Biased Opinions on VW Aeroengines
Please read this
excellent commentary on VW aeroengines before proceeding further. Justin Mace also shares his
thoughts. And this reality
check by R.S. Hoover (Veeduber) is essential.
Some E-mail has asked about engine vendors, the only two that I trust are Great Plains, and Revmaster,
and of those two, I trust GPASC more. Don't forget Limbach engines,
particularly if you are in Europe. The Sonex people have an engine offshoot. Their fixed advance ignition system looks simple and robust, but it makes hand propping impossible. Their CNC conversion pieces look nice in the pictures; I’ve
not seen one of these engines in person, or flown behind one. There is a new Australian vendor, with a Type IV
conversion, driving the prop from the flywheel end with a prop extension and an
outboard bearing, they also have helical gear reduction units.
If you are serious about hauling two people, 1835 cc is the minimum
displacement, and please seriously consider a stroker Type I or Type IV engine.
Subscribe to the VW
Aeroengines mailing list, and read their archives, particularly anything by
Bob
Hoover (not that one, the other one). Here's an example, on head rebuilding
and why you need a spare set of heads. Bob has also come up with a serious of modifications he believes will increase the reliability of converted engines.
There is a promising new
English ignition system on the market that looks appealing for minimum
weight/complication conversions. The Leburg ignition is a bit complicated, but it is self contained, and with motorcycle dynamo bits, self-generating. If you want full electronic control of fuel and
spark, you can have that as well. Probably the best value in ignition
systems is a Bosch 009 distributor triggering a Universal Corporation CDI module. Many are believers
in the Compufire dual coilwaste spark system. Maybe you’re interested in a homebuilt fuel injection
system, but it’s not really set up for the firing order of VWs, although
the previously mentioned Bob Hoover is working a such a system for his ’65 van,
look for his posts in the Yahoo Group on this
project to check on his progress Update: Bob finished his Megasquirt. It ran. He doesn't advocate you do the same.
Anything other than a magneto means you need a generator, or at least a
battery. There are belt drive
Permanent Magnet generators that are small and light on Kubota
and John Deere small equipment.
Vertex mags are supported by Mason Racing, 15 Second Ave, PO 101,
Springmount, PA 19478, 610-287-1511 and Vertex
Repair, as well as by the factory.
Type IV conversions are a bit heavier and more expensive than Type I/II/III
derivatives, and there seems to be problems getting a decent stroker crank for
this engine at an affordable price, but read what Mark Langford has to say
about them anyway. Jack Lockamy built
one for his Sonex and is quite happy about it – or was, until the
crank/sleeve/hub arrangement cut loose and almost killed him. GPASC is working on a fix, but at this
point in time, Winter 2002, there is not, in my opinion, a safe “fan end”
propeller hub/crankshaft arrangement for the Type IV on the market. Driving the prop from the flywheel end takes care of these Type IV specific prop hub problems!!!
If you need more than about 70 horsepower (and that assumes a stroker Type
IV run pretty hard…), you should be looking elsewhere. A Corvair perhaps?
Why should you look elsewhere? The limiting factor is heat dissipation out
of the heads and the exhaust valves. The stock heads are actually superior in
this area to all aftermarket heads I've seen, including the SCAT heads on my
old project. Thermal Barrier
Coatings look like a very, very good idea for (in order of importance)
exhaust valves, heads, and piston crowns.
Just hanging your cylinder heads out in the breeze is a loser. You will
never achieve proper airflow through the heads that way, essential for long
exhaust valve life. Richard Lamb shares how he did it:
I made my eyebrows thusly:
Make patterns for the side pieces. One goes at the base of the jug,
the other goes between the last pair of fins on the head. <Wrong, IMHO – RRY> Or make
them go all the way to the end of the head and add holes for your
sparkplugs and intake manifold. <Better, IMHO – RRY>
Cut the side pieces so that the back end curves around the back
of the rear cylinder. Make the top edge of the side pieces 1/2"
extra for a flange. Bend the flanges by working around the curve
with a pair of pliers or ???
This will cause the piece to curl obscenely! But by working around
the curved part of the flange with fluting pliers, the piece can
be straightened back up! It's so cool.
Mount the eyebrows with a couple of #6 or #8 screws through the fins.
Pop rivet (or drive?) the top covers to the side plates.
Don't forget to block off the bottom between the cylinders. A piece
of stainless or .063 thick aluminum between the fins on top of the jugs
makes a neat place to tie in a piece of safety wire to secure the bottom
baffle.
While
we are on the subject of cooling, please look at this otherwise pretty
sanitary VW installation. The problem I have with it is the lack of cooling
air into the fins that surround the exhaust ports. See the area between the
forward plug, and the forward exhaust valve? That's the most critical area for
cooling, and in this installation, it gets NO AIR. That's not right. Even if
your CHT's look fine, you're cooking your exhaust valves, and the temperature
differential between various parts of the heads will promote cracking. Although
I like and respect Richard, his plane, and his workmanship, his cooling setup as he
implemented it makes this mistake; it doesn’t shove any air into the fins
around the exhaust valves. Since his cylinders are out in the breeze, maybe
he’ll get away with it. Same bad practice here. I wish I had a
picture of prop maker Ed Sterba's
Sonerai engine: his installation had it all done right, with little auxiliary plenums
directing air UP (as I recall) through those exhaust port fins. Blueberry’s engine does it right, Serge Vidal does it right, Jim Hardy’s engine does it right. Look at the way the stock TOP tin is
arranged.
