D
DAMN YANKEE
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"Closed Loop" operations in stock GEN2 Viper, just exactly what does that mean?
About 85 percent of all the driving will ever do in our vipers will be in closed loop, yet most Viper owners don't know it means. I thought I would take a second to get a very simple description on closed loop out there as its a great place to begin.
For many, I think they believe this subject is not approachable because it is too complicated or they don't have the skills to better understand their own cars. I felt that way until I supercharge my Viper and wanted to carry on the tradition of doing all the work myself even up to tuning the car. So let's get this out on the table right now, my supercharge Viper runs infinitely better than my stock Viper ever did. It's smoother, more responsive, much faster, more stable at all speeds and, most importantly, I know why. I am also an advocate of using the best Viper tech's I can find. From 2000 until 2006 I had to service my Viper myself, I simply did not know where I could take my car to get reliably and responsibly serviced. I met Chuck Tator, and Chuck now sees my car routinely. I'm not a master mechanic, Chuck is an I (and my car) know the difference. I also rely on Sean Roe for his consistent and skillful guidance. Having said that, make no mistake about it, when it comes to generating logs and reviewing, in a very detailed way, the specifics that drive the air/fuel and timing issues of my engine, I know as much as anyone as to were my car is at any given time. No, Chuck Tator does not tune might VEC, I do (along with help from Sean). My Viper does not burp, have weak spots in its power curves, weird idling, hesitations or slow transitions from vacuum to boost or back again. My car runs like a bear, so much better than when it was stock it's ridiculous. This take work, very little and I find it fun to do. I also need to make one last point, I simply don't care what engine management system you use, I'll give you my guidance from a VEC perspective because that's what I know. Stock vipers can be fundamentally improved by being able to work with the stock PCM using such systems.
Back to subject, a well running Viper is one that has precise tuning of the air to fuel ratio and ignition timing curves over the whole operational range of the engine. We begin with understanding one of the very basics of stock Viper engine. There are two major conditions that every stock Viper engine has, open loop and closed loop operations. And they are very different. Closed loop refers to a condition whereby your Viper's PCM is constantly monitoring the narrowband oxygen sensors located in your exhaust system along with a few other sensors like air temperature and cooling temperature. As you may be aware, each side of your engine (or bank) has its own exhaust pipe with a narrowband sensor located at the junction of the header and another narrowband sensor located behind the catalytic converter. When your engine is warmed up and your operating your engine with approximately less than 80 percent throttle, the PCM monitors the amount of oxygen and fuel and makes adaptive changes by increasing or decreasing the injector "pulse" automatically and spark curves. Increase the pulse, or in other words provide electrical current to the injector's for a longer duration, firing the injector's for more milliseconds, and you get more gas injected into the cylinder. Shorten the pulse, less milliseconds, less gas injected. This is where all you idle and cruising and normal acceleration efficiency work is.
We should think of closed loop operations as the time in which the engine is not being called upon to do its most powerful work. That does not mean that you're not accelerating, or even moving at highway speeds, that is not the case.... One can cruise at highway speeds for hours and never leave closed loop. In closed loop operations, we generally expect to throttle body's to be less than 80 percent open. In closed loop operations, we expect that the Viper is idling, gently accelerating, reasonably accelerating or cruising. All the while, the PCM is working to maximize the efficiency of your air fuel ratio. That ratio is most efficient at what is called "lambda". lambda is achieved when 14.7 lbs. of air is mixed with one pound fuel. The target, constantly being adjusted for engine load and other engine and driving conditions in the lambda is just that, 14.7. For those of us that want to see if in closed loop our cars are operating at lambda, we can. We do this by using the oxygen sensor that samples at a much higher rate and add a much more accurate rate and those found in stock Viper. Stock Viper's Oxygen sensors they are narrowband sensors, guys/gals that want to more accurate view their engine's ability to achieve lambda in closed the operations rely on gauges driven by wideband sensors. As load changes, so does the require A/F (Air Fuel) mix. It would be incorrect to assume that simply having a wideband sensor and wideband gauging your car is going to allow one to properly address all issues surrounding closed loop operations. We also need a high-quality software interface (program) to the ODB2 found in our GEN2 vipers. I have one, it plugs into the drivers left hand knee location of the OBD2 fitting under the dash. I can directly look into the PCM's operations, especially the adaptives and make sure they fall within a specified range of the stock PCM operating throughout closed loop. There is of course more on this subject, lots more, but there you have a very simplified begining, closed loop operations in a very summary fashion. I know what you are thinking....what happens in closed loop if I am running simms? Interesting question and one we will cover if anybody cares to.
I'm throwing this out here, to hopefully begin the process of helping others understand principal operations of the Viper and hopefully encourage others with much more knowledge than I have to step forward and share what they can. This is the tuning section, this is where interested minds can learn more. As to those that want to know what open loop operations are, I thought I would start a separate thread on that topic if there is interest here. if after awhile it becomes clear that nobody really cares about these subjects, trust me, I'll stop....
