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Join Date: Jun 2003
Location: Phoenix, AZ
Posts: 1,327
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going downhill
My wife's Mazda will accelerate going down the hill to work, with the car in gear and will runup to 50+ with no pressure on the gas pedal.
My car holds about 40 in the same configuration. Is there some magic in here someplace? 
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87 951, K27/6, Almond Beige, 17" Turbotwist 87 944S, alpine white, 5sp died a violent death 84 944, silver/brown, auto, gone but not forgotten "may the force be with you" |
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07-21-2003, 02:46 PM
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vott does ziss do?
Join Date: May 2003
Location: Seattle
Posts: 6,676
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That's simply the engine being able to accelerate the car to whatever speed with the fuel supplied while the pedal is at idle. IOW, the car will increase speed going down a grade by a combination of gravity and engine power. The point at which vehicle reaches that magic speed where it will no longer accelerate is simply the point where more fuel would be required to do so. The reason why the speed stabilizes at that point (in her case 50mph) is because the engine is no longer making enough power to accelerate the car further without requiring more fuel. Since the engine is no longer able to provide additional energy for further acceleration, it also keeps the car from accelerating just as it would when using the engine to brake the car. Result: the vehicle keeps a constant speed.
Does that make sense? 
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07-21-2003, 03:05 PM
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The Mazda has a poor compression to gear ratio.
Low mechanical resistance. Tires, width and pressure, also have a lot to do with it.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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07-21-2003, 03:21 PM
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Location: Phoenix, AZ
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Thanks.
I just remembered her car is in overdrive unless it's toggled out going up a hill.
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87 951, K27/6, Almond Beige, 17" Turbotwist 87 944S, alpine white, 5sp died a violent death 84 944, silver/brown, auto, gone but not forgotten "may the force be with you" |
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07-21-2003, 04:43 PM
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Join Date: Jul 2003
Location: eugene, or
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That has got to be great on the trannie...
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78 924 74 Karmen Ghia (probally) 96 Gary Fisher Aluminum |
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07-21-2003, 08:18 PM
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Join Date: Jun 2003
Location: Phoenix, AZ
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downshifting on the uphill to keep the turns up is better than lugging the engine going slow.
we have to negotiate some downhills and sometimes kill the tranny even more by using 2nd gear, to stay off the brakes got the mazda new in '98 and it hasn't been a problem. i appreciate your input.
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87 951, K27/6, Almond Beige, 17" Turbotwist 87 944S, alpine white, 5sp died a violent death 84 944, silver/brown, auto, gone but not forgotten "may the force be with you" |
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07-21-2003, 09:49 PM
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1983 Porsche 944 2.5 liter
