HKS adjustable cam
gears with valve cover customizationMy miata engine runs hot compared to the RWD Corolla GTS. Normally it would not be an annoying problem. Unfortunately, the factory intake tract runs right behind the radiator where the radiator fan keeps blowing hot air on the surface of the intake tract. Even worse is the intake air box located right on top of the exhaust header. An aftermarket exhaust without a heat shield will definitely heat up the intake air a lot. Compared to the RWD Corolla GTS with a 1-ft long intake tract from the throttle body to the area behind the right front headlight, the intake system on the miata definitely gets influenced by underhood temperature much more than that of the Corolla.
A series of actions to cope with the high underhood temperature include adding heat shield to separate exhaust heat from intake path, wrapping aftermarket exhaust header with heat insulation wrap, adding water-wetter for more efficient cooling, replacing factory recommended #6 spark plugs with cooler #7 plugs, etc.
The result is not significant but noticeable. When I first bought the car, it would perform like it lost 10 or more hp after an hour or so driving in the summer. That's running factory 10-degree ignition advance and 94-octane gas. I remembered one time the car was as slow as an Hyundai Excel! After the series of actions against underhood temperature, the car wouldn't feel as bad after an hour or so driving in the summer.
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gears with valve cover customization
