Zerostatic

Theoretically when VTEC engages, you shouldn't feel it. It should switch at the exact moment when more power is produced using the high-end profile instead of the low-end profile.

So, when people put I/H/E on their cars and they can "feel" the VTEC now, doesn't that mean that now due to these mods, the VTEC point should be lowered again to the point where you hardly notice when it engages. Because if VTEC feels like a big rush of power all of a sudden aren't you losing out on power right before the VTEC engagement point.

wilp99

u sound like negrodaumos....

white3.0

at 4k RPM

97Acura3.0CL

not for teh 3.0

this is going to get going bad real quick

when i got my vafc my settings stock that the vafc read form the ECU was 5300 engagement stock

but it is about high 4, low 5's in the rpm range for the 3.0 i cant tell anymore with the vafc on and mine is now set at 3800

white3.0

VAFC says my friends Civic SI is a low 14 sec car

Mike 350Z

I don't think you guys understand the question at hand. He's saying should the engagement pt. be changed so it's a seamless transition. I for myself have no idea, but i understand what he's asking.

CLpower

No, basically when vtec engages it is changing cam lobes.

even on stock cars you can feel vtec engage. It's never really a smooth transition, esp. on DOHC motors. you really feel it on a type R. You feel it more on a modded one.

Dan3952

4200 rpm

My VTEC temporarily disabled itself due to me running the car at a ridiculously low oil level and this was where my redline was temporarily. Because the system didn't have enough oil to engage properly I also had a rougher than normal engagement that I felt between 4500-5000 K. These two things didn't happen at the same point in time

LCARUCA 97

i can feel it

azian21485

you won't know where to set vtec engagement with vafc or vtec controller unless you bring it to a dyno..butt dyno isn't accurate

Zerostatic

would a good way of figuring out the approximate VTEC point be to set the VTEC really low like (2,500 rpm) and dyno, and then set it really high (4,500 rpm) and dyno. Then if you cross reference the two dyno's and figure exactly where does the high end profile starts making more power then the low end profile.

ghost_masterCL

^^^ that sounds about right. I think that makes more sense. but keep in mind hte high ned might make more at a certain rpm than the lower, but drop below what the lower would produce abve that rpm, so it would be better to set it at a certain point so as to MAXIMIZE average torque.

azian21485

i'd just set it at like 7k if you can so it doesn't engage at all

here's a quick pic someone drew that i grabbed off an accord forum

wilp99

what the hell...............talkin bout a bootleg ass graph.

azian21485

someone DREW it..it's only used to make the point across but i guess it didn't cus some people wanna see the real thing huh

wilp99

i mean theres no rpm's, fuel ratio, nothin.

ib_jimmy

hahaha where u get that graphic mang! it doesnt answer what the question is asking but a perfect graphic to show how VTEC work.

GoldieAlek

ghost_masterCL

ok here. lets answer the question.

Yes. the VTEC engagement point should be right there at the ideal location. however sometimes it's not, BUT when it is, you'll also notice that the slope of the graph increases considerably at the ideal engagement point. It's not so much the Sudden jump in power that's doing it. It's the increase of power/rpm. You gai power much faster in the VTEC than in the lower cam lobes, and thus feels like a "boost" when it engages.

azian21485

sorry i thought people would assume it was the typical dyno chart

x-axis = rpm
y-axis = horsepower

yes there's no torque curve but it doesn't matter it'll be pretty much the same concept

i just posted the graph because someone was talking about overlapping a dyno chart while having vtec engaged at a lower rpm (red line if you want) and then vtec with vtec never engaged (blue line) so if you cross reference (not sure if that is the term but seems to fit here lol) you'll know where to set your vtec

zerostatic's answer was already posted.

you can't just say "lower the vtec as you put on more mods" because different companies, parts, blahblahblah make power at different points along the rpm range..that's why you need to dyno you're car get it tuned, then look at the curves

he was correct that setting it too late you'd feel a big power surge because if you look at the "late crossover" portion of the graph, if you were to switch lobes at that point (yellow vertical line) you'd be jumping into a higher power range right away and therefore "feel it" and think you're going faster rather than a smooth delivery