How-to: VTEC Window and how to use it.

Hello guys, I noticed not many people know how to set the VTEC window in Kpro, or understand how it even works. We just set it to where we want to and go with it. So here's a lil guide on how it works. It's easy!

Here is our Parameters window and Table. The VTEC window settings use Kpa to determine where to set the threshold, so I changed the way the table displays to coincide with the settings.
http://i.imgur.com/UTfjHss.png
Basicallly, if you didn't already know, the Kpro ecu uses the Speed-Density method to determine how much air is flowing through the intake manifold, and the O2 sensor is used in closed loop mode to correct it. This means the computer is guessing at how much air is going into the cylinders and all it's using Manifold Absolute Pressure (MAP sensor!) to determine where on the fuel table it is at, and that dictates how much fuel is going in the engine.

What that means right now is the Kpa numbers are just a measurement of vacuum/boost, and for the purpose of this instructional, that's all we need to know. The higher the Kpa, the higher the pressure is in the manifold, ie, the harder you step on the gas, the higher the manifold pressure (from absolute vacuum, to atmospheric for NA guys).

So, notice the first threshold settings, 3800 RPMs and 96 Kpa, lets draw a line on the table to demonstrate how this works...
http://i.imgur.com/KlPnCZ9.png
Pretty simple right? What this means is any pressure above 96 Kpa (pretty much WOT) AND above 3800 RPMs will put you in VTEC.

Now lets look at the second settings, 5500 RPMs and 30 Kpa. Lets draw more lines.
http://i.imgur.com/wYNVOhf.png
Well look at that, a WINDOW!
What this means is at 30 Kpa, which is with almost the throttle closed, and over 5500rpms, you will be in VTEC, this is your partial throttle VTEC setting.

So we made this nice lil window right? Lets draw another line that connects those 2 thresholds...
http://i.imgur.com/Gac7BQL.png
This line represents the variable VTEC threshold that could occur anywhere between those 2 settings. If you were able to see the tracer on Kmanager move through the Kpa and RPMs, as soo as it crossed that line you would be in VTEC. What this means is if you were cruising at about 4200 RPMs, you would not be in VTEC, but as soon as you stepped on it and the manifold pressure crossed that line, you would get VTEC.

So lets clean up this table and show you where you would, and would not be, in VTEC.
http://i.imgur.com/vkeIq3N.png
This is how the ECU determines when you cross into VTEC, lower boundary is always where WOT VTEC occurs, and upper is where it would be if you were just partial throttling through traffic or something.

In the tuning world, you would set the lower boundary where the low speed cam and the high speed cam (primary and vtec, respectively) cross in power on a Dyno. This setting can be different depending on how you built your engine. Honda typically sets VTEC a little higher so you can FEEL it, a sales gimmick to show you that the technology exists. Nothing more, nothing less. You wont feel a "kick" when you have a properly set VTEC threshold.

I know it now, just a little though. lols

NICE! I would love to see a series of HOW TO: for KPro tuning!

IMO its safer to push a tune to the edge if you use a switchpoint versus a window.

For my setup, i like knowing i can hit columns 7+ on the 'low cam' without relying on the 'hi cam' to make power round town. Since my 'lo cam' is partly on the big lobe, a window would defeat the purpose of using a flipped pin rocker setup (fuel economy). It will vary from build to build and the use of the setup.

I can see a window being advantageous for a bigger turbo setup (laggy) around town... more exhaust at lower RPM would help spool the turbo faster. Just thinking out loud...

Well since you're flipped pin, its easier to say you're not in vtec (low speed cam) and IN VTECCCCC (high speed cam). So if you want to throw dyno tuning out the window (but honestly with flipped pin, your tuned VTEC at WOT should be higher than most traditional vtec setups) you just move the RPM higher. I'll post up another OEM table...

http://i.imgur.com/w9BpeS5.png
This would probably be more what yours would look like, seeing that the TSX cam lobes, both high and low speed, are pretty aggressive.

If i used a k20a3 head i could see that... but the larger ports on the k24a1 head and compression bump seemed to make use of the extra air. I was even surprised how much ignition i was able to run on the 'lo cam' without knock.

People that ride in my car are surprised how linear the car feels, and often comment that there is no VTEC crossover feel (you sure you have VTEC?). Just one solid and increasingly strong pull all the way through the RPM range.

Ill get it on a dyno soon... just waiting on some coin to do so. Im curious of its output and TQ curve before the bigger exhaust.

You'll see it on the dyno, once you do the low cam and high cam over lap. Kinda tired right now but I'm not familiar with flipped pin performance on the dyno. Low end tq sounds better than you probably describe it since the offset valves cause the swirling fuel inside the cylinder. In my head it sounds like your non vtec tables will make good power for much of the rpms before your full vtec tables cross on the dyno, thus raising your lower boundary. Typically the more aggressive your primary lobe, the higher that lower boundary goes. Like tsx cams. If you compare z3 cams (let's assume the vtec lobes are the same) with their lower profile primaries, they should have a lower lower-boundary than a tune on the tsx cams, given its running the same engines.

Quote:

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Originally Posted by AKEP

You'll see it on the dyno, once you do the low cam and high cam over lap. Kinda tired right now but I'm not familiar with flipped pin performance on the dyno. Low end tq sounds better than you probably describe it since the offset valves cause the swirling fuel inside the cylinder. In my head it sounds like your non vtec tables will make good power for much of the rpms before your full vtec tables cross on the dyno, thus raising your lower boundary. Typically the more aggressive your primary lobe, the higher that lower boundary goes. Like tsx cams. If you compare z3 cams (let's assume the vtec lobes are the same) with their lower profile primaries, they should have a lower lower-boundary than a tune on the tsx cams, given its running the same engines.

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After reading this and the rest of the thread I understand why my friend's engine VTEC crossover is so low and why some engines have the crossover higher or lower.

Case in point:

He has a built K24 block using Wiseco's 12.5 CR pistons in a K24 but using a STOCK K20A2 with stock profile K20A2 cams. When he got his car tuned the VTEC crossover point had to be set at 3800 RPM because the car was choking when they were setting it around 5k area.

Compared to my car I have a stock K20Z3 bottom with Honda overbore pistons (86.25mm) and my built K20A2 with oversize 0.5mm intake valves and Crower (not Brian Crower) Stage 2 cam profiles (much mroe aggresive than stock) and my car was having bogging issues with the crossover set at 5200. The tuner finally settle the crossover at 5800 RPM and my powerband saw gains midrange BEFORE the crossover and my engagement was almost nonexistent (you couldn't see any type of bump where VTEC was engaging in the powerband graph).

Quote:

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Originally Posted by AKEP

You'll see it on the dyno, once you do the low cam and high cam over lap. Kinda tired right now but I'm not familiar with flipped pin performance on the dyno. Low end tq sounds better than you probably describe it since the offset valves cause the swirling fuel inside the cylinder.

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It does make noticeably better power part throttle (2500-4500, columns 5-7 and 8 when its cold out) than WOT on the lo cam. My xover is 4800 and i strive to shift at 4500 around town since 95% of my driving is on the lo cam. Its definitely a different beast. It even liked 40 degrees of advance on the small ass exhaust im using, which surprised me.

I need to go back and gradate the cam advance from idle to 2krpm. Its 0-5-10-20 to ease initial tuning and if im smooth on the throttle i can feel it change, since its climbing up that big lobe. I can imagine it would make life easier on the roller rockers if i did.

Ill mess with a window again once the 87x86 12.5cr block is done... ive gone too far down this road to start over. lol

good shiii tony k

:thumbu:

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