Tuning questions

[seethrough]

Figured I would try to start a conversation that didn't involve all the drama and could maybe bring out some intelligent discussion. Anyway I have been studying up on tuning since it has always been that black magic part of the auto world that I wanted to understand more. A few books that I have are starting to shed some light on things but everyone's PCM acts a little differently so I am looking for answers on how the Viper PCM works. I don't have any immediate plans to make changes but would like to understand what is going on when the tuners that are out there are working their magic. So here goes - if you have an idea of how any of this works join in. Here are a couple of things that I am not sure about.

1. What inputs does the Viper PCM use to determine WOT? I am confident throttle position is one input that it looks at but does it look at other inputs like speed, engine load, MAP signal? And what is WOT when it comes to the throttle position? 70%, 80%, 100%?

2. Does the PCM go into open-loop when at WOT and ignore the O2 sensors for fuel trim adjustments and run solely on fuel tables?

3. Are the knock sensors limited to a certain frequency range of noise so that they can ignore common engine noise and only detect a knock? Will it matter if they are moved from the intake valley bosses to a different area of the intake valley?

4. Is the IAC opened during WOT periods to allow more air into the intake system?

5. Is the IAC used during deceleration?

 

[Slitherbeast]

I don't think we will get to much discussion on tuning the viper engine here. Very few options when it comes to tuning. CPU software was difficult to crack. the early vipers had a program called VEC that had a controller wired into the injector wiring and such so as to piggy back injector signal. I believe it was developed by ROE racing to allow their supercharger kits to work.

I have tried some tuning with the VEC II in my truck to some success but trusted the tunes I received from Torrie that came with the SCT.

 

[blazinsrt]

If you want to learn a lot about tuning go check out thirdgen.org those guys tune with burning chips still. As well as all kinds of aftermarket ECMs. To answer your WOT question though.

Most ECMs (unsure of the viper ecm though) use throttle position vs MAP and then do what is called acceleration enrichment and that is added to the fuel table by a percentage. I have a Holley EFI setup in my other car and play around with tuning it.

 

[VENOMOUS1 RACING]

Hope this helps

Figured I would try to start a conversation that didn't involve all the drama and could maybe bring out some intelligent discussion. Anyway I have been studying up on tuning since it has always been that black magic part of the auto world that I wanted to understand more. A few books that I have are starting to shed some light on things but everyone's PCM acts a little differently so I am looking for answers on how the Viper PCM works. I don't have any immediate plans to make changes but would like to understand what is going on when the tuners that are out there are working their magic. So here goes - if you have an idea of how any of this works join in. Here are a couple of things that I am not sure about.

1. What inputs does the Viper PCM use to determine WOT? I am confident throttle position is one input that it looks at but does it look at other inputs like speed, engine load, MAP signal? And what is WOT when it comes to the throttle position? 70%, 80%, 100%?
Yes TPS and often 75-80% is WOT and Map figures as well as the higher kpa reflects WOT cells
2. Does the PCM go into open-loop when at WOT and ignore the O2 sensors for fuel trim adjustments and run solely on fuel tables?
Yes it does. O2s are ignored on cold start and WOT.
3. Are the knock sensors limited to a certain frequency range of noise so that they can ignore common engine noise and only detect a knock? Will it matter if they are moved from the intake valley bosses to a different area of the intake valley?
They do rely on frequencies they're built to "hear"
They can be moved as long as in the valley. Older cars were on side of block and only one.

4. Is the IAC opened during WOT periods to allow more air into the intake system?
IAC is closed during WOT and and only opens during decel down to idle and during idle.
5. Is the IAC used during deceleration?

 

[seethrough]

Thanks guys. I have a follow up question. If under WOT the PCM ignores the input from the O2 sensor are there any other sensors it reads that affect the base fuel map under WOT. So basically does the PCM rely on the fuel table only and dump whatever fuel itdictates or does it have some modifying tables that get input from other sensors such as the MAP or TPS?

 

[blazinsrt]

It reads coolant temp as a modifier as well. So map, coolant and tps. Plus the acceleration enrichment percentage.