davidwf
Active member
Does anybody have a feel for the hourly fuel consumption I should expect from a Honda 6 driving a Beneteau 21.7 (211).
fuel comsumption Honda 6 ?
- Thread starter davidwf
- Start date
ongolo
New member
Roughly, a petrol engine will use 400g petrol per Hp/hour, so if all is well, that engine can not use more than 2.4 liter petrol per hour, but it could use much less if you take it easy
Ongolo
Ongolo
A
Anonymous
Guest
[ QUOTE ]
Roughly, a petrol engine will use 400g petrol per Hp/hour,
[/ QUOTE ]That's interesting - my Yanmar diesel has a specific fuel consumption of around 170g diesel per hp-hr. Presumably diesel has a much higher calorific value?
Roughly, a petrol engine will use 400g petrol per Hp/hour,
[/ QUOTE ]That's interesting - my Yanmar diesel has a specific fuel consumption of around 170g diesel per hp-hr. Presumably diesel has a much higher calorific value?
ongolo
New member
[ QUOTE ]
[ QUOTE ]
Roughly, a petrol engine will use 400g petrol per Hp/hour,
[/ QUOTE ]That's interesting - my Yanmar diesel has a specific fuel consumption of around 170g diesel per hp-hr. Presumably diesel has a much higher calorific value?
[/ QUOTE ]
My air cooled Deutz is supposed to use 161g/Hp/h, but this is because air cooled Diesel engines run a little hotter than liquid cooled diesels.
However, petrol engines run lower internal temperatures and lower compression ratios.
The real difference is that a petrol engine runs on a vacuum and does not burn all petrol to CO2 but some of it is CO, the evaporating petrol also cools down the engine combustion chamber, the pistons pulling against the vacuum take quite some power. Newer fuel injection car engines are more efficient, but a simple caburettor engine like a honda will use close to 400g fuel per Hp/h.
The caloric value in my outdatedn book is almost identical for petrol 11000 kcal and 10500 kcal diesel, so is the theoretical air consumption of 12.7 cubic meter for one kg of fuel for either, but the real air consuption is about 16 to 22 cubic meter air for either engine.
A diesel (except some 220 Mercedes engines) never operates a vacuum, never produces CO as it runs on a surplus of air, that is why diesels like the toyota landcruiser have a little vacuum pump on the alternator needed to run the brake booster.
Hydrogen has 28570 kcal per kg and being under pressure, needs no fuel injector system, just selenoid injectors to meter the gas, but I would be scared of a hydrogen car. In any case, hydrogen seems to be used in fuel cells and ordinary propane used in gas conversions for motor cars has only about 6750 kcal, that is why propan gas motors are expensive to run.
regards ongolo
[ QUOTE ]
Roughly, a petrol engine will use 400g petrol per Hp/hour,
[/ QUOTE ]That's interesting - my Yanmar diesel has a specific fuel consumption of around 170g diesel per hp-hr. Presumably diesel has a much higher calorific value?
[/ QUOTE ]
My air cooled Deutz is supposed to use 161g/Hp/h, but this is because air cooled Diesel engines run a little hotter than liquid cooled diesels.
However, petrol engines run lower internal temperatures and lower compression ratios.
The real difference is that a petrol engine runs on a vacuum and does not burn all petrol to CO2 but some of it is CO, the evaporating petrol also cools down the engine combustion chamber, the pistons pulling against the vacuum take quite some power. Newer fuel injection car engines are more efficient, but a simple caburettor engine like a honda will use close to 400g fuel per Hp/h.
The caloric value in my outdatedn book is almost identical for petrol 11000 kcal and 10500 kcal diesel, so is the theoretical air consumption of 12.7 cubic meter for one kg of fuel for either, but the real air consuption is about 16 to 22 cubic meter air for either engine.
A diesel (except some 220 Mercedes engines) never operates a vacuum, never produces CO as it runs on a surplus of air, that is why diesels like the toyota landcruiser have a little vacuum pump on the alternator needed to run the brake booster.
Hydrogen has 28570 kcal per kg and being under pressure, needs no fuel injector system, just selenoid injectors to meter the gas, but I would be scared of a hydrogen car. In any case, hydrogen seems to be used in fuel cells and ordinary propane used in gas conversions for motor cars has only about 6750 kcal, that is why propan gas motors are expensive to run.
regards ongolo
A
Anonymous
Guest
[ QUOTE ]
The real difference is that a petrol engine runs on a vacuum and does not burn all petrol to CO2 but some of it is CO, the evaporating petrol also cools down the engine combustion chamber, the pistons pulling against the vacuum take quite some power. Newer fuel injection car engines are more efficient, but a simple caburettor engine like a honda will use close to 400g fuel per Hp/h.
[/ QUOTE ]That is interesting.....I remember learning as an engineering student that the laws of thermodynamics explain why any combustion engine (internal or external, piston or turbine) runs more efficiently with a higher difference of temperatures but I had never heard the explanation about vacuum. Presumably the only reason for a vacuum is to make a carburetter a viable means of fuelling the cylinders? If so, I wonder that they have not be banned, along with two stroke outboards, by recent legislation. Thanks for explaining it.
The real difference is that a petrol engine runs on a vacuum and does not burn all petrol to CO2 but some of it is CO, the evaporating petrol also cools down the engine combustion chamber, the pistons pulling against the vacuum take quite some power. Newer fuel injection car engines are more efficient, but a simple caburettor engine like a honda will use close to 400g fuel per Hp/h.
