Piston Rings & Blowby - Explained

How do piston rings work? What is blowby? Why are there three piston rings? What do each of the piston rings do? Typically there are three piston rings, and they serve three major purposes. They keep combustion gases from entering the crankcase, oil from the crankcase from entering the combustion chamber, and they aid in heat transfer between the piston and the cylinder walls. The video details these processes, and also sheds light on how blowby occurs, and what happens when piston rings are worn out.
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[@Guitarfollower22]

I like how he began using actual parts to help us easily understand his teachings. Thanks man.

[@AlexdeLarge6655321]

I put new rings on a piston on my bike. I didn't measure ANYTHING. I was so pleased when I started the bike and it ran. It ran pretty well. I did 500 miles on it, including some quite tricky off-road stuff. It smoked a little. It smoked a lot. It used oil quicker than petrol. But it ran. I decided the oil use was more than your everyday break-in consumption so tore it down again and did some measuring. The rings I fitted were standard. I'd assumed the piston was standard. It wasn't. It was a full 1mm oversized. The piston ring end gaps were like the black hole at the centre of the universe. I'm still a bit baffled the bike ran at all, nevermind scrabbling up rocky mountain tracks and a few laps of a race circuit. '85 XT350. Love it.

[@alistuslarter6787]

I bet you had good compression

[@markschaefer5703]

You deserve so many more subscribers, the way you break things down and explain them is awesome. I love learning about and having the knowledge of why engines and processes work. Keep up the awesome work coming from someone interested in mechanics and mechanical engineering!

[@erich.82]

I appreciate these videos you put out, and explaining in such a way that the layman can understand. You are the Carl Sagan of mechanical engineering.

[@Nalopotato]

+mygreenzebra He's not nearly as poetic as Sagan =p Which isn't a bad thing, just a fact.

[@EngineeringExplained]

+mygreenzebra Some of you are too kind with your compliments! Really appreciate it, glad you enjoy the videos!

[@michaelt126]

The piston ring's end gap allows for expansion of the ring due to the engine heating up, much like adjusting valve lash in an engine with mechanical lifters. without the gap, the rings could start expanding outward into the bores and kill the engine. great videos btw, ive watched almost all of them and appreciate the condensed learning within them.,

[@DTRU122283]

Not to mention, on a performance engine the temps are usually higher which expands the rings even more. That is probably THE major limiter on how much nitrous an engine can take, given the tune is perfect.

[@chasemiller7974]

Not to mention also that without relief of the compression through those gaps, the piston rings could have a tendency to crack and fail.

[@jhndijkman]

It truly is amazing how piston rings lasts so long in car engines these days. The amount of work they have done in high mileage vehicle and yet still have little to no compression loss or blowby must be a credit to good design and probably oils that look after these thin little bits of metal.

[@EAGLE13441]

Finished watching all your videos explaining how cars work! Thank you for everything you've taught me, I basically knew nothing before I came across this channel.

[@lukeskyrunner3]

Thank you for this video. I've been looking for a good piston ring video, and this explains them very well! Keep it up.

[@jackiechan6460]

Now, me and the mad scientist got to rip apart the block and replace the piston rings you fried.

[@UndergroundTrev]

No mention as to clocking the rings for proper ring position to ovoid excessive blow by? ( I learned more than I chimed in! Thanks! )

[@MrTheHillfolk]

I installed total seal rings before , and now blowby is minimal. I think I'd have em made for any engine I ever redo. It's also Good enough to have a open crankcase vent and not get gassed out by it inside the car.

[@eddieguzman591]

Thank you man. Really good presentation. Like someone mentioned-thanks for using an actual piston along with your illustrations.

[@joshbrown5901]

Hey Jason, love your videos have almost watched them all, helped me so much giving me a visual example on some tricky stuff so thanks for that. Now, could you possibly do a video on stalling hydraulics in heavy diesel machinery, I have read a bit on it but would love to see you do a video on it to help me understand, thanks again!

[@Atlas_FPV]

Could you do a video on hard break-in of an engine vs soft break in please?

[@willbergger812]

I would enjoy a video regarding valve seals.

