Adrian Steele Posted August 5, 2021 Report Share Posted August 5, 2021 I have fitted the 123 Tune distributor to my six to replace the worn Lucas distributor. It now runs so much better so I clearly hadn't appreciated how worn the old one was. I have played around with the advance curve settings to get what feels like the optimum so thought it would be a good idea to check/adjust it finally on a rolling road. One near me is Turner Mechatronics in Hemel Hempstead who besides tweaking modern cars claim to be capable working with classics including TR6s. Problem here was the expert mechanic was adamant that I should have a vacuum to the distributor otherwise it will never run properly and then proceeded to lecture me about this retrograde modification - "nothing wrong with the Lucas dizzy but it needs vacuum." I got concerned when he said he could adjust the metering unit (MU) if it needed it. Alarms bells ringing now, because if he thinks a six has to have a vacuum to the distributor then he is not that knowledgable so I wanted him no where near the MU. I took the car away with no work being done, but had to pay 1 hour labour for the ten-minute conversation to get my keys back despite him never touching the car!! In short - looking for recommendations of someone trusted in Bucks/Herts/Oxon area with rolling road capability and TR6 KNOWLEDGE. Quote Link to post Share on other sites
Tim D. Posted August 5, 2021 Report Share Posted August 5, 2021 Sounds like a bit of a trial, but in his defence the PI setup sans vacuum is a little unusual and people don't really understand why it doesn't have one. Tim Quote Link to post Share on other sites
BlueTR3A-5EKT Posted August 5, 2021 Report Share Posted August 5, 2021 (edited) 5 hours ago, Tim D. said: Sounds like a bit of a trial, but in his defence the PI setup sans vacuum is a little unusual and people don't really understand why it doesn't have one. Tim The never worked on a Cooper 'S' then either. Have you considered Enginuity in Acton NW London? https://enginuity.co.uk/ They have a Sun Rolling Road Dynomometer with TAT software Peter W Edited August 5, 2021 by BlueTR3A-5EKT Quote Link to post Share on other sites
Steves_TR6 Posted August 5, 2021 Report Share Posted August 5, 2021 Enginuity are good. i have a tune+ on my 6 and would also like to do a rolling road tune up perhaps we could coordinate and both do this the same day Adrian ? steve Quote Link to post Share on other sites
Adrian Steele Posted August 5, 2021 Author Report Share Posted August 5, 2021 Agree, thinking it would be good to get some like minded 123 converts together. This is my current setting based only on how it 'feels/sounds' when running: Static 11 deg BTDC - based on LED illumination. RPM ADVANCE Deg 500 12.0 1000 16.0 1600 21.0 2000 23.0 2600 28.0 3000 30.0 4000 32.0 5000 34.4 My six is running so much better compared with the knackered worn out Lucas dizzy it replaced. Running a Piper TR6BP285B Cam with 6 into 2 Extractor and a very noisy sports exhaust (I may need to silence (sic) that in the future!); so think it would be good to confirm 123 advance curve settings in action - hence rolling road. Gut feeling is I could be more aggressive on advance but want a pro to help me here. Just need to find a pro - Enginuity may be the preferred choice at the moment. Still smarting about paying for nothing, but expecting Mastercard to sort it out for me........... Quote Link to post Share on other sites
ntc Posted August 5, 2021 Report Share Posted August 5, 2021 33 minutes ago, Adrian Steele said: Agree, thinking it would be good to get some like minded 123 converts together. This is my current setting based only on how it 'feels/sounds' when running: Static 11 deg BTDC - based on LED illumination. RPM ADVANCE Deg 500 12.0 1000 16.0 1600 21.0 2000 23.0 2600 28.0 3000 30.0 4000 32.0 5000 34.4 My six is running so much better compared with the knackered worn out Lucas dizzy it replaced. Running a Piper TR6BP285B Cam with 6 into 2 Extractor and a very noisy sports exhaust (I may need to silence (sic) that in the future!); so think it would be good to confirm 123 advance curve settings in action - hence rolling road. Gut feeling is I could be more aggressive on advance but want a pro to help me here. Just need to find a pro - Enginuity may be the preferred choice at the moment. Still smarting about paying for nothing, but expecting Mastercard to sort it out for me........... Std bottom end I would say that is about right and I would not go any further Quote Link to post Share on other sites
JochemsTR Posted August 6, 2021 Report Share Posted August 6, 2021 add some advance (upto 10°) under partial load by using the vacuum....but you do not need rolling road for this....just a passenger with a laptop Quote Link to post Share on other sites
Z320 Posted August 6, 2021 Report Share Posted August 6, 2021 Btw, and shure most of you know, the vacuum for the distributor advance unit is caused by Venturi by the airflow passing the trottle butterfly, it us not the vacuum in the inlet manifold. I posted what I measured on my HS6 some years ago at another forum, I have to search for, if there is interest about. Quote Link to post Share on other sites