[/ QUOTE ]That is interesting.....I remember learning as an engineering student that the laws of thermodynamics explain why any combustion engine (internal or external, piston or turbine) runs more efficiently with a higher difference of temperatures but I had never heard the explanation about vacuum. Presumably the only reason for a vacuum is to make a carburetter a viable means of fuelling the cylinders? If so, I wonder that they have not be banned, along with two stroke outboards, by recent legislation. Thanks for explaining it.
reeac
Well-known member
Just to complicate things further, diesel fuel is about 10% denser than petrol so you get more molecules per gallon than you do with petrol. If you look at the emissions of two cars - one diesel and the other petrol - which have identical mpg figures you will see that the diesel one emits more carbon dioxide. Each gallon of fuel contains more carbon.
Regarding the talk of vacuums, the diesel has no butterfly valve to restrict air intake as does the petrol engine, hence cutting so-called "pumping losses" which are quite marked at small throttle openings. That's why diesel cars are especially economical at lower speeds and when idling in city driving.
Regarding fuel consumption of marine engines, the commonest way of stating them is in terms of bhp.hours per gallon - 10-12 for 2-stroke, 15 for petrol and 20 for diesel. After all, we buy the fuel by volume [gallons or liters], not by weight [grammes].
Regarding the talk of vacuums, the diesel has no butterfly valve to restrict air intake as does the petrol engine, hence cutting so-called "pumping losses" which are quite marked at small throttle openings. That's why diesel cars are especially economical at lower speeds and when idling in city driving.
Regarding fuel consumption of marine engines, the commonest way of stating them is in terms of bhp.hours per gallon - 10-12 for 2-stroke, 15 for petrol and 20 for diesel. After all, we buy the fuel by volume [gallons or liters], not by weight [grammes].
A
Anonymous
Guest
[ QUOTE ]
Regarding fuel consumption of marine engines, the commonest way of stating them is in terms of bhp.hours per gallon - 10-12 for 2-stroke, 15 for petrol and 20 for diesel. After all, we buy the fuel by volume [gallons or liters], not by weight [grammes].
[/ QUOTE ]Yanmar quote theirs in g/hp-hr so you need to obtain the specific density at the temperature you are working at to obtain volume/hp-hr. Are the figures you quote for US gallons, or imperial?
Regarding fuel consumption of marine engines, the commonest way of stating them is in terms of bhp.hours per gallon - 10-12 for 2-stroke, 15 for petrol and 20 for diesel. After all, we buy the fuel by volume [gallons or liters], not by weight [grammes].
[/ QUOTE ]Yanmar quote theirs in g/hp-hr so you need to obtain the specific density at the temperature you are working at to obtain volume/hp-hr. Are the figures you quote for US gallons, or imperial?
reeac
Well-known member
They are for Imperial gallons. I accept that thermal expansion will have an effect although it won't be much in the normally cold UK marine environment. The effect shows up when you take fuel from a cold underground fuel tank and put it into a car tank on a warm day.
To further clarify what I said earlier, I've just looked up specific data in a Jan. 2004 car mag. and for example:
Hyundai Getz 1.1 48.7 mpg., 138 gm.CO2/km.
Ford Mondeo estate 2.0 DCi 48.7 mpg., 154 gm.CO2/km.
Same mpg. but different CO2 emissions.
To further clarify what I said earlier, I've just looked up specific data in a Jan. 2004 car mag. and for example:
Hyundai Getz 1.1 48.7 mpg., 138 gm.CO2/km.
Ford Mondeo estate 2.0 DCi 48.7 mpg., 154 gm.CO2/km.
Same mpg. but different CO2 emissions.
A
Anonymous
Guest
[ QUOTE ]
To further clarify what I said earlier, I've just looked up specific data in a Jan. 2004 car mag. and for example:
Hyundai Getz 1.1 48.7 mpg., 138 gm.CO2/km.
Ford Mondeo estate 2.0 DCi 48.7 mpg., 154 gm.CO2/km.
Same mpg. but different CO2 emissions.
[/ QUOTE ]I'm not sure what point you are making, CO2 emissions are a different issue and mgp figures as quoted in car data bear little resemblance to the specific fuel consumption of marine engines. Have I missed something?
To further clarify what I said earlier, I've just looked up specific data in a Jan. 2004 car mag. and for example:
Hyundai Getz 1.1 48.7 mpg., 138 gm.CO2/km.
Ford Mondeo estate 2.0 DCi 48.7 mpg., 154 gm.CO2/km.
Same mpg. but different CO2 emissions.
[/ QUOTE ]I'm not sure what point you are making, CO2 emissions are a different issue and mgp figures as quoted in car data bear little resemblance to the specific fuel consumption of marine engines. Have I missed something?
ongolo
New member
Yes you do buy fuel by the gallon and work it mpg, but the rest of the metric world works in liter consumption/100km, and so does the rest of the world indicate the efficiency of stationary engines in consumption in g /Hp /h.
As a matter of fact, quoting mpg and ft/s in a publication was regarded an offense when South Africa changed to metric.
If the Common wealth would come out of the stone age, life would be easier for you guys.
)
As a matter of fact, quoting mpg and ft/s in a publication was regarded an offense when South Africa changed to metric.
If the Common wealth would come out of the stone age, life would be easier for you guys.
)reeac
Well-known member
People were discussing the sources of the diesel engine's greater fuel economy and I made the little-known point that one reason is that it uses a denser fuel and when consumption is measured in the usual way [by volume] this shows up as a 10% reduction in consumption.