TheSamba.com :: View topic

Wed Mar 05, 2014 6:45 pm

DISCLAIMER: I'm fairly new to all of this.

So I've been trying to get a grasp on how the aftermarket electronic ignition systems work. I understand how the factory dizzy, points, and coil all work but what components do these aftermarkets replace and/or interact with? Where are the benefits most noticeable and at what point are they worth investing in?

My current (first) build is a 2276. I've committed to what basically equates to a W125 cam (DRD cam with a tiny bit shorter duration at .050). Heads and carbs are still in the debate column but I'm thinking like a CB mini wedge 42x37.5. Probably Dell 40 carbs if I can find them or maybe 44IDFs.

Does an electronic ignition have a rightful home in my engine?

PS - I searched for some basic info on the forums but couldn't fine much that was definitive. If there's a post I missed, please simply post a link and I'll promptly shut up.

THANKS!

Wed Mar 05, 2014 6:53 pm

homebrew_86 wrote: Does an electronic ignition have a rightful home in my engine?
Do you mean a Pertronix, Hot spark or Compufire?

If so they are just electronic points replacements.

If you're talking about CDI, MSD or crankfire.... its a different story.

I run a mechanical distributor with points and just a Bosch coil on a 2180 w/ IDAs. It runs great.

Wed Mar 05, 2014 6:57 pm

The points replacement modules have been discussed before.

Beyond that you'll have to be a bit more specific. CDI? Boosters? Whole different systems? there are thousands of them :shock:

Wed Mar 05, 2014 7:00 pm

I see. So if you decide to with CDI or the others, its a completely electronic ignition? Would you be using the distributor drive pinion for timing somehow?

And what gains would those give you?

Wed Mar 05, 2014 7:02 pm

modok wrote: The points replacement modules have been discussed before.

Beyond that you'll have to be a bit more specific. CDI? Boosters? Whole different systems? there are thousands of them :shock:

I don't really know what any of that is modok :oops: (aside from the point replacement modules). Told you I was new to this. lol

Wed Mar 05, 2014 7:09 pm

Get this book:

http://www.amazon.com/Doctors-Step-Guide-Optimizin...YPDYCVF757

After reading it, you will have forgotten more than most people know

Wed Mar 05, 2014 7:11 pm

Nice! Thanks Eaallred. One day I hope to be on the other end of this discussion. Lots to learn still!

Wed Mar 05, 2014 7:13 pm

You can do any combination of things, depending on what you want to do.

IMO "Electronic ignition" is when you drive the coil with a transistor.
So the points replacement modules are transistor, but so are others too.

CDI is when you drive the coil with a capacitor system, a "CDi box"

Both can be triggered by points or or some other type of sensor such as VR or Hall or optical sensor. Aftermarket distributors will have these different kinds of sensors.

Most OEM engines went to transistor ignition in the mid 70's. By the mid 80's most got rid of points and instead used other types of sensors.
In the 90's they moved the sensor from the distributor to the crank for greater accuracy.

CDI has rarely been used as OEM on cars/trucks, but there are quite a few DIE HARD believers that like them.

So there's really three aspects.........accuracy, power, and control(ability to make it advance how you want).

IMO for a simple carb'd engine like what Glenn or you or I have a old distributor has good enough accuracy and control.........but it's nice to have a little more powerful spark. Opinions differ.

I'm running a modified 009 distributor with regular oil points, but with a ford TFI "module" wired in controlling an old toyota coil. That's what you'd call a "booster". About three times more powerful spark than stock.

You can also do the same with a CDi box, but I find i prefer like how the transistor systems runs.

Wed Mar 05, 2014 7:17 pm

Gotcha. That clears things up nicely. Thanks guys!

Wed Mar 05, 2014 8:23 pm

Try this simple easy (free) read to help grasp basics....

http://en.wikipedia.org/wiki/Ignition_system

Google Search can be your friend....

Dale

Wed Mar 05, 2014 8:26 pm

wow, that book appreciated in price a ton! A decade ago we used to give that one away (literally)!

Wed Mar 05, 2014 8:32 pm

lol i think ive had it twice by accident ..lol the jacobs book hundered bux who knew? fabricator john , coopy

Wed Mar 05, 2014 8:53 pm

[email protected] wrote: wow, that book appreciated in price a ton! A decade ago we used to give that one away (literally)!

You gave it to me to read!

Always do what John says. I have learned that over the years.

Wed Mar 05, 2014 10:39 pm

First there is a trigger, either points (homemade systems), magnetic (hall effect) or optical. Magnetic consists of metal triggers placed on a shaft that pass by a special sensor (hall effect sensor). Optical triggers consist of a light and a light sensor that are blocked by "wings" mounted on the shaft. As the shaft turns the "wings" block and unblock the light from the sensor to trigger it. Pertronix systems are an example of magnetic triggering systems. Mallory systems are an example of optical triggering systems.

