Date: Fri, 8 Jul 2011 08:46:28 -0700
Reply-To: Don Hanson <dhanson928@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Don Hanson <dhanson928@GMAIL.COM>
Subject: Re: Superchargers?
In-Reply-To: <BAY152-ds61D33214622E7CD47F373A0400@phx.gbl>
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I've done some more reading on this Supercharger subject around the
various VW forums. Just 'surface reading' and not real research but I am
starting to get some ideas, some sense of what VW guys are saying about
these types of engines. Being Friday, here's some more thoughts on this
subject that no one seems to have applied to a Vanagon...yet.
I think "Turbos" seem to be more 'cool'. I don't mean their
temperature. They are accepted, and it's 'cool' to say..."I drive a _______
Turbo" That sounds better than saying, "I have a ___________ with a
Supercharger on it" Many vehicles do have space limitations, too, as
Dennis says. It can be difficult adding a supercharger to a vehicle,
spacewise. A vehicle with PS pump and an AC compressor and a tight engine
space .... finding room for the SC and it's drive belts and plumbing, that
presents a challenge. I get the sense that the compromises made necessary
due to available space, those compromises are sometimes the cause of
problems. Picture the 1/4 mile dragsters. They don't have to bother with
any of that and they simply mount the supercharger in the best possible
way...right on top, driven by the front of the crankshaft with one big
direct belt...Simple..Big ole scoop, right in the fresh cool air. Quite
different than trying to fit that blower into say a GTI Rabbit or a 911
Porsche or a Nissan NSX..etc.
It is said by many, on the various lists I've been reading, that the VW
superchargers aren't that well done. They have some longevity issues. The
VW superchargers are often replaced by aftermarket. There is a selection of
these that have none of the VW supercharger's known issues.
A couple of characteristics of a supercharger make it attractive, to me at
least.
Smooth power delivery over the rpm range is a significant attribute. I've
raced against turbocharged sports cars and they always had to contend with
"turbo-lag" I've driven them and working around that turbo lag isn't
good. Very modern turbos have 'mitigated' that lag by robbing power at
peak, by adding a second turbine wheel ("Twin-Turbo") by 'chipping' the EMS
to eliminate the "Hit" that comes from a turbo when it comes on to
boost..waste gates...all kinds of 'band-aid solutions' I find it appealing
to have power delivered in a more linear fashion by the belt (or in some
cases, gear).
Power at high altitude...I think the first superchargers were built for
airplane motors. Made to overcome the power loss as those airplanes climbed
up to higher altitudes. Way back there were supercharged airplanes, there
may still be some. Anyway, at higher elevations, forced induction motor do
outperform, significantly, normally aspirated motors. I am not sure of the
scientific reason, but forced induction motors really do lose a lot less
power as they go above about 5000' elevation... I would often beat twin
turbo Porsche 993s and 996s at Portland or Thunderhill , Laguna Seca or
Infineon, or the other tracks at near sea level with my big displacement
normally aspirated 928 Porsche, but at Reno or any other high elevation
venue...they were more powerful in comparison to me and often faster...
Expense...it seems to me that adding a supercharger to an existing VW
motor might be a more economical way to get some extra power without a huge
outlay of cash and time. Transplanting a different brand motor into a
VW...No one can say, truthfully, that that is simple or inexpensive, by the
time it is all sorted out 100% and running properly. I think, according to
what I see, that if you don't go crazy with the boost and drive like a sane
person, supercharged vehicles work just fine. There are plenty running
everywhere that have drivers who don't even know they have a supercharged
motor... If you set up a motor with just a few lbs of boost....you'd likely
get a few more HP and just a little less durability....
Just Friday rambling here... Don Hanson
On Fri, Jul 8, 2011 at 5:16 AM, Dennis Haynes <d23haynes57@hotmail.com>wrote:
> The turbo also has parasitic losses. The exhaust has to be pumped through
> the turbine. They both have pros and cons. Supercharger advantages include
> boost there all the time and consistent with engine rpm, does not lag. Also
> exhaust heat does not get transferred into the incoming air. A Downside is
> they take up room and need to be positioned so engine can drive it.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Rob
> Sent: Friday, July 08, 2011 3:17 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Superchargers?
>
> I've often wondered about the 'why' with a supercharger.
> The supercharger takes horsepower off the front end (parasitic) to operate
> and a turbocharger gets it's power from the engine waste. I can see why the
> supercharger was used on the Pratt & Whitney R1820 but on an engine with a
> (relatively) easy to tap exhaust stream why use a supercharger?
> Just wondering ...
>
> Rob
> becida@comcast.net
>
> At 7/6/2011 08:13 AM, Don Hanson wrote:
> > Anyone have any experience with superchargers on a VW?
> >Turbochargers get all the ink..everyone talks about Turbo Subies and
> Bostig
> transplants.
>
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