It is not only in Europe that the noise-free laws have been “tightening”. In the US state of California these caused the Porsche 911 GT3 with manual box cannot be sold there.
The decision affects the 911 GT3 and 911 GT3 Touring and is due to the fact that the manual gearbox variant of the German sports car does not meet the SAE J1470 noise measurement standard. In other words… it's too “noisy”.
Created in 1992, this test was born in an era when most cars had gearboxes with only five or even four ratios. The most curious thing is that there is already another test (the J2805), created in 2020, that the 911 GT3 with manual gearbox can pass, however, this new test has not yet been implemented in California.
How does the test work?
Although the document that regulates it is extremely detailed, the SAE J1470 test can be summarized in a very simple way: the model to be approved must pass (in acceleration) next to a microphone that will record the level of noise it emits in decibels (dB).
The purpose of this test is to measure “the highest noise level compatible with urban driving”. Test methods vary depending on the type of vehicle, its mass, power and box type.
Generally, the test involves accelerating at full speed from 50 km/h until the engine reaches its maximum rpm. In the case of models with manual transmission, the test is done in second or third gear, and in the case of the 911 GT3 it is done in third.
The PDK box passes and the manual doesn't, why?
While in the case of models with manual transmission the acceleration has to be done at full, in third, until reaching the redline, in the case of models with automatic transmission, although the recommendation to accelerate fully is the same, it cannot, however, make the box reduce a ratio.
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Accelerating at full speed on the 911 GT3 with the PDK gearbox could cause several reductions (at first it is capable of reaching practically 80 km/h), so it never performs the test with full throttle and thus passes it without difficulty, until because the test ends before the engine reaches full revs, precisely the point that causes the manual 911 GT3 to “fail”.
As for the Californians who had already ordered the Porsche 911 GT3 with manual gearbox, Porsche said they will be contacted by the respective dealers so that the situation can be explained to them and so that they can, if they want to do so, opt for the variant with PDK gearbox.