[Vwdiesel] Powerplant Trades

[Val Christian]

Aircooled vs. water jacketed...the trades are simple.

Aircooled: less weight, lower manufacturing complexity, looser engine 
tolernaces, noisier operation, shorter life, less stable engine temps.

Work OK for airplanes, chainsaws, and low milage cars.  (Didn't Saab
have a 3 cyl aircooled engine?)

Waterjacketed: weigh more, increased manufacturing complexity,
tighter tolerances, better engine temp maintenance, quieter
operation, longer life.


Then there is the trade space for Otto Cycle and Diesel Cycle Engines.

They fall into a couple of categories:

-manufacturing complexity (higher for diesel, given the current state of the
industry)

-maintenance complexity (lower for diesel when averaged over the life of
a properly maintained power plant)

-wear limits (graceful degradation with the Otto, which tends to start
more easily than a similar condition diesel)

-power characteristics (torque, RPM trades, plus duty cycles, startup
times, engine cycles, etc.)


Well, our discussion could go on forever.  But there is the OTHER
compression engine.  The turbine.  I don't hear of too many people 
running these.  Yet, they are used in some powerplants, including
some train engines (traditionally diesel in recent years (bar electric))
If I could just get my hands on a nice turbine, with, say 40 hp.
It would probably outperform a 48/52 hp vwdiesel IDI in auto applications.
At least for highway drivability.  Remember, max torque at lowest RPM.
Who needs a gearbox (save reduction gears)?  No more complex at starting
than a diesel, although a hotstart has greater consequences.  The real 
thrill is the noise you leave behind.  Then again, a 48 hp vwdiesel
IDI without exhaust is a thrilling car...

Val

ps: I bet we can burn veggie oil in a turbine.