Quote:
Originally Posted by CATPart
I guess I need to decide if it makes sense to create this electronic "mag replacement" ignition, that does not have a timing advance map.
pros:
-less moving parts
-cheaper parts and plugs (not necessarily lower quality)
-I can say I have EI
-the ford parts have some proven history
cons
-why bother replacing a mag with a mag?
-the switch flip for the starting advance is more workload, but I envision a momentary-on switch, bet then again low rpm ground ops might benefit from the 6° advance.
questions:
-would I expect lower fuel burn?
-would I expect better starts and smoother running?
-how much would low rpm ground ops benefit from 6° btdc?
-my described system does not have it, but if added, what real world advantage would a timing advance map give me and is it enough to care about?
this all comes up as I am nearing that point of slick inspection and have been thinking about a switch to EI instead of servicing slicks. pmag seemed cool, but this edis stuff lets me tinker.
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You left off a significant con. The mags greatest assest is that it runs without electrical input. Not so big a deal if you only replace one. replacing both shifts the balance scale in my opinion.
questions:
-would I expect lower fuel burn?
I don't think so. The benefits here stem from proper timing. As long as a spark can light a fire, having a stronger one does little for you. At altitude, where the mag's weak spark can't light the fire consistently, you'll see improvement. Same holds for aggressive LOP operation.
-would I expect better starts and smoother running?
Same as above. Mag's have a weak spark at very low RPMs and the coil will improve consistency. 4 additional degrees retarded won't add a lot to starting performance in my opinion, beyond a slightly reduced risk of kickback.
-how much would low rpm ground ops benefit from 6° btdc?
Running your engine at any RPM at 6 BTDC would degrade performance and is not recommended. IDLE operation is optimized somewhere in the teen's to upper teen's depending upon conditions. ignition should advance in a somewhat linear fashion with RPM until you reach the max or peak advance in the 3000 range. Lower idles advance reduces heat and was used in the 70's to reduce emission ratings.
-my described system does not have it, but if added, what real world advantage would a timing advance map give me and is it enough to care about?
considerable and yes. The vast majority of benefits you hear about EI are related to variable timing. There is a reason cars don't use static timing. It is worse than archaic. Heck, even the Model T had variable timing albeit manual (a stalk on the steering column). However, it is not unheard of. Many drag engines use a static timing arrangement to eliminate failure and improve consistency. However, those engines only run at Idle and WOT.
Larry
megajolt
Linear Mode
