SV: Supercharged vs. Turbo

["Roland Johansson" <scirocco@mail.bip.net>]

> Ok I know this is a debate that rages EVERYWHERE, but I
thought it'd be
> relevant to bring it up now with the talk about 16V turbos.

> Anyway, a chapter in the book is devoted to turbos and
superchargers for VW
> engines up to 1989.  After reading this chapter, it was quite
clear that he
> favored the supercharger to the turbo.  In fact, he states
"Superchargers
> are inherently better then a turbo for a street-driven
gasoline engine" (p.
> 108).  The main advantage he pointed out for the supercharger
was its
> ability to provide equal boost throughout the RPM range, as
opposed to the
> turbo which has to rely on a wastegate system to provide this
equalization
> (and hence is not as efficient).  There's also the issue of
turbo lag
> (spin-up time), which is nonexistent for the charger.  In
fact, the only
> advantage he cites for the turbo is its ability to perform at
high
> altitudes.
> 

Modern turbochargers if they are put together with right size of
compressor/turbine and for hp numbers below 250 have very small
lag, it is there but not like old Saab 900 turbos of the first
year. More drawback is that you lower compression usually and
that way looses power low end, like going from standing. 
The supercharger in streetdriven cars have a valve that lets the
supercharger off charging when you don't need the power to save
gas and that gives you some 1/10 second or several in lag.

Useful superchargers for VW motors (normal motors between
1,5-2liter) takes about 15-30hp to be driven, the G60 unit was a
good piece of enginering as it only takes 15-18hp to be driven.
When the G60 is not used to boost (you step on the gas) it uses
less parasitic hp.

A turbo is driven by the exhaust pulses in most applications,
not by the heat but to parasitic hp of a turbo is 5-10hp
depending on size and boost pressure when boosting, less if you
only cruise and don't boost.

> Anyway, I realize this is one man's opinion (albeit an
educated one it
> seems), and I'm sure there are plenty of turbo evangelists out
there (on
> this list I'd imagine), but it does make me think.
> 
> So let the debate begin!  What do the folks with turbos or are
doing turbo
> conversions think?  Is it simply a matter of the parts for
chargers not
> being available?  I'm also concerned about the longevity
factor of a turbo.
> Superchargers seem to be more reliable, which is why VW chose
to put a
> G-lader on the Corrado instead of a turbo (which they did
experiment
> with)...
> 

The big issue is cost, you can find a nice new turbo for one
third the price of a supercharger and todays watercooled turbos
last over 200 000kms if you don't realy abuse it with full power
runs for minutes and shut motor off immedatly. Superchargers
last usually longer but if you look at prices you can buy two or
three turbos for the same money. Turbos can be fond for sell
used but I haven't seen a supercharger for sell used if you take
V8 dragster motors off count.

The Corrado/Golf/Passat G60 Polo G40 superchargers aren't as
reliable as VW thought, between 100 000 to 200 000kms they need
to be sent for service at TEC in Germany before they break into
many pieces. This is something that has started to happen the
last years, earlier noone had heard of broken G60 but today I
now ov several.

Why I went for a turbocar is that my previous Scirocco got
damaged in a crash and I needed a new Scirocco, it was the right
price and if you ever been driving a turbo Scirocco and felt
that it accelerates noticable in 5th gear up to at least 7500rpm
(where I let my foot of gas) its hard to not want a turbo or
compressor.

> -tim
> 

Roland Johansson
Scirocco 1,6l TIC -82
Http://hem.passagen.se/toker



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