Ever so often, a person new to the whole car thing comes in and wants to know all about their vteck, or vtech, or whatever it is they mispell vtec as...


Point being... i'm sure some of you have come across this, but I figured I'd link it, so Dave, or whomever can stick it where it belongs where it'll reduce the number of recycled questions people who don't think to use the search button produce...

http://videos.streetfire.net/video/3...E74118BB4A.htm

 

I LOVE IT!!!!!!
I knew how to spell Vtecks....or vtek...or VTEC sorry(lol) and I knew what it stood for and what it did. BUT UNTIL now i couldnt picture it. DUDE NICE LINK. VTEC is truely nice QUESTION HERE IF I MAY? Buy getting bigger cams you increase the length that the valve is open correct, which allows more air in for a bigger bang. SO does this increase the compression then, making bigger cams bad for turbo. lets say on a GSR?

 

I can add a link to the Integra FAQ, but the question in my mind is about the stability of the URL. h:
It's a slick animation, but if the link dies in two weeks or so, what's the point? :run:

The other problem is getting people to read the FAQ in the first place. h:

 

Umm... let's back up a step.

Cam lobe profiles are defined by two separate factors - LIFT and ENDURANCE.

LIFT is measured in varying ways, but the basic principle is that a taller lobe will open the valve further, allowing more air (or exhaust) to flow into or out of the engine in a fixed amount of time.

ENDURANCE is determined by the ramps on either side of the lobe's wear surface. A more gradual slope to each face increases the amount of time the valve spends opening and closing. This also increases flow by providing more time for air (or exhaust) to flow into or out of the engine over the course of a given 4-cycle combustion cycle.

Now that we've got those terms estabilshed, consider the difference in engine dynamics between a naturally aspirated buld and a turbocharged build.

With an N/A motor, the exhaust charge is shoved out by the upstroke of the piston and drawn through the header by virtue of tuned pipe diameters within the exhaust header and so on. On the intake side, fresh air waits at near atmospheric pressure, to be drawn in as the piston begins its intake stroke.

N/A cams feature high endurance and high-lift profiles to provide additional power by exploiting the benefit of valve overlap. The cam profiles intentionally increase the period of time when the exhaust valve is open at the end of the exhaust stroke and the beginning of the next intake stroke. By using refraction tuning within the exhaust header, a scavenging effect at high rpm helps draw more fresh air into the cylinder. The end result is more oxygen to be utilized in the combustion cycle, producing more power.

With a turbo motor, the dynamics are entirely different at high-rpm. Within the exhaust manifold, there is a significant amount of pressure due to all the exhaust gas waiting to drive the exhaust impeller on the turbo. Likewise, there's plenty of fresh air waiting to flood into the combustion chamber when the intake valve opens.

Given these circumstances, turbo cams take an entirely different approach than N/A cams. Valve overlap is eliminated and valve lift is increased to better expel the exhaust charge and receive the incoming pressurized intake charge.

So, it's isn't a matter of bigger versus smaller cams when turbocharging a motor. The issue is to match the cam profile to the method of tuning.

Class dismissed. :run:

 

Note to all:
Anyone who says TheOtherDave doesn't know his shit will immediatley be hit in the head with a goddamn tack hammer..

Good lookin' out, big guy.
I don't know how long the video would be there, I can see what I can do about obtaining the video, and maybe someone will host it?
I dunno, not a huge deal, but it's nice to be able to visualize that shit a little better.

 

:chuckles: I'm not one to promote violence... so I hope we never get to that point.

Let me see if I can cajole a friend of mine into hosting the vid.
And I absolutely agree with you. To someone who is just learning the basics of engine operation, the visual aid is immensely helpful.

 

Dave is like my internet father for integras.

 

haha... when i first started learning... i had a GSR head sitting in my room...so i could just look at the open head and see the cams/lobes/rockers... i totally understood hehe

 

dave is the man

 

dave is one of ur friends able to post this on their site... i know a few people who would like the video on their myspace or something