Excessive oil burning, oil jets, stuck rings, acetone
 

I tried to cram as many search words as I can in the title.

Backstory:

* ~29K miles since rebuild (summer 2012) with new 84mm JE pistons and rings, Mtuned rods, bearings, the whole nine yards..
* >2K miles on the head with brand new everything - valves, springs, seats, guides, you name it.
* Progressive port water injection
* MP62 supercharger / TDR IC
* Replica Gibb 4 into 1 header, resonator, Borla muffler. No cat. 2.5"

Daily driver, driven fast, two track outings on the engine.

I noticed the car was using some oil about a year or so after the rebuild. Didn't think much of it. Boosted engine and all.
Then, it started getting worse. I was adding about a quart between oil changes. (less than 3K miles)
That got progressively worse. Up to 4 quarts between oil changes.
Got to a point where I was shooting blue smoke every time I got on the gas. I would be cruising, and I would give it gas to either pass someone or get ahead of them, and there would be smoke all over.
And, in the past few months, oil consumption was up to a liter in about 200 km (~120 miles). Whoa.

I never let the engine starve, carried oil in the trunk and always topped it off to be safe.
And, it bothered me. A lot.

I would start the car, keep the idle high, and as the idle climbed smoke would be billowing. Red lights were a smoke show.
The engine had power, and performance did not suffer, tho.

So I started searching. Had to be the rings. "New" rings I had taken all that time to seat properly.

My search pointed at oil jets as a possible culprit.
I have JE pistons which are quite similar to Wisecos with the oil drain ports on the lower lip of the oil control ringlands, and the jets supposedly shoot their load right between those rings, overwhelming any "control" function.
Anyway.

I borrowed a leakdown tester, and promptly found out the second "percentage" gauge on the tester is busted.
I used it anyway.
The idea was to at least to pinpoint where the leak was, and screw the percentage for now. I know it drinks and farts oil.

All four cylinders leaked past the rings. No noise/hissing at intake or exhaust, no bubbles or anything at the radiator neck, but plenty at the oil filler neck and the dipstick.
Funny thing, if I put the oil cap back on while listening through the dipstick, it just gurgled for a while.

I did a comp test, too. Results were within 1-2 psi of each other, and pretty much identical to a previous test I had done back when the engine was fresh and healthy.
So, top rings are good.

Must be the oil control rings. They could be stuck for all I know.
After all, I DID read about how oil from the jets getting between the rings could turn into varnish, harden and cause the rings to stick.

As the next logical step, I poured liberal amounts of a homemade penetrant into each cylinder (about 1/2" deep), rocked the engine back and forth a bit, put the plugs back on and left the car to sit overnight.
That could maybe, possibly, free up the stuck rings. If they were stuck indeed.

BTW, homemade penetrant is a 50/50 mix of Dexron 2 ATF and acetone.

Long story short, after I cleaned out what little "penetrant" was left in the cylinders the next day, I ran the engine to burn off the remaining ATF and get it up to temp to change the oil.
I used Mobil1 10w60.

Then I took the car out for several test drives.

Holy crap. ​

The car does not smoke. Well, almost does not smoke.
I drove for 45 miles, and saw smoke 3, maybe 4 times.
And, I was trying to get it to smoke, by flooring it, driving in high RPMs, the usual smoke producing things.
Checked the oil level, just fine. It should have gone down on the dipstick by now.

So, I am somewhat happy that my diagnosis was correct (oil control rings are the culprit), but also bothered by the fact that I need to pull the engine again.

Here's the plan:
Pull engine, check PTW clearance, hone cylinders, install new rings, REMOVE the oil jets, break engine in again, profit (not).

I already have 84mm pistons and I do not want to shell out big bucks again if PTW clearance is unacceptable.
If it turns out to be too much, I will just sleeve the block. (Can't find a block here, and block sleeving is cheap, like less than $100.)
PTW clearance should be 0.002953". That's what the engine builder had told me.

I already ordered a full engine gasket from Fel-Pro and a set of JE rings.

Will keep you guys posted about how things unfold. This thread will not be be updated frequently, I need to find the time to tear the engine, do the break-in, and accumulate miles to get meaningful results.

Just posting this here to keep open records, provide info for others and approach this in a logical and scientific way with your input.

Hope your does not smoke like mine does did.

Nice diagnosis and trial, I have spare blocks, but I noticed you're in Istanbul. Didn't that used to be Constantinople?

How's this penetrant work?
I'm assuming you drained the oil beforehand and flushed after the penetrant?

I see what you did there ;)


Cheers to OP, I am glad you found a temporary solution to the problem.
Very glad you tried to cram a bunch of search terms, will definitely help people in the future, giving a solid reason why they should remove the oil squirters on aftermarket pistons.

I'm going to try this.
Getting rid of my squirters cut down my oil consumption by a bunch (about 1 quart every 2k miles down from 1 quart every 1k). Have supertech's with oil drain back holes. Also run an mp62 with 63mm and 140mm pulleys... 14psi @ 7200rpm.

My belief and experience. Most aftermarket pistons don't work well with oil squrters. The gas ports for the oil control rings are done wrong. Stock pistons don't have gas ports connecting between the underside of the pistons and the oil control rings. the oil pressure squirting on the underside of the piston goes out those gas ports and completely fills up the oil control ring groove.

I also think that ceramic thermal barrier coating the top of the piston works. I think it works better keeping the heat out of the piston than trying to cool the piston from the underside by squirting excess oil at it.