Tim D. Posted August 6, 2021 Report Share Posted August 6, 2021 1 hour ago, JochemsTR said: add some advance (upto 10°) under partial load by using the vacuum....but you do not need rolling road for this....just a passenger with a laptop Agree with adding some vac advance if you can. I run an Aldon amethyst programmable ignition on my supercharged 6. It used to be a bit bucky at low revs through town. Adding vac. Advance sorted it out and I can use leaner mixtures at cruise which is probably why I get 30 mpg :-) Quote Link to post Share on other sites
Z320 Posted August 6, 2021 Report Share Posted August 6, 2021 (edited) My experience with different engines, cars and mcs is: every engine runs best on all revs (also at tickover) on full advance (engine specific), while it better to start on late. So my advice is not to overdo with finding the correct curve, this is "digital" and like I do on my pre war Nortons with manual avance: late to start them, full advance from tickover to max revs, some deg. less on heavy load, some deg. more on higher revs (advance unit), back to late ignition when you stop the engine for the next start. Edited August 6, 2021 by Z320 Quote Link to post Share on other sites
John L Posted August 6, 2021 Report Share Posted August 6, 2021 Has anybody tried changing the max mechanical advance in the std non vacuum distributor, by modifying the beak on the weight mechanism to give a bit ore advance at higher engine speeds? John Quote Link to post Share on other sites
BlueTR3A-5EKT Posted August 6, 2021 Report Share Posted August 6, 2021 Did it the other way Welded a blob on the finger to reduce the mechanical advance, and filed it to the degrees I was told I needed. No idea if I improved things, as the performance was not transformed on my Morris Minor. Quote Link to post Share on other sites
Hamish Posted August 6, 2021 Report Share Posted August 6, 2021 It’s that what the distributor doctor is for ? says he who uses an accuspark ! Quote Link to post Share on other sites
Z320 Posted August 6, 2021 Report Share Posted August 6, 2021 3 hours ago, John L said: Has anybody tried changing the max mechanical advance in the std non vacuum distributor, by modifying the beak on the weight mechanism to give a bit ore advance at higher engine speeds? John Hi John, if you want this, why ever, I guess you need onother advance unit. They have been made in plenty variations. Which TR model do you drive, please? Ciao, Marco Quote Link to post Share on other sites
harrytr5 Posted August 6, 2021 Report Share Posted August 6, 2021 On 8/5/2021 at 10:40 AM, Adrian Steele said: I have fitted the 123 Tune distributor to my six to replace the worn Lucas distributor. It now runs so much better so I clearly hadn't appreciated how worn the old one was. I have played around with the advance curve settings to get what feels like the optimum so thought it would be a good idea to check/adjust it finally on a rolling road. One near me is Turner Mechatronics in Hemel Hempstead who besides tweaking modern cars claim to be capable working with classics including TR6s. Problem here was the expert mechanic was adamant that I should have a vacuum to the distributor otherwise it will never run properly and then proceeded to lecture me about this retrograde modification - "nothing wrong with the Lucas dizzy but it needs vacuum." I got concerned when he said he could adjust the metering unit (MU) if it needed it. Alarms bells ringing now, because if he thinks a six has to have a vacuum to the distributor then he is not that knowledgable so I wanted him no where near the MU. I took the car away with no work being done, but had to pay 1 hour labour for the ten-minute conversation to get my keys back despite him never touching the car!! In short - looking for recommendations of someone trusted in Bucks/Herts/Oxon area with rolling road capability and TR6 KNOWLEDGE. I will PM you and you escaped lightly Regards Harry Quote Link to post Share on other sites
Peter Cobbold Posted August 6, 2021 Report Share Posted August 6, 2021 The reason for having vac advance at cruise ( hence the butterly edge take-off to the capsule) is to allow longer combustion time for lean cruise mixtures. This applies to most engines but not to the PI. The PI does not run lean at cruise in order to avoid pinking when the throttle is floored. The PI lacks an accelration charge device so has to be run rich even at cruise. If it is set lean at cruise there will be a "lean spike" when flooring the throttle and the pistons will rattle from detonation. SO the PI lacks acceleration charge, the cruise mixture is rich and that in turn means that vac advance is not required and indeed would be undesirable. Using disy settings as per the Lucas PI disy and having no vac advance will be correct for PI fuelling. Peter Quote Link to post Share on other sites
