Dannny

i was told that a conventional compression tester would not work on a rotary engine.

well that was after i had bought the tester and tested the engine. I have 105psi on both rotors, could i use that as any indication of how the engine is, even though its not the right tester, even if its just a "ballpark" indication?

thanks

Rx-7Doctor

iTrader: (13)

An acceptable minimum psi is 75psi. Normal range is 110-150psi hot. How did you do this procedure exactly?

Dannny

took the wires comming from the coils off the distributor and put the tester in all of the spark plug holes

they all read 105. it was one of those 25 dollar testers from discount auto parts it has an air check valve. it builds up pressure with each stroke and stays at 105 when its done

the car was a bit hot, drove it to my workshop in my backyard and let it warm up then turned it off

Rx-7Doctor

iTrader: (13)

Almost correct. You leave the trailing plugs in, remove the leading plugs, disconnect the fuel pump fuse at the fuse box and crank over the engine with the throttle wide open to purge any fuel. Make sure your battery is well charged for
proper spinning of the engine. take a reading at each of the leading plug holes. Sounds like you still have good compression even with doing it wet.

Misthael

Thank you on the info on how to properly test compression. I might do that sometime.

Blake

Well, the "proper" method (short of a real rotary compression checker) is to, first, crank WOT with the schrader valve held open. Observe and note that all the "bounces" of the needle are of similar magnitude and evenly spaced. Then, release the schrader valve and note the high reading. Repeat on the second rotor. Hardly scientific but reasonably informative.

Bob Holton

What is a schrader valve ? and what does wot stand for? Thanks

RotaryRyan

WOT=wide open throttle

tmking66

The schrader valve is the small valve in the end of the tester that allows the tester to hold its reading after you stop cranking. This valve is the reason a traditional test will not give you any useful information about your engine. You could have an engine with two bad apex seals but as long as just one is good the tradtional tester will give you acceptable compression readings. For this type of tester to work, you have to remove the schrader valve (using small needle nose pliers). With the valve removed, install the tester and crank the engine. You must watch the needle of the tester CAREFULLY as it will be bouncing very fast. As long as you are seeing bounces that are consistent then you are ok as long as they are within the acceptable compression. If you are seeing the needle taking a low bounce and the higher you have problems. Using the tester right out of the box does not give you accurate info without removing the schrader valve.