I ran a compression test on my 12A today and i was wondering if these numbers are good, average, Extremely good etc.

Compression on:

1st housing : 120
2nd Housing: 120

Good? Bad?

What's the normal compression on a 12A?

 

I think 120 on both are really good last time I checked... i think... heh

 

Excellent

 

What were the numbers on each face?

 

I'm going to be doing this tonight. How to you get the ones on each face... I have the type that you hold up to a plug hole. So nothing computer driven.

 

On the side by the gauge, there is a pressure release valve, hold that open and watch closely for 3 bounces.

 

You have to use a special compression tester that measures the compression of each face, the normal type u use on piston engines will just give you the compression of the highest compression face, and each face can be different.

 

If you try the hold open the release valve test you will get lower number compression readings, 20% below or something like that i believe, but its a good way to check for consistent compression on each face/ rotor

 

Alright thanks guys. The faces are all 120 also.

 

Good news. Keep up the maintenance intervals and she'll last forever.

 

The trick to seeing the compression on all rotor faces isnt to hold in the pressure release button...

Its taking the schrader valve out of the compression tester, It will be on the end that goes into the sparkplug hole. The valve is identical to the valve in a tire stem, so if you cant unscrew it with a little screwdriver, go find a valve stem tool.

With the valve out, there is no unwanted pressure loss when the rotor is creating compression. This way, you see the compression on each rotor face without the gauge holding the highest rotor face's pressure.

 

unless you can open and close that Schrader valve on the Compression tester approximately 500 Times per second you will not get a True Compression reading for ALL faces..the only Compression tester that can do that is a Mazda Rotary Engine Compression Tester(Specifically made For Rotary engines).,,Now the Piston Engine compression tester will give you the Average of the Three faces of the Rotor..The engine will run on One rotor!~..not smoothly,but It will run!..(mine ran with 30 psi on the rear and 110 on front!~).you can get a good Idea of your "internal's condition" from the Piston tester,but Not a true reading...Oh 120?..you are In GOOD shape Man!..lots of miles Left on that engine..Just Maintain the thing and all should be Well!

 

Why would the valve need to open and close?

If there is no valve on the compression tester, its identical to screwing a pressure gauge into the sparkplug hole, which leaves nothing but the seals in the rotor to leak pressure.

Although with the gauge you wont have a recall feature of the compression on each face, but watching the needle bounce will show you the pressure made by each rotor face.

It may not be the ideal tester, but I can gaurentee you it wont average the readings.

If a side seal is lost you will get 2 good needle bounces in the 90-120psi range and one much lower.

If one or more apex seals are gone you may see 1 good needle bounce, and 2 low readings, or all low readings.

If the engine is good, you will see 3 even pulses...which will give you a prety good idea that nothing is terribly wrong.

Sure it wont record the readings, but who cares...the tester will cost you next to nothing at your local automotive parts store.