[@AlexGtheDon]

Although I already knew what piston rings do; I wanted to watch this video and it is as accurate and even better than I could have described their purpose! 😊

[@3900Class]

my cousin and I are rebuilding a 1990 Mazda B2200 pickup. He thinks piston 3 is leaking oil into the combustion chamber, he can't be wrong because it looks nasty. I'm glad for videos like this and others that will be helpful as we continue with the rebuild.

[@akarimsiddiqui7572]

Do a video on Subaru's new platform explained and how it matters to future owners

[@Ndog888]

I AGREE

[@cringesohigh]

Wow! Technical automotive videos without an obnoxious introduction nor any irrelevant details such as what you had for breakfast or your most recent sikkk modz. Thank you sir, this is great! Subbed!

[@EngineeringExplained]

+jsamhall that's my style, glad you enjoy it, thanks for subscribing!

[@Frankinho45]

Excellent, concise presentation, thank you! Loved the whiteboard in particular.

[@goodshepherd536]

I think your videos are awesome there are informative and thoroughly explained by yourself, but sometimes you go through quite quick in videos and i get a little lost & confused as im no engineer like yourself, but i am learning slow but surely..;) Thanks again for sharing your knowledge of engineering and mechanics, and please keep the vids coming. Peace.

[@6Twisted]

Could you could do a video on hard vs soft break-ins? Manufactures tell you to soft break-in engines, but since learning about glazing and ring seating I don't know who to trust any more. I feel like manufactures just tell you to soft break-in to cover themselves, even if it's worse for performance. But I wouldn't risk an engine on it without an experts opinion. Thanks.

[@socas_nic]

Break ins have to be soft. You want your engine to be used in all kinds of RPMs in different gear ratios. Also do not stay on to certain RPM for no longer than 20-30 seconds. Do not red line your engine and do not let it idle for more than 30 seconds. So generally use different gear ratios at different speeds while not going above the recommended RPM and while not cruising for extended periods of time.

[@bernardlandymore7372]

Soft break in is the way to go if you have built the motor your self. The first 50 miles are the most important for future bore and ring life. That said I don't know about a factory build as I think they run them before they sell to the public and do not build to the tight tolerance that an independent engine builder should do.

[@seemssafe2995]

soft break in if you dont want your rings to seat

[@6Twisted]

@@seemssafe2995 Bruh, you're replying to a 6 year old comment.

[@seemssafe2995]

@@6Twisted ill do it again

[@AeroElectro]

That kinda ended abruptly. I was hoping for more details.

[@GreatGrandmasterWang]

AeroElectro that’s what she said

[@benjamingrimes3304]

@@GreatGrandmasterWang LOL!! 🤣🤣

[@prithvirajdj]

@@GreatGrandmasterWang 🤣🤣🤣😂

[@nickj4618]

Great Video! Nice, simplified explanation! Keep up these great videos!

[@stijnpeeters8430]

You are like my personal teacher. Keep up the good work!

[@laddaevolta]

How about thicker & lighter oils on new & old car engines. EO provides lubrication and sealant between piston ring and cylinder wall. Since older engines have bigger wear and tear, does using thinner EO affect compression and combustion. vise versa. Thanks

[@icekk007]

+Tango965 Yes, engine oil provides sealing between the piston ring and the cylinder wall. If the wear on the piston ring is excessive, no oil will help sealing it. If the wear is small, a thicker oil may help. The property of engine oil that matters is High Temperature High Shear (HTHS). You can find HTHS in an oil's product datasheet. An oil with high HTHS will form a better seal between the piston ring and the cylinder wall.

[@rollipollirock]

icekk007 if you have VVT heavier oil will not be good for your solenoids

[@rathjens]

Thank you! Your videos are awesome! What is the life expectancy for piston rings? How many miles/ how many years? Thanks again! Timo

[@DonutHole123]

Some last longer than others but with regular oil changes/general maintenance you should go at least 200k miles without oil consumption. My dads Mitsubishi Outlander has 305k and I don't think it consumes any oil, maybe a very little amount.

