rev up your engines, today I'm going to talk about that modern auto stop-start
system that some cars have, where your driving down the road and when you come to a stop and
you're sitting, it turns the engine off, and then when you step on the gas it
starts back up and runs, now these auto stop and start systems are made to save
gasoline and they really started full-time in modern hybrid cars like the
Toyota Prius, now auto start-stop works great in hybrid cars, because they were
designed that way, to begin with, a hybrid car doesn't have a tiny little
starter like a normal car that runs on 12 volts, it uses the generators inside
the car to actually start the engine using a five hundred volt battery, so
it's no problem for that giant battery that's in the trunk of the Prius to
start your car up and down and up and down, it's got a lot of power, but most
cars still have these lead acid batteries they're smaller they're not
made for continually starting and stopping the car, for these kind of apps
you need a deep cycle battery, most cars still use a lead acid, they're not really
deep cycle, lithium ion like in the Prius are, but when you think about it
they're making cars cheaper and cheaper, they're not going to be putting more and
more expensive batteries in the cars just for this, and as I've already said
in hybrid cars, they use these giant motor generators to start themselves up, on a
regular car they're using these tiny little starters, they're not made to be
used over and over and over again, now granted some of these auto stop start
cars do a more robust starter, but it's nothing compared to the generators
that they use in the Priuses or any hybrid vehicle, these things are tiny
compared to those huge things, and you might not think about possible engine
damage from starting and stopping all the time, but I'm a mechanic and I think
about it, realize that your crank and your rod bearings get worn the most upon
startups, and in a normal car, they usually good for a hundred thousand starts
and stops before they start to wear out, and that's fine for a normal car that
you start up driving around then later when you shut it off you start it up, but
with these things, you're going to be starting and stopping a lot more often
so you'd need bearings that were good to 300 or 400 thousand of these cycles, so
if you have start/stop in a normal engine, hey it's going to wear the rod
bearings and the crank bearings, and then you're going to have to rebuild the engine
it's something that a lot of people aren't going to think about, but being a
mechanic, I think about that stuff and when I see damage that shouldn't occur
I'm not for that system, and then let's get down to the nitty-gritty, how much
better gas mileage do you actually with one of these Auto stop-start systems
well they advertise that they get between 3 and 10 percent better gas, much
but you're only going to get 10 percent under very limited conditions, the
temperature outside has to be moderate, between 40 and 85 degrees, higher or
lower you're not going to get much, and if you run the AC, you're generally going to
get less than 3% better gas mileage, because air conditioning uses a lot of
power, this isn't like you're turning your whole car off by turning your
ignition key off, it shuts the engine off but other systems are still operating, so
if it's hot outside after a very short period of time, it's going to have to turn
the engine back on to run the air conditioner, now like I said previously
these systems work fine in hybrids like the Prius, because the Prius's use
electronic air conditioners and they got that big old five hundred volt battery
in the back. so even when the engines not running. it can run the compressor with
that 500 volt battery and you still feel nice and cool. inside but a normal car
doesn't work that way, now truth be told, there are a whole bunch of different
auto stop start systems out there, some of them that I've seen in Europe heck
they use the alternator to start and stop the car
the alternators in those cars just spin the serpentine belt and instead of the car
driving the alternator, the alternator is spinning to make the engine go, and some
of them have electronic water pumps like BMWs, so the engine won't overheat if the
car isn't running while it's sitting there, because realized when you shut an
engine off, it's got a lot of heat in it, it's what's called heat soaking, it's
just sitting there heat soaking it actually gets hotter, so the cooling
system still has to be doing stuff even though the engine is shut off, and sure
engineers can bypass these problems with some really high-tech
technology, but really when you think about it, all this technology
that's going to break down the line and be really hard to fix, do you really want
that to get a little bit less than 3% better gas mileage if you run an air
conditioner, it doesn't intrigue me, and for many people there's just the
annoyance factor of, your driving and when you stopped on the engine shuts
itself off, now they all do have a button you can push that turns the system off
every time you start the car, if it drives you nuts, you can push that button
and turn it off, and me I find it rather annoying, every time I get a rental car
or I'm road test in a car that has that system on, first thing I do is push that
button off so it runs like a normal car, because if you want really good gas
mileage and all these technology features, heck go out and get a hybrid
like a Toyota Prius, they were designed for that, because really when you think
about it, these auto stop start systems they're kind of like a halfway measure, you
know, they work fine in the hybrid cars, but in a gasoline car, it's trying to turn
them into something that they really weren't meant for, since I'm a mechanic and
these systems have been out a little while now, they're starting to break, I
have to fix them, let me tell you they're no fun to fix, and you're not going to be
happy when you get this giant bill for fixing them right,
so if you never want to miss another one of my new car repair videos, remember to
ring that Bell!