Hypermiling the Aurion

[httttt]

Let me say first off that I do not condone unsafe driving at all...

Having driven a manual 4cy for the last 4 years I had come accustom to costing in N when the car has momentum, going down hills or coming to a slow stop only when it is safe to do so. But since having the Aurion I have just left it in D.

My question is "what are the implications to the Aurion's gear box or engine when cruising in N then tp pick up speed knocking it back to D while coasting maybe 50-60 Ks?".

[DUB]

i highly wouldn't recommend it...

[David the Viking]

BIG NO NO!!!

[¥uri]

i've thought about this also.. but imagine when you accidentally put it in Reverse

[httttt]

:o Ya, wouldnt want to knock it into reverse. But i doubt it would actually go into gear.

Anyone particular reasons?

I'm guessing it will have some sort of negative implications... (uneducated guess) The automatic gear boxes are not designed to go from N to 3 or 4 and will probably wear down the gears. ???

[WildfireATX]

Going From sports in say 2nd and high rev's into Drive brings nearly instantaneous change to say 4th or even 5th gear however the gearbox is already under torque from drive. An easy way to see what will happen shows up if when reversing out of your driveway for example u go from reverse through neutral to drive without stopping backwards momentum the aurion lurches violently and chirps front wheels and its VERY VERY bad for the torque converter, Gearbox CV's the whole drivetrain. Besides when u coast in the aurion it doesnt remain at revs anyways unless u are in sports mode.

I have simulated this situation nearly exactly when driving my mums old falcon once a while ago it is on LP Gas and has a changeover switch to go onto petrol which requires u to put the gearbox in neutral coast until the engine splutters then flick it over. I was on cruise control when i switched it into neutral which resulted in the engine revving quickly and me panicking and putting it back into drive which slammed the driveline and made even the ancient XF chirp its back wheels violently.

[Steven]

I know from experience that an Aurion will attempt to go into reverse at around 80km/h... makes a very loud bang noise too

[DJKOR]

Hypermiling the Aurion... that statement seems a bit laughable. I know I didn't buy the Aurion to get good fuel consumption. Anyone buying it for that reason as well should have a think again.

I would advised against changing between N and D while there is any momentum in the car. Just by visualising it, you can imagine the un-necessary stresses you are putting on to the transmission.

The only time I shift into neutral is when I am at the lights on relatively level ground. Not to save fuel, but so I can take my foot of the brakes and reduce the chance of putting a hot spot on my rotors. I'm still a bit over-cautious with them at the moment.

With respect to the fuel saving benefits of shifting to neutral when rolling down a hill, Hiro Protagonist has explained this pretty well. It's aimed more towards a manual, but in autos, there shouldn't be 'too' much difference:

In a modern EFI car, when you are off the throttle going down a hill in gear (ie engine braking) you are actually using NO petrol. The ECU stops the injectors from firing, and the engine stops being a driving engine and instead turns into a driven engine (this is the principle behind engine braking and regenerative braking). This is also the reason why the engine note changes significantly if you put just a tiny bit of throttle on (when completely off the throttle, it's quite loud and boomy, but squeeze the throttle slightly and it gets a lot quieter).

However, if instead of going down the hill in gear and engine braking, you put the clutch in our shift into neutral, the engine no longer has a load connected to it (or has a driving force pushing it), and will drop to idle. However, fuel must be injected at idle to keep the engine turning over, otherwise it will stall. Thus, coasting down a hill in neutral uses more fuel than going down in gear.

At the lights (once again in a manual car), it is more fuel efficient to push the clutch in as opposed to leaving the transmission in neutral. The reason behind this is if the clutch is disconnected, the only thing being driven by the engine is the engine itself, and the flywheel. If the clutch is engaged and the transmission is in neutral, then the engine is also driving the clutch/pressure plate, and the input shaft of the gearbox. This creates drag, which requires more power from the engine, which means more fuel. It's a marginal difference, but it does exist (of course, sitting at lights with your foot on the clutch gets very tiring, and it can wear out the throwout/release bearing).

Things are changed completely for an auto. The engine-braking situation should remain the same, but sitting at the lights is different, as when the transmission is in Drive but the car is stopped, you are putting a fair bit of resistance against the engine (since the torque converter/fluid coupling cannot 100% disconnect, you need to hold the brakes slightly), once again sapping power and fuel. Can't remember exactly how an auto creates neutral, pretty sure it's a locked torque converter but no clutches engaged, so there's no physical connection to the wheels (unlike Drive, which relies on brake-load and slipping the torque-converter to stay stationary)

EDIT: As an aside, because a lot of people find it hard to believe that the engine uses no petrol when engine braking, try this (only tried it in a manual, so no guarantees for an auto):

1) Get up to around 60km/h or so on a straight road (downhill helps) with no traffic, in gear

2) Take your foot completely off the throttle, listen to the sound the engine makes (this is engine braking)

3) Leaving the car in gear, and without touching the clutch, turn the ignition key to ACC

4) Listen to the car, it will sound exactly the same as when in engine-braking mode and the car turned on

If you pay a bit more attention, you'll notice that it sounds exactly like an electric air compressor, because that is exactly what it is. The sound you are hearing isn't the burning of petrol, it's the compression and release of the air in the piston. At this stage the engine is simply an air pump, powered by the inertia of the vehicle and gravity, which drives the engine through the rotation of the wheels and hence the transmission/clutch/crank. Car engines make pretty good air pumps (that's what they are in essense anyway, just powered by internal combustion), in fact Beetle engines are renowned in the Australian opal-mining industry for being used as air-compressors - one side of the boxer burns fuel like a 2-cylinder internal combustion engine, the other side (which receives no fuel or spark) acts as a 2-cylinder air pump/compressor)

I know from experience that an Aurion will attempt to go into reverse at around 80km/h... makes a very loud bang noise too

Serious? I wish the gear selector had a button you have to press before you could push it into reverse like most other autos. The design of the shifter doesn't really make it all that difficult.