[@buzztrucker]

I would just like to have you teach me everything engineering. I really learn a lot from you.

[@MultiAna96]

Great!! Simple, detailed and very quick. Keep it up!!!

[@octurbojoe]

Wouldn't the power stroke in the cylinders be more susceptible to blowby squeezing past the rings rather than during the exhaust stroke, when the spent combustion gases already has exited the cylinders? Blowby happens when combustion pressures seep past the rings and make its way through the crankcase and out the vents, taking oil vapors with it into the intake, correct?

[@roadrunnerblink]

+OCTurboJoe I know what you're getting at but the blowby doesn't "squeeze past the cylinders" in one go. Look again at the diagrams in the video. It happens in two stages: 1) The exhaust stroke forces the rings DOWN letting gases into the top part of the gap. 2) The compression stroke now forces the rings UP which releases those gases out of the bottom of the gap. It is a two-stage process. It would take an incredible amount of power to blast those gases past the rings in one go. Maybe if the rings were very worn though.... Hope that helps.

[@octurbojoe]

+Boysya Exactly. It's more pronounced with force induction. A newly built engine with a fresh set of rings can still have a good amount of blowby. Pressure will always find the past to least resistance, especially through rings on the power stroke. The exhaust stroke is more like negative pressure where gases exit the chamber vs positive pressure pushing past the rings, into the crankcase, and out the vents. This video probably explains blowby at idle whereas I am explaining excessive blowby under load.

[@jacobfraser7967]

+roadrunnerblink he didnt describe it well, in fact most blowby is caused by bad ring to cyl seal, not by a tiny amount of space behind the ring

[@ammarhussainkazmi954]

Hi, Can you make a video on how to remove these blow by gases from your engines' sump I am talking about the ventilation of crank case. Thanks

[@nissanrb30]

this vid answered a few questions I've been thinking of. subscribed!

[@michaelbarnhill2685]

Great video as always. Picking up where you stopped the video at....id love to see a video about worn piston rings vs carboned up ring grooves leading to rings no longer able to seal correctly. Basically, a comparison as to which is the actual culprit for blow-by. Much like how warped rotors is a generic term for uneven rotors, when the rotors are not actually warped.

[@jonathanwance2654]

sir, can u make a video on Hard break-in. I really like how you explain things with engineering point of view, appreciate it so much...thanks

[@Str4vv]

Could you please make a video about breaking a car in? Mythbusting or the usual. The topic is so controverse, but also so important. Cheers!

[@sapien213]

U saved my day .... has a GTI with high oil consumption. ...and wasn't getting what's the real issue for vehicle . Almost 2 weeks of restless days. The piston rings are worn out and oil gets to combustion area and burns off... In high speed oil just becomes so thick and in 20km around 2 liter if oil gets burned .... But in low RPM .... there's no oil burning .... actually your video made me get the actual problem for the vehicle .... Anyway it's expensive to rip apart the engine and reassemble. ....going to do it anyway ...... Thanks a ton ...mate

[@DrummerBoii1411]

I was going to ask about Engine knock but then found your video from 2014.. Nice one lad, you have us nicely covered..

[@Gameplayery]

no fast and furious remarks? interresting

[@WojciechP915]

I believe piston rings in an engine form whats called a "labyrinth seal"

[@icekk007]

+Bill T Labyrinth seal is not used in piston ring. I think it is generally made of elastomer (rubber) material, so it can withstand the heat and pressure experienced in a piston. They are generally used in shaft seal in rotating machines.

[@ShaunHensley]

Bill T Labbys are on rotating assemblies as was mentioned, but they definitely don’t have to be soft like rubber.

[@mummyjohn]

Yes it is a variation of the labyrinth passageway, you don't line up the ring gaps all in a row for this reason

[@batulaut]

I just learn this from your channel. Great one!

[@louieanderson2847]

Thank you Jason. Good explanation as always.

[@TheWolvesCurse]

explain PCV valves please

[@Hank_Dog]

+TheWolvesCurse essentially, you have a valve on your crankcase that lets air/fuel out of your crankcase back into the intake manifold.

