Date: Sun, 23 Feb 2003 17:22:41 -0800
Reply-To: Alistair Bell <albell@UVIC.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <albell@UVIC.CA>
Subject: Re: vanagon with ticco engine/vibrations
In-Reply-To: <004e01c2db99$1142b9a0$0b3b67ce@MCNOCK>
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This droning thing is something that may be a result of a few little things
rather than one single solution.
Some people claim no annoying resonances, some are driven mad by them.
here's my experience with '82 diesel Westy, converted to 1.8 Digifant 8v.
(have 2 vans to compare, the other being my friend Stephen's van))
I kept the stock diesel manifold and exhaust system when I had the swap done
back in '94. I wanted to keep some money for other things :) I also was
planning to swap tranny or at least put in different R&P, when funds came
available.
Well, as often happens I never did change the trans nor the exhaust (until
now).
I didn't notice any annoying resonances for the first couple of years, then
a buzz developed. I found 2 of the rubber exhaust mounts to be broken.
Replaced and the van was fine.
Latterly though, the van has been getting louder and buzzier, the internal
baffles of my diesel muffler had finally left the can. I do get a real buzz
around 3500 rpm.
So there may be an inherent resonance problem with the 1.8 litre I4 in the
Vanagon engine carrier. A good muffler reduces this buzz a lot, but the
muffler has to be hung correctly, and in my opinion, copying the stock
diesel set-up is the way to go (quite stiff rubber mounts, 3, 2 at the
proximal end, 1 at distal end of muffler.).
Stephen's experience has been different. He swapped in an air-cooled tranny
and had a different exh system. I have never noticed a buzz with his van.
But he has gone through more a couple of mufflers and connectors. He made
the mistake (remember the early '90's were relatively early days in the swap
world) of hanging the muffler by flexible rubber doughnuts.
But through it all his van was smooth, in fact I think it felt a lot
smoother than mine, even at idle. I can only guess it was the exh and
muffler.
I hope, and, (arrogantly I suppose), expect my new exh system to result in a
smoother and quieter van.
If I do get resonances, I will look to these things (in order of ease, not
necessarily in order of importance):
1. experimenting with differing stiffness cross member. that metal piece
that spans between the 2 tubular carriers in the pre-83.5 diesels, the ones
with the bushings on the end of said tubular carriers. I swapped in a length
of AL angle for the stock flat bar last summer and I felt (Frank G.
correctly encouraged me to do more measurements on this) that it shifted the
rpms of resonance. Remember, my muffler was basically shot then.
(cutting up lengths of AL channel/box is something I can do *S*)
2. Acoustically isolate intake filter. One time SA list member had a
complaint of annoying resonances in his SA I4 project. He asked SA VW
engineers, they pointed him to the air box. I really should try and find
that bit of archived email.
3. Adapting another mount. I will take Frank's advice and look to hyd.
mount.
One last thing. Last summer on our holiday, while driving across the
seemingly endless prairie of Alberta, I had the chance to move around the
van while my wife drove. The van was packed to the gills and all that gear
and clothing must have muffled much of the noise. But...The funny thing I
noticed was that the noise was less in the back seat than it was in the
driver's seat. Why would that be? I am closer to the putative sound source
when I am in the back. My conjecture is that the sounds/vibrations have a
conduit in the gear shift/linkage, and they have a sound box in the plastic
heater duct that runs between the front seats of my van. I have used sound
deadening mats on all of my van's walls and lots on the floor and under that
plastic duct, but...it sure sound louder in the front than in the rear. Some
more work needs to be done...could it be that the pop top acts as sound
board too?
I hope this helps.
Alistair
--
'82 Westy -> diesel converted to gas in '94
albell@uvic.ca
http://members.shaw.ca/albell
