Just got a PPI done on a 360 with compression test. Everything seems to check out but just want to reassure myself before trying to pull the trigger on this one. The readings came back as the following: Cyl 1: 165 Cyl 2: 165 Cyl 3: 180 Cyl 4: 165 Cyl 5: 185 Cyl 6: 180 Cyl 7: 180 Cyl 8: 180 This was done at a Ferrari dealer and the service tech told me they did a dry test Any feedback is appreciated!
I had posted a similar question last summer when I was purchasing my car regarding my results. From the feedback that I received, there are many variables that can have an affect on the numbers such as test method, engine temp, etc. Etc. etc. The opinion of those who commented was that consistency between the cylinders was more important than the actual numbers .
As a general rule of thumb, the numbers should all be within 10% of each other. The actual number will vary by the gauge, temperature, etc. I have two different gauges and they read differently... one has probably been dropped.
Compression numbers will vary from gauge to gauge. Did they do it with the engine hot? Did they have a battery charger connected to the battery in order to keep the starter cranking consistent. How many revolutions did the technician crank the engine on each cylinder? It looks like they did not know what they were doing, as those are the lowest compression figures that I have ever seen for a 360. Typically they should be around 210 psi. I also inspect the spark plugs for coloration and carbon build-up. Even coloration (light tan) indicates even fuel mixture, carbon build up indicates oil burning. Plug inspection is just as important as the compression test. If they really did the test correctly with a good gauge, then I would say that the motor is worn out or has problems. My guess is that the test is not valid.
The other thing that is strange is a that all Ferrari dealers are required by Ferrari to use a Picoscope to perform compression tests on used cars for powertrain warranties. The picoscope test is very quick and only requires the removal of one spark plug. It is very accurate. https://www.picoauto.com/library/automotive-guided-tests/relative-compression-petrol/ https://www.picoauto.com/library/training/compression-testing
I was about to ask that question ..do we know if that process was used or a manual plug by plug process Sent from my moto g(7) using Tapatalk
My compression results were even lower using a picoscope, in the 145 range however the variation between cylinders was very close. Here is the link to the thread where it was discussed before my purchase. https://www.ferrarichat.com/forum/threads/ferrari-dealer-did-compression-test-numbers-low.582948/
Most important would be the service tech's opinion based on experience. Compression test is a reference tool only. Wide variations based on instruments, procedures and test conditions.
