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MG Midget and Sprite Technical - 1275 Ignition Timing
|I have a 1275 with 123 Distributor, performance exhaust manifold, and K&N filters, with the correct needles.
When the timing is set up with a strobe, and vacuum gauge, the performance is great, and it accelerates very well. However in this condition, it is very difficult to start from cold, the starter motor just seems to hit a brick wall, and its apparent that the ignition is too advanced for starting.
With the ignition slightly retarded, the performance is still acceptable, and the starting is fine, but I miss the extra sparkle, and the vacuum gauge says the ignition is slightly retarded.
Do I have to live with a compromise between performance and starting, and would a high torque starter help.
From memory the 123 curve should be set on number 4 for the car, I have pushed it up to 6, still with no pinking.
put it back to 4.
No you don't need a hi-torque starter and yes just about everything with a road car is a compromise.
Check tappets gap, check your plugs, the condition and gaps - replace if required, adjust the timing if required and mixture if required.
How do you know you have the correct needles?
You can set the car up to run well (over a wide or narrow range) but to get the most you can the car needs a full service and full driving then and a good number of runs on a rolling road with a good tuner.
I've got a 123, LCB and performance exhaust, K&N with correct needles from a good tuner (previously wrong needles with a not-so-good tuner) and other small bits'n'bobs.
I go to Peter Burgess as he's a good tuner and will give the car sufficient runs to set it up well without charging as much as others to do the job properly.
I do have a hi-torque starter but I did need to replace my previous standard starter and like the idea and sound of the hi-torque.
|I have the high torque stater and just love it, from britishstarters.com its the izuzue starter versiom
If your running over 9 CR ratio its a huge advantage
That said... i would be very careful about over advancing the timing... it could be the cam, chain, and sporckets are worn and your getting a false reading
Unless your needing this as a street racer to make illeagel racer money id make an appoimtment with Peter Burguss on his rolling road or knock it back a few degrees to enjoy driving it on the road... not every stop light needs to be a christmas tree to peel the rubber off
You could book your car in for a tuning / diagnostic session with A.C.Dodd at M.L.Motorsport.
A.C.Dodd is well known in Mini circles but has had a great impact lately with members of Kent Area midget and Sprite Club. (www.masckent.org)
M.L. Motorsport are at Higham,Kent so not a million miles from Sussex.
A.C.Dodd has once monthly sessions on a Saturday.
|Thanks for the answers guys, the car is well serviced, and the timing chain was changed recently.The needles are the ones recommended by the filter suppliers (MGOC).
I chose to go to curve 6,as my understanding was that the advance curves do not have any effect during starting, or low RPM, so if a slight retard is needed for starting, then an increased curve number would compensate for this retard as the Revs increase.
I don't think my left leg would stand a round trip of about 300 miles in the Midget,to see Peter,but I will look into M.L.Motorsport, thanks Alan.
my engine is up from standard but not big output stuff and as I remember it when I fitted the 123 with a mate of mine who knows about cars I said about moving up the curves and he just smiled at me and it was set on 4 IIRC and has remained there.
So perhaps you should ask about this with your tuner or after set up runs try power runs on 6 and then change to 4 to see which is best overall.
With the needles they may very well be correct or your particular car set up may suit some slightly different needles.
I've found some tuners seem to have their gauges and print outs set up for ego/exaggerated figures and others don't, not that it really matters what the figures are other than as a comparison guide for setting the car at that session.
|I am led to believe that A.C.Dodd actually designed the curves for the 123 Dizzy. Who better to sort the car. He will also customise your SU needle if needs be.|
|Interesting news Alan and very good news for Dave.|
if you go there (seems a very good idea to) and if you want to and can ask I'd be interested to know what real world difference to a road going Spridget the 5, 6, and 7 settings make compared to 4, cheers (do bear in mind I'm totally non-technical and mechanical).
sorry I've just remembered that mine was set on 0 not 4.
I've also just checked the instruction sheet I got with the 123 and the 0 to 3 band would be the correct band for my 1973 car.
Look up AC Dodd on Facebook. His profile page is of him with goggles and facemask. You can contact him and ask him yourself.
I have arranged a couple of 'an audience with A.C.Dodd' that have been both entertaining and informative. Four Kent cars are fitted with his camshafts. He has tuned several and had much imput on engines including machining.He also writes tech articles in one of the Mini magazines.
thank you, unfortunately I'm not on Facebook.
