onsdag den 6. juni 2018 kl. 21.37.56 UTC+2 skrev Johnny B Good:> On Wed, 06 Jun 2018 11:34:09 -0700, Lasse Langwadt Christensen wrote: > > > onsdag den 6. juni 2018 kl. 20.09.01 UTC+2 skrev mako...@yahoo.com: > >> > > >> > Now I've got to take care of a production line stop situation. Those > >> > are always fun. Grumble. > >> > > >> > -- > >> > Regards, Joerg > >> > > >> > http://www.analogconsultants.com/ > >> > >> the interesting real life behavior of spark plugs is... > >> > >> if you have a "fouled" plug" that the car cannot fire.... > >> > >> sometimes adding another spark gap in series with the fouled plug will > >> allow the car to fire the fouled plug. > >> > >> It seems that if the coil is connected directly to the fouled plug, it > >> can never develop enough voltage to fire. > >> > >> But if a second gap is inserted in series, then the coil CAN develop > >> the voltage and when it fires, both gaps will arc. > >> > >> I discovered this quite by accident. Back in the late 60's I had a car > >> that was mis firing on one cylinder. The standard troubleshooting > >> procedure called for removing the wire from one plug one at a time and > >> the one that makes no difference is the bad one. I noticed as I was > >> putting the wire back on, when I held the wire close to but not > >> attached, an arc would jump and the car would run better. I latter > >> found they actually made small inline gaps just for that purpose. > >> > >> > > many cars run wasted spark with two plugs in series > > That's purely a trick to use a special ignition coil to serve two > cylinders from a single CB wire using a floating HT winding that > effectively puts the two spark plug gaps in series. It works best when > the waste spark occurs on the exhaust stroke (on a 360 deg crank twin > cylinder 4 stroke engine for example).I know
SPICE model for a spark plug?
Started by ●June 5, 2018
Reply by ●June 6, 20182018-06-06
Reply by ●June 6, 20182018-06-06
On Wed, 6 Jun 2018 11:29:26 -0700 (PDT), tabbypurr@gmail.com wrote:>On Wednesday, 6 June 2018 19:19:17 UTC+1, Jim Thompson wrote: >> On Wed, 6 Jun 2018 11:08:36 -0700 (PDT), tabbypurr wrote: >> >On Wednesday, 6 June 2018 03:35:48 UTC+1, bill....@ieee.org wrote: >> >> On Wednesday, June 6, 2018 at 9:09:35 AM UTC+10, Joerg wrote: >> > >> >> > Looking for a SPICE model that mimics a spark plug, ideally with and >> >> > without fuel. Does anyone know where to find one? >> >> > >> >> > So far I found: >> >> > >> >> > >> >> > .subckt spark_gap 1 4 >> >> > R_off 1 2 1e7 ; dark resistance (affects breakdown voltage) >> >> > R_ion 1 2 R=10/V(ion)**.75 ; dynamic ionization resistance >> >> > Dfall 2 3 10V ; bidirectional cathode fall voltage >> >> > Cdfall 2 3 50p Rser=100 ; for convergence >> >> > V_ion 3 4 0 ; current sense for behavioral sources >> >> > B_ion 0 ion I=I(V_ion)**2 ; measure of channel ionization >> >> > C_ion ion 0 5u Rpar=1 ; ionization time constant >> >> > .model 10V d(Vfwd=10 Vrev=10 Ron=1) >> >> > .ends spark_gap >> >> > >> >> > >> >> > However, the spark occurs at a few hundred volts and changing parameters >> >> > doesn't do much. >> >> >> >> A spark plug breaks over at about 20kV. It's an avalanche breakdown in compressed gas, so you have to have a free charge carrier show up to initiate the the avalanche. Car cylinders are dirty places, so it might be a chunk of soot. >> >> >> >> The currents involved in the established avalanche would be high enough to sustain an arc if it went on for long enough, but you have an initial glow discharge with a voltage drop of a hundred volts or so for perhaps a microsecond before the ion bombardment gets one electrode surface hot enough to allow the arc mechanism to take over - which is to say to let the surface get hot