Leaving the key on
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Leaving the key on =?ISO-8859-1?Q?Blattus_Slafaly 03-25-2008
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Posted by =?ISO-8859-1?Q?Blattus_Slafaly on March 25, 2008, 12:17 pm
In today's cars and bikes with electronic ignition and fuel injection,
does it hurt to leave the key on without starting the engine? Used to be
you could burn out the points or coil, don't have them any more. I
realize it will drain the battery flat if the lights come on too if left
on too long.



--
Blattus Slafaly ? 3 :) 7/8

Posted by oldgeezer on March 26, 2008, 5:17 pm
Blattus Slafaly 0/00 ? ? ? schreef:
> In today's cars and bikes with electronic ignition and fuel injection,
> does it hurt to leave the key on without starting the engine? Used to be
> you could burn out the points or coil, don't have them any more. I
> realize it will drain the battery flat if the lights come on too if left
> on too long.
>
>
>
> --
> Blattus Slafaly ? 3 :) 7/8

I was told the following:

The common ignition systems that use a coil, all work through the very
strange fact
that a variating magnetic field induces a voltage in a copper wire.
The faster it changes, the better the effect.

Variating a field can be done by switching the field ON, but also by
switching it OFF.

Switching off is the old fashioned point controlled system. That can
fry the coil
if you leave the key on, because all the time no spark is needed, a DC
current runs
through the primary winding.

There is an electronic version, that merely replaces the points with a
piece of electronics. That one fries the coil too.
Unfortunately many people call it a CDI, which it is not.

A CDI works by switching the field ON.
As long as there is no spark needed, the CDI unit fills a condenser to
about 400
Volts.
The 400 Volts are created by some solid state circuitry from the
original 12 Volts.
When the spark is needed, the condenser is discharged through the
coil, and
thus the spark is created.
This one will not fry the coil. Current only runs through the coil at
sparking time.


Coils of both types (points vs. CDI) differ.
The points type is built to let the magnetic field disappear asap,
while a coil for the CDI is built to create a magnetic field asap.

Rob.

Posted by The Older Gentleman on March 26, 2008, 5:33 pm

> Coils of both types (points vs. CDI) differ.
> The points type is built to let the magnetic field disappear asap,
> while a coil for the CDI is built to create a magnetic field asap.

That's interesting. I didn't know that.

OK, so what about coils for points ignition engines that have been
converted to electronic? I've never seen it stated that you must replace
the coils at the same time as fitting the electronic kit.

(Electrics and electronics are my blind spot)


--
BMW K1100LT Ducati 750SS Honda CB400F, SL125 & SH50
chateau dot murray at idnet dot com
"What you're proposing to do will involve a lot of time
and hassle for no tangible benefit."

Posted by oldgeezer on March 26, 2008, 6:07 pm
The Older Gentleman schreef:
>
> > Coils of both types (points vs. CDI) differ.
> > The points type is built to let the magnetic field disappear asap,
> > while a coil for the CDI is built to create a magnetic field asap.
>
> That's interesting. I didn't know that.
>
> OK, so what about coils for points ignition engines that have been
> converted to electronic? I've never seen it stated that you must replace
> the coils at the same time as fitting the electronic kit.
>
> (Electrics and electronics are my blind spot)
>
>
> --
> BMW K1100LT Ducati 750SS Honda CB400F, SL125 & SH50
> chateau dot murray at idnet dot com
> "What you're proposing to do will involve a lot of time
> and hassle for no tangible benefit."

Replacing points by a solid state switch means
that the system still is the cut_OFF_current type,
not the switch_current_ON type.
Thus there is no need to change the coil.

CDI=Condenser Discharge Ignition system

Rob.

Posted by The Older Gentleman on March 26, 2008, 6:18 pm

> Replacing points by a solid state switch means
> that the system still is the cut_OFF_current type,
> not the switch_current_ON type.
> Thus there is no need to change the coil.

I have to say, I know nothing about electronics, but I suspect you know
less than you think you do.
>
> CDI=Condenser Discharge Ignition system

And this statement is why I think that.


--
BMW K1100LT Ducati 750SS Honda CB400F, SL125 & SH50
chateau dot murray at idnet dot com
"What you're proposing to do will involve a lot of time
and hassle for no tangible benefit."

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