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Exhaust Systems

We have a particular component here which divides the tuning fraternity down the middle… some people believe a drain pipe exhaust system (3.5-4.5”) is the way to power nirvana, where as there is a camp that believes in a well made average size (2.5-3.0”) with flowing mandrel bends will be of more benefit… we tend to sit in that camp for a couple of reasons.

  1. The engine/turbo combination on any vehicle was never designed to run with a 4” ‘drainpipe’ exhaust with one straight through box at the back.
  2. These big exhausts often have very detrimental effect on the turbocharger, the turbo oil seal system is designed to run as a pressure differential seal and the lack of back pressure is one of the first reasons a turbocharger leaks oil (smokes at idle and on overrun). How many turbo cars do you see with 4” exhausts smoking at the traffic lights?
  3. The other important fact is that the waste gate system (on integral waste gate units) are designed to have back pressure to equalise the gas pressure before & after the turbine… this differential can be so distorted by these exhausts that the waste gate can no longer control the boost which leads to boost spikes, boost creep and the worst effect can be over speed of the turbine rotor which will cause premature failure of the turbo.