Any Gearhead's?

[Omatako]

Originally Posted by Gramp34

I guess nobody told Caterpillar (or Cummins or Detroit Diesel) that aftercoolers are quite rare.

And of course, CAT 3406 are commonly found on yachts. Look long enough and you'll always find a spec sheet that will suit your argument.

Originally Posted by Gramp34

No. A turbocharger consists of a turbine and a compressor connected by a shaft. The intake air comes in contact with _only_ the compressor and doesn't get near the turbine. It's the compression of the intake air that causes it to be heated, not any contact with the exhaust. By cooling the heated intake air it becomes more dense, allowing more oxygen to be crammed into the fixed displacement of the cylinder, which allows more fuel to be burned.

Your earlier view said "Turbocharging works off the heat in the exhaust". Clearly you have been doing some more reading and now you're saying pretty much what I did. Well done, you're heading in the right direction.

Originally Posted by Gramp34

That's 0.042 mpg. (About 200 times worse than a Hummer.) You call that efficient?

No, not really. But the engine is probably developing 1400hp from an original design output of 180. And it is running at max power, full throttle for 100% of the time. Nobody worries too much about the power it takes to turn the supercharger. Oh no, sorry, you do.

Originally Posted by Gramp34

You're trolling here, right?

No I'm not trolling, I try to give info in my posts that I know something about and stay away from those posts I know nothing about. You should consider that as an option.

[Omatako]

Originally Posted by US27inKS

Sorry Tim, this quote is way off. It's more like 13 gallons.

There's really not much to argue about here. The OP wants to know about putting a supercharger or turbocharger on his sailboat. I think everyone here can agree that he won't get his money's worth in either fuel efficiency or resale value. I think we can also agree that a turbocharged sailboat will get to hull speed quicker than a non turbocharged boat, due to increased power available.

Yep, I agree on both counts. I was never putting forward a proposal that we should all go out and supercharge our Yanmars.

The truth is that most (non-American , sorry ) motor manufacturers are including in their range, much smaller charge-air engines (both turbo- and supercharged). One thing is for sure, they're not doing this to increase fuel consumption. These engines are super-efficient. We have a VW Golf 1.5 litre turbo diesel in the family. it returns fuel consumption of under 5 litres/100km regular as clockwork. I think that's nearly 63 miles/gallon.

[sailingdog]

Gramp34—

Can you point out a small sailboat that is outfitted with a Caterpillar 3406 diesel with an aftercooler??? I've seen aftercoolers on marine diesels, but these were generally on high end, very high horsepower power boats with electronic fuel injection and such... not your typical small sailboat diesel at all.

[US27inKS]

Originally Posted by Omatako

Yep, I agree on both counts. I was never putting forward a proposal that we should all go out and supercharge our Yanmars.

The truth is that most (non-American , sorry ) motor manufacturers are including in their range, much smaller charge-air engines (both turbo- and supercharged). One thing is for sure, they're not doing this to increase fuel consumption. These engines are super-efficient. We have a VW Golf 1.5 litre turbo diesel in the family. it returns fuel consumption of under 5 litres/100km regular as clockwork. I think that's nearly 63 miles/gallon.

Those diesel VW's are pretty nice. First time I drove one I didn't realize it was a diesel, and I fix cars for a living.

It's true that they are very efficient, and get great mileage. The reason is not that the turbo is making it vastly more efficient. The reason is that it's a very small engine to start with, and has the advantage of electronics to help efficiency. The turbo was added to give it enough power so that someone would actually buy it. A non turbo version of that engine would still be very efficient, but wouldn't get out of it's own way. During a highway cruise the turbo isn't doing much for you, and it gets great mileage. When you mash the gas the turbo comes alive and the mileage goes to hell. Watch your boost gauge, you'll see what I mean.

[Gramp34]

Originally Posted by Omatako

And of course, CAT 3406 are commonly found on yachts. Look long enough and you'll always find a spec sheet that will suit your argument.

Fair enough. One spec sheet isn't enough?

Every single Caterpillar marine engine with charge air cooling is aftercooled.

Every single John Deere marine engine with charge air cooling is aftercooled.

Every single Cummins marine engine with charge air cooling is aftercooled.

