sinister357

how do you guys feel about honda's description of it's vtec system. Variable Valve Timing and Lift Electronic Control. it's electronically controlled but is the timing really "variable". i thinks it's more of a two stage thingy would be a more accurately describtion of it. this has been bothering me for awhile. just had to get it out.

IggyBcool

sinister357

someone, just explain to me the "variableness" of it and it'll be all good. but till then, i'm going keep pushing till i get an answer.

DAguyLS

my take on the "variable" is that your cam profile "varies" depending on rpm's.

95_GSmokeR

http://www.team-integra.net/se...ID=45

read this and learn.

if you still need "proof", pay attention to the last line in the fourth box down.

Uncle Ben's

its just a camshaft with 2 different lobes for the valves. then vtec engages, the sloenoid pushes the camshaft over and the bigger, more duration lobes then control the lifters. its as simple as that.

sinister357

i've read all that and it still doesn't justify it's name "variable timing". i wonder though, can it actually be accomplished - you know, changing the timing of the cams, variably? i hear it so much and in other cars other then honda's, there's got to be some truth to it.

honda011

who cares, as long as it works and we have it.....

JMod

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sinister357 &raquo;</TD></TR><TR><TD CLASS="quote">i've read all that and it still doesn't justify it's name "variable timing". i wonder though, can it actually be accomplished - you know, changing the timing of the cams, variably? i hear it so much and in other cars other then honda's, there's got to be some truth to it.</TD></TR></TABLE>

Well they say variable because it changes, doesn't mean its constantly changing. And as to your changing the timing of the cams variably, like all the time, thats what the VTC is on the new K-Series engines, it eliminates the adjustable cam sprocket, and changes the cam timing & angles based on your rpm/throttle position.

sinister357

wow! that's impressive! i never knew that on the k series. what technology made that possible? i can't imagine it. i'll do my research and find out what i can but if any one can help me understand this - please do tell me more. i very interested. too bad i won't be dealing with a k series anytime soon but its good to know.

Sack Master

var·i·a·ble ( P ) Pronunciation Key (vâr--bl, vr-)
adj.

Likely to change or vary; subject to variation; changeable.
Inconstant; fickle.
Tending to deviate, as from a normal or recognized type; aberrant

A vtec lobe is more than just a higher lift more duration lobe than a primary lobe. When vtec engages the lobe seperation and centerline are then changed. Cam centerline is also cam(or valve) timing. If the cam centerline just changed, that means it varied away from it's original timing. Granted it's nothing like a K series motor. But that's exactly what it is. Variable valve timing and lift. And obviously it's electronically controlled.
I hope that answered yoru question. Now if you don't mind I'm going to go back to doing what I do best. Talk sh$t and add as information of no useful value as I possibly can.

bosnianhondafreak

i thought it was 3 lobes primary secondary then vtec

dvp

Do some research. People shouldn't have to feed it to you. Go do yourself a big favor and search on google for it.

sinister357

i just want to know as much as everyone else...hehe. im sure i'm not the only one learning here. but then again, isn't this what this forum is for? - to share Knowledge? if everybody knew everything, we wouldn't be on here to start with.

back to the topic...how exactly does a k series changes it'e timing while running? i still can't imagine what would require fo do such a thing. i know its something in the cam shaft and gear right but what???

Sukebei Oni

ok. its called variable valve timing right? and you know that when VTEC is engauged there is a second more aggressive cam lobe in the middle of the primary lobes. (the primary lobes being the ones that open and close the valves at low engine loads. also since there are 2 intake valves and 2 exhaust valves. there are 2 primary lobes per cylinder for the 2 intake valves on the intake cam.)
the secondary more aggressive lobe is in the middle of the primaries and when it is engauged, it will take over for both of the primary lobes and open and close both intake valve. thus changing the timing of those valves. i believe the valves then open sooner and longer allowing for more air to enter the cylinder and making more power.

this variable timing of the valves is not infinitly adjustable. its only a 2 step adjustment. like how some fans have only low and high settings. they are still adjustable, but no where near as adjustable as a climate control system.

sinister357

i understand the high lift long durations cam profiles but we're on the k series now and what i want to know is how the timing is changed while the motor is running - degrees in timing changes similiar to a manually adjustable cam gear. it does it's automatically on the fly, right? or so i've heard but how. does anyone have a picture of the cam gears on a k series motor? i would think whatever it is, it's on there.

Sukebei Oni

If its like i remember hear about the toyota version, the cam gears themselves are adjustable. the outer teeth of the gear that the timing belt rides on are not directly connected to the the cams. and the timing can be changed by sending oil to the gears. I think the are spring loaded but timing can be advance by oil pressure being sent into the gear rotating the inside in a way to advance the timing of the gear. the more pressure you send into the gear the more advanced the timing will be. hard to explain with out pictures. plus I havent studied it for a long time now

sinister357

now we're getting somewhere. that IS pretty cool. complicated but cool. i would imagine the gear assembly not being very simple either considering what it has to do...but i need pics! PLEASE! this is killing me.

Sukebei Oni

here, this might clear it up a bit.

http://asia.vtec.net/article/ivtec/

sinister357

that is exactly what i was looking for! wow! very interesting. it didn't just clear it up a bit - in explains in in detail. how did you ever find such a page in such short time? it's very informative indeed. thanks Sukebei Oni.

LSvtec03

is he trying to ask about 3 stage vtec?

sinister357

i don't know what a 3 stage is but no, i wasnt asking about that. i was asking about the variable timing on an i-vtec and others - hows its timing in degrees are able to be change and all that cool stuff. you should read the article. so bottom line is it 's hydralic pressure that changes it huh? now i wonder how accurate that can be.

yrethguad

I'm in a sig. That kicks ***.

Thanx 95_GSmokeR