VTEC kick?

[spetz]

Does Honda make VTEC's to have a kick so it differentiates itself from other NA cars?

I was thinking about it, and even with the same cams/setup on a VTEC engine, couldn't the VTEC engagement point be altered to where the cam lobe power outputs meet (namely at less rpm) so that there is no kick?
Doing so, I was also thinking, would increase the power from the earlier engagement point (say 5000rpm) to the current point at around 5500rpm

And why is there such a sudden change in power over other variable lift systems like VVTi-L, MIVEC etc? Are the secondary lobes much more aggressive to the primary ones in comparison to other variable systems?

[aaronng]

It depends on the cams. VTEC doesn't give any kick or make more power. It's the cams. With the same cams, no matter where you put your camchange point, you'll end up making the same peak power (and probably less power elsewhere)

Because Honda wants drivability at low RPM and high RPM torque, the range of idle to 8000rpm is so wide that the cams alone cannot produce the same amount of torque at the cam change point. If you want to mask the change, then you'll have to use cam phasing as well as changes in the A/F ratio mapping so that you get the same torque and not feel any kick.

And the the 2ZZ-GE with VVTL-i has a larger kick because of a big change in torque when the profiles change. At close to 6000rpm, the 1st cam is not making enough torque and is actually producing less torque than it would at say 5500pm. It's because the engine is not hand prepped with polishing, balancing and lightening. The 2ZZ-GE was made to be a mass-produced engine, unlike the engines in the Type Rs.

[spetz]

So what is different in the cams to MIVEC where the kick is not noticable, just a faster rate of acceleration there after?
Is the change in lobes in MIVEC less than VTEC?

I mean, put it this way, if you move the MIVEC engagement point up by say 500rpm, it will give the same "kick" as VTEC.
So, if that's possible, why isn't it possible to move around VTEC point to get a smooth transition?
For example, assuming VTEC kicks in at 5500 rpm, does the high lift cam make less power than the low lift cam at 5400rpm? I just think that within 5000-5500rpm there should be a point where both cam profiles would make roughly the same power

[steve]

It's because the engine is not hand prepped with polishing, balancing and lightening. The 2ZZ-GE was made to be a mass-produced engine, unlike the engines in the Type Rs.

Not all honda vtecs are hand prepped polished/balanced/lightened...
B16 and H22's still have this same "kick"

[saxman]

So what is different in the cams to MIVEC where the kick is not noticable, just a faster rate of acceleration there after?
Is the change in lobes in MIVEC less than VTEC?

I mean, put it this way, if you move the MIVEC engagement point up by say 500rpm, it will give the same "kick" as VTEC.
So, if that's possible, why isn't it possible to move around VTEC point to get a smooth transition?
For example, assuming VTEC kicks in at 5500 rpm, does the high lift cam make less power than the low lift cam at 5400rpm? I just think that within 5000-5500rpm there should be a point where both cam profiles would make roughly the same power
whenever I tune an ecu with dyno time, I do as much as possible to get a smooth transition, because that results in the most power.

There are some people that insist on feeling the kick though, even if they are going slower because of it.

[aaronng]

Not all honda vtecs are hand prepped polished/balanced/lightened...
B16 and H22's still have this same "kick"
That's right, the ones that are not hand prepped have a bigger "kick". :)

[aaronng]

So what is different in the cams to MIVEC where the kick is not noticable, just a faster rate of acceleration there after?
Is the change in lobes in MIVEC less than VTEC?

I mean, put it this way, if you move the MIVEC engagement point up by say 500rpm, it will give the same "kick" as VTEC.
So, if that's possible, why isn't it possible to move around VTEC point to get a smooth transition?
For example, assuming VTEC kicks in at 5500 rpm, does the high lift cam make less power than the low lift cam at 5400rpm? I just think that within 5000-5500rpm there should be a point where both cam profiles would make roughly the same power
It depends on how Mitsu decided to tune the engine. From the dyno charts of the FTO GPX, there is only a very small dip in torque at the cam change point, so you won't feel the kick. Maybe they did polishing, balancing and lightening, maybe they have a variable intake manifold, I'm not sure what Mitsu does exactly to the engine at the factory. The FTO's mivec engine being a V6 will also have a different torque characteristic over the I4s.

Usually what engine designers do is dyno the engine with each cam profile. Overlap the dynos and you'll have "twin peaks". The point at which the first peak intersects the 2nd peak is the optimum point. If the engine was designed such that the valley in between the 2 peaks is so deep, you will feel a strong kick. Once you have that valley, if you move the cam point down, you will feel hard acceleration and then at camchange point, no more acceleration. You'll feel a lag as the rpm builds up and torque comes back. If you raise the point to a higher rpm instead, then you won't have a valley, but a cliff! So you'll have a very strong kick.

In order to fill up that valley, you can alter the air/fuel ratios and timing so that at the end of the lowcam you are making more torque, and at the beginning of highcam you are making less torque, so the valley essentially disappears.

[fly_vti]

if vtec doesnt make more power whats the point of it besides fuel econemy

[sever_all_ties]

if vtec doesnt make more power whats the point of it besides fuel econemy

A straight power curve. Good low down power. Great top end. Efficiency.

[aaronng]

if vtec doesnt make more power whats the point of it besides fuel econemy
All vtec does is let you use 2 different cam profiles. I could put vtec with cams with identical profiles on both lowcam and highcam and I wouldn't make any extra power on camchange.

I could put cams for ultra fuel economy, I could put cams for ultimate power on both low and high rpm. It's the cams.

[iamhappy46]

From experience Nissan's NEO VVL systems camshaft change points are at different revs, so inlet and exhaust change occurs sepreately so that the 'power drop' is hardly noticeable.

MIVEC is slighter smoother as ignition timing is retarded just before the cam changes making it nearly impercetable and gives a smooth transfer thru its shift point

[Limbo]

reason why the other Vtec like technology does not have the kick is that they generall only affect timing changes and do not affect the lift on intake and exhaust like honda does. I know this is a fact in the toyota VVTI. The VVTI-L had the lift function in the cams, thus making it very similar to honda's. Each manufacturer does it abit different. It is just that honda were able to mass produce it and add the extra lift, thus add better performance

[aaronng]

Yeah VVTi enhances low RPM torque. But Neo VVL, MIVEC and VVTL-i are similar with VTEC where you have variable valve lift. VVTL-i goes one step further by having something very similar to i-VTEC.