Note the design of the pistons mazda put on the 323 GTR.
1) Compression ringland portion is cast Iron, Strength ready for all of it boost levels.
2) Oil squirters actually shoot into a hole routing it through a channel that pulls heat from the ringland portion of the piston.
3) Gas ports for the oil control rings don't go through to the underside of the piston, they go to the outside by the wrist pins.

As piston design engineer, and can confirm that all of this is right. We have had similar experiences at work, but logically it makes sense. Your oil rings already have a lot to deal with, and introducing tons more oil to them via piston cooling nozzles/inertia and those stupid holes is not helpful. I was super surprised that my Wisecos came with them, and immediately removed my piston cooling nozzles because of it (well that and they didn't fit). I'm of the opinion that they are not needed on engines any of us on this site would build, provided forged pistons are used, because we are not OEMs trying to make an engine last 250k miles. If you look at any plot of aluminum strength vs temperature, note that the material is very sensitive, and why the OEM engine designers would want to use oil squirters. However, with forged material, a there is a lot more margin due to the higher strength.

These comments are very interesting, because you just described nearly every diesel piston.
1. The cast iron ring grooves are added to prevent wear in the grooves, due to high cylinder pressure and soft aluminum, and to keep the aluminum from sticking to the bottom side of the ring when the piston gets hot.
2. Piston cooling galleries are the most effective ways of cooing the piston, and allows you to run really high in cylinder temps without melting pistons
3. Most oil ring drain features don't go all the way through the piston, just provide a small channel to drain oil from the back of the groove, and allows it to drain over the area of lots of space above the wrist pins

As for OP, it could very well be stuck rings, and I hope your method works well, but have never heard of good luck using solvents or other products to get rings unstuck for long periods of time. There are lots of products out there that are supposed to dissolve the carbon, but I never heard that they work for long periods of time.

Good info. Props

To my surprise, the thing worked great.
There's some supporting evidence to the merits of this concoction, anyway.

As for draining the oil beforehand, I didn't.
I figured, by the time this mixture runs through the rings and into the oil pan, the acetone would be long gone.
I waited for almost 24 hours before I did anything to the car, and the really thick goo left in the cylinders sort of proved what I had assumed.
Of course I changed the oil afterwards. I have a special "tilted on the lift" procedure that gets pretty much everything out of the engine. (The car is tilted, with the pass side down, about 30-35 degrees and left there for at least 45 minutes for the last of the oil to run out)

Thank you.
That pretty much confirms my suspicions.

I knew it... ;)
Oh, I DO know my method is not a permanent fix.
I just wanted to verify/confirm my suspicions and use this solvent as a diagnostic tool.
Please read the bottom of my first post.
That engine IS coming apart.

I work for Paccar. though I don't work much on the engines specifically as I do more structural analysis work. My current office space is across the hall from 4 engine test dyno cells and my window looks at the heavy truck chassis dyno byilding that has a climactic wind tunnel built around it capable of dyno testing at extremes of atmospheric temperatures and pressures. I see lots of heavy diesel engines torn apart on a regular basis.

Can you get a miata engine on one of those dynos :)

Off topic:

How do you like Paccar, my fiance is a big fan of bellingham, and I saw that they were in the area.

It's all right. Been with paccar for over 23 years starting at Peterbilt so they haven't pissed me off enough to leave. My wife works here doing engine calibration and operating the dyno cell as well. It's a full service test facility here so structural testing and a full on test track with High speed and durability here as well.

I have a freshly built 1.8 that I plan to install soon. It also has JE pistons. Im getting the vibe I should remove the oil squirters while its still on the stand. It also has a BE pump and shimmed +1. What should I expect as far as difference in oil pressure with the pump and no squirters? Sorry if thats a noobish question. Are there many builds out there with pistons that have oil drain back holes having problems with oil consumption?

My guess, and it is only a guess, is that it would not make a big difference.
Those jets only spray when oil pressure is above 40 psi, and the Miata does not have any more or less oil ports/galleries/restrictions/flow paths in its block and head design compared to other engines.

I did read some accounts of engines with removed jets, and there was no mention of noticeably increased pressure.
Just decreased oil temps.

Not quite an apples to apples comparison but I've just had my motor rebuild with FM Wiescos , I had the squirters removed . Huge increase in oil pressure compared to my old motor. Some of the increase is probably due to new bearings but I'm crediting at least some of the increase to the removal of the squirters.

Thanks for the input guys. Still not too sure yet on if I want to pull them or leave them be. Seems it would make sense to remove them though.

Great info here all, thank you for sharing. Yet another thread proving that MT.net is the best site on the web.

It's possible your decision could be made for you when you assemble your engine. When I assembled my engine (non-FM Wisecos), the piston directly interfered with the piston cooling nozzle. They all would have broken off if I would have left them. I think Bob, Eric Anderson and others have shown you don't need them. However if you want it for the safe feeling, and can potentially deal with increased oil consumption, your engine will still work fine.

My engine is assembled already. :( I'll have to crack the pan and mbsp to get at them again. Yay, redo oil pan.

The JE piston skirts are clearanced for the squirters from the factory. Which is why I wonder if it is a potential issue to run the jets with pistons that have oil drainback holes, that they are made with clearance for jets built in. I want to make the right decision, but not end up with "high" oil pressure because of the shimmed pump and no jets..if thats even possible. That where I'm concerned really.

So when removing the oil jets, do you just let them be have the bolt hole open, or do are you supposed to screw a bolt in. Sorry for the silly question, I'm just trying to do it right. Thanks