Preserving clutch and gas mileage

[Zenmervolt]

Originally posted by: MisterMe

Originally posted by: Zenmervolt

Originally posted by: MisterMe
What I saying is in efforts to "save your car" you might avoid engine breaking an coast to stops. Doing this avoids the rpm spikes and save you gas.

No, it does not. It uses more gas to coast. I went over that in my last post. All modern electronic fuel injection systems detect engine braking and turn off the injectors down to a specified RPM cutoff (typically 100-200 RPM above idle) at which point idle-level fuel-flow is restored. This means that exactly zero fuel is used during engine braking (until the threshold RPM is reached, at which point only idle levels of fuel are consumed), whereas coasting down uses an idle-level of fuel during the entire slowdown period as opposed to just at the end.

So if this kid is trying to save his car to the utmost extent, which way would you tell him to avoid the most wear and tear over the lifespan of a clutch/engine?

See my post above.

This doesn't change the fact that you're wrong about engine braking wasting fuel though.

ZV

 

[TheLonelyPhoenix]

Originally posted by: Zenmervolt

Originally posted by: TheLonelyPhoenix
Okay, so what kind of techniques should I be using now in the interests of not wearing down my clutch or burning up too much gas, and what should I learn about for future reference once I'm proficient at normal shifting?

And last I checked, replacing a front wheel drive clutch was about $800+, so I do believe its a good component to economize.

The fuel consumption amount is academic. While you technically save fuel by engine braking, it's not enough to make any measurable difference in the real world. Remember that an idling engine burns something like 1 gallon of fuel every two hours. So if your engine is idling and you're coasting at 60mph, you're effectively getting 120 mpg at that instant. It's not enough to worry about.

As for techniques:

Keep your foot off the clutch unless you want it completely disengaged. Unless you are changing gears or sitting in neutral/starting off you should never rest your foot on the clutch pedal.

When shifting, press the clutch pedal to the floor and move the leave smoothly to the next gate. Do not try to rush things, just make it smooth for now. Speed will come later on its own. Be sure to engage and disengage the clutch smoothly too, again, speed will come in time on its own.

Honestly, there is nothing that you need to learn beyond normal shifting. Double-clutching is kinda fun, but it increases wear on the clutch, and it's purely un-necessary as long as you're not a race driver.

I stand by my recommendation to leave the car in gear when braking until 1,000 RPM (or slightly higher), then going to neutral and completing the stop. That doesn't wear the clutch because you're not shifting and it does capture some benefit of engine braking.

ZV

So double-clutching INCREASES wear on the clutch?
Whaaa?

What kind of clutch engage/disengage speeds should I be looking to achieve? I'm not trying to rush things, but I'd like an idea of what I should be shooting for, just so I don't get too comfortable with bad habits.

Also, when making a turn, should I coast thru with the clutch pedal down and use the brake to manage speed, then downshift after the turn and speed back up? Or is it better to downshift beforehand and go through the turn with the clutch engaged?

 

[duke]

Silly question...I drive a manual, but it doesn't have a tach. Is it a good idea to rev match by ear?

 

[Zenmervolt]

Originally posted by: TheLonelyPhoenix
So double-clutching INCREASES wear on the clutch?
Whaaa?

What kind of clutch engage/disengage speeds should I be looking to achieve? I'm not trying to rush things, but I'd like an idea of what I should be shooting for, just so I don't get too comfortable with bad habits.

Also, when making a turn, should I coast thru with the clutch pedal down and use the brake to manage speed, then downshift after the turn and speed back up? Or is it better to downshift beforehand and go through the turn with the clutch engaged?

Double-clutching cycles the clutch twice instead of once. Of course it increases wear on the clutch. It was used to increase smoothness of gearchanges before the advent of full synchromesh gearboxes. Almost all automotive gearboxes since the 1970's are full synchromesh and hence do not require double-clutching. Any automotive gearbox since the 1980's will certainly be full synchromesh.

As I said before, don't worry about speed, worry about smoothness. Smoothness is far more important to clutch life than speed.

