Just done one today reason being it smokes blue on overrun and wan't to rule out the rings, warmed engine up for 10 mins and each cylinder was between 130 and 135psi.
This is on a fresh 1.6CVH MFi engine with 250 miles on the clock so far, head skimmed, block decked and new +0.5mm oversize Mahle pistons (not sure if they were low comp or not).
Anyway are these values good for what I am looking at or should I have let it warm up for longer? Or do I still need to do a wet comp test to further rule out ring damage?
It never smoked before the build so don't think the valve guides have suddenly gone and hope its just something simple like stem seals instead.

 

what oil are you running it in on?

 

Turbo seals ?

 

Used Millers running in mineral oil for turbo'd cars dropped it after 150 miles and put Mobil semi synthetic in and done another hundred or so miles since. Turbo was new in January and never smoked before the rebuild and has been off the road pretty much since then until I got it all back together recently.

 

I read on rsturbomania that fresh N/A engines should be about 180psi and turbo'd cars should be around 130 to 150psi due to their low comp design compared to N/A.

 

you need to drop your oil again and put some cheap mineral back in it the engine is not run in properly yet and the bit of blue smoke how much we talking a puff or a bit more

 

Builds from a puff into a cloud very quickly on overrun and fecking stinks! Then goes away back on the accelerator.

 

ring problem it sound slike to me or if you're lucky stem seals.
i have 150psi on three and 135psi on one on my 1.8zvh, i know one ring is on way out but only side effect is heavier breathing and oil surges up breather into pot, i'll be repiping that for the time being lol!

 

It seems a little low to me for a new engine.

 

Agreed, back to cheap mineral for the next 850miles mate. It even gives instructions on the back of the millers stuff telling you not to change to a semi synth or fully synth for x amount of miles.....

Slightly perhaps, but compression usually increases as the running in process progresses. Although it should probably have reached near best compression by now as the rings should have mostly bedded in.........

Rob,

 

Well if it was smoking on boost as well I figure that would be the rings gone but its smoking big time only on overrun and a little after its warmed up.

I checked the hoses earlier for any oil in them but they were dry.

Think I agree with the oil change and while am at it gonna change the stem seals as I got that nifty tool for doing it with the head on. They are only a few quid but gonna try and get genuine Ford if possible. Halfrauds have got some sh1tty 15W40 mineral oil for £15 so why not.

 

Not a bad plan... try a google on 'blow by test' or 'leak down test' and ignore the links to suspect looking porn.

Rob,

 

 

i'd be happier with 150psi+ across the cylinders mine when freshly rebuilt was 155 on two cylinders and 160 on two.

 

Just for comparison mine were 175psi give or take across all 4 after being run in.

 

How many miles had you done before considering it run in, 1000 miles? I have only done 250 so far but not mad keen on driving cos of the embarassing oily cloud that follows me!

 

I did 1000 yeah mate, all on the Millers running in oil then changed for Silkolene Pro S 10/50

 

So there is a possibility then that I have not reached max compression yet due to its low mileage.

 

good luck with this dude.i run around 130 to 145Psi and that was fresh built,pulls spot on! I do find turbo cars running over 160Psi a bit extreme.But alot of people tend to run slightly higer comp pistons for quick low end grunt,less lag.But i dont have that problem.I ran 5/30 for bedding in and turned boost down to 5Psi for around 700Miles.Changed oil few times during the 1000Mile bed in period too.

 

A comp test tells you nothing about your CR mate, my 7.5:1 low comp accralite build was also around 170psi on all 4, and my current one is stock CR of 8.5:1

 

what does it tell you then.lol

 

Well if you know what it should be then it tells you how worn your rings are, or if your valves are not sealing properly.

 

Yeah i understand that.but i had full rebuild by ford themselfs and i was getting 145 And one was 130 odd.Car pulls very strong.I didnt run the engine before compression test,well as far as i remember.

 

Oh well there is your problem! lol
Car should have been running and up to temp before doing the comp test.
But if they are that low and vary by as much as 15psi then something is wrong.

 

lol agreed, however a car with a higher compression ratio will have a higher compression test value.

Rob,

 

In theory it will yes, but there are too many variables that effect the comp test to be able to accurately use the results for guessing the CR.

 

oh yea, you cant guestimate the cr from a compression test agreed, just generally a higher compression ratio on a good engine means a higher compression tester reading.

Rob

 

Nothing wrong here lol.She runs fine.But i will of course do the compression test after running.