| rrobinet |
On page 185 of the 2004 MDX Owners's Manual it states:
"The GCWR must be reduced 2 percent for every 1,000 feed of elevation"
By this formula, at Lake Tahoe at 6,500 feet the GCWR should be reduced by 6.5 * 2 = 13%.
GCWR 9835 lbs.
GVWR 5730 lbs.
=payload @ 0 ft 4105 lbs
reduce payload @ 6500 ft 13%
=GCWR @ 6500 ft 8556 lbs
=payload @ 6500 ft 2826 lbs
=payload reduction 1279 lbs
=payload reduction 31%
So, it appears that the MDX can tow 1/3 less at 6500 feet than at sea level. Does this make sense? What mechanical limits are associated with high altitude? The engine puts out significantly less HP at high altitudes, so is Acura concenred that we can't climb the hills around Lake Tahoe fast enough pulling a 4,500 lb boat?
:p |
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| renov8r |
'pre-ignitions" or ping -- the reduced oxygen will mean that the computer will squirt less fuel into the cylinder (to try and keep emmisions in line with specificed limits) BUT that might result in the moter running hotter.
As the cylinder heats up ping is more likely. While the knock sensor would then reduce timing it would also result in decreased power. The driver would probably respond by putting the pedal to metal more often, but if the vehicle is already at is limits the computer probably won't be able to keep taking out timing and eventually you would get heavy pre0ignition which could destroy a piston, cylinder head or connecting rod.
Mind you, there would PLENTY of things to warn you that you cannot keep pushing -- like the lack of power and audible noise. Acura is almost certainly thinking of worst case and the lawyers want to "CYA" as far as warranty claims... |
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| mogur |
No, it will "squirt" less fuel in to the cylinders but that is only because the air is thinner so it must do so to maintain the same fuel to air ratio or mixture as at sea level. (One of the reasons that carburated vehicles used to run so poorly at higher altitudes was that carburators could not compensate for this and thus the mixture wound up being horribly overrich.) Thus the heat produced for a given amount of power is almost exactly the same. In fact, the tendancy to ping is actually reduced at higher altitides because the compression pressure at WOT throttle drops correspondingly with the reduction in atmospheric pressure. That is why octanes at high alttitude locations are lower than at sea level.
The reason that they reduce the towing capacity at higher elevations (and most all gas engine manufacturers do this) is two fold: Reduced maximum power and reduced cooling (radiator, brakes, etc.) due to thinner air.
Tom
quote:
Originally posted by renov8r
'pre-ignitions" or ping -- the reduced oxygen will mean that the computer will squirt less fuel into the cylinder (to try and keep emmisions in line with specificed limits) BUT that might result in the moter running hotter.
As the cylinder heats up ping is more likely. While the knock sensor would then reduce timing it would also result in decreased power. The driver would probably respond by putting the pedal to metal more often, but if the vehicle is already at is limits the computer probably won't be able to keep taking out timing and eventually you would get heavy pre0ignition which could destroy a piston, cylinder head or connecting rod.
Mind you, there would PLENTY of things to warn you that you cannot keep pushing -- like the lack of power and audible noise. Acura is almost certainly thinking of worst case and the lawyers want to "CYA" as far as warranty claims...
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