Go Back   Honda-Tech > Honda and Acura Model-Specific Technical Forums > Honda Civic (2001 - 2005)
Sign in using an external account
Register Forgot Password?
Search


Reply
 
 
 
 
LinkBack Thread Tools Search this Thread
Old 07-14-2006, 04:17 PM   #1
Honda-Tech Member
 
Miracle's Avatar
 
Join Date: Mar 2006
Location: Clarksville, TN
Posts: 4,827
iTrader Rating: (0)
motiv8d KMiracle1984
Send a message via AIM to Miracle
Default This, is VTEC explained.

UPDATED 8-15-06

This is for the ones who do NOT know how VTEC works, and for the ones who DO know, please correct me if it can be proven that I have made a mistake on this anywhere. Seeing as this is my first Honda, I think I did ok on this, but please, correct me if I'm wrong.

This thread is designed to teach you the operation of Honda's, and possibly imports all together, greatest innovation.

Mods, if you could, please sticky this and leave it open for further discussion/questions. Now, on to the meat of this post.

Ever wonder how Honda SOHC VTEC (Variable Valve Timing and Lift Electronic Control) works?
Well, with a little research, here is the best I can explain it.

I am assuming you all know how a camshaft operates the vales on a car? A concentric lobe rotates on a central shaft, hitting the valve, opening it, allowing air to enter the combustion chamber. It turns out that there is significant relationship between the way the lobes are ground on the camshaft and the way the engine performs in different rpm (rotations per minute) ranges. The grind on a camshaft is often referred to as its 'profile'. The larger the profile, generally, the more power you can make.

VTEC was developed by Honda as a mechanical and electrical system to allow a Honda engine to essentially have two cam profiles, in one camshaft, for optimal engine performance through all RPM's.

Like its DOHC counterpart, SOHC VTEC, which is explained in this article, optimizes the flow of fuel/air mixture for high RPM operation while maintaining smooth and economical low RPM operation.

In a SOHC VTEC motor, the camshaft sits centered in the head, so both of the intake and exhaust valves are engaged on the same camshaft.
There are 3 camshaft lobes on a VTEC camshaft. The three cam lobes in the middle are the intake cam lobes. The two low RPM (the shorter of the 2 profiles) lobes actuate two valve rockers, which in turn pushes the intake valves open.

Click the image to open in full size.

The high RPM lobe actuates a follower, which is shaped like a valve rocker, but doesn't actuate any valves, under normal conditions. While there are different intake cam lobes for high and low RPM operation, the same two exhaust cam lobes are used for all RPMs. The lack of cam profile changing for exhaust valves is the primary difference between DOHC VTEC and SOHC VTEC engines.

Below is a picture of the rocker arm assembly in a VTEC motor. Notice the valve operating lobes on the out side, with the VTEC engagement rocker in the middle. When VTEC actuates, a rod connects the 3 together, "making" VTEC.

Click the image to open in full size.

To make VTEC happen, the ECU has to realize the following parameters from the sensors on the motor:
1 Your MAP (Manifold Absolute Pressure) sensor must read 0hg (aka 0 inches of vacuum). When it reads this it will send a 3volt signal to the ECU.
2. Your throttle has to be open 100% because your TPS sensor has to send a 4.5-volt signal to the ECU.
3. Your coolant temp has to be at running temp.
4. Vehicle speed has to be above 20mph.
5. You have to have 65-80 oil psi.
6. The engine must be running at a minimum of 4500 RPM.

During low RPM operations, the two outer (smaller profile) intake cam lobes directly actuates the two valve rockers, Just like in a normal engine. These low RPM intake lobes are optimized for smooth operation and low fuel consumption. The high RPM intake lobe rides on and actuates the high profile follower, But since the follower isn't connected to anything, it doesn't cause anything to happen, yet.

Click the image to open in full size.

