Liemoanh

I know that people lower the vtec point to get in the powerband earlier, but is there any downsides to this?

I currently running a SC S2000 and wanted to lower the vtec point to 5,000 rpms.
What will this do to my power band up top?My peak rwhp is 286 at 8,900 rpms. Will my peak numbers now peak at 7,900 rpms? My dyno shows that I build constant hp all the way until I hit redline. Will I build more peak hp if I shift the vtec point which in turns shifts the powerband? What is the lowest rpms you can set the vtec at and why?

mikegarrison

Unless you made any other changes, it shouldn't have any effect on the top of the power band. Nothing will have changed up there.

However, I would assume for a stock F20C that a lower Vtec power point hurts the performance at RPMs less that 6000 (or else why would Honda have two stages in the first place)? For an SC F20C, who knows?

Liemoanh

May I ask how you came to this conclusion?

So regardless, setting the Vtec point at a certain rpm other than 6,000 rpms would not be beneficial to the optimum performance that the stock F20C delivers (I assume).

If I set my Vtec at 7,000 rpms, would I improve the low end?

If I set my Vtec at 3,000 rpms, what would the dyno graph show me? If peak rwhp is unchanged, will my dyno graph show me a more flatter line from 3,000-9,000 as opposed to 6,000-9,000 rpms?

For instance, stock A vs stock B

Stock A=Vtec 3,000 rpms

Stock B=Vtec 6,000 rpms

Who would win in a quarter-mile?

Thanks for you input Mike.

Chadwick

It is my understanding that boost w/ a supercharger is applied most noticeably in the higher RPM range, basically after the VTEC transition

I can't see how it'd actually increase the amount of the boost the car is running. Properly tuning it, though, I can see an increase in efficency or better maximazation of available boost.

I'd say put it on a dyno and try it. What do you have to lose?

mikegarrison

That's true of a turbocharger. For an SC, it's a design choice whether it is optimized for low RPM torque or high RPM power.

mikegarrison

Because you haven't changed anything at high RPMs! There are two sets of cams. One operates at high RPMS, and one operates at low RPMs. The only thing you would have changed is where they switch over, not how they operate.

Hyper-X

I haven't the slightest about the benefits for FI setups, however...

Altering the VTEC x-over point usually ends up smoothing the midrange area and may make the kick less noticeable.

The problem I see is that while VTEC may engage below 6000 rpms, the ECU is still on the low cam maps and won't provide the same maps as you would in VTEC at/above 6000 rpms.

Sideways

We lowered mine about 800rpm and with the supercharger it pulls fine. Others have not had such good results. I suggest you do it on a dyno and you can compare your engine with the Vtec point set in more than one spot. This will give you the best results.

Having a Vtec power band of several thousand rpm is nice.

MattG

Somebody correct me if I'm wrong, but from what I understand not only is there a change in cam profile, but there are an associated fuel/ignition timing mappings which swap over at the same point.

You can change the point at which the cam profile changes, but from what I have read the fuel/timing mappings will remain at stock levels(?)

As posted earlier, test the changes on the dyno where results can be measured.

redlineracing

I'd like to lower my stock 03 to about 5800.

How is it done?


Thanks

\rlr