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Eeyore
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 Posted: Sun Jun 15, 2008 11:51 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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Uncle Ben wrote:
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The computer in the car can't reach the richness it needs on E85
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Saab Trionic. It's in my car. A good article here....
http://en.wikipedia.org/wiki/Trionic_T5.5
Engine management system SAAB TRIONIC T5.5
Courtesy of: DrBoost
Overview
Saab Trionic T.5.5 is an engine management system that controls ignition,
fuel injection and turbo boost pressure. The system was introduced in 1994
Saab 900 with B204L engine. Since 1994 a number of changes have occurred.
1995. Four wire oxygen sensor, electronic heat plates in intake manifold
(not in US and CA markets). K line is connected via VSS (Vehicle Security
System) to enable immobilizing (certain markets). Vacuum pump for the vacuum
servo assisted brake system with some control from Trionic is used on
automobiles with automatic transmission.
1996. OBD II diagnostics on US and CA markets, which means two lambda sonds.
1996, 5. Leakage diagnostics of the EVAP system on the OBD II variant.
1997. Heat plates are removed.
1998,5. (Saab 9-3). K-line is connected via MIU (Main Instrument Unit) to
enable immobilizing from TWICE (Theft Warning Integrated Central
Electronics) (not in software for markets: US and CA). Fuel pump relay is
electrically supplied from main relay. Request signal for Air Condition is
feed from MIU. Electrical pre heating on oxygen sensor is supplied from main
relay. Requested boost pressure is raised somewhat on automobiles with
manual gearbox. SID message when leakage in EVAP-system is confirmed,
applicable in On-Board Diagnostics II variants.
1998. Two new engine variants; B204R and B204E, B204E were available with
manual gearbox only and demanded high octane gasoline to deliver the stated
torque. B204E is lacking boost pressure control, this engine wasn’t
available on US and CA markets. On the Swedish market automobiles is
equipped with the B204E engine, OBD II diagnostics and ORVR (On board
Refuelling Vapour Recovery system), a system that makes sure that the
gasoline vapour doesn’t escape into the surrounding air during refuelling.
Saab Trionic’s ignition system consists of an ignition cassette with four
ignition coils, one for each spark plug. The ignition system is capacitive.
The spark plugs are used as sensors to detect combustion and
pre-ignition/pinging. This renders camshaft position detector and knock
sensor redundant. This function also enables effective detection of
misfires, which is an OBD II demand. The fuel injection is fully sequential
and is dependent on the MAP (Manifold Absolute Pressure). Boost pressure
control (L and R engines) utilises a solenoid valve pneumatically connected
to the turbocharger’s waste gate.
The system was fitted on models Saab 900, Saab 9000 and Saab 9-3. This
information is however most accurate for the SAAB 900.
[edit]
Fuel
Fuel injector valves
The fuel injector valves are of a solenoid type with needle and seat. They
are opened by a current flowing through the injector's coil and are closed
by a strong spring when the current is switched off. To ensure as optimal
combustion as possible and with that lower exhaust emission the injectors
are equipped with four holes, which gives a good distribution of the fuel.
The squirts of fuel are very exact positioned (two jets on the backside on
each inlet valve). This put very high demands on the fixation of the
injectors. To secure this fixation the injectors are fixed in pairs by a
special retainer between cylinders 1 – 2 and 3 – 4. The injectors are
electrically supplied from the main relay, while the ECU grounds the
injectors.
[edit]
Fuel injection
Pre-injection
When the ignition is switched on, the main relay and fuel pump relay are
activated during a few seconds. As soon as the ECU gets the cranking signal
(from the crankshaft sensor) it initiate a coolant dependable injection with
all four injectors simultaneously which ensures a fast engine start. If the
engine is started and shortly after is switched off a new pre-injection is
initiated after the ignition's been switched off for 45 seconds.
