I just had a full PPI done on an '01 996 TT Tip.

This included a compression check.

The numbers on the fax I received, look like this:

1 190
2 189
3 190
4 191
5 190
6 191

What do these numbers mean and are they good/bad/indifferent?

Thank you for your input.

 

These are numbers showing PSI in each cylinder and what you want is them to be all virtually the same +/- 5%. I don't know what the PSI should be but the closeness of the numbers is a very good thing. Equal is always better even if the compression is down a bit. Sounds good to me so far. That seems about what a 9.6 compression engine should be showing.

 

Thank you for clarifying that.

Patrick

 

Those numbers look great.

 

I don't think a P dealership does this kind of test, but a much more meaningful thing to do is a cylinder leak-down test.

The compression testing is good for providing relative numbers from cylinder to cylinder, and yes, close numbers are good. There are some variables that are introduced in compression testing, such as condition of the battery, amount of crud and crust on piston domes, etc.

The leak-down test pressurizes each cylinder individually while locked at TDC and with a guage, helps to tell where the leakage is occurring, i.e. past the rings into the case, past a gasket into the coolant system, out the exhaust valve, or the intake valve, and so on. All cylinders will have some leakage but the percentage should be a low number for a healthy engine.

 

You can also alter the outcome of a compression test by adding a drop of oil in each cylinder, which would boost up bad numbers.