- I've been wanting to experiment with dropping the vtech?
- I understand the concepts "VTEC window pressure" and "VTEC window rpm" on Hondata
- I've read the help files as well.
- What I'm not sure is if these are OR conditionals or AND conditionals.
- For example, If I always want vtech to engage @ 4000 rpm, can i set the upper and lower windows for 4000 or do I need to place values in the Vtech Window Pressure as well.

- In addition, from what I've read the best optimum (for most NA cars) ~ 3800; If I drop the vtech to this point. How will this affect longevity? From what i've been reading, when vtech oil pressure drops as well (and pressure usally indicates flow (but not always)...

 

I wish setting VTEC was as simple as typing some numbers in blocks on the laptop screen. There are also fuel settings and I don't recall what else but after looking at the software I decided to get a FlashPro tune by someone who knew what he was doing and wasn't experimenting.

There's enough information here to indicate to get VTEC to engage below 5000 rpm takes a high flow cat. I don't recall the reason, but there it is. The VTEC on my MY2006 car engages at 3600rpm under WOT. That's 3600rpm AND wide open throttle which is how VTEC works in a stock ECU except then it's 6000rpm AND wide open throttle. * My Gernby FlashPro tune was the result of scores of WOT pulls in 3d gear capturing data from a couple dozen special diagnostic calibrations.

I'm convinced there are no reliability concerns assuming that's what you mean by "longevity." The engine is actually rarely on the VTEC cam as even though it's often running higher than 3600rpm it's rarely at WOT. Cruising at 79mph (80mph speeding ticket here in Virginia is a felony offense) on the interstate the engine is at roughly 4000 rpm but still on the "economy cam" since the throttle is not fully open. At this speed, however, VTEC is right under my right foot. Exhaust note instantly changes and the increased power is felt as the cam changes. Where the 3600 VTEC shines is back road driving in 3d and 4th gears. And getting VTEC power at about 15mph rather then 30mph in 1st gear.

* WOT or some throttle setting or power demand. My eyes glazed over reading the documentation for FlashPro and I let the expert tuner set up my car.

-- Chuck

 

I cant speak to those specific settings as I just paid for an out of the box tune (Karcepts AP1 tune, which I highly recommend on an Ap1). But can attest to the fact that doing it without a HFC sucks pretty bad. huge power dip for a couple of thousand RPM that completely negates most of the benefit. But with the HFC it is nice. So do keep that in mind if you are testing and wonder why it performs so badly. And of course you want the rest of the tune to go with it. Mine engages at 70% throttle at 4000 rpm and regardless of throttle position at 6000 rpm.

You also will not notice or really feel VTEC coming in with it lowered like you do stock. It is just more of a linear increase vs more of an abrupt change. On mine the tq curve goes from about 125 ft*lbs just below 4000 RPM, then increases to about 133 ft*lbs as VTEC comes in, then drops slightly to around 131 ft*lbs between 4000 and 5500 rpm or so. After 5500 it increases to about 147 by around 6000 rpm where it stays relatively flat until around 8000 rpm where it starts to drop a bit towards redline. All numbers from an AP1.

 

VTEC Yo! only occurs with the 6000rpm VTEC because at that rpm the power increase is noticeable. Much more linear with the 3600rpm VTEC in my car. Of note, the car revs so quickly in 1st and 2d gears I installed a redline line audible alarm to keep off the rev limiter. Shift when the alarm screams. In higher gears it's beep.....beep.....beep. But in 1st and 2d it's beebeepbeeb like an old alarm clock.

I'm convinced Honda set VTEC where it is for the Yo! experience.

-- Chuck

 

My beloved AP1 will be tuned on AEM V2 soon as I finish up my SOS wiring kit install and the AEM wideband install. I'd like VTEC to engage at 4800 rpm + WOT or over 50 percent throttle (whichever the AEM ECU allows).

 

I don't see any disadvantage in a 3600rpm VTEC. Why 4800? Just curious, not a challenge.

-- Chuck

 

It entirely depends on your setup. You determine where it should be set by doing a dyno run with VTEC off, a run with VTEC on, and then place the transition point where the lines intersect. Anything else will make less power between where it should be set and where it is set.

 

Looks like nobody answered your actual question. It's an AND operation - so it must meet both conditions for it to kick in. The reason is because, without the pressure window, you could suddenly be entering VTEC while cruising on the highway at a low percentage of part throttle load. That's why there's a load threshold associated with VTEC (along with minimum coolant, minimum speed engagement, and disengage speed).

Here are some values you can use to start with and play around with if you have a test pipe. Note that I assume no responsibility if you mess things up. Also note that setting the Window Pressure RPM just slightly lower than the Lower point is also on purpose. I'll leave that as an exercise to the person learning how to tune why that's being done:

VTEC Window RPM Lower: 3600
VTEC Window RPM Higher: 5800
VTEC Window Pressure RPMs: 3400 4000 4500 6000 7200
VTEC Window Pressure MAP (bar): 0.940 0.920 0.800 0.500 0.300

Since you're reading the Hondata documentation, you should understand how to set your VTEC crossover at the optimal point. Hondata explains this very clearly in their documentation, so you'll obviously want to adjust this aforementioned data accordingly.

And having VTEC engage lower will not harm your motor so long as you aren't engaging it super low (around 2000 RPMs, for example). However, once you adjust your VTEC lower like this, you'll need to start tuning your fuel, timing, etc.

 

Because I run a full race J's Racing titanium exhaust...
Just kidding (not about the exhaust, I do run one) lol. Based on my cruising RPM on the highways mainly. Annnd...perhaps I want to preserve some sort of kick, yo
Come to think of it why not dissect the huge AP1 9000 rpm window right down the middle which leaves you with 4500 rpm VTEC engagement...

I assume at that low engagement of 3600 rpm you feel a strong surge as opposed to a kick, yo?

 

I'll be road tuning in real time. No dyno time available. I'm getting a remote tune done by AP1 Chief.