Tim D. Posted August 30, 2014 Report Share Posted August 30, 2014 Not sure whether it is a perfect cure but in theory you could adjust the mu to weak at low altitude and then richen up with the choke. Then as you climb you can release the choke. Of course this would be much easier with a wideband on the exhaust. Tim Quote Link to post Share on other sites
Peter Cobbold Posted August 30, 2014 Report Share Posted August 30, 2014 Thank you Peter, seems a nice winter project in any winter to come ;-) Drove the Stelvio and several other high alpine passes, the car was not very happy there. No stalling or plug cleaning but the smoking and severe loss of power I remember. Can't be good for the engine. Regards, Willem I like Stuart's servo driven MU. That could be controlled by a UEGO signal to give a constant AFR. Not only for altitude. If the motor works fast enough it will kill the lean spike and pinking upon acceleration. Needs electronic expertise for the control circuit. Peter Quote Link to post Share on other sites
Andy Moltu Posted August 30, 2014 Report Share Posted August 30, 2014 Wonder if there are still any metering units available that were fitted on TR6's dispatched to Switzerland,they were fitted with the barometric devise but must be very rare these days. Â Some of the high altitude spec ones didn't have the the compensation device fitted - the mixture was simply set leaner - OK until you drop down to lower altitudes. Quote Link to post Share on other sites
Tim D. Posted August 30, 2014 Report Share Posted August 30, 2014 Peter Yes that could be the answer. Might need a slightly dampened control system as I could imagine some fun resonances. Quote Link to post Share on other sites
jean Posted August 30, 2014 Report Share Posted August 30, 2014 Yes Andy, these were probably the CP specification units mentioned by Derek. I wonder how they coped with idle at lean mixture or did they only lean it out in the mid and high range. This must not have been a ideal compromise I'm glad to have stored the MU of my 6 in a box..... Quote Link to post Share on other sites
Peter Cobbold Posted August 30, 2014 Report Share Posted August 30, 2014 (edited) Peter Yes that could be the answer. Might need a slightly dampened control system as I could imagine some fun resonances. Tim, I think a UEGO responds in a couple of milliseconds so the circuit may well need damping, although I suspect the motor drive will be slow to respond in comparison. I have a spare MU-castle to donate to the cause if you're minded to try it. Peter Edited August 30, 2014 by Peter Cobbold Quote Link to post Share on other sites
Peter Douglas Winn Posted August 31, 2014 Report Share Posted August 31, 2014 Jean The first TRs in Swizerland had the pictured metering unit with an altitude compensator. Later on the main importer told Triumph that they did not need it. They had found out that when the car was properly set up, the customers had no problems with the high passes. I know that when the CO value is about 2.2 to 2.5 you can make all Swiss passes. I think the main problem today is a lot of the engines and ancilleries are old and not up to scrach. They drive OK up to 70 mph but when one wants to do a long tour with high passses the problems arise. Quote Link to post Share on other sites
saffrontr Posted August 31, 2014 Report Share Posted August 31, 2014 Peter / Jean,  The latest build record of a TR6 recorded with a high altitude metering unit was CR6641LO bound for Switzerland so it could be that the importer or indeed Triumph removed these on arrival / before despatch from the factory and fitted a normal unit? Bit of a puzzler all the same why they should fit them in the first instance if they weren't needed.  cheers  Derek Quote Link to post Share on other sites
Marc R Posted August 31, 2014 Report Share Posted August 31, 2014 (edited) In the '80 & '90, I drove few times the TR6 full of luggage plus 2 set of shies (w/ the Hard Top) into to the Alps in Val Thorens (alt. 2300m), I noticed a lower response from the engine but did not faced an issue with the plugs. Except on very high pass where the Lucas's system should face his own limitation, I intend to think that today our PI set up is most of the time too rich. What is your view? and what can be the appropriate level (rich vs lean) acceptable for a TR6 at sea level? Â Regards Edited August 31, 2014 by Marc R Quote Link to post Share on other sites
Peter Douglas Winn Posted August 31, 2014 Report Share Posted August 31, 2014 As far as I know the frim Emil Frey in Zurich were the main importer for Triumphs. Furthermore I talked to ex employeees. They told me the new factory cars were set up somewhat rich, hence the need for the high altitude metering unit Then they decided to set up the cars for going over mountaoins and comfortable driving, not for speed (very swiss). Marc it is easy to get a comsumption which is better the 28mpg with the Lucas system. So when you have this consumption, you won't have any problems with the mountains. Living in Germany with my triumphs 1 carb and 1 PI I have driven over many passes going to and from France annd Italy and never had a problem. Quote Link to post Share on other sites