At the higher RPM ranges, at a point determined by the ECU, the 2 rockers for the valves, and the middle follower for the high profile LOCK together, allowing the 3 pieces to ride on the big profile on the camshaft, enabling the motor to ingest more air, and in turn, more fuel, for more power. since the middle camshaft lobe is higher, when VTEC engages, it lifts the 2 valve rockers off of the camshaft all together.

Click the image to open in full size.


Now, on to the performance aspect of VTEC.

On a stock motor, equipped with a factory fuel and ignition system, there is no need to change the VTEC point. Because with the introduction of more air, more fuel is needed to prevent the motor O2 levels to go lean, in turn burning a valve, or otherwise damaging the motor.

To optimize VTEC, it is wise to introduce into the equation a larger fuel pump, larger injectors, and a controller, to change the fuel and ignition parameters of the ECU. Apex Integration, along with other performance parts manufacturers, make control boxes suited to just that purpose. You can see a image of the APEXi VAFC (VTEC/Air Fuel Controller below.

Click the image to open in full size.

Essentially, what that does, is introduces user programmable fuel maps, and VTEC engagement points. A stock motor really doesn't benefit from one of these, as there is no way to introduce as much fuel at the nessecary RPM to combat detonation and the engine running lean.

Companies like GReddy, AEM, Hondata, and TurboXS produce user programmable interfaces, to allow for tuning of the ECU fuel maps to compensate for the lower VTEC engagement point.

Here are some videos to demonstrate in a 3d model how VTEC actually works.
Video 1
Video 2

A varible of VTEC I do not know much about is i-VTEC, utilized on 02+Si's, rsx's TSX, newer Accords and CRV's.

Here is a link to a VERY good write up on i-VTEC:
http://www.superhonda.com/foru...24797

i-VTEC introduced continuously variable camshaft phasing on the intake cam of DOHC VTEC engines. Valve lift and duration are still limited to distinct low and high rpm profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. Phase changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to maximum advance at full throttle and low rpms. The effect is further optimization of torque output, especially at low and midrange RPMs.

Below, you can see what the cylinder head on a K series i-VTEC looks like. Notice the timing CHAIN, instead of a belt. That is an integral part of the i-VTEC function.

Click the image to open in full size.

Click the image to open in full size.


I hope this helps, and if you have any questions, please IM me, or post it here.


Modified by Red_EM2 at 2:05 AM 8/15/2006


Modified by .Red.EM2 at 10:57 AM 10/20/2006
__________________
My 'Stang Build v. 2.6H
Miracle is offline   Reply With Quote
Old 07-14-2006, 04:54 PM   #2
 
gitrdone's Avatar
 
Join Date: May 2006
Location: em2turtle, ca, usa
Posts: 378
iTrader Rating: (0)
Default Re: This, is VTEC explained. (Red_EM2)

so the vtec controler aint worth it? what if i changed my fuel pump and injectors?
__________________
Quote, originally posted by jackinthetrunk
So I bought this helmet size Large. So that means it is not DOT certified right? [img]http://images.honda-tech.com/set1/smile/emthup.gif[/img]
gitrdone is offline   Reply With Quote
Old 07-14-2006, 04:58 PM   #3
Honda-Tech Member
 
Miracle's Avatar
 
Join Date: Mar 2006
Location: Clarksville, TN
Posts: 4,827
iTrader Rating: (0)
motiv8d KMiracle1984
Send a message via AIM to Miracle
Default Re: This, is VTEC explained. (catch_me_if_u_can)

The most benificial 'all motor' Change you can do to your car, is to change the fuel system to a returnable system, which really isnt worth it anyways on the D17, but if youre willing to go all out, and spend some futile money on the D17, then thats your perogative.

