Lotus Elan

123 ignition tune

PostPost by: Pistacchio sprint 72 » Sat Jul 12, 2014 8:42 am

I am very happy with the 123 ignition tune i had installed on my seven crossflow engine 2 years ago.
You can switch between two ignition curve by the flip of a switch.
You enter the ignition curves into the dizzy using a laptop and a usb cable.
It looks like an excel sheet where you set the points either by hand directly on the graph or by entering values in the table on the side of the graph. Really easy.

The only thing is that it is easier when you have an igntion curve to copy.

Do you have guys, the ignition curve of a lotus elan sprint dizzy?
Thxs
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PostPost by: billwill » Sat Jul 12, 2014 12:25 pm

From my OGU topic:
lotus-elan-f19/getting-ogu-roadworthy-again-t26101-120.html#p191893

billwill wrote:This is the data from the Lucas Distributor database referenced in another topic.




Service Number 41189a
Model 23D4
rotn CCW
ECM curve
RPM 1 3250
Advance 1 7
RPM2 1000
Advance2 5
RPM3 600
Advance3 1
RPM4
Advance4
No advance below 400
Vacuum code no vacuum
Connection screw
Years 1968-73
Models Lotus
comments Elan_2S, 130S, S4, Sprint, Ford Escort and RS1600


Which I read as no dynamic advance below 400 rpm
1 degree at 600 rpm
5 degrees at 1000 rpm
7 degrees at 3250 rpm

Notice that maximum advance is not specified.

Unfortunately the database table does not clarify whether this is crankshaft RPM or distributor rpm, so they could be wrong by a factor of 2. That would make it 7 degrees at 6500 rpm crankshaft

All suitably confusing to the innocents. :D :D And not matching exactly to Lotus timing instructions of about 19degrees at 1000 RPM (12+5 =17 not 19).




Also see:
lotus-electrical-f38/tuning-lucas-distributor-t28918.html
Bill Williams

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PostPost by: rgh0 » Sat Jul 12, 2014 12:32 pm

Hi Bill
Your numbers are distributor degrees and distributor rpm so double both for engine crank degrees and engine rpm.

cheers
Rohan
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PostPost by: Galwaylotus » Sat Jul 12, 2014 5:05 pm

I agree with Rohan's assessment. When programming the advance curve, however, it probably is looking for distributor advance ? rather than crankshaft ?.

I also note the statement, "Notice that maximum advance is not specified." I'm not convinced that this is true. Mile Wilkins book on the Twin Cam shows a maximum (crankshaft) advance for the 41189A distributor at either 24? or 26? BTDC depending on the engine spec. The former has a 10? static advance while the latter has a 12? advance. In both cases the distributor mechanical advance is 7? (or 14? at the crankshaft). Miles also quotes Graham Atkin and John Bloomfield, "No Weber twin-cam engine specification needs more than 24-25 degrees of advance, whereas the Stromberg does." That would lead me to believe that the full mechanical advance comes in at 3250 rpm. That is based on the listing billwill gave; however, Miles specs for that distributor show full advance at 5000 rpm crankshaft. As in many things Lotus it only gets more confusing the deeper you dig!! :?
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