Diesel performance at altitude

[ChrisB]

Hi all,

I have just returned from a camping/touring holiday during which we
travelled across the alps through southern Germany, Austria and into
northern Italy.

Generally I am very pleased with the ease and comfort with which my
75 handled, however I was surprised by the difficulty it had with the
mountain passes and wondered if anyone else has any
comments/experience to add.

This car is my first diesel, and I have had the Rover CDT to CDTi
power upgrade, which at low altitudes to my mind has now given it
good performance. However, at altitude (we eventually got it over the
Stelvio pass at 2700m) it was very short on power. The main problem
was getting up to 1800rpm when the turbo kicks in, then giving plenty
of power. Hill starts (even relatively slight) at altitudes above
1000m or so where not easy an needed plenty of clutch slipping to
keep the revs up. Most of the time I ended up crawling up steadily at
around 3000rpm in 1st gear as it would not hold 2nd when I needed to
slow down below 1800rpm for the frequent hair-pins.

I don't remember the altitude having such a marked effect on previous
visits to the mountains with petrol cars, and I noticed that the many
other diesel cars (mainly VW) tackling the same pass did not seem to
have the same difficulty.

I remember reading somewhere in previous postings that if the air-
mass-sensor is not doing its job, then power is reduced until the
turbo kicks in and am wondering if this could be the explanation.

Any thoughts before I get my dealer involved (it is a 2003 car and so
still under warranty)?

Regards

Chris.

[Malli]

Hi Chris,
I experienced the same on my car (make 7/2001). There is a really bad loss of torqe in altitudes above ~1500m (Monte Spluga / Solda near Stelvio) below 2000 rpm. According to my experience it has nothing to do with the engine tuning. The effect was rather the same before and after the reprogramming of the ECU. Cleaning the air sensor did not really help, I did not try to detach it, which seems to help at normal altitudes. If your dealer has a solution, please let me know.

grts,
Malli