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honestly people the answer is easy. look at the dyno. why is there even a debate about this?

the D17, just like every other honda, sees a big jump in torque on the dyno when the hi cam profile (vtec) engages.

 
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my hi cam engages at 4200rpm and shuts down when the rpms drop below 3700, gotta love the vafc2, if it kicks in any earlier it dosen't really help much.

 
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i thought it switched to high cam from low cam at 3 rmps... someone said that on here and was takling about how u can get better gas mileage by staying under 3 rmps in low cam..

 
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whatever man im just tellin you when the lamp lights that is hooked into my ecu according to the vtec light diy

 
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Exactly, mine is set to come on at 4400 and goes off at 3900


Can anyone actually hear there vtec kick in??

 
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my friends 6thgen u could hear it.. with short ram intake if ur in first gear or something and increase ur rmps slowly, u can hear it engage at 5,500 rpms

 
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can someone tell me when vtec and high cam is supposed to engage? and are they the same thing? im confused

 
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How bout on a d17.........anyone? I know i can!

 
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yup. thank you for confirming the 4200rpm i had stated earlier. and typically yes, the hi cam will disengage several hundred rpm below the engagement point.

 
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you should read my post on page 2. vtec is a system that incorporates a low cam profile and a hi cam profile (standard vtec that is.... not vtec-e or 3 stage vtec). the hi cam kicking in is part of the vtec setup.

 
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thanks s2000 man, what about is the thing at 5,500 rmps then? or is there no such thing that goes on there

 
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When my Vtec engages my wheels start spinning from 4500 rpm's right up to 7500 rpm's..Man its a real turbo

 
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our redline is way below 7500

 
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he goes thru the red.. duh

 
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Yeah I have 10 000Km's and its my 4th set of tires...

Ive also had to wear Neck collars cuz the torque snaps my neck and head back so hard..
VTEC is so nice....

 
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So i guess im the only one who can actually hear Vtec turn on? For those that say they cant hear it, something must be wrong!!

I got video proof if someone wants to hear!

 
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lmao rep to you

 
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Its true when I test drove the 05 Civic Si Sedan The salesguy said it had as much torque as a Mustang Saleen. So when the car got at 4500 RPM he grabbed onto the O **** Bar beside his head and **** in his pants when the vtec engaged....The torque steer was so bad that i know have to work out 5 days a week just so I can jold on to the steering wheel when the Vtec kicks in...

 
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anyone have similar feedback about v-tec

 
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Use VAFC-II, the information shows that D17 VTEC as follow:

Lo->Hi: 3250 rpm
Hi->Lo: 2300 rpm
Pressure: -94 psi (forgot the unit, something like that)
Throttle: 2%

All the information is sent to VAFC-II by the ECU. A good function of VAFC-II is the "reference mode" so it can take a factory number for reference.

By interpreting the information above, it reads the factory setting as follow in word:
1. VTEC will definately be at high cam lobe(16 valve high lift) > 3250 rpm, no matter how light you press the throttle. It can be called a "critical point".
2. VTEC will definately be at low cam lobe(12 valve) < 2300 rpm, no matter how hard to press the throttle.
3. Anything between 2300 and 3250 rpm is purely a function of throttle position and intake pressure.
4. There is a 200 rpm delay to switch from low cam to high cam initially(first gear that engages VTEC), which means even at full throttle, VTEC won't switch to high cam until it reaches 2500 rpm in first gear, or whenever the first gear that the VTEC engages.
5. VTEC will switch back to low cam whenever it detects engine speed dropping any 200rpm below 3250 rpm. It will NOT switch back to low cam above 3250 rpm for any reason.
6. VTEC will switch back to low cam whenever the function of throttle and pressure indicates that VTEC is not needed.

So basically it is a function of rpm, pressure and throttle position.
Summarize it:

<2300 rpm, no VTEC
2300<N<3250, rpm, pressure and throttle dependent
>3250 rpm, absolute VTEC

Note that the pressure and throttle therasold declines as rpm rises. ie. It may take up to 50% throttle and very high pressure like -4psi to engage VTEC at 2500rpm, but it takes very little, like 2% throttle and -94psi to engage at 3240rpm(just 10 rpm below critical point).

