can someone explain Vtec?

[grooveline]

Ok, I know what the benefits of VTEC are. However, can someone explain the HOW? How do they transfer from one cam lobe to another? I want to know how the internal work.

secondly. ya know besides honda. Toyota(VVTI), and BMW(lanos) are the only people with an adjustable cam? hmmmm. it makes me wonder what the hell our american companies are doing all day beside playing with each others butts.

[2k2civicSi]

ford has zetec on the 2.0s

[Hondatech]

Edit: Clarified i-VTEC operation

Here's a good pic of the VTEC system:



When you're under the VTEC engagement point, the rocker arms ride on the primary and secondary lobes. These lobes are designed for good fuel economy and low RPM torque. The lobes have slightly different profiles, so one valve opens a bit more then the other to promote "Swirl" in the combustions chamber, which also aids torque. When you reach the VTEC engagement point, a solenoid opens a valve, and engine oil pressure is used to push a pin over and lock the rocker arms to the center rocker arm. The high lift lobe is designed for pure high RPM performance.

On The base RSX and Civic Si/SiR K20, the VTEC only operates on the intake cam. During low RPM operation, four intake valves are opened fully, while the other four open only enough to prevent fuel pooling behind them. This allows for wicked swirl, and one of the reasons our engines make such well felt torque. When the VTEC engages, the High lift lobe allows all eight valves to open fully, giving high RPM power.

The "i" part of our i-VTEC system adds a hydraulicly actuated cam sprocket on the intake cam to the mix. You've all seen adjustable aftermarket cam sprockets, I'm sure, where you can adjust cam timing to move the powerband around for better performance. Well, our system constantly adjusts the cam timing to provide ideal torque and economy for the given situation.

As far as I know, Toyotas VVT-i and BMW's Vanos system use a system like the "i" part, with adjusting cam sprockets, but without the lift control like VTEC.

[Pradamuimui]

I LOVE HONDATECH.....EXTREMELY WELL PUT!!!!!

[xlr8]

i heard the new lamborghini has some sort of variable valves.

[MadMax]

Thats a good explanation of the K20A2 (rsx-s) iVTEC, but the K20A3 (Si and rsx) is different as it only applies to 4 of the 8 intake valves.

[Hondatech]

Good point. Edited original message to clarify i-VTEC operation.

[smapzy]

Madmax, I think it work on all 8 intake valves... our car have 16 valves, 8 in and 8 out. ;-)

[MadMax]

No it doesnt. 12 of our 16 valves never experience vtec - they follow the same cam profile from idle to redline.
4 of our intake valves do, however.
Below 2200 rpm, the engine only uses 1 intake valve per cylinder. The other just barely cracks open - just enough to prevent fuel from accumulating there. This increases the swirl in the combustion chamber and allows the engine to run leaner at idle and thus use less fuel while you sit at a stop light.
Above 2200 rpm, all 16 valves are used as in a normal 16-valve car - except for the "i" aka VTC which alters the intake cam angle.

[2002Si]

variable Valve Timing & Electric Lift Controls and the "i" means "intelligent", hondatec is right, I just figured you'd want to know what it stood for!!:D How is it intelligent?? Well the car actually reacts on the weather and how you drive the car. Yeah, well I was just talking about what it stands for. Where's the "L"?? Just VTEC I mean. And besides, if you don't know what Vtec means and you own a Vtec vehicle you need to do some reading so you figure out what won't screw your car up. Which it's pretty damn hard to screw up a honda unless you're just stupid or are ready for a new engine.

[DamnYo]

Originally posted by 2002Si
variable Valve Timing & Electric Controls

Variable valve Timing and lift Electronic Control

[grooveline]

[a solenoid opens a valve, and engine oil pressure is used to push a pin over and lock the rocker arms to the center rocker arm. The high lift lobe is designed for pure high RPM performance]


Can you explain this part little better? Where are the other rocker arms?

[K20Death]

Fords Zetec is nothing more than a name for the engine, I checked into it. It has nothing to do with cams adjusting at certain rpms, or anything to do with cams for that matter.