Accelerator stuck wide open while car is going fast: what should you do?

[NY]

The footbrake will also (hopefully!) cancel cruise control. Being cynical, that is one cause of supposedly "stuck throttle" :-)

[boltar]

Something that occurs to me is that being AC alternators will need an inverter to crank them whereas a starter motor is DC and just needs a circuit to the battery. I wonder if inverter limitations are what prevents it being used all the time on non hybrid cars?

[NY]

Ah I didn't realise the Auris uses the alternator to start the car from cold. I presume if the fan belt breaks you are utterly buggered because you can't restart the engine (if it's stopped) to be able to drive (with the engine using on battery rather than alternator power for its spark) to a safe place to wait for Mr RAC or Ms AA to tow you to a garage.

[TMS320]

That is why you would press ~hard~ and sustain.

Normally the brakes only disperse kinetic and potential energy which are inherently limited so it usually doesn't matter how you load them. Against the engine, cautious braking allows the engine to keep the energy topped up. Also, if your delay allows the speed to rise you've created a bigger problem than you had to start with.

[Tim Streater]

It doesn't have a traditional alternator.

You could look here for more details:

according to which:

The HSD system replaces the geared transmission, alternator, and starter motor with:

? MG1, an AC motor-generator having a permanent magnet rotor, used as a motor when starting the ICE and as a generator (alternator) when charging the high voltage battery

? MG2, an AC motor-generator, also having a permanent magnet rotor, used as the primary drive motor and as a generator (alternator), which regeneration power is directed to the high voltage battery

[NY]

Ah so the "alternator" and "starter motor" functions are combined with the motor for actually driving the car. So there's a mechanical connection between it and the engine (as for a conventional starter motor) so no need for belt drive. I can't work out from the Wikipedia article: is it effectively built into the flywheel?

My parents have a hybrid Auris and they are very pleased with it. I noticed that like a lot of cars with CVT (*), the engine runs *very* fast (a lot faster than the most efficient speed of 1500 to 2000 rpm that the article mentions) and for a lot longer than a driver of a manual car would choose to do, or a conventional auto would except in kickdown mode, before "changing up". I suppose it knows what it's doing...

(*) The old Dafs and the Volvo 343.

[Andy Burns]

Neighbour had a "normal" prius, now has a prius PHEV, probably works well for them, lot so short local journeys, so generally plugged-in and recharged rather than filling the tank.

They don't have Otto cycle engine, instead Atkinson cycle engine, which is more efficient though less powerful.

[Dave Plowman (News)]

Usually caused by wind up in the suspension, so nothing really to do with the handbrake as such. If you had pure wishbone suspension with the wishbones at right angles, it wouldn't happen. But most are usually angled to a semi trailing design. To prevent plunge etc when braking.

[NY]

So the Auris doesn't actually have a conventional (Otto) petrol engine. Never knew that. I'll have to Google what the differences are.

[Dave Plowman (News)]

It's an interesting one. Like most hybrids, the IC engine does all the work when at speed on a long journey. And an Atkinson cycle type is best at a constant speed. Efficiency takes a dive outside this. Very noticeable on early Prius which were very heavy on fuel when cruised at speed.

[NY]

I was surprised at how little battery storage the Auris has (and this may be true of other hybrids too), so it only uses the motor for a small amount of the duty cycle - maybe a little bit more for lower speeds that you'd find in town, so it would keep the towns cleaner at the expense of more pollution in the countryside or on longer, faster journeys when the IUC engine also charges the battery.

It sounds a good idea: design an engine that is as efficient as possible at one speed, and then develop transmission that tries to maintain this engine speed for a wide range of road speeds.

Are there any hybrids which are purely IC-electric (like diesel-electric trains) where there is no mechanical connection between IC and wheels, just a generator and electric motors. This would allow all the smoothness of acceleration that you get with an electric motor, because the ratio between motor and wheels is fixed (maybe 1:1), so there are no losses in a fluid flywheel or in the belts of a CVT. On the other hand, petrol-electric-kinetic is more energy conversions so there may be extra losses in that.

At first, I assumed that a petrol/diesel-electric hybrid was like this: no mechanical connection, only an electric one.

[boltar]

Chrevrolet Volt IIRC.

[Dave Plowman (News)]

But it's not just engine speed but the load on it. At the end of the day you need enough 'power' from the combination of IC and electric unit to maintain its maximum cruising speed. With likely quite a bit in reserve to climb hills without slowing down considerably.

It's why hybrids tend to give good MPG figures when driven gently. But often worse than a conventional vehicle when driven fast.

[dennis]

Its worse than that on a smart car.. the same belt drives the water pump. You may start the car and have the belt break and you will only get down the road before you have to turn the engine off to stop it overheating. Then you can't restart it.

[Thomas Prufer]

Reminded me, there's something called the "Power Braking Test" or "Stall Speed Test": Rev up on full throttle against a full brake (only works on an automatic), note steady-state rpm. Stop after a few seconds lest the torque converter overheats.

This puts all the mechanical energy output in the torque converter -- another place to dump the energy when braking a fast-moving car with engine on full throttle.

Thomas Prufer

[dennis]

8<

I think Vauxhall did one but they don't sell them any more.

[TMS320]

The context you snipped was about losing eps.

It's not natural for the engine to disobey your foot.

[Dave Plowman (News)]

The TC itself limits the speed the engine can get to. And usually well below the full engine torque.

I've lost you there.

[NY]

I think a lot of cars that had the fan driven by the belt also had the water pump driven by belt. I seem to remember one of my dad's cars which had two belts driven from different pulleys on the engine: one for fan and the other for alternator and water pump; or maybe I'm imagining that.

[Rob Morley]

I wonder how much ABS conspires against stopping the engine with the brakes.