hybrid engine startup

I've only ridden in a hybrid once, but from what I recall, the engine starts up very quietly and smoothly. Compare this to the conventional car startup, which is rather violent, the whole car shudders. How does the hybrid accomplish this? And why can't they make conventional cars startup just as smooth and quiet?

Reply to
Bucky
Loading thread data ...

because when you start the toyota the engine is not running it is working of the battery. a light on the dash says ready.the you put it in gear and you are ready to go. if you step down on the gas the engine starts automatily.

Reply to
Dave Dave

Just guessing: it'll be a mixture of causes. * Small engine with a special shock-absorber-thingy connecting it to the rest of the drive train. * Electric motor coupled with a good control system to even out variations in speed and load. * And, in fact, you do feel it starting and stopping, under some circumstances (although it is never anywhere near obvious, or jolting).

Maybe they will, now they know how. But a conventional engine rarely needs to be ultra-smooth when starting/stopping, because it does those jobs so rarely (commonly one of each, per journey), relative to a hybrid. Also, a decently made conventional engine can be pretty well-mannered, as-is.

Reply to
Andrew Stephenson

The only difference is in the lack of starter motor. In a conventional car, the starter motor turns the engine at a speed much less than the normal idle speed of 850rpm or higher, so there is a bit of a rumble as the engine starts turning on its own. In a hybrid the electric motor has the ability to turn the engine at the same speed at which it will be idling when the system starts the engine, so the trasition is much smoother.

Reply to
qslim

What kind of car do you usually drive? I can barely feel the startup in my cars and the noise isn't particularly loud, either. In fact, I'm not entirely sure I can FEEL the engine in my Sienna start at all.

Besides, you do need a little feedback in the form of noise, so you'll have some idea of what's happening under the hood.

*** Free account sponsored by SecureIX.com *** *** Encrypt your Internet usage with a free VPN account from
formatting link
***
Reply to
dh

COST

Actually my '05 Camry SE V6 is pretty much silent at startup; the only way to really tell that the engine's started is watching the tach. As contrasted with the '06 xB that shudders significantly at startup.

So I repeat:

COST

($25 grand for one and $15 grand for the other)

-Don (That Was Easy!)

Reply to
Don Fearn

yeah I know, I was referring to when the engine actually starts.

Reply to
Bucky

I think that's it. To expand on it, I don't think it's so much the fact that the Prius lacks a starter motor, it's the fact that the Prius in essence has a 44 hp starter motor. With such a powerful motor, it can powerfully start the engine quickly and smoothly. Of course, the reason that the Prius can have such a powerful starter motor is because it uses the same motor that drives the car.

In a conventional car, they're not going to put a 44 hp motor just for starting the car, that would be a waste of money, space, and weight. They're going to put as small of a motor as needed.

"Motor-generator... automatically starts the gasoline engine much more quickly and smoothly than a conventional starter motor."

formatting link
"the engine fires up instantly. Because it uses a much more powerful starter motor, you don't hear it spin for a second before the engine starts."
formatting link

Reply to
Bucky

Variable valve timing. At startup there's not much compression, and very little fuel is used. I'm assuming you are referring to the Prius.

Reply to
mark digital

Doesn't have anything to do woth cost, Don. 6 cylinders are by nature much smoother than 4 cylinders. This is why none of Toyotas V6s have balancer shafts - you don't need them. If you have been in a new Highlander hybrid, the engine on transition is absolutley seamless compared to the Prius, where there is a slight shudder.

Reply to
qslim

Variable valve timing isn't used at idle or at startup. It's only used at higher engine speeds when under load.

Reply to
qslim

Oh, so you are saying the engine is at full compression at startup? Bull.

Reply to
mark digital

A modern automotive engine does not have a mechanism to relieve compression like you see on small pull-start engines like on a snowblower.

If you take a look at how the variable valve timing works, you could tell that it is not designed to relieve compression at startup.

Reply to
Ray O

What you say is completely opposite what I was told by a certified Prius tech. As load increases, whether it be at low or high rpm, so does the compression. The engine is built much lighter because it doesn't have the constant compression. In idle it sips gas and the compression is very slight. Just enough to run and that's that. mark_

Reply to
mark digital

not exactly.

the variable valve timing has nothing to do with the compression.

at low engine rpm, the engine has better torque and efficiency with a 'mild' cam timing. (low valve overlap) as the rpm increases the engine can tolerate more overlap ('hotter cam') and make more horsepower. otherwise, the mild cam timing makes the engine run out of breath at higher rpms. this allows the engine the best of both worlds, good torque at low rpms and great torque at high rpms.

the shop manual explains this. if the solenoid is activated at idle, the engine stalls. the timing has too much valve overlap. this is a diagnostic procedure from the shop manual, too.

the engine in the prius is the same as the engine in the echo. i have a couple. it's a 1NZ-FE. the prius has a cover over the original starter hole, it uses the generator as the starter motor. it's silent and more responsive. sammmm

Reply to
SAMMM

Well, yours truly has also attended the Prius certification classes, and variable valve timing has nothing to do with what you're talking about. If the VVT oil control valve was activated at startup, compression would disappear and the engine would stall.

Reply to
qslim

Either the certified Prius tech needs a refresher course or you misunderstood the tech. Variable valve timing is not designed to vary or relieve compression. It is designed to allow the engine to "breathe" more efficiently at higher RPM. In an engine without variable valve timing (VVT), as engine RPM increases, the amount of time that the valve is open gets shorter and shorter so less air is drawn into the engine and the burnt gases are not expelled as efficiently. VVT helps overcome those issues.

The 4 cycles of a 4 cycle engine are intake, compression, power, and exhaust. If there is no compression, there will not be any power so the engine will not run on its own.

Reply to
Ray O

All I can say now is I eat my words. Maybe the tech tried to simplify it for me too much. mark_

Reply to
mark digital

That's how you learn. I've learned a lot from a steady diet of crow!

Reply to
Ray O

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.