Archives

Was wondering if anyone else out there was driving a car equipped with a manually shiftable automatic transmission, and if so how they were using it in their repertoire of hypermiling techniques. I use mine basically to upshift faster than the full auto would allow, and then also when approaching a stop or a turn i use it to slow the vehicle with engine compression. I will know by tomorrow how well i did on my first tank and will update at that point.

It's better than a full / standard automatic, for sure. I really want to see your results in that wagon!

Well, just looking at the guess-guage I'm hopeful at this point, but there's no telling for sure until I'm done pumping gas tomorrow :) I'm sure it could be better though, because that first trip back and forth was driving into some serious headwinds..in excess of 35-40mph. I'm sure that didn't help any at all. And my return trip last night was partially in rain - also not helpful. So I'll use those as cop-outs if my numbers end up sucking!
In addition, probably in the next 6-12 months the wagon will need new tires - I'm hoping that I can get some Low rolling resistance shoes for it - that may help too.

In addition, probably in the next 6-12 months the wagon will need new tires - I'm hoping that I can get some Low rolling resistance shoes for it - that may help too.

If you have the 16" wheels, the Goodyear Assurance FuelMax is available in the correct size (205-60-16), and the Michelin Energy Saver A/S is available in 215-60-16 (3/8" wider, 3/8" taller), as is the Bridgestone Ecopia EP422. The Goodyear and Michelin both did very well in a fuel economy test performed by an online tire vendor about a year ago.

I have the FuelMax tires on my van, and highly recommend them. Here is the test Maxx mentioned: http://www.tirerack.com/tires/tests/TireTestServlet?tireMake=Michelin&tireModel=Energy+Saver+A%2FS&tirePageLocQty=

Yes, I priced some LRR tires on tirerack earlier today. Whew! They are expensive compared to the regular tires. Wonder if they make enough difference to actually pay for the price difference over the life of the tires?

Maxx...my sportwagon is running 17" rims, so that makes tires more expensive as well.

According to calculations I've done, it's worth it.

Yes, I priced some LRR tires on tirerack earlier today. Whew! They are expensive compared to the regular tires. Wonder if they make enough difference to actually pay for the price difference over the life of the tires?

Maxx...my sportwagon is running 17" rims, so that makes tires more expensive as well.

On that same site, it lists your OEM tires as Michelin Pilot HX MXM and lists 215/50-17 as the size. The Michelin Energy Saver A/S and FuelMax tires are not available in that size, but are available in 225/50-17 - 3/8" taller and 3/8" wider. Whether they'd fit your car without rubbing is a question for some of the Mazda enthusiasts. From what I see, both tires - EnergySaver and FuelMax - cost less than your OEM tires. By $40 and $55, respectively.

Another option is to use tires that are known to be LRR but are not advertised as such. They include the Bridgestone Signia SE200 or Turanza EL400, Firestone FR710, Continental CV95, and some sizes of the Michelin Pilot and Primacy tires. The site you checked has started adding a "LRR" listing on tires that have a low rolling resistance, so you can look for that in the listing of tires.

Michelin symmetry, too. OEM on the Ody. The GY Fuel Max is better, new, than the Symmetrys were when well worn. Wearing down the tread helps reduce the rolling resistance, so as these wear down, the improvement should only increase.

Kumho has a new "eco solus" lrr tire that's fairly inexpensive, too.

We need standardized testing and labeling for this.

The Kumhos are probably what i'd go with. Each eco-solus tire is "only" wow - 97$ a piece. I think that getting the right size would matter...doesn't look like there is much room in the wheelwell for something bigger, Maxx.

It'll be something I'll have to research more as time goes on and the need for replacing the tires becomes more pressing. I'm not down to the wear bars on the fronts yet so I'lve got a little time.

In other news...my first refill was somewhat disappointing. Despite my best efforts. Driving on the highway at 55mph, coasting where I can in town, using the autostick to pre-empt shift points, and airing the tires to 42PSI, I was only able to return a measly 30pmg overall. Granted I had used ethanol gas, driven through two rainstorms, and had one day of 35-40mph headwinds to contend with so hopefully this next fill-up on regular will be better.