But if you wanted to, then maybe a walbro fuel pump, the swap to a returnable system, aftermarket fuel rail, bigger injectors, a better Intake Manifold, an adjustable FPR, Camshaft, valvetrain, cam gear and VAFC would yield some decent gains. But thats if you want to dump 2 maybe 3 grand into the motor. Which youre going to have to do anyways if you go boost'd. Or you could wait for a K to show up, and then youre really free to do anything.

Its really all up to you.
__________________
My 'Stang Build v. 2.6H
Miracle is offline   Reply With Quote
Old 07-14-2006, 05:06 PM   #4
 
gitrdone's Avatar
 
Join Date: May 2006
Location: em2turtle, ca, usa
Posts: 378
iTrader Rating: (0)
Default Re: This, is VTEC explained. (Red_EM2)

Click the image to open in full size. i see, Click the image to open in full size.
__________________
Quote, originally posted by jackinthetrunk
So I bought this helmet size Large. So that means it is not DOT certified right? [img]http://images.honda-tech.com/set1/smile/emthup.gif[/img]
gitrdone is offline   Reply With Quote
Old 07-14-2006, 09:28 PM   #5
Honda-Tech Member
 
Pnoymugen's Avatar
 
Join Date: May 2002
Location: Henderson, Nevada, U.S.
Posts: 331
iTrader Rating: (0)
Send a message via AIM to Pnoymugen
Default Re: This, is VTEC explained. (Red_EM2)

Good write-up on the sohc vtec. Good Job! Click the image to open in full size.
Pnoymugen is offline   Reply With Quote
Old 07-15-2006, 04:12 AM   #6
Grace Under Pressure
 
Newborn_'s Avatar
 
Join Date: May 2006
Location: The Fugitive Motel
Posts: 2,519
iTrader Rating: (0)
Default

Nice one, Red.
__________________
'90 DA6 XSi
'01 E39 540 V8
WTB - SSR Reverse Mesh Centre Caps - PM me!
Newborn_ is offline   Reply With Quote
Old 07-15-2006, 04:51 AM   #7
Honda-Tech Member
 
MidShipCivic's Avatar
 
Join Date: Aug 2004
Location: Altamonte Springs/Orlando, Florida, USA
Posts: 4,638
iTrader Rating: (0)
Send a message via AIM to MidShipCivic
Default Re: This, is VTEC explained. (catch_me_if_u_can)

Quote:
Originally Posted by catch_me_if_u_can
so the vtec controler aint worth it? what if i changed my fuel pump and injectors?
To need any of that you need to have your engine taking in more air than normal.

__________________
MSEngineering unconventional versatility.
MidShipCivic is offline   Reply With Quote
Old 07-15-2006, 11:39 AM   #8
 
Join Date: Jul 2006
Location: long beach, ca, usa
Posts: 8
iTrader Rating: (0)
Default Re: This, is VTEC explained. (Red_EM2)

can you explain to me how the vtec controlller works?
i have a ls-vtec all motor runnin a p28 jun chip....will that benefit my car to run better? Click the image to open in full size. Click the image to open in full size.
EgSiCknEsS is offline   Reply With Quote
Old 07-16-2006, 02:43 AM   #9
Honda-Tech Member
 
03EM2guy's Avatar
 
Join Date: May 2006
Location: Chapin, sc, US
Posts: 843
iTrader Rating: (0)
Send a message via AIM to 03EM2guy
Default Re: This, is VTEC explained. (EgSiCknEsS)

nicely done Click the image to open in full size.
__________________
03 EM2 cardiff blue-green pearl-sold / 91 CRX B16A turbo-sold
97 EJ6 gsr-t 297whp/220 ftlbs @ 10.5psi ..for a lil while, now allmotor 195/137
06 Yamaha r6 - almost my daily lol
03EM2guy is offline   Reply With Quote
Old 07-16-2006, 11:38 PM   #10
Honda-Tech Member
 
k24em2's Avatar
 
Join Date: Apr 2005
Location: Lincoln, Ne, USA
Posts: 1,895
iTrader Rating: (0)
Default Re: This, is VTEC explained. (03EM2guy)

