Tuesday, April 18, 2017

The Truth About Engine Stop Start Systems



One of the most glaring examples of this carmaker agenda self-serving design is the auto engine shutdown and restart system.

You drive along. Stop at a red light. The engine automatically shuts down. Light goes green, you start lifting off the brake, and the engine kicks back into life, as if by magic. We’re talking about that.

Systems like Mazda’s iStop - and seemingly 100 other proprietary names for similar bullshit technology. I get questions about this all the time.

So here it is: The truth about bullshit auto engine shutdown and restart systems.

Number one with a bullet: they save you bugger-all fuel. Claims that you will save any appreciable money are unmitigated bullshit. You can idle your engine all day long, and it’s still not going to cost you as much as a burger and fries. Engines just don’t consume much fuel at idle - they’re really only driving the ancillaries, overcoming their own internal friction and a bit of drag in the torque converter (if they’re driving an automatic).

The real reason these automated systems exist in many new cars is so the carmaker can legally ‘game’ the official fuel consumption tests. We’ve discussed these tests before. They’re lab tests from which the official fuel figures are derived - and these numbers are very important to carmakers, because consumption is increasingly important to buyers.

Unfortunately the tests are not very representative of actual driving. They’re just not - the official test numbers are always better than you can achieve out there, on the road, and that leads to a lot of customer dissatisfaction. Unfortunately.

The most non-representative aspect of the tests is the amount of time the cars spend stopped in both the city and highway tests. Those valleys there? The car is stopped. Together, both tests take 20 minutes - and around one-third of that time is spent stopped. In the city cycle test - it’s almost half the total time stopped.

So if you’re a carmaker, and you’re in this intense competition with all other carmakers, and you include the engine shutdown feature in the car, almost half of the official city cycle test is spent with the engine shut down. You’ll make incremental gains over a competitor without that system in his car. So, congratulations - you just gamed the system, and there’s nothing illegal about it.

But what this means for you, the car owner is: you have to wear it. And it’s unpleasant - especially on restart. Especially in a diesel, which has to battle a lot of compression when it restarts. And especially if your car has a CVT transmission. They tend to have pretty aggressive torque converters. So the restart is unrefined, at best. It’s awful.

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