I shouldn't bitch too much though...the epa estimates for this car are lousy, so I'm beating epa at least. And still, its such a cool and functional car - I may even learn to forgive it for being a little thirsty. Wagons rock!

Have you tried to Pulse and Glide (in gear not switching to N) in the highest gear, I get great results with this because of the fuel shutoff during the glides. The only thing is you do not want to be high on the RPM’s as that will cause a quick slowdown of the vehicle in gear. Doing this between 32 and 40 MPH seems to be better than switching to N with the engine on. Anything faster would be better by switching to N during the glides.

The Kumhos are probably what i'd go with. Each eco-solus tire is "only" wow - 97$ a piece. I think that getting the right size would matter...doesn't look like there is much room in the wheelwell for something bigger, Maxx.
It'll be something I'll have to research more as time goes on and the need for replacing the tires becomes more pressing. I'm not down to the wear bars on the fronts yet so I'lve got a little time.
The eco-Solus is a 215-60-17 and your car specified 215-50-17. The 60 series tire would be 1.4" too tall and would have clearance problems. 225-50-17 or 215-55-17 might fit (typically 0.4" taller and 0.7" taller), with the likely problem being a little frame or suspension component rubbing when the wheels are turned all the way to the lock.
My brother has an HHR with 215-50-17's on it, and in the rear wheel housings, you can barely fit your fingers between the tire and the body surface. Larger tires on that car would likely be an issue. For your car, you can "eyeball" the clearance by running your hand around the circumference of the upper half of the tire, front and rear, paying special attention to the inner tread area. Do that with the wheel cranked full left and then full right and make sure your fingers are not contacting anything. If your hand can run around the circumference of the tire without contacting anything, the larger tires should fit. But even then, there is no guarantee.

My bad, Maxx...I read the numbers off Tirerack incorrectly. You are correct. Those tires would not work.


As far as P&G on the interstate is concerned I have not tried it as of yet. I may though. The fuel cutoff would be a good thing. Might try it following next fill up. I will continue to experiment and see what is the best option.

Thanks for all the input folks - this is why I love this forum and came back!

Have you tried to Pulse and Glide (in gear not switching to N) in the highest gear, I get great results with this because of the fuel shutoff during the glides. The only thing is you do not want to be high on the RPM’s as that will cause a quick slowdown of the vehicle in gear. Doing this between 32 and 40 MPH seems to be better than switching to N with the engine on. Anything faster would be better by switching to N during the glides.

I know I'd be willing to give that a shot, but I've always seen on here that it shouldn't be good at any speed.

I take it you've tried it both ways (at 32-40mph) and you found the DFCO works better for you?

-Mike

What about "Pulse and Hang"? Pulse up, but then maintain juuuust enough pedal pressure to prevent DFCO, but not enough to hold speed.

I've tested Pulse-and-DFCO to be even worse than steady speed driving, which is itself worse than P&G. I don't think that's a good approach.

I cannot imagine that P&G in gear would ever be better than steady state driving. If you're in gear and engaging DFCO, you are not gliding.

I know I'd be willing to give that a shot, but I've always seen on here that it shouldn't be good at any speed.

I take it you've tried it both ways (at 32-40mph) and you found the DFCO works better for you?

-Mike


It is always better to do P&G with the engine off during glide, but without having a true manual (same as you ) DFCO works best (in my opinion). I have to add that it is only at those speeds in my car, if I did that between 40 and 45 or 45 and 50, the results would not be as good, actually the results get worse and worse as you go faster and faster. Once I get above 40 I switch to 40-50 or 45-55 (depending on speed limit) and switch to N on the glides. If I could DFCO at 32-40MPH for my entire commute, 60MPG would be easily within reach.

Andrew - what speed did you try this at and what RPM range did you notice durring your trial? In my car I can easily get above 60MPG doing this while a steady speed of 35 nets just over 50MPG. I agree that doing this at high speeds does not work, but at low speeds I think every car should have a sweet spot where this will work better than steady speed. As far as P&G with the engine on and switching to N, the only reason I prefer not to do that is the Smart always switches to 4th gear anytime you put into gear below 41MPH, so I would either have to swith from N to D to M and select 5th gear on each cycle or leave in drive and wait until I hit 37MPH where the car will switch by itself. This would lead to 2 gear changes per cycle and not sure that there is a huge benefit when you consider wear on the clutch.

