RE: Supercharged vs. Turbo

[Tim Ebling <tim@surreal.com>]

Hmmmm, I see your point, and it's a good one.  It'd be interesting to see
real world HP figures for typical charger vs. turbo applications, and
figures on power losses induced by the induction system itself.

However, apparently there are those that would disagree that turbos give you
free HP.  Nothing is really free is it? :)

To quote (once again) from the Raven book:

"Contrary to popular belief, turbochargers do not make free horsepower.  To
develop boost in a street application, you will see about 2.5 psi of
backpressure for every 1 psi of boost.  At 6 psi of boost, the backpressure
would be 15 psi.  If you try to run that much backpressure on a normally
aspirated motor, it will choke and die.  The turbocharger does not provide
free horsepower, but it does manage to overcome its own drive losses."

:)

- -tim


> -----Original Message-----
> From: lerb [mailto:lerb@redrose.net]
> Sent: Monday, October 19, 1998 1:32 PM
> To: Tim Ebling; 'Scirocco Mail List'
> Subject: Re: Supercharged vs. Turbo
> 
> 
> Well Tim I look at it this way....when I spin up a turbo I am 
> getting free
> power...What I mean is I am not taking power from my car to 
> produce more...I
> am taking something that would normally be a waste product 
> and funneling it
> through something that will make more power in the end....yes 
> there is a
> little lag and yes there is a tendency to get more power at 
> greater RPMs
> from turbo.....Now a supercharger always robs something from 
> the engine to
> give power. So what would you rather do start out with say 
> 127HP rob 30 to
> get 160 or start out with 127 and not rob any and get 160? I 
> chose not to
> rob any if I can...I can not spare any power loss one little 
> bit....even if
> it means getting it back in the end......If I had  V8 with 
> 300+ HP I could
> see sparring 50-75HP to double the output. Then there is the 
> difference on
> how the supercharger puts out at lower RPMs and the whole 
> debate that if it
> even does anything before the normal powerband of the motor 
> anyways. Hey my
> opinion is biased since I have only seen one supercharged 
> VW...but in theory
> I like FREE power :)
> -----Original Message-----
> From: Tim Ebling <tim@surreal.com>
> To: 'Scirocco Mail List' <scirocco-l@privateI.com>
> Date: Monday, October 19, 1998 4:06 PM
> Subject: Supercharged vs. Turbo
> 
> 
> >
> >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.
> >
> >At the Oktobugfest show yesterday (Puyallup, WA), I was 
> fortunate enough to
> >pick up Greg Raven's "Watercooled Performance Handbook", 
> which someone
> >mentioned was out of print.  What a great book!  This guy 
> seems to really
> >know engines, not just from a practical standpoint, but from 
> a theoretical
> >and scientific standpoint as well.  Bottom line is, I was 
> impressed with
> his
> >knowledge.
> >
> >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.
> >
> >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)...
> >
> >-tim
> >
> >--
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