What’s the compression on a running engine?

[@teardowndan5364]

Readings are getting messed up by the tubes adding to compression/combustion chamber volume and having non-negligible flow resistance. There needs to be check valves at the engine so any gas that gets in the tubes stays there and takes that much compressed gas volume out of the combustion chamber equation.

[@nebula0024]

Came here to say this, you beat me to it! Especially when the engine is firing up, which is causing all kinds of chaos!

[@MadScientist267]

That and fluid dynamics. The cross section of the tubes are tiny relative to their length. When the gases try to move in it at the high speeds that the pistons are changing the pressures at, the drag takes over, resulting in a "net zero". So there's a delicate balance here, getting the tubes big enough that the gases can move at operating speeds, while not reducing the compression ratio to inoperable.

[@teardowndan5364]

@@MadScientist267 Reed valves at the engine "adapters" would take tubes out of the equation: any gasses that pass by stay there no matter how long and thin the gauge tubes are. Pressure builds up to equilibrium with ignition pressure and then the tubes are no longer a factor. In that sort of setup, you do want drag from the tube walls to dampen any standing waves and surge pressure.

[@MadScientist267]

@@teardowndan5364 I didn't say it couldn't be done, just that it is nowhere near as simple as it would seem. They started out with the "intuitive" version and got what I would call "expected results". As it unfolded, I was not surprised as one problem's solution would create another problem. The complexity is the reason.

[@TheBeeMan1994]

Compression testers already have a “check valve” though so the gauge holds the pressure reading after testing

[@jordankidd230]

the guy that does these voiceovers deserves a medal, hes the reason i can watch one of the most interesting auto channels

[@xxs1lentk1ller30]

Sounds like shit

[@dansw0rkshop]

In steam, there is a device called a snubber in line with the gauges. This prevents the pulsations from making the needle flick around. It's not a check valve, it's just basically an orifice that results in the reading being averaged over a time constant.

[@FuckGoogle502]

Which to use would depend on whether they want to measure average pressure or peak pressure.

[@johnjelinek-g7b]

Also, the added volume inside the tubes and fittings decreased the compression ratio a LOT . But it was still fun watching . :)

[@Timsturbs]

like RC filter in electronics, narrow channel that creates resistance for the flow and a reservoir

[@kylevarble2325]

I love how you guys aren't afraid to try anything I admire and applaud you thank you!

[@demil3618]

Most people are afraid of trying all those things because it may cost them f it goes wrong. They turned it into a business investment and get paid back by YT. Also think of the Rubel value right now and YT paying in western currency, so it makes a lot of sense…

[@GroovesAndLands]

This is why they use piezo transducers for in-cylinder pressure measurement for engine testing.

[@richardprice5978]

also showing how hard it can be, 🤔hope that doesn't come out to bite me as my 440 mopar is being modified for EFI and ( and Nissan* type VCR connecting-rod's so independently tuned everything cylinder by cylinder and by cycle etc ) liquid push-rod's ( valve's have slave-cylinder's so top is tied to the masters/cam-card-grind/or/ecu-limited and bottom-side is tided to air/N2-bladder-main/or/opposite-cycling for desmotronic activity ) aka computer need's to know where the intake's-valve's are as well as the exhaust's-valve vs in-cylinder-PSI vs crankshaft so nothing crashes and the tune can be 👌as spark is lit at peak-PSI/best-spot and or table for in-cylinder temperature etc rather than the 2002~ ways of guessing by using o2's and camshaft-sensing+crank or 1950's-fixed carb+dizzy-etc

[@GroovesAndLands]

@@richardprice5978 Wow, hope that works out for you.

[@pbocking44]

for hi budget motorsport eg: F1 - they produce a spark plug with strain gauge built in - so can map the pressure over time as spark occurs. They're not cheap. I like your alternative.

[@BruceWillison]

What a pity there is not an award for the great work you guys do but, we will just have to keep giving you guys a big thumps up .

[@vincentrobinette1507]

Try it with a DIESEL! Try to find a model that uses glow plugs, so the glow plug ports can be used, without any modification to the cylinder head. If the ball and seat can built right into an adapter shaped exactly like a glow plug, it will be possible to eliminate any change in chamber volume. If the chamber volume becomes too high, a diesel engine won't even start! You will definitely want to use the 250 kilogram gauges, especially, if you load a turbocharged diesel engine.

