Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:> 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.Are you saying the cylinder compression pressure only varies ~2:1 between idle and full throttle?> That's why cars in neutral don't idle at the rev limit.I'm pretty sure the idle control system sets the idle rpm.> Cheers> Phil Hobbs
SPICE model for a spark plug?
Started by ●June 5, 2018
Reply by ●June 6, 20182018-06-06
Reply by ●June 7, 20182018-06-07
On Thursday, 7 June 2018 03:14:10 UTC+1, Steve Wilson wrote:> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > 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. > > Are you saying the cylinder compression pressure only varies ~2:1 between > idle and full throttle? > > > That's why cars in neutral don't idle at the rev limit. > > I'm pretty sure the idle control system sets the idle rpm. > > > Cheers > > > Phil HobbsAt idle very little petrol/air mix is let into the cylinder, so when compressed it's only a fraction of the pressure of a compressed pedal-to-the-floor fill. It's engine basics stuff. NT
Reply by ●June 7, 20182018-06-07
On 06/06/2018 10:14 PM, Steve Wilson wrote:> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> 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. > > Are you saying the cylinder compression pressure only varies ~2:1 between > idle and full throttle?It's probably a good bit more than that. Point is the physics, which I gather you now understand. 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 7, 20182018-06-07
On Thursday, 7 June 2018 14:31:02 UTC+1, Phil Hobbs wrote:> On 06/06/2018 10:14 PM, Steve Wilson wrote: > > Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > >> 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. > > > > Are you saying the cylinder compression pressure only varies ~2:1 between > > idle and full throttle? > > It's probably a good bit more than that. Point is the physics, which I > gather you now understand. > > Cheers > > Phil HobbsThe ratio of power produced at full pelt versus idle is what... I don't recall, but certainly more than 20:1. Fuel consumption ditto. So I wouldn't expect unignited compressed fill at idle to even reach atmospheric pressure. NT
Reply by ●June 7, 20182018-06-07
torsdag den 7. juni 2018 kl. 04.14.10 UTC+2 skrev Steve Wilson:> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > 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. > > Are you saying the cylinder compression pressure only varies ~2:1 between > idle and full throttle?manifold pressure, air entering the cylinder is manifold pressure times volumetric efficiency, and that varies with rpm> > > That's why cars in neutral don't idle at the rev limit. > > I'm pretty sure the idle control system sets the idle rpm.that is just a technicality, in the simplest case that is just an end stop that prevents the throttle from closing all the way
Reply by ●June 7, 20182018-06-07
torsdag den 7. juni 2018 kl. 16.28.30 UTC+2 skrev tabb...@gmail.com:> On Thursday, 7 June 2018 14:31:02 UTC+1, Phil Hobbs wrote: > > On 06/06/2018 10:14 PM, Steve Wilson wrote: > > > Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > > > >> 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. > > > > > > Are you saying the cylinder compression pressure only varies ~2:1 between > > > idle and full throttle? > > > > It's probably a good bit more than that. Point is the physics, which I > > gather you now understand. > > > > Cheers > > > > Phil Hobbs > > The ratio of power produced at full pelt versus idle is what... I don't recall, but certainly more than 20:1. Fuel consumption ditto. So I wouldn't expect unignited compressed fill at idle to even reach atmospheric pressure. >I looked up some numbers, 2liter engine, ~450gr/h gasoline at idle 0.450gr*14.7 = 6.6kg/h air 6.6kg/1.15kg/m^3 = 5.74m^3/h air 5740/60 = 95 liter/minute 95liter/750rpm = 0.12 liter/revolution 0.12 times a compression ratio of 9:1 is roughly 1 bar ignoring all the details
