Noob questions about pulse and glide
 

Hi I was wondering if pulse and glide will still be efficient with the engine on? as i cant really turn off the engine here because of the needed demand on airconditioning (humid and hot here) or will dwl work better?

also when slowing down to a slow pace is it better to use dfco or just put it in neutral?

another question is if its better to stay at the best bsfc at a lower gear (say 2500 rpm 2nd gear hi load) compared to lets say 2000 rpm 3rd gear hi load but not in the "best island" in the bsfc.

thanks!

Frankly, no one can answer those questions for you. You'll just have to fine tune your technique for your car and conditions.

In summer I EOnC in neutral, so I can keep the A/C (A Prius is great for hot weather BTW).

If you look at BSFC maps you really don't loose much efficiency by not being perfectly on the island, it's a few percent so I don't worry much about it, I just try to stay near 80% load (NA petrol cars).

Most of my P&G is with the engine on. It's as simple as popping out of gear and watching the instant mpg skyrocket.

At 60 mph my car settles down to 270-300 mpg. It's not off, but it's nothing to sneeze at.

Think about it like this, the engine consumes more power the faster it spins because that's how friction works. By putting it in idle, you're slowing the engine down and reducing its energy consumption, so yes, it generally works.

It might not work on certain cars with extremely tall gearing on flat terrain. If your cruise rpm is like 1500 (e.g. Corvette) I would guess that engine on pulse and glide doesn't do much. However if you see a hill, that's a good opportunity to drop it in neutral on a slight downgrade.

If you have to slow down it is best to slow in neutral. The trick is to throw it into neutral early enough that you will be down to the target speed at the right time.

For example: if you know the speed limit decreases ahead find the spot where you can coast in neutral from and reach the slower speed zone at the reduced speed limit. This way you are throwing away less of the energy that was used to get up to speed in the first place.

Neutral, DFCO, brakes {last resort :) }

Hi thankyou for your responses! its quite hard really to have an economical figure here because there are lot of speed bumps! i think every 200m to 300m. i get 18km/l tops when cruising on long trips but get a horrible 6-8km/l at city driving despite P&G because of the speed bumps and awful traffic. well looks like ill modify my P&G at a lower rpm and more load thanks!

got a noob question about P&G...

Started to do the gas it up above the speed limit, push the clutch in to glide, repeat. When you pulse back up to speed, should you accelerate as fast as possible back to speed? Or should you ease the acceleration up?

Here's a BSFC chart for my engine:

http://i.imgur.com/ADlajSq.jpg


I generally drive at 50mph when the speed limit is 50 or above, which puts me right at 2000RPM, where the engine can most efficiently convert fuel into motive energy. From the chart, you can see that above ~75% load, efficiency begins to drop off, so it's best to accelerate at high but not full load.

I have a $3 eBay ELM327 bluetooth dongle paired with my smartphone I used to keep an eye on load until I got a feel for it.

thanks for the reply. you guys really know your stuff. A lot of it is well above my head. I def need to do some driving experimenting to find my efficiency sweet spots.

Perhaps a more helpful tip would be that, when I do P&G, I pulse in top gear at medium-acceleration. Given that I live in a very hilly/mountainous area, my pulses generally coincide with climbing one side of a hill, while my glides I do with the engine off down the other.

makes sense. I've only been P&G'ing for one tank so far. Got a lot to learn

Everything is situational. Your car, roads and driving conditions are unique. The things you'll learn are transferrable, but if you change your route you'll have a lot to learn. Even the traffic conditions at different times will give you things to learn. After years in the Aveo you'll have to learn your next car too.

Get a ScanGauge or UltraGauge. Being able to see short trip (since startup) and long trip (reset every fill up) mpg, as well as a few other things that you may find helpful will help you see what's going on and learn a lot.

And welcome to the fun!

not sure I completely understand the scangauge. I've been looking at them, but how do you hook it up to your car? I have two ports, one under the steering column and another under my glove box.

I don't have an SG or an Aveo. Haven't learned them yet. ;)

Aveo, I don't think you will be ever using (able to get car to go into) DFCO if you are driving where there is a speed bump every 200-300 meters.

