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1969 911 Distributorless Ignition


Vehicle Information: Model: 911T ; Year: 1969; Body Type: Targa; Engine (type, size, modifications): 2.0, oil pressure fed tensioners, otherwise unmodified; Total Mileage: 102,000;

I've had on and off problems with ignition systems on this car (starting with having a Marelli distributor, but I replaced that withthe proper Bosch replacement for Marelli). Last change I decided was to implement an Electromotive Inc. distributorless ignition system. I find it's really precise, however, it's advance curve isn't adaptable to the original 911T advance. The Electromotive system allows one to set advance at 1000rpm, additional advance from 1000 to 3000 rpm (from 0 to 25 on top of the 1000rpm advance level) and additional advance or retard from 3000rpm to 8000rpm (from 4 retard to 10advance). So, advance curve changes at 3000rpm, and the slope of the curve is 12.5/1000rpm max up to 3000, and 2/1000rpm max from 3000 to 8000. The 911T advance curve changes slope at about 2000rpm, and is initially at about 8.5/1000 until 2000rpm, and about4.5/1000 rpm from 3000 to 6500 where it rev limits.So the closest settings I can figure for the distributorless (and compared to the Marelli/Bosch)system are as follows:RPM Distributorless Marelli/Bosch1000 4BTDC 1BTDC1500 10.25BTDC 8.5BTDC 2000 16.5BTDC 17BTDC2500 22.75BTDC 19BTDC3000 29BTDC 21.5BTDC3500 30BTDC 24BTDC4000 31BTDC 26BTDC4500 32BTDC 28BTDC5000 33BTDC 30BTDC5500 34BTDC 32BTDC6000 35BTDC 34BTDC6500 36BTDC 36BTDCSo the key differences in advance are between 2500 and 5500rpm. Driving the car, it seems like it accelerated better in the 4000 to 6500 rpm range with my distributor (when working properly). Does that make sense based on no other changes other than ignition timing?? Or Should I look to the ignition system for other issues?? I'm just not sure this change is enough to slow down the upper end acceleration of the car?? Worst case is that I put a newer coil and CD-box system in and put the distributor back, but I'm looking for another opinion. I'm just not sure if having the advance go in earlier like this, and then not advancing at as fast a rate would cause poorer upper end performance.

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