Exhaust Packing and Wrapping
What's the difference between E-Glass and Basalt?
Exhaust Packing - How it works and Types
The packing in an exhaust is used to absorb the sound waves. A silencer is just a big box filled with a packing. The energy in the sound waves excites the fibres of the exhaust packing and the energy is dissipated. A result of this is that the fibres are broken up and are blown out with the exhaust gasses.
This is the reason that the effectiveness of a silencer reduces with use as the volume of packing is blown out.
It also illustrates why the packing should not be rammed hard into the exhaust box. If the packing is solid round the central perforated tube the sound waves cannot penetrate deep into the packing and the silencer does not reduce the sound level.
There is unfortunately no way of predicting the size of silencer that a particular car/engine combination will need. The only rule of thumb is that volume matters and therefore increases in diameter often give better results than increases in length.
There are two types of packing E Glass (white) and Basalt (brown).
The basalt can withstand a higher temperature than the E glass but blows out at a much faster rate. The life of the basalt can be extended if the perforated tube is first wrapped with stainless steel wire wool.
The E glass is more often used. The change to basalt is only necessary if the E glass has reached such a high temperature that it appears a small molten globules of glass.
Any tips on how to use Exhaust Wrapping?
Guide to wrapping your Exhaust by George Astell, Merlin Motorsport
Using exhaust wrap can increase the performance of your engine. Wrapping the headers of your exhaust system will effectively prevent your exhaust tubes from cooling down, therefore keeping the exhaust gases of your engine at a high temperature. Maintaining the exhaust gases at higher temperatures increases performance on several levels. For example, when traveling at higher speeds the gases will increase the scavenging effect and improve the performance of the intake and exhaust systems as a whole. The exhaust gases are therefore removed faster from your exhaust system when hot. Exhaust wrapping also expels the hot exhaust gases more quickly due to decreased density, leaving room for purer, cooler air in and around the combustion chamber. This will increase the quality of the air-fuel mixture and thus improve the engine performance.
To help with fitting exhaust wrap, you can moisten the wrap to make it more pliable (do not soak the material). Once moistened, wrap the material around selected pipe and secure in place, ideally with a stainless steel tie. Then tightly wrap the rest of the pipe, overlapping by approximately 1/4 inch (6mm) each time. Then fasten at the other end with another tie. More ties can be added to help secure in place if required. As a rough guide, 2 inch (51mm) diameter pipe will use approximately 47 inches (1200mm) of 2 inch wide wrap per foot (300mm) of pipe. Likewise, 3 inch diameter pipe will use around 59 inches (1500mm) of 2 inch wide wrap per foot of pipe.
As an extra option to finish off a clean and well-protected Exhaust Insulating Wrap application it is recommended to use the Hi-Heat Coating. The coating will protect the wrap from abrasion and harmful liquid spills. Extra resins and binders toughen the surface, extend the life of wrap by protecting it from friction, and seal the pores to minimize the penetration of harmful liquids. Using the heat coating is not essential but can prolong the life of the wrap.
Once fitted, allow the wrap to dry then start the engine in a well ventilated area. This will then let the exhaust wrap material cure. Some smoke may appear at this point. This should last no longer than 10-15 minutes. Smoke should not appear again once the wrap has fully cured.