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Why the Stick-Shift Porsche 911 GT3 fails California noise test



Porsche unveiled the 2022 911 GT3 Touring this week – a more comfortable and subtle version of the razor-sharp new GT3 introduced earlier this year. Buried at the bottom of Porsche’s press release was a grim, disappointing admission: “The seven-speed PDK gearbox will be the only transmission offered in California with the 911 GT3.” That’s right: The six-speed manual, a free option that seems ideal in the raw, visceral, naturally absorbed GT3, can not be sold in California, the state where you expect to see the largest number of this sports car sold.

It all comes down to noise. According to a spokesman for Porsche, the GT3 passes California̵

7;s driving noise test when equipped with PDK’s seven-speed dual-clutch automatic; with the six-speed stick it fails. It is a factor in how the test is performed – and which test method California chooses to use.

The California Code of Regulations specifies that highway vehicles must pass a drive-by noise test designed by the Society of Automotive Engineers – specifically SAE J1470, “Measurement of Noise Emitted by Accelerating Highway Vehicles.” This SAE paper goes into extreme detail explaining the design and layout of the ideal test environment, the correct arrangement of the measuring equipment, the exact condition of the vehicle to be tested, and over and over again. But basically, the test boils down to this: A vehicle accelerates past a microphone, and the sound pressure level in decibels is recorded.

SAE J1470 aims to measure “the highest noise level in accordance with urban driving.” The exact test method varies depending on the vehicle size, power, peak acceleration speed and gearing, but generally involves full throttle driving starting at 50 km / h and continuing until the engine reaches its peak power speed Manual transmission vehicles are tested in either second or third gear; given the GT3’s curb weight and power, the procedure requires third.

Here’s the thing: Automatic transmission vehicles are not necessarily tested at wide open throttle. The method specified in J1470 states that “the throttle lever must be opened as fully as possible to ensure maximum acceleration without operating start“(highlight added) and held in this position until the car reaches the end of the test area.” Kickdown, “as defined by SAE,” means a forced shift to the lowest possible gear (first or low gear). “

You see the problem here. The PDK-equipped GT3 can handle almost 80 km / h first. Determining that flooring the accelerator in an automatic GT3 would trigger a multi-gear shifting right up to the first. So while the procedure requires the manual GT3 to run full throttle almost to redirect in third, the same procedure prohibits full throttle acceleration in the automatic version of the same car. Therefore, the PDK test passes while the manual fails.

A Porsche spokesman would not answer specific questions about how the manual or automatic GT3 worked in California’s noise test. But the Porsche representative highlighted something remarkable: the SAE J1470 is no longer the most up-to-date test method when it comes to measuring drive-by noise.

See, SAE J1470 was first published in late 1984. The paper reveals that it is relatively outdated when it comes to vehicle technology: the standard test procedure assumes that the typical stick-shift vehicle is “equipped with a manually operated gearbox with no more than four forward gear ratios.” There are alternative test parameters for vehicles with highfalutin gearboxes with more than four forward-looking ratios, and SAE has been publishing updated versions of the test method since 1984. But the basic framework of the J1470 seems insufficient to test modern vehicles by 2021.

The Society of Automotive Engineers addressed this with a brand new vehicle standard: the SAE J2805, published in 2008 and updated as late as May 2020. The J2805 completely updates the driving test procedure. Instead of driving past full throttle (or near full throttle), the J2805 includes a hugely complex method of calculating the appropriate acceleration speed for each vehicle being tested. As the first paragraph of J2805 states, this updated procedure is “based on comprehensive statistical surveys of vehicle traffic in real traffic.” The J2805 includes techniques suitable for hybrid cars and other advanced powertrain designs that did not exist when the J1470 method was published. Long story short, the J2805 more accurately simulates “acceleration by partial throttle control in urban traffic.”

Here’s the problem: California does not use the J2805. Vehicle noise testing is performed by the California Highway Patrol, as defined in the California Code of Regulations, Section 13, Section 1046. This Regulation specifies SAE J1470 as the official testing procedure. So while Porsche presumably designed the GT3 to pass the updated J2805 test with both transmissions available, in California, the old method is still the law of the land. (Porsche’s spokesman stated that CHP has planned to update its test rules to incorporate the new SAE procedure; Road & Track reached out to the CHP for comment but did not receive a response at the time of publication.)

So for now, Porsche can not sell you a 502 horsepower 911 GT3 with a six-speed manual in California – despite the fact that the PDK-equipped GT3 has the same engine, the same exact exhaust system and as far as we can tell, gives the same amount of noise.

“We do not know when the new SAE J2805 procedure will be adopted by California, therefore we can not guarantee the sale of the manual transmission on the 911 GT3 – and where there is doubt, we are always cautious,” said Porsche spokesman Road & Track via e-mail.

Our contact at Porsche was eager to point out that the issue of noise control does not affect any other 911 variant nor does it apply to the 718 Boxster or Cayman. So if you want a brand new Porsche sports car with manual transmission and you want to put a Californian number plate on it, you have all the models available to you – except the one you really, really want.

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