The biggest gains in fuel economy will be driving habits. It becoms second nature after a while. Poke around this classic blog for ideas on saving a bunch of gas..
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com

btw..ac and pulse n glide? You should hate ac just as much as satin and brakin' if you are hyper-miling :)

I don't slow for speed bumps. It's my way of telling The Man that he can wear down my suspension components, but he can never take my freedom.

Speed bumps should be illegal.

I have a question (okay a few questions) for you guys that EOC for your glide. How do you start back up? Do you pop the clutch or use the starter? Either way, doesn't that wear out components faster? Honest question, not being a troll. I tried EOC a few times and restarted with the clutch but I keep thinking I'm going to take out the clutch over time. I've been trying to play around a bit with EOnC coast. I think it helps a little but not a lot. Now almost all my driving is in heavy city traffic, mostly with a cold engine. I'm not doing the 80% load with a cold engine and I usually just get up to speed and I have to stop anyway. Is P&G even a technique that works in town?

If you just drop it into gear, you will wreck components. If you just touch the clutch plate to the flywheel--hardly even feeling the contact a lot of the time--you will not wear out components. For proof all I have is my car. It has the original 1998 Honda clutch, I know because I bought it from a dealer in Virignia, certified used, in 2001. The car now has almost 250k miles on it. Same clutch. I have been bump starting it using 5th, 4th, 3rd, and sometimes even 2cd gear maybe 50 or 60 times a day minimum every day of the week for 5.5 years and about 75k or 80k miles. Still drives great.

Using the starter. Since I shut down at all significant stops (not stop signs), I also use the starter a lot. 20 times a day maybe? Still using the 1998 starter motor.

It just keep going, and going, and going....

Thanks, personal experience is good. This is my first manual trans daily driver in over 20 years. Just driving it normally I'm not as smooth as I used to be when I was a kid lol. getting better though. can't really eoc now anyway cause it's always dark and it sometimes doesn't even get warm enough to open the thermostat with the cold, but I may give it a try again when the weather improves.

Yeah, the north winter isn't EOC weather.

Like California98Civic was saying, there's a big difference between bump starting and popping the clutch. If you can engage the disc brakes smoothly, I'm sure you'll be working the clutch just fine in no time.

Get yourself an SG or UG and you'll see how much gliding (on or off) works, the difference is incredible. In town is made for P&G: you just said that you get up to speed and have to stop, you just need to work it to your advantage. Decelerating in gear puts you in DFCO. Dropping into neutral lets you keep going, slowing a bit, at maybe a couple hundred mpg (that's where the gauges come in). Working with any slight hills can help you maximize this.

I do some horrible bumper to bumper traffic. Yes, working a clutch is a lot of work, but so is riding the brakes like everyone else is doing. But by tapping myself along I'm burning a lot less gas and not wearing my brakes at all, and by doing it well I'm not wearing the clutch either- my last car lived and died on that commute and stood up to some serious thrashing before I came here, and it went away at 205k (207k? Don't remember exactly) miles with its original clutch.

Do you have your grille blocked? That works wonders with warmup time.

Thanks, sounds like I just need to master the techniques and not worry so much. I don't mind working the clutch as long as it doesn't cost me money. I've actually been enjoying driving again for the first time in a long time. I do have a SG and I watch it closely. I've been mostly doing what you said already so maybe just need to keep practicing. I have a full grill block, insulated belly pan, hood and around a good portion of the engine bay. It's just with a 4 mile commute and a third to half of that in neutral, it doesn't run long enough. Do you shut the engine off when you're stuck inching along in traffic?

It depends on just how stuck things are.

In stop/go, crawling traffic, I will bump start as low as 20 mph. And anywhere that I sit still for at least 7 to 10 seconds, I will shut down and use the starter when it's time to move. I slow-moving traffic, I do like trucks and let a little extra space open up in front of me. I roll along slowly at 25 or 35 MPH pluse and gliding. Regularly see some of my most amazing FE numbers in the worst LA traffic.

But until you are much more comfortable with bump starting I would recommend not trying it below 20 mph or 3 rd gear much. It is harder to do gently at really slow speeds.

I EOC a fair amount and I even bump start under 10mph sometimes... The little Civic VX engine doesn't mind a bit.
My Other Car is a 2000 Civic EX... I swapped out the engine for a JDM B16A that I actually get better MPG's (35mpg)than the stock engine... and have much more power if I so choose to use it. I don't drive it much as my VX is my favorite car of all time.

