Volvo Kad 43 Fuel consuption

[zingaro]

Does anyone no the difference in fuel consuption between a Kad 43, 230hp and a kad 41, 200hp as when i look at the boat test figures produced in a report on my boat by MBM it listed the fuel consuption at 2 MPG at 3000 rpm with a speed of 18.8 knots. I have the identicle boat used in the test except mine is fitted with kad 43s and achieved 22.5 knots at 3000 rpm which is the cruising speed that i try and stick too conditions permitting.Are the kads 43s thirstier than the kad 41s what is the difference between them for one to achieve more horsepower.

 

[[2068]]

I would have thought that with those two engines, the amount of fuel to get from A to B will be about the same, except that with the more powerful KAD43's you're getting there a bit faster, burning more fuel per hour, but total fuel burnt for the journey being equal, which is what counts.

dv.

 

[Wiggo]

The KAD42/43 differs from the AD41 in that they are supercharged as well as turbocharged (hence the 'K' bit). This gives them better acceleration, as the blowers give boost while the turbos are still spinning up. There were other differences between the 41s and 42/43's as well that account for the different horsepower ratings.

As the 42/43 chucks out more power, it runs with coarser props than the 41 would, meaning that for a given engine revs they will be quicker (as you've spotted).

Fuel consumption is related to output power, and power to engine revs. If you went at 18.8 knots, you'd be pushing the same amount of water per second out of the way as the test boat, needing the same energy and burning about the same amount of fuel.

As DV says, at the same 3000 rpm, you burn a bit more fuel but get there quicker, so you burn it for less time. Overall, you should probably see similar mpg up to a point (the fuel consumption rises very sharply in the last 15% or so of the rev range).

 

[zingaro]

Thanks for the information

 

[DavidJ]

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The KAD42/43 differs from the AD41 in that they are supercharged as well as turbocharged (hence the 'K' bit).

[/ QUOTE ]
K for Kompressor, of course!, I didn't realise that. All I can add is that 2mpg is what I get overall from my KAD43's fitted to a Sealine S37