Calculating of injection time
To decide how much fuel needs to be injected into each intake runner the ECU
calculates the air mass that had been drawn into the cylinder. The
calculation make use of the cylinder volume (B204 has a displacement of 0.5
litres per cylinder). That cylinder volume holds equal amount of air which
has a density and thus a certain mass. The air density is calculated using
the absolute pressure and temperature in the intake manifold. The air mass
for combustion has now been calculated and that value is divided by 14.7
(stoichiometric relation for gasoline mass to air mass) to determine the
required fuel mass for each combustion to inject. Since we know the flow
capacity of the injector and the density of the fuel (pre programmed values)
the ECU can calculate the duration of the injection. Using the oxygen sensor
1 the injection duration is corrected so we receive Lambda=1 (stoichiometric
combustion). When hard acceleration occurs the lambda correction is masked
and WOT (Wide Open Throttle) enrichment occurs for maximum performance. When
opening the throttle, acceleration enrichment (accelerationsupprikning in
Swedish) occurs and when closing the throttle deceleration emaciation
(decelartionsavmagring in Swedish) occurs. During a cold start and warm up,
before lambda correction is activated, coolant temperature dependable fuel
enrichment occurs. With a warm engine and normal battery voltage the
duration of injection varies between 2,5 ms at idle and approx. 18 – 20 ms
at full torque.
Lambda correction
The catalyst requires that the fuel/air mixture is stoichiometric. This
means that the mixture is neither rich or lean, it is exactly 14,7 kg air to
1 kg gasoline (Lambda=1). That is why the system is equipped with an oxygen
sensor in the forward part of the exhaust system. The sensor is connected to
pin 23 in the ECU and is grounded in the ECU via pin 47. The exhaust fumes
pass the oxygen sensor. The content of oxygen in the exhaust fumes is
measured through a chemical reaction, this results in an output voltage. If
the engine runs rich (Lambda lower than 1) the output voltage would be
approx. 0,9 V and if the engine runs lean (Lambda higher than 1) the output
voltage would be 0,1 V. The output voltage swings when Lambda passes 1. The
ECU continuously corrects the injection duration so that Lambda=1 is always
meet. To be able to function the oxygen sensor needs to be hot, this
requirement is meet by electrically pre heat the sensor. The pre heating
element is feed by B+ via fuse 38 and the main relay, the sensor is grounded
in the ECU via pin 50. The ECU estimates the temperature on the exhaust
gases (EGT) on the basis of the engine load and the engines RPM. At high EGT
the electrical pre heating is disconnected. The lambda correction is masked
during the engines first 640 revolutions after start if the coolant
temperature exceeds 18? (64F) at load ranges over idle and under WOT or 32?
(90F) at idle.
Adaptation
The ECU calculates the injection duration on basis of MAP and intake
temperature. Injection duration are then corrected by multiplication of a
correction factor, which is fetched from main fuel matrix
(huvudbränslematrisen in Swedish) and is dependable on MAP and RPM. The need
to correct the injection duration is due that the volumetric efficiency of
the cylinder is dependent on the engines RPM. The last correction is made
with the lambda correction, this results in a stoichiometric combustion
(Lambda=1). The lambda correction is allowed to adjust the calculated
injection duration by ±25%. The ECU can change the correction factors in the
main fuel matrix on basis of the lambda correction, this ensures good
driveability, fuel consumption and emissions when lambda correction isn’t
activated. This is called Adaptation.
Pointed adaptation
If the ECU calculates the injection duration to 8 ms but the lambda
correction adjusts it to 9 ms due low fuel pressure the ECU will “learn” the
new injection duration. This is done by changing the correction factor for
that particular RPM and load point in the main fuel matrix to a new
correction factor resulting in 9 ms injection duration. The correction
factor in this example will be raised by 9/8 (+12%). The pointed adaptation
can change the points in the main fuel matrix by ±25%. Adaptation occurs
every fifth minute and takes 30 seconds to finish, the criteria’s for the
adaptation are: Lambda correction is activated and the coolant temperature
is above 64? (147F). During the adaptation the ventilation valve on the
carbon canister is held close.
Global adaptation
The global adaptation on OBDII variants occurs during driving on non OBDII
variants the global adaptation occurs 15 minutes after engine shut down.
When the engine is inside a defined load and RPM range (60 – 120 kPa and
2000 – 3000 RPM) no pointed adaptation will occur all points in the fuel
matrix will be changed instead by a multiplication factor. Global adaptation
can change the points in the main fuel matrix by ±25% (Tech2 shows ±100%).