enough into distort under the influence of the applied electric field to create lots of atomically sharp spikes that emit electrons by "warm" field emission. >> >> >> >> Best of luck modelling that in Spice. >> >> >> >> The presence and absence of fuel make a difference to the multiplication process that forms the initial spark, so the initial breakdown voltage is going to be different, and it influences the glow discharge period when the discharge moves from a glow to an arc. Once the arc is established the fuel content doesn't make any difference. >> >> >> >> A friend of mine set up a laser system for looking at the gas flows inside a single cylinder test engine for Shell in the later 1970's, but he was more worried about the combustion initiated by the spark than the spark itself. >> > >> >One car I had with points & coil produced around 6kV for sparkplugs IIRC, nothing like 20kV >> > >> > >> >NT >> >> What brand? In air, or under compression? >> >> ...Jim Thompson > >Lada, late 1960s design. 6-7kV at idle. AIUI figures like 20kV are more associated with electronic ignition, but it's not an area of expertise for me. Measured by an adjustable spark gap in open air, that was measuring the max V_out the coil could produce. So it can't have delivered more to the compressed cylinder content - must have dlivered less in fact. > > >NTThat voltage is _after_ the HV finally breaks-over. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions, by understanding what nature is hiding. "It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie
Reply by ●June 6, 20182018-06-06
On 2018-06-06 12:50, Jim Thompson wrote:> On Wed, 6 Jun 2018 11:29:26 -0700 (PDT), tabbypurr@gmail.com wrote: > >> On Wednesday, 6 June 2018 19:19:17 UTC+1, Jim Thompson wrote: >>> On Wed, 6 Jun 2018 11:08:36 -0700 (PDT), tabbypurr wrote: >>>> On Wednesday, 6 June 2018 03:35:48 UTC+1, bill....@ieee.org >>>> wrote: >>>>> On Wednesday, June 6, 2018 at 9:09:35 AM UTC+10, Joerg >>>>> wrote: >>>> >>>>>> Looking for a SPICE model that mimics a spark plug, ideally >>>>>> with and without fuel. Does anyone know where to find one? >>>>>> >>>>>> So far I found: >>>>>> >>>>>> >>>>>> .subckt spark_gap 1 4 R_off 1 2 1e7 ; dark resistance >>>>>> (affects breakdown voltage) R_ion 1 2 R=10/V(ion)**.75 ; >>>>>> dynamic ionization resistance Dfall 2 3 10V ; bidirectional >>>>>> cathode fall voltage Cdfall 2 3 50p Rser=100 ; for >>>>>> convergence V_ion 3 4 0 ; current sense for behavioral >>>>>> sources B_ion 0 ion I=I(V_ion)**2 ; measure of channel >>>>>> ionization C_ion ion 0 5u Rpar=1 ; ionization time >>>>>> constant .model 10V d(Vfwd=10 Vrev=10 Ron=1) .ends >>>>>> spark_gap >>>>>> >>>>>> >>>>>> However, the spark occurs at a few hundred volts and >>>>>> changing parameters doesn't do much. >>>>> >>>>> A spark plug breaks over at about 20kV. It's an avalanche >>>>> breakdown in compressed gas, so you have to have a free >>>>> charge carrier show up to initiate the the avalanche. Car >>>>> cylinders are dirty places, so it might be a chunk of soot. >>>>> >>>>> The currents involved in the established avalanche would be >>>>> high enough to sustain an arc if it went on for long enough, >>>>> but you have an initial glow discharge with a voltage drop of >>>>> a hundred volts or so for perhaps a microsecond before the >>>>> ion bombardment gets one electrode surface hot enough to >>>>> allow the arc mechanism to take over - which is to say to let >>>>> the surface get hot enough into distort under the influence >>>>> of the applied electric field to create lots of atomically >>>>> sharp spikes that emit electrons by "warm" field emission. >>>>> >>>>> Best of luck modelling that in Spice. >>>>> >>>>> The presence and absence of fuel make a difference