Just got a compression test on my 178,000 mile GSL-SE 13b engine. The results are as follows:

Rotor 1 8.7, 8.8, 8.8
Rotor 2 8.4, 8.6, 8.6

The tech said brand new they run around 9.5 and you start to get in trouble around 7.5. Sounds like my engine is very healthy. Am I right or wrong? Would you have a problem buying this car with these compression numbers?

 

here was mine around 104k on the ticker last year.

Front 7.3/7.5/7.3 - 341 RPM
Rear 7.5/7.7/7.9 - 348 RPM

still running good

and my 84's test way back in 97

7/30/1997 Compression test 7.6/7.7/7.8 - 8.5/8.6/8.5 - 105869 miles

 

Forgot to add the RPMs, Rotor 1 288, Rotor 2 283.

Don't really know what these numbers mean. Can someone enlighten me?

 

does that relate to the stock compression ratio being rated at 8.9 I beleive?

would that be "perfect" or are these numbers unrelated?

 

Thanks Max7, anyone else have numbers to compare or an opinion?

 

I'm not really sure, but i think the units for those numbers are 'bars'...

 

Yes, these numbers are related to compression. The gsl-se has 9.4:1 compression rotors. And one bar is approximately 1 atmosphere of pressure. Actually, one bar is equal to 0.987 atmospheres. This means at sea level with a perfect engine, the readings should be 9.4/0.987 = 9.52. So, one could say that the compression reading are apporimately equal to the compression ratio. As for the RPMs, there is a curve in the FSM and I think the Haynes manual that says what the compression should be for a given cranking RPM.

Hope this helps.

Kent

 

thanks!

 

Nope, compression ratio has nothing to do with ideal engine compression. It is very dependent on cranking speed and altitude. At sea level and 250rpm cranking speed, a new motor will show a reading of 8.5 or slightly higher. The numbers posted for a 178K mile engine seem awfully high.
P.S. compression ratio is just the ratio of intake volume to the volume of the combustion chamber and it represents how much the air is compressed prior to ignition.

 

the best thing to see is that there is no major drop on 1 face. .2 was the largest i saw and thats fine. my mazda tester shows kg and psi on the t2 im helping a fired redo(long story) it hit 113.1 on all 6 faces..COLD and on a turbo thats GREAT hell i think on any motor thats a good # epecally cold...figure 20+ more when its hot