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#1
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How much fuel is consumed on a start up?
I drove to a party last week with a friend. The car had just over 1/4 tank. We drove 50 miles total, there and back. When I got home, I noted that the fuel tank was now right at 1/4 tank. The next morning when I started it, it was just under 1/4 tank. So, how much fuel is used at startup? Even if you don't know the exact amount (1/2 cup or whatever), maybe you know it's "the equivalent of 10 minutes of driving or whatever.
Also, I know they say "if you're stopping the car for a few minutes, best to just let it idle". But it doesn't really say how many minutes. Thanks, jeff 1991 300d, 117k |
#2
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Startup on an injected car, gas or diesel uses very little fuel. Probably somewhere on the order of 1-2oz (just off the top of my head) or less.
Someone did calculate it out one time and found that if you're going to sit at idle for more than 10sec, it more efficient with modern injection systems to shut off the engine. Older injection systems like the W123 are still very efficient and probably don't use any more at startup than their younger cousins. I would just turn off the engine if it looks like I'm going to sit for more than a minute. I perfer not to shift into park, shut down, glow, crank, shift to drive. This might frustrate other drivers at stop lights. |
#3
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if im in a drive through or something i put it in nuetral, shut it off, turn it on, drive, go
no need for glow plugs if its already warm
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1981 300SD 512k OM603 |
#4
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How many seconds are you cranking it?
If it starts in one second, you'll use about one teaspoon of fuel to start it (my WAG). Longer crank times use more fuel. |
#5
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True, I'm just anal.
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#6
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What more likely happened is that the fuel in the tank warmed up and expanded a bit over those 50+ miles of driving and then cooled off (contracted) overnight, resulting in the lower gauge reading in the morning.
Thats why some fuel stations heat the fuel on the way out the pump so it expands and they sell ever so slightly less per gallon, saving them big $$ over time. I was at a station like that once....the nozzle and hose warmed up right away when the fuel started coming through....I thought it was very odd.
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-diesel is not just a fuel, its a way of life- '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k) |
#7
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This is an interesting question. If you are just considering starting an engine its not very much. However if you are trying to compare how far you can drive a car that has to be started and not up to operating temperature to one that has be running a while and warmed up on the same amount of fuel I would imagine there would be some measurable difference. Your engine contains a lot of metal, water, and oil to heat up.
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green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons ) white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank) desert storm primer 63 T-bird "The Undead" (long term hibernation) http://ecomodder.com/forum/fe-graphs/sig692a.png |
#8
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On the W123s there are no sensors to determine engine temperature to affect mixture. No "choke" equivalent for a diesel. No cold start injector.
Engine will use as much fuel during the starting process as it will use during the same period of time at idle in other words. Whether it burns it is another question, but it's still injected. Theoretically it's actually less, as cranking rpm is less than idle rpm and injector pump action is directly proportional to rpm.
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Kent Christensen Albuquerque '07 GL320CDI, '10 CL550. '01 Porsche Boxster Two BMW motorcycles |
#9
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It takes my fuel guage to wake up in the am. She takes ~3mins to get up to where she left off the day before. She's 180 years old in car years!
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82 300D....went to MB heaven 90 350 SDL....excercising con rods |
#10
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Yes, the fuel gauges aren't very precise really. Maybe you park on a slight incline as well?
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1985 CA 300D Turbo , 213K mi |
#11
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Quote:
I am sure there is a sliding scale on "year computation" and for the MB my cars are only teenagers at best... I would say 2 to 3 years to each "car year" not the other way around like dogs...
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#12
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I do know this, my car uses about 3.5 ounces of fuel at idle, operating temperature every 10 minutes. You could figure up the startup usage by using an extremely accurate measuring cup as a temporary "gas" tank and marking the before and after of startup.
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1981 Mercedes-Benz 300SD ~285,000 Miles |
#13
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Isn't the rack held at full fuel while cranking? Those few revolutions at full fuel could equal a good amount of time at idle.
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Dale http://i52.photobucket.com/albums/g1...MG_2277sig.jpg 1990 300D 2.5 Turbo -155k 2000 E430 - 103k 2014 Jeep Grand Cherokee Ecodiesel 4x4 - 11k 2014 VW Passat TDI SE - 7k Bro's Diesel 2006 E320 CDI - 128k Pop's Benz Pre-glow - A moment of silence in honor of Rudolph Diesel |
#14
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Ara T comes close to the explanation here.
Fuel gauges are thermal devices - they read higher when hot. The temperature within the cabin is important, and a fuel gauge will read less on a cold morning. Treat pointers on the dash of most cars as a vague indication at best - to call them instruments is a travesty. |
#15
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Fuel gauges are voltmeters. With a fresh start, the (car/gauge cluster) voltage could be lower or higher than when you shut it down.
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Gone to the dark side - Jeff |
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