300D Turbo at 5,000 feet
 

When I lived at altitude for a year (~5,000 feet) my w123 300D NA took a significant performance hit.

I now drive a w124 300D (2.5L) turbo. I get 26 to 34 MPG, can travel 75 MPH all day long and have adequate acceleration for city driving. That's at low altitude.

I may move back to 5,000 feet.

How bad is the performance hit going to be?

Thanks.

Tolerable comparatively. The turbo has to work a lot harder to push the same PSI.

Ultimately the question is do I want to sell the car to someone at sea-level or take it will me to 5,000 feet.

After my experience with the 300D NA I would not want that at 5,000 for the mostly town driving I was then doing.

Curious how many of our diesel owners are at altitude.

Its a night and day difference between the 617 NA and 602 turbo.

Well sjh, all "NA" vehicles will take a hit at 5000 feet. Denver is at 5000 feet, often go there and with most vehicles it is hard to feel the difference. But with the 616 or even a 617 with no turbo, I would think it does show up. I think the power loss at 5000 feet with that 2.5 turbo will be hard to find. I don't really think you will find it at all. If you like the car, keep it

HeWhosNameShallNotBeMentioned lives in Federal Heights. He was continuously trying to get his turbos working better but hes never complained about lack of power.

I'm curious about your options. If you want to stay with a Diesel, a 98-99 E300 will mind the altitude less than a 2.5 turbo. In my corner of the country you can get a 94-95 E320 or E420 for what 2.5 turbos go for.

For perspective, I can feel my 87 300D working at altitude more through the temp gauge than though the seat of my pants. Heavy throttle application sends the gauge to 100*C in short order. Fortunately the cooling system sees that the engine gets no hotter. Since it has a #14 head, I'm very sensitive to such things, but no aluminum head Diesel likes to be overheated. charmalu would advise you to consider a 617 turbo for altitude.

Sixto
87 300D

That is likely due to the diminished cooling capacity associated with decreased air density.

I appreciate the comments.

I actually parted with my '99 E430 when I acquired the '90 300TD.

An attraction of the 124 diesel over the 210 was I thought it would be much more user maintainable and I was entering a period of limited funds and needing a reliable car I could maintain. Hopefully that period of my life is coming to a close.

BTW - where does look on their engine to determine the number of the head? Thanks.

On a 603 it's by the #2 injector. Just about the same with a 602 but I don't know the casting number sequence to tell you whether it's an original or updated head... or that it matters on a 602.

Sixto
87 300D

The atmospheric pressure at sea level is 14.7 psi.

The atmospheric pressure at 5,000 feet is 11.8 psi.

An n/a vehicle takes a hit of 24% in power loss.

A turbocharged vehicle has a cylinder pressure of 29.7 psi (assuming 15 psi boost) at sea level.

A turbocharged vehicle has a cylinder pressure of 26.8 psi (assuming 15 psi boost) at 5,000 feet.

The turbocharged vehicle takes a hit of 10.8% power loss.

However, you always have the option of turning up the boost on the turbocharged vehicle to 17.9 psi, in which case your cylinder pressures will be identical to sea level and the power level will be identical to sea level. Just don't return to sea level with the vehicle and use all available boost.

As TF mentioned, the cooling system might be seriously overburdened in this condition due to the limited cooling capability of the thinner air.

All of the above is based upon a standard temperature of 68 degrees. Of course, the cooler the air temperature, the greater the air density, resulting in greater power and additional cooling.

And that's why we keep Brian around :)

Is 17.9 psi a practical limit or based on an overboost protection solenoid (which a 2.5 might not have since it has vacuum wastegate actuator)?

Sixto
87 300D

Some folks still think I've got some value...........;)

I think the switch on the manifold is usually set to trip at something close to 15 psi. However, I'd bet that most don't work due to clogging over time. If the switch is limiting, obviously, you'd need to bypass it.

Well it is an aluminum head and this engine is much more temperature sensitive than my old 123.

Thanks.

I did gsxr's EGR swap so I have control over boost pressure.

I like to think I am a smart guy but I had not thought of Brian's suggestion.

THANKS!!!

However, I'll take a hit in the 1,000 to 1,800 RPM range before the turbo kicks.

That's a very interesting idea Brian. I'm going to spend some time with it.

Thanks again.