diamondlarry-

I just tried it and saw "0.3 LPH". Soooooo, I think there is no round-up. Since it is not "0.1 LPH", I think that the units are English-centric, which would make sense for a product developed in the USA.

I don't think changing units will make any difference in MPG, :( .

CarloSW2

Same here
 

I had the same thing.

yeah but that is .75gph maybe you can't burn at any lower a rate - guess I need to try it in my xB and see if it gets lower than the .2 - 1. gph I see all the time when warmed up...

Get a little speed up before the downhill. Makes the hill last a little longer and keeps you from getting run over. If you coast for .7 mile, your MPG should be 10% better for the following 7 miles. Add 'em up and they amount to something. Pulse and Glide can be done on level ground. 60 to 40 works pretty well for me but only if I glide in neutral, engine off.

Get in that Toyota and come see us in Colorado. We'll go trout fishing.

Ahhh, but here's the catch. I do just that BUT the road has a HUGE bump at the bottom PLUS it turns to a rocky dirt road PLUS it switchs to 15mph in the area where I'm capable of still coasting 30mph PLUS the ONE house on the road in the 15mph area has a cop as a best buddy, he's always there in that 15mph zone. He even waits for me sometimes at 0500am - pretty cool guy as I am normally cruising 35-40mph through there at that time of the morning, This is really out in the middle of nowhere with no side roads, kids etc.

I do have an alternate route I do an engine off coast on when I am driving my Metro, HUGE savings and it is about .5 of a mile. Always cars on that road though, I hate traffic.

Toyota still needs work, I need to find the time (and motivation and $$$) to work on it. BTW, if you're still in Daytona and drove out PM me, I'm just a few minutes off I-10 - I'll let you take the Insight out for a spin.

Not sure about all diesel?s, but my TDI uses no fuel coasting in gear down hill. At idle scangauge will show about .2L/hr once warm. If I am going down a hill in 5th with no throttle added it shows 0.0L/hr, if I push the clutch in it goes back up to .2L/hr.

So the big debate on the TDI forums is whether to coast in neutral or coasting in gear. Of course you slow down a lot sooner coasting in gear.

If I have to stop I have figured out how far out I can coast clutch in to make it just right, or if I am in traffic how far out I can coast clutch out, no throttle. From the testing I have done it is better to coast in neutral at .2L/hr then coasting in gear at .0L/hr because you have to stay of the throttle longer leading up to a coast in gear (assuming a flat run out).

Unless you have just the right hill to gain no speed in gear and have to slow down anyway, I use neutral.

Just compare it on a KE+PE/top to KE+PE/bottom basis (I'm guessing it depends on the hill). You can calculate the difference in energy between the car's initial state, higher up on the hill, and it's final state, lower down on the hill. Compare these initial states to find out which car, in gear/no fuel or out of gear/little fuel, gains more energy from rolling down the hill. Since the car out of gear is idling, calculate the energy used while idling multiplied by the appropriate modifier for diesel engine/transmission efficiency, and account for it including it in the car that's out of gear's delta E. You could test this on a few different hills to get a curve of best fit, and approximate the grade where it becomes better to keep it in gear, or coast in N, barring of course speed limits. :thumbup:

Sorry, I first thought your reply was directed to someone else.

I have done no official tests on uphills but have been driving in the manner you describe by accelerating before and quite often during uphill climbs. I almost always do this on hills not too long, i.e., that I can see the crest. I am sure I have improved my uphill FE with these methods.

Longer climbs I get questionable payback for increased approaching speed. But during long climbs I will accelerate if my instant MPG drops below 30 MPG. When my SG II drops into the 20-30 MPG range, extra throttle does not lower the MPG reading substantially(when it's that low, how much lower can it get?). Quite often I can level off after acceleration to a higher speed and see much improved MPG readings for a time. I downshift only when absolutely necessary and when I do I will accelerate immediately to gain enough momentum to get back in 5th gear as soon as possible.

If you drive this way, I would like to hear your assessments.

Do you drop to the next lowest gear, or an even lower gear so you can accellerate better?

I always drop into the next lowest gear. I don't very often go lower than 4th. In the past, if I let my car pull way down 5th, it was also too slow for 4th to pull strong. Then I would use 3rd to bring it back up. I do not skip shifts often.

Keep in mind that I have a 130 HP 2.0 liter engine. But it may not be as different as it seems. At my 10,000 ft. altitude, I may be losing 35% of HP and torque. Actual barometer readings here are in the 21-23 in. Hg area, vs 29-31 in. Hg at altitudes of 0-2000 ft. What this means is that I have about one third less atmospheric pressure pushing air into the engine. Like a supercharger in reverse.