About 85 percent of all the driving will ever do in our vipers will be in closed loop, yet most Viper owners don't know it means. I thought I would take a second to get a very simple description on closed loop out there as its a great place to begin.
For many, I think they believe this subject is not approachable because it is too complicated or they don't have the skills to better understand their own cars. I felt that way until I supercharge my Viper and wanted to carry on the tradition of doing all the work myself even up to tuning the car. So let's get this out on the table right now, my supercharge Viper runs infinitely better than my stock Viper ever did. It's smoother, more responsive, much faster, more stable at all speeds and, most importantly, I know why. I am also an advocate of using the best Viper tech's I can find. From 2000 until 2006 I had to service my Viper myself, I simply did not know where I could take my car to get reliably and responsibly serviced. I met Chuck Tator, and Chuck now sees my car routinely. I'm not a master mechanic, Chuck is an I (and my car) know the difference. I also rely on Sean Roe for his consistent and skillful guidance. Having said that, make no mistake about it, when it comes to generating logs and reviewing, in a very detailed way, the specifics that drive the air/fuel and timing issues of my engine, I know as much as anyone as to were my car is at any given time. No, Chuck Tator does not tune might VEC, I do (along with help from Sean). My Viper does not burp, have weak spots in its power curves, weird idling, hesitations or slow transitions from vacuum to boost or back again. My car runs like a bear, so much better than when it was stock it's ridiculous. This take work, very little and I find it fun to do. I also need to make one last point, I simply don't care what engine management system you use, I'll give you my guidance from a VEC perspective because that's what I know. Stock vipers can be fundamentally improved by being able to work with the stock PCM using such systems.
Back to subject, a well running Viper is one that has precise tuning of the air to fuel ratio and ignition timing curves over the whole operational range of the engine. We begin with understanding one of the very basics of stock Viper engine. There are two major conditions that every stock Viper engine has, open loop and closed loop operations. And they are very different. Closed loop refers to a condition whereby your Viper's PCM is constantly monitoring the narrowband oxygen sensors located in your exhaust system along with a few other sensors like air temperature and cooling temperature. As you may be aware, each side of your engine (or bank) has its own exhaust pipe with a narrowband sensor located at the junction of the header and another narrowband sensor located behind the catalytic converter. When your engine is warmed up and your operating your engine with approximately less than 80 percent throttle, the PCM monitors the amount of oxygen and fuel and makes adaptive changes by increasing or decreasing the injector "pulse" automatically and spark curves. Increase the pulse, or in other words provide electrical current to the injector's for a longer duration, firing the injector's for more milliseconds, and you get more gas injected into the cylinder. Shorten the pulse, less milliseconds, less gas injected. This is where all you idle and cruising and normal acceleration efficiency work is.
We should think of closed loop operations as the time in which the engine is not being called upon to do its most powerful work. That does not mean that you're not accelerating, or even moving at highway speeds, that is not the case.... One can cruise at highway speeds for hours and never leave closed loop. In closed loop operations, we generally expect to throttle body's to be less than 80 percent open. In closed loop operations, we expect that the Viper is idling, gently accelerating, reasonably accelerating or cruising. All the while, the PCM is working to maximize the efficiency of your air fuel ratio. That ratio is most efficient at what is called "lambda". lambda is achieved when 14.7 lbs. of air is mixed with one pound fuel. The target, constantly being adjusted for engine load and other engine and driving conditions in the lambda is just that, 14.7. For those of us that want to see if in closed loop our cars are operating at lambda, we can. We do this by using the oxygen sensor that samples at a much higher rate and add a much more accurate rate and those found in stock Viper. Stock Viper's Oxygen sensors they are narrowband sensors, guys/gals that want to more accurate view their engine's ability to achieve lambda in closed the operations rely on gauges driven by wideband sensors. As load changes, so does the require A/F (Air Fuel) mix. It would be incorrect to assume that simply having a wideband sensor and wideband gauging your car is going to allow one to properly address all issues surrounding closed loop operations. We also need a high-quality software interface (program) to the ODB2 found in our GEN2 vipers. I have one, it plugs into the drivers left hand knee location of the OBD2 fitting under the dash. I can directly look into the PCM's operations, especially the adaptives and make sure they fall within a specified range of the stock PCM operating throughout closed loop. There is of course more on this subject, lots more, but there you have a very simplified begining, closed loop operations in a very summary fashion. I know what you are thinking....what happens in closed loop if I am running simms? Interesting question and one we will cover if anybody cares to.
I'm throwing this out here, to hopefully begin the process of helping others understand principal operations of the Viper and hopefully encourage others with much more knowledge than I have to step forward and share what they can. This is the tuning section, this is where interested minds can learn more. As to those that want to know what open loop operations are, I thought I would start a separate thread on that topic if there is interest here. if after awhile it becomes clear that nobody really cares about these subjects, trust me, I'll stop....
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