thats what i thought as well.. but i think that this vtec thing will not just open up like that.. you'll have to ram your rpm to get the feel of it..
example 1:
You want to overtake a slow car.
You are in D.
Press throttle.
You managed to overtake the car.
Speedometer now: maybe 90/100 kmh
You feel slight edge.
But it was actually your car downshift the gear.
Then gear up again up to gear 5.
RPM is about 2.5 to 3
Question: Does the vtec kicks in?
Answer: I don't think so. Every auto car will actually behave the same. (correct me if i'm wrong)
example 2:
You want to overtake a slow car.
You are in D.
You downshift the gear to D3 manually.
Press the throttle.
RPM is up to 5 or more.
Speedometer now: Maybe 120kmh or more.
Then only you put to D.
Overtaking is easybeezy. Maybe you had just felt that 120PS.
Question: Does the vtec kicks in?
Answer: Hell yeah. Actually, i think the vtec kicks in at about 4.5 to 5. You can feel the famous 'vtec pull', but not that much. The gears and all are not meant for tracks or racing.
Well, that are based on my q&a with my 'Honda' friend. He owned a DC5. I've never been in his DC5 to feel the vtech kick in thing but my other friend had his. From his argument, normal D will not actually put your car to the fullest of its capability. To feel the vtec is actually to drive your Auto car, Manually. According to him as well, his sister's Civic FD vtec kicks in at around the same RPM. You can actually start from standstill using 1, then only change to 2 (anytime you like) after you felt the vtech urge, then D3 then only D after you 'satisfied'..
Pressing D will not open vtech meh? Yes, it will, eventually.. but your vtec is opened at gear 5 lah kot.. how bout other gears?
As there are many readings (here and fb) saying that this car (read: engine) is underpowered.. well, what can i say? I can say that it is not underpowered, it was actually a case where you don't know yet how to drive (read: use) it.. to gain 100kmh quick is not that hard. You can do it in D3 mode je. I didn't do my own timing as yet, but records shown it took about 8 seconds to gain 100kmh? But you'll have to use the 'Manual' for this vtec thing to assist you.
If this vtec thing is in every gear in D mode, you'll surely visit the fuel pump regularly boss.. So, think twice before happily open your vtec everytime
Tried that, done that.

i don't know where you are going to with this...
in terms of the vtec cam kick feel of the b16b, b18c, k20ar.... i can tell you it's not there whatever you do... the l15a7 is built to be a consumer engine... not an outright performance engine... else, it won't be outputting only a measly 120ps for a 1.5l...even the b16b 1.6lit had in excess of 160 horse on tap which is just a notch above 100 horse per liter...so, if you expect the feel of the performance engines...you'll be in for some heavy disappointments...
and the VTEC will engage in all the gears and not 5th alone... if you plant your pedal into the carpet from standstill... every gear will shift up around 6.5k revs.. it depends on your throttle inputs as i said before... this L series engine gives you the feel of a slight surge when the VTEC engages and not the feel of a kick like from it's big brothers... you just feel the power keeps going on rather smoothly rather than tapering off until it upshifts...even if it only engages in 5th, it's a bit rather pointless as you say it will be around 4.5 to 5k revs which means the car is most likely traveling above 160kph already and acceleration at that point upwards is dang slow.. i doubt you can feel anything at all... if there is anything to be felt at all... it's during the first and 2nd gear pulls.. even 3rd feels a bit weak already...
so, if it's a throttle problem... it is the same as any car.. if you floor a vios or a city / jazz all the time... it is going to be the same outcome which means more visits to your friendly local drinking hole...