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post #1 of 6 (permalink) Old 06-24-2014, 03:04 PM Thread Starter
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High altitude tuning

As I'm currently living in Bolivia I've been driving some trails at very high altitude eg. 4500m/15000ft+. I use my Commander to go climbing in the Andes. It's really an amazing car - takes me everywhere a llama can go.
Now I'm planning to drive up to 5500m/18000ft to climb a volcano. I've been wondering if I should tune the air/fuel mix or is this fully automatic? So far I haven't had any problems except maybe some lack of power which can typically be solved with LOW mode. But I wouldn't want to be stuck with a car that won't start at these heights. Towing services are very limited - except for the llamas
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post #2 of 6 (permalink) Old 06-24-2014, 03:29 PM
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The engine control is electronic and adaptive with a feedback loop from the O2 sensor. So, yes, it is automatic to tune itself for altitude.But, 18k ft altitude? Don't know if the electronic controller or other pars of the vehicle have been tested for those extremes, so you can't garuantee it will perform as expected until you try it.Trying to tune it yourself? There are flashpac tools that let people tailor the fuel and spark curves or load premade programs that improve performance. Since the engine controller is closed loop for all but Wide Open Throttle, any tuning of fuel is negated in a few minutes as the adaptive engine controller uses feedback from the O2 sensor to tune the engine back to the ideal 14.7:1 air fuel ratio. So it only gets more power at wide open throttle. Well for fuel, you can play with the spark curve to get more power at part throttle.But the only tuning I've heard of is for more power, NOT better adaption to higher altitude. So, I'm guessing your safer just relying on the electronic controller tuning the motor itself for the extreme altitudes.


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post #3 of 6 (permalink) Old 06-24-2014, 05:39 PM Thread Starter
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Ok, sounds that the only way to find out is to try it :-)
The volcano in question is Parinacota :
http://www.openstreetmap.org/#map=13....0999&layers=C

I've been told that the trail goes a lot higher than what is shown on the map.
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post #4 of 6 (permalink) Old 06-25-2014, 08:35 AM
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Take lots of pictures and post them giving us a report on how your Commander performed in those extreme conditions! Good Luck, sounds like a lot of fun!

The only thing I can think to prepare, is a brand new air filter (the least resistance possible for the low air pressure) in fact consider getting a K&N air filter.

K&N air filters are a cotton weave filter that has much larger openings and thus flow with much less resistance, you spray a special oil on it that soaks into the cotton and the oil captures the dirt, so that if filters out the dirt well enough but still give less resistance to air flowing into the motor. Plus, they are re-usable, you clean them and then re-oil them, so if you get a K&N Air Filter make sure its clean and fresh just prior to the trip.

Fuel Octane, you want to check this out because I'm NOT sure, I may have this wrong; BUT, the higher the altitude, i.e. lower the air pressure, the less octane you need in the fuel to prevent detonation/pre-ignition. Higher Octane Fuels usually have higher vapor pressures, meaning its harder for them to atomize and remain suspended in the air as a vapor, while lower octanes do this more easily. Most Manufacturers, including Jeep/Chrysler, have TSB's out telling the Dealer's if they have customers complaining about hard starting and stalling while cold in cold weather, to ask them if they are using higher than recommend Octane fuel in the vehicles, and going to recommended octane usually solves the problem, its because of the vapor pressure issue, or volatility of the fuel.

*What I do know for a fact, using higher than needed octane fuel does absolutely nothing to help your performance, in fact, if it is a lot higher than needed by the conditions, it can create problems with the motor running as well as it should, at least when it is cold, like hard starting and stalling at idle. Of course if the fuel octane is too low, you'll get detonation/pre-igntion.
*As well, I do know for a fact that higher altitude (lower air density) creates the conditions that reduces the chances of detonation/pre-ignition and you can safely use lower octane fuel, even lower than recommended. But of course its always possible that you could pick a lower octane fuel than needed by the higher altitude that isn't high enough for that low of an octane. Lets put it this way, in the mountanous regions of the U.S., about 4k ft or higher, the gas stations typical sell fuel that is 86 octane when the standard low octane fuel recommended for all cars (that use it) is 87 octane.
*What I don't know, is what is the best octane for your Commander at 18k ft, or if the lowest octane fuel sold in that area is even low enough for trying to operate your Commander at 18k ft. But if I was you, I would buy the lower octane fuel the higher you get.

And it you run into problems, like hard starting, stalling, rough running, misfires, etc at 18k feet, I'm betting it will be because the fuel won't atomize fully and stay in a vapor well at that low air density.

As well, South America has a lot of ethonal in their fuels, I guess it varies from country to country or region, NOT sure how that effects the fuel at high altitudes, I would guess it would be better, but I might be totally wrong and less ethonal is better at higher altitudes.


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Last edited by Mongo; 06-25-2014 at 08:40 AM.
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post #5 of 6 (permalink) Old 06-25-2014, 09:55 PM Thread Starter
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Thanks,
I probably won't find K&N here, but will change for a new air filter in any case. Good points regarding the fuel. I'll check with a friend who owns a gas station here. Maybe the standard stuff over here is already special octane + mix as La Paz is already pretty high up.

The first time I went higher up I didn't actually pay any attention to the whole issue. I left the Commander at 4800m/15700ft and only when I came back to the car it suddenly hit me: Will she start ? Well she started just fine.
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post #6 of 6 (permalink) Old 07-07-2014, 07:13 AM
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You might see if there are any of those supercharger kits left. I believe they made them for the 4.7 a few years ago.

2007 Commander 4.7 QTII pulled behind 2000 Dutch Star Motor home
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