It is always best to keep the clutch engaged and the car in gear as much as possible, it gives you more options for control. If you suddenly engage the clutch when you're trying to go through a corner with the clutch disengaged you can really surprise yourself and upset the car. Downshift before the corner, go through with the clutch engaged.

ZV

 

[Zenmervolt]

Originally posted by: duke
Silly question...I drive a manual, but it doesn't have a tach. Is it a good idea to rev match by ear?

A tach is useless for rev-matching. In order for it to be useful, you'd need three tachs, one to measure engine RPM, one to measure input shaft RPM, and one to measure output shaft RPM.

Rev-matching is always done by feel, at least it is for me.

ZV

 

[MisterMe]

So double-clutching INCREASES wear on the clutch?
Whaaa?

What kind of clutch engage/disengage speeds should I be looking to achieve? I'm not trying to rush things, but I'd like an idea of what I should be shooting for, just so I don't get too comfortable with bad habits.

Also, when making a turn, should I coast thru with the clutch pedal down and use the brake to manage speed, then downshift after the turn and speed back up? Or is it better to downshift beforehand and go through the turn with the clutch engaged?

Sure, "double" clutching would add wear to a clutch. I'm not sure why you would need to double clutch anything but every time you step on the clutch pedal, the clutch gets worn an additional amount. So by the terms of the phrase, double clutching would add an extra cycle and therefore another minute amount of wear...

Just concentrate on being smooth. Try to match rpms to whatever speed you are going. This can only come with experience. Say if you're cruising at 60 and need to drop a gear for passing or whatever, try to increase the rpms a bit when engaging the clutch back in. The closer the rpms are to what the road speed would dictate will effectively reduce the wear on the clutch...

I'd say about turning is that your focus should be remaining smooth. If you're heading around a corner and have already selected the gear with which you will be accellerating out with then leave the clutch engaged. If you're not trying to be hurried then coast around the corner with your foot hovered over the brake to anticipate anything that may come up. Here again it's all experience and you will work out your driving style over time...

ZV - whatever dude about the fuel thing. The way I see it is if this guy is looking to have the least impact on his new drivetrain then avoiding things like engine breaking would only make sense...

 

[duke]

Originally posted by: Zenmervolt

Originally posted by: duke
Silly question...I drive a manual, but it doesn't have a tach. Is it a good idea to rev match by ear?

A tach is useless for rev-matching. In order for it to be useful, you'd need three tachs, one to measure engine RPM, one to measure input shaft RPM, and one to measure output shaft RPM.

Rev-matching is always done by feel, at least it is for me.

ZV

Can you explain a little bit further, mechanically, what you mean "by feel"? Do you have all three tachs?

 

[Zenmervolt]

Originally posted by: MisterMe
ZV - whatever dude about the fuel thing. The way I see it is if this guy is looking to have the least impact on his new drivetrain then avoiding things like engine breaking would only make sense...

Look, I was just trying to counter that bit of mistaken information you were given by whomever spread it to you. I agree with you in practical applications.

ZV

 

[Eli]

In my opinion, engine braking couldn't possibly add any more wear to the drivetrain than acceleration and/or startoffs.

 

[Zenmervolt]

Originally posted by: duke

Originally posted by: Zenmervolt

Originally posted by: duke
Silly question...I drive a manual, but it doesn't have a tach. Is it a good idea to rev match by ear?

A tach is useless for rev-matching. In order for it to be useful, you'd need three tachs, one to measure engine RPM, one to measure input shaft RPM, and one to measure output shaft RPM.

Rev-matching is always done by feel, at least it is for me.

ZV

Can you explain a little bit further, mechanically, what you mean "by feel"? Do you have all three tachs?

No, nobody in their right mind would have all three tachs, information overload.

There are two kinds of rev-matching. One involves matching engine RPM to transmission input shaft RPM to smooth the engagement of a gear. The other involves matching the ratio of input shaft speed to output shaft speed to allow the dog teeth of the gears in the transmission mesh precisely. This second type is used in double-clutching and is not necessary unless the transmission is non-synchro. The first kind of rev-matching is what is commonly referred to.

Most of the time, you can just play it by ear and get it right.

ZV

 

[Zenmervolt]

Originally posted by: Eli
In my opinion, engine braking couldn't possibly add any more wear to the drivetrain than acceleration and/or startoffs.

Engine braking, per se, does not. It's the additional shifting that may or may not accompany it that slightly increases wear on the clutch.

ZV

 

[TheLonelyPhoenix]

So, what I got out of this thread was:

1) Don't switch gears to engine brake. Let off the gas and let the internal resistance of the gears do some work, the car is 'smart enough' to know not to use any fuel until RPMs have dropped to near idle levels. At that point, press the clutch pedal in and use the brakes.

2) Double-clutching is unnecessary for normal driving, its reserved for older cars and racing environments.

Is that right?

 

[TheLonelyPhoenix]

And would someone please tell me how long it should take me to engage/disengage a gear ideally, once ive got smoothness down? i feel like a broken record with this question, but you all seem to be glossing it over...

 

[Zenmervolt]

Originally posted by: TheLonelyPhoenix
So, what I got out of this thread was:

1) Don't switch gears to engine brake. Let off the gas and let the internal resistance of the gears do some work, the car is 'smart enough' to know not to use any fuel until RPMs have dropped to near idle levels. At that point, press the clutch pedal in and use the brakes.

2) Double-clutching is unnecessary for normal driving, its reserved for older cars and racing environments.

Is that right?

That should serve you well.

Remember smoothness too. It's more important than anything else. While you will be "slow" at first, as the motions become embedded in "muscle memory" you will get faster without trying. If you try to make yourself faster, you will have problems with smoothness and will slow things down in the long run by increasing the liklihood of missed-shifts.

ZV

 

[flot]

Don't be so paranoid about your driving.

Try to drive like a normal person. This means that if your passengers are getting whiplash every time you shift, or if the car/engine is making funny noises, you aren't doing it right.

You _clearly_ don't have enough experience with the car to be putting all of this thought into it. You are going to overthink everything and screw up way worse than before. Go drive your car for a couple months and reask your questions.

PS before you ask for the gazillionth time, it should take you approximately 1.5 seconds to go from a standstill to your foot entirely off the clutch, and it should take less than a second to switch gears. In fact, once you are a decent driver, it goes "push in cluch, switch gear, let off clutch" in one smooth 3 part process. IE there is no "delay" between any parts, as soon as your foot hits the floor your start moving the shifter, and as soon as the shifter is in, you start letting the clutch out.

Just hypothetically speaking, let's say you shift from 2nd to 3rd at 25 mph. 25 mph in 2nd is 3000 rpm, and 25 mph in 3rd is 2000 rpm. In an "ideal" shift, you would be accelerating, and at 24.9 mph (2999 rpm) you push in the clutch, and then shift to 3rd. As the engine is naturally slowing down (your foot is off the gas, remember?) you begin to let the clutch out around 2300 rpm, and at 2100 rpm you feel the clutch grabbing, and at 2001 rpm your foot is completely off the clutch and the gear change has taken place. In theory, then, the "perfect" 2-3 shift would take exactly as long as it takes the engine speed to drop from 3000 rpm to 2000 rpm.

 

[flot]

Originally posted by: episodic
If you are real good you can put it in without a clutch (at least I could on my cj-5 way back). . .
Course I never used a clutch when I drove a semi either . . .
Float the gears . . . be one with the engine

A note on this - I think it depends somewhat on the transmission. I had mastered the art of shifting without the clutch in my Jeep YJ, but then got rid of it in favor of a newer TJ, and can't do it at all, will groink the gears every time I try. Don't know if it has to do specifically with transmission design, or the tolerances involved, gear cut, etc, but ???

It is definitely a fun trick to impress your friends.

Note to original poster: Ignore all these messages, they will hopelessly confuse you. Sorry to hijack the thread.

 

[Zenmervolt]

Originally posted by: TheLonelyPhoenix
And would someone please tell me how long it should take me to engage/disengage a gear ideally, once ive got smoothness down? i feel like a broken record with this question, but you all seem to be glossing it over...

