RogerPodacter

Just curious about this. I-vtec is new and must be better than the older generation Honda engines. But what exactly is different/better?

shaf

This page explains both the old vtec and the new, as well as the differences.

miner

'Old' VTEC had 1 cam lobe. I-VTEC has 3 cam lobes for less pronounced changeover - many smaller 'steps' vs one big step.

captainjack

Great, simple breakdown. Especially for us non-gearheads.

TinkySD

That's not 100 percent accuarte, but close

I-vtec in this engine means VTC or continuously variable intake valve timing. the normal vtec(exhuast side + cam lift/duration) is an identical system to the old layout. Only the tsx, rsx-s and new j30a4 use 3 cam profile system instead of two. All these little changes lead to a flat torque curve so you never get a super surge of power. All the upside of old vtec is there(and then some with the added vtc) you just don't feel it because good power is being made through the entire rev range.

fdl

The TSX i-vtec engine is a great...and it does have power downlow thanks to i-vtec...but it seems to lack top end. THe car runs out of steam a bit after 5k rpms or so...(although it gets some of it back at 6200).

TinkySD

Yeah totally. This engine was setup for drivability(low end/midrange) not top end power. The weaker top end really limits the dragstrip numbers(especially with 6sp) The good news is most mods really improve teh top end. The AEM sir gives a 5-6.5 lbft gain from 6000-7100 rpms along with it's healthy midrang gain.

kenbiddulph

The two most stark examples of how different i-VTEC is from VTEC is comparing the K20 in the Civic Si/RSX and the Prelude's H22.

In the RSX, it doesn't feel as fast as the Prelude, but it is and in fact faster. The Prelude has such a sudden burst of torque that it is almost necksnapping in the 4th generation. You definitely know when VTEC is engaged.

DEVO

The... "i" in i-vtec is in the timing of the engine. It's always changing depending on the RPMs. Where as in the old system that wasn't the case.