Coil for 280zx Dizzy

[toopy]

I have a new Lucas DLB102 coil, which according to where you get your info is a direct replacement for a 280zx coil.
However, ive also read on other uk classic car forums when google searching for coil info, that the DLB102 needs a ballast resistor!

Now im confused

Can anyone enlighten me please

 

[AliK]

Mr T,

I am no expert on this but from what I understand, the ballast resistor reduces voltage to (and therefore FROM) the coil so that the points don't burn out. So check on the other forums that your reading which suggest you need a resistor that they are not running points.

Also coils requiring a resistor have a lower impedance hence the reduction in voltage is also required so that they don't over heat, mainly at idle revs.

IIRC the non ballast resistor coil has an impedance of 3ohms - do you know what yours is rated at?

 

[toopy]

Mr T,

I am no expert on this but from what I understand, the ballast resistor reduces voltage to (and therefore FROM) the coil so that the points don't burn out. So check on the other forums that your reading which suggest you need a resistor that they are not running points.

I looked at several different forums that came up doing a search for Lucas DLB102, some seem to think it was fine
for electronic ignition, others also said, ok but still needs the ballast!

IIRC the non ballast resistor coil has an impedance of 3ohms - do you know what yours is rated at?

I think its 1.5ohm


I think there is a DLB101 that is 3ohms, but that didnt seem to get mentioned any where.

 

[Rob Gaskin]

Guys, I started a Thread on something similar:

http://zclub.net/forum/archive/index.php/t-21024.html

Try the 'Search' facility and perhaps the 'Google' version of it.

As has been said before, most topics have been discussed before so it can give you a good start/background.

 

[Mr.F]

The 280ZX distributor "black box" is internally ballasted and needs a 3 ohm coil and no external ballast resistor. I have suitable Pertronix coils available or could order the OEM 280ZX coil..

 

[SKiddell]

For clarification (Electrical pedant mode on)
On a standard or unmodified setup the coil is designed to spend most of its life running at between 6-9 volts, the ballast resistor is switched out of circuit when starting to give the standard coil "over voltage" to compensate for current draw of the starter etc and a cold engine, this "over voltage" increases the spark density and assists starting, once the car is started the ballast resistor is switched in to reduce the coil supply from 12 volts back to 6-9volts, easing the life of the coil, rotor arm, cap etc.
Points life is eased by the condenser (which is a capacitor) buffering the current spikes when the coils magnetic field collapses (creating back emf).

If you are using a true 12 volts coil then you should have the ballast removed as it is designed to run at this voltage permanently
But ensure that any coil is designed for purpose as there are 12 volt coils for electronic systems and 12 volt coils for points systems
(Electrical pedant mode off)

 

[morbias]

The 280ZX distributor "black box" is internally ballasted and needs a 3 ohm coil and no external ballast resistor. I have suitable Pertronix coils available or could order the OEM 280ZX coil..

I thought the 280zx ignition controller unit needs a 1 ohm coil

[EDIT] just had a look at the 1980 S130 FSM (picked a year at random!) and according to that the resistance across the coil should read 0.84-1.02 ohms (page EL-26). Or were there different setups and coils used on different years for some reason.

@SKiddell - Isn't the output voltage the important factor, not the input voltage? Obviously the output voltage is limited by the input voltage but does that not depend on the coil, ie. the ratio of primary to secondary windings? And also what sort of ignition you are using in the dizzy, wouldn't that have an influence on what is sent to the plugs? On a stock points setup the condensor would absorb some of it but on an EI setup without a condensor the whole lot gets pushed to the spark plugs or is that not how it works?

 

[Mr.F]

Points use 1.5ohm coil + ballast resistor = 3 ohm and reduced voltage at coil +ve when resistor warms up.
Electronic use 3ohm coil and no ballast resistor for 12v maintained at coil +ve.
The 280ZX box contains several circuits which monitor spark timing, amplification, control power switching, duty control (ratio of on/off coil primary period) and current limiting.

If you use a ballast resistor with a 280ZX electronic system, then 9v will not drive the "black box" adequately and you are likely to experience reduced performance and/or misfiring. Upgrades to 280ZX distributor tend to use the simple two wire hook-up which uses the coil +ve to supply the box with 12V ("B" terminal). On the 280ZX the coil +ve and the "B" terminal are both supplied with continuous 12V from an ignition controlled battery source.

Some aftermarket electronic systems can be used with a 1.5ohm coil and ballast resistor - see individual instructions that come with the system.

 

[morbias]

Points use 1.5ohm coil + ballast resistor = 3 ohm and reduced voltage at coil +ve when resistor warms up.
Electronic use 3ohm coil and no ballast resistor for 12v maintained at coil +ve.

Yes I understand this is the common view but I am simply wondering why. For instance, if you look at the spec sheets for the Flamethrower coils (for example), the 3 ohm coils have a ratio of 80:1 whereas the 1.5 ohm coils have a ratio of 100:1. So doesn't that mean that whether you use a 3 ohm unballasted setup or a 1.5 ohm coil with a ballast resistor, the energy sent to the spark plugs is going to be more or less the same?

Also the thing about the resistor warming up; is it not just a case of the ballast resistor not being in the ignition start circuit? When the key is returned to the on position the circuit switches to the branch with the ballast resistor.

Also re. the 280zx coil - I figured there would be gubbins in the controller that was dependant on the correct coil being used, but why does the FSM say it should be 1 ohm if it should actually be 3?

 

[SKiddell]

@SKiddell - Isn't the output voltage the important factor, not the input voltage? Obviously the output voltage is limited by the input voltage but does that not depend on the coil, ie. the ratio of primary to secondary windings?that not how it works?

