Pulse & Glide - am I correct? (City area)

[PeterRRC]

Hello,

I'm ecodriver since around 4 years. My most driving are in city area where is PSL 30 mph and where is a lot of traffic lights and intersection. My average mileage is around 30 miles every day in these conditions. EPA for my car in mix 1/3 (hwy/city) is ~32MPG.
To tell the truth my average fuel consumption by driving only in my city is about 32MPG so not bad I think (no hwy driving).

I've read this forum earlier (before register) and would like to ask the advanced hypermilers for advice.

So this is what have I done so far to improve my FE:
- Tire pressure 32PSI (all tires)
- Vacuum Gauge on Dashboard
- Engine oil: 10W45
- Few modifications in front bumper for better aerodynamic profile
- Kill switch (used very rare so far) and I started to turn off engine on almost every lights where I'm sure I will be idling for more than 10 seconds.
- I also use DWB & DWL and also constant driving when possible with speed around 30mph.

I've read about technique P&G and I have few doubts since I have recently found BSFC chart for my car engine:


So from this chart it looks like the less fuel I will burn if I'll accelerate with 100% throtle between 2300-2700 rpm, so for my car on selected gears it will be:

Gear --- Speed for 2300 rpm --- Speed for 2700 rpm
1 ------- 10 mph (17 kph) -------- 12 mph (20 kph)
2 ------- 19 mph (30 kph) -------- 22 mph (35 kph)
3 ------- 28 mph (45 kph) -------- 33 mph (53 kph)
4 ------- 38 mph (62 kph) -------- 45 mph (72 kph)
5 ------- 50 mph (80 kph) -------- 58 mph (93 kph)

BUT...
1. Does 100% throttle mean excatly: 10 to 5 In/Hg (the yellow field on my vacuum gauge), or 5-0 In/Hg (red field)?
How should I do P&G with this BSFC chart for my engine to get better FE?

2. Does P&G will be better than constant crusing (when possible of course) in:
- flat city/urban area (speed limit 30mph/35mph),
- flat hwy (55-60mph - PSL is much higher but I want to keep this speed)

3 The other thing I've noticed is that that this engine - 1.3L MPI (50kW) has very high rpm at 55mph (it's 2600 rpm) - when I'm crusing on hwy with this speed my car gets around 39MPG... is there smth else what can I do to decrease burned fuel?



Thank you in advance,
Peter.

[brick]

Originally Posted by PeterRRC

So this is what have I done so far to improve my FE:
- Tire pressure 32PSI (all tires)
- Vacuum Gauge on Dashboard
- Engine oil: 10W45
- Few modifications in front bumper for better aerodynamic profile
- Kill switch (used very rare so far) and I started to turn off engine on almost every lights where I'm sure I will be idling for more than 10 seconds.
- I also use DWB & DWL and also constant driving when possible with speed around 30mph.


BUT...
1. Does 100% throttle mean excatly: 10 to 5 In/Hg (the yellow field on my vacuum gauge), or 5-0 In/Hg (red field)?
How should I do P&G with this BSFC chart for my engine to get better FE?

2. Does P&G will be better than constant crusing (when possible of course) in:
- flat city/urban area (speed limit 30mph/35mph),
- flat hwy (55-60mph - PSL is much higher but I want to keep this speed)

3 The other thing I've noticed is that that this engine - 1.3L MPI (50kW) has very high rpm at 55mph (it's 2600 rpm) - when I'm crusing on hwy with this speed my car gets around 39MPG... is there smth else what can I do to decrease burned fuel?

A few things:
32 psi sounds quite low. We typically recommend that folks run at the pressure written on the tire ("max sidewall") not the pressure written on the door jamb. Some will use even more pressure, but that is their own choice.

10W45 is an incredibly heavy oil. That's fine if that is what your car requires, but I would be very surprised unless it were quite an old vehicle. Heavy oils bog an engine down and harm efficiency, so please make sure that is correct or else change it out for the right oil.

On the BSFC thing, the problem with your chart I think is that it only shows full throttle. That's not very helpful because you don't want to use full-throttle. Ever. The reason is that engine control systems dump in more fuel than is required just to prevent knocking at very high load.

The general consensus here is that the best results come from accelerating at part throttle and low RPM. Change up at as low an engine speed you can, but not so low that the engine struggles in the next gear. Shoot for something like 70% throttle.