[@peterjensen6844]

When the vacuum pressure of the intake manifold/throttle body is in the correct range, the PCV valve opens and uses that vacuum to pull blowby gasses out of the crank case and pull it in to the intake and reburn it. Its an emission control system. If that valve is stuck open, you could suck up engine oil and cause all kinds of issues with the intake or throttle body.

[@mohamedli3354]

what metal are these rings made of? I always thought they're rubber.

[@VinaySharma-zt3gk]

Same

[@stradplayer90]

Not since the early 1900s has that been true. They are made out of a very hard, springy, and brittle steel.

[@VinaySharma-zt3gk]

+Jean-Paul Veillon Oh!

[@danalex6129]

cast iron

[@midniteoyl8913]

+Mohamed Li Usually cast iron for the Top Ring, cast iron or steel for the Second Ring, and steel or stainless steal for the Oil Control rings

[@IAcityntv]

Very informative video thank you.

[@DIYLifeSkills]

Always great demonstration and explanation. Great job!!!

[@internetpolice1166]

In other words...if you own an STi, buy an Air Oil Separator.

[@fightfanian]

you should go wayyy deeper into this subject. You could make a 30 min video if you went deep.

[@Viralityoflife]

+fightfanian how deep? Really deep?

[@fightfanian]

+Mike Halpert balls deep

[@Viralityoflife]

+fightfanian like hodgetwins sugar walls deep?

[@Snowcrest289]

+fightfanian A Basic overview gets the job done in :05 minutes. Well Done!

[@Boz1211111]

+fightfanian I was actually expecting that...

[@guiltygearcore]

Great explanation. Thanks for the great vid. Subscribed!

[@RoadandRacetv]

Excellent video as always.

[@detmer87]

Blowby = Volkswagen TSI engines

[@yourfather5324]

Yep

[@einseinseinseins]

Why are cylinder rings so much more reliable and durable than the Apex seals in a wankel engine?

[@jamtea573]

simply that the heat is more intense and builds up on one side of the block more than the other, so there are more cooling issues to overcome. Plus the oil, if not regularly topped up with the correct type will mean that there is more wear on the seals. Not to mention that the wall exhausts in the standard 13b design mean that they are regularly passing over the port which can cause some wear when it touches the other side (overcome in the renesis MSP design). The oil used however, even in this design doesn't burn 100% cleanly, so the residues that build up will cause seal wear and degradation over time. 2T Premixed fuel and SOHN oil reservoirs do help in reducing these types of wear, which would be nice to see this channel cover.

[@einseinseinseins]

***** ***** thanks! That makes sense;)

[@StrongFreeLovin]

Wow, I was expecting it to be longer, but it was actually 3:50! So good job explaining that time went super fast.

[@APM7]

thank you for sharing technical knowledge...

[@Jakevrana]

dude! 30 seconds into this video and I knew this was going to be informative, good job

[@seanroose6074]

Really good demonstrations in all your videos. Thanks

[@riccardolongoni8195]

wheo, 4k vid. nice job! really apriciated! keep it up!

[@shubhashshukla9321]

thank you very much. your video is very helpful in understanding the concept of blow by. keep makinh videos like this. again thank you

[@KOXXkomp]

Absolutely love these videos

[@VelocityLabs]

Excellent vid, thanks!

[@morpheus232001]

Great explanation as usual. Thanks.

[@exhausted-tears]

Nice explanation and very good graphics/picture quality, Thanks a ton man 👍

[@robertjackson7590]

Might do a vid on the different configurations of rings, cyl walls, Nikasil, cast iron and the advantages and disadvantages. Great video as it is.

[@dannymoreno15]

love this guys videos!

[@paviaaPS3]

WOW you are awesome Engineering explained. I discussed this topic with someone from the comment section like 2 days ago. And some said this topic was to small. yet you made the video I wanted. thank you so much. Have a nice day :)

[@alirafi5729]

Hey Jason, thanks for the awesome explanation as always! I was wondering why does the piston ring grooves allow a vertical play for the piston rings. I think that if there weren't any vertical play, the exhaust gas would not get in to the grooves and make its way down to the crankcase. One explanation that comes to my mind is may be it allows the first piston ring to have less stress on it by allowing the play. Can you please elaborate on this? Thanks!

