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Re: [T3] Compression Ratio Recommendations

<x-charset iso-8859-1>Hello-

I forgot a couple things in my previous post... sorry... read that first,
otherwise this won't make too much sense.

Two other things that can lead to detonation:
- excessive cylinder temperatures.  Like excessive pressures, if you are
running way too hot, detonation will happen.
- low octane gasoline.  If you lived in 1940s Germany, before the
revolutions in petroleum cracking, then you needed a low CR to keep from
detonating.  Same goes for parts of the world without quality gasoline, like
perhaps some parts of Mexico.

The Type 3's had their CR dropped primarily so that VW had a bigger margin
of error before hell broke out.  Between inaccurate fuel mixture, imperfect
manufacturing tolerances, customers pushing the engines too hard (a Type 1
in stock form is NOT good for a constant 50hp duty) and getting them too
hot, the large variations of formulation in early unleaded fuels, etc., it
was difficult to push the engines to their limit without problems.  However,
if you build the engine very carefully, tune the induction system's fuel
mixture well, remember that the stock engine will overheat if pushed all the
way all day long, use decent gasoline, and watch the head temperature,
running a higher CR is just fine.  I wouldn't recommend 13:1 any day of the
week, but 8:1 or so is fine.  If you are modifying the engine, then
depending on your combination of parts, more *might* also be acceptable.

Take care,
Shad Laws
LN Engineering - Aircooled Precision Performance

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