Lynn,

Does having a turbo make any difference to the ability of certain packing materials to survive?

Dave's experience would seem to prove not. 

 

My new turbo has a 3 inch outlet. What if I inserted a 2 inch outlet pipe as shown in the attached?

How many / how big on the holes? Sounds like a lot of drilling. :(

Can the perforated pipe be bought?

Regards,

John

The perforated material is just stainless sheet stock. It is rolled into tubes and welded to form the inner tube of the muffler. You can see through the length of the muffler.

 

The high pressure pulse then partially leaks into the void between the outer diameter of the perf tube and the muffler shell. It then leaks back through the perf tube as the high pressure wave passes. The swarf filler just slows the induction on the up side, and slows the escape on the downside.

 

So, the muffler trims the top (As seen on a scope) of the pulse, and that loss of energy drops the velocity below supersonic at the outlet. Like an accumulator for exhaust gasses.

 

The carbon steel version of perf stock is available at Sears. OK for experimenting, but it won't last long. Any metals supply house will have a selection of the perf material, in a number of hole sizes and spacings.

 

The NA housings have a stainless wedge cast into the exhaust liner to shape part of the pulse into a lower velocity, and that too reduces the amount of energy in the pulse. So, that a less complex muffler can be used. In all cases the total flow is still based on displacement X RPM, but the highest pressures are spread out in time to reduce the peak pressure.

 

The turbo housings have no such wedge, because the turbine wheel mechanically removes so much energy that the flow leaves the hot side housing as subsonic flow, and much less complex muffling can be used. So I think the stuffing would do much better behind a turbo.

 

AT 6,500 RPM, I suspect that an inner tube size as small as 2 1/2" would be big enough.

 

My 4" ID perf tube muffler is good up to 9,600 + RPM. We don't use RPM that low (6,500) so I have no readings for that area.

 

Lynn E. Hanover