CO ZX2 -

Is there a way you can measure your "effective HP" at your altitude? I was using a tangential "Colorado Rockies" metaphor where, in Denver, a baseball can travel 10% farther in the thin air of Coors Field, 5280 feet above sea level.

Ok, maybe I can answer my own question. I just googled "engine horsepower elevation" and got these results :

Engine Tuner's Calculator
https://wahiduddin.net/calc/calc_hp_dp.htm

Using this in conjunction with weather.com, I got current "relative horsepower" assumptions for Denver to be 83% of rated HP, a 17% reverse supercharger in Denver.

Density Altitude Calculator - selectable units
https://wahiduddin.net/calc/calc_da_em.htm

CarloSW2

Carlo, Here I am trying to help anyone who wants help and you seem to have made it your life's work to repeatedly dispute anything I say. Review the responses you have made on my posts since I have been on GasSavers. What is the deal?

You are literally and actually a mile off on this one. Denver(5280) is near half of my altitude. I gave you my altitude (10,000feet). All you would really have to have done was enter my altitude (10,000 feet) into the calculator. For a guy obsessed with figures, how could you not have seen that in my post? Even so 10,000 feet may be a low average figure. I regularly drive over mountain passes 11,000-12,000+ feet elevation. I do drive to Denver occasionally but overall a small percentage of my driving.

Answering your own questions with careless factfinding is not very scientific. I raced in Denver many years and used NHRA altitude correction factors so am very familiar with them. I have spent endless hours running engines on dynamometers using altitude and weather correction factors for HP and torque.

I am not very sure of the validity of the baseball travel statement. I have heard it many times but have no idea where it got started. It stands to reason that thinner air would have some effect but I've never worried about it much. If you can make it into something that will produce more FE for me, I'll take it. CO ZX2

CO ZX2 -

I am not disputing anything you say. I already know that you are at 10,000 feet. You are reacting to this :

... for Denver to be 83% of rated HP, a 17% reverse supercharger in Denver

I am saying it is in Denver. I am not claiming it to be your location. Sorry for not making that clear in my post :o .

The reason I did not enter your altitude is that there are 4 inputs to the calculation. I did not want to make the assumption that the weather conditions in Denver are identical to yours, especially with a 1 mile altitude differential. Wouldn't you agree?

If I had plugged in your altitude, your estimate of 35% is inline with a doubling of altitude, aka 17%*2 = 34% reverse supercharger.

Question : Can you go to the website and plug in your zipcode/location and tell me the numbers you get? Also, can you go to the website and interpret the numbers for accuracy for me?

You know this stuff off the top of your head, but other people do not. The level of car smarts in this forum is great. That ain't me. I am just "Joe car owner". I have to do "unscientifical research" to find stuff out. I have to go "somewhere else" to learn and understand information that you know by rote.

I never knew the existance of "NHRA altitude correction factors" until you just posted them.

Thinner air implies less oxygen (to me) which implies lean-engine running (to me) "up thar" in the Rockies, but I can't prove it because I haven't done this stuff all my life. You have.

Dammit, Jim, I'm a programmer, not a race engine builder :D !!!!!!

CarloSW2

The a/f mixture will be corrected by the ECU via the O2 sensor - a modern engine won't run leaner in thinner air.

What it IS doing though is running at a wider throttle opening to generate a given amount of power (relative to a car at lower elevation), which reduces throttle/pumping losses.

Add to that the reduction in aero drag in the less dense air...

Add to that the mountainous terrain, likely forcing the engine into an even better BSFC zone under higher loads on the ascents...

And you have the makings for better than average FE, when driven correctly (which CO clearly knows how to do!).

Good one!

More silliness. And mistakes. Do you know Jim? I do not.

I have a sneaking suspicion that the above was a reference to Captain Kirk.:p

10,000 ft :). I wish I lived that high up!. I suppose, it shows the value of 3 things for good fuel economy:

(1) Driving style
(2) Aero mods (if you can't thin the air, at least you can reduce the resistance!)
(3) Reducing pumping losses (again if you can't thin the air). Unless you can get new cams made, this will have to be be increasing the throttle load.

By the way, a simple way to think about the engine on + idling or 'coasting in gear' argument would be...

- The engine uses a certain amount of fuel to idle at 750rpm
- If you coast in gear at 1500rpm, the engine will be 'wasting' more energy
in the form of engine braking. This energy originally came from petrol, so, by coasting in gear at 1500rpm, you are wasting more energy than by idling in gear.