You will have to experiment with your car to see what works best. P&G is usually better than steady state, but only if used properly. The longer the glide, the better. High-speed P&G ("HS-P&G") usually requires some kind of down-hill stretch to aid the glide due to added aerodynamic drag.

[PeterRRC]

Thanks for the reply Tim,

Pressure recommended for my vehicle's tires is 30PSI, when loaded - front: 32PSI, rear: 35PSI. Probably I will increase pressure by few PSI maybe to 35 for both front and rear tires but I'm still worry about wear of my suspension (tire should also absorb some shock from the road but when it's pump too much then all work have to do your suspension)

I use oil 10W45 because of the climate where I live. We have cold winters, sometimes temperature can drop even to -30 Celcius deg., on the other hand summers are hot and then temperature is about +30 to +40 Celcius degrees. So I have no other option in case of my motor oil class.

That is my problem I can't find other BSFC chart, it's only one available I've found
I remember from this article that

(...) But what happens at part throttle, as occurs in nearly all normal car use?

Well, then, the situation is very different! And the trouble is, the SFC figures are always much worse...

Because of this quotation I guess that in my case any pressure less than 100% throttle will give be worse FE. Am I right?
So till now I've driven since friday (results are unknown so far) through city area using P&G technique:
a.) Brisk starts:
1st gear accelerate from 0-12mph (900-2700 rpm) -> with more throttle between 2300 and 2700 rpm (red scale on my vacuum gauge: 5-0 In/Hg)
2nd gear from 12mph to 19mph (1700-2400 rpm) -> more throttle between 2300-2700 rpm (again in red scale on my vaccum gauge)
3rd gear from 19 to 37mph (1700-3000 rpm) -> again more throttle between 2300-2700 rpm. (red scale on vacuum gauge)

b.) After reach 37mph (30mph PSL) switch to neutral gear and glide (NICE-On).

c.) My delta = 12mph, so my highest speed was 37, lowest when gliding was 25mph.

d.) Since I reached 25mph speed I switch gear from neutral to 3rd and pulse (like I described above) to 37mph. It takes about 6 seconds.

Here is vacuum gauge I use:
http://www.rapidonline.com/netalogue...M310455W01.jpg

So do I should use less throttle during accelerations?
75% LOD how much it will be on my vacuum gauge? (10-5 In/Hg? yellow field)?

I have also noticed one more thing during steady crusing on flat road with PSL = 30mph.
- when I'm doing 30mph on 3rd gear (about 2600 rpm) than my vacuum gauge shows 19-17 In/Hg.
And now if I change the gear to 4rd gear (about 1900 rpm) (then vacumm gauge shows about 16-15 In/Hg) - on the flat road and with steady foot.
I don't get it, maybe this engine like higher rpm and in higher range is more efficient? Any idea?


PS. Here is a table I've done with speed (MPH)/gear/rpm for my engine:

[Right Lane Cruiser]

I think you've missed the point Tim was trying to make. If you try to use 100% throttle you'll be dumping fuel into the combustion chamber that cannot be burned. Sure you'll get more power but it won't be more efficient. Stick to somewhere between 75 and 80% total engine load to get max efficiency.

P&G will work on any terrain other than steep hills that prevent much in the way of a coast distance because of gravity.

As for tire pressure, most of us run significantly higher than the numbers you are listing. Sure there will be more suspension wear but it really is negligible in the vast majority of circumstances.

Thick oil is the opposite of what you want in cold circumstances. It gets down to -31 C or so here in the winter (Minnesota) and will get around 38 C for a high here during the summer. I run 0W20 in my Insight in all temperatures without issues. My Elantra is spec'd for 10W30 and I run that year round... though I could go down to 0W30 for lower pouring viscosity and wouldn't hesitate to run that at all temperatures. The only reason I haven't yet is that I bought a case of oil some time ago that is 10W30 and haven't used it all up yet.

[abcdpeterson]

Originally Posted by PeterRRC

- Tire pressure 32PSI (all tires)
....

...
2. Does P&G will be better than constant crusing (when possible of course) in:
- flat city/urban area (speed limit 30mph/35mph),
- flat hwy (55-60mph - PSL is much higher but I want to keep this speed)

check tire listed max. I am betting you can go higher without issue, and see gains in FE.

