Too much of a good thing --15 minute gravity drop

[user removed]

A block heater will also make a big difference in your engines operating temp on that long downhill ride. If you can get the engine to operating temp the mileage should climb dramatically, especially if you can not get it up to operating temp otherwise.

Even idling the fuel consumption would reduced by probably close to 70%.

DFCO will probably kick in much sooner.

This is based on the assumption that you are not able to get the engine up to operating temp before you get to the bottom of that considerable grade.

regards
Mech

[endurance]

Mech,
It's definitely high on my list for a number of reasons. Since I live at 7400', winters can be pretty harsh and waking up to sub-zero (F) temps is not all that uncommon. Even if I didn't elect to hypermile, the engine on the Acura going downhill in cold air takes at least five minutes to reach sufficient temperature to put out enough heat to start defogging/defrosting the windshield. I can't safely drive without a 5-10 minute warm up unless I can park in a garage and have a block heater that can kick on an hour or two before I get up. The mileage benefits are definitely a bonus.

Unfortunately, winter also means the Hakkapallita snow tires have to come out or it'll be a one way trip down some day in November and I won't be able to get back up the hill until sometime in March. My snows and winter fuel usually cost me 2-3 mpg, but hopefully my new techniques and mods that I'm learning here will still mean I get respectable mileage (34+, I hope). It's a 62 mile a day round trip (10% city streets, 60% highway (about a quarter of which is subject to stop and go traffic, especially in the winter), 30% mountain roads), but the gravity drop is kind of the ultimate pulse and glide. I do 15 minutes of continuous glide on the way to work and 15 minutes of continuous pulse on the way home.

This will be our first winter up at the new place, but I've lived in Colorado for 30+ years. The GF (from Texas) is convinced we'll be fighting over our one lone 4x4 truck on the snow days, but even after a four year stint living and working in Summit County, Colorado (ski country), I remain unconvinced that four wheel drive is necessary 360+/- days a year. I have a job where I can choose to work from home four out of five weeks a month, so unless there's a cosmic convergence of a mega-snowstorm on the one week a month I have to be at work and the GF just happens to need to go to work that same day (she only works 3 days a week), I think we'll be just fine.

[Frank Lee]

I wonder if there's an appropriate non-power brake master cylinder that could be swapped in. I know on several of my cars there is.

[Mustang Dave]

Originally Posted by euromodder

On my car DFCO works right away.

Same thing with my truck. Diesels have always had DFCO, regardless of temperature.

[user removed]

Tactically I would consider letting the engine idle when you can and using DFCO when necessary.

Trying to balance keeping the engine at operating temperature (just barely) with idling and DFCO (which will cool it off and make it run more rich).

Engine off will just make it drop below operating temp which will bring on enrichment. In essence an additional cold start.

Minimise cabin heat as much as possible without risking your safety and some semblance of comfort. Recirculate the heat if you can without excess window fogging. Fresh air requires much more engine heat to get it hot enough to be effective in extreme cold.

You objective should be to balance DFCO and idle to create just enough heat to keep the engine warm enough to operate without enrichment.

A scangauge will give you the fuel consumption data to verify your fine tuning your tactic. It may even be better to use lower gears for shorter times, versus higher gears for extended periods of time, since the longer periods of no fuel consumption could get your engine temperatures to low and increase the mixture.

It is a fascinating scenario, where the eventual tactic may be somewhat unusual. Your idle fuel consumption is probably in the range of .16 to .22 GPH. Make sure the idle speed is as low as tolerable. If you can average 50 MPH with 1/7 gal per hour consumption, you are getting 350 MPG. While not as good as infinite, you will do better when the grade levels out and you have a warm engine. It's a balancing act where you burn the least fuel to try to keep the engine warm.

How long is the downhill ride as far as time?

Keep us posted as to your progress.

regards
Mech

[busypaws]

Hey guys we have to better then this for the man. He has to beat the MPG of the Jetta TDI coworker. That much elevation change has to allow some evil mechanical/electrical gee-whiz thing get him better mpgs.
1) Can we think of some pressure vessel that doesn't weigh anything that sits in the trunk and "breaths-in" on the downhill and "breaths-out" on the uphill that generates heat and or electricity.
2) Or a way to install regen breaking on the downhill which again generates cabin heat or recharges the battery.
3) Flywheel?

Once you've gotten a realiable system (2) that generates electricity or heat on the downhill then you can add weight (Take out trash, fill a 10 gallon container with water, etc) that you take downhill with you every day but don't bring that weight back up the hill.

