Thread: Idle-Jack Dangerous in low range reverse Puma

So it appears from the above posts that the TDCi is slower than the Tdi in low first forwards, but the Tdi is slower in low first reverse - is that right?

Originally Posted by DiscoMick

So it appears from the above posts that the TDCi is slower than the Tdi in low first forwards, but the Tdi is slower in low first reverse - is that right?

Yeah it seems to be the case. (Check latest posts in the slow race thread).

As revelation progresses, or goal posts move, it seems more likely that MrLandy is describing a perception that maybe the TDCi doesn't have the same level of available compression braking as the TDi, MrLandy mentions the wonderfully controlled and predictable compression braking of the TDi (contrasted to TDCi) in an earlier post. However:
- it is clear that overall gearing in the TDCi is lower than the TDi for both low first and low reverse.
- it is very likely true that the vehicle speed of the TDCi at engine idle in low first and low reverse is slower than the TDi (even when the TDCi idle is jacked to 1100rpm against the TDi running 800rpm)
(Hasn't been "slow-race tested")
- but the question is asked, does all this hold true on a steep sloping driveway (where of course the available compression braking will come into play)

So the focus is now on whether the TDCi is lacking in the compression braking department.

My experience (not empirical) is that on the steepest high traction slopes reversing at idle in low reverse gear - my 110 doesn't lack for any compression braking. Speed doesn't run away.

What I do notice is that if I were to feed in some throttle to go faster and then release the throttle - the TDCi takes its merry time to slow right back to crawl speed (idle revs - 1100rpm). This can sure give the impression the TDCi lacks in the compression braking dept. but if you wait a bit....

This is a result of that other undocumented feature I wrote about earlier, and if on slippery slopes is much valued!

In really tight situations like reversing a trailer down a steep slope - it may not be so appreciated.

You should try a stall recovery in a rural fire service truck! You have to start the engine with the gearbox in reverse and of course low range. It frightens the hell out of new recruits sitting in the back as it takes off backwards down the incline before the gearbox slows it down. The look on their faces reminds you of the first time you were in their position .

Originally Posted by Col 110

[...]Recently I attended a LROC Sydney training day
[...]

Originally Posted by Col 110

Not sure what result I would get being half way up the hill and stop - with engine running and then selecting reverse (low range) - taking the foot off the break and letting the clutch out to go in low reverse - i.e. would I get a "lurch"?

May need to depend on brake / clutch operation

You got it right - Depends on how good you are coordinating brake/clutch. If the slope is really steep getting it wrong can be disastrous.

One technique that can limit the risk is to "drive through the brakes". ie a bit like what happens when you forget to release parking brake and drive off, then release the brakes.

Hard to do if you are in a sphincter clenching situation so stick to the engine off approach.

(Sidetrack - Heheh... Sphincter clenching:
Have you ever been in such a scary situation, on a such a steep lean, that if you relax the sphincter your butt loses traction and you slip off your seat!)

Originally Posted by tact

(Sidetrack - Heheh... Sphincter clenching:
Have you ever been in such a scary situation, on a such a steep lean, that if you relax the sphincter your butt loses traction and you slip off your seat!)

hahah yes... forward and backward too..... although forward you have to stand on the firewall....