Pulse and Glide - Fuel Economy, Hypermiling, EcoModding News and Forum

EP3 · 06-25-2008, 12:45 AM

Well I tried this and on the glide I cutoff the engine too on a long striaght strip. I am not worried so much about the cutoff b/c my car has EPS and the brakes showed no sign that I could not stop fast enough. My issue is only with the restart. I pop the clutch and it starts. This can not be good for my or any car. I know if your battery is dead you can push start a manual. But I always heard it is bad on the starter. Any thoughts?

dwendt1978 · 06-25-2008, 09:30 AM

You don't "pop" the clutch at all!! You just slowly let it out.

For example in my car, if I'm rolling at 35 mph, I put it in 5th gear and slowly let out the clutch and you can't even feel it start.

At 25 mph, same gear but then after restart I drop into 4th to get back upto speed.

This process should be soooooo smooth that if there was a passenger they wouldn't know what you were doing unless they seen it.

dwendt1978 · 06-25-2008, 09:30 AM

P.S.
You completely bypass the starter doing this.

NoCO2 · 06-25-2008, 09:46 AM

Yea, if you any popping, it's going to break something eventually...

You should be letting out the clutch slowly until you can find that exact point where the clutch is in just far enough to let the wheels scrub the engine and get it spinning. Once you can do it consistently, you can start to go faster if you would like (less wear on the clutch?) but you just have to remember where the clutch needs to be and not go further than that. It should be neither violent or rough, if done properly, like dwendt1978 said, you shouldn't even be able to feel it start.

rocket · 06-25-2008, 09:50 AM

how could it be bad on the starter? the starter doesn't even know the engine was shut off or started!

NoCO2 · 06-25-2008, 09:53 AM

The only time P&G could ever be bad for the starter is if you were turning the ignition and trying to pump start at the same time, it would be the equivalent to trying to turn the engine over with the starter when then engine is already running. If you aren't specifically telling your car, via turning the key all the way over like you would to start it, then the electromagnets in the motor for the starter are not activated and the spindle inside the starter motor just spins like it always does when the engine is running.

rocket · 06-25-2008, 10:05 AM

Quote:

Originally Posted by NoCO2

The only time P&G could ever be bad for the starter is if you were turning the ignition and trying to pump start at the same time, it would be the equivalent to trying to turn the engine over with the starter when then engine is already running. If you aren't specifically telling your car, via turning the key all the way over like you would to start it, then the electromagnets in the motor for the starter are not activated and the spindle inside the starter motor just spins like it always does when the engine is running.

most starters are not engaged when they are not being used (i've never actually seen one that was continuously engaged w/ flywheel/flexplate). When the starter is engaged, the gear extends to meet the flywheel/flexplate. If there are cars that don't do it that way, i'm curious to know!

ebacherville · 06-25-2008, 10:22 AM

Quote:

Originally Posted by rocket

most starters are not engaged when they are not being used (i've never actually seen one that was continuously engaged w/ flywheel/flexplate). When the starter is engaged, the gear extends to meet the flywheel/flexplate. If there are cars that don't do it that way, i'm curious to know!

Well hybrid cars the electric drive motor is the starter too... so technicaly.. lol

Twerp · 06-25-2008, 10:22 AM

You're prolly thinking of the cat... All of my owners manuals have said not to pop start the vehicle because it can do serious damage to the cat. They don't mention anything about the starter.

Daox · 06-25-2008, 10:36 AM

I'd look here:

How to smoothly bump start / clutch start an engine

EP3 · 06-25-2008, 03:25 PM

I should have not used that word "Pop". Yeah I have pushed started before and I know the crazy surge you are talking about. I will try to do it a little smoother today. Yeah it must have been the cat then that I heard of. But hey I just got a brand new cat a month ago..under warranty. Yea I like the ideal of the engine not burning any gas but are the gains with engine off say on a mile strip marginaly better. Say my RPMs in idile turn 900 vs 0. I just think this could cause some serious crashes. But hey what do I know. I know we don't reccommed doing this, just curious how it should be done properly and some input.

Thanks all

Daox · 06-25-2008, 03:32 PM

Why do you think this would cause crashes?

EP3 · 06-25-2008, 08:01 PM

I am speaking about if done wrong thats all. If someone was to lock there column and panic. If someone put it in the wrong gear. If someone had to stop real fast and did not have full assist of brakes. This one is reaching...If you have early airbags they may not fire off if the solinods lost they energy stored up =) reaching I know. I have faith in all of our driving skills, and when it would be approaite if used cautiously it would proably be fine. And ofcourse this is mainly an agruement if someone did it wrong acidentaly. If you just pulsed and glided in neutral you wound have all the benefits of the safety. But I guess not as good if it were cut off completely.

Daox · 06-25-2008, 08:04 PM

I totally agree. If you don't know how to P&G you shouldn't be doing it in traffic. Same goes for driving in general. If you don't know how to drive, you shouldn't be driving in traffic. Hypermiling techniques are no different from learning how to drive. Both can be dangerous if the driver doesn't know how to properly do them.

Twerp · 06-26-2008, 01:09 AM

Quote:

Originally Posted by EP3

I am speaking about if done wrong thats all. If someone was to lock there column and panic. If someone put it in the wrong gear. If someone had to stop real fast and did not have full assist of brakes. This one is reaching...If you have early airbags they may not fire off if the solinods lost they energy stored up =) reaching I know.

My safety concern would be steering lockup. On my truck, it's not an issue because the "Acc" position is right below "Run." On my fiance's Ford, the "Acc" position is below the "Lock" or "ACK!" position. So if she was to kill her engine in a turn, the wheel could lock. Should be simple enough to turn the key back and unlock it, but that little "WTF!" moment as the car seems locked into a collision course with a huge boulder might prevent an otherwise rational brain from figuring that out.

Brakes though, not a problem on most vehicles I've driven. There is usually enough power left in the brakes to effectively stop the vehicle at least twice. After two presses on the pedal, it starts requiring more muscle, but the right amount of adrenaline usually does the trick... Or just turn the vehicle back on after the second brake press.

That's my two cents.

EP3 · 06-26-2008, 01:17 AM

Yeah just that WTF second is what I am talking about...True the brakes will still work but if you push like heck it can stop. I just relized how spoiled we are now in these day with all the assist things. My first car was a 76 Datsun 280z. No A/C, no power steering, no power windows, no power locks. Just a sweet car with a inline 6 and a 4 speed man.

Twerp · 06-26-2008, 03:36 AM

Sounds like my Civic but with more power and less gears... Except I've got tilt steering for some reason. Oh and a broken cassette deck and multi (meaning more than one but not more than two) speaker stereo system.

EP3 · 06-26-2008, 09:43 AM

Quote:

Originally Posted by Twerp

Sounds like my Civic but with more power and less gears... Except I've got tilt steering for some reason. Oh and a broken cassette deck and multi (meaning more than one but not more than two) speaker stereo system.

Oh yeah The Datsun had AM FM sterio with two box speakers. No Tape Deck??? Do you 16 year olds even know what a Tape deck is? Back in my day in the 90s..we had to walk 10 miles in the snow...Both ways..

trikkonceptz · 06-26-2008, 11:57 AM

Since this thread is about P&G, how about you experienced guys give us a quick tutorial on how its done. By that I mean, please answer the following questions;

-What is the optimal speed variation; 10,15,20 mph?
-What would be the best LOD for increasing speed during a P&G
-What is the Benefit of P&G over long distance?
-Does your FE plateau or will it continue to increase over distance?

And a couple of my observations; P&Ging in my car I notice that I get to the optimal FE in no time flat, but once I am there it plateaus, therefore should I stop at that point? Or am I gaining the benefit of FE while traveling at faster speeds?

Thanks in advance for sharing the knowledge ..

Daox · 06-26-2008, 12:47 PM

I normally use a 10 mph delta when P&Ging. 15 is nice when traffic allows. I rarely do 20 unless its a totally abandoned road and I'm really in no hurry at all.

I normally accelerate around 70-85 LOD.

The benefit of P&G is better mileage over a long distance.

Your FE will plateau. However, if you go back to driving normally it'll go down. P&G is just more efficient.