SPICE model for a spark plug?

Are you saying the cylinder compression pressure only varies ~2:1 between idle and full throttle?

I'm pretty sure the idle control system sets the idle rpm.

Reply to
Steve Wilson
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At 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 to
tabbypurr

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 
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Reply to
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.

NT

Reply to
tabbypurr

manifold pressure, air entering the cylinder is manifold pressure times volumetric efficiency, and that varies with 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 to
Lasse Langwadt Christensen

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 to
Lasse Langwadt Christensen

And more recently Egypt:

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Mike Perkins 
Video Solutions Ltd 
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Reply to
Mike Perkins

Untested 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,
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    310-216-1144, snipped-for-privacy@AENG.com
*

hummmmm. 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, snipped-for-privacy@anasoft.co.uk
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*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

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- SuperSpice
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Reply to
Kevin Aylward

Though the 110 is a different car

NT

Reply to
tabbypurr

The 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 :-).

Reply to
glen walpert

The issue with the syntax is the line that starts ")}". This is a continuation line, and should be preceded by "+". Alternatively if you remove the line break and terminate the previous line "> {I_ARC}, 12,0,)}" the spice model will run. Good luck.

Reply to
aran admin

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