Nobody" > wrote in message
news:XnAlj.5641$5h6.763@trndny09...
>
> "Ed White" > 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
for
> > a 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
leaner-than-ideal
> 14:1 air/fuel ratio. While certainly not lean enough to cause engine
> 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.
> http://www.allfordmustangs.com/revie...hp/product/394
>
>
>
>
> >
> > I dug out the Ford shop manual for a 1999 Mustang 2V 4.6 Liter engine.
The
> > PCD includes TPS reference voltage values for a 1999 Mustang 4.6L V-8 -
At
> > idle 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
is
> > 1.2 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
by
> > the 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
related
> > to 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.
It
> > is 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
of
> > changes in air filter restriction.
> >
> > The following is from the PCD manual for a 1999 Mustang:
> >
> > -----
> >
> > "Fuel Trim
> >
> > The fuel control system uses the fuel trim table to compensate for
normal
> > variability of the fuel system components caused by wear or aging.
During
> > closed loop vehicle operation, if the fuel system appears "biased" lean
or
> > rich, 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
on
> > the 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
during
> > closed loop operation. This range is displayed in percentage (%). A
> > negative percentage means that the HO2S is indicating RICH and the PCM
is
> > attempting to lean the mixture. Ideally, Short Term FT may remain near
0%
> > but 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
Long
> > Term FT is from -35% to +35%. The ideal value is near 0% but variations
of
> > ±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
moving
> > Short 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
to
> > return to a value near 0%.
> >
> > As the fuel control and air metering components age and vary from
nominal
> > values, 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
closed
> > loop. As changing conditions continue the individual cells are allowed
to
> > update 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).
> >
> > Cum. Avg
> > Miles MPG
> > Since previous period
> > ------- ---------------------
> > 1176 18.1
> > 2132 18.9
> > 3274 19.0
> > 4234 17.9
> > 5276 18.2
> > 6433 17.2
> > 7358 18.7
> > 8488 18.9
> > 9540 18.8
> > 10666 18.1
> > 11812 19.2
> > 12888 19.3
> > 13995 19.2
> > 15230 18.6
> > 16276 19.1
> > 17425 19.0
> > 18518 17.9
> > 19454 18.6
> > 20444 19.0
> > 21375 18.1
> > 22423 18.1
> > 23543 18.4
> > 24684 18.2
> > 25684 18.8
> > 26895 18.9
> > 27889 19.3
> > 29045 17.7
> > 30199 19.3
> > 31203 18.8
> > 32151 20.1
> > 33175 19.6
> > 34236 19.7
> > 35313 20.5
> > 36396 18.9
> > 37403 19.3
> > 38325 19.6
> > 39306 19.9
> > 40275 19.5
> > 41311 19.8
> > 42494 18.6
> > 43721 19.2
> > 44685 18.2
> > 45757 18.8
> > 46686 18.8
> > 47745 18.7
> > 48456 19.3
> >
> > Ed
> >
>
> A good friend of mine once told me never to argue with a fool, because
after about five minutes it becomes impossible to tell who is who. Its
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.