Tech Topic: 3 cam profiles on the B18C5?

blktyprgrl · Post by **blktyprgrl** » November 1st, 2005, 3:50 pm

I was reading in an engine builder's mag that was discussing the 5 forms of vtec. In the article, when talking about lift, there was a note that the "R" engine(and one of the preludes) had 3 different cam lobe profiles versus 2. It has a low, med, and high(vtec). I was wondering if anyone knew the purpose of 3 different profiles. Does it cause a certain swirl effect aiding in combustion, are the valves staggered? How does it work?

Dave_B · Post by **Dave_B** » November 1st, 2005, 3:57 pm

IIRC it's for multiple purposes. First off no need to be on the high cam as it's refered when just "putting" around town. This saves on fuel economy. Also some cams are very loby causing a crappy idle. I'm sure there are a lot more reasons as well I'm just not thinking straight at the moment.

Bbasso · Post by **Bbasso** » November 1st, 2005, 3:59 pm

that is what I was thinking but a conversation we had, She said it was different... I think we need to see the page that you are talking about Girl, opps Pornstar, Opps Ms.

<-- deep trouble now

blktyprgrl · Post by **blktyprgrl** » November 1st, 2005, 4:19 pm

well let me pull the june issue of "whatever its called" outta my ass and I'll post it...

seriously, I can't remember it verbatim, and I can't remember the name of the mag, I was reading it waiting on a friends lsvtec to be dynoed. I wish I could though..
EDIT: the article was written by a professor who teaches auto tech, the tests/info was conducted/gathered at the Honda facility in Ohio.

Vteckidd · Post by **Vteckidd** » November 1st, 2005, 5:31 pm

It was a magazine that had to do with the different stages of vtec, and how it has evolved over the years.

Donf would know what it was, it was his magazine.

The way i understood the article was that the GSR and B16 have pretty identical secondary Lobes. The ITR does not, they have staggered secondary lobes, but the magazine gave no explanation for it.

Since we are talking about stock OEM camshafts, the "idle well" theory gets thrown out, cause all stock OEM cams idle perfect. Hell, even my Skunk2 Pro3 camshafts idle like stock.

Honda designed the ITR camshaft with a different ramp rate and lift characteristic that was unique when compared to the GSR or B16. she just wants to know if anyone knows why.

I think it has to do with the design of the intake manifold and the compression. perhaps it was to change dynamic compression numbers becuase its the highest compression B series motor honda made. Maybe it was for better combustion and tumble and swirl in the chamber. maybe it was the 62mm throttle body and better flowing head and they were able to get more power out of a staggered lobe design.

interesting none the less