Just FYI, the D17A2 VTEC system only uses two intake lobes. It basically runs 12 valve operation until the crossover point then goes to 16.
k24em2 is offline   Reply With Quote
Old 07-17-2006, 01:12 PM   #11
 
HondaRacing3's Avatar
 
Join Date: May 2006
Location: Miami, Florida, USA
Posts: 43
iTrader Rating: (0)
Send a message via AIM to HondaRacing3
Default Re: This, is VTEC explained. (k24em2)

I have a D17A1 and I might look into installing a Vtec head. I've read what people have to say on other topics, however my friend told me that if I did this I would need a full swap kit, new oil lines need to be drilled for the head, a new ECU, and my check engine light will always be on b/c it would be "chipped". I've noticed no one has adressed this issue yet. If I can find a used headswap for around 300 would you recomend this, I'd like to hear if anyone has done this to their car. This is my first car so I dont wanna screw it up guys lol Click the image to open in full size.


Modified by HondaRacing3 at 5:24 AM 7/18/2006
HondaRacing3 is offline   Reply With Quote
Old 07-17-2006, 06:21 PM   #12
Honda-Tech Member
 
k24em2's Avatar
 
Join Date: Apr 2005
Location: Lincoln, Ne, USA
Posts: 1,895
iTrader Rating: (0)
Default Re: This, is VTEC explained. (HondaRacing3)

It isn't worth the effort or the money.
k24em2 is offline   Reply With Quote
Old 07-19-2006, 11:18 AM   #13
Junior Member
 
prelude_vtec99's Avatar
 
Join Date: Jun 2006
Posts: 12
iTrader Rating: (0)
Default Re: This, is VTEC explained. (k24em2)

Where exactly is the VTEC crossover point on a D17A2? I'm hearing different things like 2 stage where 2000rpm all intake valves kick in and then at 4500 VTEC engages? It's too bad there's no distinct VTEC note with the D17...
prelude_vtec99 is offline   Reply With Quote
Old 07-19-2006, 11:44 AM   #14
 
HondaRacing3's Avatar
 
Join Date: May 2006
Location: Miami, Florida, USA
Posts: 43
iTrader Rating: (0)
Send a message via AIM to HondaRacing3
Default Re: This, is VTEC explained. (prelude_vtec99)

yes 4500 i believe
HondaRacing3 is offline   Reply With Quote
Old 07-19-2006, 01:38 PM   #15
Honda-Tech Member
 
k24em2's Avatar
 
Join Date: Apr 2005
Location: Lincoln, Ne, USA
Posts: 1,895
iTrader Rating: (0)
Default Re: This, is VTEC explained. (prelude_vtec99)

Quote:
Originally Posted by prelude_vtec99
Where exactly is the VTEC crossover point on a D17A2? I'm hearing different things like 2 stage where 2000rpm all intake valves kick in and then at 4500 VTEC engages? It's too bad there's no distinct VTEC note with the D17...
No there is only one crossover, where all the valves are engaged.
k24em2 is offline   Reply With Quote
Old 07-19-2006, 08:33 PM   #16
 
Doebmx1's Avatar
 
Join Date: Oct 2004
Location: wooster, ohio, usa
Posts: 157
iTrader Rating: (0)
Send a message via AIM to Doebmx1
Default Re: This, is VTEC explained. (Red_EM2)

very good write up, wish would have been able to read this when i was learning.. Click the image to open in full size.
__________________
96 Jetta GLS - [B]SOLD[/B]
92 Civic DX D16y8 BOOST! 14.0 at 103!-[B]SOLD[/B]
95 Integra GS-R MAD VTAK YO!!! [B]CURRENT[B]

myspace.com/doebmx1

Ohio [img]http://images.honda-tech.com/set1/smile/embeer.gif[/img]

