Going up steep hills- downshift or floor it?

[PaleMelanesian]

Another trick if you don't have a gauge. Find the point where, if you push the pedal more, it doesn't give you any more power. That's your 100% throttle position. It's usually not all the way to the floor. Then back off to 80% of that.

[taco]

i found out in my 98 4x4 taco, that i could get about 2-4mpg better up a hill in top gear, flat to the floor bearly holding speed, then dropping down to 4th adn holding 1/2 throttle.

[99metro]

Oh boy Pale~, looks like I am going to have to experiment on my long hills a bit! I've been doing steady state @ 40 mph in top gear on THE HILL. I'll have to switch over to fuel consumption on the Scangauge and see if that works. Is it time to go home yet??!!

[womprat]

Originally Posted by tumnasgt

I find in my 2.2L Camry that it's better to change to 4th, as there isn't a huge amount of torque. I change my shifting point (steep inner city hills - such fun) so I stay between 2000-3000rpm, rather than my normal 1000-2200rpm, if my revs go below 2k I don't have enough torque to keep the same speed, so I have to floor it to stay the same speed vs half throttle in 4th to speed up slightly.

So you're in Wellington too eh? Hypermiling is for flatlanders in countries with wide open space it seems.

I find simply the best economy up a hill is getting as close as possible to whatever RPM + throttle opening offers the best efficiency, and of course you want to keep speed down so you not pushing too much air either. If your car does best FC at 60-70kph, then depending on the hill and your car speeds as low as 30kph might be ideal.

Staying in the 2000-2250rpm range around some of our steep hills and this seems to have dropped my FC on my commute.

[tumnasgt]

Originally Posted by womprat

So you're in Wellington too eh? Hypermiling is for flatlanders in countries with wide open space it seems.

I find simply the best economy up a hill is getting as close as possible to whatever RPM + throttle opening offers the best efficiency, and of course you want to keep speed down so you not pushing too much air either. If your car does best FC at 60-70kph, then depending on the hill and your car speeds as low as 30kph might be ideal.

Staying in the 2000-2250rpm range around some of our steep hills and this seems to have dropped my FC on my commute.

Unfortunately, Boulcott Street is the hill I have been going up the most lately, and with 2 sets of roadworks in that tiny stretch, I'm almost always accelerating up it as well. I got 33MPG (7.1l/100km) on my last tank, so I must be getting something right, but I suspect going up hills isn't it.

[mwebb]

if the 1995 audi a6 is OBD2 compatible
it would have the Hitachi ECM and those only had one line of scan data available at a time

so scangauge2 will not function on that car .

you can put the transaxle in neutral and coast down long hills
clutch released
and that will improve fuel economy

with the MAF sensor , WOT will provide the lowest suction throttling loss , but you do not want the system to go to open loop fuel enrichment , so
you could connect a DVOM to the 02 sensor signal wire
which is the black wire at the 02 sensor
and drive the car

up hill
when the system goes to open loop fuel enrichment , the 02 sensor will pinn at around 850 mv , so use a throttle position that is just slightly less than that value .
you want the 02 sensor to be cycling with the most open throttle possible .

the MPGuino will function and provide real time FE values with your system and it costs 1/3 the price of a scangauge2

[battlewagon]

I always upshift when going uphill. I think that makes the most sense because it allows the engine to operate in the part of it's powerband where it most efficiently makes power. This is all in theory, but it seems like it will reduce the load on the engine.

[Thymeclock]

Anyways, my question is, on the really steep uphills, is it more beneficial for my FE to leave it in 5th, and put the accelerator to the floor in order to make it to the top (usually at/around 30MPH at the top), or downshift to 4th or 3rd and not have to put the pedal to the floor?

30 MPH in 5th gear? I'm surprised you are not lugging the engine. (Or, maybe you are?)

What is your RPM at that point?

[almightybmw]

I recently borrowed my friend's manual Infiniti I30t for a trip (my AC was broke, and 12 hours with a wife at 90*F is a no go). Fun car, sucks fuel. It'll do 25mph in 5th, at 1000rpm. Cruising on the highway at 75mph (I-90 limit in MT) its around 3200rpm. On a 8% grade, I can still accelerate uphill at that speed, or back off to say 60% throttle to maintain. Over 2300 miles it average 27mpg. If it had at least 500rpm decrease in 5th I'm sure it could break and hold 30+mpg. If I hadn't left it in cruise 95% of the time, maybe coasted down the passes, I could have reached 29mpg on some legs of the trip.

Some cars just weren't built for mpg, they were built for fun. The motor has plenty of power to be geared for mpg as well as mph. I'm sure it has a crappy top speed because of the short 5th ratio. Don't worry, its never been above 110mph (to my knowledge).

Random rambling aside, I pretty much let the cruise manage the throttle up hills and mountains (1500-3000ft elevation gain). Most the time it would push it to what felt like 60-80% of total throttle, as I still had room left to accelerate uphill. Only once, at 60mph, 6% grade, did it completely floor it to 100%. Because of the short gear ratios, 99% of the driving this car did, does, will do--never needs downshifting, the engine makes enough power because of the higher rpms. 5th gear at 2000rpm is 51mph. In my GP I'm doing 70mph at 2000rpm. hmmmm...

[skyl4rk]

Try to keep your rpm's low, under 2200 rpm, more or less. Adjust the pedal based on the amount of power you need to keep moving up the hill, but don't floor it all the way. If your rpm goes down to the point where you are not getting power, downshift. Try to crest the hill at the lowest speed possible (as traffic allows). This takes good timing and judgment to know when to throttle off and try to coast over the top, creeping along at the peak of the hill, then rollercoastering your way down.