Old news.

As far back as Rockford, at least three builders of converted VW's
appealed to Pope Paul to use the EAA's bully pulpit for educating
homebuilders about the realities of automobile engine conversions. At
least two of us (me and Ted Barker) even offered to provide the
required torque-stand. But the EAA was (and is) more interested in
selling tent-space and full-page ads than in contributing to the basic
store of USEFUL homebuilt information.

My article you cited (The Christmas Engine) can be found at...

http://wapurl.co.uk/?IWL54GJ

....and I suggest you give it another read, paying particular attention
to the difference between PEAK and SUSTAINABLE output, and how long
you can expect to pull the former... if you're interested in a
reasonably long TBO.

As for the question of direct-drive vs a PSRU, I'm afraid you're a bit
behind the power curve, engineering-wise. Adding a PSRU does not
change the laws of physics which dictate the power & durability of an
engine. The use of a PSRU can allow a small engine, such as the
1300cc Rotax, to produce a prodigious amount of power, but only so
long as the waste heat is properly managed, which Rotax does by using
liquid-cooled heads... and lotsa money :-)

As for your expectation of discovering "the truth" by popping up on
the internet and polling the readers, you're about to get a valuable
lesson in human nature. After having paid $6000 US for what is
basically a $2500 dune buggy engine with a fan on the nose, an awful
lot of people are going to swear on a stack of Bibles that the
miraculous claims of power and durability that caused to spend that
amount of money are ALL TRUE. Never mind that their Specific Fuel
Consumption is 0.562 (or worse), or that they have to 'touch-up' the
valves now and then... because if that miraculous amount of power and
that remarkable TBO were NOT true... it would mean they were suckers,
being preyed upon by another EAA-endorsed huckster. And of course,
that can't be right.

For everyone else, as I said at the out-set this isn't a new topic.
Dig around, you'll find lots of valuable, quantified information here
and in the archives of the AirVW Group. You will also find lots of
the other kind of information as well, including full-page ads in
early issues of 'Sport Aviation,' along with infomercial 'articles.'
Read it. THINK FOR YOURSELF. Your life may literally depend upon it.

The saving grace in all this is the fact an engine is incapable of
lying. Build it, fly it, and what you see is what you get. Oddly
enough, what you get will come remarkably close to what physics,
thermodynamics and engineering has SAID you will get -- and have said
for the last hundred years.

-R.S.Hoover