Adaptation occurs every fifth minute and takes 30 seconds to finish, the
criteria’s for the adaptation are: Lambda correction is activated and the
coolant temperature is above 64? (147F). During the adaptation the
ventilation valve on the carbon canister is held close.
Fuel cut
With fully closed throttle and engine RPM over 1900 RPM and with third,
fourth and fifth gear fuel cut will occur after a small delay (some second).
On automobiles with automatic transmission fuel cut are active in all
stages. The injectors are reactivated when the RPM hits 1400 RPM.
Fuel consumption measurement
The wire from the ECU to the third injector is also connected to the main
instrument. The main instrument calculates the fuel consumption based on the
injection pulses duration. The fuel consumption is used to help getting an
accurate presentation of the fuel level in the fuel tank and to calculate
average fuel consumption in SID.
[edit]
Turbo boost pressure
Basic charging pressure
Basic charging pressure is fundamental for charging pressure control. Basic
charging pressure is mechanically adjusted on the actuators pushrod between
the actuator and the waste gate. At to low basic charging pressure the
engine doesn’t revs up as expected when the throttle is opened quickly. At
to high basic charging pressure a negative adaptation occurs and maximum
charging pressure cannot be achieved. In addition there is a substantial
risk of engine damage since the charging pressure can’t be lowered enough
when regulating with attention to pre ignition/pinging. Basic charging
pressure shall be 0,40 ±0,03 bar (5,80 ±0,43 PSI). After adjustment the push
rod must have at least two turns (2 mm) pre tension when connecting to the
waste gate lever. The purpose with that is to make sure that the waste gate
is held close when not affected. On new turbo chargers the basic charging
pressure tends to be near or spot on the upper tolerance when the pre
tension is two turns. The pre tension may never be lesser than two turns (2
mm). When checking the basic charging pressure it shall be noted that the
pressure decreases at high RPM and increases at low outside temperatures.
Charging pressure regulation
Charging pressure regulation utilises a two coiled three way solenoid valve
pneumatically connected with hoses to the turbo charger’s waste gate, the
turbo chargers outlet and the compressor’s inlet. The solenoid valve is
electrically supplied from +54 via fuse 13 and is controlled by the ECU via
its pin 26 and pin 2. The control voltage is pulse width modulated (PWM) at
90 Hz below 2500 RPM and 70 Hz above 2500 RPM. The rationale for this change
is to avoid resonance phenomena in the pneumatic hoses. By grounding pin2
longer than pin 26 the charging pressure is decreased and vice verse, when
pin 26 is grounded longer than pin 2 the charging pressure is increased. To
be able to regulate the charging pressure the ECU must at first calculate a
requested pressure, a pressure value that the system must strive for. This
is done by taking a pre programmed value (matrix of values established in
respect of RPM and throttle opening). At WOT the pressure values for each
RPM are selected to make sure that the engine gets the requested torque.
When one or both of the following criteria’s are met, a limitation of the
charging pressure is set.
In first, second and reverse gear there is an RPM dependable maximum value.
The ECU calculates which gear that is in use by comparing the speed of the
automobile and the engines RPM.
When pre ignition/pinging occurs a maximum charge pressure is set on the
basis of a mean value from each cylinders retarding of the ignition.
One or both of the following criteria’s initiates a lowering of the charging
boost pressure to basic boost pressure.
When the brake pedal is pressed down and pin 15 on the ECU is supplied with
battery voltage.
Certain fault codes is set (Faulty throttle position sensor (TPS), pressure
sensor, pre ignition/pinging signal or charging pressure regulation) or low
battery voltage.
Computing, adaptation
When the required charge pressure has finally been calculated it is
converted to the PWM signal that controls the solenoid valve, The ECU then
controls that the actual pressure (measured by the pressure sensor)
corresponds with the required pressure. If needed the PWM is fine tuned by
multiplication of a correction factor. The correction factor (adaptation) is
then stored in the memory of the ECU and is always used in the calculation
of the PWM signal. The rationale with this is to make sure that the actual
pressure as soon as possible will be equal to the required after a change of
the load has occurred.