The only real reason to coast in gear would be to slow your car down, without using the brakes, because there is a red light / junction etc up ahead. This is more efficient than idling + using brakes.

Something I have noticed with my new lambda sensor - the brakes run on vacuum, so, at idle (with the car not moving), if I press the brakes 3 times in a row, the mixture goes to 20:1 briefly (because the brakes are using the vacuum by letting air flow from the environment into the inlet manifold). When this happens, the engine runs OK, maybe *slightly* unevenly. I know that you do get a lot of NOx emissions with lean running, but would this be the case at idle?. If not, it might be possible to modify the mapping so that, at idle, the car runs lean and uses a lot less petrol (noting that diesel engines run very lean at idle).

diamondlarry -

NO NO NO!!!! My reference is to that guy from priceline that keeps trying to book your vacations for you! He also played the police chief on TJ Hooker back in the 1980's, and was in that Black and White Twilight Zone episode where the gremlin/monster was trying to destroy the engine and crash the passenger plane.

;)

CarloSW2

Oh yeah, now I remember.;) :D

My main hill is a 1000 foot climb up to the North Carolina state line. The 1st part of it is a steep 3rd gear climb for about half of the elevation increase, then a stop sign before getting onto US25, which is more gradual 4th gear climb. I used to maintain cruising speed (40mph) to the base of the hill, then go to 80% throttle and drop into the lower gears as my speed dropped off during the climb, coasting to the stop, then 80% throttle accelleration up to 4th gear on US25, then using the minimum throttle needed to maintain 40mph for the rest of the climb. But for the last few tanks I have been accelerating up to 55mph at the base of the hill then going to full throttle and dropping gears as my speed dropped off in the climb. So I am spending about half the time in 3rd than I used to. The rest of the climb is the same as before. Tank mileage seems to have improved by 1 to 2 mpg since I made this change. When Yoshi cranks up production of the MPG SuperMID, I'm planning to get one so I can get faster and more specific feedback on changes in my driving technique.

If you have the engine off, but you have it in gear, it will still generate a vacume in the intake manifold and you will still have vacume assist, for your braking need's. Another thing to keep in mind is that even if the vacume goes completely to zero, you still have braking, you just have to realllly stand on it to get it to slow down because of the lack of mechanical leverage you have lost, because of losing vacume.

I agree with you about driving in L.A. You need all of your car's capabilities fully functional 100% of the time with no fiddling around.

No more "bang" because there is no fuel in the exhaust to go "bang"!

Will someone please answer a question for me about the Scangauge? All this dependency on Scangauge readings causes me to wonder...how (if at all) is the Scangauge calibrated? Is there a calibration step? How? -Ted Hart :confused:

landspeed: 10,000 ft :). I wish I lived that high up!.

landspeed, This is beautiful country but I don't know a soul who lives here for gas mileage. I lived here for 10 years and just accepted the mountain climbs as part of my reward, never dreaming that FE could be accomplished to any degree. When I leave Denver, 75 miles away, and wind my way home, I climb over a mile in altitude. Not much 60-70 MPG there. If it wasn't for scenery it would be depressing if you let be.

Most people here are too timid, too lazy, too scared, too stubborn, and with a multitude of excuses to make any honest attempt for FE. I guess the same types exist everywhere. I would like to have the money spent on fuel for all the SUVs @ 8-10 MPG on this drive for just 1 day. Beyond that economy cars are lucky to get 20 MPG. All of them do very little, if any, better for FE travelling the opposite direction. Come on in. We have plenty of wide open spaces.

RTM, it does a trueup at fillup.

I wouldn't move there simply for FE, but it sounds like the kind of place I like (I'm from Scotland!). I have been to the US once before, to Georgia, and it wasn't really my kind of place, but I have seen pictures of the Rockies and it seems very nice.

The problem would of course be emigration - I work in medicine so I think I would have to do the transfer test (OK), but I wouldn't want to have to start from my junior years again :(.

here's the online manual. it the same thing you get with the scanguage.


https://www.scanguage.com/support/pdfs/SGIIManual.pdf

More coasting.
 

Yesterday we drove to a town we visit occasionally. 206 miles roundtrip by same route. I used my bottle level for the first time as a help in recognizing coasting opportunities. Level worked well for me despite some jiggling on bumps. Definitely accurate enough to help me pick coasting spots. I looked back on my records and this trip was by far my best MPG on this route.

I posted my bottle level and more explanation(post#5) yesterday on:
https://www.gassavers.org/showthread.php?t=2805

New coasting info. 3/15/07

I have had both my front fender skirts finished for a couple days. For the last 3 months I have been refining with left side only.

