- Joined
- Oct 1, 2007
- Messages
- 7,331
- Location
- Texas
- Vessel Name
- Floatsome & Jetsome
- Vessel Make
- Meridian 411
OK, I thought I was with you until the argument came up about a turbocharger not necessarily using more fuel.
So, using a Cat 3208TA 375 hp for example. I was under the impression that the turbocharger "kicks in" at a certain rpm. So, am I wrong thinking that if I am underway at a lower rpm (before the turbocharger "kicks in"), that I would be using the same gph as a 3208na at that same speed. I know I am probably trying to get simple explanations for complex issues, so I will hope you will bear with me.
And your discussion about "hp down the shaft" threw me for another loop. How do you determine how much hp one needs down his shaft. Sounds like I am trying to be funny, but I'm serious.
My experience has been with Cat 3208na They would move my boat at about 9 knots at 2100 rpm and would consume 10 gph. If I needed to get off the water due to weather or other issues, I could punch them up to 2450 rpm and gain about 2 knots, but use about 16 gph. Can anyone hazard a guess how a 3208TA 375 hp Cat would have affected those numbers?
Just realize in theory, turbochargers do not "kick in" at a certain RPM. They kick in at a certain load. It is heat that drives a turbocharger(not exhaust flow)....heat is energy. To give you an idea, an engine at idle will not drive up the boost because it is not loaded. Just to clarify things.
And Ski was just using 300hp arbitrarily. Don't let his "down the shaft" terminology throw you off. He just used 300hp as an example.
Now the main reason why turbocharged aftercooled/intercooled engines are more efficient in his example is because of the charge air volume and temperature. You are actually extracting more energy out of a parcel of fuel than you are in an NA engine. It really is as simple as that. And THAT IS THE REASON why turbodiesels dominate the current modern market. They are more efficient...hence they burn cleaner...hence less pollution.
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