On an S4 (warm) I recently measured:
1-204
2-200
3-200
4-215
5-214
6-180
7-212
8-202

I don't know if the gauge was reading high or if the ROW S4 engine (it's a UK car) has a slightly higher compression ratio.

Cylinder 6 looks the odd one out but not grossly. I did the 'wet' test with oil on that cylinder and it shot up to about 250psi

It's an '88 with 127K miles.

Adrian

 

cyl 6 would give me abit of worry, and when you did the wet test how much oil did you put in

 

I'm reading this thread and thinking I just got back from a run and there might not be many opps to get her out before snow & ice.............the plugs are out as is the FP fuse..............BRB with the comp. readings.

 

About 15ml - a tablespoon. It may be a sticky piston ring but doesn't seem to be bore wear given pressure went up with the oil.

 

agreed if the reading goes up with oil, it indicates just ring wear, but that is a serious amount it went up by, I would have expected more oil to have been put in there to get that reading

 

I agree and am at a loss to explain why that cylinder magically created a greater than 10:1 compression with the ring temporarily sealed. Will live with it till some other symptom shows up.

 

My readings are very consistant but not from bank to bank:

1~ 4 : +/-170psi
5 ~8 : +/-150psi

Cam timing?

 

Malcolm, yes that is correct to say that your valve timing is off.

Get your hands on porkens valve timing tool and set them the same.

 

I've got Ken's timing tool and set the cams prior to the tbelt project............hmmmmmmmmmmm!


I can reset the cam timing and do another comp test time permiting.....its getting cold.

thx Liz

 

imo it is better to set them when the engine is warm as they do move abit when warm.

 

If only 1ml was needed to seal the ring, you just reduced the combustion chamber size by 14ml... your combustion chambers are only 60 or 70ccs.

A compression test should yield a number 17-22xCR. It seems that below 14-15xCR is bad.

 

But if I have 5000cc and 8 cylinders then each cylinder is 625cc?

 

Stratford.............the combustion chamber is measuerd with the piston at TDC which leaves only the volume between the piston crown and the cylinder head.

 

Doh! Thanks for explanation.

 

So, it is possible to have +/- 10 it seems. Thanks for the info.