Restoring the power of a 1986 110bhp XU92C engine

[SRDTURBO]

Strange results, specially for the number 3

[thefunkyboy]

You should measure again because the C3 value is very strange. It will permit to ensure that it is not an error during the measure.

[amilo123]

twice I measure 3 when hot, once 10.8 and finally 10.5

I don't understand why is there such a difference between hot and cold c3...

[thefunkyboy]

It may be a trouble of piston rings. Did you try to put very few oil into the chamber and then try to measure again?

[amilo123]

i didn't, i will do it tomorrow.
is 14 normal? Is the rate at which it reaches the max pressure relevant? Have you looked at the videos?

[thefunkyboy]

14 is good

I am not sure but I suppose it is a trouble of your valves (piston 3). When cold, they manage to close correctly. But when your engine is hot, because of the metal dilatation, the valve doesn't fit on the same position on this part:


If the valve doesn't close correctly, the pressure will decrease.

[amilo123]

14 is good

And is the rate at which it reaches the max pressure relevant? Or only the max preasure counts?

[thefunkyboy]

I don't know the Peugeot theorical value. But 14, when hot, that's good

[amilo123]

ok, thanks:) I will do it the same tomorrow, and with the engine totally cold, it was a bit warm today...

[amilo123]

oh, and what do you think of the spark plugs?

[missa91]

I agree it has to something to do with the valves. Those spark plugs seem not to be that bad, so I think maybe the valves on cylinder 3 or maybe the oil. Oil viscosity has a lot to do with oil consumption, fuel economy and compression. If the engine is older and has a lot of miles, there is the chance that if you put in it a too thin oil, it hasn't got a chance against the bigger gap that has formed with time.

[thefunkyboy]

Missa, you are talking about piston rings, isn't it?

[missa91]

yes. that somewhere they are worn, and somewhere the oil can compensate for the ware, somewhere not.

[amilo123]

it doesn't consume oil, never had.

[missa91]

And what oil do you use? is it the peugeot spec?