i know how to do a compression test on a piston engine, you take out the spark plug out and crank the engine over until it says at a certain psi. but with a rotary engine you have 3 combustion chamber per spark plug hole (except for the trailing plug) so how would you do that?

thanx

 

measure it three times should atleast be 90 psi per rotor and the 120-100 is a great-normal number range anything under 90 means your engine is going to the rotary gods soon....

 

well i understand that you have to put the guage in the spark plug hole but how do i know which side i am testing and how would i know i am doing the same side 3 times. i know i could put it in and if i cranked the engine a few times i would get a reading from the highest psi rotor side, what my question is how do i test each side individually?

 

you do a bump test and an overall compression test the bump test is simply you bumping the starter and checking each side of the rotor...you have to reset the gauge each time....then for the overall you just keep the starter going and watch for the highest psi rating....

 

There are two things you can do. That little valve that keeps the pressure in the gauge, cut it off. Depending on the type of compression tester you bought. Some are right on the rubber line. On mine I just took a new air coupling from my work and screwed that on. Works fine and it shows each pulse of the rotor.

The second, go to mazda.

 

Or you get one of these (or something similar)
http://cgi.ebay.com/ebaymotors/ws/eB...tem=1873520808

 

I have a question so each individual spark plug hole checks a different rotor or whatever?

 

use a piston compression checker, take out check VALVE, attach the compression thingy to the LEADING spark plug, have a buddy floor the gas and crank it BUT ONLY AFTER u take out two EGI MAIN FUSES, i don't think u have to worry too much about the CAS wire, then crank for 10-15 secs and watch the PSI thingy go up n down three times.

make sure u gots a good battery also, weak battery gave me 30-30-30 then 60-60-60 then i got a good battery i got 110-110-110 then 115-115-115..

-mike

 

Check out this post. I listed a step-by-step guide straight from the Haynes second gen. manual on how to do a compression test on a rotary. Also has the figures for what the compression numbers should read.

Hope it helps

https://www.rx7club.com/forum/showth...hreadid=135800

 

buy a compression tester, pull the 2 fuses with the tester in leading plug hole hold the pedal to the floor and crank for 30 seconds take the readings the minimum is 85psi and the variation cannot be more then 21psi...

 

This is straight from the service manual.

Compression

Note
The compression tester for conventional piston engines reads only the highest pressure of the three combustion chambers in the rotor housing. Use compression tester (49F0189A0) to measure the compression of the three combustion chambers.

Warren’s Note: not everybody has a tester like they stated. You can use a conventional tester and remove the valve stem from it. That way you will see the gauge move up and down and not hold the pressure from the first hit.

1. Check that the battery is fully charged.
2. Warm up the engine to operating temperature.
3. Turn it off for about 10 minutes to reduce the exhaust pipe temperature.
4. Remove the front and rear trailing-side spark plugs.
5. Disconnect the crank angle sensor connector.
6. Connect the compression tester (49F0189A0) with adaptor to the front housing and the battery.
7. Fully depress the accelerator pedal and crank the engine for 5-10 seconds.
8. Make a note of the compression of the three combustion chambers and cranking speed.

Compression:
588 kPa (6.0 kg/cm2 , 85 psi) – 250 rpm
Differential limit of chambers:
147 kPa (1.5 kg/cm2 , 21psi) – 250 rpm

9. Check the rear chambers with the same procedure.