Compression

[mrbilly]

hi all

just done a compression test on my rav, all conditions were right i.e. operating temp, WOT full batt. i was getting avg 115 psi its was 220 psi when i got the car at 76,000 mls now car has done 132,000 miles and i got lpg fitted at 86,000 mls. when i add a bit of oil its increases it to 135 psi. i was wondering if its worth checking the tappets.

any ideas

thanks

[crofter]

Is that average figure about the same in each cyclinder?

Did you add the oil through the plug hole?

If so it sounds to me like wear on the piston,rings and bore so no amount of tappet adjustment will alter that.

Not good news for you,I'm afraid, but thats my "guess"

Del

[mrbilly]

yep oil in the plug holes.

its not the slight psi increase with a bit of oil its more to do with the was 220 now 115 im more concerned about. would a vac check show up ideas

[jedi134]

Is there no way off adding an oil for lubrication to an LPG system, as I do belive the LPG runs dry ie not as much lubrication as petrol, I have heard that LPG can wear out engins quicker, but just though this was rummor?

Air tools have a seperate oil supply to lube them.

[mrbilly]

i have flash lube fitted which oils the valves to keep them cool. i didnt know what your were on about with air tools

[mrbilly]

the performace seems ok thats the strange thing

[jedi134]

I think your flash lube may be the same as my air tools description......

How does this lube the engine is it mixed with the gas and enters the cylinder housing with the fuel?

what sort of lube do you use?

[Jamesbelfast]

Pneumatic air tools such as those used in inustry have an oil lubrication system which adds misted oil to prevent premature wear. But as you say such a system is already fitted to your engine.

I doubt very much it would be a valve clearance problem as the chances of all valves being equally affected would be slim.

[jedi134]

the performace seems ok thats the strange thing

Just a really wild guess/stab in the dark........ but because LPG runs cleaner, it may have cleaned the pistons of carbon and as such much more surface area to compress = less PSI measurment.

You could run a tank of petrol through it and test again?

Or The LPG has pooped your piston rings

[mrbilly]

the lube is called flash lube(google it) its supposed to stop valve seat regression like what used to have to a car that ran on leaded fuel but ran on unleaded

[jedi134]

Being lazy and cant be Assed googling does it mix with the gas? similar to what JimmyBelfast said?

[bothwell_buyer]

based on my experience with lpg on Jaguar and Renault engines, my first point of call would be the valve seats and valves themselves. Those engines ran hotter and the valves/valve seats suffered. I think your psi should be up around 160+ but not sure.

Checking the tappets to make sure they haven't closed up again would be a cheap check??

If the engine is pulling OK then I'd tend to leave alone.

Stripping the head off aint such a big deal but if you find if its the rings/bore thats worn then its cheaper just to get hold of another engine from a scrappy.