[@tcmtech7515]

They would need a system that works way higher than that for Diesel. Every time it fires on a power stroke under load the cylinder pressure can be in the hundreds of atmospheres.

[@pbocking44]

do they make a diesel Lada (it has to be be a Lada)

[@oliverscorsim]

So i did this for an r&d project of mine on my drag bike and by far commercial pressure transdusers were best for the job with as little volume between the chamber and sensor but i used stainless brake line. Tthe more primitive way i found was oil filled gauges and what ever you see at idle your gonna see 5-30x under load around peak tq. Add a restrictor between the tube andvalve i use a small needle valve.

[@hydrocarbon82]

The reason for idle vs WOT is simply because compressing vacuum (idle) leads to less peak pressure.

[@oliverscorsim]

@@hydrocarbon82 yes but youl actually get way higher pressure Going up a hill for instance than you would just going wot on flat ground

[@mondude9754]

I am curious what were your readings?

[@DerekDuVelleDrives]

Which company did you use for your pressure transducers? Kistler make specific Piezoelectric engine cylinder pressure transducers, I've not seen many others in that niche market though!

[@richardprice5978]

id like to see it becoming more common ( and mor affordable $$$$, on mine the bulky/packaging-in-bay-use and or hard to use, but then again im not great at computer's/programming but good for mechanical needs, definitely interesting choice of mine to continue/converting to EFI and a complicated setting at that 🤞🤔😅 mechanically nd wire should be fine getting a tuneup and ecu is a different experience 💭🤔🍀 ) in aftermarket ECU's as tune is directly controlled by need's of in-cylinders not 2002~era MAP/o2-ect externalities as that's more of a guess than anything really and or project's like mine it's even more important as my valve's/liquid-push-rod's ( cam-on-demand, by grinding max then ecu-limiting downward's to needs etc ) and connecting-rod's/VCR ~8:1 to 15~:1 aren't fixed in place like tom-hoover had in mind in the 1960's/ 440's and 426-platform's

[@carguy55]

That's the type of videos we all want to se, keep going guys 💪💪

[@sketchy__chris]

Ignition timing will directly effect cylinder pressure 😊

[@Pulverrostmannen]

Well, Truth is that you also have Vacuum in the cylinder pretty much half of the time as it suck in the fuel mixture, so when the valves in the gauges fails to seal the pressure you built up is being sucked back into the cylinder again, and all you can read is pretty much the average pressure. you would need some really heavy valves to get this working properly :)

[@markchapman2585]

Great video, guys. Did you guys do a video about spark plugs opening and closing the gap as far as possible. Can you try to make a diesel run backwards. That would be cool. I know older diesels you can do that, but I never tried it or really seen it go all out. I have seen a few go backward for a few seconds or less on KZbin. Keep up the great work guy's 👍

[@Skumevil]

Most engines are capable of running backwards. I used to have an old Ford 300 inline 6 the would run backwords. I wouldn't do it to any engine you care about. The problem is the oil pump will also rotate backwards and you wont get any lubrication to the cam and main bearings.

[@whyjnot420]

@@Skumevil One of the big reasons for a starting motor is to start spinning the engine in the proper direction. This feature goes back to steam expansion engines even. (You should see the stuff used on ships back in the day when they had those utterly massive expansion engines... think Titanic or whatnot... with engines that big they needed the starting drive just so the engine didn't blow up from the injection of steam in the high pressure cylinder, the amount of friction on the pistons when sitting still was just that high, but direction was just as important)

[@anonymousinc6330]

Any engine can be re-engineered to run backwards, in fact the old 2-stroke Detroits were capable of this. But you have to use a different oil pump designed to run the opposite direction or it will seize up from lack of oil.

[@timw6596]

Many twin engine boats have counter rotating engines to the boat runs straight. I used to watch car races and this one car would turn down into the corners and not lift th inside corner of the car, found out the car had a boat engine that turned the force down the corner instead of out of the corner, the other drivers were not happy when they figured it out !

[@ranger178]

it is just going really high for such a brief time that the pressure can't build up in the tube before it is at suction on intake stroke the mechanical valves can't move fast enough to open and close with spring in them.