[edit]
Ignition timing
Ignition cassette
The ignition cassette is mounted on the valve cover on top of the spark
plugs. The ignition cassette houses four ignition coils/transformers whose
secondary coil is direct connected to the spark plugs. The ignition cassette
is electrically supplied with battery voltage from the main relay (B+) and
is grounded in an earth point. When the main relay is activated the battery
voltage is reformed to 400 V DC which is stored in a capacitor. 400 V
voltage is connected to one of the poles of the primary coil in the four
spark coils. To the ignition cassette there are four triggering lines
connected from the Trionic ECU, pin 9 (cyl. 1), pin 10 (cyl. 2), pin 11
(cyl. 3) and pin 12 (cyl. 4). When the ECU is grounding pin 9, the primary
coil for the first cylinder is grounded (via the ignition cassettes B+
intake) and 400 V is transformed up to a maximum of 40 kV in the secondary
coil for cyl. 1. The same procedure is used for controlling the ignition on
the rest of the cylinders.
Ignition regulation
At start the ignition point is 10° BTDC. To facilitate start when coolant
temperature is below 0°C the ECU will ground each trigger line 210
times/second between 10° BTDC and 20° ATDC, at which a “multi spark” will
appear. The function is active up to an engine speed of 900 RPM. At idle a
special ignition matrix is utilised. Normal ignition point is 6°-8° BTDC. If
the engine stalls e.g. cooling fan activation the ignition point is advanced
up to 20 ° BTDC in order to increase the engines torque to restore the idle
RPM. In the same way the ignition is retarded if the engines RPM is
increased. When the TPS senses an increase in throttle opening the ECU
leaves the idle ignition timing map and regulates the ignition timing in
respect of load and engine speed.
During engine operations the Ignition cassette continuously monitoring the
ion currents in the cylinders and send a signal to the Trionic ECU, pin 44,
in an event of knocking. The logic for this function rests solely in the
ignition cassette and is adaptive to be able to handle disturbing fuel
additives. The Trionic ECU is well aware which cylinder that has ignited and
could hence cope with the information feed through one pin. The signal to
pin 44 and ion current in the combustion chamber is related to each other,
when this signal reaches a certain level the ECU interprets this as a
knocking event and firstly lowering the ignition advance by 1,5° on this
cylinder. If the knocking is repeated the ignition advance is lowered
further 1,5 ° up to 12°. In case of the same lowering of the ignition timing
advance in all cylinders the ECU adds a small amount of fuel to all
cylinders. If knocking occurs when the MAP is over 140 kPa the knocking is
regulated by switching both fuel injection matrix and ignition advance
matrix. If this is not sufficient the charging pressure is lowered. This
purpose of this procedure is to maintain good performance. If the signal
between the ignition cassette and the ECU is lost, the charging pressure is
lowered to basic charging pressure and the ignition timing advance is
lowered 12° when it exist a risk of knocking due to engine load.
Combustion signals
The Trionic system lacks a camshaft position sensor. This sensor is normally
a prerequisite for a sequential pre ignition/pinging regulation and fuel
injection. Saab Trionic must decide whether cylinder one or cylinder four
ignites when the crank shaft position sensor indicates that cylinder one and
four is at TDC. This is done by help of ionisation current, one of the pole
of the secondary coil of the spark coils is connected to the spark plugs at
an ordinary manner. The other pole isn’t grounded directly but connected to
an 80 V voltage. This means that an 80 V voltage is fielded over the spark
gap of the spark plugs, except when the spark is fired. When combustion has
occurred the temperature in the combustion chamber is very high. The gases
are formed as ions and start to conduct electrical current. This results in
a current flowing in the spark plug gap (without resulting in a spark). The
ionisation current is measured in pair, cylinder one and two is one pair and
cylinder three and four in the other pair. If combustion occurs in cylinder
one or two the ignition cassette is sending a battery voltage (B+) pulse to
the ECU, pin 17. If the combustion takes place in cylinder three or four the
B+ pulse is feed to pin 18 in ECU. If the crankshaft position sensor is
indicating that cylinders one and four is at TDC and a B+ pulse enters the
ECU via pin 17 simultaneously, then the ECU know that it is cylinder one
that has ignited. At start the ECU doesn’t know which cylinder that is in
compression phase, hence ignition is initiated in both cylinder one and four
and 180° crank shaft degrees later sparks in cylinder two and three are
fired. As soon as combustion signals enters the ECU via pin 17 and pin 18
the ignition and fuel injection is synchronised to the engines firing order.
