VTEC and i-VTEC on L-Series

[kotarou]

We know that the Jazz/Fit uses the L-Series engine with the VTEC technology.

But I'm confused about this:

GD uses VTEC and GE uses i-VTEC (At least is announced).

VTEC = variable valve timing and lift mechanism. Some sites say that i-VTEC is VTC + VTEC.
Where VTC is Variable Timing Control.

That's perfectly fine if you think on DOHC engines, but is this VTC true on L-Series ? Can a SOHC variate the cam phase? (Remember that one shaft is used to Exaust and Intake valves, if you variate on you change both)

If The L-Series does not have VTC, so what is the intelligent "i-" on i-VTEC present on GE models?

[guest1521]

This might help. It's interesting - to me anyway -  though lengthy and covers the GD model's engine, too, if you scroll further down the article. Just bear in mind that markets round the world variously call Jazz 'Fit' and designated engine capacities vary 1.2, 1.4, 1.5.
http://asia.vtec.net/Series/FitJazz/lseries/

[culzean]

If The L-Series does not have VTC, so what is the intelligent "i-" on i-VTEC present on GE models?

The L series is an 8 valve high compression twin spark engine with fixed cams.

i = intelligent  it means that the VTEC does not just change the valve timing at fixed rpm levels, but looks at all sorts of other parameters like throttle position, load etc.  If you drive the Civic i-vtec in a sedate manner you may never cause the vtec to operate,  may be same on the Jazz GE.    i-vtec also means that the closing of inlet valves is delayed below 3000 rpm on low load to cut down on 'pumping losses' in the engine (which are caused by the throttle butterfly being closed and 'strangling' the engine) the inlet valve closure is delayed and the throttle butterfly is opened almost fully, and because of the delayed closing of the inlet valves this means that  as the piston rises some of the mixture that has just been drawn into the cylinder is pumped back out into the inlet manifold, and in this way the cylinder pressure is lowered and engine power and fuel consumption are reduced. This can only be done because the i-vtec is drive-by-wire (the accelerator is not connected to the throttle butterfly). 

as you find out more about vtec it is a truly ingenious system, where there is more than one rocker arm for each valve,  and several cam profiles are available simply by either linking or not linking the rocker arms together by a little hydraulic pin system operated by engine oil pressure and controlled by the ECU.

[guest3776]

The Honda homepage here in my country has a link called "information databank" and all these things
are very well explained.

I would assume you could find the same link at the Honda homepage in your country.



/ John

[chrisc]

The software controlling the ECU is mapped for over 120 parameters.  Apart from monitoring normal atmospheric pressure, so that cars operated at altitude do not suffer from as much power loss as normally aspirated engines, there are paramaters for the amount of accelerator travel, load on the engine (as in hill ascent, etc).  There is even a parameter that reduces engine performance for the first XXX km. depending on driving conditions in the destination country.  So a Jazz bought in England will not operate optimally in say, Italy or South Africa.  It is possible that UK Jazz drivers who ran their cars from new might have noticed that the car "opens up" after 5000 - 6000 miles.  This is intentional and is used to prolong engine life.

[kotarou]

Well, thank you guys.

I did some research and I found this:

The animations explains a lot!

VTEC
http://world.honda.com/automobile-technology/VTEC/

i-VTEC
http://world.honda.com/automobile-technology/i-VTEC/

Now I understood one major difference on 1.3 i-VTEC

VTEC actuates on a determined engine RPM but always uses all valves.

i-VTEC takes in consideration other factors and the engine RPM but the major difference is that one valve is "turned off" or is idled. So the engine acts as a 12v or 16v mode.

That's really interesting.

On the 1.5 engine looks like the normal VTEC implementation.

So There is no VTC to change the camshaft phase on the L-Series. This makes more sense on DOHC engines.

[guest1521]

It is possible that UK Jazz drivers who ran their cars from new might have noticed that the car "opens up" after 5000 - 6000 miles.  This is intentional and is used to prolong engine life.

Yep! I noticed exactly that but at about 12,000 miles! First I thought I was imagining it, then became sure of it as it was quite noticeable on a particular hill. Your interesting post confirms it. It took 20,000 miles, though, till I felt the manual 'slickshift' and engine had both arrived at their very 'best'. That 'improvement' after 12,000 miles was much more gradual and has now levelled off.

[culzean]

This is Honda Civic i-Vtec

http://world.honda.com/news/2005/4050705_a/video/index.html

the Jazz i-Vtec is just what used to be called VTEC-E (was used in old Civic 1 .5 in the 1990's)

[guest2853]

Interesting link!