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post #10 of Old 05-02-2012
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Re: Turbo charged diesel

Originally Posted by shogan50 View Post
If your sailboat smokes at 80% throttle, something is amiss, likely the prop pitch. The smoke only happens on a properly setup diesel when it can't reach governed RPM.
You mean 80% speed on the governor which is the "throttle" on the boat. It might govern to something like 50 or 60% of actual engine throttle or 90% if your boat is tied up and can't move.

I meant over 80% throttle, or about when it starts putting out black smoke. Diesels are not intended to be used continuously like this.

Good luck making hull speed with a Harley at 1200 RPM.
If you get an engine that is twice as big, you can run it at half the RPMs and it will last MORE than twice as many hours. That's why only cheap generators for temporary emergency use run at 3600 RPM. They are shot after 1500 - 3000 hours. An 1800 RPM one might do 6000 to 10,000 hours.

Why do you think that nearly all over the road trucks in the world use turbo diesels. - because they hate efficiency? Turbos increase effective compression ratio. They generally demonstrate better efficiency than NA engines, not worse(but probably not at 8-1200 RPM).
American engine makers don't care about efficiency (it's a political economic thing.) That's why you can do a software mod on some GM diesels to boost the MPG by like 6 (it probably has to do with injecting the fuel at the proper time when the piston is as close to T.D.Center as possible.) Trucks want to have a lot of power in a small package and having a turbo is great for this.

Compression ratio is compression ratio. The only way to change it is to change the pistons or head. Effective compression ratio is well "effective" which I assume is referring to how much power the engine puts out and has nothing to do with efficiency.

Increasing the intake pressure increases the amount of air in the cylinder ("effective compression ratio"), and the amount of fuel can be increased by the same amount, which will result in the cylinder pressure at combustion and power output being increased by that amount. Increasing the actual compression ratio means that the same amount of air is going in the cylinder, the same amount of fuel is going in the cylinder, but the cylinder pressure at combustion is increased and power output is increased with the same fuel use!

Are you sure you can boost the efficiency on the SAME MODEL of engine by putting a turbo charger on it?
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