Bob,
I was talking in general. It could well be that the original AH dampers
were straight through design glass fibre filled as they are very narrow.
Mild steel pipes do last well, it is the boxes that do not last in
systems without catalyst as acid condensation gathers in the bottom and
rots the box out from the inside. Here in Europe it was not uncommon
that one had to replace the rear box of a car every two years, and if
you had a French or Italian car it could be every year, especially if
you did short runs only.
The thickness of the material will most certainly play a role in the
acoustics. Mild steel systems would be thicker to create an acceptable
durability.
Kees Oudesluijs
Op 15-2-2013 14:05, Bob Spidell schreef:
> Aka 'turbo' (reflective) and 'glasspack' (ceramic fiber) in the
> States. I had a mild steel Ansa which is a glasspack design and I
> don't recall it ever sounding tinny, and the steel was in perfect
> shape long after the fiberglass packing was shot. I'm still using the
> pipes in my current, cobbled together system (Frankenmuffler). The
> Ansa steel was quite thick (16ga maybe), and the Falcon SS seemed thin
> to me--maybe it's a question of steel thickness.
>
> Kees, do you know for certain whether original Healey mufflers (forget
> the brand name) were turbo/reflective type? They're shaped like
> glasspacks.
>
> Bob
>
>
> On 2/14/2013 10:36 PM, Oudesluys wrote:
>> There is a difference in working principal involved here. The
>> original type mild steel exhaust dampers are usually of the
>> reflective type, the exhaust gasses pass through a series of chambers
>> of a predetermined size. These chambers are separated by barriers
>> that are perforated or fitted with one or more tubes of varying
>> diameter etc to enlarge the path the gasses have to go and to absorb
>> certain frequencies. It is a fairly complicated matter. They can be
>> rather restrictive.
>> Stainless Steel systems are usually straight through systems with
>> much less restriction. The noise absorption is effected by ceramic
>> wool or stainless steel wool with which the damper is filled that
>> fits over the perforated exhaust pipe. Initially this gives a rather
>> harsh sound but after a while the ceramic or ss wool gets coated with
>> soot and partially gets blown out which will dull the sound but
>> increases the sound level.
>> In general the reflective systems do a better job damping the noise
>> but offer less performance.
>> There are also systems that are a combination of the two.
>> There are some stainless steel exhaust systems that are of the
>> reflective type and made with the same gauge material. These sounds
>> the same as the original mild steel exhausts.
>> Sound is not a question of stainless or mild steel, it is a question
>> of construction.
>> As classic/vintage/antique not catalyst cars are only little used in
>> general stainless steel is mostly used to prevent having to renew the
>> exhaust system frequently because of rust from the inside out. The
>> manufacturers design their ss systems with a certain sound in mind.
>> Usually loud and dark.
>> If mild steel is used in combination with ceramic or (stainless)
>> steel wool this will often cause rapid serious corrosion as non
>> catalyst exhaust gasses produce acids together with condensation,
>> especially on short runs where the exhaust has not been fully warmed
>> up. The wool will absorb the moisture.
>>
>> Kees Oudesluijs
>> NL
>>
>>
>
>
--
Kees Oudesluijs
Dorpsstraat 183
2995XG Heerjansdam
T: 078-677 1233
E: coudesluijs@chello.nl
Technische commissie Jensen Healey en GT
Het Jensen Genootschap Holland
www.jensenholland.nl
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