Question about the math for EOC vs Coast?
 

I've been trying to figure out what the benefit of EOC is without actually trying it.
The math I have done is based on my commute. 400 miles a week, average speed is 45 mph and my last three tanks average is 40.45mpg which approximatly equals a GPH of 1.11.
I Coast with my engine on for approximatly 10% of my one hour drive (6 min.). My normal GPH while coasting has been 0.22. So If I subtract the gallons of gas saved via. coasting (0.22gph vs. 1.11gph) then the mpg if I didn't Coast would be 36.9mpg and my average gph would be 1.22.
So lets say for the same 10% of time driving my engine is off (0.22gph vs. 0.00gph), then my mpg would be 41.56 vs 40.45 that I am currently at.

To sum up the math, if it is correct. It seems that Coasting benefits me by 9% and EOC could benefit 11%, or just 2% better than Coasting.

Does any of this make sence? It seems correct to me?

you also use a little gas on restart ,dont forget to factor wear and tear on starter/flywheel ,,your math makes sense,, to me though.

Your math seems sound to me as well. I say it's pretty clear: you burn a gallon of gas a week idling. Install a kill switch and pick up that slack! You'll save $150/yr.

Besides, it's very relaxing to turn off your engine and roll up to a red light with no noise other than that of your tires. It also removes the pressure to get away from the light in a hurry, since you're burning zero fuel sitting there.

My starter is a hit and miss unit right now, when that is addressed I intened to expirement with the idle issues. I need to track the time idleing up to and at stop lights and do some math. I have about 12 stoplights each way going to and from work. So that is 120 stops a week and the associated idle time. I currently coast up to stop lights.

I thought it was interesting that EOC is only slightly better than Engine On Coasting. So I guess ATX's don't suffer as much as I previously thought.

Do you have to stop at every light?

My daily trip is close to 52 lights, but I seldom have to stop for more than 6, sometimes less than that.

I agree that enigne off coasting can save you money in fuel, but I think it might cause you to have other repairs that offset the savings.

In my VX lean burn is disabled for something like 30 seconds on every restart so it will not help me to do EOC in the VX.

regards
Mech

I commute thru Philadelphia and on congested roads, I do my best to minimize stopping, timing lights and such. The number of stops is an average, I pass thru many more stop lights, that's just the number of times I usually stop.

I'm not too concerned about EOC causing any undue repairs. I've already got 265,000 miles, so there's plenty of time spent PM'ing this car anyhow. I have a set budget and can opperate within it pretty well and have enough latitude for major repairs if they arise. I also do all the work myself and that saves a tremendous amount of money. I also shop at the U-pull it yards for parts off good wrecks.

Maybe I'll work on a spread sheet to calculate the wasted gas/potential improvement from not idling at stop lights. I've made an eccel spread sheet for the EOC vs. Coast. If I can refine it a bit with real world results I think it could be helpfull in further refining my commute and where the best times to coast or keep the power on.

Also, is this picture some sort of record for Idle GPH in a gas motor :D I'm amazed at how low the idle gph can go under the right circumstances...

Ok, I calcultated that if my average Idle Time at a stop light is 30 sec, 24 stoplights per day and 0.22 gph. Then that would be 1 gallon of fuel per week. If I were to turn the motor off instead of idling, then that would be a 1mpg gain or 2%. I believe these numbers are high, I will have to take a stop watch with me for a couple days to see what the actual is...

I am going to buy a stopwatch too. ��
Sorry, but I have a Really basic question: My understanding is if you're likely to idle for more than a few (10?) seconds, turn the engine off. Is that about right?
I have two lights on my commute that are easily a minute so that's obvious. I either go around them or turn my engine off and relax if I see them turn red. Now know I can safely coast up engine off. Learning just how awesome this VX can be even at 267,890.

It really depends on your engine size. Tbh I EOC if even for a few seconds.

An MPGuino has a parameter that tells you how much fuel you've burned while stationary. For my commute it was just over 1 gal for every 270miles. This is only with the car 100% stationary, not counting the potential savings of EOC up to a stop. I have about 24 stop lights too.

Just to clarify, from your sig badge thing, I presume you are testing these options with an automatic transmission, correct? EOffC is something I have toyed with in my Taurus, but frankly with the column stalk shifter, i am burdened with the fear of bumping past N to R (*MENTALHORROR*), so I have just let that idea drift off. Additionally you're also placing a huge increase in the usage of your starter as the auto trans' obviously can't bump start.... Now for you with the tunnel stick you have a little finer control to avoid bumping into R so that works, but the starter wear question arises, as does the flywheel as mentioned by others.