Forgive me being a bid radical, but isn't a puny four mile commute a bit of a waste of fuel? why not just cycle it? I got an 8 mile commute and cycle it in about 27 minute, only 7 or so minutes than I can manage it in the car.

Yes... 4 miles is a short commute, but my commute is only about 6 miles, but not very bike friendly and not worth the risk of injury, but this is slowly changing around the Omaha Metro Area. With my 50+mpg's.. I can drive to work all week on just barely over 1 gallon of gas. At $2.19 a gallon in the central part of the U.S.... not a huge concern. Even when our gas was almost double... still not a big deal with the economy I'm enjoying. It's fun driving one of the most fuel efficient vehicles ever made.

If your vehicle is like my pickup, even when you put the trans in neutral while moving, the engine rpms do not drop below what they were with just the throttle lifted while in gear. --> due to the engine management system.
Even with that, I have seen pulse and glide work, just not as well as my wife's car, which goes into DFCO if you lift off the throttle at speeds above 60mph.
Based on what I have learned from driving the wife's car, I am ordering parts to fabricate for my truck a cockpit and/or throttle activated fuel cutoff. This may be of interest to the OP, if the vehicle is injected.

So where, or how did you get this chart for your engine? I'd like to get one for my truck.
And, for those like me, who really didn't/don't understand the whole pulse and glide concept, take a look here at this autospeed page: AutoSpeed - FuelSmart, Part 1

I confess, I have always found BSFC maps labelled like this one a little confusing. The vertical axis is labelled "engine torque" but we are discussing it as if it is "load percentage." The below image from Autospeed article ECONORAM linked in post #28 above has a map labelled "engine load" on the vertical axis. Torque and load % are not the same thing, though. And on Autospeed graph it seems like 45% to 65% load would yield the best FE.

http://us1.webpublications.com.au/st...13297_10mg.jpg

I missed this comment, didn't see it till now. Since it was about my commute I'll still respond. If I lived in a warm climate with less drastic swings between daylight and dark I probably would bike year round. I know guys that do it here, but my old body just won't take it anymore. Not to mention, to ride a bike in the dark on slippery streets in heavy traffic you have to have a death wish. I rode my bike most of last summer. I loved it and really hope to be back on it soon, maybe this week. I don't know if this guy would be so happy to be out riding if it was in the dark with 30-50 kph wind and wind chills in the -30's C. It's still been freezing nearly every night here.

Anyway, enough of that. I think my skills are improving. Set a new personal best for myself this tank so I'm happy. I think this car really is at its best in city driving. Thanks again guys for the advice, it's helped a lot.

That graph is still showing engine torque up the vertical axis since it goes to 145 even though it is labeled as load. We have no way of knowing what the corresponding throttle angle is.

I don't know that we can trust a visual so poorly labeled. It clearly says load. If it is correctly labelled, then we don't know how to read it yet. Load percent and throttle angle are different, too. I see chaos in these images.

This is how I read it:

The vertical axis is BMEP, or brake effective mean pressure - basically torque. An engine with a flat torque curve would be a straight line, but torque in this engine peaks at around 3500RPM and drops off above that (because the engine starts to run out of air, head doesn't flow well), so you have a curved graph.

I'm going to pick 2000RPM as an exampe: Peak BMEP there is ~140 (not sure of units, but it doesn't matter). Peak efficiency is just above 100 (75% of 140), with a highly efficient range of ~80-120 (65-85%). So, ideally you'd be shooting for about 75% load, give or take 10.

Due to how throttle plates work, the throttle opening for 75% load will be much larger at 4000RPM than at 2000RPM, since the engine needs a lot more air. There's no easy way to convert throttle opening to load - for this, you either need a vacuum gauge or an OBD II reader. Luckily, a $5 ELM327 bluetooth dongle + $3 Torque Pro app for Android can show load values:

http://i.imgur.com/4CzyLJR.png

I did not relize that the curve accross the color-coded fuel consumption zones was also data (a torque curve). Great write-up. The graph would be even clearer if there were a couple load curves overlaid on it and the BMEP numbers were labelled simply torque. And this means that in the previous graph you described, for your engine, in post #8 above, that the thick and angukar black line crossing the fuel consumption zones near the top is also your torque "curve," correct? Makes much better sense to me. I hope the OP fully gets it too for his "noob" question about P&G. Thanks!