trerynn Posted March 9, 2015 Report Share Posted March 9, 2015 I am fitting a 123 distributor, any advice on which curve to select . Quote Link to post Share on other sites
stuart Posted March 9, 2015 Report Share Posted March 9, 2015 I am fitting a 123 distributor, any advice on which curve to select . Martin you dont listen do you. B Stuart. Quote Link to post Share on other sites
Guest ntc Posted March 9, 2015 Report Share Posted March 9, 2015 (edited) Yep B on a CP car.Not sure for a 4 but Stuart will know. Edited March 9, 2015 by ntc Quote Link to post Share on other sites
jojim65 Posted March 9, 2015 Report Share Posted March 9, 2015 Yep B on a CP car.Not sure for a 4 but Stuart will know. Hi Neil, I now have a working 123. And as you suggested have set it to 'B'. Could you expand on why this is the best advance curve given all the options Thanks Jim Quote Link to post Share on other sites
Guest ntc Posted March 9, 2015 Report Share Posted March 9, 2015 Jim It is as near as dam the same as a cp car,I do not have the info to hand with regard to a 4 it will be in the book though. Quote Link to post Share on other sites
Peter Cobbold Posted March 9, 2015 Report Share Posted March 9, 2015 As Neil says the curev will be much the same as the 6. Because the 6 and 4 have similar combustion chamber shapes and size and compressions (and turbulence does most of the timing anyway) so we need similar curves. Like these: http://phys.org/news/2015-03-million-migratory-birds-cyprus.html Note these are disy degrees so at the crank they are double these values. All in the centrifugal swing gives about 28 ckdeg at 3000rpm. Add the static timing of around 10BTDC ( right?) and we have about 40deg advance at 3000rpm. For most old engines it will be around 35-40BTDC The 123 has I think a vac advance facility, to connect ot the throttle edge take-off. That should advance the spark further at cruise , to give at 3000rpm about 45BTDC. This gives more more time for the less compressed, leaner mixture to burn correctly. So the 123 vac advance setting that adds about 10 to 15 ck deg is the setting to try first. Peter Quote Link to post Share on other sites
stuart Posted March 10, 2015 Report Share Posted March 10, 2015 FWIW if you do use the A/R facility if fitted on a 123 then you do need a flame trap or similar in the line as any excess fuel/vapour that managed to make its way into the dizzy will destroy it. Not applicable to standard dizzys. Stuart. Quote Link to post Share on other sites
Fireman049 Posted March 14, 2015 Report Share Posted March 14, 2015 As Stuart says it's very important to fit an expansion (flame trap) chamber. If anyone would like a photo. showing the vacuum advance pipe fitted with an expansion (flame trap) chamber then please PM me your eMail address. Tom. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted March 15, 2015 Report Share Posted March 15, 2015 (edited) Read this thread page: http://club.triumph.org.uk/cgi-bin/forum10/Blah.pl?m-1380262350/ Then try the excellent 'MintyLamb' 123 Ignition Curver to see what is offered as steps 0-9 & A-F http://www.mintylamb.co.uk/123ign.html They all suggest a static of 10 degrees - where they go between that and full advance is quite interesting and worth viewing as a graph to compare with the orig spec. This link gives a nice graph of the effects on rate of advance controlled by different weight springs in a mechanical advance system ( as orig) http://www.setyourtiming.com/timing_settings.html Cheers Peter W Edited March 15, 2015 by BlueTR3A-5EKT Quote Link to post Share on other sites
Peter Cobbold Posted March 15, 2015 Report Share Posted March 15, 2015 (edited) Spark timing summary: http://www.innovatemotorsports.com/resources/myths.php It mentions factors that affect optimum timing: rpm, compression ratio, load, mixture, cylinder filling. Most of which can be different from the original factory engines. Measuring the best spark timing is difficult, if not impossible. The torque changes little for a big change in advance or retard from peak. http://www.daytona-sensors.com/engine_tuning/Timing_Torque.gif 'MBT' is Maximum Brake Torque Feeling a difference while driving is well nigh impossible to get to that last percentage point of power, although it will get onto the plateau on that curve. But the spark could still be 5 ck deg too advanced or too retarded from best. But we dont know what best is....for the full range of operating conditions. Peter Fig2.8 shows the top few percent of the MBT curves for different rpm ( N) and loads ( Pim, KPa). http://liu.diva-portal.org/smash/get/diva2:23960/FULLTEXT01.pdf The peakiest curve was for 1200rpm at 40kPa ( ie 0.4Bar, ie light load) So thats where the TR engine will show the greatest diffferences in 'feel' with different spark advances, hence the region of the 123 settings to change for best part load running. Edited March 15, 2015 by Peter Cobbold Quote Link to post Share on other sites
snowric Posted March 25, 2015 Report Share Posted March 25, 2015 Interesting video from TR member on tune 123 on a 6 cylinder car with a Kent TH6 camshaft. 12 mins in he shows his optimal settings. Interesting that he has a higher advance at tickover to keep it smooth and (peter ?) I assume to maximise the efficiency of the burn at tickover. This then drops off to what looks to be a normal curve, i assume to avoid pinking. Snowy Quote Link to post Share on other sites
Peter Cobbold Posted March 25, 2015 Report Share Posted March 25, 2015 (edited) Curve is at 11:54 . Edited March 25, 2015 by Peter Cobbold Quote Link to post Share on other sites
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