to the >>>>> multiplication process that forms the initial spark, so the >>>>> initial breakdown voltage is going to be different, and it >>>>> influences the glow discharge period when the discharge moves >>>>> from a glow to an arc. Once the arc is established the fuel >>>>> content doesn't make any difference. >>>>> >>>>> A friend of mine set up a laser system for looking at the gas >>>>> flows inside a single cylinder test engine for Shell in the >>>>> later 1970's, but he was more worried about the combustion >>>>> initiated by the spark than the spark itself. >>>> >>>> One car I had with points & coil produced around 6kV for >>>> sparkplugs IIRC, nothing like 20kV >>>> >>>> >>>> NT >>> >>> What brand? In air, or under compression? ...Jim Thompson >> >> Lada, late 1960s design. 6-7kV at idle. AIUI figures like 20kV are >> more associated with electronic ignition, but it's not an area of >> expertise for me. Measured by an adjustable spark gap in open air, >> that was measuring the max V_out the coil could produce. So it >> can't have delivered more to the compressed cylinder content - must >> have dlivered less in fact. >> >> >> NT > > That voltage is _after_ the HV finally breaks-over. ...Jim Thompson >On Russian-made cars you never know. I remember one journalist who was transferred to Russia who reported about his experience when buying a car there. They had exactly three cars at the dealership, all the same type Lada (essentially a copy of an older Fiat model), in three different colors. Two wouldn't start and the third had a flat tire (in the show room!). So they bought the one with the flat tire. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●June 6, 20182018-06-06
On 06/06/2018 03:54 PM, Joerg wrote:> On 2018-06-06 12:50, Jim Thompson wrote: >> On Wed, 6 Jun 2018 11:29:26 -0700 (PDT), tabbypurr@gmail.com wrote: >> >>> On Wednesday, 6 June 2018 19:19:17 UTC+1, Jim Thompson wrote: >>>> On Wed, 6 Jun 2018 11:08:36 -0700 (PDT), tabbypurr wrote: >>>>> On Wednesday, 6 June 2018 03:35:48 UTC+1, bill....@ieee.org >>>>> wrote: >>>>>> On Wednesday, June 6, 2018 at 9:09:35 AM UTC+10, Joerg >>>>>> wrote: >>>>> >>>>>>> Looking for a SPICE model that mimics a spark plug, ideally >>>>>>> with and without fuel. Does anyone know where to find one? >>>>>>> >>>>>>> So far I found: >>>>>>> >>>>>>> >>>>>>> .subckt spark_gap 1 4 R_off 1 2 1e7 ; dark resistance >>>>>>> (affects breakdown voltage) R_ion 1 2 R=10/V(ion)**.75 ; >>>>>>> dynamic ionization resistance Dfall 2 3 10V ; bidirectional >>>>>>> cathode fall voltage Cdfall 2 3 50p Rser=100 ; for >>>>>>> convergence V_ion 3 4 0 ; current sense for behavioral >>>>>>> sources B_ion 0 ion I=I(V_ion)**2 ; measure of channel >>>>>>> ionization C_ion ion 0 5u Rpar=1 ; ionization time >>>>>>> constant .model 10V d(Vfwd=10 Vrev=10 Ron=1) .ends >>>>>>> spark_gap >>>>>>> >>>>>>> >>>>>>> However, the spark occurs at a few hundred volts and >>>>>>> changing parameters doesn't do much. >>>>>> >>>>>> A spark plug breaks over at about 20kV. It's an avalanche >>>>>> breakdown in compressed gas, so you have to have a free >>>>>> charge carrier show up to initiate the the avalanche. Car >>>>>> cylinders are dirty places, so it might be a chunk of soot. >>>>>> >>>>>> The currents involved in the established avalanche would be >>>>>> high enough to sustain an arc if it went on for long enough, >>>>>> but you have an initial glow discharge with a voltage drop of >>>>>> a hundred volts or so for perhaps a microsecond before the >>>>>> ion bombardment gets one electrode surface hot enough to >>>>>> allow the arc mechanism to take over - which is to say to let >>>>>> the surface get hot enough into distort under the influence >>>>>> of the applied electric field