Reving engine with clutch in

[bowman316]

Does it hurt the clutch to hit the gas with the clutch in?
when I am down shifting, I will put the clutch in, shift the the right gear, and with the clutch still in, give a lil gas to rev match, then let out the clutch.

does this hurt anything, should i double clutch, by stopping in netural, then gas it?

 

[MikDee]

Re: Reving engine with clutch in

On a boat? Nah, you should be able to speed shift it, you might get some cavitation though,,,

Seriously though, No, no damage done, the clutch plate is disengaged from the driveline, until you release the pedal, then you'll get some excess wear on the clutch plate from high rpm friction.
No, no double clutching unless you're driving a Big Rig, and it grinds going into gear when single clutching because of the extra load on the vehicle.
I hope this answers your question?

 

[bowman316]

Re: Reving engine with clutch in

yea, you can rev all you want with the clutch in right?
just like being in neutral

 

[MikDee]

Re: Reving engine with clutch in

Your engine may not like it too much, but yeah!

 

[Bob_VT]

Re: Reving engine with clutch in

Some of the newer cars will not permit revving the engine. The ecu will limit the rev. It really is not a good practice. If you have a hydraulic clutch and the line breaks or the cylinder seal goes..... if you have a cable assembly that snaps...... we are talking possible disaster.

 

[TilliamWe]

Re: Reving engine with clutch in

yea, you can rev all you want with the clutch in right?
just like being in neutral

No, not exactly. I am not expert, but I believe that with the clutch pedel depressed, you are putting wear on the Throw Out Bearing. (or is it the Pilot bearing?) All things equal, the best place for the clutch to be is engaged (clutch pedal up) and the transmission in neutral. That way the wear is at a minimum.

Next, revving the motor with the clutch depressed is doing nothing helpful as far as downshifting. In a fully syncronized transmission, it just isn't necessary. And you are NOT matching the transmission and engine revolutions with the clutch pedal depressed. It's an input shaft thing (again, not an expert to explain it).

But if you want to pretend that you are driving a big rig, without a synchronized trans, the correct proceed for a down shift is:
Let off throttle, depress clutch, move shift lever into neutral, release clutch pedal, press throttle to just above rpms needed, depress clutch pedal, move shift lever into next lower gear, release clutch pedal.

Now you see why they invented fully synchronized transmissions?

 

[sportsmanphil]

Re: Reving engine with clutch in

Just for explination purpose: the trans has a shaft sticking out the front. It pokes into the flywheel of the engine by way of a pilot bearing/bushing. this just keeps it centered and supported. The throwout bearing is what presses the clutch but yet allows it to spin on a bearing surface.

Reving the engine with the clutch in will not hurt anything, unless you get stupid with it and float a lifter (if your engine has lifters, never told us what kind of car we are talking about here)

When it comes to down shifting, there is no reason to match the engine RPM with the pressure plate of the clutch when stopping. If you are downshifting to pass or just drive at a slower speed, matching speeds is more suited.

However I do not reccomend downshifting to assist in stopping at all unless you are in an emergency situation and needing to add stopping power. Why? because brake replacement is much cheaper than clutch replacement. No reason to add ware to a clutch if not needed.

 

[slasmith1]

Re: Reving engine with clutch in

However I do not reccomend downshifting to assist in stopping at all unless you are in an emergency situation and needing to add stopping power. Why? because brake replacement is much cheaper than clutch replacement. No reason to add ware to a clutch if not needed.

you obviously have never experienced brake fade on a steep grade. the rule is you use the same gear going down the hill that you need going up it. in a small car it is no big deal but if you are towing or hauling a load that is close to it's max capacity this is a rule to live by.

 

[sportsmanphil]

Re: Reving engine with clutch in

you obviously have never experienced brake fade on a steep grade. the rule is you use the same gear going down the hill that you need going up it. in a small car it is no big deal but if you are towing or hauling a load that is close to it's max capacity this is a rule to live by.

