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Discussion in 'Engine Queries' started by Berto, October 4, 2017.
Similar piston design inside a Toyota engine:
Berto they don't all use oil - i remember when i first got mine with 66km (about 40k miles) i never topped it up between 15k services there would be about 3.5 to 4l in the pan. Mine only started using oil at about 300km.
Please bear with me for a while Patricks, we'll get to that.
Just to be sure: Can anyone confirm (if possible with good pics of the oil control ring groove) that those two vertical notches (four total) close to the gudgeon pin are the only drain ways available for the oil control ring on standard Z22SE pistons (i.e. no drain holes or slits at all in the oil control ring groove)?:
they are all the z22se pistons have.
I know the z22se oil control rings do gunge up, after about 80k
^ Thanks Vocky.
While we're at it let's have a look at the quality aftermarket pistons that gurus like Vocky use in their mouth-watering engine builds:
Now LET's have a look at a previous generation of GM sporty four-bangers:
this might be total rubbish but I've had my car from new never put any oil in it between services after about 7ok miles started getting oil in inlet manifold and car started to smoke a lot under high revs got catch can which helped for a while would empty about 1 litre of oil a month engine anyway engine dead now I getting another one but was told I need my rocker cover when I removed it. it was full of crap after cleaning I jetted out but there's a plate inside where I think the engine crankcase vents through it has taken nearly 2 weeks of soaking and jetting to clean it out read somewhere if you have to much crankcase preasure it can cause blow by my rocker cover was full
So what's the matter with the frigging holes?
As the name implies, the oil control ring (third ring from piston top) is there to control how much oil remains above them on the cylinder. While the piston moves up and down the bore they scrap excess oil from the cylinder wall, ideally leaving a thin film just enough to lubricate the two upper rings.
If for whatever the reason the oil control rings start misbehaving, the engine will burn extra amounts of oil.
The oil scrapped from the cylinder wall accumulates in the oil control ring's groove, so it must be evacuated from there and returned to the oil pan. And that's what the holes are for:
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Some piston designs even go a step further from the holes and feature long slots for enhanced oil evacuation from the groove, like the old GM 2.0 SOHC 8V engines in the Kadett GSi 8V (Astra mk2 GTE 2.0 8V in the UK):
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And yet the pistons GM put inside the Z22SE come with not a single oil drain hole at all.
Strategical excerpts from discussions about the Saturn 1.9 engine, whose pistons (first video in this thread) were also made by GM with the same design (no oil drain holes at all) ...
"... The Saturn engine was designed to maximize fuel mileage. Th original engine design dates several years before the 1991 model year, that puts it back into the late 1980s. When it was designed the decision was made to use the new 5W-30 oil which improves fuel mileage. But at that time (late 80s) the hot film strength of the oil was lacking. To attempt to control the wear associated with oil film failure at the oil control rings the thickness of that film was artificially increased by design. The design trick was to drastically reduce the oil return from the oil control ring groove. that decision results in oil being retained in the oil control ring groove and oxidizing to carbon.
If you rebuild the engine, add the oil drain back holes the design team left out. ..."
"... the number of holes determines the amount of oil scraped off of the cylinder walls. This is not a simple exercise to determine how many holes and what size. If you scrape off too much oil you are rewarded with excessive cylinder wear. And, not enough and you continue to burn oil.
A high grade synthetic oil has a very high film strength. This means that very little oil is required to provide protection. So, drill the holes and use a pure high grade synthetic oil and all should be well ..."
"... Synthetic oil has a higher film strength and is harder to turn to carbon (burn). Less oil ring plugging ..."
"... As far as the oil consumption issues, I was a Saturn technician for 12 years and there are alot of similarities between the 1.9l and the Northstar. While at factory training in Tennessee, I had the privilege to chat with the powertrain engineers and the topic of oil consumption came up. The engineers agreed the root cause was oil control rings carbon sticking in ring groove on piston due to no drain back holes behind the oil rings in piston.
They told me next oil consumption overhaul I do (I did quite a few), drill 8 staggerd holes behind oil rings in piston. I had a 97 SL2 that I picked up with a blown engine. I salvaged the lower end, performed the ball hone, soap and water cylinder cleaning, and piston mods. The car does not burn a drop of oil and its been 125k since overhaul. I'm going to do this mod to my Northstar as like the 1.9l, the oil drain holes are absent from the factory pistons ..."
"... The reason that Saturn left the oil drain holes out is due to their design goal for a high gas mileage high performance engine as defined as more than 1 HP per cubic inch displacement. To obtain the high fuel efficiency they went with the cutting edge oil technology of the day, the 5w-30 oil.
Now back in the late 80s when this engine was still only on paper there were a lot of problems with the 5w-30 oil. Basically shredded pistons and scored cylinder walls. An oil film failure problem. They were also afraid of the synthetic oils as Mobil was the only kid on the block and the pickup truck commandos were bad mouthing the h**l out of it. so, consciously or unconsciously they deleted the drains and placed a pair of drain cuts on either side of the wrist pin. technology has marched on and this over lubrication is not required and is actually harmful.
In truth it was harmful by the time the first Saturn rolled off the assembly line. hence the oil burning engine. From he late 80s to the beginning of 1991 the additive package for the thin motor oils had been perfected and maintaining a thick oil coat so as to not break it down was not required any more ..."
"... The problem is not excessive oil on the cylinder walls it is the accumulation of carbon in the oil control ring separator. Each of the scraper rings constitutes a knife edge filter, very efficient. The lower ring scrapes on the up stroke and the upper on the down stroke. The oil and carbon lands in the separator area. The flow path to the existing notches is long and torturous.
