Hypermilling...anyone heard of this process? [Archive] - SaabCentral Forums

: Hypermilling...anyone heard of this process?

23rd June 2009, 03:05 PM
Here's the link http://www.youtube.com/watch?v=dAkRLjx8FeU

Though its at idle it does seem to make a difference. Don't know what kind of pos/neg results it would have at driving speeds but it does make some sense. Thought I would post it and see what everyone else thought about the idea!

23rd June 2009, 04:03 PM
I've been hypermiling on and off for a year or so; it makes a dramatic difference in fuel economy, and comes with the unexpected benefit of making one a safer and more aware driver...

check out www.ecomodder.com and www.cleanmpg.com - these sites show just how far you can go with hypermiling. All in all, when you clear away the disinformation and hype, what remains is a practical set of guidelines and practices that makes driving much more economical...

23rd June 2009, 04:25 PM
RITmusic, do you have any pics of your particular setup? thanks for the links.

23rd June 2009, 05:03 PM
I don't have any mechanical / aero mods at all... 90% of hypermiling is really about modification of driving habits, not modification of driving hardware.

That aside, I did purchase a Scangauge II, which in addition to its OBD II functionality also performs advanced trip computer functions and displays realtime feedback on a whole host of engine telemetry... one of which is instantaneous fuel consumption. Having realtime feedback of what happens to your car when you depress or release your gas pedal really changes the way you drive...

Here's a review of the scangauge I posted up at standardshift.com:


There are a few pictures of my installation in that thread.

23rd June 2009, 05:49 PM
id rather have my car in gear in the highway for when that random car decides to come out you etc.

besides...i get 33mpg on the highway at 75mph anyway.

23rd June 2009, 05:53 PM
I get my best mileage by having the SID readout on MPG. Don't let that number drop!!! I managed to average 31.5 mpg (calculated, SID said 30.5) on my last fillup:D.

However, don't do this with your girlfriend in the car, she will complain that you are driving like an old man.:suprised;

23rd June 2009, 06:10 PM
I was more curious of the steam injection rather than coasting and all that lame stuff that goes along with hypermiling...so anyone have a comment on that part of it? I would think that water injection would be better than steam but on the other hand steam is far more atomised than any mister nozzle!:confused:

23rd June 2009, 06:34 PM
That doesn't really fall under the hypermiling umbrella...

Hypermiling is more about getting better fuel economy than the EPA says you should be able to get in your car.

When you start talking about steam-cycle engines, you're entering the realm of mechanical engineering. Future green technologies and so forth...

To follow up on that point, there are a couple things you could be referring to.... neither of which involve injecting steam into a cylinder.

The first one is introducing water into a fuel/air mix in order to keep combustion temperatures low even when running very lean, but you're still running a basic otto-cycle (suck-squeeze-bang-blow).

The second one is injecting water into a cylinder that has just exhausted the gasses from combustion, thereby using the latent heat in the cylinder to flash boil the water into steam, yielding a second power stroke, making an effective self-cooling six-stroke engine (suck-squeeze-bang-blow-steam-blow).

24th June 2009, 03:17 PM
I hypermile and the benefits were near instantaneous, though it did take a while for the driving style to take hold.

The thing is, I don't own this car so I can sip gas. The tradeoff I've made is that I hypermile all week long and then drive the car like it was meant to be driven on the weekend.

The result is that I get a little over 30mpg during the week. That's with 40 minutes of highway driving with 10 minutes of city driving on each end.

I am not recommending anyone do this as their are safety and legal issues... I shift into neutral on small hills and I turn the car all the way off on larger hills. I know where those places are on my trip and it is almost automatic. I also drive 60mph instead of 70mph. I avoid idling wherever possible and I put it in neutral as soon as I see a red light or a stop sign.

As RITmusic2k stated, it's really about changing your driving habits more than anything else.

It comes down to this, are you willing to drive like a granny to increase your mileage and (anecdotally) the lifespan of your car?

24th June 2009, 04:15 PM
The only problem I see with the techniques stated so far is the turning off of your car. Is the increased fuel economy worth shortening the lifespan of your starter? Not to mention potential dangers with doing so? Otherwise, I agree with everything stated - you really do need to drive like an old person to get better fuel economy and think ahead. Just doing these things will help a lot.

Another thing you could look at is T5 or T7 suite. After perusing through this software a little bit, it looks like you could do a bit in there to help fuel economy.

24th June 2009, 04:36 PM
Evidence concerning wear on the starter is inconclusive. That said, of course it's going to wear out sooner. Most folks start their car maybe three or four times a day during a work week. On my trip, I start my four times going to work and three times on the way back. So, we'll call my usage roughly double. I paid $189 for a reman starter with a lifetime warranty. But, let's say that I have to replace a starter every two years because I am starting more often. I am getting approximately 30mpg where I was getting about 24mpg before. At 6mpg more, I am saving about $7.50 a tank per fillup. At the rate I drive, that is saving me about $360 a year.

In all, I feel that I am saving more than enough money to warrant starting the car more often. It is especially true since I have a lifetime warranty on my starter.

