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Discussion Starter #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?
 

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Are you referring to the dual stage intake manifold on a GSR, where the cams switch to high lobes at one RPM and the secondary butterflies on the intake manifold open at a different RPM point? Is that what you are reffering to by dual stage VTEC.
 

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Must be talking about the GS-R! I dont see it making that much of a diference eccept for the torque curve. Although i do like my friends type-r but that's probably just the fact that it's an R.
 

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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.
 

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Discussion Starter #9
then why do some aftermarket ecu's (computers) like skunk2,jun,spoon, ect.. say that there single stage vtec kicks in at 4400rpm and and my gsr with the vafc was dynoed with the vafc at 5200rpm?
 

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It's single stage/runner INTAKE MANIFOLD, NOT VTEC. Changing VTEC with a VAFC will override what's in the ECU.

Oh and about the GS-R intake manifold, it's possible to change and "tune" the secondaries to your liking.
 

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Discussion Starter #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 [email protected] 5700rpm's (VTEC PULLS VERY HARD)" ... that was off a jun computer?
 

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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)
 

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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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