How a 4 Stroke Engine's Piston Motion and Valve Events Interact

For a better understanding of the how’s and why’s behind tweaking individual valve events Here’s a quick explanation of the four events in order of importance:
1. Intake Valve Closing (IVC)
This event has the most control over the powerband. We trade low- end torque for high-end horsepower when we close the intake valve later after BDC.
2. Intake Valve Opening (IVO)
This is the first component in overlap and the most important to idle quality. The idle gets rougher when we open the valve earlier BTDC, but we net more airflow on the intake stroke.
3. Exhaust Valve Closing (EVC)
This is the second component in overlap and is a compromise between reversion at low rpm and part throttle and the positive effects of scavenging higher in the power band and WOT.
4. Exhaust Valve Opening (EVO)
This is the least critical of the four events due to high residual cylinder pressure blasting out of the cylinder even before the piston hits BDC. It helps rid the cylinder of burnt gasses, but it’s a compromise. Opening too early before BDC decreases pressure on the piston that could be used to turn the crank, but reduces pumping losses. Pumping losses are caused by pressure working against the piston when it’s on the upstroke after BDC.
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[@craftshark3221]

just for a moment of humility , a series of clever 19th century mechanics thought of and designed the internal combustion concepts that we sometimes struggle to comprehend and do maintenance on ; )

[@SummitRacing]

Thanks for watching!

[@williedavis3966]

Most of this stuff sounds like french. I have a lot of studying to do. Thanks

[@adithyankp7977]

Use full for auto mobile engineering students. 👍

[@mrmysterious6006]

Hi Summit. Liked your video. I wish it was more in depth and you specified ranges for our valve events. Anyway, do you think an IVC of 51 or 52 degrees is good for my engine? I have an LS2 408 with cnc ls3 heads and 12:8.1 compression. If I run a slightly later IVC this should help with torque down low with that much compression? I have also been having timing issues with current cam a 236/244 114 LSA +2. I have been readling around that using a 51 or 52 IVC plus more duration should solve my timing issue as it will bleed some compression. Please help! Cheers

[@stephenbennett4524]

4YYZUU77ÀÀ⁷À⁷

[@Mattvardaman]

I wish more people would seek to understand these principles instead of saying what cam should I run in my car/truck/boat?. If you aren’t sure, call a camshaft rep! Be honest about your goals or you might end up like so many guys with a cam that’s too big and no power below 3,000 rpm. Edit: Summit’s Pro Ls truck cams are great, I run one in my daily driver with the 174002 springs.

[@SummitRacing]

Thanks for watching, Matt!

[@abdelbaki612]

usefull information about the car

[@SummitRacing]

Thanks for watching!

[@blakenorman4822]

Just watched a video where someone used a vacuum/pressure gauge to find TDC, He used a compression gauge hose took out the Schrader valve connected the hose to the vacuum gauge hose with a fuel line and hooked into the spark plug hole So when it was on the compression stroke it was reading on the pressure side of gauge and as the power stroke started and exhaust valve opens it starts reading vacuum, he just turned the crank with socket back and forth till it read zero between vacuum and pressure to see TDC Watching this video brings it to light a little better, so when its TDC on power stroke i wonder what the gauge says? Just bought gauges gonna try it on my dads tr6 see if TDC is lined correctly with his harmonic balancer marks Thanks for video

[@SummitRacing]

Thank you for watching, Blake! Good luck.

[@marsel108]

Can lack of back pressure cause damage to the valves?

[@akassasin5768]

No. Valves are not damages during start up or if the engine is turned over by hand. In both instances there is no back pressure.

[@longtattat3865]

For example, the pitston diameter is 50mm and how to install the intake valve and the commune valve accordingly?

[@frankmiranda1352]

What would make the valves switch operations like blowing out into the carb and out the air filter

[@bretbradbury5559]

It depends on how violently it's occurring. What I mean is if it's like a sneeze, combustion is occurring when the intake valve is still open. If it's doing this independently of any spark, then install a degree wheel and verify the valves are doing what they should be, when they should be, comparing it to your camshaft card. If you don't have one, you can get (or should be able to get) the information from the camshaft, on the front or usually the back end of it. In other words, if it's doing this independently of any spark, your cam timing is off. If it's using a chain, the gear marks are not properly aligned.

[@AutoBodyEverything]

kzbin.info/www/bejne/e4jOo4ugrLqSrqs Can you help me? While racing my engine it all the sudden went limp on one cylinder (as it seemed).. despite the bent electrode from #3 cylinder, it was nearly tapped shut but it sounds like no compression in one cylinder. Running a shade tree test, it seems like the valve overlaps are entering into other chambers. Watch the vid, I think it’s a chain jump but I’m not too familiar with THIS kind of overlap.

[@SummitRacing]

A timing chain jump would affect all cylinders, not just one. Do a compression check of all cylinders. If all have good compression and within 5-8% of each other, there is no engine damage. The spark plug electrode could have been caused by an engine over-rev. At high RPM parts do tend to grow!

[@professorright]

Enough with revs. One would do.

[@setoman1]

I don't know about you, but I would prefer not to have ANY interaction between valve and piston. I'm happy with my engine and don't need a new one.