VEC II ?
- Thread starter pullshard
- Start date
I think the O2 sensors are still functioning normally, but the VEC2 doesn't change anything based on them. As I understand it the VEC2 can make changes to the base maps by advancing/retarding timing, adding/removing fuel, etc., but the factory PCM's adaptives using the various sensors are still fully functional.
HMMM. I still do not understand how it works (VEC Noob). You install the vec II (piggy back, but how much?). You place a card in the vec II. The pcm takes that info and "learns" what is on the card and tries to adapt to it. I understand that the pcm still functions. What confuses me is that if the VECII is telling the pcm what to do fuel and timing wise, would it not have to bypass the O2 to get this done. At idle the O2's tell the pcm if the car is lean or rich. The pcm then takes this info and makes adjustments. If to rich or to lean for a certain amount of time it throws a code. So if the VEC II is now in place, doesn't the PCM just take the VEC info and go by that making the 02's useless??? Am I making any sense at all? Now at WOT the system goes into close loop mode, which I'm pretty sure at this point it uses no info from the O2 at all. So at WOT the VECII is now in full control or is the PCM still in the mix???
Me needs to understand.
Me needs to understand.
PhoenixGTS
Enthusiast
I am no VECII expert, but in general, what piggy-back computers do is alter signals from various sensors in order to trick the stock computer into doing what you want. For example it would alther the oxygent sensor voltage in order to trick the stock computer into adjusting the fuel mixture in closed loop differently than it would without the piggy-back. And might trick the crank positioning or cam position sensor in order to affect timing. It might use an absolute manifold pressure sensor adjustment to effect open-loop air fuel. So you still have to have sensors working.
1TONY1
Enthusiast
The vec2 looks at what the factory pcm wants....then alters the signals (adds or subtracts fuel/timing) The front 02's are still doing their normal job.
IEATVETS
Enthusiast
If in doubt call the man.........Sean Roe. But these guys are pretty smart also.
KenH
Enthusiast
Keep in mind that the VEC2 is only used at WOT when the car is generally running off preset maps rather than when it is monitoring the O2 sensors like it does when idling around town. It works by intercepting key signals like the MAP and crank position and modifying them before passing them on to their destination. It also includes its own fuel injector drivers. Everything is referenced off the stock settings rather than creating them from scratch.
If you haven't seen it, Sean has his operating instruction posted on the web which give a pretty good idea of how the system works.
http://kansascityvca.com/roe/
If you haven't seen it, Sean has his operating instruction posted on the web which give a pretty good idea of how the system works.
http://kansascityvca.com/roe/
1TONY1
Enthusiast
That is incorrect.
KenH
Enthusiast
How about 'keep in mind that though the VEC2 is always in-line, it is generally only programmed to affect settings during WOT operation'?
Larry94
Enthusiast
Correct me if I'm wrong, but I believe the stock PCM controls the fuel and spark advance through an open loop system up to around 80% of WOT. It will "adapt" based on various outside parameters. Beyond 80% the fuel and spark advance are controlled by a closed loop system using fixed pre-set factory maps. The vec II controls ignition and spark advance based on manifold pressure and/or RPM. If you adjust the injector pulse width and/or ignition based on RPM but only have them take effect at a manifold pressure at or near zero, then, in effect, they will only occur at WOT. However, adjustments at negative pressures (i.e. vacuum) or positve pressures (i.e. boost) are also possible.
1TONY1
Enthusiast
What Jack said.
1TONY1
Enthusiast
You have your open and closed loop backwards......but your explanation is correct. The vec2 can control anywhere in the rpm range and in vacuum or boost. The main thing it does in vacuum is make the larger injectors (s/c application) act like stock.
VIPER D
Viper Owner
It also can retard/advance timing under boost and nos use, turn on and off the nos system and I have modded mine to even act as a shift light.
vd..
vd..
Is anyone using a VEC II on a paxton Car? If so, do you have any VEC II maps that you have worked on that you could email so I can look at. I would love to see how they compare to what my tuner did. I'm hooking up a wideband in the next couple of weeks and want to see which card I have works best. And then once I understand the system more, I want to start to play with the settings and see what they do a\f wise. I'm not really interested in max power (yeah right) I just want to drive a paxton car and feel good about it. I think some paxton car owners know what I'm talking about.
