Nissan had to reduce the exhaust noise on manual Zs, as they are not subject to the same testing procedures as automatics.
The new Nissan Z is one the most anticipated enthusiast cars. The Nissan Z is an exciting new enthusiast car. It comes in a 6-speed manual transmission or a 9-speed auto transmission. To meet strict noise regulations, Nissan had to install a quieter exhaust to the manual transmission Z.
Automakers must consider a multitude of regulations and rules when building cars. Sports cars such as the Z are more complicated because automakers must balance fun and legal obligations. The rules must be followed by even the most exciting Z, with its twin-turbo 3.0-liter V6 motor.
Before any new vehicle can be sold anywhere in the world, it must pass all noise regulations tests. California is the US’s most stringent state, meaning that every vehicle sold in America must comply with the noise regulations.
California’s test is based upon one developed by the Society of Automotive Engineers (SAE J1470). A basic test requires that a car must drive past a microphone. The vehicle must be driving at 31 mph. The vehicle should then accelerate to its maximum power RPMs at full throttle.
Problem is that manual and automated vehicles are tested differently. Manual transmission vehicles must be in 2nd or third gear to pass this test. This means that they will make a lot noise and reach redline. The text specifies that automatic vehicles must accelerate quickly and open the throttle rapidly to pass the test. This is in order to avoid triggering a forced downshift or kickdown. Instead, automatics should accelerate slowly in whatever gear they can reach 31 mph. However, the transmission should not downshift to a lower gear to keep noise levels low.
Nissan’s new Z is more loud with an automatic transmission than the manual transmission Z. This is because they have an aftermarket option that can fix their quieter exhausts.