I have a VTEC AFC unit for my integra. I was thinking about dropping the VTEC engage point down to 4500 RPM instead of the 5800. I know this will use more gas but I don't usually drive it in the high rpm's anyway. Would there be any problems that you can anticipate by doing this?

 

with you doing that does it move the whole powerband around or does it just make it engage sooner??

 

vtec for a gsr is 4400 if i am not mistaken and the secondary butterflys open at 5800..

 

I couldn't honestly tell you...... My AFC was set to 5800 before so I know it was engaging then, not at 4400. I don't like this 5 post limit. It makes things difficult.


Modified by microsoft_sux at 9:02 PM 8/21/2004

 

well i could so setting ur vtec to kick in at 4500 would make it kick in later then earlier if thats what u were going for

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by neo1z &raquo;</TD></TR><TR><TD CLASS="quote">
4400 - Vtec
5750 (according to Helms) - Secondary Butterflies (NOT VTEC, not a second stage of VTEC, nothing like that)</TD></TR></TABLE>

 

your car will fall on its face if you set vtec for that low... the powerband isnt that low so you will lose power until you hit your powerband

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by microsoft_sux &raquo;</TD></TR><TR><TD CLASS="quote">I couldn't honestly tell you...... My AFC was set to 5800 before so I know it was engaging then, not at 4400. I don't like this 5 post limit. It makes things difficult.


Modified by microsoft_sux at 9:02 PM 8/21/2004</TD></TR></TABLE>

it engauges at 4500rpm. the secondary butterflies at 5800...

or so i notice when i drive

 

The stock gsr vtec engagement is at 4400 rpm, the secondary butterflies open up at 5750 rpm, thats why most people confuse the secondaries with vtec. Your vafc settings should be like this: L-H:4400, H-L: 4000!! Dont mess with it anymore, let your tuner do that for you. Your secondaries are still gonna open up at 5750, but if you set your vtec at 5800 you will lose a lot of your midrange. I had a vafc before i got hondata, and the best setting is vtec at 4400, trust me i tried a lot of settings, but the stock one is the best until you do internal work and get it tuned.

 

I wouldnt drop you vtec any lower than 5300 since your stock cams dont make any power until 5700 rpm or so..... just my opinion.

 

since im getting so much mixed feedback im just gonna put it back where it was. thanks anyway.

 

dont listen to people like this

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by iH8RICERZ &raquo;</TD></TR><TR><TD CLASS="quote">I wouldnt drop you vtec any lower than 5300 since your stock cams dont make any power until 5700 rpm or so..... just my opinion.</TD></TR></TABLE>

he is wrong. vtec does not engage at 5700 its 5750 and thats not vtec thats secondary butterflys

look at it like this u set ur vtec to kick in at 4500 right? normaly vtec kicks in at 4400 so u are making it kick in later then normal so what are u trying to do?

 

Unless your engine is heavily modified, I would leave the crossover at stock (apparently 4400 rpm for the B18c1). The stock crossover is set to where the low rpm cam profile power curve and the high rpm cam profile power curve overlap.

We-Todd is down, so here is a horrible ascii graphic to illustrate what I mean.

.............<FONT COLOR="blue">/\</FONT>....
............<FONT COLOR="blue">/</FONT>..<FONT COLOR="blue">\</FONT>...
.....<FONT COLOR="red">/\</FONT>...<FONT COLOR="blue">/</FONT>.....<FONT COLOR="blue">\</FONT>..
....<FONT COLOR="red">/</FONT>..<FONT COLOR="red">\</FONT><FONT COLOR="blue">/</FONT>..........
...<FONT COLOR="red">/</FONT>...<FONT COLOR="blue">/</FONT><FONT COLOR="red">\</FONT>..........
..<FONT COLOR="red">/</FONT>...<FONT COLOR="blue">/</FONT>............
.<FONT COLOR="red">/</FONT>.................
........*.........

The red curve is your low rpm cam profile, while the blue curve is your high rpm cam profile. The * is your crossover point. You can see that changing the crossover point will only cause a loss of power.

If your engine is heavily modified though, the curves may be shifted around. In that case, the thing to do would be to set the crossover super high (so you stay on the low rpm lobes) and dyno the car. Then set the crossover super low (so you stay on the high rpm lobes) and dyno the car again. Then superimpose the curves and see where they overlap.

Overlap rpm=optimum VTEC crossover.

...Hope that explains why some people move their crossover points.


Modified by OBD1Kenobe at 5:47 AM 8/23/2004

 

We really need to know more about your car before knowing if setting VTEC lower will screw things up. If it's a GS-R with the stock IM, then VTEC engages at 4400 RPM like everyone else has said. If it's coming on at 5800 and you aren't confusing those with the secondaries, then you're losing a lot of your powerband.

If you've got a single-stage IM like the Skunk2 or AN-R unit, then from personal experience, you don't want VTEC engaging at 4400. I had a really shitty powerband that spiked from 5K-6K RPMs and dropped off hard after that. It was so hard I could actually feel it. Yeah *** dynos don't mean anything, but it was definitely something anyone could feel. 5300 would be a nice place to have your VTEC set at. Probably not the best place, but it's better than it being at 4500.

 

THE VAFC'S STOCK SETTINGS PUT THE VTEC POINT AT 5800 ON A GSR

this is wrong, and it should be 4400. it did the same on my car.

 

so if the gsr engagement point is 4400 then what is the b16s??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by aznballer &raquo;</TD></TR><TR><TD CLASS="quote">so if the gsr engagement point is 4400 then what is the b16s??</TD></TR></TABLE>

Somewhere up above 5000, as is the ITR, since they both have single-stage intake manifolds.

 

ok thanx 4 clearing that up