Ok seeing the dynos and reading the posts seeing how Hondata was able to shift vtec switch over to a lower point and obviously Honda coulda have done this in the beginning....why wouldnt they keep the car in vtec (high cam) through the entire rpm range and eliminate the switch over...other than a drop in mileage wouldnt there be a flatter power band given the way the power band flattened out when vtec was brought down to 5k from 6k and a possible gain in peak power

just out of curiousity that maybe Hondata can test and give us an example in maybe a reflash 2

 

I was under the impression that the VTEC cam didn't give alot of power in the lower RPMs.

 

Exactly. There would be a significant loss of torque.

That was the problem with pre-vtec engines. They were built with either no torque but high power up the band, or lots of torque down low, but no power past 5k.

 

Not to mention that your engine would idle like a piece of crap.

 

a hondata dealer told me that if they lowered the vtec engagement any more it would detonate, dunno if its true but makes sense.

 

Why would lowering the vtec point have anything to do with idle? I have lowered the vtec point on my SC Civic as low as 2000 rpm during the process of tuning.

 

Actually, I think the questions was why don't they just use the VTEC cam profile throughout the whole rev range, which I imagine would include idle.

 

well what if vtec was engaged at a lower the rpm like jtso said to around 2k rpm what would that end up doing to the engine...or would anything below the 5k leave gaps and holes in power and lead to problems with the engins

 

found some information here:

http://www.leecao.com/honda/vtec/whatsvtec.html

 

Good find!

So in a nutsheel, VTEC combines the best of lower rpm drivability and higher rpm power. Then, I'd venture a guess as to why the TSX engine works well with VTEC switch at 5000rpm (and works OK at 6000rpm) instead of anything lower:
it's because the engine displacement is already relatively big enough (vs 1.5L or even small on older generation VTEC engines) to generate good amount of torque smoothly without the VTEC cam engaged.

Then I have a dumbass question... I've missed the development progress from VTEC to iVTEC by Honda. So what did they add in making iVTEC?

 

Its just a trendy name. Came out about the same time as iTunes.










j/k. Jlukja, who doesn't know either.

 

You got me for couple seconds there!!! I was about to call on you, haha...

I know the "i" in iVTEC is supposed to mean intellegent, but I don't know what kind of intelligence they've added... anyone?

Either way, VTEC or iVTEC still sounds better (and more original... just don't like that VTECH phone/toy brand trying to suedo-copy it!) than Toyota's VVTI (is that what they have?!?)

 

iVTEC adds cam phasing to the mix, for better torque down low...

example would be driving a GSR and RSX Type S... The RSX has way more power down below... because of the cam phasing...

 

cam phasing... is that like making the VTEC switch continuous from "low" to "high"? But I thought there're still only two sets of cams: "low" and "high", correct? Then how do they make it "phase"?

edit: I remember on my '98 Prelude (DOHC VTEC), there's a distinct kick when VTEC switches to high cam at 5000rpm... the kick seems less distinct in iVTEC engines, is that because of the phasing? Or am I just imagining it's less distinct?

The kick was so fun to feel...

 

its called VVTL-i...thank you!! VTEC does sound better than VVTL-i..but Toyota guys dont say VVTL-i...you guys say "when VTEC kicks in.." they say "when LIFT kicks in.." they call it LIFT, you guys call it VTEC. So LIFT doesnt sound too bad..but i think VVTL-i came out for toyota before i-VTEC came out for Honda/Acura..RSX-s was the first to use i-VTEC right? i think the Celica's came with VVTL-i in 2000 or 2001

 

You'll feel the kick better if u had a RSX-s...and gearing is different with the TSX and Prelude..and the TSX's high cam isn't as strong as the RSX-s

 

There are actually both VVT-i and VVTi-L from Toyota. Which one comes first I really have no idea.
There are many answer to the question of why Honda didn't engage the higher profile cam at 5000 rpm.
First of all it would have suffer a bad millege. Just think that if you are parting throttle at 5k and your engine swith over to high profile cams then the engine won't be able to maximize the benefit of high profile cams since air coming is not enought as it's being resricted by less than 100% throttle openings. As for Hondata they know that everybody who purchase their products are probably some kind of car nut who wants MORE powr, so they lower the vtect point so the engine can breathe a little better at high RPMs, which will eventually gives more power.

 

Also, most of us on this board were actually complaning about bad gas millege from a 4 banger engine in our TSX. That's also why millege is an important factor here. Honda has to make a car that everyone will like. NOT just car freak like most people on this board.

 

what about cam phasing? Exactly what is it? How is that done?

There are still just two sets of cams even in iVTEC, right?

Even a link to some write-up, article would be very nice, thanks!

 

With a little help from my old friend Google, it'll give you this
http://www.ukcar.com/features/tech/Engine/vv/vvt_3.htm

 

i-VTEC, is the same as "old VTEC" in that it has three cam lobes, per cylinder, two "low cam" and one "high cam", except they added, in variable cam timing, which the the old VTEC didnt have, and all the vvt-i and vvtl-i engines have this is as well, this is the reason you dont need cam gears on i-VTEC engines, the computer will change the cam timing for you...