Thread: So what is the correct way to drive a Td5 Auto??

pretty much as per a manual

never turn on the cruise control, its not proactive enough.

gently wind it up before a climb (I always sit a little below the speed limit to allow for this) and aim to hang onto lockup as long as possable by easing off as you slow down,.

keep the engine working at peak torque RPMs when you're trying to accelerate then use as little throttle as possable to maintain speed. if you drop off of the torque curve manually knock it back a gear then allow it to climb slower but at the peak torque of the next gear down. generally if you knock it down a little earlier and can get 3rd to lock up you can stay locked up in 3rd for a lot of the climbing work. (unless your loaded or towing)

manually downshift to maintain speed when you decend hills and dont use the brakes if you can avoid it (dont take risks on corners)

fit an EGT guage and boost gauge and try to keep both of those as low as possable for as long as possable.

Listen to it and watch the exhaust, engines and gearboxes talk to you while your driving and will let you know what you need to do once you learn their lingo.

Dave's spot on, Regards Frank.

Originally Posted by Tank

Dave's spot on, Regards Frank.

He usually is

Originally Posted by catch-22

On a recent 27 hour driving trip it seemed my brother-in-law was getting better fuel economy than I. He is a trucky so I expected that.

So I started thinking about what would be the best way to drive, say a Td5 auto, to maximise fuel economy. So here are the scenarios -

1. Use cruise control or feather accelerator? Cruise will not do well on hills as it cannot anticipate, better leave on cruise and give it some help before the hills by overriding it.
2. Before a slightly inclined hill that will slow the revs, maybe make it labour a little, but not drop back gears? (accelerate before hill, force drop back of gear (auto)) That is just not going to happen, manual drivers are more likely to labour their engine and often express irritation at the fact that the auto drops down a gear sooner than they would in the manual.3. On a steep hill that must drop back gears? (low gear high revs, mid gear, mid revs, what revs)
I try not to let it get up above 3000 rpm
Interested to hear, especially from truckies.......

Not a truckie but I expect they anticipate on hills and don't over rev their engines as the diesel can use the torque. With the manual gearbox they go for an EGT with the probe after the turbo, if the temp starts to rise they back it down a gear. All that is happening is your hitting the accelerator and more fuel is supplied until it can no longer burn it in the combustion chamber and starts to burn in the exhaust. Drop it down a gear get the EGsT in check, not because it will just just damage your engine but because it is wasting fuel.

Originally Posted by slug_burner

Not a truckie but I expect they anticipate on hills and don't over rev their engines as the diesel can use the torque. With the manual gearbox they go for an EGT with the probe after the turbo, if the temp starts to rise they back it down a gear. All that is happening is your hitting the accelerator and more fuel is supplied until it can no longer burn it in the combustion chamber and starts to burn in the exhaust. Drop it down a gear get the EGsT in check, not because it will just just damage your engine but because it is wasting fuel.

A diesel is more efficient at high load at low rpm than at lower load in higher rpm.
Don't think of just EGT, think of EGT and rpm. How much hot air are you pumping out the exhuast?
500C at 3000rpm is burning a whole lot more fuel than 600C at 2000rpm.

Originally Posted by Dougal

A diesel is more efficient at high load at low rpm than at lower load in higher rpm.
Don't think of just EGT, think of EGT and rpm. How much hot air are you pumping out the exhuast?
500C at 3000rpm is burning a whole lot more fuel than 600C at 2000rpm.

So should the auto hold onto the gears longer when climbing a hill? Once the TC drops out of lock you will just start to heat up the fluid and the engine will start to rev higher.

It must be a difficult line to walk for the auto designers, economy vs a level of performance.