View Poll Results: Do you downshift your MT?
Voters: 184. You may not vote on this poll
Do you downshift your MT?
#31
12-07-2006, 06:47 PM
#32
12-07-2006, 08:19 PM
I got tired of reading it all, but basically rev matching to downshift pretty much takes purpose out of downshifting to slow down, and ultimately makes no sense to me at all, unless I'm downshifting to accelerate.
How does downshift cause strain on the engine? I can tell you how..
The RPMs go from 3,000 to 5,000 instantly... What does that mean for the engine that's designed to readline at 7500RPM, absolutely nothing, point is? .. Oh, it doesn't do anything wrong to the engine. Pressure some say on the rings, yes provided your car was equipt with a special JBWELD bung or something in place of the PCV valve, but most cars (aka all cars) aren't .. Your PCV stands for Possitive crankcase ventelation, by the way.. This means if there's too much pressure in the crank it will blow out of the crank and valves to the intake, this is why some, like myself, may have oil in the air intake. Is it bad ? No, it's how the car was designed to function. Would it cause a person to go 5 quarts low on oil after 3,000 miles? No..
What would cause the burning of 5 quarts of oil would be the rings being worn improperly, or the cross hatching on the cylinder walls being glazed. These are two examples that actually plague people that DONT downshift enough when they get their cars, or who DO rev match when the downshift. Your engine needs that pressure during break-in to allow the rings to seat properly. It can all be debated until we're blue in the face, much like the Amsoil vs. Mobil1 synthetic that goes on on 90% of the motorcycle forums.
The fact is, if you've driven a car for over 200,000 miles and downshifted all the time without worry of "rev matching" then odds are it's not causing any problems.
As for skipping gears... I've heard rumors of this causing problems with the syncros.
If you want to worry about breaking your trans and find out what not to do it's simply.. Just don't use it as an arm/hand rest while you drive and just get a good feel for your car. Your spine will tingle when you do something wrong .. At least mine does.. Get in tune with the car and understand what the car you own needs to do by listening to the engine, feeling out the clutch, and getting a better feel for that gas clutch relationship.
And now you know the rest of the story.
-fact, there is no concrete evidence for anything I"ve stated tonight, it's mostly pulled directly out of my a$$, but I believe it ..
anyone who doesn't is just plain dumb.
How does downshift cause strain on the engine? I can tell you how..
The RPMs go from 3,000 to 5,000 instantly... What does that mean for the engine that's designed to readline at 7500RPM, absolutely nothing, point is? .. Oh, it doesn't do anything wrong to the engine. Pressure some say on the rings, yes provided your car was equipt with a special JBWELD bung or something in place of the PCV valve, but most cars (aka all cars) aren't .. Your PCV stands for Possitive crankcase ventelation, by the way.. This means if there's too much pressure in the crank it will blow out of the crank and valves to the intake, this is why some, like myself, may have oil in the air intake. Is it bad ? No, it's how the car was designed to function. Would it cause a person to go 5 quarts low on oil after 3,000 miles? No..
What would cause the burning of 5 quarts of oil would be the rings being worn improperly, or the cross hatching on the cylinder walls being glazed. These are two examples that actually plague people that DONT downshift enough when they get their cars, or who DO rev match when the downshift. Your engine needs that pressure during break-in to allow the rings to seat properly. It can all be debated until we're blue in the face, much like the Amsoil vs. Mobil1 synthetic that goes on on 90% of the motorcycle forums.
The fact is, if you've driven a car for over 200,000 miles and downshifted all the time without worry of "rev matching" then odds are it's not causing any problems.
As for skipping gears... I've heard rumors of this causing problems with the syncros.
If you want to worry about breaking your trans and find out what not to do it's simply.. Just don't use it as an arm/hand rest while you drive and just get a good feel for your car. Your spine will tingle when you do something wrong .. At least mine does.. Get in tune with the car and understand what the car you own needs to do by listening to the engine, feeling out the clutch, and getting a better feel for that gas clutch relationship.
And now you know the rest of the story.
-fact, there is no concrete evidence for anything I"ve stated tonight, it's mostly pulled directly out of my a$$, but I believe it ..
anyone who doesn't is just plain dumb.
#33
12-07-2006, 08:26 PM
Originally Posted by obender66
New brake pads $80
New transmission-few grand
Blowing your engine after you overreved it downshifting-priceless....