to create lots of atomically >>>>>> sharp spikes that emit electrons by "warm" field emission. >>>>>> >>>>>> Best of luck modelling that in Spice. >>>>>> >>>>>> The presence and absence of fuel make a difference to the >>>>>> multiplication process that forms the initial spark, so the >>>>>> initial breakdown voltage is going to be different, and it >>>>>> influences the glow discharge period when the discharge moves >>>>>> from a glow to an arc. Once the arc is established the fuel >>>>>> content doesn't make any difference. >>>>>> >>>>>> A friend of mine set up a laser system for looking at the gas >>>>>> flows inside a single cylinder test engine for Shell in the >>>>>> later 1970's, but he was more worried about the combustion >>>>>> initiated by the spark than the spark itself. >>>>> >>>>> One car I had with points & coil produced around 6kV for >>>>> sparkplugs IIRC, nothing like 20kV >>>>> >>>>> >>>>> NT >>>> >>>> What brand? In air, or under compression? ...Jim Thompson >>> >>> Lada, late 1960s design. 6-7kV at idle. AIUI figures like 20kV are >>> more associated with electronic ignition, but it's not an area of >>> expertise for me. Measured by an adjustable spark gap in open air, >>> that was measuring the max V_out the coil could produce. So it >>> can't have delivered more to the compressed cylinder content - must >>> have dlivered less in fact. >>> >>> >>> NT >> >> That voltage is _after_ the HV finally breaks-over. ...Jim Thompson >> > > On Russian-made cars you never know. I remember one journalist who was > transferred to Russia who reported about his experience when buying a > car there. They had exactly three cars at the dealership, all the same > type Lada (essentially a copy of an older Fiat model), in three > different colors. Two wouldn't start and the third had a flat tire (in > the show room!). So they bought the one with the flat tire. >It was a copy of a Fiat 124 sedan, including the reliability. LADA is a Russian acronym for "Fix it again, Ivan". ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●June 6, 20182018-06-06
onsdag den 6. juni 2018 kl. 21.54.48 UTC+2 skrev Joerg:> On 2018-06-06 12:50, Jim Thompson wrote: > > On Wed, 6 Jun 2018 11:29:26 -0700 (PDT), tabbypurr@gmail.com wrote: > > > >> On Wednesday, 6 June 2018 19:19:17 UTC+1, Jim Thompson wrote: > >>> On Wed, 6 Jun 2018 11:08:36 -0700 (PDT), tabbypurr wrote: > >>>> On Wednesday, 6 June 2018 03:35:48 UTC+1, bill....@ieee.org > >>>> wrote: > >>>>> On Wednesday, June 6, 2018 at 9:09:35 AM UTC+10, Joerg > >>>>> wrote: > >>>> > >>>>>> Looking for a SPICE model that mimics a spark plug, ideally > >>>>>> with and without fuel. Does anyone know where to find one? > >>>>>> > >>>>>> So far I found: > >>>>>> > >>>>>> > >>>>>> .subckt spark_gap 1 4 R_off 1 2 1e7 ; dark resistance > >>>>>> (affects breakdown voltage) R_ion 1 2 R=10/V(ion)**.75 ; > >>>>>> dynamic ionization resistance Dfall 2 3 10V ; bidirectional > >>>>>> cathode fall voltage Cdfall 2 3 50p Rser=100 ; for > >>>>>> convergence V_ion 3 4 0 ; current sense for behavioral > >>>>>> sources B_ion 0 ion I=I(V_ion)**2 ; measure of channel > >>>>>> ionization C_ion ion 0 5u Rpar=1 ; ionization time > >>>>>> constant .model 10V d(Vfwd=10 Vrev=10 Ron=1) .ends > >>>>>> spark_gap > >>>>>> > >>>>>> > >>>>>> However, the spark occurs at a few hundred volts and > >>>>>> changing parameters doesn't do much. > >>>>> > >>>>> A spark plug breaks over at about 20kV. It's an avalanche > >>>>> breakdown in compressed gas, so you have to have a free > >>>>> charge carrier show up to initiate the the avalanche. Car > >>>>> cylinders are dirty places, so it might be a chunk of soot. > >>>>> > >>>>> The currents involved in the established avalanche would be > >>>>> high enough