[@trm4life]

Definitely need to revisit this with different gauges!

[@rastaralph7154]

The fuel and exhaust gases are probably going up the pipes to the gauges and disrupting the mix in the cylinder so that's why it would hardly start up 💚💛❤️

[@bladi-senpai9398]

Actually is the lack of compression most likely

[@FuckGoogle502]

The cylinder can't compress the air as much because the excess air is traveling up the tubes on the compression stroke, then sucking it back out of the tube on the intake stroke. The gauges added a compression leak the way they have them installed with no check valves. The internal volume of those tubes is enormous compared to the combustion chamber that the engine is expecting the air to be pushed into. Edit: Like trying to start a chainsaw with the decompression bulb leaking.

[@ProdigalPorcupine]

@@bladi-senpai9398 I agree, that's the most likely reason.

[@GrantJohnston-dr9rt]

Now they are putting their heads together! Greetings from Montreal!

[@Lucast3]

Combustion peak pressure for regular gasoline engines does not typically cross 50 bar at maximum load and ignition time. For pressure reading, you need a very (very) tiny tubing between cylinder and measurement gauge (something like refrigeration capillar tubes), in order to minimize compression spring effect. But anyway, analog gauges does not provide all amplitude, the best you will got is the pressure average.

[@soulthatcreates]

I think the cylinder pressure would be much higher with the engine under a load... You gotta take it for a drive, up a steep hill! Maybe you guys should invest in a dynamometer... That would open up a lot of options for experimentation.

[@MadScientist267]

There's a whole lot going on that isn't apparent here. Gauge range, fluid dynamics, frequency and heat causing catastrophic wear and failure of the check valves designed into the gauges, the effects of trying to counter fluid drag reducing the effective compression ratio. The list goes on... Agreed that the pressures will be much lower when the engine is only idling... but until the other problems are solved, adding load will only make things that much more silly. One of the first actual "popping off" illustrated how chaotic it is inside the cylinder even just at "idle" - I believe it was cylinder 3, the needle was dancing all over the place to the point you can't even calculate the average anymore. Edit: 8:13

[@cmsracing]

The cylinder pressure will go way up under load, for example while driving or accelerating.

[@Fk8td]

The valves aren’t meant to read at that kind of speed and the pressure is dissipated before it can read.

[@felixlafuente9714]

What an impressive idea!!!! You will need some check (one way) valves because pressure is high but time of it is very short

[@michaellegg9381]

Use high temperature pressure sensors and digital gauges.. thats likely the only reliable way to obtain a clean reading.. also the combustion chamber size has changed due to the extra volume From the copper pipe and the pressure gauges.. im not sure how to get around that unless you make each pipe and gauge exactly the same length and volume or the entire engine compression ratio will be different in each boar 🤔 you might have to shave the head face until you reach the original combustion chamber volume in each cylinder.. thats going to take some thought and effort but would be great to be able to monitor running compression and start compression for track or drag racing and even for diagnosis of road cars.. i can see this being very useful if you can figure out how to have a normal combination volume..

[@GrugBug-f7j]

Solid! Top KEK! Peace be with you.

[@gldgti]

Low readings would be expected at idle and free revving the engine. The cylinder pressure is low because 1) the engine intake is in vacuum with the throttle relatively closed and 2) cylinder pressure is low because there is very little torque required just to turn the engine over. If you want to see bigger cylinder pressures ,you have to drive the car and load the engine up

[@KenFullman]

The main reason the pressure is low is because of the extra volume the tubes are adding to the cylinders at TDC. This is reducing the compression ratio (causing the starting difficulties). Then as soon as the engine starts running, the heat anneals the springs in the pressure relief valves on the guages. Rendering them useless. There are so many issues going on here. It really needs check valves where the tubes enter the cylinders. And those check valves need to be heat proof.