New transmission-few grand
Blowing your engine after you overreved it downshifting-priceless....
if you're even stupid enough to over rev your engine, then don't down shift period... downshifting a car requires that you normal or average level skill and an IQ of a chimp. If you have no common sense whatsoever, don't even try it... It's people like you who crash into a wall racing your brand new G agasint a hyndai and then posting it on this forum crying about it.
with that said, if you're a stupid momo litte kid who parents bought you your G and have no experience in driving, then don't do anything stupid...
a brakepad is cheaper then a new clutch...
for everyone else who knows how to drive, and has the common knowlege NOT to downshift if ur already reving at 4-5k.... then you'll do just fine.
If you can't drive for jack shlt, and ur dumbazz downshifted from 6 to 1st, then you my friend should take public transportation.. Do us and everyone who knows how to drive a favor and just stay home. Post all day on this forum if you want, just dont drive at all.
#34
12-07-2006, 08:31 PM
Originally Posted by cnaman
If you can't drive for jack shlt, and ur dumbazz downshifted from 6 to 1st, then you my friend should take public transportation.. Do us and everyone who knows how to drive a favor and just stay home. Post all day on this forum if you want, just dont drive at all.
#35
12-07-2006, 10:25 PM
#36
12-07-2006, 10:48 PM
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Originally Posted by MightyMouse
I got tired of reading it all, but basically rev matching to downshift pretty much takes purpose out of downshifting to slow down, and ultimately makes no sense to me at all, unless I'm downshifting to accelerate.
How does downshift cause strain on the engine? I can tell you how..
The RPMs go from 3,000 to 5,000 instantly... What does that mean for the engine that's designed to readline at 7500RPM, absolutely nothing, point is? .. Oh, it doesn't do anything wrong to the engine. Pressure some say on the rings, yes provided your car was equipt with a special JBWELD bung or something in place of the PCV valve, but most cars (aka all cars) aren't .. Your PCV stands for Possitive crankcase ventelation, by the way.. This means if there's too much pressure in the crank it will blow out of the crank and valves to the intake, this is why some, like myself, may have oil in the air intake. Is it bad ? No, it's how the car was designed to function. Would it cause a person to go 5 quarts low on oil after 3,000 miles? No..
What would cause the burning of 5 quarts of oil would be the rings being worn improperly, or the cross hatching on the cylinder walls being glazed. These are two examples that actually plague people that DONT downshift enough when they get their cars, or who DO rev match when the downshift. Your engine needs that pressure during break-in to allow the rings to seat properly. It can all be debated until we're blue in the face, much like the Amsoil vs. Mobil1 synthetic that goes on on 90% of the motorcycle forums.
The fact is, if you've driven a car for over 200,000 miles and downshifted all the time without worry of "rev matching" then odds are it's not causing any problems.
As for skipping gears... I've heard rumors of this causing problems with the syncros.
If you want to worry about breaking your trans and find out what not to do it's simply.. Just don't use it as an arm/hand rest while you drive and just get a good feel for your car. Your spine will tingle when you do something wrong .. At least mine does.. Get in tune with the car and understand what the car you own needs to do by listening to the engine, feeling out the clutch, and getting a better feel for that gas clutch relationship.
And now you know the rest of the story.
-fact, there is no concrete evidence for anything I"ve stated tonight, it's mostly pulled directly out of my a$$, but I believe it ..
anyone who doesn't is just plain dumb.
How does downshift cause strain on the engine? I can tell you how..
The RPMs go from 3,000 to 5,000 instantly... What does that mean for the engine that's designed to readline at 7500RPM, absolutely nothing, point is? .. Oh, it doesn't do anything wrong to the engine. Pressure some say on the rings, yes provided your car was equipt with a special JBWELD bung or something in place of the PCV valve, but most cars (aka all cars) aren't .. Your PCV stands for Possitive crankcase ventelation, by the way.. This means if there's too much pressure in the crank it will blow out of the crank and valves to the intake, this is why some, like myself, may have oil in the air intake. Is it bad ? No, it's how the car was designed to function. Would it cause a person to go 5 quarts low on oil after 3,000 miles? No..
