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Aug
Higher octane fuel does not have more energy its just more expensive. All other factors being equal an engine with a higher compression ratio will deliver a higher thermal efficiency.
High compression in a cylinder usually means there is liquid oil andor high carbon deposit in the combustion chamber displacing room for air.
What is considered a high compression engine. What is considered a high compression engine. Compression ratios usually range from 81 to 101. A higher compression ratio say from 121 to 141 means higher combustion efficiency.
Higher compression ratios and combustion efficiency mean more power with less fuel and fewer exhaust gases. Does high compression make more power. What is considered high compression in an engine.
Anything over 101 is a high compression ratio. Anything over 121 is highly compressed. 87 Octane is both a high and low compression fuel.
What does low engine compression in one cylinder mean. Low engine compression in one cylinder will cause different symptoms from when low compression is in. What is a high compression engine.
If an engine has a high compression ratio it means that a given volume of air and fuel in the cylinder is being squeezed into a much smaller space than an engine with a lower compression ratio. Pretend you have an engine whose cylinder and combustion chamber volume is 10 cc when the piston is at bottom dead. In my mind a high compression engine is a compression higher than pump gas can be safely run example 105-1 93 octane limit most engines so i guess over 105-1 is considered high compression also as octane goes up rate of burn slows so dont put race fuel in a low compression engine its doing no good.
1 With high compression ratio they operate at higher pressures and offer a cleaner and complete burn of fuel leading to better mileages too. A higher compression ratio– say from 121 to 141 – means higher combustion efficiency. Higher compression ratios and combustion efficiency mean more power with less fuel and fewer exhaust gases.
All other factors being equal an engine with a higher compression ratio will deliver a higher thermal efficiency. This means that the engine is able is turn more of the heat generated from the combustion process into horsepower instead of wasted heat. As a result the compression required in a diesel engine is very high usually about 350 PSI or more.
This makes the diesel engine much heavier and louder compared to the gasoline engines. When Should You Check The Compression In Your Vehicle. High compression in a cylinder usually means there is liquid oil andor high carbon deposit in the combustion chamber displacing room for air.
The air gets more compressed because the combustion chamber is essentially smaller and the pressure reads high. A higher compression motor will make more usable power on a street car. The motor will make power lower in the RPM range and will spool a turbo faster.
Your max boost level will be less on a high comp motor all other things being equal but its power that makes a car fast not psi. As a general rule of thumb compression pressure around 90psi is the minimum required for combustion to occur in a gasoline engine. That is if the compression test reveals less than 90psi that particular cylinder can be declared dead On the other end of the spectrum 200psi is about the most compression pressure you will see in a non-racing.
If an engine has a high compression ratio it means that a given volume of air and fuel in the cylinder is being squeezed into a much smaller space than an engine with a lower compression ratio. Depending upon the condition of the piston rings and valves a healthy engine typically has a cranking compression between 150 and 180 psi. A good performance engine can easily have a cranking compression of more than 200 psi.
Some are a little higher and a. Higher compression ratios can make gasoline petrol engines subject to engine knocking also known as detonation pre-ignition or pinging if lower octane-rated fuel is used. This can reduce efficiency or damage the engine if knock sensors.
Higher compression ratios run hotter and will earlier begin to predetonate which is why high octane fuel is used. It resists more against that. An engine that is designed for high octane fuel should use it other engines not.
Higher octane fuel does not have more energy its just more expensive. Its as simple as that. High compression ratio engines burn both much more cleanly and much more efficiently than lower-compression engines.
For example a diesel engine which burns fuel very differently to a gasolene engine will often give fuel economy 60 greater than its gas equivalent even though diesel only has about 10 more energy per gallon. As a result poor rings usually cause this condition. Be aware that a cylinder suffering from excessive oiling even from bad rings.
Can yield high compression test results. Other symptoms may give you a clue to the problem a smoking engine. There are some variables that affect the readings obtained from compression testing.
October 2007 by Pacific Continental Engines NEW Cylinders at overhaul Compressions at last annual. 176 278 377 477 578 677 Engine Notes. Very smooth running especially at idle.
Are these good compression numbers. Whats considered good borderline and its time for some serious maintenance. Continuing with our 350 engine example with a 4-inch bore and the piston top inch down the bore a perfect cylinder would measure 07854 x 4 x 4 x 050 628 ci x 1639 conversion 103 cc.
High cylinder pressure which is caused partly by a high compression ratio is what makes an engine detonate on pump gas. Decreasing the cylinder pressure by adding duration is just like taking compression out of the engine but mostly only at low RPM. Duration has a marked affect on a cams power band and drive-ability.
Which octane level is required for a particular engine is determined by its compression ratio. Higher-compression engines require higher-octane fuel. For example the engine in a basic sedan generally requires the standard octane fuel offered at gas stations but a high-performance sports car or race car might require a high octane fuel.
High compression ratios in gas engines often cause a problem known as engine knocking. Diesel engines on the other hand are designed for high compression in order to function. A ratio of 131 is considered high in a gas engine while a diesel engine can range from 141 up to 231 depending on the type.
Sometimes having compression as low as 80 and 90 the engine will still run great. Well talk about low results in a minute. Now the Four-Strokes have more moving parts.
They dont have ports like on the Two-Strokes. Instead they have intake and exhaust valves that also need to close and they have a much higher compression reading. As long as the engine can tolerate higher compression without detonation the higher the better within reason.
190 is about the limit for todays engines running the fuels of today. Back in 90s the fuel would tolerate more spark advance more compression and higher cylinder temps before problems would appear.