Re: Mustang GT and K&N air charger
- From: "Ironrod" <cemuza@xxxxxxxxxxxxxxxx>
- Date: Sat, 16 Feb 2008 09:37:33 GMT
Nobody" <nobody@xxxxxxx> wrote in message
"Ed White" <cewhite3@xxxxxxxxxxxxxx> wrote in message
****lots of previous stuff removed*****
I'll take one last stab at this.....
The basis of your argument seems to be that automotive engineers are
idiots who cannot design a fuel injection system that will compensate
leaner-than-ideala minor difference in the flow restriction of an air filter. I don't
believe this to be the case.
Correct, refer to following link:
Dyno testing the 2005 GT has shown that the computer is so sensitive to
airflow changes that a computer modification is necessary in order to
control the air/fuel ratio at the proper level. Installing this air intake
assembly on a 2005 GT without any tuning will result in a
14:1 air/fuel ratio. While certainly not lean enough to cause engineThe
durablility concerns, it is leaner than what is desired for optimum
performance. Even when replacing the air filter ONLY to a higher flow
assembly, the air/fuel ratio leans out at an alarming rate.
I dug out the Ford shop manual for a 1999 Mustang 2V 4.6 Liter engine.
AtPCD includes TPS reference voltage values for a 1999 Mustang 4.6L V-8 -
isidle the voltage is OK if it is anywhere between 0.52 and 1.27 V. At 30
mph, the acceptable range is 1 to 1.2 V. At 55 mph the acceptable range
by1.2 to 1.5 V. Clearly the tps value is not a major determining factor in
adjusting the A/F ratio since the acceptable values at idle and 55 mph
actually overlap. No other sensor related to the A/F ratio are affected
relatedthe air filter restriction. The only other sensors in front of the
throttle plate are the MAF sensor and air temperature sensor. Neither
will be affected by small changes in pressure in the intake tract
Itto the air filter restriction. A 1999 Ford 4.6L does not utilize a
barometric pressure sensor.
The following sensor are part of the system:
Camshaft Position (CMP) Sensor -4.6L
Crankshaft Position (CKP) Sensor -4.6L
Throttle Position (TP) Sensor
Idle Air Control (IAC) Valve -4.6L, (2V)
Engine Coolant Temperature (ECT) Sensor -4.6L, (2V)
Mass Air Flow (MAF) Sensor -4.6L, (2V, 4V)
Intake Air Temperature (IAT) Sensor
Heated Oxygen Sensor (HO2S)
Catalyst Monitor Sensor
Clutch Pedal Position (CPP) Switch
Fuel Pressure Sensor
Except for the TPS, none of these will be affected by normal sorts of
changes in the air filter restriction. As I have tried to explain
previously, the TPS is just a gross indicator of the throttle position.
ofis not designed to be used for the sort of fine A/F ratios you are
suggesting it is used for. The range of acceptable output valves for a
given throttle position is so wide that it cannot possibly be a
determining factor when evaluating changes in fuel economy as a result
normalchanges in air filter restriction.
The following is from the PCD manual for a 1999 Mustang:
The fuel control system uses the fuel trim table to compensate for
Duringvariability of the fuel system components caused by wear or aging.
orclosed loop vehicle operation, if the fuel system appears "biased" lean
onrich, the fuel trim table will shift the fuel delivery calculations to
remove the bias. The fuel system monitor has two means of adapting Short
Term Fuel Trim (FT) and Long Term Fuel Trim (FT). Short Term FT is
referred to as LAMBSE and Long Term FT references the fuel trim table.
Short Term Fuel Trim (Short Term FT) (displayed as SHRTFT1 and SHRTFT2
duringthe NGS tool) is a parameter that indicates short-term fuel adjustments.
Short Term FT is commonly referred to as LAMBSE. LAMBSE is calculated by
the PCM from HO2S inputs and helps maintain a 14.7:1 air/fuel ratio
isclosed loop operation. This range is displayed in percentage (%). A
negative percentage means that the HO2S is indicating RICH and the PCM
0%attempting to lean the mixture. Ideally, Short Term FT may remain near
Longbut can adjust between -25% to +35%.