The combustion signals are also used to detect misfires.
[edit]
Heat plates
Heat plates are used to lower the warm up emissions. They vaporize the
injected fuel before it is drawn/forced into the cylinders and consequently
reducing the need for added fuel in the A/F mixture in the warm up phase
thus reducing the emissions. At engine start and coolant temperature lower
than +85°C Pin 29 on ECU is grounded and a relay in the engine compartment
are activated and closes the electrical circuit for the Heat Plates. The
circuit is protected by a 40 A MAXI fuse. When the coolant temperature is
warmer than +85°C or four minutes has passed the Heat Plates are switched
of.
To compensate for the increased air resistance in the intake, engines fitted
with Heat Plates have a slightly adjusted charge pressure, Approximately:
+0,2 bar, this means that LPT models with heat plates have a solenoid valve
to raise the charging pressure above basic charging pressure.
In case of a Heat Plate-failure the car may have drivability problems due
condensed fuel in the intake during cold engine operations. This condensed
fuel is compensated in engines without Heat Plates by enriching the A/F
mixture.
The activation of heat plates is in the software and activates different
code parts to achieve what the engine can do with the help of heat plates
and to overcome the restriction the heat plates does in the intake.
[edit]
Other features
Shift Up lamp
The Shift up lamp can be found on OBD II cars. The lamp helps the driver to
drive economically. The Lamp is supplied by ignition power (+15) and is
grounded in the Trionic ECU, pin 55. The shift up lamp is lit when the
ignition is turned on for three seconds to test the circuit. During normal
driving the lamp is lit when reaching a specific RPM while driving on light
loads. When wide opening the throttle the Shift up lamp is lit when the RPM
is near 6000 RPM. While driving on the fith gear the lamp will not lit. |
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Eeyore
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Eeyore
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| Posted: Sun Jun 15, 2008 11:58 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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Bret Cahill wrote:
| Quote: |
The same engine design could easily be adapted to an efficient
commuter vehicle.
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The answer to all your quibbles exists and is manufactured by Saab Automobil
AB
Ask GM why they haven't brought the Bio-Power range to the USA.
Graham |
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Eeyore
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| Posted: Sun Jun 15, 2008 11:58 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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DG wrote:
| Quote: |
If people are going to go to ethanol it might be easier to agree on
some one percentage ethanol and then use the right [high] compression
ratio engine.
Put a sensor in your fuel line and let the engine adjust to the
mixture in the line.
The compression ratio depends on the machinery geometry which isn't
easy to adjust without removing the head or crankshaft.
Ah, time for new engines...
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Saab have already made them all.
Graham |
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Eeyore
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| Posted: Sun Jun 15, 2008 11:59 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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DG wrote:
| Quote: |
20 years ago one of the smartest people I ever met was building
ceramic engines. Their time may have come...
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Big cooling problems AIUI.
Graham |
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Sevenhundred Elves
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| Posted: Mon Jun 16, 2008 9:23 am Post subject: Re: Experimental data on ethanol fuel efficiency |
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On Sun, 15 Jun 2008 19:59:44 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:
| Quote: |
DG wrote:
20 years ago one of the smartest people I ever met was building
ceramic engines. Their time may have come...
Big cooling problems AIUI.
Graham
|
I don't know of any better conductor for heat than diamond. I suppose
diamond whiskers might also contribute to the strength of the ceramic.
Pity, that synthetic diamond is still somewhat expensive.
S. |
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Eeyore
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| Posted: Mon Jun 16, 2008 10:33 am Post subject: Re: Experimental data on ethanol fuel efficiency |
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Sevenhundred Elves wrote:
| Quote: |
Eeyore wrote:
DG wrote:
20 years ago one of the smartest people I ever met was building
ceramic engines. Their time may have come...
Big cooling problems AIUI.
I don't know of any better conductor for heat than diamond. I suppose
diamond whiskers might also contribute to the strength of the ceramic.
Pity, that synthetic diamond is still somewhat expensive.
|
Bugger innit. Aluminium oxides aren't bad but beryllium's toxic BIG TIME.
Can they really handle the shock loading too ?