WRI consult, I have tried this at many speeds, and in most cases P&G while in gear was better than steady driving. Yesterday I had to turn my AC on and was getting about 39-40MPG, I then started P&G while in gear (40-45MPH DFCO only works at higher RPM's while the AC is on) and was able to get it up to 44MPG. Not sure why it does not work in your tests, but I am certain that it works as even other smart 451 owners that drive for mileage barely crack the 50 mark.

I don't remember. That was over 2 years ago. I found it to be worse, and didn't pursue any further. It seems logical to me, considering the drag involved in dfco.

Maybe there's a special condition in the programming of the Smart that makes it work at that range.

That may be possible, I tried this with my wife's car and did not notice any huge benefits, then again I was going by the cars MPG readout as she does not have a scangauge.

I started thinking after yesterday’s posts to see if what I am doing is actually the best way to go and figured I would do an analysis. Not that I could actually change to true P&G due to the fact that a clutch replacement for my car would cost quite a bit and each cycle results in 2 gear changes as the cars computer selects 4th gear when engaged below 41MPH. I am curious to see input as I am not sure that my calculations are accurate. I adjusted the Glide distance in proportion to the pulse time. The calculations are done on a P& G from 35-40 MPH. The actual numbers would fall somewhere in between a 3-4 second pulse so I did calculations for both.

DFCO
Pulse Avg Speed = 37.333MPH
Pulse Time = 3-4Seconds
Fuel Used (GPH) = 1.5
MPG = 24.8886
Glide Avg Speed = 37.333MPH
Glide Time = 6 Seconds
Fuel Used (GPH) = 0
MPG = NA

3 Sec Pulse
1 Mile Pulse = .040178 Gal Used
2 Mile Glide = .000000 Gal Used
3 Miles = .040178 Gal Used
MPG = 74.666

4 Sec Pulse
1 Mile Pulse = .040178 Gal Used
1.5 Mile Glide = .000000 Gal Used
2.5 Miles = .040178 Gal Used
MPG = 62.221

P&G
Pulse Avg Speed = 37.333MPH
Pulse Time = 3-4Seconds
Fuel Used (GPH) = 1.5
MPG = 24.8886
Glide Avg Speed = 37.333MPH
Glide Time = 9 Seconds
Fuel Used (GPH) = .27
MPG = 138.270

3 Sec Pulse
1 Mile Pulse = .040178 Gal Used
3 Mile Glide = .021696 Gal Used
4 Miles = .061875 Gal Used
MPG = 64.645

4 Sec Pulse
1 Mile Pulse = .040178 Gal Used
2.25 Mile Glide = .016199 Gal Used
3 Miles = .056199 Gal Used
MPG = 57.829

Sorry, still not convinced. Contradicts too much of my knowledge about how cars work for me to believe it without a LOT more data to back it up.

Can I guarantee 100% accuracy, no. My mileage logs should backup the DFCO side of the comparison (the difference can be accounted for by actually having to stop at several red lights per day).

My limited experience agrees with gabe1475 that DFCO can be better than P&G with engine on, but only when the engine RPMs are very low.

The big advantage of P&G with with engine on is by shifting to neutral I have reduced the engine friction, however the engine is running less efficient at idle because of the pumping losses caused by the mostly closed throttle. By leaving the engine in gear the friction will be higher as the engine is turning faster. However, the energy I use to drive the engine came from my pulse burn, during which the engine was running at higher efficiency than during idle.

For example my car idles at about 800 RPM with a Brake Specific Fuel Consumption (BSFC) of about 400 g/(kW*h). If my pulse is at 1200 RPM with a BSFC of about 225 g/(kW*h) then I am be better off using DFCO as my efficiency increase between idle and pulse is greater than the friction decrease. However, if my pulse is at 1600 RPM with a BSFC of about 220 g/(kW*h) then I would be better off using engine on P&G, as my friction drops in half and my pulse efficiency is less than twice my idle efficiency

My simple rule of thumb is to prefer engine on P&G over DFCO if my RPM at speed is twice the RPM of idle. (Of course engine off P&G is preferred over both.)

I disagree. At anything above parking lot speeds, neutral is going to be better.