/Oo ___[B]A[/B]___ oO
|=_|_______|_=|

Doebmx1 is offline   Reply With Quote
Old 07-21-2006, 07:43 AM   #17
Honda-Tech Member
 
MidShipCivic's Avatar
 
Join Date: Aug 2004
Location: Altamonte Springs/Orlando, Florida, USA
Posts: 4,638
iTrader Rating: (0)
Send a message via AIM to MidShipCivic
Default

There's always a different sound, and k24em2 is right.
__________________
MSEngineering unconventional versatility.
MidShipCivic is offline   Reply With Quote
Old 07-22-2006, 08:04 PM   #18
Honda-Tech Member
 
asdfsad's Avatar
 
Join Date: Mar 2006
Posts: 129
iTrader Rating: (0)
Default Re: (MidShipCivic)

I thought that i would add a little to this thread while asking a few things. I have found a few videos illustrating how Vtec works. These two videos basically reinforced what you have explained.

http://videos.streetfire.net/s...a.htm

http://videos.streetfire.net/s...a.htm

OK well here goes my newbie questions. This is my first vtec car/honda i have ever owned and I was trying to understand how Vtec works a little better. I have a h22a4 DOHC prelude and I was wondering one thing, how is the sound Vtec "makes" created?
__________________
http://www.albinoblacksheep.com/flash/posting.php

Posting and you!
asdfsad is offline   Reply With Quote
Old 07-22-2006, 08:12 PM   #19
Honda-Tech Member
 
Miracle's Avatar
 
Join Date: Mar 2006
Location: Clarksville, TN
Posts: 4,827
iTrader Rating: (0)
motiv8d KMiracle1984
Send a message via AIM to Miracle
Default Re: (asdfsad)

Quote:
Originally Posted by asdfsad
I was wondering one thing, how is the sound Vtec "makes" created?
The sound youre hearing is the engine uder a heavier load of air and fuel. Its when the locking rods engage in the rockers that VTEC begins, and allows more air in the motor, which is the noise you hear.

BTW, VERY good find on the videos. Im going to put those in the OP if you dont mind.
__________________
My 'Stang Build v. 2.6H
Miracle is offline   Reply With Quote
Old 07-22-2006, 08:55 PM   #20
Honda-Tech Member
 
asdfsad's Avatar
 
Join Date: Mar 2006
Posts: 129
iTrader Rating: (0)
Default Re: (Red_EM2)

Quote:
Originally Posted by Red_EM2

The sound youre hearing is the engine uder a heavier load of air and fuel. Its when the locking rods engage in the rockers that VTEC begins, and allows more air in the motor, which is the noise you hear.

BTW, VERY good find on the videos. Im going to put those in the OP if you dont mind.

haha thanks for the explanation Click the image to open in full size. Click the image to open in full size. Btw how many posts does one need to have before the messaging function works?

nvm works and yea put it in the OP so people can see how it works
__________________
http://www.albinoblacksheep.com/flash/posting.php

Posting and you!
asdfsad is offline   Reply With Quote
Old 07-23-2006, 11:00 PM   #21
 
xenoturkey's Avatar
 
Join Date: Jul 2006
Posts: 1
iTrader Rating: (0)
Default Re: This, is VTEC explained. (Red_EM2)

The only thing I would like to add to this sticky is that honda most certainly did not invent VVT (In essence the mother of vtec). GM had the first version of VVT in 1975. Otherwise, good technical explanation.

