I have a Perkins Prima 50 HP diesel engine installed in my boat and I cant seem to find the fuel consumption information Running the engine at 2000 RPM and at 1000 RPM what is the average fuel usage per hour I would expect to see.... Filling the tank and recording the hours usage is difficult as varying speeds are hard to record using this system all assistance is much appreciated Regards Tim
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I have a similiar engine.....
I have the Volvo MD22LB which is a 2.2 liter 50hp that uses the Perkins block. This is installed in a Hunter 40.5. At 2500 rpm, I use about 0.8 gallons or 3 liters per hour. I know this figure because for two years my fuel guage was broken. I used the elasped time meter to calculate consumption at fill-ups.
I have the Volvo MD22LB which is a 2.2 liter 50hp that uses the Perkins block. This is installed in a Hunter 40.5. At 2500 rpm, I use about 0.8 gallons or 3 liters per hour. I know this figure because for two years my fuel guage was broken. I used the elasped time meter to calculate consumption at fill-ups.
Well running diesel engines
consume about .285 liters per hour per horse power. So your fuel comsumption rate will depend on how much horsepower your propeller absorbs and how much of an accessory load you have. Just because the engine is rated at 50 hp dose not mean that it is generating that much. You can run wide open throttle with no load and the governor will limit the fuel consumption to the need to maintain that speed at that load. When you put the transmission in gear and go to WOT the governor will supply fuel suffient to bring the engine to full rpm and for a short time you will be making black smoke.
consume about .285 liters per hour per horse power. So your fuel comsumption rate will depend on how much horsepower your propeller absorbs and how much of an accessory load you have. Just because the engine is rated at 50 hp dose not mean that it is generating that much. You can run wide open throttle with no load and the governor will limit the fuel consumption to the need to maintain that speed at that load. When you put the transmission in gear and go to WOT the governor will supply fuel suffient to bring the engine to full rpm and for a short time you will be making black smoke.
Don't be concerned with "varying speeds"
The measured fuel consumption in liters/hour will yield not an exact figure but an average number which will be useful for you to calculate minimum fuel requirements for a trip or leg of a trip, help approximate time to refuel, help monitor engine efficiency, calulate fuel costs for a season or trip, etc. The burn rate should be calculated at normal usage which includes the varying RPM ranges normally utilized. Fill up the tank, keep a record of the time the engine is run untile you reach ten hours, refill again and divide the number of liters taken by the 10 hours and that will yield a good approximate figure of your burn rate. To try to get burn rate for 1000 rpm or for 2000 rpm is irrelevant as those figures will be hardly useful. The burn rate of 3 liters per hour sounds reasonable for your engine and you can use that until you calculate your own. Engine size and condition are the main factors in timed fuel consumption.
The measured fuel consumption in liters/hour will yield not an exact figure but an average number which will be useful for you to calculate minimum fuel requirements for a trip or leg of a trip, help approximate time to refuel, help monitor engine efficiency, calulate fuel costs for a season or trip, etc. The burn rate should be calculated at normal usage which includes the varying RPM ranges normally utilized. Fill up the tank, keep a record of the time the engine is run untile you reach ten hours, refill again and divide the number of liters taken by the 10 hours and that will yield a good approximate figure of your burn rate. To try to get burn rate for 1000 rpm or for 2000 rpm is irrelevant as those figures will be hardly useful. The burn rate of 3 liters per hour sounds reasonable for your engine and you can use that until you calculate your own. Engine size and condition are the main factors in timed fuel consumption.
Fuel Consumption Rate
Tim, Was going to ask why you needed the rate in liters, then saw you're in MelVVorne; caught the ferry from there to Tassie when heading to Strahn to work on an Abalone boat. 1) Very difficult to ascertain exact consumtion rate, carry extra fuel, and never get below 1/3 tank in a diesl as you hit a wave, fuel gets airborne, and you suck air! 2) John Vigors book, lotta skippers use, has one gallon per hr for each 18 H.P. for diesel, one gal per hr for each 10 H.P. for petrol. Assume an engine at cruising speed uses 2/3 of the available H.P. to complicate it more, most diesels have two rated H.P. outputs, a higher one at max RPM for one hr. These are GENERAL guidelines, all engines, trans, hulls, props and conditions will play havoc with calculations. Fill all the way up the neck without air pocket, log EVERYTING then refill exactly the same, log EVERYTHING each trip; then do the division, and above all carry more fuel than you 'think' you'll need.
Tim, Was going to ask why you needed the rate in liters, then saw you're in MelVVorne; caught the ferry from there to Tassie when heading to Strahn to work on an Abalone boat. 1) Very difficult to ascertain exact consumtion rate, carry extra fuel, and never get below 1/3 tank in a diesl as you hit a wave, fuel gets airborne, and you suck air! 2) John Vigors book, lotta skippers use, has one gallon per hr for each 18 H.P. for diesel, one gal per hr for each 10 H.P. for petrol. Assume an engine at cruising speed uses 2/3 of the available H.P. to complicate it more, most diesels have two rated H.P. outputs, a higher one at max RPM for one hr. These are GENERAL guidelines, all engines, trans, hulls, props and conditions will play havoc with calculations. Fill all the way up the neck without air pocket, log EVERYTING then refill exactly the same, log EVERYTHING each trip; then do the division, and above all carry more fuel than you 'think' you'll need.
Fuel consumption
Many thanks for everyones assistance with my question on this great site Best regards Tim Foster
Many thanks for everyones assistance with my question on this great site Best regards Tim Foster
calculating burn rate is actually very simple;
The formula is fuel used over time spent. There is a misconception that hull condition, prop, wind and currents influence the burn rate but these items as you can see do not enter into the formula. These factors do influence disatance travelled and speed, but not burn rate. The burn rate of your engine is only influenced by its size and condition. Do calculate 20% of the maximum hours the engine will run on a tank of fuel and keep it as an emergency reserve. Just measure the fuel used and divide by the number fo hours; it is simple and it will give you an useful figure. The distance to be travelled is to be calculated according to the conditions at the time you are navigating; you just know how many hours the engine will run.(Do not count the reserve time)
The formula is fuel used over time spent. There is a misconception that hull condition, prop, wind and currents influence the burn rate but these items as you can see do not enter into the formula. These factors do influence disatance travelled and speed, but not burn rate. The burn rate of your engine is only influenced by its size and condition. Do calculate 20% of the maximum hours the engine will run on a tank of fuel and keep it as an emergency reserve. Just measure the fuel used and divide by the number fo hours; it is simple and it will give you an useful figure. The distance to be travelled is to be calculated according to the conditions at the time you are navigating; you just know how many hours the engine will run.(Do not count the reserve time)
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