What is the difference between I-VTEC and VTEC?

 

ivtec controls both cam gear and ignition timing, and its always changing at all rpms. vtec has a set rpm(for the s2k its ~6k rpm) where the other cam profile is engaged. www.howstuffworks.com has a better explanation.

 

Razor, thanks for the explanation. I guess I-VTEC is better?

 

But VTEC is more "funner".

 

not necessarily. it's all a matter of what you define as better and what Honda decided they wanted out of the engine.

 

http://www.canadiandriver.com/articles/jk/...k/at_011205.htm

 

http://asia.vtec.net/article/ivtec/

At this point, it is important to highlight again that the basic DOHC VTEC system is more than capable of delivering extremely high specific power outputs. i-VTEC is not needed. Witness the 125ps/litre power delivery of the F20C used on the S2000. Again what i-VTEC do allow is for Honda to go for the sky in terms of specific power output but yet still maintaining a good level of mid-range power. Already extremely authoritative reviewers like BEST MOTORing have complained about the lack of a broad mid-range power from for eg the F20C engine. In a tight windy circuit like Tsukuba and Ebisu, the S2000 finds it extremely tough going to overtake the Integra Type-R in 5-lap battles despite having 50ps or 25% more power. Watching the 'battle' brings one point painfully clear. There is a dire need of power from the F20C below 6000rpm. Every time the S2000 sneaks up behind the ITR, it fails to engage in a good overtaking move because the power from the F20C is surprisingly insufficient. The reason for this is because DOHC VTEC makes do with merging two distinct power curves. To get the extreme power levels of the F20C, the wild cams' power curve are so narrow that there is effectively a big hole in the composite power curve below 6000rpm. What i-VTEC can do to this situation is to allow fine-tuning of the power curve, to broaden it, by varying valve opening overlap. Thus this will restore a lot of mid-range power to super-high-output DOHC VTEC engines allowing Honda, if they so desire, to go for even higher specific outputs without too much of a sacrifice to mid-range power.

 

the thing i like about ivtec motors is the low end torque it offers, but then again if i wanted a torque i wouldnt buy a honda in the first place. i personally prefer the standard DOHC VTEC motors, the f20c in my s2k and the h22a in my accord. i like the dr.jekyl/mr.hyde difference.

 

Some people have been putting in lower gears in the rear end for an extra boot in the ass.