TD5 at altitude (>4000mASL)

[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

[Yorkshire_Jon]

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!!

Sent using Forum Runner

[strangy]

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.

[camel_landy]

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

[Yorkie]

maybe fit some airbags... ;)

just heard about this mentioned on QI show recently.

Mount Everest news - Mount Everest by climbers (http://www.mounteverest.net/story/stories/Chains,wedontneednostinkinchainsJan182004.shtml)

not a td5 but higher than your going. :cool:

[jasonedu]

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.

[n plus one]

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.

[harro]

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.

[Rick Fischer]

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

[strangy]

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)

RF

Apart from the use of turbo chargers, this is over simplified and incorrect.
Too much to be written in a post here for a correct explanation.

[Rick Fischer]

As you say it is simplified, and still too long winded. Hence the "properly engineered" comment at the end.

Incorrect. Mmmmmm! Over simplified perhaps, spent 40 years as AME, LAME, and CAA/CASA SAWI, on fast movers, helos, and heavy metal; and bug smashers in GA; gaining Diplomas in Mech and Aero Engineering with an Auto mech design major thrown in..............and somewhere in there I also used to teach the stuff for both airframes and engines.

Seeing the PT6? on your post I assume you can decipher the jargon :)

Cheers

RF

[strangy]

I am guessing what I quoted from your post is a typo or grammatical error?
Or are you really saying a turbo charged motor isn't affected by altitude?

Cheers

[Rick Fischer]

That is correct........as far as it goes, and the reply gets long winded.

0 boost at MSL is Std Atmo, ie no vacuum, so what the piston feels before ignition is a full charge at "Std" pressure/density. Whether talking in" Hg or psi anything above that is boost. As the engine goes up the turbo will maintain the boost within it's controlled range until it reaches the density/altitude where it just cannot flow anymore air to maintain pressure, though if the waste gate is not properly controlled they will overspeed. The compressor output and the turbine input must balance.

Personally, when I had Td5 and before that the Tdi going over Packhorse pass at around, is it, 6000 to 7000ft my discos didn't even know they were that high; but compared to the situation in this thread he is talking in meters. They were much superior to my NA Rangie V8 which would be panting.

One of the things the Yanks found out with aircraft turbos initially was that unlike mechanical superchargers the turbos would continue to spin up until the waste gate opened. However, in that learning process they spat a few out the back and consequently improved the waste gate control, the compressors and turbines.

Simply, the turbine extracts "Heat", as long as that Heat is available, the compressor will spin, as the density altitude decreases there is less load on compressor tending it increase RPM until the load matches the turbine torque, ie maintain pressure.

An auto diesel turbo is designed to increase power and torque by increasing the air supply,(and injected fuel) will tend to maintain MAP until the compressor simply cannot flow anymore air to maintain the pressure. An auto turbo diesel doesn't know what altitude its at! The turbo will tend to increase pressure till the waste gate opens, or it cannot flow enough air. Luckily in "hot rails" the ECU senses the MAP and injects the correct amount of fuel. Obviously, once the turbo flow limits are reached the amount of fuel injected is reduced, and of course power and torque.

This is where one can start to move into a "risk" zone. If the waste gate doesn't open, and compressor output pressure can't open it, the compressor will be trying to balance the turbine torque, ie increase RPM, unless controlled by another agent. On an aircraft engine the waste gate will one way or another also be barostatically controlled.

For us normal punters high altitude can be simulated by having a blocked/restricted intake tract; ie very high differential pressure across the
filter/s and "overspeed" becomes a risk.

A turbo charger's rotating assembly will always increase or decrease RPM to get the compressor load to match the turbine torque (Heat input). That's why a turbo is one of those things which provides something for nothing :)

On my Bimmer I've made running out of puff a virtue (for me). I ended up using a small turbo to give me low RPM grunt. It runs up quickly to 12psi then as the engine rpm increases the turbo slowly comes back to 7psi. The turbo simply cannot flow enough air. For the short durations that it happens it is not a problem.:D

Apologies for the long winded reply, and apologies if it still doesn't come across. I've reviewed and corrected it a few times. This medium is a bit limiting.

The long and short of it is: A turbo charger's rotating assembly will always increase or decrease RPM to get the compressor load to match the turbine torque (Heat input)

[weeds]

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.

bumping an old thread.......as I research my trip aboard

I have been following an overland blog and the couple have a troop carrier, they mention a re-tune was successful in reducing the effect altitude was having on their troopy

just wondering if there is an option to have a second map/tune to suit altitude which you could swith to as required, well in my case i'd probably just swap the ecu's over.

also wondering if anybody has tried Paul's suggestion of disconnecting the AAP Sensor.....something I will have to track down as I have no idea where this sensor is.

cheers