I'd very soon be overwhelmed with anything even slightly technical especially to do with engines and ignition, I'm hoping for the simplest of answers even if that answer is there isn't a simple answer. :)
I know the from the very few times I went on the 123 website things seemed quite cryptic but a few contributors were able to give their experiences and answers to simpler questions. I should add, I wasn't looking for info on curves and settings on the 123 website (I can't remember now why I was there).
|You got your SU needle recommendation from your air filter supplier (MGOC)
WOW...NO!, Sorry completely the wrong answer.... well sort of
I understand that MGOC sells parts so im sure from experiance they have a good idea of what goes with what, so there recommendation is more of a good guess not a fact, i want to say su carbs has around 300 differsnt needle specs, its not a science its more art trial and error
For your needs... your into the weeds your needing very specific specifications if you pushing your timing to this level 6 setting then you want the exact needle for your engine not a general guess
If you read danial stapletons book he has the best section for dialing in SU needles ive ever read, seriously need to read that chapter
Setting on the 123... your only partly correct, yes there wont be any or very little advance at ideal or low revs but how the dissy is curved will have a huge effect on how fast or slow the dissy timming maxs out compared to your fuel quality and the amount of fuel atomisation being burnt
What i mean is you can have a short curve on high octan(slow burning fuel) and a A/F ratio of 9 (lean)
and that could equal a long dissy curve with low octan fuel ( fast burning fuel) with a high A/F ratio (rich) of 14
Meaning meaning you can go both ways...if you have a high CR engine of say above 10.5 then you probably want a really long curve set up... but you have to nail the timming dead on as it relates to every thing else... and that includes your camshaft timming if your camshaft timming is to advanced then you could retard it and set your dissy curve to a longer curve giving you more dissy timming
Thats all therory in my head, but you get the idea of where im going... david vizard has a great chapter thats a little complex and dry to read that explains how all the varibles fit togather but if you can read thst thur several times, you will have a much better understanding of how it all works and you can take out the gambling and guessing your involved in at the moment
I think you need to decide what it is you want to achive with this engine... do you want to do this as a top end tune for race day where you need every drop of horse power or is this just a once a week stop light to stop light peel off the rubber dounut burnout fun street racer
If you need this for real competition and every drop counts, then you need to be very specific in your specs
If its just a fun street racer then its just general settings if your off here and there by a couple of degrees thats not a problem ... but you dont max out your specs to the top end ither... keep them with in reason
Tbh... for what your wanting you may have the wrong dissy, you may want the 123 (tune) instead of the standard 123, the 123 TUNE Uses a lap top computer instead of chips to set the curve and the entire dissy is adjustale from the laptop computer
Sorry for the book... my fear is you not aware of the risk your playing with, if this goes bang, you could be looking at $3000 to $5000 for an engine rebuild or new engine
When your pushing the top end of engine specs you cant be guessing ... you have to know
|Thanks for the answer Prop, no I am not trying to make a track day car, just trying to get a compromise between starting, and performance to keep up with modern traffic. As far as I know the camshaft is standard, and when I got the car as semi wreck, the engine was Gold and rust coloured. so I assume it was a Gold seal engine at some time. (why don't POs keep bills)
I don't think I am in danger of blowing it up, as cruising on the motorway at 3 to 4000 RPM it stays very cool, with the gauge staying just under normal.
Talking of keeping up with normal traffic, I had a funny experience some time back, driving on a winding A road, A264 for those that know it, I had a modern VW on my tail, and he was unnerving me a bit, I went into a corner at normal Midget speed, and he disappeared, I thought that's good, and then he came storming up behind me again. This happened at every bend. I don't know if he could not drive, or his car was rubbish, but it was fun for a while.
3-4,000rpm cruising on the motorway, have you got a 5-speed box then as 70mph is over 4,000 rpm in 4th.
Depending on your gauge accuracy just before N might be just a tad warmer than usual as most (1275) I've heard about are at about 7 on a clock rather than near 6. As always I have a simple but thorough cooling/heating cleaning system I can let you have notes on, it's worked for a couple of others on here (gets your heater warm/hot for winter use too).
I like small roundabouts on open roads as the modern that was previously quite close then has to work a bit harder to catch up again after the roundabout. I'd prefer to be overtaken but some just seem to want to ride on the car in front's bumper instead.
This thread was discussed between 30/06/2017 and 03/07/2017
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