SPICE model for a spark plug?

[Joerg]

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.

--
Regards, Joerg

http://www.analogconsultants.com/

[John Larkin]

On Tue, 05 Jun 2018 16:09:34 -0700, Joerg <ne...@analogconsultants.com>
wrote:

I thought your dirt bike had pedals.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[bill....@ieee.org]

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.

--
Bill Sloman, Sydney

[Klaus Kragelund]

Wouldn't be better to "just" run a test, and feed the voltage/current waveform into spice?

Cheers

Klaus

[Joerg]

Yes, but this isn't an engine application and testing would not be easy
at all. Or not really possible a priori.

[Joerg]

It's for something way bigger :-)

[Joerg]

On 2018-06-05 19:35, 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.
>

It also works fine in clean air.

> 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 current (100-200mA), duration and so on are well know. I could
probably piece together a behavioral model but I am not very good at
that and thought that I sure can't be the first one. But maybe I am.

> 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.
>

Yes, different job.

[Jim Thompson]

Break-over depends on risetime as well as voltage. I may have a
model. Cross fingers.

...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

[Jim Thompson]

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,
www.AENG.com, 310-216-1144, In...@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
.ends

[Joerg]

Thank you. LTSpice doesn't like this line though:

E_EARC_CONTROL 8 0 VALUE = { IF( ABS(I(V_VSENSE)) > {I_ARC} , 12 , 0
)}

It complains about the "extra" curly brace at the end which to me seems
correct, not "extra". If I take it out LTPSICE, of course, complains
about a missing curly brace. Software really isn't my thing. Or maybe
there is a bug somewhere.

Meantime I found a nice article about spark gap modeling using the
Rompe-Weizel formula but it's complicated:

http://www.bordsysteme.tu-dortmund.de/publications/2000_IEEE_Transactions_Computer%20Simulation%20of%20ESD%20from%20Voluminous%20Objects.pdf

Now I've got to take care of a production line stop situation. Those are
always fun. Grumble.

[tabb...@gmail.com]

One car I had with points & coil produced around 6kV for sparkplugs IIRC, nothing like 20kV


NT

[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.

Nothing is ever simple.

Mark

[Jim Thompson]

What brand? In air, or under compression?

[tabb...@gmail.com]

On Wednesday, 6 June 2018 19:19:17 UTC+1, Jim Thompson wrote:

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

[Lasse Langwadt Christensen]

at idle and low loads there isn't much pressure

[Lasse Langwadt Christensen]

many cars run wasted spark with two plugs in series

[Joerg]

The redneck solution would have been to strap a piece of wood across the
area and lash that one plug connector to it so that it just fires, and
call it a day. "Hey look, I fixed it!".

[Johnny B Good]

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). The effect with old fashioned
Kettering ignition (whether transistorised or not) on fouled plugs is
merely an unexpected bonus.

If you want a more foulproof system, the obvious way is to remove the
dependence on coil inductance as the HT generating mechanism (flyback
pulse mode) and use the coil purely as a step up transformer to the
instant application of a 400v charge from a capacitor connected in series
with the LT winding across a quenchable dc-dc converter which can be
briefly shorted out via a thyristor which arrangement allows one full
cycle of ac energy to be applied to produce some 30 to 40 kilovolts from
the bare coil, reduced by the actual cylinder pressure at the spark plug
points (circa 6KV at tickover to 20 or so KV at full throttle maximum
torque revs).

There isn't a flyback pulse mechanism for fouling induced leakage
resistance to interfere with since the coil is just used as a voltage
step up transformer in this case. The leakage due to plug fouling may
knock a few kilovolts off the 40KV unloaded coil output but this won't
stop the plug sparking at the lower breakdown voltage circa 20KV or so
required to ignite the air fuel mixture.

The importance of the circuit topology, capacitor charged via the coil's
LT winding by the output of a quenchable dc-dc converter which is shorted
out by the thyristor, is that it allows the current in the capacitor to
reverse via the converter's output rectifier bridge after it hits the
positive peak, allowing for a negative voltage peak on the 2nd half of
the full cycle which recharges the capacitor up to somewhere in the
region of 70 to 80 percent of its initial voltage by which time the
thyristor has unlatched and the converter restarts to top up the
capacitor in plenty of time for the next sparking pulse.

Replacing the function of the CB points in the old Kettering setup with
a high voltage switching transistor is so last century (and, oh so shit).

--
Johnny B Good

[Steve Wilson]

Lasse Langwadt Christensen <lang...@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.

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?

[Lasse Langwadt Christensen]

onsdag den 6. juni 2018 kl. 21.38.54 UTC+2 skrev Steve Wilson:
> Lasse Langwadt Christensen <lang...@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

>
> 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

[Lasse Langwadt Christensen]

I know

[Jim Thompson]

That voltage is _after_ the HV finally breaks-over.

[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.

[Phil Hobbs]

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

[Lasse Langwadt Christensen]

https://youtu.be/mIAYxWCXF8A East Germany but close enough ;)

[Steve Wilson]

Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

> onsdag den 6. juni 2018 kl. 21.38.54 UTC+2 skrev Steve Wilson:
>> Lasse Langwadt Christensen <lang...@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.

