Thursday, Dec 04, 2014 at 13:15
If you have grown up with petrol engine pre-conceptions a lot of things about driving a diesel will seem strange.
In may ways the behaviours could not be more different.
Diesel engines operate most efficiently arround where the power and torque curves cross....this is where the engine develops the maximum torque and the maximum power possible both at the same time.....they will both drop away shortly after...... and this is regardless of manual or automatic gearboxes.
I don't know that it is for your engine but for my small 4 cylinder that is around 3000rpm.
OH and...with turbo diesels this band will be narrower than it would be for a similar AN diesel.
If the manufacturer of the vehicle is half smart they will have matched their transmission with this behaviour....and generally toyota are pretty good at this.
In a diesel lower RPM does not necessarily mean better fuel economy.
There is a very good reason most diesels come with a tacho.
If you listen to the engine it will tell you.....it might be heavy
rock and roll, but it should be a happy song.....if it sounds like a durge it wont be running efficiently.
By all means look up the torque and power curves for your engine.
Watch your EGT
Get that scan guage and watch your tranny temp.
But above all listen for the song
the differences.
with a petrol engine
pushing for the most power, you will hold in a gear till the engine will not comfortably rev any harder till you pick the next gear and you will keep the revs high
Pushing for most economy you will run the highest gearing the engine will tolerate and keep the revs low. in all cases.
With a diesel engine
Pushing for most power, you need to keep right on top of that power and torque curve.....maximum power will not be generated below that band and power will drop off above that band.
You should shift to the next highest gear as soon as the vehicle will pull
well in it.
Rev'ing out beyond the power band achieves little.
Maximum economy will occur at two
places in a diesel rev range.....
lightly loaded with light throttle application right at the bottom of the power band.
Heavily loaded toward the upper end of the power band where the torque and power curves cross.
OH btw if anybody tries to say their diesel has a fairly flat power curve.....they are kidding themselves......most have less than 50%to 70% of their maximum power a thousand reves either side of the peak.
Ya gota keep on that curve.
cheers
AnswerID:
542537