Lynn,

 

I'm having a hard time visualizing the stack of 3/4" square tubing exhaust as you described.  Do you have any pictures? 

 

Mark

 

Here you go...........

 

Fish tails like those found on motorcycles are found at the end of absorption style mufflers that remove some of the high pressure pulses. The flat side (of any pressure vessle) will fatigue fail very quickly when exposed to pulses. The round muffler (pressure vessle) is ideal from the strength to weight and fatigue failure stand point.

 

Like a large piston in a hydraulic system, a small amount of pressure produces a huge mechanical advantage over the piston or a flat or nearly flat section of a muffler, or the flat sides of a fish tail.

 

So if it's flat it dies. Or even nearly flat. The further from round the shorter the life. You can extend life span in a flat section by bracing it so it cannot move. Movement (bending) is required for a fatigue failure, so no movement generally yields no failure.

 

 

In the case of the CART piece it is after the turbocharger, so most of the pulses are already removed, and the square tubes provide extensive cross bracing to prevent movement. In any case the whole exhaust system is discarded after three heat cycles including the waste gate exhaust piece. Just to avoid a failure during a race. One reason why there is no more CART series.

 

Lynn E. Hanover