[Lasse Langwadt Christensen]

onsdag den 6. juni 2018 kl. 22.24.11 UTC+2 skrev Steve Wilson:
> Lasse Langwadt Christensen <lang...@fonz.dk> wrote:
>
> > onsdag den 6. juni 2018 kl. 21.38.54 UTC+2 skrev Steve Wilson:
> >> Lasse Langwadt Christensen <lang...@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

[Joerg]

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".

[Mike Perkins]

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

[Phil Hobbs]

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.

[Steve Wilson]

Throttle. Throttle. Throttle. It doesn't matter if the compression ratio
is constant. If you don't have much air to being with, you won't get much
pressure at the end.

Smarter every day. Anything I can do to keep my car away from Candian Tire
is good.

Good discussion. Thanks.

[tabb...@gmail.com]

On Wednesday, 6 June 2018 20:50:48 UTC+1, Jim Thompson wrote:

> On Wed, 6 Jun 2018 11:29:26 -0700 (PDT), tabbypurr 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:

> >> >One car I had with points & coil produced around 6kV for sparkplugs IIRC, nothing like 20kV

> >> 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

It was incapable of jumping the gap at all at any wider spacing, so around 6kV was the _peak_ output.


NT

[Jim Thompson]

On Wed, 06 Jun 2018 09:40:06 -0700, Jim Thompson

Phil, This is from LTspice Digest #9378:

"Spark Gap

Sun Jun 3, 2018 4:54 am (PDT) . Posted by:

bordodynov

Hello.
I developed the arrester models based on the model from
analogspiceman. I added inertia, i.e. depending on the speed of the
voltage supply, the breakdown voltage changes.
I developed (based on the datasheet) the EM90X, EM230X, EM300X,
EM350X, EM400XG, EM550X and EM3000XB models. I would like to expand
this list with other arresters. Please indicate the types of surge
arresters that models are desirable to have.

Bordodynov. "

Check out the "files" section to get the model (I'd guess).

[tabb...@gmail.com]

On Wednesday, 6 June 2018 21:00:00 UTC+1, Phil Hobbs wrote:
> On 06/06/2018 03:54 PM, Joerg wrote:
> > On 2018-06-06 12:50, Jim Thompson wrote:

No, it wasn't. The body was a reinforced Fiat 124, the rest was mostly Russian. The Lada is unusual in having a lot of misinformation about it out there.


NT

[tabb...@gmail.com]

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.


NT

[tabb...@gmail.com]

I've never seen one come with a crowbar. Do you mean a starting handle? They had those, being designed to operate in Siberian temperatures & offroad in the Russian climate, where inability to start the car was sometimes life-threatening.


NT

[Joerg]

Not a crank like my Citroen 2CV had. It looked like a giant tire iron
which was easily suitable to break down a locked front door.

[Joerg]

Are they still building them in Egypt?

[Steve Wilson]

Steve Wilson <n...@spam.com> wrote:

> Throttle. Throttle. Throttle. It doesn't matter if the compression ratio
> is constant. If you don't have much air to being with, you won't get much
> pressure at the end.

being with -> Begin with

[tabb...@gmail.com]

On Thursday, 7 June 2018 00:22:44 UTC+1, Joerg wrote:

I can't remember. The relevant company is Bogdan IIRC. ISTR they put weird door handles on them.


NT

[Steve Wilson]

Phil Hobbs <pcdhSpamM...@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

[tabb...@gmail.com]

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

[Phil Hobbs]

On 06/06/2018 10:14 PM, Steve Wilson wrote:
> Phil Hobbs <pcdhSpamM...@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.

[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 <pcdhSpamM...@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.


NT

[Lasse Langwadt Christensen]

torsdag den 7. juni 2018 kl. 04.14.10 UTC+2 skrev Steve Wilson:
> Phil Hobbs <pcdhSpamM...@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

[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

[Mike Perkins]

And more recently Egypt:
https://en.wikipedia.org/wiki/Lada_110

[Kevin Aylward]

"Jim Thompson" wrote in message
news:ve3ghd58bbiklvo90...@4ax.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, ke...@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

[tabb...@gmail.com]

On Thursday, 7 June 2018 19:57:52 UTC+1, Mike Perkins wrote:

Though the 110 is a different car


NT

[glen walpert]

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 :-).

[Steve Wilson]

glen walpert <nos...@null.void> wrote:

> 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 :-).

My first car was an English Anglia. Instead of blinking turn signals, it had
two levers that swung out from either side that illuminated to show the
direction of turn. These were a constant pain to maintain.

Removing the transmission to change the clutch was a bit more of a pain. I
had to lift the car on jacks, slide underneath, then remove all the bolts to
lift the transmission out.

Later, when I started taking girls on dates and they told me they were horny,
I could not believe that they would say such a thing in my car, which I
regarded as sacred. It took me many years before I discovered my mistake.

[aran admin]

> ...Jim Thompson

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.