just curious

 

the i-vtec is intellegent.
it went to college.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FutureITR &raquo;</TD></TR><TR><TD CLASS="quote">the i-vtec is intellegent.
it went to college. </TD></TR></TABLE>

seriously i laughed when i read that...that was funny but seriously

k well i found something but it doesnt really make to much sense to me can someone spell it out in easier terms

The i stands for intelligent : i-VTEC is intelligent-VTEC. Honda introduced many new innovations in i-VTEC, but the most significant one is the addition of a variable valve opening overlap mechanism to the VTEC system. Named VTC for Variable Timing Control, the current (initial) implementation is on the intake camshaft and allows the valve opening overlap between the intake and exhaust valves to be continously varied during engine operation. This allows for a further refinement to the power delivery characteristics of VTEC, permitting fine-tuning of the mid-band power delivery of the engine.

 

i know it stands for intelligent but whats so intellegent

 

well, I'm not a biggy on this, but i will give all the help i can, and learn the rest from someone else also. The K24A2, VTEC operates on both camshafts, not just the intake camshaft. And on the K24A2 and K20Z3, which have 3-lobe system, both valves switch switch from high and low simultaneously, compared to only 1 of the valves. The rest, i'm still trying to figure out completely. hope this helps for now, i'll check up and figure out the rest, so your not alone with all this. good luck

 

For anyone who wants to know, all this can be found at:
http://www.all-acura.com/article95.html
http://www.all-acura.com/article67.html
http://www.honda-forum.com

Happy reading, folks.

VTEC
VTEC is an acronym for Variable valve Timing and lift Electronic Control. It is a mechanism for optimizing air/fuel mixture flow through the engine.Honda first introduced the DOHC VTEC mechanism in the US on the 1990 Acura NSX. But a year earlier in 1989, the Japan Domestic Market got the world's first dose of DOHC VTEC in the 1989-1993 generation of the Honda Integra. The 1989 DA6 Honda Integra RSi/XSi used a 160hp variant of the B16A DOHC VTEC engine

VTEC, as most of us know, was a way to attack the compromise of low end power vs. high end power. It was pretty much impossible to make an engine with high output in the upper RPM range without sacrificing drivability in the lower RPM range. The physics of it work in a way such that a slower moving engine cycle responds better to low lifting valves with almost no overlap. However as the engine cycle speeds up and demand for air increases, the engine will need higher lifting valves with more overlap to meet the demand. If you have high lift/overlapping valves at slow engine speed, the engine won't be able to expel waste gases fast enough before it breathes in again. So instead of the nice breath of combustible oxygen air your engine was expecting to get, it gets a load of its already burnt carbon monoxide gas. You'll notice this happening with a loss in low end torque as well as shaking, sputtering, and crackling when the engine is at idle.

On the other side, if you run low lift valves you'll get your nice idle and smooth response in the beginning. However as the engine spins faster, it can't circulate the air quick enough and the valves end up closing before the engine has completed breathing in all the air it needed. You'll notice this when your engine is pushed harder, and your acceleration seems to get weaker rather than stronger.

Every camshaft has a rotation per minute which is perfectly matched with the cam lobe profile. You can usually tell how a cam was designed by looking at where the engine's torque peak occurs. The solution to that was to change the valve lift and timing on the fly, giving the driver excellent response at both ends of the RPM spectrum. Honda's solution was VTEC. An acronym that loosely stands for Variable valve Timing and lift with Electronic Control.

There were a couple ways that Honda implemented VTEC, most of them actually for fuel economy believe it or not. There are currently five different types of VTEC motors on the market. First is the DOHC VTEC. Then there is the SOHC VTEC or just VTEC. There is also a VTEC-E which has no performance value; it is used to for economy purposes only. The 3-Stage VTEC has three different stages that is used throughout the RPM band. And the new I-VTEC found in the K series which is just a little more advanced version of the DOHC VTEC.

So how does VTEC work? Well inside a pair of valves there are three cam lobes. The two outside ones are for lower RPM’s and the middle one works at higher RPM’s. As the cams spin around, the valves are pushed into the open position and air is let into the combustion chamber. The center cam lobe serves no purpose at low RPM’s and just spins along with the camshaft. This is pretty much the normal operation of the valve train, and this cycle will continue until it is directed to do otherwise. In order for the ECU to initiate the VTEC system, 5 engine conditions must be met:

Temperature: The engine must have reached normal operating temperature.

Throttle Position: The throttle must be open far enough to allow for increased airflow in

VTEC.

Vehicle Speed: The car must be in motion (wheels spinning).

RPM: Engine must spin to its target value. A GS-R for example starts at 4400 RPM’s.

Oil Pressure: The engine must be operating with normal and safe levels of oil pressure

determined by the VTEC pressure switch.

The ECU will send a signal for a spool valve to open. When this valve opens, oil is allowed into the pivot shaft inside the valve rockers and directed into the center rocker. Inside the center rocker, a set of pins are forced outward by the oil pressure and lock inside the rockers to both sides. This entire process occurs in 1/10 of a second. The valve rockers are now locked together and when the cams spin back around, the valves will be actuated by the single lobe in the center rather than being individually actuated by the smaller lobes. This will cause the valves to have an increase in lift and their duration has been increased allowing more air into the valve and successfully altering the valve timing.

Once the engine decelerates, the oil pressure holding the pins outward will be cut off and a return spring will pull the pins back into the center rocker where they will lay in wait for the next trip into VTEC. The smaller cams will then take over and the engine will return to normal operation.


i-VTEC
So what's the difference between VTEC and the new i-VTEC. The i stands for intelligent, so the new VTEC is an intelligent system. The new i-VTEC system combines features from both the B and D-series motors, creating a greater powerband width with cleaner emissions.

Now, for those of you who are not acquainted with the D-series motors, they are the motors which can be found in the non-Si versions of the Honda Civics. These motors are not as sophisticated as the B-series motors that are found in the DOHC VTECs such as the Integra GS-R/Type R or Honda Civic Si. The D-series VTEC system simply advance and retard the cam to widen the powerband. The new i-VTEC system capitalizes on the strengths of both by advancing and retarding the cam duration timing as well as utilizing 2 different cam profiles.

The name Honda has coined for their advance and cam retarding mechanism is VTC, an acronym for Variable Overlap Timing Control. Simply put, i-VTEC = VTEC + VTC. The new VTC mechanism that has been added to the i-VTEC system allows for continuously varied valve overlap. The VTC mechanism allows for fine tuning of the mid-band power delivery. VTC is not a new concept, variable valve timing has been around for awhile and can be found in a number of vehicles. Some current examples of implemented variable valve timing motors can be seen in Toyota's VVT-i , and BMW's VANOS/double-VANOS motors.

Basically, all VTC does is varies the valve opening overlaps, which is illustrated to the left. As you can see VTC simply changes the relative alignment between the camshaft and its driving sprocket. VTEC alone only creates two or three cam profiles. However, VTC allow for continuous valve timing changes, in other words creating infinite cam profiles.

There are numerous other innovations that have accompanied the new i-VTEC system. Most notable is the engine orientation change. The new orientation has the intake valves facing the front of the vehicle and the exhaust valve facing the rear. This is the same engine orientation as the Japanese Grand Touring race cars.

 

Basically:
Vtec switches between two cam profiles

and

Vtec-i does the same thing, but it also is continually advancing and retarding the intake cam for better power and mpg..

 

Well, I was going to write that for people too lazy to read . And it's i-VTEC. Not VTEC-i.