What would cause the burning of 5 quarts of oil would be the rings being worn improperly, or the cross hatching on the cylinder walls being glazed. These are two examples that actually plague people that DONT downshift enough when they get their cars, or who DO rev match when the downshift. Your engine needs that pressure during break-in to allow the rings to seat properly. It can all be debated until we're blue in the face, much like the Amsoil vs. Mobil1 synthetic that goes on on 90% of the motorcycle forums.
The fact is, if you've driven a car for over 200,000 miles and downshifted all the time without worry of "rev matching" then odds are it's not causing any problems.
As for skipping gears... I've heard rumors of this causing problems with the syncros.
If you want to worry about breaking your trans and find out what not to do it's simply.. Just don't use it as an arm/hand rest while you drive and just get a good feel for your car. Your spine will tingle when you do something wrong .. At least mine does.. Get in tune with the car and understand what the car you own needs to do by listening to the engine, feeling out the clutch, and getting a better feel for that gas clutch relationship.
And now you know the rest of the story.
-fact, there is no concrete evidence for anything I"ve stated tonight, it's mostly pulled directly out of my a$$, but I believe it ..
anyone who doesn't is just plain dumb.
Case closed
#37
12-08-2006, 02:02 AM
downshifting is good when u are in the process of breaking in an engine. its allows the rings to expand and create a good seal between the sleeves.
when u downshift it creates a vacuum and helps break in the motor correctly..
i was told this by a tuner/builder/drag racer who just rebuilt my integra LS motor...
when u downshift it creates a vacuum and helps break in the motor correctly..
i was told this by a tuner/builder/drag racer who just rebuilt my integra LS motor...
#39
12-08-2006, 08:24 PM
Oh geez, and you deducted all that from my 3 line post?
Ever heard of such thing as "sense of humour"?
I did not make any serious statements, so why don't you **** off?
Ever heard of such thing as "sense of humour"?
I did not make any serious statements, so why don't you **** off?
Originally Posted by cnaman
if you downshift while at 5k or more then ur a dumbass and should be allowed to drive any car over 30k.
if you're even stupid enough to over rev your engine, then don't down shift period... downshifting a car requires that you normal or average level skill and an IQ of a chimp. If you have no common sense whatsoever, don't even try it... It's people like you who crash into a wall racing your brand new G agasint a hyndai and then posting it on this forum crying about it.
with that said, if you're a stupid momo litte kid who parents bought you your G and have no experience in driving, then don't do anything stupid...
a brakepad is cheaper then a new clutch...
for everyone else who knows how to drive, and has the common knowlege NOT to downshift if ur already reving at 4-5k.... then you'll do just fine.
If you can't drive for jack shlt, and ur dumbazz downshifted from 6 to 1st, then you my friend should take public transportation.. Do us and everyone who knows how to drive a favor and just stay home. Post all day on this forum if you want, just dont drive at all.
if you're even stupid enough to over rev your engine, then don't down shift period... downshifting a car requires that you normal or average level skill and an IQ of a chimp. If you have no common sense whatsoever, don't even try it... It's people like you who crash into a wall racing your brand new G agasint a hyndai and then posting it on this forum crying about it.
with that said, if you're a stupid momo litte kid who parents bought you your G and have no experience in driving, then don't do anything stupid...
a brakepad is cheaper then a new clutch...
for everyone else who knows how to drive, and has the common knowlege NOT to downshift if ur already reving at 4-5k.... then you'll do just fine.
If you can't drive for jack shlt, and ur dumbazz downshifted from 6 to 1st, then you my friend should take public transportation.. Do us and everyone who knows how to drive a favor and just stay home. Post all day on this forum if you want, just dont drive at all.
#40
12-09-2006, 12:56 PM
Just How I Figured It....
I was the one who originally started this discussion in the Check Your Oil thread by commenting on the folly of downshifting for the purposes of deceleration.
After reading the responses so far, IMO this thread will be of use to Nissan engineers who are trying to figure out why it is that their previously bulletproof VQ is being brought to its knees when installed in G35s with manual transmissions. There still could be something wrong with the design, but to me it's looking more like a case of "the loose nut behind the steering wheel."
My theory is that the unusually high manifold vacuum created in a typical engine braking scenario is pulling oil past the valve stem seals and into the combustion chamber. This is how you can have oil consumption without ring wear, without excessive blowby, or without compression loss.
And unlike ALL who have posted so far, allow me to supply a little bit of a source for the facts supporting my theory from the Wikipedia entry on "manifold vacuum:"
So, the more often and the more aggressively you engine brake, the more oil you could be pulling past the valve guide seals.
