AT Down Shifting
06-20-06, 12:18 AM
#18
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Originally Posted by Ramon
Higher revs = more friction. More friction = more wear and tear... You don't need "proof" that is the way things work, simple physics. When you're moving there is energy, when you're slowing down you're transforming that forward motion energy into heat. The wear you save on your brakes by downshifting doens't just disappear, part of it is now being transferred to the transmission/engine. The proof is in the laws of physics.
Weather the additonal wear is of significance or is neglagable is another matter. There are too many variables to give an accurate answer, such as how often you do it, how fast you're going when you do it and how many gears you downshift.
Weather the additonal wear is of significance or is neglagable is another matter. There are too many variables to give an accurate answer, such as how often you do it, how fast you're going when you do it and how many gears you downshift.
However...
I've owned a manual for the past 10 years and downshifting is actually recommended to save the brakes and increase the life of the engine (vs. just letting the engine idle to neutral or almost stall in a high gear).
The thing is that, even though physics are involved, engines nowadays (and especially Honda and Toyota engines) are quite near bullet-proof and you can redline the car all day and it will still probably last past 200K miles. I am reminded of a story I heard about Honda engine testing ..I'm not sure how true it is, but I heard that the engineers stress test the engine in R&D by running it at redline for 48 hours straight...and it still works! Again, it's a "believe it or not" story, but after having owned two Acura's, I'm inclined to agree...those engines are bullet-proof!
The brakes however, will wear down much faster than the engine (though brakes are cheaper), so if you want to "save" your brakes a little, then downshifting can help.
My $.02.
06-20-06, 05:16 AM
#19
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Only on a Lexus forum 
When was the last time any of you blew a motor in a car with less than 150k miles on it? When was the last time any of you even kept a car long enough to put that many miles on it?
Exactly.
When was the last time any of you blew a motor in a car with less than 150k miles on it? When was the last time any of you even kept a car long enough to put that many miles on it?
Exactly.
06-20-06, 05:50 AM
#20
depends how many gears you downshift by, having a 6 speed tranny the gears are close so the revs wont increase that much vs a 5 speed.
Most automatics wont even let you downshift at will without stomping the gas (a nono if you want to brake at this time) so its obvious theres going to be little to no proof for either case. Heck most car drivers wouldnt even know downshifting lets you slow down faster
Most automatics wont even let you downshift at will without stomping the gas (a nono if you want to brake at this time) so its obvious theres going to be little to no proof for either case. Heck most car drivers wouldnt even know downshifting lets you slow down faster
06-20-06, 06:17 AM
#21
Both the engine and tranny are designed to accomodate downshifting just fine. Figure, that when your car is in power mode, it will be downshifting on its own to prepare you for more responsive and quicker acceleration. The tranny won't see the difference, so long as its healthy, and gets its fluid changed on a regular basis. The engine will see a jump in torque/rpm...but if its broken in properly and warm, also in good condition, it will be fine. It would be pretty sad if the brakes stood up to more abuse than the more vital portions of the car, which are usually engineered for tolerance/mistakes. If this wasn't the case, we wouldn't be allowed to downshift, just as a rev-limiter is put in place to prevent an over-rev situation.
The only time I'd really disagree with it, is if one is downshifting to avoid using the brakes. Thats differen't, as brakes are there for a purpose. Otherwise, have at it...and if all else fails, then make use of the warranty.
The only time I'd really disagree with it, is if one is downshifting to avoid using the brakes. Thats differen't, as brakes are there for a purpose. Otherwise, have at it...and if all else fails, then make use of the warranty.
06-20-06, 06:56 AM
#22
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Originally Posted by Shinobi-X
The tranny won't see the difference, so long as its healthy, and gets its fluid changed on a regular basis.
06-20-06, 07:15 AM
#23
Originally Posted by monkeyfarm
The auto trans in the IS doesn't get any scheduled fluid change. It's a sealed unit.
06-20-06, 08:49 AM
#24
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Originally Posted by Flipsonic
To those who have AT, do you downshift to slow down? Is there long term negative effect to the engine if you do this frequently?
I find I do this more frequently in my IS than my other cars. When I get off the freeway or when the car in front of me is getting close, I downshift as long as I know the engine won't rev too high.
I find I do this more frequently in my IS than my other cars. When I get off the freeway or when the car in front of me is getting close, I downshift as long as I know the engine won't rev too high.
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