Graham |
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Sevenhundred Elves
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| Posted: Mon Jun 16, 2008 11:00 am Post subject: Re: Experimental data on ethanol fuel efficiency |
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On Mon, 16 Jun 2008 06:33:36 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:
| Quote: |
Sevenhundred Elves wrote:
Eeyore wrote:
DG wrote:
20 years ago one of the smartest people I ever met was building
ceramic engines. Their time may have come...
Big cooling problems AIUI.
I don't know of any better conductor for heat than diamond. I suppose
diamond whiskers might also contribute to the strength of the ceramic.
Pity, that synthetic diamond is still somewhat expensive.
Bugger innit. Aluminium oxides aren't bad but beryllium's toxic BIG TIME.
Can they really handle the shock loading too ?
Graham
|
I'd have to guess a little, but my guess would be yes, they can, since
thin whiskers of hard and brittle materials generally aren't brittle
at all, but tougher and more flexible than bigger lumps of the same
material.Compare graphite fibers to graphite, for instance. It's an
amazing difference, but the crystal structure is mainly the same. Like
you say, Al2O3 should be a cood heat conductor like any very hard
material, so maybe that's how they do/will do it. Wouldn't surprice me
if they'll use nanotubes in ceramics for added strength, some day.
Those are good heat conductors, too, according to Wikipedia.
Speaking of toxicity, I read in the news that doctors are concerned
about microfibers and carbon fibers, wondering if they might not turn
out to be as health damaging as asbestos. There seems to have been
very little research done on that, and that's what concerns the
doctors most, I suppose.
S. |
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Lloyd
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| Posted: Mon Jun 16, 2008 5:59 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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On Jun 15, 2:48 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:
| Quote: |
Uncle Ben wrote:
Bret Cahill <BretCah...@aol.com> wrote:
If people are going to go to ethanol it might be easier to agree on
some one percentage ethanol and then use the right [high] compression
ratio engine.
For the future, sure. I think 85% is good. For the present (since I
already have a usable car), I switched for the 18% savings I get
already; and then I discovered the extra pep that my car gets as a
bonus.
You'll get a hell of a lot more pep with a turbo ! That's why Saab's the
world leader in this technology.
They were they first to add turbos to ordinary everyday road cars,
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The first production turbocharged automobile engines came from General
Motors in 1962. The A-body Oldsmobile Cutlass Jetfire and Chevrolet
Corvair Monza Spyder were both fitted with turbochargers. The
Oldsmobile is often recognized as the first, since it came out a few
months earlier than the Corvair. -- wikipedia
| Quote: |
then
they developed the world's first and only ? 32 bit ECU (Trionic). Now
they've combined them to make the best flex-fuel cars in the world, with
emission levels that are stunningly low.
Graham |
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Stephen Sprunk
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| Posted: Mon Jun 16, 2008 8:27 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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Bret Cahill wrote:
| Quote: |
If people are going to go to ethanol it might be easier to agree on
some one percentage ethanol and then use the right [high] compression
ratio engine.
For the future, sure. �I think 85% is good.
Let's go with either that or 100%.
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E85 is the best you can do with conventional engines and in all weather,
and even then some places up north drop to E70 in the winter due to
ethanol's cold-start problems.
E100 is simply not possible without major engine changes. Brazil's E100
cars, for instance, have a small gasoline tank under the hood to assist
with starting and warming up the engine, after which the car goes to
pure ethanol. That's not a minor difference.
| Quote: |
Flex fuel was just a way to get the foot into the door so gas stations
would start to accomodate the fuel.
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Well, the idea was that the gas station would have tanks of pure
gasoline and pure ethanol, and the pump would mix them depending on
either user selection or the current relative prices. Since a flexfuel
car can anywhere from 0% to 85% ethanol, this makes a lot more sense
than picking a single fixed percentage -- or at least it did before oil
prices started climbing so fast. Now, there's little reason to go with
less than E85 (in cars that can take it) except in extremely cold weather.
| Quote: |
For the present (since I already have a usable car), I switched for
the 18% savings I get already; and then I discovered the extra pep
that my car gets as a bonus.
You'ld save even more and get even more pep with a higher compression
ratio. You'ld never be able to use gasoline again, however, because
of knock.
