TOKYO -- For all its silence, Toyota’s Mirai hydrogen fuel cell vehicle can actually be pretty noisy.
Ironically, that is because the car is propelled by a whispering electric motor and not a rumbling gasoline engine. That allows the driver to pick up sounds that might otherwise be droned out.
The sounds -- a distinct whirring and intermittent clicking -- are unique to the Mirai’s hydrogen drivetrain. They came through loud and clear during a recent test drive in Yokohama.
The whirring kicks in when the driver punches the pedal for quick acceleration. It is reminiscent of the motor-assist in the Prius hybrid. But in the Mirai, it is actually the hydrogen pump working overtime to flush more hydrogen through the processing stack to ramp the car up to speed.
The clicking, which can grate like a noise-vibration issue, comes from the hydrogen fuel injector, which feeds the fuel from the high-pressure hydrogen tanks into the pump.
The clicking speeds and slows in time with your foot on the accelerator.
Both sounds emanate from just under the rear floorboards where the mechanisms are housed. Engineers said they are working on ways to better muffle the sounds.
Then of course, there is the futuristic “Jetsons” hum Toyota deploys in all electrified vehicles. It’s an artificial sound meant to warn people when the car is approaching in quiet electric-only mode.
Those are just some of the quirks associated the new alternative-energy nameplate, which went on sale in Japan in December and hits U.S. lots in September. Toyota Motor Corp. is positioning hydrogen technology as its long-term solution to sustainable, clean-energy transportation.
Another curiosity is that Japan doesn’t allow self-serve hydrogen fueling. Instead, only licensed station attendants are permitted to hook up the nozzles and hit the “refuel” button.
The procedure requires two attendants. One is outside working the hose. That person then uses a walkie-talkie to communicate with another inside the station at a control panel. The second monitors all the pressure gauges and leak meters before radioing back with a final OK.
And the licensing is no joke.
At a Mirai refueling demo here, attendant Yukihiko Hasegawa said the pass rate for the pumping exam he took year was only 18 percent. Only about one car a day comes to his station, where hydrogen costs 1,000 yen ($8.39) per kilogram. That’s enough to power the car for about 100 kilometers (63 miles.)
Hydrogen leaks, he said, are the No. 1 concern: “It’s very dangerous.”