This results in a low flow velocity, this means the heavy particles sink. So you end up with carbon build up. Now by drilling some additional drain holes in the high thrust areas you provide a path to dump the carbon into the pan before the flow velocity drops. Most oil is scraped off of the thrust sides of the piston. Four large holes will work but 6 smaller ones is better and easier for the home machinist to pull off.
If you want a practical demonstration of low flow velocity take a look at the water saver toilet. ..."
"... without holes you will have more oil on the walls even with new rings ..."
Though Peter Finn's english is almost as bad as mine, his video illustrates very well the nastiness of stuck oil control rings:
The Stucky Horror Show:
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^ The above fossilized ring after excavation =>
Another interesting history about piston holes.
Early Toyota 1ZZ-FE engines were growing a reputation for oil-burners.
Now each car manufacturer has its own ways. When Toyota screws up, they will apologize to the emperor and commit sepukku if necessary:
Toyota 1ZZ-FE service bulletin
Symptom: The oil consumption will start suddenly and increase at an exponential rate.
Cause Of Phenomenon:
The root cause is the sticking of the oil control rings due to degradation of the engine oil.
There are a number of contributory factors:
1. Failure to follow the Manufacturers Service Schedule causes oil degradation.
2. Oil entering the combustion chamber being burnt and carried by ‘blow by’ gas down side of piston as carbon particles.
3. The lower portion of the piston (especially around the oil control ring) runs hotter (160ºC) than target (120ºC).
4. The oil flow in the oil control ring area is quickly restricted by any carbon particles reducing lubrication, cooling and ‘flushing action’. This in turn causes degradation of oil in the ring groove, further accelerating the sticking process.
These factors cause the oil in the oil control ring groove to degrade faster leading to sticking of the oil control rings.
On all models it is necessary to replace the Oil Dipstick with a modified one as per the following details:
Description: Oil Dipstick
Modified Part Number: 15301-0D011
Difference: Green dot on the pull ring
Increases oil capacity by 0.5L
Piston Production Improvement:
1. Increase the number of oil return holes from 4 to 8
2. Add a slit to the ring groove
These changes are designed to improve circulation of oil around the lower portion of the piston.
• prevent build up of carbon deposits
• improve cooling due to increased flow of oil
^ The problem was too few (4 total) and too tiny oil drain holes in the groove. Later 1ZZ-FE pistons (left) came with eight larger holes:
The aftermarket is well aware of these OEM screw ups:
Unfortunately GM's recommended service (oil change) interval for some models (including the Z22SE) of 20,000 miles or 1 year (whichever is sooner) was too long as owners covering high mileage neglected doing interim oil changes. However I suspect few owners ever reached an annual mileage of 20,000.
In 2002 the average annual mileage for a 4 wheel vehicle was 9,200 and by 2013 had fallen to 7,900.
If a vehicle has a good service history then regular oil changes (every 4-5K miles) using a fully synthetic oil should keep 'oil burn' in check.
If a vehicle has been neglected regarding servicing and oil changes then it is likely that contamination and a build up of 'sludge' will have occurred, with the piston oil control rings becoming 'gunged' up. Fortunately this condition can be treated by products such as Forté Advanced Formula Motor Flush.
Also available Forté Oil System Protector (reduces oil burning) and Forté Oil Fortifier
Wholly agreed, 20K miles (~30K km) is a far too long OCI (Oil Change Interval), bad recipe for engine longevity.
Quality synthetic oils sport a higher flash point (= less susceptibility to carbonization) and contain detergents (solvents) that help in keeping engine internals clean.
But the thing is, OEM Z22SE pistons, even brand new in pristine condition, will pass extra oil to the combustion chambers. And are far more susceptible to gunking up in the long term. By design.
Now that KevinH has opened the can of worms we may discuss magic treatments for loosening stuck oil control rings.
Haha, yes a 'can of worms' indeed.
Although engine flushing shouldn't be a necessity if regular oil changes with a quality fully synthetic oil are carried out, it will not do any harm as long as the manufacturers instructions are followed.
I have used the Forté products before and do recommend them, but they are not the cheapest on the market and I'm not saying other products won't achieve a satisfactory result.
I've heard good things about this product:
Sounds like a serious chemical carbon solvent for ring soaks.
i agree with this, IF the oil is changed regularly they don't burn oil until they reach higher mileage's.
had mine from 10,000 miles at 6 months old and it had had 1 oil change before i got her.
i used 10w40 semi synthetic oil and changed it every 5,000 miles, got to 117,000 before engine was striped for power gains (flowed head) and only using 0.5L oil in 5,000 miles.
only measurable engine wear was on no4 bore, it was close to tolerance for ovallity mid stroke. still under but close. no noise from timing chains or lifters and she was running DBilas cams at that time (bad choice)
yes what your saying is right, if manufactures had made the pistons better, spent more money on them they would last longer before needing overhauling.
but also if the owners cared for their cars more they would last even longer still.
20,000 miles is way to long to leave the oil in for most peoples cars, engines that don't get cold that are run for long hours each start up can go longer on oil changes. your average shopping cart car how ever goes through many hot cold cycles between oil changes which breaks down the oil faster than those engines that stay hot for longer.
i used to work for a bus company and the Volvo B10M engines would see 500-750,000 miles before needing overhaul with 20,000 mile 3-4 weekly service interval on semi synthetic 15w40. these buses did 20-22 hours a day with out being switched off, just for a turn around nightly inspection and clean. they would still have minimal oil burn.