[@Hobby_Electric]

You need very fast one way valves close to the combustion chamber, also a long thin tipe will reduce the pressure. A Diesel Ship engine can reach over 200 Bar Combusion Pressure

[@kentworch]

Very interesting experiment, definitely think those gauges are failing before the true combination pressure is being reached though. Would be really cool to see that, but that's probably quite tricky. Anyway, awesome video as usual.👍👍

[@jonathanjones7319]

I figured the compression test stuff wouldn't cut it. Ty great vid

[@mutantryeff]

Well thought out experiment

[@rafaellastracom6411]

Cylinder pressure is actually cylinder load. You have had the engine just idling which is very, very low load. You need to load it up and the best way to do that is using a very high gear, so you are at a low rpm, and give it 100% throttle. This will make the gas pressure have to work hard to push the piston and will give you an idea as to what peak pressures would be. Also, the gauges should have one way check valves so the gas does not escape. You will only be able to capture the highest recorded pressure but that is exactly what we want to see anyway.

[@onestopfabshop3224]

You don't need a check valve at all. All you need is a tiny buffer orface. They have them on the old mechanical turbo gauges to keep manifold pressure from fluttering. Take that out, and it's unreadable. Just an FYI

[@FijiLaw]

Its measuring combustion getting over compressed and air in long tubes interfering with compression of fuel to air ratio causing long cranking

[@busyguy7479]

fascinating watching you guys work on these experiments, you never know until trying something thanks for the interesting videos.

[@kevin_6217]

Combustion pressures in aircraft engines were measured by special spark plugs that had pressure transducers built in. The duration of the pressure spike is very short. Dial gages are not going to be able to respond quickly enough to show an accurate reading.

[@vitor900000]

You need a good one way valve to see the something close to the peak pressure on those gauges.

[@jedisith25]

That's the type of videos we all want to se, keep going guys

[@Comatoastedd]

Love your videos, please keep up the work!

[@bishop8848]

god damn it, "What's the compression of a running engine?" now that's a question i would have never thought to ask, that i absolutely need to know the answer too

[@siddharthshekhawat5502]

Reading are not stable bcoz there is compression and decompression so just put a one way valve in between to get a stable reading

[@johnb4639]

To measure running cylinder pressure you need an electronic pressure sensor - then no need for non-return valve. Cylinder pressures to be then be displayed sequentially on an oscilloscope. Would be interesting to then examine the rise and fall shape of each pressure pulse. No need for all that plumbing if each sampling orifice was built into modified spark plugs.

[@DonaldRichards-mr3lz]

The compression stroke is so fast the pressure gages con not react that fast on the intake stroke there will be some negative pressure a small amount of vacuum on the intake stroke .

[@billneptune9097]

I know you're in Russia, but a mid 90s ford ranger with a four cylinder has 2 plugs per cylinder. Would have made this really easy.

[@bobirving6052]

Check valve springs did not get damaged by heat. They got damaged from hammering shock waves.

[@rouuuk]

🛑im surprised no one noticed or mentioned this, you should keep the hand break on and put the gear shift in 2nd and try and to move the car with manometer installed , then you will see the pressure needle go up.

[@gormanspacemarine]

you need plenum chambers for each gauge to disperse the pressure from pulsing.

[@WolfmanDude]

Maybe you could try to connect a fast electronic pressure sensor to one cylinder so you can measure the pressure waveform during the cycle? I have seen that on reseach projects, but I could not find anyone doing it in a video. Could even have big potential for tuning!

[@msmith5030]

Interesting. Love your videos. How about trying to get hold of the Wankel rotary engine. Think what you could do with that😀

[@EndroEndro]

you could see how much difference in pressure spark timing would give you or different fuels

[@IvyMike.]

The longer pipe increases the combustion chamber size, therefore reducing the compression ratio, you need a very small jet inline to smooth out the pulses, less than 0.10mm (for air), close the source to solve this, so it slowly builds pressure up in the gauges, (this has been used to calm hydraulics down for years, with no moving parts).. You would get away with this setup on a turbocharged engine, on boost only though.

[@volvo09]

The combustion event is very short, so there is a momentary high pressure spike, and then the piston comes up and down another 2 crank rotations at atmospheric pressure (or vacuum if not at WOT) before there is another combustion event. A smaller orifice won't fix it. Only a fast acting check valve (coupled with time to build up that pressure in the pipe), or an electric pressure transducer and an oscilloscope.

[@IvyMike.]