Doesn't your car have some kind of lockout that makes it hard to accidentally shift into R? My Odyssey does. You can push and pull the shifter between N, D, D3, and D2, but to go into R you have to pull toward you as you move it. My sister's Camry has a button you have to push.

I estimate I spend about half my driving time EOC coasting. My commute takes 30 minutes, so 15 of that is coasting. My car idles at 0.22 gph. That's .055 gallons each way, or 0.11 per day, or 13 cents. Times 21 work days per month equals $2.73 / month, or $32 / year.

That's only counting commuting, not extra trips.

I spent $387 over the last year on gas, so EOC is saving me roughly 8% in fuel costs.

I wouldn't do EOffC in an automatic tranny. That will damage the transmission and put wear on the starter. In the owners manual for my Civic, it says that the transmission can only go 50 miles while being towed in N with engine off. So if you EOC 1 mile per commute trip, then you only have 25 days before the transmission starts having problems, according to the Manual.

I EOnC with my Civic at 10-45 MPH because it can coast really far at those speeds, and that is most of my commute to school (going home I take the freeway because there is no traffic and believe I get better mileage going that way).

No no no. 50 miles at a time. if you need to go farther you have to start the engine and run it a bit and shift through the gear positions, to re-lubricate the transmission. Then it's good for another 50 miles.

1 mile is way below the threshold, at least on Hondas specified like yours. My Odyssey is the same.

Oh, thank you PaleMelanesian, I had no idea. Then I guess the only wear on the car will be the starter for EOCing in an auto.

Not if he clutch bump starts.

Speaking to those of you who have bump started for thousands of miles, does it seems not to affect the durability of the transmission? My owners manual specifically states not to push start it, and it's been years since I've kept up with auto tech so I didn't know if anything in manuals has changed to make it a bad idea, or if they were just covering liabilities.

When bump starting a cold engine unburnt fuel may enter the cat, which would shorten it's life. It shouldn't apply to hot engines. Chances are if you EOC your cat isn't getting up to temps anyway, though I don't think anyone here has actually had a cat failure from EOCing.

Most cars will go open loop after you key off and restart.

This means the next pulse happens in open loop. Since the car's already in open loop/ enrichment should I just floor it? This method means I only need to pulse for maybe 5 seconds.

The alternative is to drive at low load while in open loop, however, it takes about ten seconds to switch to closed loop, so that means 10 seconds of at say 40% load followed buy the real pulse of 100% load once it goes closed loop.

I think the first method is actually more effective. I don't know how long my cat will last though as I've already got a cat low temp code at ~3000miles from new. I assume running in open loop all the time won't help it?

It might just be about liability. You should research it further. I have been bump starting for about 60,000 miles now. Both the transmission and the CAT are fine, though I did swap the trans for taller gearing. Each trans has about 30,000 in bump starts on it. Neither has been compromised by it, to my knowledge. Both are old transmissions with mild shifting issues and some needed replacements like seals, or bearings, or maybe a syncho could use replacing because shifting has gotten clunky in a place or two... totally normal kinds of wear for transmissions with 100,000 or 200,000 miles on them. As importantly, there are lots of other people here who have been doing this a long long time without incidents.

But you should research your car and the reasons for that warning before you attempt it, would be my recommendation.

james

My Civic's transmission and clutch were just fine when I retired it at 200,000 miles, 50,000 of that being super-bump-start eoc hypermiling. I only have 20k on the Fit now so I can't say one way or the other.

The Civic would go into Closed Loop mode almost immediately on a bump start. The Fit isn't so generous, taking ~5 seconds of Open Loop before it switches. I try to do longer cycles because of that - more closed loop time during a longer pulse, and then I coast longer.

A good bump start is very gentle. It shouldn't be much stress on any components. It's a 2-step process for best smoothness. Use top gear, or 4th if you're below 10 mph. Lift the clutch just until it brushes contact, then push it back down while the engine spins up. Then choose your gear and shift like you normally would.

Now we are starting a new parameter, worrying about the life of the CAT.
Hmmm, most of us drive at low RPM's/low engine demand, just that is trouble for a CAT! CAT's need high temps to work more proper, no?
:confused: