i made a new intake for the car and put back on the dyno the best i could get out the car stock was 215 hp with just a cone at the end of the maf the best i could get was 224 hp now with the new setup i got a best of 231 hp
it is a 4 in pipe going down under the facory box and moved the maf down there as well i was getting high iat and was running lean so i put it down there to cool it down and richen up the air fuel it was getting 14.5-14.9 now it is down to 13.2-13.5 it is the diff. in air/fuel that help in the gain
the readings are before the cat i wielded a bung in for tunning the nitrous but when i went to tune the n2o i left the jets at home so that is what i started with and staying with untill someone can make a program for me to edit the pcm 100 hp at the wheels is good for now air/fuel on the n2o is nice and safe at 11.8
I think that Dyno tuning should be done with a WRAF.
The "conventional" O2 sensor in use since 1978 can tell the engine control system only that the exhaust is either too rich or too lean. It’s called a switching sensor because it makes a sharp voltage transition when the air/fuel mixture varies a tiny amount either side of ideal (14.7:1 for a gasoline engine). (fig. 5)
Refer to figure 5, Typical Switching-Style O2 Sensor Signal.
A. O2 Voltage (mV)
B. Time (s)
The engine controller responds to a rich signal from the O2 sensor by leaning the mixture, and responds to a lean signal by richening the mixture.
Even more precise fuel control would be possible if the O2 sensor could detect the exact deviation of the exhaust stream, lean or rich. The new wide-range air/fuel sensor can do this.
Wide-Range Air-Fuel Sensor (WRAF)
The wide-range air-fuel sensor, or WRAF sensor, discussed in this article will be used in the 4.6L LH2 engine in the 2004 Cadillac XLR and SRX. This sensor may also be referred to as a lambda sensor or wide-band sensor.
The WRAF sensor has been used in the past on select models of GM vehicles with the 3.0L L81 engine, first in the 1999-2001 Cadillac Catera, then in the 2000-2004 Saturn LS.
TIP: Throughout service information, the wide-range air-fuel sensor is referred to using the standard terminology of heated oxygen sensor or HO2S; in this article we will refer to it as the WRAF sensor.
Advantages of the WRAF
A typical V6 engine operating at 2500 rpm will produce approximately 62 cylinder pulses per second per cylinder bank. Refer to the graph in figure 5, which displays the voltage of a switching-style oxygen sensor. During one rich-to-lean and lean-to-rich transition of the oxygen sensor signal (1/2 second), there will be approximately 30 cylinder pulses.
Each cycle or switch is the average air-fuel ratio of several cylinders.
With a switching-style sensor, the engine controller will merely continue to adjust fuel trim, rich or lean, until it sees a signal swing in the opposite direction. The process then reverses and continues transitioning rich-to-lean and lean-to-rich. This explains the constant cycling or switching of the switching-style sensor.
So, the first advantage of the WRAF sensor is that it can detect the exact deviation from 14.7:1, rich or lean, and allow the engine controller to precisely adjust the air-fuel ratio to the desired amount.
TIP: Ideal combustion occurs with an air-fuel ratio of 14.7:1, also referred to a stoichiometric.
Most switching-style oxygen sensors operate within a range of 0 to 1000 millivolts, and as a result will not provide an accurate reading when the air-fuel ratio exceeds approximately 14.6:1 when rich or 14.8:1 when lean.
The WRAF sensor (fig. 6) can provide an accurate signal when the air-fuel ratio is as lean as 16:1 or as rich as 11:1, allowing the engine controller to continuously adjust fuel trim throughout this wide range of air-fuel ratios. So, a second advantage of the WRAF sensor is its ability to provide an accurate signal while operating in an air-fuel ratio, or lambda state, other than stoichiometric .
Refer to figure 6, WRAF Sensor.
A. Trimming Resistor
B. Resistor Cover
WRAF Wiring and Circuits
Refer to figure 7, WRAF Sensor Cutaway. Attachment 32962
The WRAF sensor has six wires (circuits), divided among three functions.
Reference Voltage -- The engine controller provides a fixed signal voltage to the WRAF sensor on two circuits. These circuits are called the reference voltage circuit (D) and the low reference circuit (E) from the reference air duct (P).
Pump Current -- There are two circuits called the input pump current (F) and output pump current (G). They provide an electromotive force needed for the movement of oxygen ions inside the sensor.
Heater (N) -- As with a switching-style sensor, there are heater voltage supply (L) and heater low control (K) circuits. They are similar in operation to most switching-style sensors.
Each sensor contains a trimming resistor (M) that is integral to the sensor connector. This trimming resistor is used during sensor manufacturing to calibrate each sensor to the desired performance specifications.
Here is what happens as exhaust flows past the sensor. Refer to the WRAF sensor cutaway (fig. 7): Attachment 32962
1. As the exhaust stream (A) passes the WRAF sensor, a sample of the exhaust gases enters the exhaust gas sample tube (B) and moves through the diffusion gap (C).
2. When the air-fuel ratio of the sampled exhaust gas changes, there is a corresponding change to the voltage potential between the reference voltage circuit (D) and the low reference circuit (E).
3. When the voltage on these circuits changes, the engine controller changes the amount of voltage on the input pump current circuit (F) and the output pump current circuit (G).
4. As the voltage on the input and output pump current circuits changes, oxygen ions move into or out of the pumping cell (H) through the porous layer (J). This brings the voltage potential between the reference voltage and low reference circuits back to a desired value.
