(Gerry this is gold ..gold ,Gerry) lol Thank Daniel My installation plans to turbo charge a 350 chev engine c/w positive displacement pump for the gasifier Henri
Sent from my iPhone On Feb 25, 2011, at 4:01 PM, Daniel Chisholm <[email protected]> wrote: > On Fri, Feb 25, 2011 at 20:45, Toby Seiler <[email protected]> wrote: > I'm under the impression that a small amount of positive pressure on the > intake has a large effect in the engine power, in comparison to a vacuum > intake. How do you think a gas and air pressure of 2-5 pounds or so, would > affect the compression ratio / efficiency if one is using low pressure in > producer gas making? > > Perhaps someone has density information/chart and the way to relates to > compression ratios. > > Toby perhaps the easiest way to keep things straight is to think in terms of > absolute pressure. > > A normally aspirated engine running at wide open throttle has a manifold > pressure of about 15 psi absolute (or if you want to quibble for more > accuracy you could use 14.5 psia: atmospheric pressure is 14.7 psia, and > there's a small amount of vacuum due to the flow restriction of the wide open > carburetor) > > If you supply 1.5psi of boost (so you manifold pressure is now +1.5psi higher > than atmospheric), you have raised your absolute pressure by 10% - from > 15.0psia to 16.5psia. To a pretty good first approximation, this 10% > increase in absolute pressure will give you a 10% increase in horsepower. > > Similarly a 3.0psi boost will give you about a 20% increase in horsepower, > and a 4.5psi boost will give you about a 30% increase in horsepower. > > Compression ratios are multiplicative. So if you are providing 20% boost > (3.0psi) to an engine with an 11:1 compression ratio, the overall effective > compression ratio is 1.20 times 11, for 13.2 to 1 compression ratio. FWIW > the "1.2" is from the 20% boost, the "11" is the piston's compression) > > Figuring out the engine's efficiency change is not as straightforward. On > the one hand, increasing the compression ratio increases the engine's > thermodynamic efficiency (because the mean pressure and mean temperature to > increase). Working against this though is that the engine's *expansion* > ratio has not been changed (the motion of the piston is what extracts work > from the gas). > > While turbocharging an engine has a great deal of sex appeal, it probably > makes a lot more sense to keep Doug's advice in mind. While it's not > completely true that "there is no substitute for cubic inches", that does > make an awfully good "zeroth law of engine selection". > > Adding 40% more cubic inches is in many cases a *much* more elegant solution > to a problem than adding 20% more intake pressure... > > > -- > - Daniel > Fredericton, NB Canada > _______________________________________________ > Gasification mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org > > for more Gasifiers, News and Information see our web site: > http://gasifiers.bioenergylists.org/
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