to sustain an arc if it went on for long enough, > >>>>> but you have an initial glow discharge with a voltage drop of > >>>>> a hundred volts or so for perhaps a microsecond before the > >>>>> ion bombardment gets one electrode surface hot enough to > >>>>> allow the arc mechanism to take over - which is to say to let > >>>>> the surface get hot enough into distort under the influence > >>>>> of the applied electric field to create lots of atomically > >>>>> sharp spikes that emit electrons by "warm" field emission. > >>>>> > >>>>> Best of luck modelling that in Spice. > >>>>> > >>>>> The presence and absence of fuel make a difference to the > >>>>> multiplication process that forms the initial spark, so the > >>>>> initial breakdown voltage is going to be different, and it > >>>>> influences the glow discharge period when the discharge moves > >>>>> from a glow to an arc. Once the arc is established the fuel > >>>>> content doesn't make any difference. > >>>>> > >>>>> A friend of mine set up a laser system for looking at the gas > >>>>> flows inside a single cylinder test engine for Shell in the > >>>>> later 1970's, but he was more worried about the combustion > >>>>> initiated by the spark than the spark itself. > >>>> > >>>> One car I had with points & coil produced around 6kV for > >>>> sparkplugs IIRC, nothing like 20kV > >>>> > >>>> > >>>> NT > >>> > >>> What brand? In air, or under compression? ...Jim Thompson > >> > >> Lada, late 1960s design. 6-7kV at idle. AIUI figures like 20kV are > >> more associated with electronic ignition, but it's not an area of > >> expertise for me. Measured by an adjustable spark gap in open air, > >> that was measuring the max V_out the coil could produce. So it > >> can't have delivered more to the compressed cylinder content - must > >> have dlivered less in fact. > >> > >> > >> NT > > > > That voltage is _after_ the HV finally breaks-over. ...Jim Thompson > > > > On Russian-made cars you never know. I remember one journalist who was > transferred to Russia who reported about his experience when buying a > car there. They had exactly three cars at the dealership, all the same > type Lada (essentially a copy of an older Fiat model), in three > different colors. Two wouldn't start and the third had a flat tire (in > the show room!). So they bought the one with the flat tire. >https://youtu.be/mIAYxWCXF8A East Germany but close enough ;)
Reply by ●June 6, 20182018-06-06
Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:> onsdag den 6. juni 2018 kl. 21.38.54 UTC+2 skrev Steve Wilson: >> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>> > at idle and low loads there isn't much pressure>> Q: Why should there be any difference? The compression ratio doesn't >> change. When you measure the cylinder compression, it is a static >> measurement at low rpm. The engine is cranked over by the starter. >> Variations between cylinders indicates leakage from intake or exhaust >> valves or worn rings, or a blown head gasket.> because the throttle is closed so the manifold is at vacuum. When doing > compression test you need the throttle wide openThe throttle is not completely closed. It is at idle. Plenty of air enters the cylinder to measure the compression.>> High loads means more fuel and air enters the cylinders. If the >> cylinder pressure increased, it would start acting as a diesel. This is >> called knock and can be very destructive. Most cars have a knock sensor >> to prevent damage.>> Also, diesel engines idle fine. This means the cylinder pressure is >> adequate to ignite the fuel. Why should it change at operating rpm?> diesel engines don't throttle the air they just meter the fuelYes. You havn't explained why the cylinder pressure is low at idle.
