Blue Smoke/Low Compression on New Engine
Turbo Mini Forums

Hey All,

I am FINALLY getting around to getting my Mini going after a lot of fits and starts with it. I'm getting issue now with lots of blue smoke after the car runs for a while. I'm 95% it's the rings and I'm not sure what to do.

Basic overview:
998c engine bored +0.040
12g295 head with new valve guides and seats
gt1548 turbo
HIF44 carb

History:
Took me a while to sort out ignition/fueling initially but eventually got it running and ran it for the recommended cam bed in time (~2500 RPM for 20min). This was the first time the engine ran since rebuild.
Changed the oil, messed with it a bit more and have no been driving it a little bit. Mostly pretty short drives as I sort out clutch/ignition/timing/brakes/etc. It runs pretty well, making solid 8psi boot and makes enough power to keep me happy. BUT! It is pouring out a considerable amount of smoke after it runs for a while

Issue:
When I drive the car it's pretty clean at start but then after driving for a bit if I stop and let it idle, it starts to make a pretty good size cloud. It's obviously hard to tell if it's doing the same while driving. When I get on the gas from a stop it also seems to leave a cloud behind.

Things I've Checked:
Valves: No noticeable play in the guides and I do have seals on them
Turbo Leak: Possible since I had an oil over pressure early on but the intake tubes are totally clean. Haven't check outlet yet
Compression Test: This doesn't seem good
#1: 70, #2: 75, #3: 75, #4: 90
I added a bit of oil to #1 and go it up to about 140
Oil Pressure: Runs at ~35 when warm at idle
Breathers: I think I need more breathing since I only have the one on the timing cover. I can feel air pushing out when I take oil cap off.

From what I've read this is likely an issue with the rings seating but I'm not sure how I can fix it (if at all).

I've moved across the country from the machine shop I had the engine done at but it was a pretty well respected shop.

Appreciate any advice and help

the oil in the bore test caused such a massive change it really has to be a ring or bore issue imho.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

id have to agree

losing half your compression is a fair bit!! are you sure its not a head gasket? did you have all 4 plugs out at the time of testing?

i had an oil burning isue with my first build all fresh parts and bore hone the lot
what i found out the hard way was

first the ring installation onto the pistons i twisted the rings on that is when putting them on the pistons i sat one end in the grove and rolled the ring over the top of the piston this made them get a twist that made them not free to move this was not really apparent as they still felt "free" but they did not drop under there own weight when the piston is turned over if that makes scene they should really flop around with zero resistance if they are anything but they may not rotate in the bores and may not bed in correctly

second thing i did wrong was to use to much oil on the bores pistons and rings when assembling them i simply used WD40 ! and it was mint

third thing was when i started it i got the revs up to the prescribed 2500 or so yep that was good its what the cam needs tick but after the 20 min or so i let it idle!!! bad dont let the thing idle if you can help it the first start should be as follows start it set idle up 2500 go over the car lose bolts leaks after the 20 or so mini shut it off check fluids leaks then start it and DRIVE IT dont be soft on it but dont go flat out at the poor thing just load and unload the engine change its rpm and load but minimise idle time for the first 5-10 hours of run time

that engine had 180psi on all 4 and didnt burn oil

id still be using it if i didnt have fuel and ignition problems that lead to a melted piston!
so make sure your happy and comfortable with it all or just spend the money and have a shop set the thing up
trust me its easy to make a simple mistake and a second or two with it running under power with an unsafe tune will cost far more than the rolling road and half day tuning to set it right in the first place!!

I agree with Denis but you ought to do the oil down the bore test on all 4 cylinders to see if the large change is on all 4 and you should do the tests both cold (without oil and with) then repeat when at full temperature so you have 16 readings to compare.

Then to be certain, a leakdown test.

Schrödinger's cat - so which one am I ???

Yeah, I think it really is a piston/bore issue based on the feedback here and the tests. I will repeat on the other cylinders just to verify but it seems pretty conclusive.

