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single/dual stage vtec

4K views 15 replies 8 participants last post by  MichaelDelaney 
#1 ·
what are some of your personal opions on single and dual stage vtec. Is it better to have two kick in at 4400 nd 6800, or is better to have one pull really had half way. I've read that havin your vtec kick in at 5200 is better. Also does the vafc controll a single or dual stage vtec, and where does it kick in?
 
#7 ·
#8 ·
When you get you engine package complete and tuned you will want to adjust your VTEC engagement point to make the best of both HP curves.
To better understand this concept, read up on What is a powerband? from the common topics.
 
#12 ·
yes but stuill why do some companies try to say that vtec engages at 4400rpm or is that just the butterflies opening up? because i went on ebay the other day and looked at a skunk2 chipped computer and it said this: "SINGLE STAGE VTEC ENGAGEMENT@ 5700rpm's (VTEC PULLS VERY HARD)" ... that was off a jun computer?
 
#13 ·
on a GS-R, the VTEC crossover is 4400rpm. The secondary intake runners open at 5700rpm.

on an ITR, the VTEC crossover is higher, at 5700rpm. It does not have a secondary intake runner in the intake manifold.

(these are stock points; aftermarket ECUs and control boxes can change VTEC crossover RPM points)
 
#16 ·
civicek9coupe on Feb/08/04 said:
what are some of your personal opions on single and dual stage vtec. Is it better to have two kick in at 4400 nd 6800, or is better to have one pull really had half way. I've read that havin your vtec kick in at 5200 is better. Also does the vafc controll a single or dual stage vtec, and where does it kick in?
obviously you don't know what you are talking about...

a gen 3 gsr has a 4400 VTEC switch and the secondary butterflies (not related to VTEC but to engine vacuum at the GSR's 2 stage IM IAB) open at 5800 rpm. the secondary runners on the GSR IM open up when the hi lobe VTEC cam has started to kick in and needs more air to breathe to make power. in nonVTEC the primary runners help make power at low to mid rpms but are too small at higher rpms and choke off the bigger VTEC lobe. the RSX has a 2 stage IM too but uses a roller valve instead of butterfly valves to open up the shorter bigger IM runners for better breathing at the top end rpm.

itr, gen 2 GSR, civic si have a different IM. They are single stage and don't have secondary runners or IM valves to open. So they don't have a 5800 rpm valve opening (NOT VTEC switch) like the GSR.


read the this article that I wrote (log in)

and this article here (if you can handle it...it may be over your head though).

you move the VTEC higher when you get bigger cams because their powerband is shifted up higher and you have a higher redline.

you place the VTEC switchover at an rpm where the nonVTEC lobes run out of steam.

I described that in the dyno tuning basics article (click) ...

you may want to start learning and reading from the COMMoN TOPICS and Articles and catch up to everyone else here.
 
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