Turbo engine "theory"

[C M Smith <cmsmith@domain.elided>]

Not a theory.  SAAB, Volvo, and now VW are proving that turbo is the way to 
easy high performance engines every day with high torque, well built turbo 
engines that last easily as long as aspro engines. Yes, the pound for pound 
includes those huge and heavy turbos (about 3 pounds each I would guess, 
one is enough for a four, and smaller is better for turbos for the street) 
and the air to air intercoolers (aluminum, filled with surprisingly light 
weight air) and the engines require no special cooling requirements beyond 
the usual water/glycol radiator operating at normal rad pressure cap 
pressures, (turbos are actually thermally more efficient than aspro engines 
as heat energy is extracted from the exhaust, the turbo itself gets hot and 
so does the engine compartment, but the total cooling load on the  cooling 
system is actually lower, per unit of fuel used.)

My own personal experience with three turbo cars is they are trouble free, 
at least as trouble free as aspro engines. With modern electronic engine 
management it is simple to turbo a well built street engine. Not so simple 
is to extend the rev range of an aspro engine in order to extract more 
useable torque out of it. Variable cam timing is now essential, as are very 
strong engine internals to enable the con rod bearings to survive the 
inertia loadings of relatively long stroke cranks reversing the pistons at 
8,000 rpm at TDC with both valves open (can you spell "bang" in US dollars?).

As for torque and horsepower, well they is related you know. In fact hp and 
torque are directly related and proportional to rpm. Torque is the only 
thing that counts for acceleration rates. Power only matters at high speeds 
(if you doubt this try beating a Magnum V10 pick up across an intersection 
sometime) and is largely irrelevant for street driving. Even a 120 hp will 
get you well over 120 mph these days with modern body designs. Case in 
point is the SAAB 9000 Turbo which easily reaches 137 mph (220 km/hr) with 
"only" 160 hp, and gets to 60 in about 8 seconds from a standing start, 
turbo lag and all. Real world roll on acceleration is even better as the 
torque curve is fairly flat. Later 9000T models are even quicker, 
especially on roll on. My SAAB Aero surprises quite a few "muscle" car 
drivers if we begin accelerating at say highway speeds, eat my dust you 
aspro weakling.

These days a good turbo engine of 2.0 litres will easily run with an aspro 
3.0 litre, last as long, and be as trouble free. At the top end the turbo 
will usually easily outdrag the aspro engine until the rev limiter cuts in, 
and the lighter overall package (my Aero is easily 10% lighter than the 
slightly smaller 164L I own) handles much more nimbly (but those negative 
cambered front tires on the 164 do hold on better, just for less than half 
as long in tread wear!)

Now, not to say I don't prefer a highly strung very high output rev like a 
maniac aspro engine to my stump pulling SAAB engines. But the point 
responded to was more along the lines of "which one works better.....


Michael Smith
Calgary, Alberta,Canada
91 Alfa 164L
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