No idea where to go from here...It's a new engine, does it need more break in? Probably has ~2hrs on it.

If not, what do I do? I feel like I have a good handle on most other issues now but not sure where to go with this one.

Thanks!

I'd certainly try working it hard see if it does need more piston ring bedding in.

Schrödinger's cat - so which one am I ???

the whole point of loading the engine is to create cylinder pressure to push the rings against the walls to "wear" them in
but this only works while the bores have the fresh hone cross hatch after a short time the majour peaks have rubbed off somewhat
also if the whole thing has to much oil when built up they rings kinda hydro plane so it only need a tinny bit when building once its started and runs the oil it needs will be flung up from the crank rods as it runs

myself if everything else checks out fine like no head gasket isues and your happy with the tune id go find a quite road and stick it in 2nd gear and give it like 75-90% throttle up to like 4500 then lift and let it coast down to like 2500 and repeat a bunch of times just be careful where you do this and keep an eye on the wideband make sure the timing is safe to

if the smoke isnt to bad maby you can live with it for a while and see if it gets less as it gets some spirited hours put on it

I have had 3 builds that breathed heavy from fresh over the years. a good kicking helped but never fixed it, once a heavy breather always a heavy breather IMHO. Solutions for me were a rehone and run in with mineral oil, new rings suspected tension was weak(or rings just plain crap) and in once case a rebore as the cylinder was oval best I could measure. was obvious when honing as there was a weird pattern of high and low spots.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Thanks for the advice all.

The boring/honing was done with a machine shop but I installed the pistons myself. It seems like something might have either been done wrong in the install or the bores weren't done right. I went out and drove it a little heavier last night. Did some 2nd and 3rd gear pulls and it's definitely not smoking as much on start up but still when I idle for a while at the end of the drive it started smoking again.

Took some more measurements with compression gauge and also did a leak down test:

Compression when cold (psi)
#1 75 (add oil-> 150
#2 75 (add oil-> 160
#3 75 (add oil-> 110
#4 90 (add oil-> 130

Compression when hot (psi)
#1 80
#2 85
#3 80
#4 80

Leakdown Test when cold (Input 90psi)
#1 88psi
#2 87psi
#3 87psi
#4 87psi

During the leak down it was pretty clear that the air was going past the rings since I could feel a little flow out of the dipstick hole and the filler cap. I think that given how consistent the results are across cylinders it must be a ring/bore issue.

This car has been quite the project with lots of set backs. Seems like my best bet here is to maybe drive a bit more but should plan to take the engine out yet another time. Bummer.

what style of oil controll ring did you use? I find the (easily snappable) 2 piece type, where the both scrapers are one piece with a spring behind them are very intolerant, that said if the bore is true, sized and finished correctly there should be no issue with either style.

Any chance as you fitted the pistons yourself and your in the USA where engines are generally much bigger, the machine shop bored a little too much because they either didnt have your pistons to measure, or used a rule of thumb for clerance that doesnt really work with itty bitty engines like ours.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

This is the piston/rings that I used:
http://www.minispares.com/product/Classic/P22463-40.aspx

Your theory on the machine shop could be correct, I gave the shop the pistons but I didn't chat with them about clearance and just trusted them to it. (maybe a stupid move)

Those are insanely low pressures...sure it's even the right size pistons for the bores ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Did you measure the ring gaps (rings in the bores by themselves) before you fitted the piston/rings ?

That measurement would give you a good idea if the machine shop did the bores too big as per Denis's suggestion.

Those readings above being so consistent (apart from No.3 where you probably didn't put as much oil in or it ran straight through the gaps) do say it's a ring/bore issue I'm afraid.

Schrödinger's cat - so which one am I ???

rings upside down ? (if its a design of ring where that makes a difference )

Edited by robert on 14th Jun, 2017.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

also I seem to remember somone getting a ring pack included with their pistons that was for the next size up, so had big ring gaps and bugger all ring tension.

Okay well, I took of the head today to see what I could find. Here's what I got. Is there anything else I can check in this state or is the short block destined to need to come out.