Reply by ●June 6, 20182018-06-06
onsdag den 6. juni 2018 kl. 22.24.11 UTC+2 skrev Steve Wilson:> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: > > > onsdag den 6. juni 2018 kl. 21.38.54 UTC+2 skrev Steve Wilson: > >> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: > > >> > at idle and low loads there isn't much pressure > > >> Q: Why should there be any difference? The compression ratio doesn't > >> change. When you measure the cylinder compression, it is a static > >> measurement at low rpm. The engine is cranked over by the starter. > >> Variations between cylinders indicates leakage from intake or exhaust > >> valves or worn rings, or a blown head gasket. > > > because the throttle is closed so the manifold is at vacuum. When doing > > compression test you need the throttle wide open > > The throttle is not completely closed. It is at idle. Plenty of air enters > the cylinder to measure the compression.read the manual for a compression tester some time> > >> High loads means more fuel and air enters the cylinders. If the > >> cylinder pressure increased, it would start acting as a diesel. This is > >> called knock and can be very destructive. Most cars have a knock sensor > >> to prevent damage. > > >> Also, diesel engines idle fine. This means the cylinder pressure is > >> adequate to ignite the fuel. Why should it change at operating rpm? > > > diesel engines don't throttle the air they just meter the fuel > > Yes. You havn't explained why the cylinder pressure is low at idle.I did, on a gasoline engine the throttle is closed so very little air enters the cylinder it has be that way to get the right fuel/air ratio Diesel engines don't have a throttles but they don't have ignition either
Reply by ●June 6, 20182018-06-06
On 2018-06-06 12:59, Phil Hobbs wrote:> On 06/06/2018 03:54 PM, Joerg wrote: >> On 2018-06-06 12:50, Jim Thompson wrote: >>> On Wed, 6 Jun 2018 11:29:26 -0700 (PDT), tabbypurr@gmail.com wrote: >>> >>>> On Wednesday, 6 June 2018 19:19:17 UTC+1, Jim Thompson wrote: >>>>> On Wed, 6 Jun 2018 11:08:36 -0700 (PDT), tabbypurr wrote: >>>>>> On Wednesday, 6 June 2018 03:35:48 UTC+1, bill....@ieee.org >>>>>> wrote: >>>>>>> On Wednesday, June 6, 2018 at 9:09:35 AM UTC+10, Joerg >>>>>>> wrote: >>>>>> >>>>>>>> Looking for a SPICE model that mimics a spark plug, ideally >>>>>>>> with and without fuel. Does anyone know where to find one? >>>>>>>> >>>>>>>> So far I found: >>>>>>>> >>>>>>>> >>>>>>>> .subckt spark_gap 1 4 R_off 1 2 1e7 ; dark resistance >>>>>>>> (affects breakdown voltage) R_ion 1 2 R=10/V(ion)**.75 ; >>>>>>>> dynamic ionization resistance Dfall 2 3 10V ; bidirectional >>>>>>>> cathode fall voltage Cdfall 2 3 50p Rser=100 ; for >>>>>>>> convergence V_ion 3 4 0 ; current sense for behavioral >>>>>>>> sources B_ion 0 ion I=I(V_ion)**2 ; measure of channel >>>>>>>> ionization C_ion ion 0 5u Rpar=1 ; ionization time >>>>>>>> constant .model 10V d(Vfwd=10 Vrev=10 Ron=1) .ends >>>>>>>> spark_gap >>>>>>>> >>>>>>>> >>>>>>>> However, the spark occurs at a few hundred volts and >>>>>>>> changing parameters doesn't do much. >>>>>>> >>>>>>> A spark plug breaks over at about 20kV. It's an avalanche >>>>>>> breakdown in compressed gas, so you have to have a free >>>>>>> charge carrier show up to initiate the the avalanche. Car >>>>>>> cylinders are dirty places, so it might be a chunk of soot. >>>>>>> >>>>>>> The currents involved in the established avalanche would be >>>>>>> high enough to sustain an arc if it went on for long enough, >>>>>>> but you have an initial glow discharge with a voltage drop of >>>>>>> a hundred volts or so for perhaps a microsecond before the >>>>>>> ion bombardment gets one electrode surface hot enough to >>>>>>> allow the arc mechanism to take over - which is to say to let >>>>>>> the surface get hot enough into distort under the influence >>>>>>> of the applied electric field to create lots of atomically >>>>>>> sharp spikes that emit electrons by "warm" field emission. >>>>>>> >>>>>>> Best of luck modelling that in Spice. >>>>>>> >>>>>>> The presence and absence of fuel make a difference to the >>>>>>> multiplication process that forms the initial spark, so the >>>>>>> initial breakdown voltage is going to be different, and it >>>>>>> influences the glow discharge period when the discharge moves >>>>>>> from a glow to an arc. Once the arc is established the fuel >>>>>>> content doesn't make any difference. >>>>>>> >>>>>>> A friend of mine set up a laser system for looking at the gas >>>>>>> flows inside a single cylinder test engine for Shell in the >>>>>>> later 1970's, but he was more worried about the combustion >>>>>>> initiated by the spark than the spark itself. >>>>>> >>>>>> One car I had with points & coil produced around 6kV for >>>>>> sparkplugs IIRC, nothing like 20kV >>>>>> >>>>>> >>>>>> NT >>>>> >>>>> What brand? In air, or under compression? ...Jim Thompson >>>> >>>> Lada, late 1960s design. 