And if you think about it and realize that with the 5AT, as with almost all automatics, there is very little engine braking. Could this explain why there is no apparent oil consumption problem on the 5AT cars?
After reading the responses so far, IMO this thread will be of use to Nissan engineers who are trying to figure out why it is that their previously bulletproof VQ is being brought to its knees when installed in G35s with manual transmissions. There still could be something wrong with the design, but to me it's looking more like a case of "the loose nut behind the steering wheel."
My theory is that the unusually high manifold vacuum created in a typical engine braking scenario is pulling oil past the valve stem seals and into the combustion chamber. This is how you can have oil consumption without ring wear, without excessive blowby, or without compression loss.
And unlike ALL who have posted so far, allow me to supply a little bit of a source for the facts supporting my theory from the Wikipedia entry on "manifold vacuum:"
Vacuum is created in some situations. On deceleration or when descending a hill, the throttle will be closed and a low gear selected to control speed. The engine will be rotating fast due to the fact that the road wheels and transmission are moving quickly, but the butterfly valve will be fully closed. The flow of air through the engine is strongly restricted by the throttle, producing a strong vacuum on the engine side of the butterfly valve which will tend to limit the speed of the engine. This phenomenon, known as compression braking, is often used in engine braking to prevent acceleration or even to slow down with minimal or no brake usage (as when descending a long or steep hill). Note that although "compression braking" and "engine braking" are sometimes used to describe the same thing, "compression braking" here refers to the phenomenon itself while "engine braking" refers to the driver's usage of the phenomenon. Compression braking can be greatly increased by closing the exhaust with a valve on the over-run, which is often done on large trucks.
Also, see #13 and #24 on this Amsoil page: http://www.smartsynthetics.com/motor...onsumption.htmSo, the more often and the more aggressively you engine brake, the more oil you could be pulling past the valve guide seals.
And if you think about it and realize that with the 5AT, as with almost all automatics, there is very little engine braking. Could this explain why there is no apparent oil consumption problem on the 5AT cars?
Last edited by gwhiz35; 12-09-2006 at 01:00 PM.
#41
12-09-2006, 01:20 PM
The choices on this poll are too limiting and don't make a lot of sense. How could anyone drive a car on the street without downshifting it whether it is an MT or AT? To do this the car would have to stay in whatever top gear it got up to until a stop despite a variety of speeds in normal city driving.
As others have said driving an MT requires a good feel for the engine, clutch and shifter so you're feeling at one with the car and in a safe driving mode and rpm range. Downshifting is part of normal driving, as is some amount compression braking on hills or slight braking, and regular rev matching. Doing any of this in excess or at higher ends of the rev/braking range will cause unnecessary wear to some part of the drivetrain.
As others have said driving an MT requires a good feel for the engine, clutch and shifter so you're feeling at one with the car and in a safe driving mode and rpm range. Downshifting is part of normal driving, as is some amount compression braking on hills or slight braking, and regular rev matching. Doing any of this in excess or at higher ends of the rev/braking range will cause unnecessary wear to some part of the drivetrain.
#43
03-25-2008, 05:50 PM
Originally Posted by stpdevil
Yes... for the exact reason you just cited. They explained on top gear that then you idle you are using a tiny bit of gas, but when you are slowing down in gear your wheels are turning the engine and no gas is needed to keep the engine running. This could be completely wrong, but thats how they said it worked on the show. Overall I don't think it makes a huge difference, but they were talking about it on the episode where they were trying to squeeze 40mpg out of a big Audi with a tt diesel v8.
i do not down shift to stop cuz thats what the brakes are desginedfor, not the motor and tranny,
however, if i was on the track or plan on zipping out the the turn ill downshift so im already in gear.
#44
03-25-2008, 08:47 PM
Originally Posted by nghiars
Originally Posted by stpdevil
Yes... for the exact reason you just cited. They explained on top gear that then you idle you are using a tiny bit of gas, but when you are slowing down in gear your wheels are turning the engine and no gas is needed to keep the engine running. This could be completely wrong, but thats how they said it worked on the show. Overall I don't think it makes a huge difference, but they were talking about it on the episode where they were trying to squeeze 40mpg out of a big Audi with a tt diesel v8.
#45
03-25-2008, 09:24 PM
