High Altitude Tuneup

[gdl40]

I recently moved my 84 300D from Sacramento to Lake Tahoe, and the car is very sluggish now. Is there a way to tune the car for high-altitude driving? Thanks!!

Well, your 300D will not win any drag races at high altitude but correctly adjusting the ALDA will help give you reasonable performance. Are you familiar with this adjustment?

[gdl40]

Thanks for your response, Craig. No, I'm not familiar with adjusting the ALDA, buy will research the threads. Any help will be appreciated.

This is a good place to start:

ALDA issue threads

The bottom line is that carefully adjusting the ALDA in the CCW direction will give you more fuel at part throttle, but there are some checks you should perform before you start adjusting things.

This thread includes some good advice:

http://www.peachparts.com/shopforum/diesel-discussion/24796-performance-problems-85-300d-turbo.html#post128721

[layback40]

Thin air is hard on a diesel. Keep your air filter clean.

[dude99]

might also be worth checking to see what kind of shape your turbo air seals are in and also if your wastage is actually letting the turbo build up to the correct pressure.

[kerry]

If you can notice the difference, something is wrong with your turbo. Relative to NA gas and diesel engines, your turbocharged engine should be acting pretty much like it is still at sea level.

[Gillig]

Altitude should be no issue for diesels, even at 10,000' they should have reasonable off-idle power with no boost when tuned correctly.

Valve adjustment
Check linkage
Make sure you're starting in 1st
etc etc

There is a whole list of things to do to get the engine in top shape.

[kerry]

Originally Posted by Gillig

Altitude should be no issue for diesels, even at 10,000' they should have reasonable off-idle power with no boost when tuned correctly.

??? Am I missing something? All internal combustion engines have reduced power as altitude increases due to the fact that there is less oxygen to burn. Being a diesel makes no difference.

There is a difference between driving a turbo diesel at sea level and 6000 feet; I often drive between elevations and can feel the difference. All internal combustion engines are affected by air density, but turbos are better able to compensate.

[junqueyardjim]

The school bus I drive is a 3 year old transit Thomas with a "7" series Caterpiller engine. It has a tag on it saying it is rated to 185 hp up to 10,000 feet. It is turbocharged and intercooled and does really run well. Now it could be that it is rated at more then 185 hp at sea level.

[cirrusman]

I bought my '83 300SD in Anaheim CA, and drove it all the way to Salt Lake City UT. I didn't notice any changes in performance. The car was a good climber then and it is still now. It was slow pulling away then, it still slow pulling away now

[Gillig]

Originally Posted by kerry

??? Am I missing something? All internal combustion engines have reduced power as altitude increases due to the fact that there is less oxygen to burn. Being a diesel makes no difference.

"they should have reasonable off-idle power with no boost when tuned correctly." I never said they would have full power.

A 300D moves 21.48lb/min at sea level with 12psi boost. At 10k' you would need 22.5psi boost to flow the same amount of air and get the factory 125hp, but that would blow up the turbo from over-speeding. With 12psi you'll get enough air for about 93hp instead.
Thats far better than a non-turbo 300D would fare, it would have just 60hp at 10k', less than a 240D at sea level!