i-VTEC same as Type R VTEC

[Chris]

I have been told that the VTEC in the current Type R is like a turbo, it kicks in after so many revs and BANG warp speed captain! Is this the same for the new i-VTEC in our new civics? I can not feel it kick in like a turbo, but I might be wrong, I haven’t really thrashed it yet, too new, if you know what I mean. So if any one out there knows it would be nice to find out how this special i-VTEC works

[basegreen]

Basically you get a kick over the full range of revs, rather than a specific turbo which kicks in at a particular point like the diesel.

That, married with the way the petrol is geared means that the 1.8 VTEC and the 2.2 diesel have broadly similar 0-60 times.

[Bungle]

The system uses different cam shafts that control the timings of the valves. An engine that performs well at highs RPMs will not idle well, and will be ineficeint at low speeds. An engine that idles smoothly and is efficient at low RPMs is not good at producing power at high speeds. Changing the valve timings means you can get the best of both worlds.

At higher revs, when the engine is being pushed, the vtec system changes to a different cam setup to produce more power. You can feel the extra boost when you go past 4000 RPM, and it is similar, just less pronounced than a turbo system.

The note also changes to a whirling roar tather than that horrid metallic thrashing sound lesser engines produce.

I think this about right, if anybody can expand on this or correct me...

Edit: Just read some more info on it... It is not the cam shaft that changes, just the cams or lobes themselves change to alter the timing of exhaust/inlet valves to burn the fuel and air mixture better.

Text copied from http://paultan.org/archives/2006/03/...i-vtec-engine/ there are some great diagrams there, too if you want to have a look.

This is for those who appreciate the technology that goes into a powertrain. How does the new 1.8 liter SOHC i-VTEC engine in the new 2006 Honda Civic achieve good fuel mileage (Honda claims 1.5 liter fuel economy during cruising) while producing a respectable 140 horsepower and 174 Nm of torque? Let’s have a look at some of the technologies that went into this new engine - the R18A1.


According to Honda, during low load driving conditions like highway cruising where the driver would be pressing the accelerator pedal only slightly, the engine experiences pumping losses due to the restricted air flow created by a throttle butterfly that is almost closed. Pumping losses and air resistance result in a negative impact to fuel economy Using a conventional mechanical throttle this cannot be avoided. Low speed = small throttle butterfly opening. Pedal to the metal = big throttle butterfly opening.


Honda got around this using Drive-by-wire and a fuel-economy optimized i-VTEC system. The i-VTEC system for the 1.8 liter SOHC engine has 2 sets of cam lobes, one for high output and one for low load conditions. During low load conditions, the pumping losses are avoided by letting the throttle butterfly open wider than it normally would. To offset the larger amount of air coming in, the intake valve timing is delayed. This reduces pumping losses up to 16 percent.





To increase fuel economy, Honda has also taken steps to reduce friction in the engine. Piston skirts are coated with Molybdenum disulfide, and oil rings are ion-plated to ensure reduced friction. This provides a 10% reduction in friction.


Other technologies include a variable-length intake manifold using longer manifolds at low RPMs and shorter manifolds at high RPMs for an optimum ram effect and piston oil jets which cool down pistons to avoid engine knocking. As a result of these technologies and a compression ratio of 10.5:1, this 1.8 liter SOHC i-VTEC engine makes 140hp at 6300rpm and 174Nm of torque at 4300rpm[/url]

[Chris]

Wow very technical, thanks guys. Makes you appreciate this engine even more!