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Old 12-15-2009, 05:10 PM   #21 (permalink)
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Originally Posted by dcb View Post
LOL, did my post make any sense?
Yeah, sort of. In between my original post and the edit is when yours appeared. I need to tap faster.

I see the graph. Mine is the ASZ version of that engine (130hp) but probably similar. Not sure about the full throttle thing though as that would surely just mean unburnt excess fuel (Diesel = fuel controlled) and in any case the turbo would kick in and I would be at 2500+ before I know it.

I shall experiment with the highest gear approach though, part throttle enough to maintain speed or bleed it off enough to get to the top and then coast down. I don't EOC as my steering and brakes don't work well with no engine.

EDIT : Reason for my post is I'm kind of living of the instant MPG reading and its painful watching it hit 25 or less when going uphill vs --- (i.e. infinity) when going down.

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Last edited by Arragonis; 12-15-2009 at 05:16 PM.. Reason: More info
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Old 12-15-2009, 05:15 PM   #22 (permalink)
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there is less return on EOC for a diesel, but clutch/neutral coast will carry you farther than coasting in gear.

I don't have reason to believe full throttle on a small smart diesel = proportionately more unburnt fuel, otherwise my bsfc peak would not be sitting on the torque curve.
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Old 12-15-2009, 05:32 PM   #23 (permalink)
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As I learned it, lugging is defined as the point in the engine's power curve where it doesn't make enough power at full throttle to maintain your current vehicle speed. This would make the lug-point dynamic, not static.

I follow this rule, except at 80% throttle in gassers. (Unless they're GDI, then 100% is OK.)

I've never heard the definition regarding the use of carbs at all, and I find it unlikely, since diesels also suffer from lugging issues.
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Old 12-15-2009, 06:52 PM   #24 (permalink)
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The best way I've found (automatic transmission) is to have speed when you start the hill and bleed it off a bit as you climb the hill. Letting go of the gas completely JUST before the peak and coasting all the way back down.

This method is almost as good as a level straight.

Yep this is the same technique I use as well but I think the hills here are not as frequent or steep as those in West Virginia.

A "get momentum working for you" approach is the best option if the hill allows it but where it is along haul then drop into a lower gear earlier and maintain as much as you can.

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Old 12-16-2009, 11:23 AM   #25 (permalink)
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Originally Posted by dcb View Post
But that is where I make the most power for a given amount of fuel on my tdi. Start gliding prior to the peak so that you glide crawl over the top and reduce need for braking as appropriate.
from ecomodders very own wiki (which anyone can edit/contribute to) Brake Specific Fuel Consumption (BSFC) Maps - EcoModder
I can believe that chart to be accurate for the VW 130Bhp engine. We too have a Skoda Vrs and I can feel the engine become more torquey and efficient in the range of 1,500-2,500 rpm. This is borne out by the instantanoius mpg reading climbing rapidly once 1,500 rpm is breached.

A standard rule of thumb used to be drive within the range of peak torque +1000rpm -500rpm for best efficiency. Under light load lower revs can be used without the engine bogging down. I'd be wary of running high loads at low revs in a diesel as that can create very high forces on the big ends and crank.

For hills I use the 'arrive a bit quicker and let speed bleed off slowly' technique.
In the Vrs one needs to be careful to not be in too high a gear under load, it seems to increase consumption.
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Old 12-17-2009, 03:07 AM   #26 (permalink)
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One other issue doing this in the UK is traffic volume, quite often people just don't like following someone driving with load or doing the rollercoaster. In my view they should just leave a long gap (I do this to break up jams often) but I'm usually in a minority.

I shall experiment further, there are plenty of hills to try.
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Old 12-17-2009, 08:35 AM   #27 (permalink)
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Originally Posted by Arragonis View Post
One other issue doing this in the UK is traffic volume, quite often people just don't like following someone driving with load or doing the rollercoaster. In my view they should just leave a long gap (I do this to break up jams often) but I'm usually in a minority.

I shall experiment further, there are plenty of hills to try.
The roller coaster is most efficient for the professional driver who makes a living hauling loads. Reducing fuel cost means money in their pocket.

On I95 between Richmond and Washington DC, the truckers will do the "roller coaster" with speeds ranging from 53 to 75 MPH in a 65 zone. Leaving stopping distance (3 stripes x 43 feet) between us is my favorite position on that road in heavy traffic. The road is 3 lanes each way, and if you get in the inner two lanes the aggressive drivers treat it like a NASCAR race, with separation distances measured in feet and passing proximity measured with a yardstick.

Instead of trying to impose my desire for better driving habits on others, I just pace myself behind the trucks, which generally stay in the right lane.
This also gives me an escape route to the right, where the shoulder is paved and as wide as either of the three lanes available for traffic.

The hills around Fredericksburg are of sufficient grade to allow coasting (in neutral-engine on) at speeds of 70+, and in some cases you even need to use DFCO to keep your speed down. While you may see only 25 MPG on the uphill section, on the same hill's downhill section the mileage can exceed 300 MPG.

Doing this achieved the highest single trip mileage I ever recorded in my VX, over 68 MPG, at an average speed on 64 MPH. May of 2008 when fuel cost here were approaching $4 per gallon. Two passengers and cargo with a total weight of about 500 pounds.

I prefer alternative routes to the above mentioned scenario, but at night, the greatest danger here is Deer running out in front of your car. A friend once hit a Deer and it came through the windshield of his van. They had to open the door to let the Deer out.

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Old 12-17-2009, 05:45 PM   #28 (permalink)
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I agree - except being in Scotland most roads are 2 lanes only - so nowhere to hide and not be annoying.
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Old 12-17-2009, 06:40 PM   #29 (permalink)
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ok, well in answer to the original question (and the title of this thread), it is as I described, load up the hill at bsfc peak and glide down and glide crawl over the top so you brake less.

Maybe we should change the thread title to "Hills (most efficient climbing technique for diesel / manual transmission after I put a whole bunch of conditions on it)"
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Old 12-18-2009, 03:03 AM   #30 (permalink)
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Does it make a difference if I'm wearing glasses ?

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