jamesStag Posted September 4, 2014 Report Share Posted September 4, 2014 (edited) Peter, Marc & All, Just a comment that my 69 CP TR6 PI does average 29mpg on a run over a few checks. I've not adjusted the MU, just carefully balanced the butterflies which were way out from the prev owner. Car was much happier after that. I don't suffer any hesitation on WOT, and the plugs look a good colour, almost verging on too-light tan (see older plug thread from me). Yet people following me do still mention they can smell fuel, that said might just be nontechnical people not being used to a non catalyst exhaust! Â Sure I'm not driving any high altitude for that test, but I wonder what the MoT exhaust analyser would report? I know a friendly garage so perhaps I should find out unless Peter C says that without driving on the road the static test might be unrepresentetive... Cheers, j. Edited September 4, 2014 by jamesStag Quote Link to post Share on other sites
mike barrett Posted September 6, 2014 Author Report Share Posted September 6, 2014 Thanks everyone a very interesting thread. So if I fitted a UEGO sensor and readout do you think it is practical to tweak the mixture (by adjusting the MU) when in the Alps? I am hoping to go back next year and it would be nice to get up a few passes without changing the plugs! I also like Peters idea of artificially fooling the system that the pressure is higher than really is.... but difficult to test in East Anglian. BTW does it matter where the UEGO sensor is fitted in the exhaust system. Â cheers mike Quote Link to post Share on other sites
Peter Cobbold Posted September 6, 2014 Report Share Posted September 6, 2014 Thanks everyone a very interesting thread. So if I fitted a UEGO sensor and readout do you think it is practical to tweak the mixture (by adjusting the MU) when in the Alps? I am hoping to go back next year and it would be nice to get up a few passes without changing the plugs! I also like Peters idea of artificially fooling the system that the pressure is higher than really is.... but difficult to test in East Anglian. BTW does it matter where the UEGO sensor is fitted in the exhaust system. Â cheers mike MIke, If the exhaust pipe joints are completely air-tight a sensor can be poked up the tail pipe a couple of feet. But the correct way is to fit it about 2-3 feet from the exhaust manifold, sealed into the downpipe and positioned so condensation cant flow into the sensor. Â The difficult bit is what to adjust in the MU and how. Setting for altitude doesnt really need cockpit adjustment. A roadside fix before and after a climb should do the job. Â One possibility is to slide shimstock between the cam follower rollers (#18) and the end of the moving stop piston (#49): http://www.lucasinjection.com/LUCAS_BLOWUP.gif The shim has to move in and out with the piston. How thick? -do it by trail and error. You want to lean the mixture by about 20% at 1500 metres http://docs.engineeringtoolbox.com/documents/462/elevation_altitude_air_pressure.png So if the AFR is set normally, under load, to AFR13 then you want to shim it to give AFR=15.6. You can do this in east Anglia - though it will probably pink like mad briefly after flooring the throttle. There was an article years ago in TRAction describing the shim method for normal altitudes, taking up wear. Â Another way, which I've never tried, would be to pressurise the castle behind the plastic cover with a 12 v tyre pump and tank set to supply air at 20% above atmospheric pressure at sea level: about 3psig. It simply replaces the atmospheric pressure lost at altitude. A simple plastic bottle of a litre or so will hold 3psi easily. The pump is switched on at say 2.5 psig and off at 3psig by a pressure switch. Try Bailey and Mackay. Feed the air into the underside of the diaphragm - on the 'atmosphric pressure' pipe marked here: http://www.lucasinjection.com/Lucas%20page%2011%20fig%2010.jpg Seal the plastic cover. Some air will leak past the excess fuel pivot but probably not so much that the pump will have to work all the time. And with an adjustable pressure switch you could have cockpit control over a range of altitudes. Again, you can test it at home. Â Peter Quote Link to post Share on other sites
mike barrett Posted September 8, 2014 Author Report Share Posted September 8, 2014 Peter thanks, Will have to get a MU to play with before I touch mine. cheers mike Quote Link to post Share on other sites
