My new (used) S is the first Honda I have owned since my 81 Prelude and my last toy car, a 91 MR2 turbo was where I received most of my automotive education. I know many Honda cars are VTEC engines that vary valve timing and lift, but don't know what it "looks" like.

Having never seen one of these engines opened up but read articles about the car switching to "power max" or "the hot cam" or a "different cam lobe" but don't know how to visualize what is happening. Anyone want to venture an explanation and perhaps a photo or diagram?

 

I think there is a little quick time video on Honda's website that shows this. But as a quick over view.....When the car reaches 6300 (i think, 00-03), there is an actuator that opens to let oil pressure push pins in place that activate a more agressive lobe of the cam. This is the kick in the pants that you feel when you hit 6300. You can also see the the difference on a dyno plot. BTW if I'm not mistaken the actuator sits at the right front corner of the engine just at the bottom of the valve cover.

 

PS.... The only thing I was able to get from a search was something about a third cam and some expired links to explanation pages. Does that mean that VTEC engines are triple overhead cam? And how does it physically switch between the "street" cam and the high performance cam?

Anyone....anyone....Bueller? Bueller?

 

Thanks DT,

That helps a little. I have read about VTEC not kicking in because of a stuck MAP sensor, but has anyone had problems with a stuck actuator? Where is it located? Is it part of the aforementioned MAP sensor?

 

try this site.

http://auto.howstuffworks.com/framed.htm?p...vtec/index.html

http://auto.howstuffworks.com/question229.htm

 

Try this link I found.

It is an independent website, but looks to have reliable info (if a little old).

Looks like there is just an additional lobe on the same cam.....not a seperate cam entirely.

Vtec Explained

Hope that helps you.
Hockey

 

It's easy imagine in your valvetrain are 4 little mice and 4 big rats. WHen you step on the gas, rice falls in front of the mice and they start running.

When you get to Vtec a little door changes and the rice starts falling in front on the 4 big rats and they really start running.

fltsfshr

 

The cams have two different profiles, the VTEC lobe is only engaged when the oil pressure switch opens up and the oil pushes pins in the rocker arms which lock in the rocker arm that the VTEC lobe is hitting, therefore engaging VTEC. When not in VTEC the lobe simply slaps the free floating rocker, which is why VTEC motors are slightly loud and sound like valves are knocking slightly on idle. The VTEC lobe has a higher lift and longer duration lobe profile.

 

[QUOTE]Originally posted by fltsfshr
It's easy imagine in your valvetrain are 4 little mice and 4 big rats.

 

that works for me...bring your ls1 on. i got big rats.

fltsfshr