Reply by ●June 7, 20182018-06-07
On 07/06/2018 02:04, tabbypurr@gmail.com wrote:> On Thursday, 7 June 2018 00:22:44 UTC+1, Joerg wrote: >> On 2018-06-06 16:02, tabbypurr wrote: >>> On Wednesday, 6 June 2018 21:19:54 UTC+1, Lasse Langwadt Christensen >>> wrote: >>>> onsdag den 6. juni 2018 kl. 21.54.48 UTC+2 skrev Joerg: >>> >>>>> 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 ;) >>> >>> The Trabi was a 1950s economy car, a very different animal. Plastic >>> body, 2 stroke engine with 5 moving parts, no fuel gauge etc. >>> >>> The Lada was a good car when it came out. But it kept being >>> manufactured about 40 years. >>> >> >> Are they still building them in Egypt? > > I can't remember. The relevant company is Bogdan IIRC. ISTR they put weird door handles on them.And more recently Egypt: https://en.wikipedia.org/wiki/Lada_110 -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Reply by ●June 7, 20182018-06-07
"Jim Thompson" wrote in message news:ve3ghd58bbiklvo908gqo8f115spmc9os1@4ax.com... On Wed, 06 Jun 2018 08:52:05 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Wed, 6 Jun 2018 02:41:47 -0700 (PDT), Klaus Kragelund ><klauskvik@hotmail.com> wrote: > >>On Wednesday, June 6, 2018 at 1:09:35 AM UTC+2, 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. >>> >>> -- >>Wouldn't be better to "just" run a test, and feed the voltage/current >>waveform into spice? >> >>Cheers >> >>Klaus > >Break-over depends on risetime as well as voltage. I may have a >model. Cross fingers. > > ...Jim ThompsonUntested by JET. It has the odor of an LTspice model, so behavior and convergence are automatically suspect >:-) .SUBCKT SPARK_GAP2 1 2 PARAMS: V_GLOW=1500 V_ARC=150 I_SUS=.002 V_BREAKDN=12000 I_ARC=.2 * SINCE THE STRIKING IS VERY FAST, IT IS STRONGLY ADVISED * TO SET TRTOL TO 1 VIA: .OPTIONS TRTOL=1 and ITL4=1000. THIS WILL FORCE * PSpice TO BE MORE VIGILANT IN THE VICINITY OF TRANSITIONS * * Documentation on the Sparkgap model can obtained from AEi Systems, www.AENG.com, 310-216-1144, Info@AENG.com *>D_D3 10 11 DZ_ARC >X_SARC 9 0 3 10 SPARK_GAP2_SARC >R_RT1 7 0 50 >D_DT2 8 9 D1N4148 >E_EBREAKDN_CONTROL 6 0 VALUE = {IF(ABS(V(1,2))>{V_BREAKDN} , 12 , >+ IF( ABS(I(V_VSENSE)) > {I_SUS} , 12 , 0 ))} >D_D4 5 11 DZ_ARC >E_EARC_CONTROL 8 0 VALUE = { IF( ABS(I(V_VSENSE)) > {I_ARC} , 12 , 0 >)} >D_D2 5 4 DZ_GLOW >V_VSENSE 5 2 DC 0 >C_CT2 9 0 0.1U >R_RT2 9 0 50 >C_CT1 7 0 0.25U >X_SBREAKDN 7 0 1 3 SPARK_GAP2_SBREAKDN >D_D1 3 4 DZ_GLOW >D_DT1 6 7 D1N4148 >.MODEL DZ_GLOW D (BV={V_GLOW} IS=1U RS=5 IBV=10U) >.MODEL DZ_ARC D (BV={V_ARC} IS=1U RS=5 IBV=10U) >.MODEL D1N4148 D (RS=.8 CJO=4PF IS=7E-09 N=2 VJ=.6V >+ TT=6E-09 M=.45 BV=100V) >.ENDS >.subckt SPARK_GAP2_SARC 1 2 3 4 >XS_SBREAKDN 3 4 1 2 SWhyste Params: Ron=5 Roff=50MEG VT=10 VH=0 >RS_SARC 1 2 1G >.ends >.subckt SPARK_GAP2_SBREAKDN 1 2 3 4 >XS_SBREAKDN 3 4 1 2 SWhyste Params: Ron=5 Roff=50MEG VT=10 VH=0 >RS_SBREAKDN 1 2 1G >.endshummmmm. Haven't thought about spark plugs before. Another idea.... If they behave like CCFL, i.e. strike voltage than v fall, then my CCFL.sss SuperSpice download example might be of use. .SUBCKT CCFL_XN !0_1 !1_10 * V!1 !1_10 10 0 V!0 !0_1 1 0 * (c) Kevin Aylward 2002 - All rights reserved, kevin@anasoft.co.uk www.anasoft.co.uk *Generic Cold Cathode Floresent Lamp model * This model may be freely copied and used, provided