The
baffling patterns Great
Plains sells are essential for any installation, even if the engine is out in
the breeze, you can use the bottom of the patterns to save a lot of time
building your "Elephant Ears". The Aerovee folks also sell baffle plans.
"Super Cool Tin",
available anywhere performance VW parts are sold, is the easiest proper way to
get a decent set of bottom baffles. Ideally, there should be a lower plenum, to build a LOW pressure area on the underside of the engine, with an outlet area 20-30 percent bigger than the inlets.
You
can get brand new 1600 cc
hydraulic lifter engines with full flow oil filtration for about $1400 long
block. It a very tempting idea to just pop a shrink fit hub on one of them and
go fly. GPASC's 1600 cc engine
kits are only slightly more money, and have more parts you need, like prop
hubs; they may be well worth it. A new trend in the VW business is “zero-time”
engines assembled (in the US, generally) with all new parts. You can get them
from many sources,
at nice prices, but they are all solid lifter engines. However, after my
initial enthusiasm for hydraulic lifters in Type I/II/III engines, I’m cooling my
jets on that idea. A correspondent who fitted a BeetleMex “juicer” engine found
the lifters would leak down, and would only pump up after 30 minutes of noisy
running. My own engine will have solid lifters.
I've
been asked about inverted oil systems for VW aeroengines, here
is what I think. More to the
point, EVERY VW aeroengine should have a full-flow filtration
system (NOT an aftermarket pump-filter, although the new VwdoMexico unit
may be good enough), and a full-flow oil cooler,
which could be the stock “doghouse” cooler laid flat with a suitable adapter
from GPASC (although Veeduber points out some drawbacks with this
attractively simple system…), or a J.C Whitney or Mesa stacked plate cooler
mounted …wherever it will fit. Another link on how to full-flow a case.
I
also keep getting asked about turbocharging. The short answer: it's generally a
bad idea on Type I engines, it's marginally less so on Type IV. Turbos put more
heat into the engine than the heads can deal with. There are other complications,
particularly with the oil system. Read this Dan Diehl
article almost 20 years old on his experiences. If you live some place
(South Africa, for instance) where big cylinders and cranks for increasing your
displacement are expensive and scarce, but turbochargers out of wrecks are
cheap, it may make sense; all others should give this a miss. Dan took the
turbo off after a few years, since he was too fast for his buddies to keep up
with it on, and keeping it happy required a fair amount of attention.
Carbs:
A Mikuni HS-42, a Tillotson Model X, a Revflow, or one of the new
Aero-Conversions (Sonex) "POSA
for the new Millennium" carbs. Or the Zeniths GPASC sells. I have more to say on the
subject. And speaking of Posa's, yes, they can be made to work
reliably.
The
GPASC rear drive setup
looks promising. The down side is that a complete package will cost about $500
more than a comparable setup using the Diehl case, there may be a slight weight
penalty over a "full house" Diehl case engine (certainly some over an
X-casting or other bare
bones setup), and there are no cowlings yet to fit this setup - Steve's
working on it. A guy on the VW Aero Engines list is working with one of them,
and in a tractor setup, it's not easy to cowl. May be better as a pusher.
Speaking
of driving from the flywheel end, there is was a German Type IV conversionthat doesdid
just that. And Bob Hoover posted this message on the
subject in the VW AeroEngines Mailing list, along with several related messages
on how to build engine
mounts for this configuration, etc. I strongly believe this is the right way to drive the prop, and the engine I'm assembling will be done this way.
As
an engineer, I’m a little suspicious of the Valley Engineering reduction drive, also sold
by GPASC, but I have not heard any experience-based bad things about it and I
have heard some good. The things I don't like about it are the lack of an
outboard bearing for the crankshaft pulley to keep the belt loads off the nose
of the crank (Subaru redrive experience with this configuration is poor), and
the way it mounts to the case. I
personally like Don Stewarts Maximizer better –
but to be fair, it doesn’t have an outboard bearing either. Those blokes in Oz mentioned earlier will sell their reduction drive, which bolts up to the flywheel end. And the Airdrome Aeroplanes people are now selling a reduction drive.
Volksplane's
have always used a very minimal
approach to conversion. We should all consider the costs versus the
benefits of a more complicated engine.
There
is a lot of technical information about VW engines out on the web; not all of it applies to us.
I
just found this really,
really useful post on cooling on the KRNET FAQ page. The first part of this
rap (I.E. my condensation of lots of research) is just as good, or better. It’s
nice to have your assumptions validated though ;-)
I
said I wasn't going to deal with 1/2 VW ultralights, then I went and listed the
Legal Eagle. In the spirit of
fair play, I'll mention that Bob Moore, and Morey Hummel also have 1/2 VW information, and plans for an early 1/2 VW are available on E-Bay. Great Plains now distributes the Carr plans.
The most important thing to remember is to cut the oil pump capacity way down.
Two
new developments of interest: aluminum (not magnesium) engine cases, and
aluminum (not cast iron) cylinders. The first is heavier, but
stronger, particularly in fatique (the way most cases fail, and fail they will,
in time – why you should NEVER build an engine on a used case). The scuttlebutt
on these Brazilian aluminum cases is VERY mixed, ranging from "they're
awesome" to "absolute junk, never use them again. There are many vendors of these things, and apparently CB Performance has the best product. There are also US
made CNC aluminum cases, twice the price and then some, of new magnesium
VWoBrazil cases, and apparently spotty availability. The second new
development, the jugs, are definitely lighter, WAY more expensive, and
allegedly cool better.
E-mail Ryan