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Indeed, which is why we need to mandate _minimum_ ethanol content as
well, so that higher-compression engines will enter the mainstream.
Many cars already have significant knock problems with less than 91
octane gas anyways due to high (for pure gasoline) compression ratios.
| Quote: |
The only reason Indy cars get 2 mpg is because they are moving at
excessive speeds.
The same engine design could easily be adapted to an efficient
commuter vehicle.
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Um, no. The engine design is very different than what a high-efficiency
street car needs. Only minor modifications are warranted vs. current
high-efficiency gasoline engines, and even those aren't strictly
necessary (nor advisable until the minimum octane is higher).
S |
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Martin Brown
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| Posted: Mon Jun 16, 2008 8:44 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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Uncle Ben wrote:
| Quote: |
On Jun 15, 6:23 am, Uncle Ben <b...@greenba.com> wrote:
It is often claimed on the basis of chemical energy in fuels that the
driving efficiency of cars using those fuels must be proportional to
their energy content. Anecdotale evidence has disagreed with this
assumption.
In 2005, the American Coalition on Ethanol commissioned a study of
this question. Their report can be found at
http://www.ethanol.org/pdf/contentmgmt/ACEFuelEconomyStudy_001.pdf
Features of the report are that they actually drove three different
test vehicles several hundred miles under conditions designed to
eliminate accidental differences between wind speed, vehicle speed,
and others.
[snip]
more study is needed to determine if there are any long-term
consequences.
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That is their get out clause. Ethanol in E85 is quite a good solvent in
an older fuel system that was designed expecting only to see mostly
hydrocarbons. In a flex fuel vehicle then fair enough - but it would
help to have a higher compression to match ethanols burning properties.
| Quote: |
Given the differences found between BTU and mileage in this test, a
study of the differences in fuel
economy between unleaded and E85 in flexible fuel vehicles should also
be investigated. Currently,
mileage is assumed to be almost 30% lower when using E85, while
anecdotal evidence indicates that
actual MPG performance of E85 is much better than that estimate.
|
Anecdotal evidence is always a bit iffy. A car that has been properly
tuned after changing the fuel might well do somewhat better mpg if the
engine mixture was slightly wrong before the fuel was changed.
| Quote: |
If anyone suspects that the American Coalition for Ethanol might
improperly influence the results of their study to favor their product
should consider doing the experiment on their own vehicle, as I have
done.
|
I am sure that an advocate lobby group for an insanely inefficient fuel
from food process must be paragons of scientific virtue who always tell
the truth the whole truth and nothing but the truth.
| Quote: |
Establish your baseline by filling up with your usual fuel, letting
the automatic pump dictate the stop. Set your trip odometer to 0.
Drive your usual routine for 200 miles. record the exact miles driven.
|
Be worth having the car properly tuned up first before you baseline it.
I suspect at least some of the mileage improvements you are seeing on
changing to ethanol come from having tuned up the engine properly again
in the process from a sub optimal state.
| Quote: |
Then do it again with a mixture of 2 parts E10 to 1 part E85 more or
less and repeat the measurement. When you fill up you note the total
amount of each fuel you put in. That is the amount of gasoline you
burned. (Your fuel mixture will be slightly lower than E32 because of
the residual straight gasoline in your tank when you filled up.)
After 200 more miles, note the miles driven, fill up with anything you
like, noting the amount you put in, which is the amount of the mixture
you burned.
|
Better to do it over nearly a tank full. At least that way you get
soemthing like a reasonable average over all conditions.
| Quote: |
(Your check-engine light probably will not come with a mere E30 in
this trial, but if it does, don't panic. It is just the extra oxygen
in ethanol that is making your computer think there is a leak in the
system. When you resume with your usual fuel, it will quickly go
out.)
Figure your mpg on each trial and report back here! The energy
content theory says your mileage will drop 10%. But you will be the
jury for this theory!
|
It is also going to depend somewhat on the sort of mileage you do. If
you spend a lot of time idling at traffic lights the engine idle speed
could be quite a big factor in perceived milage.
If you test it cruising on a motorway at a steady 70mph that gives a
pretty good clean measure of conversion of fuel to useful work.
There is also the risk of bias. You want to believe this result and get
better milage so with the E85 you drive better with more anticipation
and less heavy footed use of the brakes - net result better milage.
