as I try to help my son with his KR project. I really like the idea (price/weight/simplicity/aftermarket) of the VW, and there has been a long collected history of de-bugging the aero-conversion aspects of the engine. However, there is are also down-sides: minor to major rebuild every ~300hrs, heat and stress related reliability issues (ending in previously mentioned rebuild), and while the theory is inexpensive mass aftermarket high quality parts, it seem the reality is that aircraft worthy aftermarket parts are pricey (big surprise), and if you have to rebuild every 300 hrs any price advantage is eaten away.
As with everything, experiences vary. Talking with the folks at Revmaster or GP is probably the best source of real information. You can also go through the KRnet archives. There are a couple of valuable internet groups/information sources: Yahoo Group: VW_Conversions - active and great archive of info/opinion https://groups.yahoo.com/neo/groups/VW_Conversions/conversations/messages Bob Hoover - VW engine guru http://bobhooversblog.blogspot.com TheSamba ? huge vw interest group http://www.thesamba.com/vw/ We are getting close to Airventure - certainly the single best place to learn what you need to know. There are hands on classes on rebuilding VW?s. You can talk to the venders, and to pilots flying behind these little engines. My take is that Revmaster is most revised/engineered conversion - i like it. I like their crank/prop hub/and bearing changes. GP has a great rep too and I think the Force-one prop hub / 4th bearing is close to the same deal as the Revmaster. GP appeals a little more the do-it-yourselfer. Besides the crank/prophub/4th bearing issue, nikasil aluminum cylinders appeal to me. great weight savings and better heat transfer. The Revmaster heads sound great to me - but so do the MOFO 50?s: http://www.mofoco.com/item/MOFOCO_050_BIG_VALVE_AIR_COOLED_VW_CYLINDER_HEAD/234/c52 Ignition is still mystery to me. The centrifugal distributor timed electron ignition systems (comp-u-fire, etc) are well thought of, very reliable, and entirely dependent on your battery. If you go with straight electronic ignition, its important to have a backup battery system. I hate the centrifugal distributor sticking up and would like to change to fully programable ei - but I?ve yet to figure out how. I have automotive spark plugs on the bottom side of the 0320 in my Osprey. They are fired off a PMAG electronic ignition. They fowl less than the aircraft plugs fired off the magneto. I like them. Probably the best time/money you could spend on upgrading/tweaking the VW (maybe any engine) is the unsexy issue of keeping it cool. Specifically, pay huge attention to baffling (over, around and _under_), airflow, etc. Get a real engine monitor so you have some idea what?s actually happening to each cylinders CHT and EGT. After that, you might consider ceramic thermal barrier coatings: top of piston, top of combustion chamber, valve faces. Also pay a lot of attention to making sure the engine and prop are balanced in order to minimize stresses (crank, bearings, case, etc). While its tempting (at least to me) to focus on cool expensive mods to the engines (like heads, nikasil cylinders, cranks, tunable ei and fi, etc), I think real world experience will be best improved by focusing on the little things like baffling, balance, carburetion, oil flow and cooling, prop and engine bolt torque, etc., and proper/thoughtful operation. Finally, your note on not wanting to move the engine forward goes against most of what I read of the KR?s tending to need their CG?s moved forward. Cheers, Owen Hughes > On Jun 19, 2016, at 9:00 AM, krnet-request at list.krnet.org wrote: > > Date: Sat, 18 Jun 2016 11:29:50 -0700 > From: Kayak Chris <kayak1176 at gmail.com <mailto:kayak1176 at gmail.com>> > To: KRnet <krnet at list.krnet.org <mailto:krnet at list.krnet.org>> > Subject: KR> VW engines questions > Message-ID: > <CAF6k7fRZjWiYy=CwJ-SXoLZUJ0Vqk4MLdh+_tJAT5vgakxsV9A at mail.gmail.com > <mailto:CAF6k7fRZjWiYy=CwJ-SXoLZUJ0Vqk4MLdh+_tJAT5vgakxsV9A at > mail.gmail.com>> > Content-Type: text/plain; charset=UTF-8 > > Few VW questions, anyone know any significant differences between > Great Plains and Revmaster approaches to VW Type 1 engine? > > In particular, Revmaster has a hemispherical chamber and improved > alloy in the heads. Wondering any feedback on that. > > Also, would welcome any comments on ignition types, aircraft plugs vs > automotive, dual ign/plugs "required"? > > And as far as electronic ignition, major pros and cons, and do those > have knock sensor options in this application? > > One last thing, ken rands KR1 had the mag as belt driven and up high > so the engine could be against the firewall. I would like not to > extend the engine mount out just to accommodate a huge center magneto, > so anything which speaks to this would help. > > Sorry for the newb type questions but I'm at where I'm at and some of > this info could be quite new. > > Thanks! >
