compression tests

[drewjak]

hi all , just bought a 325i as an engine doner, on looking through the history of the car i noticed it had its compression readings taken a few times,an im just wondering if any one can enlighten me as to weather or not these figures are good or bad, and what they would have been when new?(its a 1988 car)

at 88,812 miles(4/8/98
1..175psi
2..160
3..175
4..160
5..180
6..160

at 103,349 miles(19/1/2001)
{a tig air filter & a full scorpion system were added at same time but dont say if readings are before or after?}
1..155psi
2..160
3..170
4..180
5..150
6..175

at 108,073 miles(9/11/2001)

1..140psi
2..160
3..160
4..160
5..160
6..160
the car has currently done 121,000,smokes a bit, but seems to run and idle perfectly.but also runs very rich???
the last 2 sets of readings (within in ten months and 5 thousand miles) seem a bit odd could this be due to the filter and exhaust? or is the thing fecked?

[DRIFTBOY]

The main things that affect compression readings are the compression ratio, condition of piston rings / bores and valve seating and the temperature of the engine when the readings were taken.

Also if the measurements were taken with the same compression testing tool, as some are more accurate than others.

Those figures, although a little uneven, are not terribly low so I, personally, wouldn't worry with those.

Sorry, I don't know what the readings on a brand new engine should be though.

The smoking could be due to it running rich.
Best find out why it is running rich!

Just bung it in and thrash it! It'll be ok!