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reluctantartist
Samba Member
Joined: August 13, 2006
Posts: 1927
Location: Bloomington, IN
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 Posted: Sat Nov 22, 2014 7:18 am Post subject: Mpg when using heater |
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What kind of mpg should i expect if I am using the gas heater alot say 70% of the time? I think my city mpg went from 18 to about 11-12 mpg. Do I need to check the fuel flow on the heater.
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them. |
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bb412
Samba Member
Joined: June 30, 2004
Posts: 300
Location: canada
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| Posted: Sat Nov 22, 2014 10:25 am Post subject: mpg |
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| the Heather use appx. one or 2 quart by hr,, if the motor run or not running,, |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Sat Nov 22, 2014 1:28 pm Post subject: Re: mpg |
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| bb412 wrote: |
| the Heather use appx. one or 2 quart by hr,, if the motor run or not running,, |
No...that is PINTS....not Quarts......and only if the heater is running rich....which is not always a bad thing withjn reason.
Factory settings for the metering pump are 9-10cc per minute of running.
Typically in weather down in the teens and single digits at runnjng speeds.....if your fans, beating vents snd seals on the heater box valves and accordion tubes are in good shape.....the heater even at full thermostat setting should only be firing about 60% of the time to produce very excellent heat. Its should not run non-stop.
So typically on highest heat setting it should run at factory settings for about 38 minutes out of every 60 minutes.
This equals out to about 12-14 fluid/oz of fuel per hour. I have found over the years that to get good steady running and cycling that you want the heater slightly, richer than the factory spec. About 10-12cc per minute works well. This equals out to about 1 pint per hour with about 60% run cycle.
Even if you run non-stop.....60 minutes at 10cc/min factory settings is only 600 cc/hr which equals about 20 oz/hr.
Running slightly richer...about 22 oz/hr .....but your heater should NOT run non-stop.
Also....understand this.....if you are getting terrible gas milage....snd having to run high heater settings. ....its because your metering pump is putting out too much fuel. Just like in an engine...running that rich puts most of the fuel out the exhaust....runs a cooler flame....and transfers less heat.
In the city driving where the engine fans and heater boxes do less for your heat and you need higher heater settings ....and in good tune you should be averaging 22-23 mpg.....at full heater settings on a well tuned heater system....you will burn 1/8th of a gallon of fuel per hour in coldest weather keeping warm in the city.
So....you should be losing 3-4mpg in the city with the heater on full blast.
With highway driving where you have heat blasting through the heater boxes from your 3400 rpm engine fan.....heater settings in the same weather tend to be about 1/3 lower. I only see mpg loss typically at 2mpg on the highway.
Yes....you need to check and calibrate your metering pump. Also when you do this the engine and the heater must be warmed ip fully.
If not....and this is where most owners make the mistake and set the pump far roo rich......the heater main blower when cold runs slowly until the grease in the bearings warms up. Since the trigger points in the blower fire the glow plug coil AND trigger the fuel pump......a cold blower with tacky grease....can run as much as 25-30% slower rpm for the first 4-8 minutes during cold weather. This makes the cc output during testing too low....so owners erroneously crank up the pump flow.....and then knce the blower warms up.....now you are getting too much fuel.
Also you need to check the resistance of the two pin thetmostat in the duct.
The very best things you can do for heater efficiecny before adjusting is make sure you no air leaks in the heater ducts and insulated tubes.
Ray |
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