Without dynoing since i don't have the money, I'm trying to guestimate where i'd want to set my vtec point. it's currently at 4500. not sure if that's too early. I'm running b16 head, gsr cams, ITR IM, 62mm tb, .25 over ITR pistons LS block, 12:1c/r milled and decked with a decent flowing 2.25 exaust


Modified by VtecDA9 at 12:44 AM 11/4/2003

 

Usually 4500 is a bit too early. Try to consider what the mods have done to your torque curve and remember that vtec is used to enhance that torque curve at high rpms. If 4500 is before where your torque peaks without vtec then I would raise it. If 4500 is after the point of peak torque then I would leave it.

 

Hmmm, I'm guessing my torque curveis up a lil with the ls/vtec setup as opposed to the straight LS and that it would be over 4500, is that ur guess? I'm thinking 4900-5300 rpm now...

 

with your setup i'd say something closer to 5500rpm would suffice.

 

Well what would happen in terms of power if my vtec engaged too early or too late... I pretty much shift at 4000 when driving around the street.

 

Why GSR cams?

 

5000 - 5500 would be a good place.
You don't want to hit it all the time while just commuting around town, at least not if you want to keep halfway decent gas mileage.

My $0.02.

 

gsr cams because I wanted to spend my money in other areas during the rebuild, but now it looks like i'll be running these cams for a while till I get the lil things out the way, then I'll get bigger cams and jump on the dyno to tune them with hondata etc...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by VtecDA9 &raquo;</TD></TR><TR><TD CLASS="quote">Well what would happen in terms of power if my vtec engaged too early or too late... I pretty much shift at 4000 when driving around the street. </TD></TR></TABLE> vtec is not, like, pushing a magic nos button. it is the point where you are switching cam profiles from being clark kent to batman - you should be very close to a normal gsr cutover point.

 

5200-5500, play around with it and see what works the best for you

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RS_H22 &raquo;</TD></TR><TR><TD CLASS="quote">5200-5500, play around with it and see what works the best for you</TD></TR></TABLE>

Agreed.

 

Also, if the vtec engages too early, you expose your engine to longer duration and high overlap at low rpms. This could cause some air to pulsate back into the intake manifold, and the reuse of some exhaust gas. This will hurt horsepower numbers and can put a serious and unnecessary strain on the engine. I know a guy who set his vtec to come on at 3000 rpms, his engine smoked really bad when he did it, and even after he raised it back up, the engine has never been the same. Just be careful.