@@volvo09 Obviously, you have never worked in this field, or used carburettor balancers on multi carburettor engines, as they use a flow restrictor valves to calm the gauges down. Pumps of any sort don't produce pressure, they produce flow, like an ICE. Pressure is a restriction of flow, like the piston being forced down. So if you reduce the passage for a fluid (air is a fluid) to flow, it will produce pressure. Bear in mind you are contradicting someone that works with flow and pressure every day on hydraulic systems., and used flow restrictors to calm things down on piston type pumps. and modern diesel injection systems.

[@IvyMike.]

And furthermore a check valve will probably fail after a short time and is only one way.

[@volvo09]

@@IvyMike. True, I have used a carb balancer before, but that isn't measuring peak vacuum, the restrictor is averaging out the suction pulses so the liquid doesn't jump around. If these guys want to find peak pressure, a simple flow restrictor isn't going to do it as the pulses are waaay more erratic than a carb balancer. A carb is always under vacuum at idle and the suction pulses are what you want removed. The cylinder spends much more time at or under atmospheric pressure than it does under extreme pressure. The flow restrictor would be working in the opposite way to keep the big pulses they want to see out of the readings. I do agree on the check valve though, I don't know how one would survive unless it was a basic ball and seat... They already broke the check valves on their compression gauges.

[@IvyMike.]

@@volvo09 Exactly, you average out the pulses to give you a readable gauge result and it works the same weather it is negative or positive pressure, if you are getting erratic gauge readings, reduce the orifice size or close the valve a bit more. It works the same way when we convert AC to DC, we pass it through inductors to smooth out the current and capacitor to smooth out the voltage, i.e. restriction of flow.

[@Lee-pz1sd]

Without the problem of check valves making combustion chamber larger messing up ratios you could of jacked the car up put it in 1st gear and applied the brake while under acceleration and then you would of seen a larger reading especially under stalling conditions

[@anonymousinc6330]

I think fuel is getting blown into the gauges on the compression stroke. This is robbing fuel from the startup process, making it harder to start. Further, once it's running, the gauge loads up with this fuel, and since you can't compress a liquid, the gauge reads nothing. This might work better on a diesel due to the fuel being supplied after the compression stroke, though I'm not sure the gauges would survive the heat of diesel exhaust gases for very long. Someone else mentioned a snubber, which I think is a step in the right direction. @teardowndan is on to something about check valves, but I'm not sure how you would make it allow the air while rejecting the liquid.

[@mrmatt2525able]

I would like to see you guys use a ball bearing check valve with a large spring, like for hydraulic system style, and use small diameter copper line(like for your oil pressure gauge) coiled up between the check valve and the gauge to smooth out pressure spiked and go for a Drive and out the engine under load and see if it changes, and change ignition timing to see if that has an effect of combustion pressure

[@ddiablolll]

We did this in school on a 1990 Honda Accord it made something like 50 psi or 3.3bar at 4000rpm

[@tootsitroll9785]

It’s two different things to measure when running and not running. The fact there’s sucking with the push is putting you at neutral or messed with the results. That’s the basics execution will be another story I’m guessing :)

[@persiangulf2282]

Hi uncle ! Plz made diy steering rack (Rotary valve)

[@Weirdvideomaker]

Basically just making the combustion Chamber larger which explains the hard start

[@PoXFreak]

Compression is negated by intake vacuum. At the rate of speed the position travels for intake, compression and exhaust, there's no way to really get an idea of actual compression numbers, especially during combustion.

[@mann_idonotreadreplies]

Cool, story, bra,

[@MarkLoves2Fly]

Now add extra spark plugs where you had the valves. See if more spark will make the engine better.

[@DJjamespodcast]

I love you show keep up this awesome channel

[@twocvbloke]

Well, the gauges didn't do the whole movie trope of pinning the needles and blowing up, so, guess there's just not enough pressure there... :P

[@RANGOArts]

The tubes are adding up to volume of the combustion chamber.

[@patricklittle5757]

I enjoy watching y'all's videos I'm in usa

[@patrickbrady447]

You mighe be able to fit a pressure sensor and electric gauge. off an earth moving machine that could cope with the pressure and tempature. Like a hydraulic pressure sensor and gauge. I live the crazy things you guys get up to.

