[Diy_efi] Key-On Power for 7730

Sun Oct 1 15:14:21 UTC 2006

Regarding current consumption of ignition coils, so do coils intended 
for old breaker-point ignition systems operate at about amps. The 
breaker points would wear too fast at higher currents.
Some coils limit the current by themselves, as the primary winding has 
enough resistance (around 3 ohms for a 12 V system). Other coils have 
less resistance in the primary winding (often 1-1.5 ohms) and such coils 
always have an external ballast resistor when they are used in a breaker 
point system. In some cars, the resistor might be implemented as a 
resistance wire in the cable harness. There are two reasons for having 
an external ballast resistor: First, it will give less power dissipation 
and less heat in the ignition coil, giving it a longer life (and 
possibly smaller dimensions). And second, there is the possibility to 
short out the ballast resistor to facilitate cold starting.

On the other hand, electronic ignition systems (from about 1980 on) 
usually has a current limiting power stage in the ignition module. 
There, the current is usually 5 - 8 A and determined solely by the 
ignition module. Such ignition coils usually have a very low primary 
resistance (0.2 - 1,0 ohms) and should NEVER be used for breaker point 
systems.

Some early electronic ignition systems from the 70's use similar 
ignition coils and ballast resistors as the breaker point systems have.

A drawback of connecting a backward diode across a relay or solenoid 
coil is that it in some cases will delay turn-off of the relay. Also, 
the diode would blow up if the control voltage arrives with wrong polarity.
A better way is connecting an R-C link across the coil. The resistor 
should be approximately the same value as the DC resistance of the relay 
coil and the capacitor usually between 0.1 microfarad and a few 
microfarads. The bigger relay, the bigger capacitor.

Best regards

Torbj?rn Forsman

Don Sauman wrote:
> Not absolutely certain of your wiring arrangement, but it is usual to 
> put a reverse biased diode across relay coils to suppress back-EMF.
> 
> Don
> 
> Clair Davis wrote:
> 
>> Hehehe... I've had more cars with starter buttons than I care to think
>> about.  It's one of those little items that would be used by my wife or
>> mother (Dad's a victim, too) as evidence that we'd hacked on a car...
>> Agreed though on the cool factor of one of the big S-2000 buttons.  If I
>> were to get one of those, I'd check the Honda dealer first, and I'm sure
>> there are some aftermarket solutions, too.
>>
>> Got my wiring done today.  I came this >< close to using a relay to power
>> the coil with power to the small side of the relay coming from the two 
>> key
>> switches.  Checking again, the relay would not have powered off 
>> through the
>> key operation, but using a 9V battery to run things test, I "noticed" 
>> a BIG
>> voltage spike when I broke the circuit.  I had to be holding the relay a
>> certain way to do it, but I suspect it was just like an ignition coil.  I
>> can't swear that it would have had any affect on the ECM, but I didn't 
>> want
>> to risk it.  It really felt like a good "tingle" you get when brushing up
>> too close to a bare 120V house wire.  Hot enough to feel through my 
>> finger,
>> and this from a little 9V battery.
>>
>> Not quite off-topic, how much current does a typical "oil can" coil 
>> draw on
>> the (+) terminal?  This is a Jacobs Energy Coil steel cylinder oil-filled
>> unit if that makes a difference.  OEM has 18ga wires running power to the
>> coil, so I'm guessing those will continue to be fine.
>>
>> Clair
>>
>>
>> ----- Original Message ----- From: "Joe Boucher" <boucherj at prodigy.net>
>> To: <diy_efi at diy-efi.org>
>> Sent: Saturday, September 30, 2006 5:28 PM
>> Subject: RE: [Diy_efi] Key-On Power for 7730
>>
>>
>>  
>>
>>> How about this idea.  Install a start button that is energized when the
>>>   
>>
>> key
>>  
>>
>>> is in the on position.  Turn key to on, press starter button.
>>>
>>> That's kinda cool.  I like starter buttons.
>>>
>>> The Honda S2000 has one and a couple of other high end, late model cars.
>>> Probably not something you would casually find in a  a low end junkyard.
>>>
>>> But it sounds like you don't have problem other than finding the key.
>>>
>>> -----Original Message-----
>>> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
>>> Behalf Of Clair Davis
>>> Sent: Thursday, September 28, 2006 9:48 PM
>>> To: Rick McLeod; diy_efi at diy-efi.org
>>> Subject: Re: [Diy_efi] Key-On Power for 7730
>>>
>>>
>>> This, folks, appears to be true here, too.  I basically made a little 
>>> test
>>> light circuit to see if there was an obvious break in the circuit 
>>> between
>>> IGN-1 and IGN-2.  Using an 1187 dash light, I wired I1 and I2 (and ACC
>>>   
>>
>> just
>>  
>>
>>> for fun) together with a 9V battery.  I could not see any dimming of the
>>> bulb between run and start, regardless of how fast or slow I turned the
>>>   
>>
>> key.
>>  
>>
>>> Turning the key was the big problem, as I had to disassemble the dang 
>>> lock
>>> tumbler to make the motion consistent.  Kind of hated to do that, as 
>>> 1969
>>> ignition cylinders are unique (last year for dash-mounting for Mopar) 
>>> but
>>> I've got NO idea where the key for that sucker is.  Not much of a
>>> theft-deterrent at this point.
>>>
>>> Thanks, Rick, Tom, Tim, Will, and Lee for all the guidance.  Maybe I'll
>>> finally get these last two wires done this weekend!
>>>
>>> Clair
>>>
>>>
>>> ----- Original Message -----
>>> From: "Rick McLeod" <dunvegan at sbcglobal.net>
>>> To: <diy_efi at diy-efi.org>
>>> Sent: Thursday, September 28, 2006 12:39 PM
>>> Subject: Re: [Diy_efi] Key-On Power for 7730
>>>
>>>
>>>   
>>>
>>>> Good advise, but every ignition I've ever seen though has been MBB, not
>>>>     
>>>
>>> BBM. (Make Before Break vs. Break Before Make)
>>>   
>>>
>>>>     
>>>
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>>>   
>>
>>
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>>  
>>
> 