The reason I chose
replacement type air-filter instead of cone filter is that I
wanted to keep the low-end torque for autocrossing. In the
meantime, I wanted more intake sound. So I removed the filter box
and the short intake tract (plus integrated resonance chamber No.
1). That means I had to fabricate some support for the air filter
sticking with the air box lid and air-flow meter. The main
problem was that hot air would be sucked in from above the
exhaust header if the factory intake tract with resonance chamber
No.1 (which directed air from outside the engine compartment)
were removed. My solution was to turn the filter assembly
(air-flow meter, air box lid plus air filter) around such that
the air filter is facing a bit away from the exhaust header. But
that was not enough. I used pieces of aluminum sheets and
alumimum foil to create a heat shield for not only heat from the
exhaust header but also for the heat from the radiator fan. The
result was amazing. With the headlight up, the air-flow meter
metal housing could be stone cold after a couple hour drive in
hot summer while the engine valve cover was still too hot to
touch.
If you like how a cold air
induction system (CAI) prevents your Miata engine from getting
weak after a long drive, my heat shield customization offers even
more -- a cold air-flow meter. Some (or all?) CAI has the
air-flow meter relocated just behind the radiator, making the
meter very hot. The problem is that the metal air-flow meter
housing makes an "efficient" heat exchanger to conduct
hot air from the radiator to the intake air through the hot
metal. Another problem with hot air-flow meter is that the
air-temperature sensor is located inside the air-flow meter and
can be affected by the hot metal meter housing.
The reason I chose
replacement type air-filter instead of cone filter is that I
wanted to keep the low-end torque for autocrossing. In the
meantime, I wanted more intake sound. So I removed the filter box
and the short intake tract (plus integrated resonance chamber No.
1). That means I had to fabricate some support for the air filter
sticking with the air box lid and air-flow meter. The main
problem was that hot air would be sucked in from above the
exhaust header if the factory intake tract with resonance chamber
No.1 (which directed air from outside the engine compartment)
were removed. My solution was to turn the filter assembly
(air-flow meter, air box lid plus air filter) around such that
the air filter is facing a bit away from the exhaust header. But
that was not enough. I used pieces of aluminum sheets and
alumimum foil to create a heat shield for not only heat from the
exhaust header but also for the heat from the radiator fan. The
result was amazing. With the headlight up, the air-flow meter
metal housing could be stone cold after a couple hour drive in
hot summer while the engine valve cover was still too hot to
touch. 
My Previous Car