It is continually variable, not like Honda's VTEC which kicks in.

 

Ahh right, ok, I always imagined it kicked in at a certain RPM, as you probably guessed. :irked:

 

At what RPM is the VVC system supposed to kick in? Also, does anyone notice a significant difference in there car when it does? My F is VVC and when I rev it high I wouldn’t say I feel much of a difference through the rev range, obviously the engine does become more powerful the higher I rev it, as most engines do, but I would have expected more of a punch when it kicked in. Is it even supposed to behave in this manner?

Stu's answer is fundmentally correct although I found (on my previous VVC) that I could hear the difference shortly after 4750 rpm. Best with roof down, in a long tunnel, 3rd gear, half throttle build up not harsh accelleration then boot it and hear the engine & exhaust change and enjoy!!

 

Most do assume this. The later VVTi's and Vtec's work in more of a similar way to the VVC IIRC.

Basically the VVC mechs try to keep the maximum torque available at all times, hence the very flat torque curve. The VVC is also a bit more torquey than the Vtec due to it being a long stroke small bore engine whereas the later is the other way around.

 

So does it have more power over the full rev range compared to a standard 1.8 or just at the higher end?

 

Stu's answer is fundmentally correct although I found (on my previous VVC) that I could hear the difference shortly after 4750 rpm.

I believe that is to do with other characteristics to do with the induction and exhaust systems than the VVC though.

 

Forget my last Q, found it in another post, cheers.

 

The VVC starts to increase the valve period from as low as 2000 rpm but maximum valve period is not until 6000 rpm. The most significant change in period is at 4000 RPM. So above 4000 rpm is where you will start to see a steady performance increase as the valve period steadily increases. This is a ramped increase not a step increase like VVT.

 

I feel that lovely torque thing from around 4500 all the way to valve bounce :bigeyes: just wants to go, not quite like a turbo, but nice all the same.

 

I could hear the difference shortly after 4750 rpm

So above 4000 rpm is where you will start to see a steady performance increase as the valve period steadily increases

lovely torque thing from around 4500 all the way to valve bounce

So I'm not the only one then?

Of course, loads of people never get their cars over 4000 rpm anyway so the VVC is wasted on them.

 

The VVC actuator is also controlled by oil temperature so it wont activate the hydraulics until the oil is up to temperature. The VVC cams are one profile that have a variable duration whereas the Vtec has separate higher lift /duration cams that are 'switched' in at certain RPM by the ECU.The VVC cylinder head and induction is the key to the power gains over the stock1.8i as it has bigger valves and ports, the inlet manifold has larger ports to suit and this gives the power gains albeit it has to be 'revved'. That said the 1.8i has a good power delivery lower down due to the smaller ports/valves resulting in higher air flow speeds. Strange why MG/Rover has never opted to fit the VVC units to the smaller capacity engines as it would be a bolt on job for the 1.6 engines:idea:

 

Interesting Mike, cheers for the knowledge, BTW, have you been sleeping in on Saturdays? Been down a couple of times and you’ve not been open. Suppose I should phone first but I always like the drive down anyway, been chasing a splitter.

 

Strange why MG/Rover has never opted to fit the VVC units to the smaller capacity engines as it would be a bolt on job for the 1.6 engines:idea:

I suspect its because a 1.6 VVC would have an almost identical output to the 1.8 non-VVC? So they opted for the less-complex/cheaper solution

 

It was originally designed for the 1.4.