Peter Cobbold Posted September 8, 2014 Report Share Posted September 8, 2014 Peter thanks, Will have to get a MU to play with before I touch mine. cheers mike Mike, The air pressure method would be better from that point of view. It only needs the air pipe to be attached to the existing pipe. Peter Quote Link to post Share on other sites
mike barrett Posted September 9, 2014 Author Report Share Posted September 9, 2014 Peter understood and agree but I am an engineer so would like to understand exactly how the MU works! Â cheers mike Quote Link to post Share on other sites
Peter Cobbold Posted September 9, 2014 Report Share Posted September 9, 2014 Mike, I'm not sure it would stand that level of scrutiny! The PI seems to me to be sadly deficient in the lack of a throttle pump or similar. If you're going to have a go at curing that as well as altitude compensation then I'll lend you my spare. With transient enrichment upon wot'ing the throttle the PI can then be run leaner at cruise, and wtih vac advance implemented, could be more economical. Peter Quote Link to post Share on other sites
Tony Millward Posted September 10, 2014 Report Share Posted September 10, 2014 What an interesting thread, it would be great to have a workable system for PI's....  Cheers  Tony Quote Link to post Share on other sites
JohnC Posted September 10, 2014 Report Share Posted September 10, 2014 Hi Peter, Out of idle curiosity, would your air pressure compensation method be a first step towards using the PI with a supercharger? Ignoring such trivial details like plumbing it all in, of course... Â BTW I used the shim approach to adjust my over-rich MU many years ago, before finding a local guru who took my AFR/"Hg chart and tweaked the MU properly. IIRC I used a template I saw in Technicalities for the shim profile, and ended up using a brass shim something like 20 thou. I arrived at the thickness by inserting a feeler gauge between the cam & follower in the CU and finding which gave the highest idle rpm. Crude but it worked. Perhaps one could take a selection of shims when touring and keep going up & down until the best was found. It wouldn't be quick, but could be fun Cheers, John Quote Link to post Share on other sites
Peter Cobbold Posted September 10, 2014 Report Share Posted September 10, 2014 (edited) Hi Peter, Out of idle curiosity, would your air pressure compensation method be a first step towards using the PI with a supercharger? Ignoring such trivial details like plumbing it all in, of course... Â BTW I used the shim approach to adjust my over-rich MU many years ago, before finding a local guru who took my AFR/"Hg chart and tweaked the MU properly. IIRC I used a template I saw in Technicalities for the shim profile, and ended up using a brass shim something like 20 thou. I arrived at the thickness by inserting a feeler gauge between the cam & follower in the CU and finding which gave the highest idle rpm. Crude but it worked. Perhaps one could take a selection of shims when touring and keep going up & down until the best was found. It wouldn't be quick, but could be fun Cheers, John Hi John, That gives an idea of how thick a shim would need to be to give 20% less fuelling at altitude- a lot more than 20thou I suspect. Â I would have liked to have kept the PI with the blower but was deterred by the risk of an injector going lean. If that happened there is as very high probaility of detonation and holing a piston. That might be avoided by feeding all the injectors into the blower intake, so a failed injector only leans the mixture by one sixth.That gives time for a lean alert to be raised. Under boost the engine makes more power and needs more fuel at each rpm. And the max fuel flow at max rpm has of course to be higher. By quite a lot. The Moss kit in standard form gives 6psi boost so we need about 40% more fuel flow at max rpm. It is possible that the excess fuel lever could be used but I dont know how much extra flow it can provide. The limit will be set by the moving end-stop in the rotor. But if it can supply enough then a boost-actuated excess lever would cover all combinations of boost and rpm. I cant see a way to use boost pressure to move the diaphragm more- I think the fuel cam follower cant go lower - it would fall off the piston. Â Â A simpler. way would be to use the Lucas PI unaltered for normal unboosted running and add a single fuel squirter to add more fuel according to boost and rpm. A single SU is much easier! Â Peter Edited September 10, 2014 by Peter Cobbold Quote Link to post Share on other sites