That is just half the ideas. The other ideas involve sabotaging the jetta to get worse miles (Nothing serious - just make him drive to lunch on those cold days so he has more cold start/short drives, etc).

[endurance]

It's about 13-15 minutes and about 9.5 miles. The first 3.2 miles is driveway filled, deer covered, twisty stuff, the rest is mountain highway until I get to the interstate where I have to start climbing for about 5 miles, and then have several .25-1.5 mile coasts all the way into work. The return trip only has the one 5 mile sustained descent, which is interrupted with several flats. I know if I could discipline myself, it really does provide an excellent hypermiling commute. I'm still struggling with driving slower after a lifetime of 70mph highway driving, but I understand that speed kills mpg.

I just received and installed my scangauge tonight and while I was picking it up from my P.O. Box, I started chatting with the owner of the store about hypermiling. I mentioned needing some PVC for covering my lower grill and he mentioned that he always had the material around for making business signs. One thing let to another and I walked out with a 6"x36" piece of 1/8" thick PVC that will perfectly cover my lower grill for free! Stopped by the hardware store on the way home, picked up a normally on momentary switch, some spades, an inline fuse, some steel for manufacturing brackets for the PVC, and I think I'm set for weekend projects. I'll call my Honda dealer and make an appointment for the block heater next week. I also cleaned out one side of the garage tonight enough to get the car in, so that should help a little in the meantime until I can get the heater. Of course, if I don't get another side cleaned out before the GF moves in, she'll get dibbs on it and I'll be back outside.

[endurance]

Originally Posted by busypaws

That is just half the ideas. The other ideas involve sabotaging the jetta to get worse miles (Nothing serious - just make him drive to lunch on those cold days so he has more cold start/short drives, etc).

The Jetta is already sabotaged worse than anything I could ever do; it's driven by a 20 year old. Nothing kills mpg faster than a college kid with a turbo.

[endurance]

Well, after a a week with the Scangauge I've learned a lot. First off, I've been simply using DFCO for braking and brake assisting on my gravity drop and letting the engine idle while coasting. When I start the car cold in the morning I'm using 1.3 gallons per hour, which eventually drops down to .27-.43 depending on what accessories I have running. I quickly added a lower grill block because I found that even when I started with a warm engine (177F), using DFCO intermitenly with engine on coasting and the cool outdoor air I could watch the temperature drop to 152F by the bottom of the hill. If I started with a cold engine, it would never make it up to 150F, no less full operating temperature. Now with the grill block and outdoor air temps near freezing, it is managing to get up to and stay in the 155-175 range.

I discovered there isn't a block heater available for the car (the only one manufactured only fit the 02 RSX and was discontinued in 04 or 05), so I'm going with a lower radiator hose heater. It'll be an easier install anyway. What about a magnetic oil pan heater, too? Redundant?

Also on the list now is a garage door opener. The garage has too big of a lip at the door to push it out safely (risk getting my legs chopped off if I'm in the door and pushing), so I have to start the car, drive out, turn off the car, get out, close the door, get back in and then bump start it going down the driveway. Seriously not worth the hassle...

I paid for three days of access to the Honda Helm site to download all the wiring diagrams I need to cut off either the fuel supply or the crankshaft position signal. It'll probably be a week or two before I can get the time to do it, but it's on my list.

I also picked up a used vacuum pump on e-bay for $20 and with a PVC vacuum storage canister, I should be able to have plenty of full power braking for EOC mountain driving when DFCO isn't the best technique. It'll be a winter project I'll get to sometime.

Also, I'm considering going with LED lighting to save my battery some. Still seeking out viable headlight options, but I used to build my own bike lights for 24 hour mountain bike racing, so I suspect I'll end up creating something on my own (my last light build put out over 730 lumen, but could go for over to three hours on one relatively small lithium battery). I have plenty of high output LEDs just sitting around. I also have my metal mill if I really want to get medieval on it.

Overall, I just wanted to say thanks for all the input. My last tank was my best tank ever (36.5mpg) and while I've been struggling with this tank because of a couple of hideous commutes (rushhour traffic snarls), I'm still probably managing over 32mpg (can't trust the scangauge mileage yet, as I haven't calibrated it with a full tank cycle yet). I've definitely gone down the rabbit hole and I have you guys to thank.

[busypaws]

Before you dive into LED headlights go here and order LED lights for all the side/tail/brake lights: Super Bright LEDs ? LED Lights, Bulbs, and Accessories Won't save nearly as much as headlight LED's but its a 10minute order online and then a 15minute change out in the garage one night. When you put the front side lights back in then tape/caulk/seal around to make them more areo.