We gloss over it because it's not important. If it's smooth, it'll be right. Depending on the type of driving, I would say that it can range between 0.5 seconds to 2 seconds in normal driving.

ZV

 

[TheLonelyPhoenix]

Originally posted by: flot
Don't be so paranoid about your driving.

Try to drive like a normal person. This means that if your passengers are getting whiplash every time you shift, or if the car/engine is making funny noises, you aren't doing it right.

You _clearly_ don't have enough experience with the car to be putting all of this thought into it. You are going to overthink everything and screw up way worse than before. Go drive your car for a couple months and reask your questions.

Has nothing to do with paranoia, it a matter of having some information to chew on while I'm getting used to driving stick. I can't imagine how just going out and "driving for a couple months" is going to teach me a thing if I didn't know what I was doing to start with. Its just about getting some information to start off on, so that as I gain that experience, I have a good base of information to pair with it. You know, like when learning anything else.

And as I've only been driving stick regularly for about a week, I'm not making any experience claims either. On the third day of practice, I could drive without fearing for my safety and well-being, but I expect it will be three months before I can claim any kind of proficiency at it.

 

[TheLonelyPhoenix]

Originally posted by: flot
Note to original poster: Ignore all these messages, they will hopelessly confuse you. Sorry to hijack the thread.

Actually, I think I got some good points out of this thread. Contrary to what you may think, I'm not some high school kid who just got a new car for his sixteenth birthday or something.

 

[GTaudiophile]

While I don't normally use double-clutching with rev-matching, it's fun to do on the right road.

(BTW, I drive a Mazda Miata)

 

[GTaudiophile]

And another tip:

When on hills, despite the way it may feel, you are not sliding back multiple feet. It's really only a few inches, and unless the guy behind you is ON your rear bumper, you'll be okay. It helps to learn hill starting by using the e-break. I only needed to do that like twice before I got the hang of it.

 

[TheLonelyPhoenix]

Originally posted by: GTaudiophile
And another tip:

When on hills, despite the way it may feel, you are not sliding back multiple feet. It's really only a few inches, and unless the guy behind you is ON your rear bumper, you'll be okay. It helps to learn hill starting by using the e-break. I only needed to do that like twice before I got the hang of it.

yeah, i learned to use my handbrake on uphill starts from my dad. Pull the handbrake, let the clutch out to its engagement point with a little bit of gas, then release the handbrake. Because you've just barely engaged it, you wont slide backwards and can then normally release clutch/push gas to go. Its only necessary on fairly steep hills though, from my (limited) experience

 

[Zenmervolt]

Originally posted by: TheLonelyPhoenix

Originally posted by: flot
Note to original poster: Ignore all these messages, they will hopelessly confuse you. Sorry to hijack the thread.

Actually, I think I got some good points out of this thread. Contrary to what you may think, I'm not some high school kid who just got a new car for his sixteenth birthday or something.

I think he just meant the bits about shifting without using the clutch.

ZV

 

[mdcrab]

Not sure if it is mentioned in here, but generally it is not a good idea to downshift into first.

Also you mentioned you want to drive for good gas milage. A few pointers:
1. Drive like you have a raw egg between your foot and the gas pedal.
2. Shift at the lowest recommended shift points, don't run out the gears.
3. Coast whenever it is safe and possible. Speed should increase slightly as you approach the bottom of a hill, and decrease slightly as you approach the crest.
4. The least gas consumption occurs with the least depression of the gas pedal (same as #1)

Driving for economy can be a challenge, but it's definitely not as fun as driving for speed & acceleration.

mdcrab

 

[TheLonelyPhoenix]

Originally posted by: Zenmervolt

Originally posted by: TheLonelyPhoenix

Originally posted by: flot
Note to original poster: Ignore all these messages, they will hopelessly confuse you. Sorry to hijack the thread.

Actually, I think I got some good points out of this thread. Contrary to what you may think, I'm not some high school kid who just got a new car for his sixteenth birthday or something.

I think he just meant the bits about shifting without using the clutch.

ZV

not exactly sure why that should be confusing me either, ive seen plenty of people do it... they just tend to be the people who also like to do massive burnouts and other fun "impressive" stuff