Is it possible to switch on/off VTEC?

I've seen lots of posts inquiring about this topic mingled in with other posts... But has anyone tried it? I would like to be able to switch VTEC off when I am cruising on the highway - and when I hypermile (which is everytime I commute). Then I could switch it back on when I feel like driving more 'spiritedly'.

 

since the fit has 'old school' vtec which only actuates at a certain rpm, (i think the fits' is around the low 5k's) you shouldn't have to worry about it decreasing fuel economy unless you are constantly flooring it. (which would be counter-economical anyway, VTEC or not.)

 

Actually with low acceleration vtec kicks on at 3400. But will activate anytime you accelerate real hard.

 

vtec is a system for the engine's breathing, it's not as much on/off as it is high/low.

with the sohc L15a, you're either on the gas-sipping cam profile(that keeps one of the four valves closed) or the higher flowing cam profile(that uses all 16). basically, keeping the rpm low and the acceleration down will keep you on the gas-sipping cam profile anyway, so the way to turn vtec "off" is to drive more conservatively/economically. think of the gas pedal as the vtec switch, and don't rev high if you want to save gas. it's pretty much a passive system, it makes things work better (more efficiently), not differently.

if you were to actually turn it "off" so it used the (12 valve cam setting) all the time, you'd have reduced fuel efficiency in high flow situations because the engine would starve itself. vtec on the L15a is economical no matter if it's on or off.

*Edited for correctness, thanks jits*

 

with a sohc engine, like the l15a thats in the fit, there is only one cam hence the single overhead cam(sohc) title. The "vtec" in the fit offers a 12 valve to 16 valve operation which really is more for fuel economy and performance and is different then a dohc b series or k series engine.

The four extra valves on the l15a open up as the "vtec" kicks in to allow more air into the chamber on each piston. I was wondering if someone has designed some type of modification to open the four extra valves to run all the time so it would run 16 valves.

There is some excellent info in this article that describes the details of the l15a and l13a dsi engines.

The Truly Amazing Honda Fit/Jazz

 

I have an Apex Neo installed and with the sensor check on the VTEC engages anywhere past 2.5k rpm if you go past 15% throttle.

I tried using the VTEC controll of the Neo to see how I could affect VTEC engagement and after flooring it through two gears the check engine would turn on and I'd have to disconnect the battery to reset the ECU. After that little experiment I chose to leave VTEC control OFF on my Neo.

 

nttdemented - thanks for the information. So I guess it's not possible.

 

The VTEC engages at 3200rpm on the USDm fit , we have tried Apexi Neo, Greddy Emanage and we are not able to lower the VTEC. I guess on K-Pro can do the work.

 

dang, once aj's guys come in, everything is explained...well at least to the question i have in mind...gosh i need to visit aj more often, but damm it's a long drive...lol for the USDM FIT, i always felt the vtec engages at 4k rpm, i guess i felt it wrong, i do need k-pro