Thread: Twin Spark Swap Owner's Satisfaction Survey
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Old 08-12-2007, 02:22 PM
180OUT 180OUT is offline
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Join Date: Mar 2007
Location: San Antonio, Texas
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Quote:
Quote:
Originally Posted by sfourza View Post
The info re dizzy vs mapped ignition has been very helpful, as I'm currently trying to determine the best ignition timing for my GT Jr/TS (75 head with Webers). Will mapped ignition work with carbs? I get pre-ignition "ping" if I advance the distributor timing from "stock" at idle.
Sfourza
I encountered the same thing several years ago when I built my 2L with 10:4 Borgos. The Marelliplex was a great ignition, but my motor had preignition under just about any load. I was reading one of David Vizard's tuning books where he mentioned that motors tend to have a 2400rpm preignition period, caused by an out of control flame front. That, of course, is exactly what MSD6A ignitions were/are designed to combat. So, I installed a 6A (plugged right into the Marelliplex/FM amplifier) and immediately found that the pinging was dramatically reduced. Only on very hot, very humid days could I inuduce slight pinging---and then only if I intentonally lugged the car down in 4th or 5th gear.

Modern crank fired, programmable ignitions are an improvement over the Marelliplex/MSD approach. There are a number of options for doing this with your Alfa. The easiest by far is simply to order Max's (Alfaholics) mapped ignition kit. He's done all the grunt work for you.

While there are a number of companies (MSD, Electromotive, etc.) who'll sell you programmable igniton parts, there is a particularly elegant solution that's lots cheaper. Do a search on the forum for "EDIS". Bcal (Brett) in OZ has a 2L running Megaequirt fi which drives a Ford EDIS crank fired programmable ignition. You can visit a PickNPull junk yard and scrounge a complete EDIS ignition from a 90's Escort for about $20-30 bucks. If you want to run carbs. there's a stand alone controller call "Megajolt" that will drive the EDIS and give you complete programmability. If you do a little digging, you'll find part numbers for EDIS systems which have multifiring capability built in.

In my opinion, whether or not you choose to retain the dizzy is less important than being able to map the ignition for your particular car. That's light years ahead of a MarelliPlex/MSD setup.
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Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series
Last edited by 180OUT; 08-12-2007 at 04:25 PM.
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