what is a good COMPRESSION??
11-05-06, 12:14 AM
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what is a good COMPRESSION??
ok so i'm going to get my rx-7 to a compression test. what is the range in numbers of my compression? whats good, ok, bad, very bad?
11-05-06, 12:54 AM
#2
Are you doing it with a piston tester, or getting it done by mazda with the rotary tester? With the piston tester, 110+ is excellent, 95-110 is good, 85-95 is decent, and below 85 is getting ready need a rebuild. Keep in mind those are general numbers, just a general guide. There are also several variables in checking with the piston tester, such as battery charge, or if its been sitting a while.
As for the rotary tester, I'm not sure off the top of my head.
As for the rotary tester, I'm not sure off the top of my head.
11-05-06, 02:09 AM
#3
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Won't it also be dependant on the compression ratio of the rotors? An S5 NA should get higher compression numbers than an equal condition S4 TII due to the compression differences of the 9.7:1, vs the 8.5:1.
11-05-06, 08:54 AM
#6
Originally Posted by Black91n/a
Won't it also be dependant on the compression ratio of the rotors? An S5 NA should get higher compression numbers than an equal condition S4 TII due to the compression differences of the 9.7:1, vs the 8.5:1.
11-05-06, 09:09 AM
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Originally Posted by hondahater
compression ratio of the rotors has nothing to do with the cars actuall comression numbers.
Really. Could'a fooled me when I put 10:1 pistons in a stock 9:1 engine the compression pressure shot up QUITE a bit.
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11-05-06, 11:27 AM
#11
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Originally Posted by hondahater
compression ratio of the rotors has nothing to do with the cars actuall comression numbers.
11-06-06, 08:00 AM
#12
Originally Posted by mikaz
don't listen to this guy.....
compression is going to be the same no matter what rotors. If they where going to be differant the fsm would specify differant compression numbers for the differant rotors but it does not. I've taken compression readings from s4 to s5's, high and low compression rotors and they are all the same unless they where blown or something. you can also do searches and it's been said time and time again. You sir are the one not to be listened to.
edit: if high and low compression rotors really did make a differance, perfect compression wouldn't be 120 for all rotary enginges it would be more like 120 for low compression rotors and 130 or something for high but as we all know that is simply not true.
Last edited by hondahater; 11-06-06 at 08:13 AM.
11-06-06, 08:45 AM
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No. Higher compression equals a higher figure.
Attached at the end of this post is a thread from a fellow who was trying to make a digital compression tester. He dealt with both series four and series five motors/rotors. The figures speak for themselves.
There's no way a stock series four turbo motor with low compression rotors are going to read the same as a series five n/a with higher compression. It falls under common sense imho.
The site: http://www.marx7.org/~dsmith/comp.htm
It takes a bit of time to download because of the graphs, if using dial up.
Attached at the end of this post is a thread from a fellow who was trying to make a digital compression tester. He dealt with both series four and series five motors/rotors. The figures speak for themselves.
There's no way a stock series four turbo motor with low compression rotors are going to read the same as a series five n/a with higher compression. It falls under common sense imho.
The site: http://www.marx7.org/~dsmith/comp.htm
It takes a bit of time to download because of the graphs, if using dial up.
11-06-06, 09:38 AM
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with the rotary compression tester 800+ is damn near brand new
anything under 500 and you're having some problems
i just had mine done cause i'm having some issues and i ran higest was 834 on #1 rotor and 797 on #2
my old engine had around 480 on each rotor and it didn't run
anything under 500 and you're having some problems
i just had mine done cause i'm having some issues and i ran higest was 834 on #1 rotor and 797 on #2
my old engine had around 480 on each rotor and it didn't run
11-06-06, 10:03 AM
#17
Originally Posted by HAILERS
No. Higher compression equals a higher figure.
Attached at the end of this post is a thread from a fellow who was trying to make a digital compression tester. He dealt with both series four and series five motors/rotors. The figures speak for themselves.
There's no way a stock series four turbo motor with low compression rotors are going to read the same as a series five n/a with higher compression. It falls under common sense imho.
The site: http://www.marx7.org/~dsmith/comp.htm
It takes a bit of time to download because of the graphs, if using dial up.
Attached at the end of this post is a thread from a fellow who was trying to make a digital compression tester. He dealt with both series four and series five motors/rotors. The figures speak for themselves.
There's no way a stock series four turbo motor with low compression rotors are going to read the same as a series five n/a with higher compression. It falls under common sense imho.
The site: http://www.marx7.org/~dsmith/comp.htm
It takes a bit of time to download because of the graphs, if using dial up.
11-06-06, 10:09 AM
#18
Haven't we ALL heard this
Well, then ... it does make sense that compression ratio will have an effect on your readings.
Because I was getting rather depressed. I rebuilt my first engine and used brand new housings , RA seals, OEM springs, and S4 turbo rotors. My compression check came out at 90psi. I guess that isn't so sucky.
James
Because I was getting rather depressed. I rebuilt my first engine and used brand new housings , RA seals, OEM springs, and S4 turbo rotors. My compression check came out at 90psi. I guess that isn't so sucky.
James
11-06-06, 10:09 AM
#19
I guess for aguments sake I'd like to see kevin landers in here just because he rebuilds a dumb amount of these engines and can tell us real quickly what he sees when doing compression tests. I don't mind saying it when I'm wrong but I had to do lots of research on this because I had the same question and from what I found it doesn't make a differance.
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