I do feel that a deeper concern is the safety issue. Even so, I started off driving a Ford Fairmont that had power nothing. Driving my Saab down a hill with no power brakes or steering is really not that big a deal. The biggest hill I coast down has a pretty sharp curve at the bottom and I have no problem negotiating the turn with no power steering. The brakes are definitely stiff. But, since the whole point is generating momentum that I will use to keep my car moving once I get to the bottom of the hill, I try to stay off the brakes anyway.

Hypermiling definitetly isn't for everyone. There are aspects of it that are not legal in some states and I don't condone breaking the law just to squeeze out a few extra mpg. At the same time, in this particular forum, I don't think the audience is too concerned about traffic regulations... not too many reasons to do a Stage 3 if you're going to keep it at 55, right?

24th June 2009, 04:56 PM
That's quite an increase you got in fuel economy with the starting deal. I guess i never calculated savings with doing that...and with that lifetime warranty that really seals the deal. What is illegal with hypermiling?
What I usually do is leave the car in gear when slowing down, because the fuel cuts off above like 1900 rpms. INFINITE MPG!!!:cheesy:

I think several people on here have said they get better fuel economy after the tune. Usually I drive for good fuel economy, but I like to be able to go supa-fast sometimes:).

25th June 2009, 09:12 AM
I think that turning the car off to coast on long hills only provides a part of the overall mileage increase. It's a lot more that I drive 60, don't run the AC, avoid braking if at all possible and generally don't drive like a 16 year old.

Hypermiling itself is not illegal. However, it is illegal in some states to drive your car in neutral. I am not aware of one where it is illegal to drive with the clutch in though... that would be kind of silly.

Any time you use your engine to brake, you are hurting your fuel economy. Try shifting into neutral/putting the clutch in on any tall or long hills and you'll see your engine go to idle revs. Do the same thing normally and your car will almost certainly stay above idle.

Oh, I should mention that many hypermilers overinflate their tires by up to 20%. I have mine overinflated 20% and I have normal wear across the tires with normal rotation schedule. It is supposed to make the ride more rough but I haven't noticed a difference. The theory is that the reduced surface area of the tire touching the road makes for less friction. There are obviously hazards associated with that too. You can also remove anything extra from your car. Some have gone as far as to remove all of the seats, most of the interior and their spare tire. I personally think taking the spare and jack out is pretty counterproductive.

25th June 2009, 07:01 PM
Engine braking doesn't hurt fuel economy, it's likely better than putting it in neutral.

When you are under engine braking the fuel cuts off completely above a certain point. At idle you still use a little fuel to keep it running.

Engine braking will obviously slow you down, but on a steep enough hill it should overcome it.

Without an instant fuel gauge it's hard to tell which is better, but try engine braking next time. I'll test it with my BMW today which has a pseudo-realtime fuel gauge.

25th June 2009, 10:42 PM
Engine braking doesn't hurt fuel economy, it's likely better than putting it in neutral.

When you are under engine braking the fuel cuts off completely above a certain point. At idle you still use a little fuel to keep it running.

Engine braking will obviously slow you down, but on a steep enough hill it should overcome it.

Without an instant fuel gauge it's hard to tell which is better, but try engine braking next time. I'll test it with my BMW today which has a pseudo-realtime fuel gauge.

I used to think this too, until I started testing it out with the scangauge. It turns out the fuel consumed at idle speed is offset by the reduced speed loss from rolling in neutral. If you stay in gear to take advantage of DFCO, you'll burn more gas getting back up to speed after finishing the coasting portion of the maneuver.

Ultimately, neutral coasting is better for sustained travel pulse-and-glide, but DFCO is better if you're going down a steep enough hill that you don't lose speed, or if you know you'll be coasting to a stop.
Another thing the scangauge taught me was that the ECU won't go into DFCO immediately... It will check to see if conditons are acceptable first, then it'll wait for up to three or four seconds before cutting off the injectors.

26th June 2009, 08:30 AM
I haven't pinned this down exactly but I believe this is the criteria for DFCO on a T5:

Temp: Engine Coolant temperature must exceed this value.
Enable Speed vs. Baro: The vehicle speed must exceed this value.
RPM vs. Gear Entry: Engine RPM must exceed table value.
TPS vs. RPM: Throttle position must be below this table value.
Map vs. Baro Entry: Map must be below this table value.

The "problem" with my route is that I do not hit all of the established criteria for DFCO on the hills so I am better off putting my car in neutral or turning it off.

Incidentally, this morning I got 36.2 mpg on the way in to work. That's almost 13mpg more than I get when I don't follow hypermiling guidelines.

26th June 2009, 05:44 PM
Nice! I hear T7s tend to be a little more fuel efficient due to the more stringent control over engine variables, but I have heard of a few instances such as yours where your guys in your T5s really post up good numbers.

My 2001 9-3 was able to sustain 42-46 highway when really trying, and hit an upwards of 32 in the city.

Carmen, being a 2.3, can't quite match those numbers, but she gets close. I can get her around 42 tops with P&G, but in the city that extra displacement makes for a bigger hurdle; I only manage 28 or so. Of course, I still end up with a tank average of <25 because of the damn desire for speed on the occasional fun run. On my best behavior, I'm getting tank averages of ~27mpg, which is a healthy 29% over my adjusted EPA combined rating of 21mpg :)