Regards,
Martin Brown
** Posted from http://www.teranews.com ** |
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Stephen Sprunk
Guest
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| Posted: Mon Jun 16, 2008 8:47 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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Eeyore wrote:
| Quote: |
Sevenhundred Elves wrote:
Eeyore wrote:
DG wrote:
20 years ago one of the smartest people I ever met was building
ceramic engines. Their time may have come...
Big cooling problems AIUI.
I don't know of any better conductor for heat than diamond. I suppose
diamond whiskers might also contribute to the strength of the ceramic.
Pity, that synthetic diamond is still somewhat expensive.
Bugger innit. Aluminium oxides aren't bad but beryllium's toxic BIG TIME.
Can they really handle the shock loading too ?
|
Honda's been using carbon-fiber reinforced cylinder sleeves for nearly a
decade now with compression ratios up to 11.7:1. No problems -- and no
need to go to a ceramic block.
I don't know how far the technology can be stretched beyond 12:1, but
that's a heck of a lot higher than most cars are today, and is a
relatively simple manufacturing change to existing engines, unlike
moving to a ceramic block.
S |
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Ernieman
Guest
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| Posted: Mon Jun 16, 2008 11:03 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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"Sevenhundred Elves" <sevenhundred@elves.invalid> wrote in message
news:q8qb54htvl1pa2vnv7l9h7qa417e2k9b5m@4ax.com...
| Quote: |
On Sun, 15 Jun 2008 19:59:44 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:
DG wrote:
20 years ago one of the smartest people I ever met was building
ceramic engines. Their time may have come...
Big cooling problems AIUI.
Graham
I don't know of any better conductor for heat than diamond. I suppose
diamond whiskers might also contribute to the strength of the ceramic.
Pity, that synthetic diamond is still somewhat expensive.
S.
|
Presumably, there is an easy solution to the cooling problem: inject water
into the cylinders; see
http://peswiki.com/index.php/Directory:Crower's_Six-Stroke_Engine
Hopefully, the ceramic engine will not have the corrosion issues of metal
parts.
Ernie |
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Eeyore
Guest
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| Posted: Mon Jun 16, 2008 11:31 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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Stephen Sprunk wrote:
| Quote: |
Eeyore wrote:
Sevenhundred Elves wrote:
Eeyore wrote:
DG wrote:
20 years ago one of the smartest people I ever met was building
ceramic engines. Their time may have come...
Big cooling problems AIUI.
I don't know of any better conductor for heat than diamond. I suppose
diamond whiskers might also contribute to the strength of the ceramic.
Pity, that synthetic diamond is still somewhat expensive.
Bugger innit. Aluminium oxides aren't bad but beryllium's toxic BIG TIME.
Can they really handle the shock loading too ?
Honda's been using carbon-fiber reinforced cylinder sleeves for nearly a
decade now with compression ratios up to 11.7:1. No problems -- and no
need to go to a ceramic block.
I don't know how far the technology can be stretched beyond 12:1, but
that's a heck of a lot higher than most cars are today, and is a
relatively simple manufacturing change to existing engines, unlike
moving to a ceramic block.
|
Fixed compression ratios, or lack of turbo boost are dead technology.
Graham |
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Eeyore
Guest
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| Posted: Mon Jun 16, 2008 11:33 pm Post subject: Re: Experimental data on ethanol fuel efficiency |
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Lloyd wrote:
| Quote: |
On Jun 15, 2:48 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:
Uncle Ben wrote:
Bret Cahill <BretCah...@aol.com> wrote:
If people are going to go to ethanol it might be easier to agree on
some one percentage ethanol and then use the right [high] compression
ratio engine.
For the future, sure. I think 85% is good. For the present (since I
already have a usable car), I switched for the 18% savings I get
already; and then I discovered the extra pep that my car gets as a
bonus.
You'll get a hell of a lot more pep with a turbo ! That's why Saab's the
world leader in this technology.
They were they first to add turbos to ordinary everyday road cars,
The first production turbocharged automobile engines came from General
Motors in 1962.
|
Bollocks.
The only company to make them their standard line were Saab, And My God,
they're far better at it than any of your useless US behemoths.
Graham |
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