Date: Tue, 25 Jan 2000 09:55:51 -0500
Reply-To: Bob Donalds <bostneng@FCL-US.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bob Donalds <bostneng@FCL-US.NET>
Organization: Boston Engine Exchange
Subject: type 1 verses wbx RPM
Content-Type: text/plain; charset=us-ascii
Charles Hokanson wrote:
>
> you know the more I think about it, the less I think it is true that
> aftermarket poweer mods for T1s come at higher RPMS. In fact, I don't think
> most T1 folks like to rev their motors as high as we do. Case in point: I
> mentioned to an old friend (who owns an aircooled speed shop, but has no wbx
> experience) that I had to run 4k RPMs to get to 70 and he said emphatically
> "Dude, you can't run those kinda Rs -- Itt'll come a part". And this was
> from a guy who built a T2 that used to tow his baja UP an steep grade and
> pass everything. So, although I do no have the dyno sheets to back any of
> this up, I hereby retract my agreement that aftermarket mods come at the high
> end in the majority of cases -- I don't think that is true. CHarlie.
Charles and the list
I'm sure that the type one engines see the higher RPMS when going
through the gears. The type 1 engines can't take sustained highway RPMS
of 4k or it will overheat and have a very short life. I run both my air
and water cooled van engines at 4k all day long on the highway no
problem. A max RPM of 3000 or 3250 is ok for the type 1 on the highway.
You can bounce a stock type 1 engine of 5k with little ill effect with
the exception of pounding the valve train. keep in mind the power starts
to drop off at 4k on a stock type 1 engine. Of course holding a type 1
engine at 5k for power readings with a stock crank will pound out the
center main due to crank flex. I've done this on the dyno and the
engine's life was measured in hours!
The dyno testing I've done of bolt on power mods (carbs,exhaust aqnd
ratio rockers) on stock engines increase midrange and top end starting
at 3k and they also extend the power range up into the higher RPMs. To
safely run the non stock engine where the peak power is means heavy duty
or double springs and counteweighted cranks become necessary.
I have heard from more than one van and bus owner that they need to
down shift on the highway when climbing even small hills. the engine
makes to little power below 3k they also report at the same time they do
have a non stock camshaft. Cams and bolt ons combos if not well
selected shift the power curve to the mid and top end only. The results
can be shorter engine life from the pounding the engine takes if
precautions are not taken to prevent it. Also major drivability problems
like starting off while having to ride the hell out of the clutch and
getting a burst of power at mid RPM range.
I can back these points up with dynos sheets and will at a later date.
Bob Donalds
from Boston where its snowing to beat the band as I write this
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