Wednesday, February 3, 2010

Solved! - A Standard Engine for Homwbuilts

The final piece of the puzzle fell into place when DuraFix altered the alloy of their aluminum brazing rod. The new rod allows us to apply the Fat Fin modification without fear that the extended fins would crack

For those who have not followed the development of this engine, it' specs are as follows:

2332cc displacement (142cid). That is, a perfectly 'square' engine having a bore AND stroke of 84mm. Rod length is 142mm (5.6"). Compression ratio is 8.5:1.

( - 13 February 2010 -
My thanks to the several of you who caught this error. The 'square' engine would b 84 x 84... or perhaps 94x94... but it would NOT be 84x94. [My interpretation of the Standard Engine is one having a Bore of 94mm and a Stroke of 84mm.] So please accept my apology for this gross mis-statement of fact, for which I've no excuse... although I may be able to come up with one, given enough time :-)

The propeller is installed on the clutch-end of the crankshaft. You may fabricate the required spool & propeller hub yourself using the dimensioned drawings contained in the HVX Files or you may purchase them from Great Plains Aircraft Supply Co (GPASCo).

A 20A. alternator is installed coaxially on the pulley hub. The guts of the alternator are taken from a Harley-Davidson motorcycle. A kit of parts, including the required regulator, is available from GPASCo.

The engine conversion includes the HVX modifications. A swaging tool for installing the Toyota valve seals may be fabricated from the drawings or purchased from Mike Sample.

There are a wide variety of carburetors that will work with this engine. Least expensive is the Tillotson Model-X whereas most convenient is probably one offered by GPASCo.

The engine uses either single- or dual-port heads and may use either single or dual ignition. Unless dual ignition is required by local authorities, single ignition is recommended.

The lightest and least expensive ignition system is the stock Volkswagen system based on a mechanical-advance distributor (ie, the -009). This system uses regular ignition points which should be replaced every 100 hours. The system my be improved by eliminating the points using a solid-state points replacement module, or converted to a Waste Spark system using the CompuFire DIS-IX, although the latter is significantly heavier and about 4x more expensive.


The above defines the basic engine. Engines of other configurations will work but the key factor is overcoming the Volkswagens inherent thermal limitation as dictated by the fin-area of the cylinder heads. The 'Fat-Fin' modification provides an elegant solution to the thermal limitation by increasing the fin area.

-2 February 2010


Greg Potts said...

How much of this technology would be applicable to a VW bus engine?

Jim in NC said...

I just now re-found your blog, after your quick post to RAH. Good to see you in print, again.
Where do I go to read about your fat fin modification heads and engine, and do you have a sustainable continuous HP rating ballparked for it?

Jim in NC

flybynightkarmarepair said...

@ Greg: the HVX mods will apply, and your welcome to stroke your engine. The Fat Fin stuff will not fit the stock tin. Neither will the stroked engine, but that's more easily dealt with (commonly done in hot rod VW land too) than the Fat Fin mods.

@ Jim: search the posts for this blog - see that little search tool thingie? Or go to the AirVW Yahoo Group, or the Chugger Yahoo group.

@ Bob: I've got the alternator, but I'm still working on the mounting brackets - Did you convince Steve Bennet to start making those?

jimbo said...

Hey Bob,
Enjoy your postings. Have a question about this being a perfectly square engine. Isn't the bore and stroke really 84 x 94 in order to come up with 2332.

Anonymous said...

very useful read. I would love to follow you on twitter. By the way, did you guys learn that some chinese hacker had busted twitter yesterday again.

Anonymous said...

My question is: what is the new alloy and how do you know what rods have it? And how much does the long fin mod help cooling in an airplane?



Jon in Iowa said...

I may be missing something here, but a 2332 cc engine is in my thinking an oversquare engine (94mm bore x 84mm stroke). A square engine (84 x 84) would not be 2332cc.

Bob Hoover said...

There are too many variables to define this with perfect accuracy but an acceptable method is to assume the Maximum Sustainable Output will be about 75% of the maximum PEAK output. For design purposes it is reasonable to assume an engine having a displacement of 142 cubic inches should produce AT LEAST 71 hp for PEAK power ( ie, cid divided by two ).

Those estimations give us 71hp for PEAK and 53.4hp for CONTINUOUS.

I realize these figures are not as large as those for some other VW conversions but they are in close agreement with REAL engines I have built in the past, and tested using a torque-stand.
-R.S.Hoover - 14 Feb 2010

Bob Hoover said...

** For Greg Potts **

The HVX Modifications were developed for off-road racing and may be applied to an engine installed in a VW bus.

The Fat-Fin modification was developed for VW engines converted for use in LIGHT AIRPLANES and can NOT be applied to vehicular engine, in that the larger fins will not fit under the stock VW tin-ware.

-R.S.Hoover, 13 Feb 2010