I know downshifting is not that good for the tranny, and that is better to brake cuz breakes are cheaper. But does the engine NEEDS downshifting from time to time to clean itself or any other purpose?
I been thinking that when you downshift the vacuum created might lube the cylinder walls or the piston rings.
Any ideas or opinions? facts would be better.
but i tought this could be an interesting discussion.


[Modified by GZERO, 2:21 PM 3/1/2003]

 

yeah i'd say it just slows stuff down, until you bring it to proper pms, all the books i've read don't go into detail about downshifting mechanics, though everyone says its better to rev match than to slide it in slow the rpms down and then mash it.

 

yeah, i always do double clutching (don't know if is the same as rev matching) but even if you do that there is going to be a moment when you won't be touching the gas pedal and the engine will find itself having a hugh amount of vacuum.
I was thinking all this because i read that when breaking a new engine you need to do this as well as some hard runs. So my guess would be, our 4 stroke engines need downshifting from time to time. If you think about it, on races you can see the guys downshifting, and if they do it, perhaps there is some technical explanation behind all this.

 

Yeha they're keeping the engine in it's optimal power band so they can accelerate at maximum rate when they exit the corner

 

true, but if downshifting is bad for the engine they wouldn't used it, they could let the clutch pedal in, and when is time to accelerate they would dump the clutch and go on the gas.
I'm talking about more technical level.

 

race car drivers don't care what is good for the motor as long as they win and the motor makes it through. If you dumped the clutch you could loose traction, not good if you are trying to win race.
I drive my cars with lots of downshifting it seems fine for the engines and if you do it smoothly it is fine for the tranny. my.02

 

1) doubleclutching is POINTLESS. its for old cars with transmissions that dont have syncros. so stop doing that ****.

2) downshifting wont hurt the motor, and its not THAT bad for the transmission, only if your going from like 4th to 1st. if you are slowing down and go from 3rd to second, its not that bad.

 

i'm not interested about the tranny, i know trannies are mad with downshifting in mind, and i do a lot of downshifting, but my question is more towards the engine, what does the engine does on downshifting, was i right saying that when the engine is downshifted it creates vacuum that atracts oil from the piston rings?
OK, let me put an example:
Lets say you have to identical engines, with all the variables the same, one is never downshifted and the other one is downshifted a lot.
A) which one would last more? and WHY?
B) will they wear in the same maner?
C) any other info you can add?

 

i have never heard that downshifting one gear hurts the motor so this is all new to me. if its true, i would also like to see some proof or an explanation... interesting topic.

 

NO NO NO! wait, i didn't say it was bad, i been thinking that it might be good to the engine cuz of the vacuum.
But yes, i do want somebody to tell us the real deal.

 

I agree. I do it all the time. It is better than trying to come to a dead stop at 50 miles an hour. Downshift until you can just stop naturally. Yes, it can save on the brakes as well.

 

IMO, downshifting is OK sometimes, but it depends. If you have to slam on the brakes and come to a stop quick just use the brakes becasue thats what you have tyo be concentrating on. On the other hand, if you see that a set of lights or a stop sign is ahead of you then downshift. Doing it then will not put excessive strain on you tranny or motor and it will save your brakes.

 

real race car drivers have sponsors. sponsors mean $$$. and if you've got money, than you just wanna get outta that corner quick, who cares if you need to get a new motor after the race, you've got the money for it.

 

When a race car downshifts during or after a race is it so the brakes wont heat up?
And dont most race cars have very light flywheels and the car would probably die if the revs aint kept up.

I dunno

 

Im a down shifter. if i didnt down shift id go through brake pads once a month

 

the only time i've heard about downshifting being bad for the motor is with turbo. read it in a import mag a few years back. actually it was more damaging to the turbo.

 

Care to elaborate? i would like to hear this.

 

It is all BS! Listen, if you live in some serious hills, You do not want to use your brakes. If you did not downshift and you lived in the mountains that you would eventually fly off a cliff. Truckers always, always downshift when coming down a hill, so does everyone I know in Idaho. They actually teach you to down shift in driving school. If you do not downshift, your brakes will no longer function when they start to boil 1/2 way down a 7% grade and then what? Is thats when you think that you cant afford to down shift? Yes, it does put the extra milage on your motor that you are downshifting instaed of braking but it does nothing to the motor or tranny to make a difference.

 

It will eat up your clutch quicker though

 

even though it's for cars that dont have synchros (back then), it will wear your synchros out faster if you dont double clutch or do the heel and toe (basically the same thing) than just pressing the clutch and sticking it into gear then letting go of the clutch. imo, when RACING, it's not a bad idea, but on streets, why do it? theres no point in going faster on street roads, even when street racing, unless your'e stupid and doing autox on local/residential areas

 

That's a really bad way of putting that....if there really was no point of "going faster" on city roads then I would have bought an automatic Geo Metro instead of an Integra GSR, and keep her in cruise control 90% of the time. I would also have never done any performance mods to any of my cars.


[Modified by Lsos, 11:47 PM 3/2/2003]

 

can we go back into subject?
i wanna hear a technical explanation if is good or if is bad for the engine, i wanna hear facts and theories.
I don't care about the tranny at this moment, i do think downshifting is a necesity, and as someone said, i have many hills in my city, and if you don't downshift you will eat your brake pads like once a month

 

I don't think an engine needs downshifting. The cylinder walls and piston rings are as lubed as they need to be. I doubt any manufacturer would rely on downshifting for proper engine lubrication. That's just crappy engineering. It would blow any engine taken on a long distance trip.

What do you mean by downshifting anyways? Are you talking about engine braking, or downshifting to get more power....or both?

Another thing, they test engines at my old job: they strap them on a dyno and run them at full power for hundreds of hours (the S2000 was the most interesting one...they just kept the thing at 8500rpm wide open for hours and hours at a time. There was technicians, and myself, just standing around the dyno cell listening to the thing ). For those hundreds of hours, there is probably zero time spent at excessive manifold vacuum....that throws out the engine braking being good theory.

 

im confused.....how do nto down shift....if im going say 40, in 4th jsut crusing along, and i need to get aroudn a fairly tight turn, i usualy put int he cluth, put it in neutral, brake, put it in third or second and continue around the bend.


is thay bad....thast how i was tought to drive....doesnt mean tis the right way.

 

Race car drivers don't downshift to help them slow down. That would throw the balance of the car off, and take some cotrol over braking from the driver.