I love P&G in city. my city mileage is my best mileage. I make a game of using P&G to avoid trafic stops, gliding when I see trafic stopping ahead of me planing the glid so i don't have to stop.

[PeterRRC]

OK I think I got it. So now can anyone tell me how to properly assess LOD in scale of vacuum gauge?
I mean i.e. what values ​​should indicate vacuum gauge when LOD is 75-80%?
Is it the yellow field (from 10-5 In/Hg) or maybe lower? Unfortunatelly my car has only old ODB output so I can't use SGII or UG to check this byself. Thanks.

About tire pressure and oil I will take a look closer at these things, thanks again

Originally Posted by abcdpeterson

(...)
I make a game of using P&G to avoid trafic stops, gliding when I see trafic stopping ahead of me planing the glid so i don't have to stop.

I've started to love this game it's some kind of competition between me and my car

[EVuser]

Originally Posted by PeterRRC

OK I think I got it. So now can anyone tell me how to properly assess LOD in scale of vacuum gauge?
I mean i.e. what values ​​should indicate vacuum gauge when LOD is 75-80%?
Is it the yellow field (from 10-5 In/Hg) or maybe lower? Unfortunatelly my car has only old ODB output so I can't use SGII or UG to check this byself. Thanks.

About tire pressure and oil I will take a look closer at these things, thanks again




I've started to love this game it's some kind of competition between me and my car

Peter,
Try picking a vacuum number that allows the car to accelerate at a slow rate from gear to gear. If you lock your foot in a set position and the car accelerates at say 10-11 in of vacuum you should see the vacuum number increase as the rpm increases. Shift to the next gear when the car will again accelerate at that same 10-11 inches. In the days of carbs all of the enrichment features usually came into action starting around 10 inches. Fuel injection can map that enrichment much more precisely but I would guess it starts about the same.

If you are only going to 30 mph and have a 4 or 5 speed transmission it would be likely that you might make a 2-4 or 3-5 shift to your best cruise. This really depends upon the capability or torque curve of your engine. I'm sure the experts will disagree with me if I'm wrong in regards to this. I don't hypermile a manual at all but certainly try to get the 5 speed auto in the HAH into as high a gear as it can pull on 3 cylinders as soon as possible. Both the SG2 and the vehicle confirm max mpg when driven this way in town.

The rear view mirror is my number one device when it comes to judging the potential distance at which to start a glide. Like you I enjoy the challenge of getting the most distance out of the least amount of energy. From 30 mph on flat terrain the Solectria can glide an amazing distance as the speed very slowly drops from aero drag and tire friction. Not hindering other drivers is a priority I hold above my personal kwh per mile achievments so checking the mirror is important . Tire friction seems to be all about psi as I can tell a immediate change in glide with a slight drop in tire pressure. and an increase with a slight increase in PSI .

[Right Lane Cruiser]

Peter, I don't know how it translates to your vacuum gauge but you can also do a reasonable guess based on feel — that's how I determined the correct acceleration rate in my Elantra initially. At any given speed in a gear you'll find that at some throttle position the car stops accelerating harder — that's your 100% load level. Estimate 3/4 of that acceleration rate and you'll be at around 75% load.

It can be quite difficult to improve beyond a certain level without an instant fuel economy readout display of some sort, but not impossible. Take a look at what our French member Groar (Denis) has achieved in his Megane sometime. However, perhaps you could install a SuperMID (designed by our very own member named Yoshi in Japan and using metric units) or an MPGuino (based on an Arduino controller and using english units like mpg) — both require a little wiring but will work if you have electronic fuel injection and a VSS signal.

Good luck and do keep us posted on your progress!!

[PeterRRC]

Thanks Sean,

Yes I have Multi Point Injection system in my car so idea with MPGuino it's not so bad.
There is also orginal trip computer for my car - TC-6 (on the left side of dashboard) but it costs about $150-200 and it's almost unassailable on the market.
So far I will test my FE techniques without instant FE gadgets (except the vacuum gauge I already have) and I will see how it works for me.
Thank you also for detailed explanation and contacts to other members you have given in your last post. I will keep these data for future.

[PaleMelanesian]

On my 1.6 Honda, 80% LOD equates to 12 PSI. I don't know how that converts to Hg, but my gauge reads 14.3 ambient with the engine off.

Try using lower rpm. Since you have a small engine you'll need more rpm than a larger one, but maybe 1600 - 2500 rpm should do you well.