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Manifold Pressure, RPM & Engine Efficiency

  • acuthbert
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acuthbert created the topic: Manifold Pressure, RPM & Engine Efficiency

Page 2.9 in the 5th paragraph states "...the best engine efficiency is achieved when the LOWEST RPM is used with the HIGHEST manifold pressure."

Page 2.11 in 2nd paragraph states"...avoid a combination of HIGH manifold pressure and LOW RPM."

All in relation to a CSU.

Just wondering if i have missed something along the way as this contradicts itself.

Aaron
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bobtait replied the topic: Re: Manifold Pressure, RPM & Engine Efficiency

No it is not a contradiction. The engine manufacturer publishes a list of various manifold pressure and RPM combinations that are recommended as safe to use for a particular engine. The combination with the highest manifold pressure and lowest RPM gives the best engine volumetric efficiency.

However if the manifold pressure is higher and RPM are lower than the recommended figures, engine damage can occur. This is called 'overboosting'. Very high manifold pressure combined with very low RPM [beyond the manufacturer's recommendation] actually make the volumetric efficiency too good and too much gas enters the cylinders causing overheating during the compression stroke and detonation during the power stroke.
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  • acuthbert
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acuthbert replied the topic: Re: Manifold Pressure, RPM & Engine Efficiency

Thanks Bob that clears it up for me.

Cheers

Aaron
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