Thread: Defender "slow race" - TDCi vs TDi

Originally Posted by tact

I wonder if the TDCi behavior that has you worried is that other behavior I wrote up in the other thread: the one about how the TDCi takes its time to drop revs to back to idle (any gear, low or high range, on or off road).
( Idle-Jack Dangerous in low range reverse Puma )

Yes that's exactly what it is and that's why it's dangerous IMO. In low reverse on a steep hill there's no time to let the revs drop, because by then you're either on your way far too fast down hill or you've slammed into the rock wall or trees at the bottom. It's counter intuitive as to what low range is designed for in that situation. ...going up hill or on the flat, sure the idle jack can be useful. Downhill and especially in reverse I reckon its dangerous.

Originally Posted by MrLandy

Yes that's exactly what it is and that's why it's dangerous IMO. In low reverse on a steep hill there's no time to let the revs drop, because by then you're either on your way far too fast down hill or you've slammed into the rock wall or trees at the bottom. It's counter intuitive as to what low range is designed for in that situation. ...going up hill or on the flat, sure the idle jack can be useful. Downhill and especially in reverse I reckon its dangerous.

Ok. Gotcha. In this case there are two distinctly different situations and really you just have to know your vehicle, know the right driving techniques, know your own limits:
Situation 1. Very tight situation like manouvering a trailer in reverse on a steep driveway. To avoid the slow return to idle:
- don't touch the accelerator in the first place. In low reverse you cannot stall the engine and in such a tight place why would you touch the throttle.
- if you never quite get the clutch pedal fully up (because it's THAT tight) idle Jack won't even kick in and anti stall is your best friend.
- be aware that if you have room to let clutch right up revs will gently go up from 800 to 1100 a second or two after the pedal tops out. Know your vehicle, and know you are still moving slower than a TDi.

Situation 2. Offroad where you are on a long slippery hill in low first or reverse and basically just want to be able to keep one of the vehicle's pointy ends facing travel direction, and maybe have just enough control of the long slide as to aim off from big trees...:
- idle Jack does no harm and brings no surprises, it actually helps keep the wheels turning at a more useful speed. And the slow return to idle after any throttle you use to control the vehicle direction during the sliding descent is a pure gold asset. (I.e. Sudden! reduction in wheel speed will break what ever traction you gained with the counter-intuitive throttle action and put you more out of control again. The TDCi slow return to idle revs minimizes this driver error)

Thanks Tact good info for newbies, but I'm very aware of technique.

In my situation there was no throttle. Letting the clutch out alone, combined with gravity in reverse, raised idle. And braking had little effect whether clutch in or out. The idle jack was fighting the brakes until it subsided. Engine braking was non existent due to idle jack.

Originally Posted by MrLandy

Thanks Tact good info for newbies, but I'm very aware of technique.

In my situation there was no throttle. Letting the clutch out alone, combined with gravity in reverse, raised idle. And braking had little effect whether clutch in or out. The idle jack was fighting the brakes until it subsided. Engine braking was non existent due to idle jack.

Which brings us back to (10mths ago in the other thread:Idle-Jack Dangerous in low range reverse Puma ) :- That just doesn't happen in my vehicle. If I don't touch the throttle and let the clutch out nicely in reverse low: the vehicle begins to move very slowly (much slower than a stock TDi) at idle around 800rpm. Then a second or two later the revs gently rise to 1100rpm (vehicle speed, by all accounts, still slower than a TDi).

If yours (or any one else's) behaves differently then maybe there is a problem that needs LR to fix.