6-7kV at idle. AIUI figures like 20kV are >>>> more associated with electronic ignition, but it's not an area of >>>> expertise for me. Measured by an adjustable spark gap in open air, >>>> that was measuring the max V_out the coil could produce. So it >>>> can't have delivered more to the compressed cylinder content - must >>>> have dlivered less in fact. >>>> >>>> >>>> NT >>> >>> That voltage is _after_ the HV finally breaks-over. ...Jim Thompson >>> >> >> On Russian-made cars you never know. I remember one journalist who was >> transferred to Russia who reported about his experience when buying a >> car there. They had exactly three cars at the dealership, all the same >> type Lada (essentially a copy of an older Fiat model), in three >> different colors. Two wouldn't start and the third had a flat tire (in >> the show room!). So they bought the one with the flat tire. >> > > It was a copy of a Fiat 124 sedan, including the reliability. LADA is a > Russian acronym for "Fix it again, Ivan". ;) >A friend's brother had the station wagon from Lada. It came standard with a crowbar included. IIIRC the car gave him a lot of grief. https://en.wikipedia.org/wiki/VAZ-2101#/media/File:Lada_Riva_estate_Cambridge.jpg Meantime Fiat had moved on to more modern cars but those could have issues as well. A friend had Fiat Mirafiori (131?) station wagon and he called his "Mirafrusti". -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●June 6, 20182018-06-06
On 06/06/2018 20:59, Phil Hobbs wrote:> On 06/06/2018 03:54 PM, Joerg wrote: >> On 2018-06-06 12:50, Jim Thompson wrote: >>> On Wed, 6 Jun 2018 11:29:26 -0700 (PDT), tabbypurr@gmail.com wrote: >>> >>>> On Wednesday, 6 June 2018 19:19:17 UTC+1, Jim Thompson wrote: >>>>> On Wed, 6 Jun 2018 11:08:36 -0700 (PDT), tabbypurr wrote: >>>>>> On Wednesday, 6 June 2018 03:35:48 UTC+1, bill....@ieee.org >>>>>> wrote: >>>>>>> On Wednesday, June 6, 2018 at 9:09:35 AM UTC+10, Joerg >>>>>>> wrote: >>>>>> >>>>>>>> Looking for a SPICE model that mimics a spark plug, ideally >>>>>>>> with and without fuel. Does anyone know where to find one? >>>>>>>> >>>>>>>> So far I found: >>>>>>>> >>>>>>>> >>>>>>>> .subckt spark_gap 1 4 R_off 1 2 1e7 ; dark resistance >>>>>>>> (affects breakdown voltage) R_ion 1 2 R=10/V(ion)**.75 ; >>>>>>>> dynamic ionization resistance Dfall 2 3 10V ; bidirectional >>>>>>>> cathode fall voltage Cdfall 2 3 50p Rser=100 ; for >>>>>>>> convergence V_ion 3 4 0 ; current sense for behavioral >>>>>>>> sources B_ion 0 ion I=I(V_ion)**2 ; measure of channel >>>>>>>> ionization C_ion ion 0 5u Rpar=1 ; ionization time >>>>>>>> constant .model 10V d(Vfwd=10 Vrev=10 Ron=1) .ends >>>>>>>> spark_gap >>>>>>>> >>>>>>>> >>>>>>>> However, the spark occurs at a few hundred volts and >>>>>>>> changing parameters doesn't do much. >>>>>>> >>>>>>> A spark plug breaks over at about 20kV. It's an avalanche >>>>>>> breakdown in compressed gas, so you have to have a free >>>>>>> charge carrier show up to initiate the the avalanche. Car >>>>>>> cylinders are dirty places, so it might be a chunk of soot. >>>>>>> >>>>>>> The currents involved in the established avalanche would be >>>>>>> high enough to sustain an arc if it went on for long enough, >>>>>>> but you have an initial glow discharge with a voltage drop of >>>>>>> a hundred volts or so for perhaps a microsecond before the >>>>>>> ion bombardment gets one electrode surface hot enough to >>>>>>> allow the arc mechanism to take over - which is to say to let >>>>>>> the surface get hot enough into distort under the influence >>>>>>> of the applied electric field to create lots of atomically >>>>>>> sharp spikes that emit electrons by "warm" field