Long Term Fuel Trim (Long Term FT) (displayed as LONGFT1 and LONGFT2 on
the NGS tool) is the other parameter that indicates long-term fuel
adjustments. Long Term FT is also referred to as Fuel Trim. Long Term FT
is calculated by the PCM using information from the Short Term FT to
maintain a 14.7:1 air/fuel ratio during closed loop operation. The Fuel
Trim strategy is expressed in percentages. The range of authority for
ofTerm FT is from -35% to +35%. The ideal value is near 0% but variations
moving±20% are acceptable. Information gathered at different speed load points
are stored in fuel trim cells in the fuel trim tables, which can be used
in the fuel calculation.
Short Term FT and Long Term FT work together. If the HO2S indicates the
engine is running rich, the PCM will correct the rich condition by
toShort Term FT in the negative range (less fuel to correct for a rich
combustion). If after a certain amount of time Short Term FT is still
compensating for a rich condition, the PCM "learns" this and moves Long
Term FT into the negative range to compensate and allows Short Term FT
nominalreturn to a value near 0%.
As the fuel control and air metering components age and vary from
closedvalues, the fuel trim learns corrections while in closed loop fuel
control. The corrections are stored in a table that is a function of
engine speed and load. The tables reside in Keep Alive Random Access
Memory (RAM) and are used to correct fuel delivery during open and
toloop. As changing conditions continue the individual cells are allowed
after about five minutes it becomes impossible to tell who is who. Itsupdate for that speed load point. If, during the adaptive process, both
Short Term FT and Long Term FT reach their high or low limit and can no
longer compensate, the MIL is illuminated and a DTC is stored."
And finally, here is a challenge for you. The chart below lists the
average fuel economy over 900 to 1250 mile intervals for my 2006 Nissan
Frontier - tell me approximately at which points the air filter was
changed......should be a piece of cake if filter restriction affect fuel
economy as drastically as you think. This truck is a farm vehicle and
spends a significant amount of time on dirt road and field paths. It
probably saw more dust last October than your Mustang has ever seen (I
pick peanuts in October - almost nothing generates more dust).
Since previous period
A good friend of mine once told me never to argue with a fool, because
getting to be the same with this thread, A point that I think was
overlooked is that nobody pointed out that at normal idle the intake is
almost 100% restricted, (closed). The almost part being the small amount of
air needed supply the idle circuit. The engine changes speed (RPM) by
removing that restriction to allow for more air as the demand increases.
Point of fact, if that restriction isn't there then the engine will continue
to spin up until it self-destructs. You need restriction in order to
control the engine output.
Now while I've never measured it I would suspect that the intake is still
restricted by over 90% even when cruising at 70.
Mileage is not effected solely by air flow changes, what has to change is
the air/fuel ratio. If sufficient air is flowing to feed the fire then
you're golden. With current electronics measuring the air coming in, the
exhaust going out and adjusting the fuel feed in between the air/fuel ratio
is held static.
Another misconception is that the engine has to work harder in order to suck
the air through a dirty filter than it does through a clean one. It
doesn't. (Hard to believe I know). The engine isn't sucking air through
the filter, it is sucking it past the throttle plate, which is almost
completely closed to start with. (If it wasn't the engine would spin up out
of control.) Air flows across the filter as a result of the pressure drop.
The amount of restriction needed to maintain a certain RPM at a certain load
is fixed. Restriction of the air filter, intake, throttle body, manifold &
outside pressure are all cumulative but overall pressure drop is the same
for a specific load. An example, if you were measure the pressure drop
between the outside air and just aft of the throttle body you would have a
number that would directly correlate with how much effort the engine is
expending to suck the air in. Remove the entire intake tract so there just
a bare throttle body and take the measurement again you would still have the
exact same number. In other words the engine worked just as hard to suck
air through the intake as it did to suck it straight out of the atmosphere.
The throttle would be slightly more closed to compensate for the loss of the
restriction caused by the missing components but the overall result would
remain the same.
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