Is Smog Test Results Good Indication of Compression in Engine?
 

Hi,

I am going to be purchasing my first RX-8 woohoo, and I had a question about smog test results. The guy I am buying it from is going to be doing a smog test on the car and I was wondering if smog test results are a good indication of the compression in the engine? I understand that if the smog test fails it is not necessarily poor compression in the engine, but if it passes the smog test, is that a good indicator for good compression in the engine? The reason I am asking this is because I have contacted 3 Mazda dealerships around me and the quote for a compression test is $220 around the board. Most likely I will end up getting a compression test anyways, but I was curious if anyone knew if smog tests can indicate good or bad compression levels in the engine.

Thanks for your help!

NO....might tell you how well the CAT works though ;)

There is certainly a good correlation between smog test results and engine health, but I don't think there is any real conclusion that you can draw between them with just the smog results. In order to do so, someone would have to test different compression level engines with the same perfect condition emissions equipment and record the results.

Far too many variables otherwise.

See how it starts warm...if it takes longer than when cold the compression is poor. Best spring for a compression test though unless you have the funds for a rebuild

Agreed. Timing the starting time when cold vs the starting time when hot is generally going to be a better indicator of compression, with the closer those times are the better the compression scores.

Thanks guys for your input. Hopefully the compression test comes back with really good numbers. Then I can join in on some rx8 fun!