[@blazin_bouch710]

When the engine is cranking but there's no explosion from fuel firing the cylinders and making crazy amounts of vacum in the cylinders eating the relief valves because there not rated for any vacum

[@goranzalud4781]

Can you weld camshaft to increse valve moving for more power😀

[@GrandePunto8V]

Use pressure "sensors", transducers!

[@justinowen1402]

I'd say since it's blowing out the valves it needs maybe a metal ball instead of rubber and a stiffer spring.

[@wizkid1]

Should have used a head that has dual spark. Used one of the spark holes

[@erikcourtney1834]

Come on guys. How much compression did you lose with all the tubes? That and you need check valves. Put check valves at the head. Will still be lower than stock pressures but will still be high.

[@IanRandall-b9w]

Could it be, combustion Engine has a flame front affect on combustion that forces the piston down at such a fast interval. And then a vacuum on down stroke for intake. Could that constant change in compression to vacuum equal out almost at the compression guages causing a low reading?

[@75L48]

Not surprisingly you will get low reading at idle, throttle is closed. YOu need to chceck full load pressure. In this tiny engine it will not be much but readable. Modern high power diesels run to 200Bar of peak cylinder pressure.

[@linuxguy1199]

Mechanical gauges are a bit too slow, id go to using electrical pressure sensors logged via an oscilloscope. Connecting them with as short of tube as possible

[@pbocking44]

Can you make a lada with 4 wheel steering please - so it will turn in a very small circle.

[@billgates3699]

Lunokhod 😂 that is the best part of this whole channel.

[@jdjd0711]

Put some load on the engine. Like put it in gear and hold the brake or slip the clutch

[@JohnSmith-jl3fm]

Lower the valve seats and stems see if that makes more pressure. Or hemi the head and make the head sit higher with a longer throw on the rods. People have had ridiculous hp out of small engines.

[@timothybayliss6680]

You could make direct injection with the same welded in bung

[@jeremypike9153]

Liquid filled gauges would aid quite a bit in seeing what is going on.

[@GHOOGLEMALE]

Pressure transducers required

[@busyguy7479]

Its a shame that the rest of this troubled world cannot take the time to get involved in activities other than fighting wars. these people could take lessons from you guys may GOD bless you all.

[@ANATURALDREWSASTER]

I’d love to see this test but with predetonation induced

[@Frosty_Icepck]

That head should be ready for a direct injection Lada project

[@peterjohnson9438]

You need electronic load sensors and a computer that can average out the readings. There's still a question of keeping the load cells cool enough to operate, but that's where this test needs to go.

[@reinekewf7987]

digital manometers are more suitable but more expensive but they can keep up

[@sueplummer-x4k]

I often wondered what it was nice one

[@Obsequious1]

I'm wondering if the pressure would change when the car is driving. An engine under a load with more air and fuel should yield more pressure. " In Theory "

[@josephmonnens]

I'm just wondering would the heat from a running engine eventually make the gages melt or stop working considering that the combustion gas is super hot

[@AlienLivesMatter]

Interesting experiment

[@AnneStevenson-w3t]

Smaller jet on those tubes will give you a smoother reading

[@zach_94]

is the pressure higher when the engine’s under load?

[@GAMINGOBRIEN69]

I don't even know where you would buy those higher pressure ones

[@guuuu666]

Remember that the combustion is forcing down the pistons and as the rotating assembly is design to help keep the reciprocal movements of the pistons in unison. The chemical force of the combustion is converted to mechanical force and only the residual force will show a reading as pressure.

[@nico73simons]

doe dat nog eens tijdens rijden🤔

[@khalilamd1]

Please I need a video adding 200cc of kitchen detergent to the engine oil and going out to demand it

[@anibalbabilonia1867]

👌😂👉Next video use the same engine for the next crazy experiment! 🧪 this guy’s content is great!🤣👍

[@BattleMachines]

Hi all. Greetings from Slovakia

[@dav1dbone]

A simpler approach would have been to modify or make spark plugs with pass through tube

[@shrikantmd9428]

what happened when engine intake valve and exhaust valve same size..🤔🤔🤔 Plz make video on this Topic.. 🤔🤔🤔🤔🤔🤔🤔🤔🤔🤔

[@87fubar]

could do a direct injection or fun stuff with nos

[@Ammour_Nadir_Automotive]

what about a pressure transducer