Date: Thu, 20 Sep 2001 19:58:25 -0700
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: Digifant II 'Diesel' Conversion Pics
In-Reply-To: <B7CF5A7E.877F%albell@uvic.ca>
Content-Type: text/plain; charset="US-ASCII"
See ####
-----Original Message-----
From: Alistair Bell [mailto:albell@uvic.ca]
Sent: September 20, 2001 2:22 AM
To: vanagon@volkswagen.org; vanagon@gerry.vanagon.com
Subject: Re: Digifant II 'Diesel' Conversion Pics
on 20/9/01 3:48 AM, David Marshall at vanagon@volkswagen.org wrote:
>>>> I made some remarks on air intake noise....<<<<
>
> #### This is addressing noise and not the vibration problem.
>
David,
the noise and the vibration problem are somewhat linked. A lot of the
vibrations at certain rpms come from ,IMO, resonances in the exhaust system
as well as inherent resonant frequencies in the engine itself. To a much,
much lesser extent, noise in the intake system will contribute to the
"perceived" vibration problem (if not contributing much in actual
vibration).
#### Yes, the vibrations are a result of all of these factors.
Don't get me wrong, I like the roar (and the other advantages) of the
unshrouded K&N filter, but it does add to the overall noise and may well
resonate at frequencies that coincide with that particular engines "buzz
point".
#### It's a world of compromises!
Its an interesting idea to change the characteristics of the rubber engine
mounting blocks to reduce or eliminate the vibrations (don't forget the
trans. mount), but as the I4 install exhaust system is suspended from the
engine, not the body, for its entire length, any vibrations/resonances
produced there will be tranferred to the engine. Reducing the noise of the
exhaust, will reduce the amount of buzzing experienced by the driver.
Some have compalined of buzzing at around 4K rpm, others at around 3200. I
think the difference is due to the type of exhaust each is using.
#### Some of my customers have complained about some vibration, I ask them
to put their foot on the tail pipe and see if the vibration is still there -
every time it goes away. I can't stress that you have to make the exhaust
system as tight and as ridged as possible so it moves with the engine. I
recommend a piece of 1/8" plate metal on the location where the A2 rear
motor mount goes (same place as the Diesel mount) and from that plate weld a
1x2" bar to it that you would secure you exhaust to just before the muffler
or in some cases where people use longer muffler, on to the muffler. The
passenger side is much the same way where we use some conduit and flatten
one end of it and mount it to the same location as the rubber motor mount
the other end goes to as close as the end of the muffler to make a
triangle - no more vibrating exhaust! The neat thing about the 15 degree
kit, is even though the exhaust system in some cases may vibrate as it
wasn't built correctly - the driver never feels the vibrations, just hears
the vibrations. The Audi mounts that we use work very well and I think the
angle of the engine also has something to do with it.
Alistair
albell@uvic.ca
'82 Westy, diesel=>I4 gas
David Marshall
Fast Forward Automotive Inc.
4356 Quesnel Hixon Road
Quesnel BC Canada V2J 6Z3
mailto:info@fastforward.ca <mailto:info@fastforward.ca>
http://www.fastforward.ca <http://www.fastforward.ca>
Phone: (250) 992 7775 FAX: (250) 992 1160
. Vanagon Accessories and Engine Conversions
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