Peter Cobbold Posted August 6, 2021 Report Share Posted August 6, 2021 The lack of acceleration charge in the PI leads to a lean spike and fuel fractionation in the inlet manifold such that, if run weak at cruise, the mixture upon wotting the throttle becomes briefly very low octane. That pulse of lean, low-RON mixture detonates and the engine rattles its pistons (pinks). Details here:https://supertrarged.wordpress.com/2013/06/12/the-lucas-pi-lean-spike/ Peter Quote Link to post Share on other sites
Tim D. Posted August 7, 2021 Report Share Posted August 7, 2021 Peter’s comments are 100% correct. I tuned my MU to lean out cruise as much as possible.. wanted more MPG and less unburnt petrol smell. But you soon hit a limit where you have a transient week spot on acceleration (easy to see on an AFR meter). Quote Link to post Share on other sites
Z320 Posted August 7, 2021 Report Share Posted August 7, 2021 (edited) This is the vacuum pickup at my old HS6 The next photo is from the engine side, the butterly is some degrees open for the photo. The bore ends direkt above the butterfly, at tickover it is closed and the advance unit does not work. This is why the pickup is not the vacuum in the inlet manifold, indeed in this position it is an indication for the airflow. How and in which situations it works could be worth another post.... Edited August 8, 2021 by Z320 Quote Link to post Share on other sites
Peter Cobbold Posted August 8, 2021 Report Share Posted August 8, 2021 The butterfly edge port works when the butterfly is opened by 30deg or less, but not completely shut. The butterfly at these openings is dictating engine speed and it does that by limiting the mass air flow in the gap. The air flow is limited because its velocity is sonic, meaning it is at the speed of sound so cannot move faster. The pressure in the a manifold needed to induce sonic air flow is half atmospheric, and that is the pressure that is found at the butterly edge in sonic flow. Sonic flow is also known as "choked" flow. When the buttterly is fully closed and the engine is in the over-run (eg downhill, or slowing the car ) the manifold pressure can go to near vacuum, but that is not transmitted to the butterfly-edge port. When the engine is accelarated by opening the butterfly fully the manifold pressure rises to near atmospheric and that is sensed by the port. In this way the vac advance capsule works to advance the spark only when the butterfly is in the cruise positions, less than 30 deg open but not shut. The cruise manifold pressure when the butterly flow is sonic is consistently around half atmospheric and that is used to actuate the vac-advance capsule to give more time for combustion of the lean cruise mixture and the lower compression. Combustion explained in the talk I gave at IWE Lincoln: https://supertrarged.wordpress.com/2016/07/21/iwe-2016-technical-seminar/ slide 61 et seq are relevant Peter Quote Link to post Share on other sites
Peter Cobbold Posted August 8, 2021 Report Share Posted August 8, 2021 slides 91 et seq describe acceleration charge ,the PI lean spike and pinking from fuel fractionation. Slide 100 is HSM's disy recurve and static retime to allow the PI to be set less rich without pinking on 95 RON. Quote Link to post Share on other sites
Z320 Posted August 8, 2021 Report Share Posted August 8, 2021 (edited) Hi Peter, my experience is more practical from what I measured on the port while driving and in the result about the same. Simply said: more driving fun with the advance unit connected and working. To late today, I will tell the next days what I know from my point of view. Ciao, Marco Edited August 8, 2021 by Z320 Quote Link to post Share on other sites
JochemsTR Posted August 9, 2021 Report Share Posted August 9, 2021 I am confused, I thought this was about a PI with 123Tune with Vacuum Advance curve. Quote Link to post Share on other sites
Z320 Posted August 9, 2021 Report Share Posted August 9, 2021 (edited) Hi Jochem, this is why I will make an extra thread about the original distributor. I would be very pleased if Peter joins it with his knowledge. Everbody than can transfer this to the 123. As I know nothing about the 123 I have to ask how you get a vacuum advance curve on it? Do you really pick up the vacuum (which vacuum?) and use it for calculation on the 123, or do you simply add extra degrees according the revs of the engine? Ciao, Marco Edited August 9, 2021 by Z320 Quote Link to post Share on other sites
astontr6 Posted August 9, 2021 Report Share Posted August 9, 2021 On 8/6/2021 at 9:45 PM, Z320 said: Hi John, if you want this, why ever, I guess you need onother advance unit. They have been made in plenty variations. Which TR model do you drive, please? Ciao, Marco Hi Marco! Is this why SAH, the tuning Guru in the 1970's, years ago fitted a different spring to the Lucas dizzy when they tuned TR6's??? Bruce. Quote Link to post Share on other sites
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