I have driven in the Colorado Rockies and other mountainous areas of the world.

With all due respect, as much as I love 123 diesels, I can't imagine anyone owning and driving one, turbo or no, that have to drive mountainous areas on a reglar basis.

If you only drive flat roads at high altitude, like Denver or Albequerque, then it would make sense, but not climbing.

Have a great day,

At 11,000 ft and climbing at the Eisenhower Tunnel or over Vail Pass the 300TD will easily outpull the 455 V-8 in my 74 Olds. The non-turbo is another issue altogether.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I believe the turbo diesels definitely have the advantage at altitude. If you live in Colorado and frequently need maximum power from the engine, the amount of power that you are getting is limited due to the thinner air at altitude. However, there is a very easy fix for this. Simply adjust the wastegate to allow a little bit more pressure in the manifold. If the limit at sea level is 11 psi, you can set the wastegate at 14 psi, or so, for 5,000 feet and the engine will behave the same as if it had 11 psi at sea level.

The only danger is that you must be careful if you drive the vehicle at sea level because of the potential of heating things up a bit too much.

Gasoline engines, without turbochargers, are completely restricted in power due to the lack of air.

I agree with Kerry. I was doing 60 MPH at 4000 RPM in 3rd gear in in my '80 300SD in the mountains near Vail CO and out running everything on the road. What fun to be able to pass others. Usually its the other way around.

P E H

I own a Gurkha 4WD with a factory OM 616 turbo which is rated at 91 bhp. To turbo charge the original OM 616, extensive modifications were done by MB. The pistons are oil cooled OM 617 type, exhaust valve is sodium cooled, oil pump is from OM 617 turbo and so is the water pump and radiator, also the OM 617 turbo oil cooler was fitted. The crankshaft has been given a nitriding treatment for strenghtning.

Consider all this for a mere 26 bhp gain. MB decided not to use ALDA but modified the pump for higher fuel delivery. I querried them about this and their answer was that the turbo boost is pretty mild at 8psi so ALDA wasnt required.

This is not needed. I set my wastegate to stop at 12.5psi in oklahoma (800ft) and it still stops at 12.5psi in denver (5120ft).

1psi inside the intake manifold at sea level is the same as 1psi at 14,000ft. The turbo spins faster to make up for the thinner air (Although it takes longer to spool up). That's why they have such an advantage at altitude.

I'm not sure of the science behind it, but I know that it's just the way a turbo works.

Yes, I do love leaving the non turbo big boys behind running up Sandia Mountian in NM in the TDI. Had a Mustang pop a cork trying to keep up in mountians with my '00 NB TDI.

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After thinking about it a bit more, I believe that this is correct. The turbo must work harder to achieve the pressure due to the thinner air, but 12.5 psi is 12.5 psi, no matter whether you are at sea level or at 5,000 feet.

I stand corrected.

Speaking of altitude, VW had on some IDI's with what looked just like the boost enrichment element(alda) on some non-turbos, but it was suposidly an altitude compensation device. Wonder if it did any good, I never had one..

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
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Mercedes also put the ALDA on the 240D. Mine has one. However, it is doubtful that you could turn it up enough to provide enough fuel to keep up with a turbo.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

I believe the 240 has an "ADA", which compensates for altitude only. Turbo cars got the "ALDA" which compensates for both altitude (when no boost is present) as well as turbo boost pressure. I'm not sure how much effect the ADA adjustment has, though!

Thanks for the clarification, Dave. It makes some difference, but not very much.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

No, that is not entirely true. You are measuring pressure relative to atmospheric. Here in Denver, the absolute air pressure is about 2 psi less than sea level. 12 psi is always 12 psi, true, but in terms of absolute pressure, 12 psi here is 24.6 psia, and at sea level 12 psi is 26.7 psia. Turbos have a huge advantage at altitude, and I can't wait to get one - my 300D is an unbelievable DOG.

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'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

So, if we compare psia at sea level with 12 psi boost (26.7 psia) vs. psia at 5,000 feet with 12 psi boost (24.6 psia) there is a difference of 2.1 psia absolute? And my original post was therefore correct? By dialing up the wastegate, you can acheive the same performance in Denver as you can at sea level? Very interesting

The turbo makes up for altitude, up to a certain point, and only when the turbo is spooled up. Off idle, the turbo engine is still doggy until boost builds. Power under boost is pretty much normal, until you reach a high enough altitude where ambient pressure is too low to feed the *intake* side of the turbo! I've heard of this intake starvation happening, but I suspect you need to be WAY high up for it to happen... I'd guess over 10,000ft elevation? Anyone know for sure?

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Dave
Boise, ID
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