 
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You should note that taking torque graph out of a VTEC car is useless. When VTEC switches to high cam, it actually lowers the torque instead of raising the torque, then slowly rasing agian. Very simple, horsepower is the time derivative of torque. If torque doesn't drop at its limit, your horsepower will not rise beyond that point. Look at where your initial torque drop, it is your VTEC engagement point. Of course, if torque drops too much then horsepower will not rise either. Look at how the torque curve relate to the horsepower curve.

 
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Thanks for clearing this up. I knew that 4300 rpms was kind of high for VTEC to kick in. Funny how some people are so arrogant and think they know everything because they looked at some chart posted on the internet. LOL

 
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you're incorrect my well intentioned friend.

the reason the torque curve drops is NOT because the high cam kicks in. the torque curve drops because the low-cam profile is nearing the end of it's efficient operating rpm.

also notice that this "drop" in torque lasts about no more than a mere 300rpm or so.

So if your theory was correct, and VTEC was kicked in by 3200rpm, then by 3500rpm the torque curve would be seeing an increase in power. Which is doesn't. The decrease ocurrs at about 4000rpm, and the hi-cam engages at about 4300rpm.

This is supported by the torque curve dyno. Oh but you can't look at the dyno and surmise this? sure you can, let me prove plenty of dynos that support my point.



note the slight drop in torque before the hi-cam kicks in at 5900rpm on the Honda S2000.


Here's a 98 prelude, in which the hi-cam engages about 4900rpm. Again note the slight drop in torque from the low-cam almost exhausting itself, and then the hi-cam taking over.

 
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you're trying to tell me the hi-cam is engaged by 3200rpm on a civic that redlines at 6800rpm? heck, the dyno hardly even shows the car delivering any power at 3200rpm.

regardless, I have asked a few people I know to look into this and find out what the true stock hi-cam engagement is. not only is one of them an electrical engineer who works on car ECUs (specifically hondas) but the other also happens to own the dyno shop where Hondata does their research and developement.

And by the way, all references to vtec kicking in are during closed loop operation.

 
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Civic redlines at 6950

 
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redline is 6800. rev LIMITER is 6950.

 
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I cannot imagine how many ppl are thinking D17 engages VTEC at 4500+ rpm.

Read more article before posting any reply on this. Read the VTEC tuning articles, especially on where a VTEC engagement point is supposed to be tuned. If you read carefully, you should find something reads "VTEC engagement point should be set at the initial torque drop point".

Here we go, we have a 16 lobe camshaft vs. 20 lobe camshaft in older VTEC. What it really means is, it is built on the concept of VTEC-E. Building on VTEC-E doesn't mean no power, but means VTEC engages at fairly LOW rpm, and pressure sensing is incorporated into the system. By the definition of VTEC tuning, a 12 valve operation will end its torque output at around 3000rpm, which it has a first peak torque before 3000rpm. Next, it will have the high cam torque peak, for the 16 valve operation. So it actually has 2 peaks for D17. Do a dyno from 1000rpm on you will see. Doing it from 3000rpm just ignored the first peak. I see this because I actually asked the dyno guy to do from 2000rpm, then I read the graph.

Also, if any of you is posting torque/hp curve please have a torque/hp curve crossed at 5250rpm or it won't make any sense to read it.

 
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This entire post doesn't even apply to the D17 Civic.

There is only ONE STAGE VTEC in the D17 EX engine. This is NOT a VTEC-E ENGINE!! NOR is it a 3 stage VTEC engine.

it's just plain old SOHC VTEC. all valves are open at all times on the D17 civic and there is only 2 cam profiles on the cams, which enable the intake valves to open for greater duration when the hi-cam profile kicks in.

As for VTEC tuning and when VTEC should kick in, the point that you should engage the hi-cam is when the low-cam profile could no longer produce an air/fuel flow efficient enough to support the engine vs what the hi-cam can produce. In other words, utilizing the low-cam profile as much as possible for low end air/fuel flow until it would be more efficient to use the hi-cam profile.

Now, THIS REPLY was directly from one of the technicians at the dyno shop where Hondata does their R&D. And as I said, we will soon have the definite answer as to when exactly the D17 civic engages the hi-cam profile during closed loop operation.

 
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The tech you mention above isnt really telling us anything we dont already know.

 
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If this thread is not talking about D17, then it's my fault. But what I said is for D17A2/6 and D16Y VTEC-E engine. Somebody PM me and asks me to reply this thread with information on D17.