can someone plse explain compression ratios for me.
ok. does higher compression mean more torque or hp.
thanks for the help.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by valiente540 &raquo;</TD></TR><TR><TD CLASS="quote">can someone plse explain compression ratios for me.
ok. does higher compression mean more torque or hp.
thanks for the help. </TD></TR></TABLE>

http://en.wikipedia.org/wiki/Compression_ratio
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wikipedia &raquo;</TD></TR><TR><TD CLASS="quote">
It is the ratio between the volume of the cylinder, when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke.
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wikipedia &raquo;</TD></TR><TR><TD CLASS="quote">
A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. High ratios place the available oxygen and fuel molecules into a reduced space along with the heat of compression - causing better mixing and evaporation of the fuel droplets. Thus they allow increased power at the moment of ignition and the extraction of more useful work from that power by expanding the hot gas to a greater degree.

Higher compression ratios will however make gasoline engines subject to engine knocking, also known as detonation and this can reduce an engine's efficiency or even physically damage it.
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its basically the number of times the intake air is compressed before its ignited.

IE: 11:1 compression means the intake air is compressed 11 times before it ignites.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">its basically the number of times the intake air is compressed before its ignited.

IE: 11:1 compression means the intake air is compressed 11 times before it ignites.</TD></TR></TABLE>

No.

See post above yours.

Higher compression ratios usually mean more torque but also HP if the engine can keep breathing well at higher RPMs. (always keeping in mind that horsepower is not a force but a mathematical number calculated from torque)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91DA9 &raquo;</TD></TR><TR><TD CLASS="quote">No.

See post above yours.</TD></TR></TABLE>
Eh, he's right, but the wording was ambiguous.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ddd4114 &raquo;</TD></TR><TR><TD CLASS="quote">
Eh, he's right, but the wording was ambiguous.</TD></TR></TABLE>

Yeah after re-reading it a few times, I guess it does make a slight bit of sense. I never cared much for oversimplified explanations of many things. It really is best to think of it from the volume standpoint, because things like volumetric efficiency, displacement, etc., are all based on that.

I think reestablishing what a ratio is, does not lend itself very well as to what is happening to get compression.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91DA9 &raquo;</TD></TR><TR><TD CLASS="quote">

Yeah after re-reading it a few times, I guess it does make a slight bit of sense. I never cared much for oversimplified explanations of many things. </TD></TR></TABLE>

i was aiming to explain it in lamens terms (note the first 2 words "its basically") as the first response was very technical and i know some people have a hard time grasping things when the wording is very technical. i figured if he was asking about CR's he's new to cars and such so he might not be that technical yet

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">

i was aiming to explain it in lamens terms (note the first 2 words "its basically") as the first response was very technical and i know some people have a hard time grasping things when the wording is very technical. i figured if he was asking about CR's he's new to cars and such so he might not be that technical yet </TD></TR></TABLE>

Yeah, sorry bro, wasn't trying to cut you down or anything. When I originally read it, I thought you meant the charge was literally compressed x number of times before being lit, when it is obviously only compressed once. In my opinion, if you are just getting into cars and want to delve right into engine theory you should know the fundamentals of gases and the nature of compression by changing the volume of those gases.

I was always a visual/experimental learner and one way that helped me explain it was with a larger syringe. You could start the plunger at 25cc and then push it down to 5 cc, while holding your finger over the tip (needle removed). That would be feeling the equivalent of a 5:1 compression ratio, because the atmospheric gas has been compressed to 1/5 of it's normal volume. Vacuum works on the same principles and can be felt with this example.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91DA9 &raquo;</TD></TR><TR><TD CLASS="quote">

Yeah, sorry bro, wasn't trying to cut you down or anything. When I originally read it, I thought you meant the charge was literally compressed x number of times before being lit, when it is obviously only compressed once.

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oh, lol, all good i know what you mean, when you put it that way my statement wasent that clear.