Pulse and Glide questions..Totally new to this
 

Ok. I'm new here and this pulse and glide thing is very foreign to me, but I'd like to give it a try. I have a question,

When you shut off your motor do you bump start it or use the starter?

Are you not worried about excessive clutch wear? (or starter if you use that)

It is possible that this technique is just not for me because I have a lot of mechanical sympathy and am pretty much as interested in longevity of my car as I am with fuel economy. I put on a lot of km and I'd like my car to last a long time.
Thanks.

When I did P&G, I always bump start the motor. I would let out the clutch just enough to lightly grab and start the engine. Give it a try sometime and see how you feel about it.

I gave up on P&G months ago because Winnipeg traffic is all accelerate like hell to get through the green light and slam on the brakes when it turns red. People get angry when there's even a slight amount of coasting on the streets. 35-mpg is the price I pay (Instead of 60+mpg P&Ging).

And yeah, my clutch is pretty worn. It doesn't grab until the final few millimeters of release.

Peakster: that's what route selection is for ;)

Clutch start if I'm planning another pulse; key start if I'm coasting to a stop where I'm going to be waiting a while.

Excessive, no. There's going to be some wear, but I figure it's less demanding on the clutch to spin up the motor compared to the wear from accelerating the car from a dead stop. Drivers who slip their clutches when downshifting are wearing them out faster than I am with P&G.

People with automatics are going to see more starter wear because they have no option.

A lot will depend on how good (technically) you are at it. Rough drivers are going to put more wear on the drivetrain in general.

When you get practiced at clutch starting, it's very smooth. I recently showed the technique to someone, and I had to say out loud when I was killing the motor & when I had clutch started it.

Another important tip: to restart, choose a higher gear for the bump than the one you'd normally be in for the current road speed. Then shift back down to drive. Makes it a lot smoother. And Peakster's right - you just lightly/partially engage the clutch to spin up the motor and immediately de-clutch again once it fires. Then select the proper gear as usual (rev matched engagement is best).

Understandable. I wouldn't recommend it to anyone who isn't 100% comfortable with the idea.

^
I'm one of those people, one because I love my Jeep, and 2 because I'm still trying to undo the damage the old owners did to it. You don't EVER let the engine drive after 7500 miles without an oil change and no oil on the dipstick!!! They were such dumb retards. I also changed my fuel filter not too long ago and the fuel that came out was black. Spark plugs were recently changed cause the old ones had their electrodes worn so bad they were gapped over 2 times the factory gap, almost 3 times. I still need to replace some more needed maintenance, as well as an oil change needed in the next 300 or so miles. It may look like a sound vehicle, but when you buy a used J.E.E.P., Just Expect Every Problem ;)

Thanks for your answers.

'm pretty good at clutch starting, (I race motorcycles and you often have to do that if they have no starter)
I just know the more times you push the clutch in and out it has load on it and thats also put on bearings and they will just wear out faster. I can just see needing throw bearings or release bearings and having to replace them, which on a Subaru is expensive. So I was curious if this is something you factor in or even worry about.
I can see using this technique in a few places on the commute where I have a few long hills down and little short steeper hills upward on the way home. I usually take a different route home from work due to traffic being lighter. I tried it on the way home just guessing that I was supposed to clutch start and I can see that doing that regularly would probably pay off.

I just tried pulse and glide on my way to work this morning. I hadn't read this post or too much on the subject yet, but I guess I was doing it exactly right. I had the biggest grin on my face the first time I instinctually let off the clutch in fifth and the engine sparked back to life. The grin was from two things, one) how it came naturally to me without thinking and two) how smoothly it happened. I only did it on surface streets for the last mile to work, but jeez - I'm addicted. Can't wait to see what I can accomplish on my drive home tonight. I'm going to make a stop at gas stations before and after to find out.

One hang up in the process, I turn the ignition key to kill the motor - but then I have to turn it forward a click for my turn signals to work again and have it "cocked" for restarting. It's a bit awkward to reach for the key, is this where the Fuel Injector shut off switches I've heard about make the process more natural? What are the popular mods for improving the process?

(I'm using my 93 Civic DX HB, not the Metro Convertible at the moment)

I am also using key off/on again. i plan on putting a rocker switch on the dash near the wheel to kill the engine and the other half of the switch to restart w/ starter. currently this afternoon is for basic upkeep. New rear wheel bearings, and repair of the front spoiler. Note: don't let your friends borrow your car if they won't back into a parking space. S.

I have my switch on the side of the gear shift knob. Since engine stop is usually accompanied by a shift to neutral for gliding, I figured it was better ergonomics.

Good point, I'll have to keep that in mind when i am designing and instaling mine. Second note: make sure the tech puts the dust cap back on your rear hubs after State Insp, Now I know why my new bearings failed so quickly, S,

He speaks the truth.

If you do end up key starting it, doesn't this use quite a bit of fuel. I had heard roughly 30 seconds worth of idling. If that's true it may sometimes be better to just leave it on, right?

I've heard that too, but my fuel meter never really showed much fuel used from a key start where the engine was already warm. Still a consideration for wear and tear and difficulty, though.

That was IWillTry's conclusion too. He systematically measured fuel consumption @ idle, and compared it to the fuel consumed performing a warm restart.

His observations (based on a 1.0L gas engine with throttle-body injection):

He makes the same caveats about starter wear.

See his full report on iwilltry.org.

Hi All,

What speed do you pulse up to, and what speed to you glide down to during typical highway eco-driving? Is there an optimal speed differential between upper and lower limit?

Thanks,

-Warren.

it varies. Ideally, you'd pulse up to the speed limit (or a little above) and glide all the way back down to a near stop. But few of us have the patience for that kind of thing, now do we?

I'd reccomend gliding down to the lowest speed that's comfortable for you, if you're on the highway though, most people try to keep a plus-or-minus 10mph thing going.
For example, pulse up to 55, glide down to 45. Rinse, lather, repeat.

Depends on the vehicle also - my car doesn't P&G well at higher speeds because it's light and unaerodynamic (the glides don't last long enough to make it worthwhile).

What type of vehicle are you driving, Warren? Automatic or manual shift?

PS - welcome to the site.

Thanks. It's automatic. A bone stock '98 gas guzzler maxima SE. The other half doesn't want me to destroy the resale value by making the aero mods I was considering.

I'll have to see how long it will glide from 65...

-Warren.

Oh! That's your web site! I've looked at it several times before.

Before you start experimenting with P&G with your Maxima, do you have onboard fuel efficiency instrumentation? A ScanGauge?

One thing I've noticed with P&G is that it confuses the people behind you. I will P&G if there is no one behind me, or someone following at a distance. With tailgaters I just go the speed at which I would end the glide. This tells them that I won't be going any faster and that they had better pass me if they want to go faster, rather than teasing them and getting them mad. It also saves me more fuel.

For people who tailgate hard, or flash lights or beep horn (happens once in a blue moon), I will slow down some more. I mean, what are they going to do, bump me? Attempts to intimidate might work if I was riding a motorcycle, but not in a car. If I am going a legal speed, they should learn how to change lanes.

I was teaching some hypermiling techniques to a friend recently.
She didn't realize that in order to coast you have to either hold the clutch in or shift to neutral, and consequently, she didn't notice the engine reengaging - and she was the one driving! I pointed out the tach reading, and explained the idea of bump starting.

I find in my (2.5 ton commercial) truck I can get the engine going easily at any speed above 5mph and barley feel it.
You get smoother with practice. I was kind of hard on the drive train the first month or so, but now I really not worried about wearing anything out.