this copyright notice is included *The model is based on, where G is the instaneous conductance, *I=G(V,I)*V and dG/dt = aI^2 +b(I/V)^2 + f(I/V) * the most general model is dG/dt = aI^2 + kIV + cV^2 + d(I/V)^3 +b(I/V)^2 + f(I/V) *Note: UIC "use initial conditions" in transient setup must be used *The tanh, divide and multiple by 1000 is to from a convergence limiter to 1000 amps B2 1 3 i=1000*tanh(v(1,2)*v(4)/1000) v1 3 2 dc 0 c1 4 0 1 ic=.001 *integrator time constant resistor, ideal is very large, however make it as small as the specific circuit allows r1 4 0 0.1 *change the numerical constants to change the on characteristics *core ccfl equation b1 4 0 i=-(2.5*I(v1)^2 - 5.0e4*(I(v1)/v(1,2))^2 + 275.0*I(v1)/v(1,2)) cstray 1 10 100p rleak 1 10 10Meg * *strike control, r diode and c controls turn on time, rrect and c controls turn off time *full wave rectifier, will keep switch on unless frequency falls too low b3 s_1 0 v=abs(v(1,10)) s1 10 2 s_2 0 ccfl_switch Cconverge 10 2 10p d1 s_1 s_2 diode rrect s_2 0 500k cton s_2 0 0.5e-6 .model diode d(rs=1k) * *sets the strike voltage and holding voltage. Vstrike=vt+vh Vhold=vt-vh .model ccfl_switch sw(ron=1 roff=100e6 vh=100 vt=300) * *these clamps are not used in ordinary operation d3 1 12 ccfc_clamp_diode d4 1 12 ccfc_clamp_diode * .model ccfc_clamp_diode d(rs=1 bv=750) .ends I got the basics of this one from my bible "The Spice Book" -- Kevin Aylward http://www.anasoft.co.uk - SuperSpice http://www.kevinaylward.co.uk/ee/index.html
Reply by ●June 7, 20182018-06-07
On Thursday, 7 June 2018 19:57:52 UTC+1, Mike Perkins wrote:> On 07/06/2018 02:04, tabbypurr wrote: > > On Thursday, 7 June 2018 00:22:44 UTC+1, Joerg wrote: > >> On 2018-06-06 16:02, tabbypurr wrote: > >>> On Wednesday, 6 June 2018 21:19:54 UTC+1, Lasse Langwadt Christensen > >>> wrote: > >>>> onsdag den 6. juni 2018 kl. 21.54.48 UTC+2 skrev Joerg: > >>> > >>>>> 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 ;) > >>> > >>> The Trabi was a 1950s economy car, a very different animal. Plastic > >>> body, 2 stroke engine with 5 moving parts, no fuel gauge etc. > >>> > >>> The Lada was a good car when it came out. But it kept being > >>> manufactured about 40 years. > >>> > >> > >> Are they still building them in Egypt? > > > > I can't remember. The relevant company is Bogdan IIRC. ISTR they put weird door handles on them. > > And more recently Egypt: > https://en.wikipedia.org/wiki/Lada_110Though the 110 is a different car NT
Reply by ●June 7, 20182018-06-07
On Thu, 07 Jun 2018 07:39:21 -0700, Lasse Langwadt Christensen wrote:> torsdag den 7. juni 2018 kl. 04.14.10 UTC+2 skrev Steve Wilson: >> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >> > 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. >> >> Are you saying the cylinder compression pressure only varies ~2:1 >> between idle and full throttle? > > manifold pressure, air entering the cylinder is manifold pressure times > volumetric efficiency, and that varies with rpm > > >> > That's why cars in neutral don't idle at the rev limit. >> >> I'm pretty sure the idle control system sets the idle rpm. > > that is just a technicality, in the simplest case that is just an end > stop that prevents the throttle from closing all the wayThe idle control system on my 1961 Alfa Rojunko Spider was the usual stop screw, but it was adjustable by rotating the choke knob, which pulled out for choke. Regular adjustment was necessary. The car's best feature was however the convenient lifting lug at the balance point of the engine/ transmission combo for easy removal. I could get that engine out in under 30 minutes by the third or fourth time :-).
