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Discussion Starter · #1 ·
hey guys got my car back today and they said it did not run like a car that's supposed to have a 12:1 compression. So is there any easier way then dropping the pan and looking to see if my pistons say SRP on the bottom to tell? I once read you can figure out your CR by using some formula on the compression test numbers.
 

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Well compression testers are usually not that accurate...thats why you only pay attention to the number difference from cylinder to cylinder to see if the engine is good.

However...I suppose if you gave a stock engine a compression test...something that you KNEW the compression of...like a d16z6 (9.2:1), then you could compare those results to the results of your engine and figure out the C/R with a ratio.

Ex:

if a d16z6 gave 180psi (average of 4 cylinders)...and your engine gave an average of 240psi...then you could just do:

180:::::240
---- = ----
9.2:::::: X

Where X is YOUR engines C/R.....and using your basic math skills: (240*9.2)/180 = 12.26667

So your engine would have a C/R of about 12.3:1

This would of course be an approximate answer because the final answer depends on the condition of the d16z6..I would say 12.3:1 give or take .5 points

werd?
 

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gurusan said:
Well compression testers are usually not that accurate...thats why you only pay attention to the number difference from cylinder to cylinder to see if the engine is good.

However...I suppose if you gave a stock engine a compression test...something that you KNEW the compression of...like a d16z6 (9.2:1), then you could compare those results to the results of your engine and figure out the C/R with a ratio.

Ex:

if a d16z6 gave 180psi (average of 4 cylinders)...and your engine gave an average of 240psi...then you could just do:

180:::::240
---- = ----
9.2:::::: X

Where X is YOUR engines C/R.....and using your basic math skills: (240*9.2)/180 = 12.26667

So your engine would have a C/R of about 12.3:1

This would of course be an approximate answer because the final answer depends on the condition of the d16z6..I would say 12.3:1 give or take .5 points

werd?

Damn you know your stuff. BTW nice Sol man...that thing is CLEAN. :number1
 

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gurusan said:
Well compression testers are usually not that accurate...thats why you only pay attention to the number difference from cylinder to cylinder to see if the engine is good.

However...I suppose if you gave a stock engine a compression test...something that you KNEW the compression of...like a d16z6 (9.2:1), then you could compare those results to the results of your engine and figure out the C/R with a ratio.

Ex:

if a d16z6 gave 180psi (average of 4 cylinders)...and your engine gave an average of 240psi...then you could just do:

180:::::240
---- = ----
9.2:::::: X

Where X is YOUR engines C/R.....and using your basic math skills: (240*9.2)/180 = 12.26667

So your engine would have a C/R of about 12.3:1

This would of course be an approximate answer because the final answer depends on the condition of the d16z6..I would say 12.3:1 give or take .5 points

werd?

dude.. its official.. you know to much
 

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dude....did you read my post?

What I said was that you can't tell the compression ratio of a motor by just giving it a compression test because the gauges are different and not that accurate.

That's why you need to compare it to something you already know.
 

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Discussion Starter · #11 ·
Um yeah so I need to know what stock compression test numbers are and then my compression test numbers. Then put 10.4 under stock number and X under what my actual compression numbers are.
 

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Yeah and to know the stock compression test numbers you need to do a compression test!! And then using the SAME gauge you do a compression test on your car...then do the math thingy
 

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Argh. You aren't understanding me.

I know your motor isn't stock...that's the entire point!

Let me break it down for you:

Step 1: Aquire a compression tester gauge

Step 2: Do a compression test on your friend's car or something...something that's stock

Step 3: Do a compression test on YOUR engine using the SAME gauge.

Step 4: Compare your results to his and do the proportion thing to find out your C/R.
 
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