How to do a compression test.
08-06-2010, 04:34 PM
#1
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How to do a compression test.
Wanted to see if i could get some instructions on how to do a compression test. My friend is supplying the compression tester that he uses on rx7s. So he is not sure the steps on how to do it for the rx8. Any help would be great.
08-06-2010, 04:40 PM
#2
Steps are pretty much the same.
On most modern fuel-injected rotary engines you remove the EGI fuse(s) to disable the ignition.
On the RX8, you disconnect the eshaft sensor.
Other than that... steps should be the same.
Compression numbers for the RX8 @ 250rpm:
Standard = 120psi
Minimum = 98.6psi
On most modern fuel-injected rotary engines you remove the EGI fuse(s) to disable the ignition.
On the RX8, you disconnect the eshaft sensor.
Other than that... steps should be the same.
Compression numbers for the RX8 @ 250rpm:
Standard = 120psi
Minimum = 98.6psi
Last edited by Jon316G; 08-06-2010 at 04:43 PM.
08-06-2010, 06:08 PM
#6
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They use this. http://www.twistedrotors.com/index.html
There is an instructions manual. So for the rx8 all i have to do is disconnect the eshaft sensor then do the test?
There is an instructions manual. So for the rx8 all i have to do is disconnect the eshaft sensor then do the test?
08-06-2010, 08:20 PM
#7
Disconnecting the eshaft sensor disables the ignition, but you still need to disable the fuel pump.
There is a 20A FUEL PUMP fuse that needs to be removed.
My tester is different, but the idea is pretty much the same.
After the fuse is removed and the EPS disconnected, remove the leading spark plug and insert the transducer.
Crank the engine for 5sec (no more than 10) and observe the readout.
Now you need to "normalize" the results for 250rpm so you can compare it to Mazda's specs.
I use this Rotary Compression Calculator:
http://foxed.ca/foxed/index.php?page=rotarycalc
AND REMEMBER TO ALSO DOWNLOAD "NI LabVIEW 2009 Run-time Engine Minimal Redistributable" ALSO.
Make sure you choose the Renesis under the 'Engine' drop-down.
Mazda's Specs:
Standard = 120psi @ 250rpm
Minimum = 98.6psi @ 250rpm
There is a 20A FUEL PUMP fuse that needs to be removed.
My tester is different, but the idea is pretty much the same.
After the fuse is removed and the EPS disconnected, remove the leading spark plug and insert the transducer.
Crank the engine for 5sec (no more than 10) and observe the readout.
Now you need to "normalize" the results for 250rpm so you can compare it to Mazda's specs.
I use this Rotary Compression Calculator:
http://foxed.ca/foxed/index.php?page=rotarycalc
AND REMEMBER TO ALSO DOWNLOAD "NI LabVIEW 2009 Run-time Engine Minimal Redistributable" ALSO.
Make sure you choose the Renesis under the 'Engine' drop-down.
Mazda's Specs:
Standard = 120psi @ 250rpm
Minimum = 98.6psi @ 250rpm
08-11-2010, 12:05 AM
#17
Do you have trouble starting?
Do you notice it takes several cranks to get it going?
The upgraded starters have a bigger motor (or more coil windings) so it produces more torque.
On my original starter doing a compression test, my best RPM was 177.
On my upgraded starter, the best RPM was 248 (going off of memory).
Watch the following and see if your car sounds like this:
http://www.vimeo.com/3653485
Do you notice it takes several cranks to get it going?
The upgraded starters have a bigger motor (or more coil windings) so it produces more torque.
On my original starter doing a compression test, my best RPM was 177.
On my upgraded starter, the best RPM was 248 (going off of memory).
Watch the following and see if your car sounds like this:
http://www.vimeo.com/3653485
08-19-2010, 01:49 PM
#19
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I have trouble starting my car. Always starts, but takes several cranks. Where can I get an upgraded starter and how much are they? Is it easy to install? I just installed a starter on my friend's Camry and wasn't bad.
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