I have experienced brake fade, from tugging a 34' camper through the WV mountains (following behind some 70 year old Q-tip in a smoke screen producing Caddy Braham) to a C5 Vette on the VIR circuit.

Your scenario would fit somewhere between my comments "emergency situation" and "downshifting for lower speeds"

 

[bowman316]

Re: Reving engine with clutch in

I'm driving a 2007 ford ranger, with the 4.0 l engine. 5 speed.
When down shifting, (only when towing my boat, and even then, not that much to minimize clutch ware)
I will need to raise the rpms by about 1,000 to rev match. Otherwise the truck will kinda jerk, and the rpms will raise rapidly.

I think rev matching by hitting the gas with the clutch in is much better than having the rpm's jump like that.

my trailer weights about 3,000 lbs.
it is a hydrolic clutch

 

[sportsmanphil]

Re: Reving engine with clutch in

i'd say you are letting the clutch out too fast on the down shift.

The larger your engine (4.0 in your case) will come with heavier clutches and the larger engine will show its negative side effects more than a light engine/clutch combo.

 

[kkr26]

Re: Reving engine with clutch in

Put in neutral.

 

[TilliamWe]

Re: Reving engine with clutch in

When down shifting, (only when towing my boat, and even then, not that much to minimize clutch ware)
I will need to raise the rpms by about 1,000 to rev match. Otherwise the truck will kinda jerk, and the rpms will raise rapidly.

It is possible that you are downshifting too soon. Apply the brakes a little longer. But in any case, you aren't really helping yourself by revving it with the clutch still depressed. All you are doing is making yourself feel better. As far as the revs climbing fast, that's normal.

 

[bowman316]

Re: Reving engine with clutch in

my general rule of thumb is anything that makes the truck jerk or feels un natural is wearing the clutch, anything that feels smooth is not hurting it.

 

[QC]

Re: Reving engine with clutch in

That is correct . . . ^^^ Guys he is talking about rev matching, not revving for fun. With our without synchros this is easier on the entire driveline. This assumes he would've made the shift anyway, but if he is going to downshift for more power uphill, or for braking downhill, matching engine speed to trans speed is a good thing. There is no additional clutch wear here, in fact there is less when the speeds are matched as there is no slip or friction to eat up the clutch. Saves on u-joints and all other wear surfaces from the clutch to the driven wheels. It could even be argued it is easier on tires. Minimal, but definitely not bad. Better yet is to skip using the clutch for shifts completely. Gotta be good though or things get worse fast

 

[bowman316]

Re: Reving engine with clutch in

Better yet is to skip using the clutch for shifts completely. Gotta be good though

You talking about shifting without the clutch at all?

 

[QC]

Re: Reving engine with clutch in

Yes. But learn on somebody else's stuff

 

[sportsmanphil]

Re: Reving engine with clutch in

You talking about shifting without the clutch at all?

Leave bang shifting to the pros,,,,,,,,,,unless you like sweeping up bits and pieces of gears!

 

[QC]

Re: Reving engine with clutch in

Agree ^^^^, I was just pointing out that done properly, that would result in the least wear for all components involved. Modern stuff is pretty good though, with the exception of the disc itself I would not expect any of these driveline components to ever wear out unless they were literally abused.

 

[waterinthefuel]

Re: Reving engine with clutch in

Why would you downshift like that? I have a standard, and I never did that. If I needed to go down to a lower gear I put the truck in neautral, let it slow down on its own, and then put it into that gear and just feel while letting the clutch out what the truck was doing. If it was trying to slow down, I gave it a bit of gas, but I never "revved" it. I know what speeds my truck needs what gears. You don't know that for your truck? I can tell you within a MPH what speed I would shift into what gear. If your truck is revving that much when you go into a lower gear maybe you are choosing too low of a gear or not waiting long enough to put it into gear.

I don't know about whether you hurt it or not, but you are wearing out the throw out bearing by doing what you're doing. It's up to you. Just remember, there is a brake pedal on the floor to slow the vehicle, the clutch wasn't designed to do that.