Maybe you could let us know how many of their engines are intercooled and don't use that "quite rare" aftercooling?

Your earlier view said "Turbocharging works off the heat in the exhaust". Clearly you have been doing some more reading and now you're saying pretty much what I did. Well done, you're heading in the right direction.

I'm still saying turbocharging works off the heat in the exhaust. The heat is the source of power that drives the compressor. You, on the other hand, said "It has nothing to do with heat." when describing how a turbocharger works. I'm afraid I'm saying nothing like what you did.

No, not really. But the engine is probably developing 1400hp from an original design output of 180. And it is running at max power, full throttle for 100% of the time. Nobody worries too much about the power it takes to turn the supercharger. Oh no, sorry, you do.

Funny, you're no longer insisting a supercharged engine is more efficient.

No I'm not trolling, I try to give info in my posts that I know something about and stay away from those posts I know nothing about. You should consider that as an option.

Uh-huh.

But, back to the original problem.

Capnblu: If you can match up the supercharger to the original application, compare the displacement of your engine to the engine the unit came from, and the pulley drive ratio.

The boost on an automotive gas engine will be fairly mild, and would probably make a good starting point for boost on your Perkins diesel.

If the original engine displacement was more than the Perkins, you'll need to drive the supercharger more slowly, and in proportion to the difference in displacment, and vice-versa.

This is assuming you've got a Roots blower type supercharger (with lobed rotors). Their output will be proportional to speed, so double speed gives double the airflow.

If you've got a centrifugal blower, like the Paxton, its output increases with the square of the speed. Doubling the speed quadruples the airflow. You'd have to run it so it doesn't overboost the engine at high speed, but then it won't provide much boost at low speed. The Merlin engines used in Mustangs and Spitfires in WWII had two speed centrifugal superchargers, but that's probably overkill.

Have fun,

Tim

[Gramp34]

Originally Posted by sailingdog

Gramp34—

Can you point out a small sailboat that is outfitted with a Caterpillar 3406 diesel with an aftercooler??? I've seen aftercoolers on marine diesels, but these were generally on high end, very high horsepower power boats with electronic fuel injection and such... not your typical small sailboat diesel at all.

The statement with the Cat datasheet was in response to:

Originally Posted by Omatako

An intercooler (between the turbo and the inlet manifold) is what you're talking about. Aftercoolers are actually quite rare.

"Aftercoolers are quite rare"; presumably Omatako is suggesting intercoolers are not. I never said aftercoolers are common on small sailboat diesels, just that they aren't "quite rare" on diesel engines.

Tim

PS: Don't tell Omatako that intercoolers and aftercoolers are exactly the same thing. Don't believe me? Ask him to explain the difference.

[Gramp34]

Capnblu: Just had a thought how you can increase your motoring efficiency -- not at the engine, but at the prop.

Bigger diameter propellers are more efficient, but they take more torque to turn and turn more slowly.

If your supercharged engine produces its full power at lower RPM, your prop spins more slowly. To absorb the full horsepower at the lower speed you can either increase the pitch, or increase the diameter.

If you can swap the blades on your Maxprop for larger diameter (as long as it still fits under the boat), the overall efficiency goes up.

Being a feathering prop, larger diameter won't noticeably increase drag when sailing.

Dave Gerr's "Propeller Handbook" has all the calculations you'd ever like to attempt when working things out. One thing to check, though, is that the propeller shaft is large enough diameter for the greater torque.

Good luck,

Tim

[jgeissinger]

Put a propane torch on the casing of a turbocharger, heat it until it glows, and then tell me how fast the vanes are turning. It is airflow that spins the turbo! That airflow does come from heated exhaust gasses, but it is not the temperature that spins the air compressor (which is what a turbo is), and forces more air into the combustion chamber. The concept that wasted heat provides the power, because it comes from the exhaust side of the engine, is a common misconception. It is still wrong.

[sailboy21]

I see a thermodynamics lesson coming up....

http://www.turbomustangs.com/turbotech/main.htm

[jgeissinger]

P.S. Actually, Top Fuelers are putting out more than 7000 hp out of 500 cu. in. If the goal is horsepower, not fuel usage, that's pretty darn efficient.