Just FYI.
xenoturkey is offline   Reply With Quote
Old 07-26-2006, 12:39 PM   #22
 
Rich EX's Avatar
 
Join Date: Aug 2005
Posts: 46
iTrader Rating: (0)
Default Re: This, is VTEC explained. (xenoturkey)

great info for a noob on how Vtec works, but we have Vtec-E (economy) engines and more helpful to know how much Vtec-E sucks before we get our hopes up and then disapointed when a stage 3 cam gives us about 12 hp. 7thgencivic.com has a stickie on how all SOHC Vtec engines work. from 0 to 4500 one intake valve rides the primary and 2nd valve on secondary, after 4500 they both switch to primary, exaust stays the same.
__________________
2001 Civic EX, 2 door, five speed.
AEM cold air intake
DC sports 4-1 header
Megan Racing test pipe
stock exaust, cut out resenator, put turbo mufler on.
[url="http://1bad6t.com/extra/civic_high.wmv"]http://1bad6t.com/extra/civic_high.wmv[/url]
Rich EX is offline   Reply With Quote
Old 07-28-2006, 01:24 PM   #23
 
ghost_ryder35's Avatar
 
Join Date: Nov 2003
Location: Madison, WI, USA
Posts: 618
iTrader Rating: (0)
Send a message via AIM to ghost_ryder35
Default Re: This, is VTEC explained. (Red_EM2)

Very nice writeup Click the image to open in full size.
__________________
Nissan Sucks!
525i
Corolla All-Trac
ghost_ryder35 is offline   Reply With Quote
Old 07-28-2006, 09:33 PM   #24
 
xquiset's Avatar
 
Join Date: Jul 2005
Location: Los Angeles, CA, USA
Posts: 26
iTrader Rating: (0)
Send a message via AIM to xquiset
Default

nice post
__________________
if you drive a honda, you own
if you dont drive a honda, buy one.
xquiset is offline   Reply With Quote
Old 07-28-2006, 10:16 PM   #25
Honda-Tech Member
 
Miracle's Avatar
 
Join Date: Mar 2006
Location: Clarksville, TN
Posts: 4,827
iTrader Rating: (0)
motiv8d KMiracle1984
Send a message via AIM to Miracle
Default Re: (xquiset)

Quote:
Originally Posted by xquiset
nice post
Quote:
Originally Posted by ghost_ryder35
Very nice writeup
Quote:
Originally Posted by Doebmx1
very good write up, wish would have been able to read this when i was learning..
Quote:
Originally Posted by Pnoymugen
Good write-up on the sohc vtec. Good Job!

Wow, all positive comments, Im kinda suprised on my first write up.

Looking good. If you guys have anything to add, like a different type of VTEC, or whatever, throw it up here. It needs to be Honda VTEC related though.

Lets keep this rolling.
__________________
My 'Stang Build v. 2.6H
Miracle is offline   Reply With Quote
 
 
 
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
What is VTEC? - school project accuracy Corksil Honda Civic/Del Sol (1992 - 2000) 24 06-03-2011 10:22 AM
history of vtec and vvt. raverx3m Tech/Misc 0 07-19-2010 10:32 PM
Del Sol B16A Sir2 revs dropping and sputtering around 3k elwuudz2 All Motor/ Naturally Aspirated 2 02-04-2008 08:13 PM
best explanition of vtec leroyb Honda Civic/Del Sol (1992 - 2000) 15 04-26-2007 06:19 AM
Do you know your DOHC VTEC? sleevedgsr Acura Integra 11 01-11-2005 08:45 PM


Tags
2004, bad, cam, civic, d17a2, explained, good, honda, hondas, preventing, sensor, stage, tps, vafc, vtec

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



Join Honda-Tech.com

All times are GMT -8. The time now is 08:49 PM.



2014 Copyright, InternetBrands Inc.
Powered by vBulletin® Version 3.8.7 AC1
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.

Honda and the Honda marquee are registered trademarks of the American Honda Motor Company, Inc. Neither American Honda Motor Company nor its subsidiaries or affiliates shall bear any responsibility for Honda-Tech.com content, comments, or advertising. Honda-Tech.com is not affiliated with American Honda Motor Company in any way. American Honda Motor Company does not sponsor, support, or endorse Honda-Tech.com in any way. Copyright/trademark/sales mark infringements are not intended or implied.
Emails & Contact Details