TD engine braking

Has anyone noticed the lack of engine braking in the D40 TD auto's in low range. I was recently in the high country on a steep rutted out track and when decending in low first had to ride the brakes all the way down due no engine braking , drove a mates auto diesel 100 series and perfect no brakes just let it walk down. Is this normal (my first auto diesel) ??

Its a small motor, the compression ratio is relatively low to so less engine braking.

Aftermarket transfer gear's will fix it.

Is your mates Cruiser a 1HZ or 1HDFTE ? The 1HZ will have the better engine braking out of the 2.

Dave.

BDW said:

Has anyone noticed the lack of engine braking in the D40 TD auto's in low range. I was recently in the high country on a steep rutted out track and when decending in low first had to ride the brakes all the way down due no engine braking , drove a mates auto diesel 100 series and perfect no brakes just let it walk down. Is this normal (my first auto diesel) ??

Click to expand...

No problem with mine....I done a fair amount of work in the High Country and down Bendethra way and find low low to be lower than my old GU manual with very good engine braking.

Mates 100 series is 4.2td whichever that one is ?.
I,ve got a gu 4.5 man, and the engine braking in that is brillant dose'nt matter how steep it just walks it self down no brakes. My wifes got a 3ltd rangie auto and that is as good as the patrol (with out using the hill decent)
With the nav it will hold it to around 15kmph which is way to fast on steep tracks. I guess its one of those things which are hard to get a feel for on a test drive in town. Anyway i just thought it would be better, slower.
Thanks for the feed back

Its all about compression ratio

Rule of thumb
old indirect injection diesels>DI TD>common rail TD>petrol

Not sure how short the fist gear is in the auto but if its longer than the manual that wont help either

BDW said:

Mates 100 series is 4.2td whichever that one is ?.
I,ve got a gu 4.5 man, and the engine braking in that is brillant dose'nt matter how steep it just walks it self down no brakes. My wifes got a 3ltd rangie auto and that is as good as the patrol (with out using the hill decent)
With the nav it will hold it to around 15kmph which is way to fast on steep tracks. I guess its one of those things which are hard to get a feel for on a test drive in town. Anyway i just thought it would be better, slower.
Thanks for the feed back

Click to expand...

In most cases, the petrol motor will have a better engine brake because the air inlet into the engine is "choked" via the throttle's butterfly valve. This causes the engine to hold a vacuum on the downward piston stroke aiding the engine retarding (or braking).
A diesel engine breathes one full belly of breath every stroke and then has to rely on the compression ratio to retard however, having said that, once the air is compressed and the piston goes over top dead centre, the piston is pushed down at almost the same force as it took to compress the air. Thus very little engine retarding occurs.
To get a diesel to retard well, fit an exhaust brake. That will have a similar effect as the choking of a petrol engine.
The Range Rovers transfer case gears are 3.3:1 in low range and therefore multiply the engine brake effort by 30% more than what a Patrol etc would do in low range.
Remeber that a torque converter in not the greatest of couplings when used to retard an engine however, fitting a manual lock-up as well as an exhaust brake makes a huge difference.

Foxbat said:

In most cases, the petrol motor will have a better engine brake

Click to expand...

Good explanation, but this is not what I have experienced in real life? The most direct comparison being downhill descents in a petrol (3.4) vs diesel (3.0) Prado. Same gearing, same weight, same hill - The petrol Prado had much more run on

Would it be possible that the much higher comps of the diesel offsets the advantage of the butterfly closing with closed throttle?

Try and lock the auto in 1st gear and see how you go.

Dave.

nathan96 said:

Good explanation, but this is not what I have experienced in real life? The most direct comparison being downhill descents in a petrol (3.4) vs diesel (3.0) Prado. Same gearing, same weight, same hill - The petrol Prado had much more run on

Would it be possible that the much higher comps of the diesel offsets the advantage of the butterfly closing with closed throttle?

Click to expand...

Can't say for sure but the torque converter on the diesel is probably set to come on at lower revs and therefor may have greater effect on the engine. The diesels gearbox shift pattern is set differently to that of a petrol which may also have an influence. You really have to compare apples with apples. Too many variances between petrol and diesel to get an accurate 'comparison'.