It has been stated many times within this forum that the third lobe on a vtec cam shaft induces swirl of the incoming air/fuel mixture. I understand the reasoning for this however I'm not sure on how it is achieved.

Can someone shed some light on the subject?

Thanks in advance.

 

You get more swirl from the low speed lobes because they open something like 10 degrees apart. The 3rd lobe is the high speed lobe. This is the first mention I've heard of the 3rd lobe imparting swirl, unless what you're talking about isn't "standard" VTEC.

 

3rd lobe is VTEC. Valves open at the same time, no swirl.

You can see for yourself pretty easily. Get a round glass. Put two funnels over the top of it. One funnel with a bigger spout than the other to simulate the valve that is open more. Put some food dye into two glasses of water. Pour water evenly into both funnels and watch how the food dye mixes in the glass being filled. Not the best way, but it works.

 

I remember reading something about the VTEC in the 01-05? Civic Si and somehow the two intake valves can be opened one first, then both, then both a little more for "VTEC"? It might not be that car( i can't find the article right now), but apparently there is a Honda engine that works in that manner.

 

Read up on VTEC-E.

 

Primary lobes induce swirl.

VTEC lobe induces tumble.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92TypeR &raquo;</TD></TR><TR><TD CLASS="quote">Primary lobes induce swirl.

</TD></TR></TABLE>

How does the Primary induce swirl?

Also, does the smallest lobe (First lobe) play any role in this?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chillinit &raquo;</TD></TR><TR><TD CLASS="quote">

How does the Primary induce swirl?

Also, does the smallest lobe (First lobe) play any role in this?
</TD></TR></TABLE>

King V nailed it, each primary has a different valve opening and closing, this degree of separation causes air to swirl in the direction of the first valve's opening.

 

look up the D15B as well. 2 stage vtec.

 

The D15 has a two stage valve system, I've read. Somthing like 12 valve mode and 16 valve mode.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by King V &raquo;</TD></TR><TR><TD CLASS="quote">The D15 has a two stage valve system, I've read. Somthing like 12 valve mode and 16 valve mode.</TD></TR></TABLE>

I believe the k20a3 in base RSXs and 02-05 Civic Si's works in a similar way.