With the above mentioned controller, you can shift the vtec engagement point down the rev range and control the fueling accordingly. how does this get you more power earlier in the rev range. surely if it was that easy honda would have just set the engagement point lower anyway?

 

Im not really sure but from logical reasoning if you could lower the vtec engagement you will have a larger powerband instead of waiting till the normal factory vtec engagement. Im pretty sure honda could of lowered the vtec engagement point but that will decrease the life of the engine and affect the fuel consumption of the car.

 

i suppose what i'm querying is will the engine actaully produce the power further down the rev range if the high power cams are brought into use earlier, or will it not just run like a dog like cars with non vtec high lift cams used to.

 

Ive seen some people get about 10-15whp with a tuned v-afc but they are also running other mods such as intake,exhaust and headers. I hope this helps.

 

Lower has it right. For a road car you need a decent low end. Race cars need top end. You can't have both.

That is, until Honda developed VTEC. VTEC uses a conventional cam down low, but at a certain point changes to a high lift cam.

The way you work out the best point for changeover is you run the engine on low cam and plot the power curve. Then you run it on the high cam and and plot the power curve on the same line.

They will have different peaks. Find the point where the low can power is decaying and crosses the high cam curve as it's rising and you have your VTEC changeover point.

Lowing the point with out other tuning will lose you power. But add some effective mods and a bit of fuel tuning and you may find the intersection of the two curves shifts.

I have a bunch of mods. Primarily a Comptech SC. Extensive dyno tuning showed the best power was with VTEC changeover at 4400.

 

thats interesting that you found the optimum changeover point was lower down ther rev range. but then forced induction does change things somewhat.

has anyone done the same sort of testing with an NA engine to find out the optimum changeover point with fueling and induction mods only?

 

From the setups that I've observed, most people that are NA find that 5500-5700 RPM is optimal. That's not that big of a change, but it will give you a bit of extra torque at those RPMs.

 

this gets you more power by switching to the high-lift cam profile a bit earlier. in AusS2000's supercharged s2k, his switchover point is lower because he's taking in enough air at 4400rpm to make a lower switchover point beneficial. a lightly modded n/a app would only benefit from a switchover at 5500-5700rpm because that's when you're taking in enough air for the cam profile switch to make a difference in performance.

honda didn't just set it lower because this would lead to increased fuel consumption and it wouldn't work as well on a stock s2k.

 

I have mine set at 5500, with Intake, Exhaust w/test pipe.

 

I had mine set at 5600 with AEM intake and 4200 with Vortech.
Lowering it without any other mod will cause power loss. It may feels better in the butt dyno department because you get a dip in power before Vtec and then a sudden rush at 6 - 6.1krpm