I have accidentally changed it from R to D while rolling backwards at about 5km/h. I was just giving it a quick flick so I could roll back a little more and accidentally went too far. My engine stalled as a result with no rough feeling so I was glad it did that.

[Steven]

It happened when a friend was on circuit in sequential mode, and he hit it a little too hard going up a gear hence making it jump out into R.

Wasn't my car, and that car didn't seem to suffer greatly from it... however we were about 200m and it sounded like a gun going off.

[httttt]

That sounds horrible Steven. . You'd think they would put some kind of measure to stop it from happening.

Thanks for that DJ, I will take Hiro's word for it and leave it in D.

[avstral]

Once when i almost ran out of fuel around Apollo Bay during the night, i drove it about 80 km using D-N, mostly on N, speeds 60-110 km/h. No problem since then, it happend ~45Ks back.

Edited July 4, 2009 by avstral

[dave262]

That sounds horrible Steven. . You'd think they would put some kind of measure to stop it from happening.

Thanks for that DJ, I will take Hiro's word for it and leave it in D.

I had always thought there was a shift lock solenoid in place to prevent this? If it's anything like our old Honda Oddysey, it would lock the ability to change gears into P or R while the car was above 5km/h. Below this speed, you would hear a clunk as the solenoid would disengage.

Does the Aurion actually have this? Too scared to go and test it myself!

[WildfireATX]

The shift lock is mainly for maintenence so that mechanics can shift the car into neutral without having to start the car up. And thats all its for really. As for a lock out? if you driving that furiously you can accidentaqlly knock it into reverse? I think you need to settle down and think a bit before driving that furiously again.

[Guni]

Holy 5h!t darryl, too bad you don't have a corolla sportivo .... :( :(

[whitestivo]

this thread has just changed my driving style completely.

i had always thought coasting in neutral used less fuel, and now i know that i'm better to let the little stivo rev down.

totally fascinating.

does this mean that when you shift down from say 80km to 0, that every time you engage the clutch and change down a gear that the engine squirts a little bit of fuel each change? i wonder why

hiro, that was brilliant read.

whitestivo

[tekkyy]

yeah I get annoyed by the engine braking sometimes

it feels weird to go slower and slower while going down an incline

but good to know the car is saving us fuel

I have accidentally changed it from R to D while rolling backwards at about 5km/h. I was just giving it a quick flick so I could roll back a little more and accidentally went too far. My engine stalled as a result with no rough feeling so I was glad it did that.

yeah we stalled before on a ramp in D haha

(you know how Aurion don't roll back on most light to moderate inclines)

[mr_grumble2010]

That sounds horrible Steven. . You'd think they would put some kind of measure to stop it from happening.

Thanks for that DJ, I will take Hiro's word for it and leave it in D.

I had always thought there was a shift lock solenoid in place to prevent this? If it's anything like our old Honda Oddysey, it would lock the ability to change gears into P or R while the car was above 5km/h. Below this speed, you would hear a clunk as the solenoid would disengage.

Does the Aurion actually have this? Too scared to go and test it myself!

Why would you opt to coast in N ?

Firstly it's considered dangerous to do so (although I don't really find this to be the case)

Secondly, if it's to conserve fuel, then again, I don't think thatas the case.

Being new to Aurions, I cannot definitively quote, but as far as our Toyota Echo, and most other efi management systems are concerned, in particular to Manual transmissions (not sure about auto's), the most fuel efficient method of driving down hill is in gear with the foot off the accelerator.

In manual transmissions, there is a 'fuel cut' device that senses deacceleration >1400rpm and therefore cuts the injector pulses thus no fuel entering the intake manifold. Like I said I'm not sure about auto's, as this is my first, but I can't see why this wouldn't be the case ?

Anyone shed any light on whether this is the correct operation in the Aurion ????

Steve

[DJKOR]

....

Anyone shed any light on whether this is the correct operation in the Aurion ????

This is pretty much what Hiro Protagonist said and I quoted above.

I would say that it is most likely that the Aurion will do the same thing and cut the fuel. I've driven a new Corolla with the instantaneous fuel consumption display and in situations where the car is just coasting with your foot off the accelerator, it instantaneous fuel consumption drops to 0.0l/100km. I wouldn't think the Aurion would be much different since the Corolla shows that and automatic transmission can do the same.

[SCOOTA44]

Im not sure about laws in other states , but I believe it is illegal to coast in "angel" gear. though I have done it once or twice getting to a servo.