The easiest way to produce more power is to open up the exhaust system.  This is so important that it warrants to repeat it!

The easiest way to produce more power is to open up the exhaust system.

By freeing up the exhaust, the engine and turbo "breathe" better.  The turbo is able to spin more efficiently and quickly!  Typically, higher boost levels are attained.

A downside to a quicker spooling turbo, the 1986-1988 FC3S stock turbo wastegate control system cannot control exhaust gases quick enough.  This translates to boost creep!  The 1989-1991 FC3S minimize this problem due to the better "double-flapper" wastegate.

Stock, single wastegate hole from 1986-1988 turbo FC3S
Stock, double wastegate holes from 1989-1991 turbo FC3S

Boost creep (or boost spiking) is when the turbo spins uncontrollably, which eventually causes higher than normal boost levels.

To combat boost creep, there are two options:
1) Porting the stock wastegate orifice
By porting the 1986-1988 FC3S wastegate orifice, this gives more control to the wastegate; the enlarged orifice lets more exhaust gas be diverted by the wastegate so uncontrolled boost creep is minimized.  This can be done by most owners with a grinding tool and basic hand tools.

Before/after comparison of porting wastegate

2) Clipping the exhaust turbine wheel
By cutting a portion of the exhaust wheel, this drops the efficiency of the wheel itself.  By reducing efficiency of the turbo, this prevents the turbo from spinning uncontrollably.  To have this mod done safely and effectively, we recommend contacting a qualified turbo shop to do this work.

There are several good aftermarket exhaust systems available for the FC3S out on the market.  Two most notable systems are the Racing Beat 3" full turbo exhaust system for US$789, and the MindTrain 2.5" exhaust systems, which come in fully emissions-legal variations with catalytic convertors to full-race versions with no cats.  Price for the MindTrain exhaust systems come close to US$2,000!  Other than that, there are tons of "cat-back" exhaust systems that are emissions-legal, since they keep the stock catalytic systems intact - our advice is to find another FC3S owner who has a cat-back exhaust system you're potentially thinking of purchasing and see if you like the looks and exhaust note!  Stick with quality, name-brand vendors when looking for a potential exhaust system.

One last note:  by upgrading the exhaust (especially when eliminating or modifying the stock catalytic converters), it highly likely you'll run into "fuel-cut" due to elevated boost levels.  Running boost ~1psi higher than stock (1986-1988 FC3S run ~5.5psi stock and 1989-1991 FC3S run ~7.5psi stock), will cause the ECU to abruptly kill the fuel pump.  Please avoid running into the overboost fuel-cut!

To avoid fuel-cut, you can use a Fuel Cut Defensor (FCD) available from Racing Beat or Mazdatrix.  The FCD is safe for those running boost levels up to 12psi.  If you're planning to run more than 12psi of boost or wanting a must better solution, you can go with a reprogrammed ECU; we recommend going with a G-Force reprogrammed unit due to our experiences; reprogrammed ECU's eliminate the programmed fuel-cut by alternating the software code - an added benefit is the new maps to optimize the ECU for your mods!  Reprogrammed ECU's go for anywhere from US$300 to US$600, depending on vendor and 1986-1988 models versus 1989-1991 models.

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