Date: Tue, 5 Jun 2007 13:19:53 -0400
Reply-To: Jim Akiba <syncrolist@BOSTIG.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Akiba <syncrolist@BOSTIG.COM>
Subject: Re: 102mph - Turbo vs. 6-cylinder
In-Reply-To: <1181026465.466508a140e17@www.stonebow.otago.ac.nz>
Content-Type: text/plain; charset="us-ascii"
While there is no direct correlation as a generalization, in this case there
is. And quality is only part of the equation, if you don't have numbers too
it won't matter. If there was only 1 SVX engine, this discussion would be
entirely different, so it is undeniable that numbers are important to assess
just as quality is. You want both, you need at least one. So the SVX is
great, high quality, reliable, but so is the zetec which in addition has
huge production numbers. That's why you'll pay more to buy, prep,
recondition, and maintain your SVX engine. If you're ok with that great, but
it is higher risk $$ wise. Also the zetec isn't a Ford North America engine,
what do you mean by "basic US stuff"?
As far as only recently been equaled in power, what about the 3.2L Yamaha
six used in the Taurus SHO starting in 1993.. that's another 6 right along
the same timeframe as the SVX, and has almost identical power/cubic inch?
As for small turbo 4s lacking bottom end, while your observation is true, I
don't think the statement is. You have likely seen only small turbo 4s that
lack bottom end, but that's because OEMs need to find a balance between
torque and peak power... WRX drivers don't want a truck engine because
they'd lose HP and mid-high rev drivability which is what the car is built
for. If you drive a WRX insisting on a characteristic that it doesn't have,
you will of course be disappointed looking for it. It must be driven at
higher revs to be good around town, I think they are great around town, or
on a road course. You could make more low end on a WRX engine, but with a
turbo small enough to build the power that vanagons are best suited for
you'd run into the surge limit of the turbo(unless you have VGT), which is
precisely what we are approaching in sizing the turbo for the zetec. We will
knock the rev limit down as a result, because most people, especially those
with plenty of low end, won't need/persue revs above 6k. There's always a
compromise, and the torque for peak tradeoff IS worth it in vanagons. The
characteristics of power production with a turbo are largely the turbo
selection accounting for the as-built engine characteristics themselves,
which aren't inherently one way or the other within a cylinder layout
paradigm(such as inline 4 etc). Not all small displacement 4 cylinder engine
have the same rod to stroke ratio, comp ratio, intake tracts, camming,
valving, etc so not all inline 4s.. or indeed all opposed, or v8s, v6s
whatever should be characterized in such a way, despite the tendencies
observed in various implementations. It simplifies things too much. If you
had thrown in a "generally" preceding then the statement is true.
Also does anyone have a dyno chart from an SVX install in a vanagon at all?
I've never seen one.
Jim Akiba
-----Original Message-----
From: Andrew Grebneff [mailto:andrew.grebneff@STONEBOW.OTAGO.AC.NZ]
Sent: Tuesday, June 05, 2007 2:54 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: 102mph - Turbo vs. 6-cylinder
Numbers hardly equate with quality. ZETECs are basic US stuff. The
3.3-liter Alcyone SVX engine is well-proven for reliability and has only
recently been equalled in power output by other similarly-sized sixes.
Small turbo fours (eg Impreza WRX) lack bottom-end and have peaky power &
torque delivery... making the stock cars difficult to drive in town, much
less a heavy van fitted with such an engine.
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