emission. >>>>>>> >>>>>>> Best of luck modelling that in Spice. >>>>>>> >>>>>>> The presence and absence of fuel make a difference to the >>>>>>> multiplication process that forms the initial spark, so the >>>>>>> initial breakdown voltage is going to be different, and it >>>>>>> influences the glow discharge period when the discharge moves >>>>>>> from a glow to an arc. Once the arc is established the fuel >>>>>>> content doesn't make any difference. >>>>>>> >>>>>>> A friend of mine set up a laser system for looking at the gas >>>>>>> flows inside a single cylinder test engine for Shell in the >>>>>>> later 1970's, but he was more worried about the combustion >>>>>>> initiated by the spark than the spark itself. >>>>>> >>>>>> One car I had with points & coil produced around 6kV for >>>>>> sparkplugs IIRC, nothing like 20kV >>>>>> >>>>>> >>>>>> NT >>>>> >>>>> What brand? In air, or under compression? ...Jim Thompson >>>> >>>> Lada, late 1960s design. 6-7kV at idle. AIUI figures like 20kV are >>>> more associated with electronic ignition, but it's not an area of >>>> expertise for me. Measured by an adjustable spark gap in open air, >>>> that was measuring the max V_out the coil could produce. So it >>>> can't have delivered more to the compressed cylinder content - must >>>> have dlivered less in fact. >>>> >>>> >>>> NT >>> >>> That voltage is _after_ the HV finally breaks-over. ...Jim Thompson >>> >> >> On Russian-made cars you never know. I remember one journalist who was >> transferred to Russia who reported about his experience when buying a >> car there. They had exactly three cars at the dealership, all the same >> type Lada (essentially a copy of an older Fiat model), in three >> different colors. Two wouldn't start and the third had a flat tire (in >> the show room!). So they bought the one with the flat tire. >> > > It was a copy of a Fiat 124 sedan, including the reliability. LADA is a > Russian acronym for "Fix it again, Ivan". ;)The only common element was the body, all the running gear and interior was of Russian origin. Remarkable story about reliability. My experience (1970s) was very different. They were built like the proverbial, designed for cart tracks and a bullet proof engine too. They had chain driven overhead cam with a 5 bearing camshaft. The only backward part was the alternator had an external vibrating reed style regulator! -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Reply by ●June 6, 20182018-06-06
On 06/06/2018 04:24 PM, Steve Wilson wrote:> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: > >> onsdag den 6. juni 2018 kl. 21.38.54 UTC+2 skrev Steve Wilson: >>> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: > >>>> at idle and low loads there isn't much pressure > >>> Q: Why should there be any difference? The compression ratio doesn't >>> change. When you measure the cylinder compression, it is a static >>> measurement at low rpm. The engine is cranked over by the starter. >>> Variations between cylinders indicates leakage from intake or exhaust >>> valves or worn rings, or a blown head gasket. > >> because the throttle is closed so the manifold is at vacuum. When doing >> compression test you need the throttle wide open > > The throttle is not completely closed. It is at idle. Plenty of air enters > the cylinder to measure the compression. > >>> High loads means more fuel and air enters the cylinders. If the >>> cylinder pressure increased, it would start acting as a diesel. This is >>> called knock and can be very destructive. Most cars have a knock sensor >>> to prevent damage. > >>> Also, diesel engines idle fine. This means the cylinder pressure is >>> adequate to ignite the fuel. Why should it change at operating rpm? > >> diesel engines don't throttle the air they just meter the fuel > > Yes. You havn't explained why the cylinder pressure is low at idle. >The manifold is at vacuum because the engine is having to pump the air past the closed throttle. If you have 15 inches of manifold vacuum, your 8:1 or 12:1 or whatever compression ratio produces only 17/32 of the peak pressure that it would with the throttle wide open. Ratio is the same, intake pressure is less -> peak pressure is less. That's why cars in neutral don't idle at the rev limit. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