Link to front skirt project: https://www.gassavers.org/showthread.php?t=2173

Yesterday I drove the coasting route used in tests above. Coasting speeds were significantly higher at every point. Where I had braked twice before to stay close to 75 MPH, I had to brake 6 times yesterday.

When I reached the point where I had slowed to 30 MPH before, I was going 40 MPH yesterday. This extra 10 MPH allowed me to clear a rise at 32 MPH that I had never cleared in many tries at any speed. There was enough additional downgrade to coast another 3.8 miles till I slowed to 30 MPH.

This coast was 12.5 miles vs 8.7 in original test. These runs were Engine Off in neutral.

Reminder. Coast with Engine Off in 5th gear till slowing to 30 MPH in original test 5.1 miles. I did not repeat this run yesterday because of the obvious uselessness of doing so. Yesterday's coast was near 2.5 times as far.

Don't you think everyone should be Engine Off Neutral Coasting at every available opportunity? Even if you have to make your own opportunities.

CO - was there also a temperature difference between the 2 runs?

CO ZX2 -

Yes, but I had to deal with this today :

Attachment 266

This was probably under 35 MPH on the flat.

When I get my injector fuel cutoff switch installed (eventually), I will be able to use Engine Off in 5th gear to help me deal with this traffic.

EDIT : In urban traffic, where I think power brakes are necessary to avoid accidents, EOC in 5th means that I can save gas and have 100% working brakes. A (momentary) fuel cutoff switch will be perfect for this strategy.

CarloSW2

Metro. Temps were 3 degrees F. colder than first tests, 26 degrees vs 29. I had driven 20 miles to the test site so drivetrain would have been plenty warm. All else very much the same conditions. I have coasted down this same stretch many times and never made it over the rise mentioned.

Engine was shut off for the test so wouldn't have mattered there.

I don't know how cold it gets in the rockies but, around here when it gets sub zero temps the cars just won't roll as good, there is a pretty big difference too.
I don't know if its the tires or frozen grease in the bearings or a combo of the two.
I think thats why Metro wanted to know if there was a temp diff.

But ya, I agree with what you said ..


""Don't you think everyone should be Engine Off Neutral Coasting at every available opportunity? Even if you have to make your own opportunities.""

opportunities
 

I have been getting braver at creating "opportunities". I dont necessarily slow traffic, but I allow people to approach and trail for a few seconds before I bump start and gather speed.

I have been fortunite lately, most people have turned off the road soon after an approach or I get back up to speed.

I have been testing out EOC in many places now, and have found that I can coast in many places that I never would have thought possible. I definitely am getting familiar with moving slowly and the strange feeling in the steering wheel when the power steering pump kicks in.....

BeeUU wrote:" I definitely am getting familiar with moving slowly and the strange feeling in the steering wheel when the power steering pump kicks in."
Be careful here. I got a suprise when I was learning EOC on twisty roads. I was going a bit faster than I was comfortable with around a downhill turn, so I let the clutch out and bumped the motor to use engine braking. Anyone care to pause here and guess what happened?

The high effort unpowered steering suddenly became low effort power steering, and the wheel jerked quickly into the turn. Luckily I caught it, otherwise I would've spun the car.

I also want to thank CO ZX2 for this thread. Message received. :)

Yep, the first time was interesting, I thought it was the snow tires loading up, plus it was wet, I thought it might have been ice, it was a bit of a surprise. But it seems to be the pump starting. I am fairly lucky, the effort level is not that much different at speed, at least with snow tires. I am not sure what it will be like with the autocross tires installed. :eek:

Yes, for sure!! Good to hear the aero work is paying off!!

On-Ramp Surprise
 

The first time you have to re-start in a corner is a bit of a surprise. There's a long downhill where traffic loads-up before an on-ramp. I can usually EOC for quite a while on the downhill (usually having to brake as traffic loads-up).

Then, on the ramp itself is when I have to start back up. The first time went from effort to a quick jerk in the wheel (mid-ramp). Luckily the suspension is pretty neutral, so it just slid and corrected :whew: I usually start-up before the turn begins, now :rolleyes:

That's good to hear. If it had been warmer, I would have wondered how much the different rolling resistance from the drivetrain (temperatures of wheel bearings, CV joints, transaxle oil, tires) had contributed.

yup it will, especially if you have a mechanical fuel pump (like my vette) since its run off the distributor, if th eengine is turning the fuel will spray, flood the engine possibly hydrolock:(