Thanks.
P.S. Car is a 2000 gts with stock injectors, no split second. walbro 255 pump, tnt headers....
Thanks.
P.S. Car is a 2000 gts with stock injectors, no split second. walbro 255 pump, tnt headers....
the comparison from what others have done would be interesting to see, but your car is gonna react differently and is going to need its own unique tuning.
Do you know where your tuner set your a/f?
Take some time once you get your wideband and create your own cards that work well on your car. The a/f is easily manipulated and is not difficult to get were you want it.
Others cards could give you an idea of where to start or where you can go, but once you get to playing with the system you want care much what others have done.
Good luck
John
Do you know where your tuner set your a/f?
Take some time once you get your wideband and create your own cards that work well on your car. The a/f is easily manipulated and is not difficult to get were you want it.
Others cards could give you an idea of where to start or where you can go, but once you get to playing with the system you want care much what others have done.
Good luck
John
Ted B
Enthusiast
VIPER D...
Can you please give a little more info on what you had to do for your NOS control and shift light? I haven't read ALL the documentation yet, so if it's in there feel free to give me the big "RTFM".
There's no output terminals (i was expecting screws or something) so did you have to add a few new pins to the harness? Does the VEC2 software have a section for setting these option or did you have to "hack" something?
I've really only messed with pulse widths so far.
Thanks
Can you please give a little more info on what you had to do for your NOS control and shift light? I haven't read ALL the documentation yet, so if it's in there feel free to give me the big "RTFM".
There's no output terminals (i was expecting screws or something) so did you have to add a few new pins to the harness? Does the VEC2 software have a section for setting these option or did you have to "hack" something?
I've really only messed with pulse widths so far.
Thanks
VIPER D
Viper Owner
Bill M can give better details since him and his shop (VOS) did all the work. I just own and drive the monster. I will drop him an email to respond to this.
vd..
vd..
1TONY1
Enthusiast
You should have one six inch unused wire coming from the connector at the back of the Vec2, it may be taped up/over. That would be the output. I'm not sure if that is the only way to turn on a shift light, but it will work for that. It will not, say.....do nitrous and a shift light. It is a ground output that would be used to turn on a relay for anything. Can be based on rpm or boost or both.
1TONY1
Enthusiast
Can they be told different to use different rpm's/boost etc ?
VIPER D
Viper Owner
there is a shift light right on the vec2 box that can be set with the new bin file. I tapped the the out put and am using it to turn on and off my nos and for the shift light at the same time.
vd..
vd..
"there is a shift light right on the vec2 box that can be set with the new bin file. I tapped the the out put and am using it to turn on and off my nos and for the shift light at the same time."
Be more specific, I am looking at the VEC2 manual and output schematic. There are PWM contacts out on the slave and master, however they are both linked by the same control function. There is no way to get contact closure at two different load/rpm targets.
If you have the VEC turning on the NOS and also a shift lite where do you set it up and which pin-outs are you using?
Be more specific, I am looking at the VEC2 manual and output schematic. There are PWM contacts out on the slave and master, however they are both linked by the same control function. There is no way to get contact closure at two different load/rpm targets.
If you have the VEC turning on the NOS and also a shift lite where do you set it up and which pin-outs are you using?
Hi. We installed the shift light and vec 2 in Viper D's car. We used the PWM Load and PWM RPM to fire his NOS/Propane between 3000-5000RPM. The shift light in the cabin we triggered by using LED 2 on the VEC 2 itself, which is controlled by the Box Configuration.
KenH
Enthusiast
So is there some way to tap into the LED #2 light on the VEC2 box to drive the shift light? As it doesn't seen to have an output on the I/O harness.
VIPER D
Viper Owner
dats right......
And the best thing is that each card has its own shift point. Ie nos 5000 rps, all motor 5600 rps.
kinda dummy proof light goes on shift.
vd..