Positives:
Head gasket looks not busted
Valves look okay
Cylinders/pistons look relatively clean

Negatives:
It looks like the pistons are backwards?? I thought I messed this up and then read it didn't matter but just looks dodgy. Which is does but is this a potential root cause?
I noticed a vertical line in one of the bores
Bores still look to have some cross hatching

I would say those bores are very shiny for 2 hour runtime only. those vertical lines are difficult to see in picture, but does not look bad to me.

As above, I've seen cross hatch honing still visible on engines after thousands of miles.

Also, what little is visible doesn't look like the right angle, I can't remember what the usual angle is (30 degrees rings a bell) but certainly more than that.

Don't know enough about 998 pistons to comment, orientation is usually only specific if the gudgeon pin is offset or the skirt is a different width on the loaded side. But I guess the arrow is there for a reason.

EDIT - my memory is going, I looked it up and cross hatch angle is usually 45 degrees, not 30 like I said above.

Edited by Rod S on 15th Jun, 2017.

Schrödinger's cat - so which one am I ???

have you a spare piston you can measure the skirt of, then pop it in the top of the bore and see what size feeler gauge you can get i the piston to bore gap ?

on one of those pictures , is there a black mark down the bore from the top black ring ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

the vertical line is the ring gap ether the ring is not turning free or the ring had a burr on it when installed

if you can id try get the rings off the pistons with out breaking them and stick them in the bore so u can see what the gaps where relatively ie top gap is x and second is x+2 thou or so this is important! the actual gap is not as long as theres enugh that they dont butt due to heat there are lots of cars with massive gaps that dont burn oil as its a labrenth seal ie the chance of all the rings gaps being in like for more than a few hundred rpms is slim the rings should all turn both difrent ways and speeds so the path for gass to travle is long and to top that off whats the piston to bore clearance? around a few thou right? and the ring gap about the same so that makes a square thats a few thou and the time when the piston is mid stroke not long at all in short my opinion is that its the relationship of the first second rings gap not the amount of gap

imo ring gap is not to inportant as its a labaranth seal so long as there is enugh that they dont butt from heat in most cases your fine one thing to add is the second ring needs a few thou more gap than the top! as the gass that dose pass the first needs a free path to the crank case or it may float the second ring letting it pass oil


as said the bores should have that X pattern to the hone marks the hone job is like a temporary file that perfectly matches the rings to the bores but the window is really short to get the work done as the sharp peaks of the ridges and valleys wear really fast but the low parts the valleys stay there for much longer as also said

just be sure the head bolts are not under or over torqued also as this can distort the bores

Okay so I do have a spare piston with rings. Here is what I plan to do when I get the next chance:

-Measure the piston and try to use feeler gauges to get the gap between piston and bore
-Try and come up with an ID mic to measure the bore
-Fit the rings from this piston and measure the gaps

I installed the pistons about 3 years ago (maybe more)...it's been a long project. I don't remember checking the ring gaps but that doesn't mean I didn't do it.

My 998 pistons from calver had a correct orientation, the pins a not in the middle

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Those bores do look as though they have suffered fuel wash....... How rich was rich and for how long before it was fixed if at all? You can clearly see the first, second and oil ring wear pattern in the hone on the bore

Pistons do look like they have been installed the wrong way round. Arrow normally points to the front of the engine ( timing chain end), but I doubt it would wash the bores like that.

The vertical marks could just be the ring ends, but it could be a broken ring or even the piston pin or the retaining clip, especially in that position in the bore

In my opinion, this is a fresh hone and a new set of rings. Run it in 'hard' on mineral oil for at least 250 miles.

After a fresh hone, change the oil immediately after the first engine warm up, then use the correct grade running in oil where available. Change the running in oil regularly until you are satisfied the engine is run in. Usually the colour of the oil will tell you when this is if you change it at the same short intervals as each other. After that, use the best oil grade available for the engine. In the UK This would be Millers CTV 20W50.