In simple electronic ignition systems, the trigger directly triggers the coil drive circuit which has the transistor that does the function of the points in charging and fireing the coil. In most distributors the trigger and drive circuit form one module. The timing is controlled conventionally by the centrifigal and/or vacuum advance systems.

Another electronic ignition system is the capacitor discharge ignition (CDI) system. These require a separate box.

It is also possible to lock out or do away with the mechanical/vacuum advance system and place a timing controlling computer, called a engine control unit (ECU), between the trigger and the coil drive circuit. Instead of a vacuum advance diaphragm, these usually use a manifold air pressure (MAP) sensor, although some use a throttle position sensor (TPS) and/or a mass air flow (MAF) sensor. This can be completely housed in the distributor as with the CB Magna Spark Programable distributor. Or the computer and coil drive circuit can be in a separate box.

Other electronic ignition systems include coil over plug (COP) and waisted spark systems. These usually use crakshaft position sensors and/or camshaft position sensors instead of distributor shaft triggers (points, magnetic or optical, remember?) since these are "distributorless" systems. COP systems have one coil per plug, each fired by the ECU. Waisted spark systems are basically the same except the is one coil for every two cylinders. It fires both plugs at once, one begining tye combustion stroke and the other finishing the exhaust stroke. Since one plug is fired dyring the exhaust stroke it is "waisted".

Thu Mar 06, 2014 12:38 am

Wow! I think I have a Jacobs book somewhere, have to dig it out and put it on feebay! Personally I think it's a bit basic, and outdated now, but if someone will pay that much for it it's time to sell.

CDI is still about, usually multi-spark versions - the control for this is a lot more complicated than the "points replacement" Pertronix and such, which simply replace the points with a wheel with four little magnets driving a hall-effect or reluctor sensor, which in turn drives a transistor or thyristor. This gives some dwell extension and avoids points wearing out. Glenn describes the earlier method of using points to trigger a thyristor or transistor which still provides effective dwell extension, but the rubbing block on the points still wears down. Then there are boxes such as the MSD which take this a little further, though how much they add other than the multi-spark is open to question. Then there is crank-fire, usually as part of EFI, which allows a microcomputer to take over dwell, timing, advance, sometimes vacuum advance, rev limiting and can replace the distributor altogether using two or four coils (in the case of sequential, which also requires a cam sensor.)

Take a pick which one you are interested and I can give you a more complete description... or I can sell you my Jacobs book. :D

P.S. to the best of my recollection the Jacobs does not mention crank fire.

Thu Mar 06, 2014 1:43 am

To the OP. Personally, as you are new to all of this, I think it would be best if you went down the tried and tested route of a Bosch distributor, SVDAs are the best all round performer IMHO. Fit it with a regular electronic ignition module (Pertronix, Accuspark, Powerspark or similar) and see how you get on. This will work well with your engine and should be wholly reliable. There will be no tedious points adjustment and you will get good smooth operation.

Thu Mar 06, 2014 5:04 am

clarkson1968 wrote: SVDAs are the best all round performer IMHO.
So are you saying they are "one size fits all"?

There's no such thing. Ever carb has a different vacuum signal and the "SVDA" or 034 was designed for the 34PICT-3 (a smog carb for a 1600).

Thu Mar 06, 2014 6:24 am

Having engine manifold vacuum provide input for the timing curve has been solidly established by countless engineers and every existing auto manufacturer.

As long as it doesn't add to much ignition, it is only helping.

Saying it was only designed for one engine and then insinuating that it isn't right for much else, well, the same could be said about the 010. IMHO, a centrifugal only distributor is only good for full throttle performance, or severely underpowered vehicles that are forced to put the pedal down all the time. IIRC the only time VW ever put a centrifugal only distributed on at the factory was the early (25hp?) Type 2's. Everything else used a vacuum advance or mechanical/vacuum advance. It wasn't for smog reasons. It was for superior drivability.

Thu Mar 06, 2014 7:24 am

So them why did VW change the vacuum mechanical distributors every year when the carbs changed? Also why didn't Type 1s use the same distributor as a Type 3 and Type 4? After all manifold vacuum is the same and it doesn't matter what carb or even fuel injection is is front of it.

Also I never stated that a 010 is a one size fits all. There are different mechanical models with different curves. And with some carbs you have to use a vacuum/mechanical.

Thu Mar 06, 2014 7:26 am

Glenn wrote:
After all manifold vacuum is the same and it doesn't matter what carb or even fuel injection is is front of it???

Find where I said that, Glenn.

If you have to mis-quote someone to make a point, it usually means you aren't making one.