JohnC Posted September 11, 2014 Report Share Posted September 11, 2014 Hi Peter, Just rummaged around in the garage and found the pack of shims. They range from 2 thou to 10 thou, and I'm pretty sure the one I used (based on general grubbiness) was 5 thou. Just shows I shouldn't rely on memory at my age! Â Based on data I've collected over the years (probably from Lucas manuals, but possibly from measurements of my MUs), the MU shuttle has a diameter of 6mm and travel of 1.5mm at zero manifold vacuum (WOT), giving fuel delivery of ~42cc per 1000 strokes. So a 20% reduction at WOT would require a shim of 0.3mm, or ~12 thou, reducing fuel delivery by ~8cc/1000 strokes. The problem would of course be that you would lose that 8cc at all throttle openings, and it's a much higher % at part throttle. In fact I *think* fuel delivery at idle is about 8cc... Still, if you shimmed to get max idle rpm (i.e., optimum mixture) when you were at altitude you would at least have a safe starting point. Sadly there are no mountains high enough here in Oz for me to experiment! Â Cheers, John Quote Link to post Share on other sites
Peter Cobbold Posted September 11, 2014 Report Share Posted September 11, 2014 (edited) Hi Peter, Just rummaged around in the garage and found the pack of shims. They range from 2 thou to 10 thou, and I'm pretty sure the one I used (based on general grubbiness) was 5 thou. Just shows I shouldn't rely on memory at my age! Â Based on data I've collected over the years (probably from Lucas manuals, but possibly from measurements of my MUs), the MU shuttle has a diameter of 6mm and travel of 1.5mm at zero manifold vacuum (WOT), giving fuel delivery of ~42cc per 1000 strokes. So a 20% reduction at WOT would require a shim of 0.3mm, or ~12 thou, reducing fuel delivery by ~8cc/1000 strokes. The problem would of course be that you would lose that 8cc at all throttle openings, and it's a much higher % at part throttle. In fact I *think* fuel delivery at idle is about 8cc... Still, if you shimmed to get max idle rpm (i.e., optimum mixture) when you were at altitude you would at least have a safe starting point. Sadly there are no mountains high enough here in Oz for me to experiment! Â Cheers, John John, Fascinating measurements - first time I've seen them. And you have corrected a misconception I have been making. Â So at wot the standard MU delivers 42 ul per stroke ( 1microlitre being 0.001cc ). Or 42 x 6 x 3000 ul per minute at 6000rpm which is 756ml per minute. ((( Just checking: I work on basis of fuel flow =5.6 x HP, ml per minute, so 150hp needs 150x 5.6 = 840 ml per minute. ( very rich, for supercharged). So we agree.))) Â If that 756 delivery if from a 1.5mm excursion of the moving end-stop then a 20% reduction would need a shim of 20% of 1.5mm or 0.3mm which is 12 thou, as you say. And I think you are right in saying that at low loads fuelling will be lost completely. The shim is effect reduces the excursion of the end-stop from 1.5 to 1.2mm. So we lose the 0.3mm motion that covers low loads. In other words as the manifold depression increases going from wot to part-load the piston moves back in but comes to a halt 0.3mm too soon, supplying tickover fuelling when it should be giving around 20% load fuelling. So the fixed shim method wont work. It would have to slide into place as the engine approached wot. Or it would have to be tapered and slid into the correct position according to load.That's complicated. I hadn't realised that, thank you. Â The air pressure method would preserves the full 1.5mm motion so all throttles are covered. A 3psi air bias would ensure the cam always allows 20% less outward motion of the end-stop and its piston. That's 20 % less at all loads. Which is whats needed at altitude with 20% less air pressure. Â Cheers Peter Edited September 11, 2014 by Peter Cobbold Quote Link to post Share on other sites
mike barrett Posted October 23, 2014 Author Report Share Posted October 23, 2014 Over the weekend I meet a TR5 owner who had just come back from Stelvio. I asked him if he had the fuelling problem on the pass. His solution was to install a Lamda sensor and meter (same as I think Peter recommended) then adjusted the metering unit so that the mixture was slightly lean and then use the choke to adjust the mixture to optimum. Thus if he was at low levels he had the choke partly open and when going over high passes pushed the choke so that the mixture was not to rich. Neat manual solution but you can only do it if you have the lambda meter and can then control the mixture. Â regards mike Quote Link to post Share on other sites
Tim D. Posted October 23, 2014 Report Share Posted October 23, 2014 good solution.. had wondered whether it would be possible to do that with an Integral AFR... Tim Quote Link to post Share on other sites
Peter Cobbold Posted October 23, 2014 Report Share Posted October 23, 2014 Neat solution. I think it will be wideband AFR sensor ( a 'UEGO') rather than a lambda, which are very go/nogo in their signal. Peter Quote Link to post Share on other sites
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