Camshafts (Part 4) - Valve overlap

[@hiswordheals9710]

Very logical and simply explained thank you. I noticed TONS (most of them) of factory grind cams actually have a negative overlap, when plugging their profiles into cam calculators, couldn't wrap my head around them doing that

[@TalkingAboutThings]

They don't actually have negative overlap. That's an artifact of using 0.050" duration to calculate overlap instead of advertised, or 0.006", overlap. One must account for the full duration of overlap from when the intake valve just starts to lift off the seat (0.006" is a pretty reasonable guess for this) to when the exhaust valve actually arrives at the seat. If even 1 mil of clearance exists, air can, and does flow past the valve, affecting conditions in the cylinder.

[@ApriliaRacer14]

Thoroughly enjoyed this series and the well done narration and visual aids.

[@kylekoplien2924]

This guy could make a rocket ship easily understood : ) Very good explanation and cleared some confusion up perfectly, thanks

[@shrop]

Excellent explanation of hard start on a performance motor. Very nice.

[@JoelKamalando]

This helped me a lot with learning about camshaft. I want to get a 370z as a project caravans I need to learn all I can

[@nezerac]

These videos are AWESOME! You should playlist and monetize these and post them to sites that help explain cars.

[@kristibutterflykirk1]

I thought the same thing, as it takes several degrees for combustion to begin and complete. On high performance race engines, spark timing is advanced to begin combustion early so that you get the biggest "bang" and the right time and degree of the power stroke. And when you are running high RPMs, most of the fuel has not burned when the exhaust opens, so a lot of the fuel is wasted and you lose potential energy. You cant get every bit of energy out of every bit of fuel burnt.

[@sammwautsa1381]

Clear explanation nice one

[@priestleyselvaraj9203]

Awesome man. I love the way you explain stuff.

[@hks071]

Man, this is so educative

[@kristibutterflykirk1]

probably depends if the car came stock with a turbo. I was thinking the same thing too, a turbo would only make that "inertia" stuff he was talking about even better and it would make the turbo work better, making all the breath off the engine more and more efficient

[@MasJets]

Great explanation, thank you

[@kristibutterflykirk1]

I know two things about this guy. 1: He know a lot about camshafts and timing, and 2: He pops his fingers.

[@TreyMohr]

great videos!

[@tmak4699]

great videos.

[@Dr_Xyzt]

Have you ever cammed an engine so the intake valve closing is in the factory location and the intake opening is such that it overlaps slightly? I'm dealing with an engine that has a 40 abdc intake closing event and a 16 atdc intake opening. I'd like to go to a 7BTDC intake valve opening, and keep the factory intake closing. The modified cosine function I'm using to describe my cam profile generally loses 60 degrees of duration before it hits prime valve lift levels. 15.27% more useful duration. Going from a 204 cam to a 227 cam, I should go from a 430hp engine to 490 + whatever the inertia benefit is. If I get 10% more torque all the time by purging the chamber, this should be a really great running engine. If I can find a set of heads that flows poorly at low lift, and better at mid to high lift, then that should lessen the effect of late valve events, right?

[@paul39man39yo]

all the heads flow poorly at low lift :))) by the way hard to make statements on paper about what amount of hp will you gain with more duration, it depends... for sure you have a shity cam but be sure to check up the piston to valve interference cuz with 16 deg atdc opening maybe is a pretty high compression engine and that was made on purpose.. What engine are you talking about?

[@Supra2winTurbo98]

Around when does the spark plug fire? Wouldn't it be more efficient if the exhaust valve opens around the 21 degree mark at the bottom instead of at the 50 degree mark as it does now? It would seem like you would loose a tad bit of power from the combusted air going through the exhaust port before reaching bottom dead center (if that's the correct phrase). I understand it would take a few degrees for the valve to open up but it wouldn't take 50 degrees would it?

[@paul39man39yo]

the only problem is that the intake gas rushing is the effect of the exhaust gas going out at high velocity, not vice-versa, and in the video, this little detail doesn't show of ..

[@glueit1]

But in naturally aspirated engine air which enter is not have sufficient enough so how that unburnt gases will forced out?

[@diablovt108vt109]

Why do many diagrams on this topic display the valve lag and lead near BDC as valve overlap as well when it isn't? Ie. between ur top red and green line they are shaded as valve overlap, correctly, but then also between the bottom red and green line also. I have found this on google diagrams and in a book I have on engines, makes no sense but there must be a reason.

[@TMM6900]

does 252 still apply for akinson cycle?

[@bubot17]

is more overlap the culprit for the lopey idle?

[@coyotan951]

Hi, does this apply on Aircraft Piston Engines as well ?

[@mobbdeep615]

would the low rpm problems be solved if there was more fuel in the air?

[@diambo4life]

No because you still need compression, Remember...for fuel to bang it needs compression in a specific ratio with air.

[@jasongrey5712]

what is this for a small piston

[@weesenz1992]

Mute the volume and go to 0:35

[@kristibutterflykirk1]

If you are running a turbo, that unburned fuel helps run the turbo, but it creates a lot of heat in the turbo, too.

[@balajichandrasekaran6312]

IF there is an overlap wouldn't it cause the exhaust gases to pass through intake valve ? if no then what is the pressure inside>>>> intake valve,exhaust gas pressure

[@mackoncars7579]

No because there is too much pressure behind the intake valve face.

[@paul39man39yo]

will! thats a reason for the unburned hydrocarbons the MOT reads with their gas testers

[@mitsuomitakayanagi9256]

what do you call the period during the valve timing where both the intake and exhaust valves are closed?

[@94SexyStang]

Underlap I think.

[@paul39man39yo]

you dont call it :))

[@johnnyjrotten59]

cracks fingers @ 4:30 Euuuughh

[@ghiribizzi]

overlap

[@paul39man39yo]

what a good kid.. you have learned a new word :))

[@dwelgaine4319]

hi i'm korean i think this very useful so i wanna see this but you speak so quickly that i can't understand what you saying i really see your viedeo plaese speak slowly next movie thanks niceday

[@dapper_gent]

If he talk any more slowly he'll be talking backwards.

[@MarquisRex]

Seungyeon Yeo Can you listen any quicker?

[@Shannon_Robbie]

Great info but could do without referring to the valves and piston as "she". It sounds misogynistic!

[@ronsmith7739]

This is a complete waste of time. This is a simple calculation of intake valve, exhaust valve and lobe separation.

[@Zquiker]

if you have an exhaust run turbocharger, does the exhaust valve close later, for more "umph" to the turbocharger?