any experience with a 12HT at altitude?

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Sep 19, 2009
Houston, Texas and Colorado every July.
I'm about to install a 12HT in my HJ45. I use this truck to camp in the Rockies up to about 12000'.
My current engine, an H, really struggles with the thin air. Going slow on the trails is of course great but on the asphalt to the trails is a bit of a pain. I don't mind slow but 20-25 mph over the passes is a challenge and, I'm concerned that it is to much on the motor.

So, any advice and preferably experience from anyone with a 12HT at altitude?

Experience desired!


I don't have a 12t, but my 60 has an Isuzu 4bd2tc turbo diesel engine. We spend a fair amount of time in the 7,500 - 11,000 elevation range each year. The diesel works well, but has a few quirks too.

I get a fair amount of black smoke the higher we go, and she will put out some white smoke on starting. She also wants more glow plug time on a cold morning the higher we go. The Isuzu 4bd2 is a IDI engine which like some glow plug to start, a DI engine may work different.

Our mileage is also lower by about 15% (+/-) the higher we go from the combo of elevation and the climbs I suspect.

At 10,000 I would estimate that power is down by 20 - 30% compared to sea level (where we live). But the power loss is about the same as a gasser, and way less than a non-turbo diesel. We met a couple last year with a 2h in a 60 going over Sonora pass (7,000 - 10,000+). They had lots of black smoke and we flat smoked him on the climb! The turbo really helps.

Hope this helps.

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