What is the difference of the VTEC and I-VTEC ?

 

The I

 

it's intelligent

 

VTEC basically has 2 cams, low lift, and high lift (yes I know a lot more than that). When "VTEC" kicks in, it simply switches from low to high. Easy as that.

This intellegent VTEC **** is a little different. There are still 2 sets of cam lobes, but just before engagement, something happens with the rocker arms to allow it to engage more smoothly, (not sure exactly what)

I think.

 

wrong, all i-VTEC is is VTEC with VTC on the intake cam to advance or retard timing

* from the RSX brochure

"i-VTEC features Variable Timing Control (VTC) a new device between the intake camshaft and its drive sprocket that can advance and retard cam timing in infinitely small degrees, always matching valve timing perfectly to engine requirements"


[Modified by WR93EG, 11:34 PM 11/5/2002]

 

this foo gets all personal

 

OK, considering that nobody has quite hit the nail on the head yet...

i = intelligent in iVTEC. what's so intelligent about it? the fact that the timing is now continuously adjustable based on engine rpm, throttle position, load, inlet air temp, etc. iVTEC has 4D (as opposed to 3D) fuel maps too, which the engine will switch between the 6 maps depending on any one of its input parameters. this has also lead to part of the problem with dynos for the K20. a slight variance in temp may cause the maps to be swtiched, therefore making it difficult to see consistent gains.

 

This is exactly the info I was looking for to determine why I had 2 very different dyno charts on different days. The fact that a dyno should correct for environmental temp and humidity does nothing to prevent the engine from running different maps when the outside temps are extreme.
I had almost 20hp difference between my dyno runs, one on a 100F day, the other on a 55F day.
I will say that I did also see a 4-5 hp gain on the 55F day, after I had disconnected the battery to 'reset' the ECU. I assume this action causes the ECU to delete learned behavior for fuel economy purposes?

 

I would venture to say that just about any car will see dramatic differences in dyno results between a 100deg. day and a 55deg. day!! That's huge! No surprises there. The real trick with the K20 ecu is that it likes to jump from map to map with like a 1 or 2 degree temp change. That's tough on a dyno because the longer your car sits there, the hotter it will get...and you'll heat soak everything under the hood even with the hood open and a fan on it. Your best bet is to use a laser pyrometer and take readings at specified points around the engine bay (intake filter, intake tube, tb, intake manifold, block, exhaust manifold/header, cat pipe, etc.) for each run to help see why runs may not be quite so similar.

As far as disconnecting the battery. It makes sense to do it after installing power mods, but not on the dyno really. Unless you want to skew the dyno into giving you a raw max power number just for the sake of getting the dyno to read higher, in reality you wont be resetting the ecu while driving around town, so that 4-5 hp gained after resetting the ecu doesn't really exist once the ecu relearns fuel settings and integrates more fuel economy back into its program.