5. By monitoring the required voltage and current level change on the input pump current and output pump current circuits, the engine controller can determine what the air-fuel ratio is at that moment.
6. The engine controller can then determine exactly how much the air-fuel ratio needs to be adjusted to maintain the desired voltage potential and thus the desired air-fuel ratio.
The WRAF sensor is able to determine the exact amount of air-fuel ratio change required for the upcoming cylinder pulses. This is different from a switching-style sensor, which has a much larger estimating error of the air-fuel ratio change.
On a low level, there is closed-loop operation between the engine controller and the WRAF sensor pumping circuits, low reference circuit, and reference voltage circuit.
On a high level, there is closed-loop operation between the exhaust sampling of the WRAF sensor and total fuel trim adjustment. The latter is similar to the most traditional closed-loop fuel systems.
How to Interpret WRAF Sensor Data on the Tech 2
TIP: Even though the engine controller and the WRAF sensor use various voltage levels during operation, the signal value displayed on the Tech 2 is a lambda value, NOT a voltage value.
The variable name “lambda” refers to the deviation above or below stoichiometric, or 14.7:1 air-fuel ratio. A lambda value of 1.000 is equivalent to a perfect stoichiometric ratio of 14.7:1. Depending on vehicle platform, the lambda value can be as low as 0.750 or as high as 3.999. A low lambda value represents a rich exhaust sample, and a high lambda value represents a lean exhaust sample.
The lambda value can be used to calculate the exact air-fuel ratio.
For example, a lambda value of 1.025 on the scan tool indicates that the system is operating lean. To find out exactly how lean, multiply 1.025 by 14.7. This gives the result of approximately 15.07:1. Conversely, a lambda value of 0.975 indicates the system is operating rich. Multiply 0.975 x 14.7 = 14.33:1. This gives you an idea of how the controller is able to determine the exact desired air-fuel ratio.
The Meaning of Extreme Lambda Values
How can a lambda value of 0.750 or 3.999 be meaningful? Multiply a lambda value of 3.999 x 14.7 = 58.79:1. This is clearly not an air-fuel ratio that any engine could operate under during cruise or acceleration.
Extreme lambda values are a result of the limits of the controller hardware and software. When a vehicle enters a fuel cut-off state during deceleration, the lambda value may move to a very high number (infinity) because the controller software and hardware are operating the pumping circuits at their maximum correction state to offset the extremely lean air-fuel ratio that is occurring. The controller software will not display infinity but will instead display a large number. Depending on the controller manufacturer, these maximum limits may be as low as 0.750 during a very rich condition, or as high as 3.999 during a very lean condition.
Acceleration and Cruise -- The lambda value stays fairly flat, close to 1.000, during the moderate to heavy acceleration and during cruise (A). This is because the sensor and the engine controller are in their own closed-loop operation and the lambda value only “drifts” above or below 1.000 as the engine controller makes its fuel trim adjustments. This closed-loop operation between the engine controller and the WRAF sensor is an instantaneous reaction to voltage deviations between the reference voltage circuit and low reference circuit and the resulting oxygen ion exchange via the pumping circuits.
Power Enrichment -- The lambda value moves lower when power enrichment is active (B).
Deceleration -- During deceleration, the lambda value moves to 1.989. This is because the engine controller has commanded a deceleration fuel cut-off state and, as a result, the exhaust stream is extremely lean (C). Notice how the engine controller will regulate the closing of the throttle; the throttle plate must be less than five percent open before the lambda value will finally move to 1.989. On this particular vehicle, 1.989 is the limiting value of the hardware and software.
Diagnosing a WRAF Sensor
Here are a few points to remember when diagnosing a WRAF sensor:
- With the sensor disconnected and the ignition on, the voltage level measured on the input pump current circuit or the output pump current circuit, on the engine harness side, is very low and should be measured using the DMM millivolts scaling.
- In addition to the input and output pump current circuits, with the sensor disconnected and the ignition on, there will be a voltage present on the reference voltage circuit, low reference circuit, and possibly the heater low control circuit. The applicable DTC tables, when necessary, will provide the exact voltage values. Of course, there will be battery voltage present on the heater ignition voltage supply circuit.
- The voltage that may be present on the heater low control circuit is a diagnostic voltage produced by the engine controller. This voltage is used by the engine controller to discriminate between a heater circuit open, short to ground, or short to voltage condition. Depending on platform, the diagnostic voltage may or may not be present.
- Remember this when performing voltage measurements on the engine harness side. When a circuit fault is present, it may cause voltage level changes on the input pump current, output pump current, reference voltage or low reference circuits. So, you must not assume that because the voltage of the first circuit you measured is not within the correct range it is the problem circuit!
- As with any heated oxygen sensor, no circuit repairs should be attempted to the sensor harness.
All dyno tuning should be done with a wideband. And yes, it really should run 10:1 after 15 or so seconds in power enrichment. This is done to cool the piston crown. There's no need to post wideband cutaways, I know what they are and how they work.
I saw the nitrous. I assume you have a STS looking at the way you are running the air intake? Are you running wet or dry? What kinda extra pop, 50hp 75hp 100hp? What does it run on the bottle? Any good or bad news since using nitrous, and could you recomend a kit or part number? I have some left over nitrous parts off an old TA I used to have that I sprayed, and lately have been thinking about putting the spray on the Cady.
Really any information, good or bad, would be appreciated, maybe I could make a sleeper to. Thanx.