[@WhiteWingSTI]

Awesome video! 👍🏼

[@Stratos.Mixalis]

Thank you so much! That was really educational! :D :D

[@RED97761]

We thank you for all the efforts you put to explain to us every time

[@kaihartmann924]

Fantastic explanation. Thanks for the great diagrams and use of real components for demonstration.

[@billsmeets1122]

great video, very nicely explained! subscribed

[@joeseptien2182]

Extremely helpful, thank you man.. so my motors junk unless I replace those rings... good to know.

[@abdikarinhirsi7450]

Your a good teacher I thought I was actually doing it by my self

[@Cyrus_Shokan]

Another excellent video!

[@rajatverma5391]

I would be really thankful to you sir if you explain about the practical working of manual transmission of bikes and cars

[@Sportsmaster222]

Good video man, thanks!

[@robertdionne6073]

Wow great explanation. Easy to understand.

[@danielgarnando8254]

Thanks, this channel really helped me a lot to learn for my Job in Shell.

[@williambranham6249]

Just now learning about something I have used for 55 years. So what happens to the gas that passes into the crankcase and is pressure inside the crankcase a problem. Thanks for your presentation. Extremely well done.

[@MrSapper21]

Great video! Thanks!

[@bobdeengineer7396]

Great video, thanks for the explanation. Those look like the newer type of rings that you can install without any tools. They look so flexible which helps reduce drag on the cylinder wall and increase mpg (change oil regularly to prevent sticking). It would be nice to have technology to produce an artificial layer of diamond surface in the bores and a coating on the rings to inhibit wear.

[@cbgreely]

Great explanation. Thanks!

[@seanl9222]

I was super hoping you would have a video up for the new Formula 1 Engines (Mainly the Hybrid System) for the season opener this week. Great explanation of piston rings though!

[@bkglall798]

Hey great video, thanks for the explanation! I was wondering why it seems like modern cars can go for over 200k miles without any major engine work, but a car from the 60s will need a new engine every 100k miles. And when and engine is "tired" does that mean it has low compression because of worn piston rings? thanks!

[@steveanderson81]

Helpful and easy to understand vid. Thx.

[@prapsi1542]

Thank you so much mate.... this clears my doubt about blow by

[@miguelsworld63]

awesome video. very informative

[@ricardoealvarez6]

I have a question regarding the gaps on the piston rings (2:30) , specifically for a small engine. When installing the piston, does it matter if the gaps within the rings get set alligned or do the gaps need to be set opposite to each other?

[@johnbehneman1546]

GREAT EDUCATION!!!! THANKS FOR SHARING!!!

[@domnicfernandes5723]

good explanation ...great job

[@TheRevo33]

could you do a video on engine breakins/running in. and what you believe is best. hard or soft breakin ;)

[@ABSProducts]

That was a Excellent explanation

[@johnhiram1207]

Great quick explanation. Easy to see why you should do regular oil changes.

[@anisshaikh3313]

Perfect and precisely explained.. thnx

[@jamesparr444]

Show your videos to my students as they are well present and easy to understand.

[@CharlesNam]

Hi Jason. Is it true that a certain amount of blowby is desired to keep the engine lubricated and last longer?

[@sorrymycreativity952]

GOOD WORK CONTINUE

[@fanfare466]

Nice and informative.... God bless you

[@mmdirtyworkz]

Very nicely done

[@gotenz90640]

good video like always

[@aliasmari]

Thank you very much for this video, I have question , I have an old 2 stroke aircraft engine with single piston that needs overhaul but. Unfortunately no parts available no new piston or chambers , so how can I fix this problem and restore compression

[@yzfr6ws6]

Does this work the same weather boosted engine I have an 03 cobra and I have just recently rebuilt the motor and it seems like I have an excessive blow by I have filters that replaced The PVC on each valve cover and I just seems like there’s an excessive amount of exhaust coming through