Understanding Compression Ratio's.

KnightWalace · Post by **KnightWalace** » Tue Aug 03, 2004 2:15 am

Ok, I just want a clear cut explanation of the Fabled compression Ratios

Ex. 10.1:1 ....

What does that Mean... My friend and I were Wondering.... I heard the lower the compression ratio the better it is for Turbo/Super Charging... but i don't know why how what... you know

Stefan, Shaun? Wolf... OZ... Any definitions you can pitch my way?

2 liter turbo · Post by **2 liter turbo** » Tue Aug 03, 2004 11:26 am

I'll answer that one for ya.
Compression ratio is a measurement in cubic inches of the cylinder volume above the piston when the piston is at TDC (clearance volume) and of the cylinder volume when the piston is at BDC. Basically you take total volume at BDC and divide it by the clearance volume at TDC. Get it?
For instance, if the clearance volume measured 5 cubic inches and the total volume measured 40 cubic inches then the math would be 40 divided by 5 which equals 8. So the compression ratio would be 8 to 1.
Honestly, that's a pretty simplified version. In reality you're measuring the cylinder volumes in CC's and doing some math but that's the basic gist of it.

Tony

KnightWalace · Post by **KnightWalace** » Tue Aug 03, 2004 12:03 pm

Thats Awesome ... thanks... but... why is that better for turbo's?

GsiTurbo · Post by **GsiTurbo** » Tue Aug 03, 2004 1:29 pm

KnightWalace wrote:Thats Awesome ... thanks... but... why is that better for turbo's?

The turbocharger forces compressed air into the combustion chambers, thus increasing the actual compression ratio (air is already compressed by the turbo, then compressed again during the compression stroke cycle of the engine. Air that is too compressed becomes very hot, and may self-ignite (known as pinging or knocking) destroying the engine.

This is a very simplified explanation, but I hope this is sufficient.

KnightWalace · Post by **KnightWalace** » Tue Aug 03, 2004 1:47 pm

THanks GSI i got it now!

Post by **Efratech** » Tue Aug 03, 2004 3:21 pm

You're really on to this, Knight?

I think i will have the highest compresion of the forum! 10:5.1

KnightWalace · Post by **KnightWalace** » Wed Aug 04, 2004 3:11 am

My opinion is... if you love something (aka me and cars) ... then you'll want to know everything about it. So compression is a start... i still don't know much about cars... i know what stuff does... i can't do it by hand... but atleast i can learn by reading this site.

Tim04 · Post by **Tim04** » Wed Aug 04, 2004 6:10 am

That's an admirable attitude to have. I like your style Knight!
You will never know if you don't ask right?

KnightWalace · Post by **KnightWalace** » Thu Aug 05, 2004 2:22 am

Nor will you learn by sitting and watching the ones that do want to learn pass you by.

SinDromX · Post by **SinDromX** » Fri Aug 13, 2004 7:27 am

Efrain A. wrote:You're really on to this, Knight?

I think i will have the highest compresion of the forum! 10:5.1

It's a little pretentious to say that, coz you don't know mine yet.

I have the same compression ratio. lol

So we are both pretentious...