you did talk about the dynamic compression, does it increase the actual compression or reduces it?? because the air that goes into the combustion chamber have to go through the intake manifold, and the ecu monitors this vacuum pressure inside the manifold.... via few small ducts.
Well.. definitely reduces static compression, that one I'm positive.
The actual volume of air is theoretically dependent on how well the engine flows (the ports, the manifold, exhaust, etc.. something like, if exhaust easy to get out, then intake will be better.) But until I get around to the IAT and manifold pressure measurements, and how they can be used to estimate airflow.. this one still my THEORY only..
so does the manifold help to increase the air pressure and obviously the flow? and how does that affect the dynamic compression
It doesn't affect dynamic compression. The reason it's called dynamic compression is because it changes as valve closing timing changes during compression stroke.
The manifold in theory doesn't really change pressure. At full throttle opening for NA engines, it will read atmospheric pressure, which is about 14.xpsi at sea level, less when at higher than sea level (there's the ram air effect, but doesn't seem to be a big of an effect for street car speeds). For some gauges they will put this as zero vacuum. Boosted, will be different, as your manifold pressure will see more than atmospheric pressure.
What the intake manifold does is increase the volume capacity. I think this is for part throttle purposes, but it's a guess on my part.
Part throttle??.. Hmmm.. this one, I don't know yet.. I'm still on the stock intake manifold, so I'm logging all the stuff I can for the stock stuff, so when I swap, I have a baseline to compare to.
latest invention that i saw, put it that manifold don't need to have butterfly flap anymore, it uses individual flap just before exiting manifold towards the valve, does that improve anything?? it's like using individual throttle for every combustion chamber right???
I haven't seen this new invention, but it does sound like a slide carb though. (O_o)
then only we come to the cams part.....if i'm not wrong, most aftermarket cam are designed to be much wilder than stock (if the same why change??), obviously it will have sharper teardrop design, to increase the valve lift for more opening and longer opening duration....
Sharper teardrop design? Maybe it does seem that way to you, but for me, it looks nothing like the original teardrop design of stock cams. they are usually fatter, so don't look much like teardrop anymore. They are shaped like that so that they will spend more time at peak lift.
The teardrop shape is something that is a compromise to ensure the valvetrain works for a long long while, IMO.
Perhaps they don't make it too wild to avoid valve hitting piston phenomenon but it will still be more than stock.... how much, it depends on the manufacturer research.... so the other thing that we can adjust would be ignition advance or retard and cam angle adjustment.
Yup, agree with this.
obviously high rpm power need high comp, or else it won't sustain the rpm and won't be able to generate enough power
Yes, that is the conclusion so far, but why?
For me, sustaining the RPM is the work of the valvesprings so that valvefloat doesn't happen to the extreme..
The generating enough power part is understood, but exactly 'how' is the question.
Studying cams, it seems like the big durations actually makes high rpm compression a lot less than the static. But I understand the big duration needed part, because at high rpms, the valves would close too fast for proper filling of the engine cyclinders.
So the idea seems to be like yours, that high compression makes power.. The question is how, which I'm still researching now.
on the second one, the low cam on vtec engine manages all this, but all the talk about this only on vtec cam, how about the low cam? don't anybody wants to study that too?
Actually there was a discussion a while back on this. in a "1.8L with 200whp" thread.
Seems like for high compression engines, big duration primary/secondary lobes (not the VTEC) are needed to enable the engine to run higher ignition timing without knock at low/mid rpms.
