mazdaspeedwest

I was thinking about this today, and thought there might be a difference in up shifting and downshifting according to the clutch use.

So question is, how does downshifting affect the clutch and engine? and is there a difference is clutch engagement between up and down shifting?.....and i'm talking technical here, not the obvious "engine braking"

all in reference to a 5sp transmission.........

islandpro

i think your putting way to much thought into it. I see it as the forces that are put to the clutch when upshifting are then reversed when down shifting. insted of the engine providing the power the trany is. heck i dunno. im confused now.. time to take a nap.

islandpro

IMO i think the clutch goes threw the same. no matter up or downshifting.

zenilder

Well, there's not too much to it. Just so long as you rev match when you downshift, things should be okay.

Upshifting, if you're mashing the pedal, and then shift without letting off the gas, you could run the risk of overheating the clutch with one launch. The disc would slip until the engine slowed down to match the tranny, creating heat. Stock disks will start to slip pretty fast, and then you're left to feather the throttle to gain speed.
Letting out the clutch too quickly will give a jolt to the disc, but the stock discs have a spring loaded plate. So that absorbs a lot of the punishment.

Oh. If your clutch does overheat, and it slips too much, you risk glazing your clutch and possibly warping your flywheel.

The same principles apply to downshifting. If you don't rev match, you're just heating up your clutch, and eventually it'll start to slip.
Letting out the clutch too fast with out rev matching, forces one end to match speeds of the other, and in this case, it's usually the engine that has to match the speed of the car/tranny, which isn't good on the engine (and this doesn't apply to engine braking when the engine is forced to slow down to slow the car. I'm talking about sudden need to slow down). Like I said, the springs on the stock disc absorbs a lot of the punishment, but that doesn't mean that nothing else will be affected by harsh use.

islandpro

told you i didnt know. but thought i would give it a shot.

Maz94Protege

??? REV MATCH....huh??? you dont ( or not supposed to rev to down shift)

if thats what ur refering to,....i think ur shifting wrong.

mazdaspeedwest

thanks, i understand, but i don't or haven't much, rev matched when downshifting, i downshift for engine braking...but i am still on the OEM clutch and yes it does slip nicely in 2nd now...but after 12 years, it's been a great clutch.

mazdaspeedwest

rev matching is more of a racing technique. also refered to as heel-toe.

when you enter a corner under braking (heel on the brake pedal) you rev (toe on the gas pedal) the engine to match the downshifted gear's RPM, this way you'll be in the power band when exiting the corner and the car will not slow down due to engine braking, but rather spit you out of the corner faster.

very dificult to do correctly i might add, takes alot of practice.

Maz94Protege

oooo aight gotcha...thanks for the clearing up!

Sir Nuke

I really don't see where there is a problem with this at all....can't see where it does any harm.... I have over 135K on my little truck...and the clutch don't slip a bit...and I use the engine to break ALL the time....its how I drive.

zenilder

I'm not saying that any of this does any harm. At the worst, the springs on the clutch disc will wear out, glaze the clutch and possibly warp the flywheel. I certainly don't mean any of this will be the result of light engine breaking while going to the market to pick up a six pack of Henry Weinhards Root Beer with some chips & dip to watch a movie at home. I'm say you might see these problems if you tend to do it often enough to see your clutch slipping after a couple of launches or a few dozen turns. The springs on the clutch should be fine unless you really punish them by letting the clutch out quickly ( and I don't mean doing it on stoplight drags or anything. I mean when you're driving on the street, you're in 2nd, you're about to shift up to 3rd, rev is about 3500, you shift to 3rd, but you don't let the revs drop much at all, and when you let the clutch out real quick *JERK*). I don't like doing that, and I try to stay away from doing it. Especially in my truck, considering that it has monster torque, and doing that will eventually break something in the drivetrain.

So don't stress it if you do your normal daily driving. If you push your car hard everyday, then you might worry about it.

mazdaspeedwest

no problemo

turboge

Hmm... I usually use my toe portion on the brake pedal and stab the bottom of the gas pedal with my heal. I couldn't see my feet turning the other way to put the toe on the gas pedal, and the heel on the brakes.. contortion!?

Brubeck

Yes, and I do the same. I put 125k on my Toyota pick-up... engine break as much as possible and never replaced a break pad... never had a clutch problem.

If you doubt that engine breaking works, make a point to get close to an 18-wheeler in traffic. When things start slowing down and you hear rhhhhhaaaaaaaaarrrrrrr gaaaaaa gaaagg ggaaa gaa ga gaaahhhhhhh..... you'll realize that people who drive all goddamn day long know that engine breaking is a fact of life.

mazdaspeedwest

i guess it's just natural for me, and you get more pressure on the brake with your heel than your toe