<VV> How to Quiet Down my Spyder

[Shaun McGarvey]

Absolutely not. Corvair engines should be as near silent as anything out 
there, especially when at speed. Noises add up, so I'd start hunting with a 
stethoscope.

yea. Vairily ... Shaun

----- Original Message ----- 
From: "Steve Brennan" <alohaz at ca.rr.com>
To: <virtualvairs at corvair.org>
Sent: Wednesday, May 30, 2007 2:12 PM
Subject: <VV> How to Quiet Down my Spyder


Since purchasing my 1962  Spyder coupe a year or so ago, I have spent 
substantial time and money trying to get it as quiet as possible.  (My 17 
year old daughter will be driving it, and you know how picky teenage girls 
can be, even though she loves those cute little buttons on the seats.)  In 
this effort I "dynamatted" the entire passenger compartment, including the 
roof, the inner and outer skins of the doors and side panels of the rear 
seat, and put double layers behind the rear seat (adjacent to the engine 
compartment).  (With all that extra weight, there goes the gas mileage.)

While I am sure this has had some positive effect, the car is still noisy. 
Tracking the source of the noise down as best I can, I think much of it is 
entering the passenger compartment through an "passage" that runs 
unobstructed from the area covered by the rear seat side panels (i.e., where 
the rear side window mechanism is), up over the rear wheel well and then 
through a triangular shaped chamber that makes up the upper portion of the 
body between the passenger compartment and the engine compartment, and then 
around to the other rear side window area.  (I believe that the walls of 
this chamber are 1) the back wall of the "storage shelf" behind the rear 
seat (which I dynamatted and carpeted), 2) the exterior sheet metal between 
the back window and the hood, and 3) the upper portion of the front of the 
engine compartment.).  As best I can tell, this triangular chamber acts like 
a drum, collecting the noise from the engine compartment and then radiating 
it over the rear wheel wells directly into the body hollows on each side of 
the rear seat.

So, I have a few of questions.  First, does anyone know what purpose, if 
any, that the triangular chamber serves, and if there is any good reason not 
to fill it full of carpenters expanding foam (or some other sound absorbing 
material)?  There are 2 fairly large "access holes" with removable rubber 
caps inside the engine compartment that would allow such an experiment.

Second, has anyone ever tried applying the spray-on sound deadener to the 
front wall of the engine compartment and the underside of the body over the 
transaxle to create an external barrier from the drivetrain noise?  If so, 
what were the results?

Lastly, and more generally, is the air cooled engine design just inherently 
a noisy configuration?  Forget about noise when you are inside driving the 
car.  Just standing outside next to a Corvair you never have to wonder if it 
is running.  This is fine by me, cuz I like engine sounds, but others have 
asked me why it is such a noisy engine, and since all my automotive history 
is with water pumpers, I don't really have an answer.  Is it that the 
exposed cylinder "cans," as opposed to a large heavy metal block, allow more 
detonation noise to escape into the surrounding atmosphere?  In other words, 
is more noise a necessary side effect of an air cooled engine?  If so, is it 
true that Porsches, etc., are likewise "noisy" cars?

Thanks,
Steve

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