Vtec vs i-Vtec


ManosEK9

ManosEK9

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Does anyone knows how i-vtec operates?
what are the differences between the two?
what are the power gains from the use of i-vtec compared to vtec?? Are there any actuall gains or is just a tiny step forward for Honda technology used alot mainly for marketing purposes?? Thanks in advance.
 
ManosEK9 said:
Does anyone knows how i-vtec operates?
what are the differences between the two?
what are the power gains from the use of i-vtec compared to vtec?? Are there any actuall gains or is just a tiny step forward for Honda technology used alot mainly for marketing purposes?? Thanks in advance.
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The i-Vtec has alot more top end power when in vtec than the older vtec models. this is due to both the exhaust and intake cams having variable valve timing as in the older vtech engines only the intake cam had variable valve timing
 
i think i-vtec engine on EP3 cuts @ lower r.p.m as stock...anybody?

however, engine on ep3 produces more torque it being a 2L lump.
 
i think we all know what vtec does? primary cam lobe and vtec cam lobe, when vtec crosses over the bigger cam lobe is activated which increases lift and duration.

i-vtec is similar to vtec but adds one more feature, "cam phasing" this is on the exhuast side and is like having an electronic adjustable camgear that is adjusted by the ecu +-50degrees.

hope this helps. you can check youtube for videos that explain it as well so you can visialize it.
 
So in general, vtec affects only the operation of the intake cam whereas i-vtec affects both cams, right? And with i-vtec, the intake cam works in the same way as with vtec but the exhaust cam works in an intelligent way(i-vtec)?? I hope i-vtec is not clever enough to cheat and have a break when it gets tired :confused:
 
No offense but the explanation by vtech would be completely inaccurate.

VTEC already affect both cams, i-VTEC just gives them an additional feature.

VTEC operates by switching the cam profile to a completely different profile.
I-VTEC operates on the same profile (chosen by VTEC), but allows the cam phases to advance or retard via an actuator. Picture an automated, variable adjustable cam pulley. Such a feature allows the engine to have variable valve overlaps, but work on a constant lift duration as long as the cam profiles doesnt switch.

Given that VTEC may operate on 3 different cam profiles, the effects of cam phasing (i-VTEC) on VTEC is relatively minimal, as the primary VTEC profile may already adjust valve phases to suit its rpm application. A normal engine however would greatly benefit from having cam phasing, such as Toyota's VVTi.

I would think that i-VTEC is designed mainly to improve smoothness, linear power delivery and engine efficiency, not to create more raw top end power (as this depends primarily on on the cam profile). It is a remarkable improvement nonetheless.

And for an additional note: The camphases generally shift from advanced @ low rpms -> retarded @ mid rpms -> advanced @ high rpms.


edit: well, im basically saying the same thing as blinx but I hope it helps to improve the picture. :)
 
thank you JayH, i agree with you 100% about the cam phasing and its purpose.

i know her in CA emissions are tight and i-vtec motors have excellent emissions ratings becuase at idle there is almost no emssions thanks to the cam phasing.

and to Manos, vtec is on both cams, cam phasing is on one cam :nice:
 
VTEC that only happens on the intake cam is SOHC only, Dseries motors, D15s/16s etc
 
nooooo. meant on the inlet valves only, as there is only one cam it can only manage one side properly it does inlet side only
 
charlay said:
nooooo. meant on the inlet valves only, as there is only one cam it can only manage one side properly it does inlet side only
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if you are referring to soch engines then yes you are correct, twin cam engines use vtec on both intake and exhuast side.
 
blinx9900 said:
if you are referring to soch engines then yes you are correct, twin cam engines use vtec on both intake and exhuast side.
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Your probally correct where I got the info it did not state if the vtech engine they were talking about was DOHC or SOHC :angry2:
 
I would think that i-vtec creates more power and torque in the lower rpms as well as it's efficiency.
 
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