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I know that there's been a lot of confusion about our VTEC. After a long period of confusion and examination about parts, and look at other people's opinion, the result comes up.

 
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The main difference between D17A2 and older VTEC is, the older VTEC has 3 lobes per cylinder, and 2 of them are for regular 16 valve operation. The thrid high-cam engages at about 4500RPM so that it creates more power, and the jolt is felt.
D17A2 uses 2 lobes per cylinder, which is like VTEC-E without lean burn, that at low RPM there's only 12 valve mode. However, take a look at the profile, the "operating" low RPM intake cam is actually a "high-cam" compared to the old VTEC. This way, in contrast, our engine becomes VTEC hybrid instead of VTEC-E. (By definintion, VTEC-E is a lean burn engine, otherwise the E has no meaning.) We can still call that VTEC-E, but it does not mean to be a VTEC-E.
The only difference is, because of the 2 different profile of lobe(which in volume is a little smaller than D16Y8's low cam mode), more torque is generated. And, since the engine will operate at 16 valve mode, it is the same as moving the high-cam to engage all the way down to around 3000RPM. Therefore the car is much more smooth than D16Y8, and you don't feel the jolt when VTEC kicks in.

 
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nice explanation.

btw, dont listen to anything that comes out of prod's mouth

 
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So, in short, which VTEC system is better? And our VTEC engages at 3,000 rpm? Huh? now I'm more confused

 
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It "engages" at 2500 RPM. If you have a I/E you can kinda hear it switch. But at the same time I have more top end HP than my friends y8.

 
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so freakin true

 
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If you want fun, then the ordinary VTEC(like DOHC VTEC or at least D16Y8) will be better because of the jolt and sudden pull. But in terms of performance and riding comfort, D17A2 is better because of the smooth transition between low and high cam and the nice straight HP curve. Remember the last time you or your friend went to the shop with ordinary VTEC to tune for a nice straight curve(to maximize power to the whole powerband)? How hard was it(note the jump from non-VTEC to VTEC)?

 
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And guys, sorry for the horrible drawing. I wish I have some professional CAD software to draw it but i don't.

 
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I think the D17A2 setup is a better arrangement for low-end torque and high-end horsepower. Basically you will want 2 very low profile lobe to start with, but if the profile doesn't change, it will kill the high-end horsepower. If you have 2 high-cam engaged at low RPM, then you kill the torque.

But in fact, if we have VTEC controller, we should delay the VTEC engagement point for D17. I will explain it later.

 
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In reality, any VTEC engines smaller than 2.0L are using 1 normal lobe and 1 flatter lobe at low RPM. I got the data from B16A2, the low-mid RPM lobe are 33.088 and 34.978, about 2mm difference. In fact, this arrangement will generate better torque at low speed. At high RPM, the 36.267 lobe kicks in, then there's the pull. Our engines actually breath better at low RPM than B16A all the way to about 4000RPM (It is always true for SOHC engines that at low RPM SOHC breath better).

Our engine's design is good so that at low RPM, it seems like it is running at 12 valve, but in terms with volume, without lean burn, it is running just as good as 16 valve(the longer lobe actually induce alot more air to the cylinder). However the engine's VTEC engagement is too low so that it doesn't perform the best it can. I would suggest to change the engagement point to run it as an ordinary VTEC, to engage about 3500~4500 RPM would make it a little better.

 
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i got no vtec in my crx, but it is like i am in vtec all the time with my cams that have the gsr vtec cam profile. and i wont pass emissions in other states except florida since there is no emissions here

 
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If you don't have VTEC control in your car and just using the VTEC cam, then you are always running in hi-cam mode, just not VTEC. Anyway, is the low-end acceleration good? What about idling?

 
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I always though sohc vtec engines utilizes the 3 stage system

 
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There exists a 3 stage VTEC system, but only on one engine(D15 something, i forgot).

Anyway, even the DOHC i-VTEC (except the ones with red covers, hee) are 2 stage and have only 2 different profile lobes on intake and exhuast sides(the red ones have 3 on intake and exhaust).

So if our engine is VTEC-E as people say, then the regular "black cover" DOHC i-VTECs will become DOHC VTEC-E with VTC. Funny? Therefore becareful on using the term VTEC-E.

 
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Some how vtec-e does not sound right, if the d17a2 was a vtec -e engine, how is it that it generates more power then the d17a1 and d17a5 engines ?

But a hybrid vtec combo vtec- e sounds somewhat more precise.

 
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This is what made people confused.

First of all, Honda advertised the 01 Civic EX as a 127-hp VTEC-E engine.
Then, for 02, 03 and 04 Honda changed that to 127-hp VTEC engine.

It's the deal. Looking back to the first picture, the D17 design come from an original VTEC-E engine, which is 12 valve at low RPM and 16 valve at high RPM. The D17A6(HX) engine also has a high lobe and low lobe that is ALMOST the same profile with the D17A2(EX) engine. Therefore theroretically the EX engine becomes a VTEC-E.

But in real life, D17A6 is a lean-burn engine, D17A2 is not. So comparing D17A2 and the old D16Y8(ordinary VTEC) there's no difference at high RPM(high lobe), except that D17A2 engages hi-cam earlier. So it is a TRUE VTEC engine.

VTEC-E and true VTEC adds up to be a VTEC hybrid. But we can call it either VTEC-E or VTEC.

 
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There exists another type of VTEC hybrid, the cam actually looks like 3-stage cam, but the engine is a 2-stage(just like ours). The primary lobe is a normal lobe, and secondary is a flat lobe. The mid lobe is about the same profile as the high lobe. It was developed for Honda 3.0 VTEC and 3.2 SOHC VTEC because of the engine size. It runs 18 valve at low RPM and at ~3500RPM switches to 24-valve.

** The definition of VTEC hybrid is that, an engine that is 12 valve VTEC-E at low RPM and directly go to high-cam VTEC without having "normal" 16 valve operation.

 
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low end its the same, and the power band has a wider range. idlng sounds ok but it is sort of ruff and easier to stall. plus my thicker valve springs and retainers from crower allow me to rev to 8k rpms with no problem. (rev limiter is set at 8.4k rpms) check crowers site crower.com and look for the 62403 cams for dohc non vtec. same profile as the gsr cams on vtec.

 
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Here's the proof of "black" DOHC i-VTEC.
Take a look at the intake side(at the buttom) and exhaust side.