Not sure what your point is Morbias, the output voltage is a direct ratio of the input voltage, thats how transformers work, as it stands its much easier for the manufacturer to modify the input voltage to the coil by the use of a resistor rather than the output voltage by modifying the windings or would you propose that the manufacture has two coils, one with one set of windings and one with another ??, remember an ignition system of this design was used by almost every motor manufacturer for 60 - 70 years

And also what sort of ignition you are using in the dizzy, wouldn't that have an influence on what is sent to the plugs? On a stock points setup the condensor would absorb some of it but on an EI setup without a condensor the whole lot gets pushed to the spark plugs

You are misunderstanding the purpose of the condensor (capacitor) you dont have one on an electronic system as you don't need to quench the back emf generated by the coil as you have no points to protect.

Please understand that what I posted is not my opinion, its engineering fact and the way it was designed back in the late early 1900's it is also used as a classic study in electrical engineering modeling

http://www.fas.harvard.edu/~scphys/courses/E1b/E1b_3b.pdf

http://www.jetav8r.com/Vision/Ignition/CDI.html

 

[morbias]

Not sure what your point is Morbias, the output voltage is a direct ratio of the input voltage, thats how transformers work, as it stands its much easier for the manufacturer to modify the input voltage to the coil by the use of a resistor rather than the output voltage by modifying the windings or would you propose that the manufacture has two coils, one with one set of windings and one with another ??, remember an ignition system of this design was used by almost every motor manufacturer for 60 - 70 years

An ignition 'coil' is 2 coils, one inside the other, no?

As per my above post, manufacturers do have coils with different windings. The ratio between the windings determines the voltage output of the coil, so an 80:1 will give less step-up than a 100:1.

But I think I've figured it out for myself just by typing this out; the voltage output of a 3ohm 80:1 coil is going to be similar to the voltage output of a 1.5 ohm 100:1 coil + ballast resistor, but the current will be less with the 1.5 ohm coil.

Basically when people talk about a 3 ohm coil giving a stronger spark than a 1.5 ohm with ballast, in the above scenario (80:1 vs 100:1) what they actually mean is the spark duration is longer because of the higher current, right? And with points you get less dwell but with EI that's not a problem, so is it fair to say that with EI the above mentioned 1.5 ohm coil with ballast is going to be more than enough for any average engine running in a normal rev range and the whole issue of 3 ohm vs 1.5 ohm is in fact a bit of a non-issue unless you have an engine that hits higher revs than normal (even then it might make no difference).

That was basically the point I was trying to make...

You are misunderstanding the purpose of the condensor (capacitor) you dont have one on an electronic system as you don't need to quench the back emf generated by the coil as you have no points to protect.

Please understand that what I posted is not my opinion, its engineering fact and the way it was designed back in the late early 1900's it is also used as a classic study in electrical engineering modeling

http://www.fas.harvard.edu/~scphys/courses/E1b/E1b_3b.pdf

http://www.jetav8r.com/Vision/Ignition/CDI.html

Thanks, I will give those a read

 

[SKiddell]

Morbias let me get this straigh, just exactly what are you questioning, my explanation or a tried and trusted technology or the technology itself.


I suggest you read the articles (there are 1000's more out there) and maybe give the authors a ring , some professor at Harvard university would love that, they don't get out much.

 

[toopy]

Well, im not an electronics/maths wizz, so some of the above goes over my head, but in essence
the coil i have will work, its just not optimal and may fail prematurely.

Mr F can you send me the necessary Petronix or 280zx coil, whichever is cheaper! Thanks

Anyone want to buy a 1.5ohm coil? requires ballast resistor... apparently

£20 + 3.50 postage, which is what i paid

 

[morbias]

Morbias let me get this straigh, just exactly what are you questioning, my explanation or a tried and trusted technology or the technology itself.


I suggest you read the articles (there are 1000's more out there) and maybe give the authors a ring , some professor at Harvard university would love that, they don't get out much.

You seem to think this is some sort of personal attack... well it's not so chill out!

Maybe I didn't explain it properly so I'll try to put it as simply as I can.

Mike mentioned the Flamethrower coils; there is a 3 ohm one and a 1.5 ohm one that you use with a ballast resistor.

The 3 ohm coil has an 80:1 ratio, the 1.5 ohm coil has a 100:1 ratio, therefore the output voltage of both setups is going to be more or less the same, so basically the whole argument of the 3 ohm setup putting out more volts than the 1.5 ohm setup doesn't really hold up. It looks like the manufacturer has put more secondary windings and thus a higher step-up in the 1.5 ohm coil in order to compensate for the ballast resistor.

This means that even though both setups have a similar output voltage, it's only the output current that's lower on the 1.5 ohm setup. The current affects the spark duration, not the kick of it; therefore on an EI ignition system where dwell is not a problem there shouldn't be any worry about spark duration anyway due to the coil not charging fully so unless you run a ridiculously large spark plug gap or extremely high revs where dwell might again be a problem, there doesn't really appear to be much benefit of the 3 ohm Flamethrower setup over the 1.5 ohm + ballast one.

That is all I was questioning.

 

[SKiddell]

You seem to think this is some sort of personal attack... well it's not so chill out!

Then don't write it like one.....simples

And for the record, I am really really extra chilled and as such cannot chill anymore but thanks for the advice.

 

[morbias]

I wasn't aware that I did but sorry if it came across that way.

All I'm saying is that the 3 ohm vs 1.5 ohm argument is only valid if it's assumed both coils have the same number of windings, and where the Flamethrower is a commonly fitted upgrade I think it's worth mentioning that the 3 ohm coil they sell has less than the 1.5.