Thread: TD5 at altitude (>4000mASL)

I've had several Td5's high up in the Pyrenees and in Italy and can confirm that they do suffer from a drop off in performance.

Not normally to the extents that you are describing though. Normally you end up with a lack of power and black smoke as it over-fuels for the amount of o2 available.

This is not generally a problem limited to TD5s. It's the laws of physics at work!!

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I would say that's about normal.
At that altitude ( almost 13000 ft) It's predominantly about atmospheric pressure with temps playing a less significant role.

The performance drop was probably exacerbated by the weight you were carrying as was the temperature rise.

The thing to remember is that at altitude, there is less O2... Not because there is less O2 but it is because the air isn't as dense. As such, there's less of everything!! In humans, we start to notice this at approx 3,500m as that's where you can see the first signs of HAPE & HACE (altitude sickness). (OK... I'm a mountaineer & have done some training in emergency mountain medicine.)

With cars, you're going to notice different things depending on the design:

That temperature rise is probably going to be due to the 'thinner' air flowing through the radiators. It isn't going to be able to cool as well as 'thick' air.

Performance can be split into 2x areas: NA vs Turbo.

If you are in an NA car, you are really going to struggle as there is nothing there compensating for the air density. e.g. A guy I know took his V8 D2 up to Everest Base Camp and it drove like a dog - Gutless!!!

With a turbo-charged car you'll stand a much better chance as the turbo charger will be compensating for the air density. However, to do this, the turbo will be working harder and relying on greater flow through the rest of the system. As such, you might find that the hoses, air-filter or even the RAI might then be limiting things. Don't forget that the effectiveness of the intercooler will also be greatly reduced due to the thinner air flowing across it (see above).

Make sense?

M

maybe fit some airbags...

just heard about this mentioned on QI show recently.

Mount Everest news - Mount Everest by climbers

not a td5 but higher than your going.

not a TD5 but I took a Diesel Pajero up to 4700m fully loaded. performance fell off and I blew a lot of black smoke but I could still get around relatively normally. What you are describing does not sound right.

Does sound a bit extreme but it's certainly not unusual for smaller capacity motos to become push bikes at hose kind of heights and it not like a Tdi is a tower of power at the best of times...

I'd say that a bit of poor quality fuel, anything remotely approaching a dirty air filter and a bit of weight on board, the kind of inclines your likely to experience at those altitudes (unles you're puttering around on the altiplano) and I'd say low gears and maybe even low range is on the cards.

Originally Posted by Leyland1980

Just wondering if others have experience of driving a TD5 at altitudes over 4000mASL?

Having driven to ~4300m ASL in Ethiopia in a non chipped (no EGR) 2004 TD5 110 I suffered from a serious lack of power such that when presented with even the slightest of inclines low range had to be engaged I also noticed that the engine was running at higher temps than normal despute the ambient temps being low 10-15oC. The vehicle was heavily laden.

Are these symtoms "normal"at altitude? or as a result of something else and then exacerbated by the lack of O2?

Is there anything that can be adjusted to improve performance at altitude?

Many thanks

John

John there is a sensor in the side of the airbox on Td5's (ambient air pressure) that has an input into the fueling strategy. As I understand it fueling is reduced as ambient air pressure lowers due to higher altitude and less 02. Probably in place mainly for emission/pollution control.

I have read on another forum that a trick to increasing power at altitude on the Td5 is to disconnect the AAP sensor giving a default value of 100kpa (sea level) to the ECU this will increase fueling.
Probably get a bit of black smoke but should increase power.

The other possibility is that the AAP sensor is faulty.

Cheers,
Paul.

Altitude should really make no difference to a turbo charged vehicle. Aircraft have been using super/turbo chargers for this purpose for over 80 years. The turbo will just spin to provide the required pressure/density (boost) demanded by the ECU, ie P1V1T1=P2V2T2. (can be a problem - see below)

However, what may be happening is that the turbo simply cannot make the boost; ie it is running out of puff. (This too has its dangers - The turbo will spin to excessive RPM to attempt to make the boost because it doesn't have the load)

[All please NOTE - This is also a problem that can be caused by "unclean air filters and intercoolers". Turbo overspeed can cause turbine creep and failure, compressor failure, oil film breakdown/overheating and bearing failure. Catastrophic failure, not necessarily at the time, but later under what may be mundane conditions]

Perhaps you need to have a bigger turbo, different scroll, whatever; to make the boost. but then this would effect SL performance. Too much lag! If the vehicle is always (or spends most of its time at higher altitudes then the higher flow turbo would be the answer) Alternatively a plumbed 2nd stage turbo that can be switched in for higher altitudes e.g. Road Rods with switchable exhausts for drag racing; OR

A mechanical supercharger that can be magnetically clutched in (downstream?) of the turbo. Could be done off of an aneroid capsule or the system was really swish off of a piezio sensor.

Aircraft used to use geared (2 speed) superchargers Merlin and Griffon are good examples. Yanks used big multi-stage turbos, on their in-lines and radials.

A simpler solution (but more costly) may be a late model bigger turbo with the latest (for cars) variable inlet guide vane technology.

All depends on how much time the vehicle spends at altitude and how much one wants to spend.

Might be simpler/cheaper/easier to order a new vehicle but specifiy as a special order to the manufacturer that for the particular vehicle it needs to have the ECU and turbo modified for high altitude; then his engineers do it. Probably have done it already as a design consideration.

Whatever is done in regards to any of the above needs to be properly "Engineered", not the local tinkerer down the back street.

Sorry if this all is a bit long winded.

[With respect to a previous comment: All Fuel Control Units (ECUs) will reduce fuel delivery to match the O2 available, even those on the most modern turbo fan engines. However, those cunning buggers increase the engine speed so the the compressor/s spin up to increase the pressure/density of the air available to the burners ]

RF