Any tips for a compression test ??

[Tiger-G]

Hi All 

I'm trying to find out why I have an oily rich smell from the exhaust on my 2006 955i, and have invested in a compression tester to find out whether the rings are worn.

Anyone got any tips for doing a compression test ?? So far I've got make sure you have the fuel injector fuse pulled, have the throttle wide open, do it while the engine is hot.

I'm also going to do it with the engine cold, and with a little bit of oil squirted in the bores just to see if there's a marked difference in compression.

Anyone know what the compression readings should be ??

Cheers  :icon_wink:

[Timbox2]

Triumph dont seem to specify an actual figure for compression, I cant find it. From memory around 140 and up is ok, but more importantly your looking for any significant difference between the 3 cylinders.

[Tiger-G]

Thanks Tim  :icon_wink:

Got round to doing my compression test today, on what is a cheap and cheerful tester that I don't expect to be 100% accurate. The results were quite similar for both a cold and hot engine test:

For pistons 1 - 2- 3.

Cold engine: 105 - 110 - 100 (pretty poor IMO  )

Cold engine with engine oil added to cylinders: 140 - 140 - 140.

Hot engine: 110 - 110 - 110.

Hot engine with engine oil added to cylinders: 140 - 140 - 140.

Looking at a good few videos online for Triumph engine compression tests, they are all above 150psi on a cold engine, so I guess my piston rings are worn. The increase in PSI with the addition of engine oil to the cylinders pretty much backs that up.

Thanks Triumph for your crap piston ring design   

[JayDub]

I don't think those specs are very bad, ring/bore wear doesn't come up that often even on Triumph triples with up to 100k mls on the clock.
To be fair to Triumph, its 11 yrs old and the condition of it now is more down to care and maintenance given by the owners (or not). 

[Sin_Tiger]

Don't be too hasty blaming ring wear, how are your valve clearances?  Again, you said yourself "cheap and cheerful tester" 

Main thing is consistency across the cylinders, I don't think you should be worried.

[Tiger-G]

Thanks chaps, that's a bit more reassuring. Checked the valve clearances tonight, and they are all just in spec.

I don't have a car at the mo, so the bike is my only transport. So unfortunately, I'll just have to put up with the rich oily smell, loss of oil, and poor MPG, as it will be too much hassle to replace the rings and valve oil seals.

I'm tempted to change the O2 sensor to see if that improves the MPG a bit ??