Fireman049 Posted March 7, 2015 Report Share Posted March 7, 2015 (edited) I've just found a company that sell Bosch 4 electrode spark plugs suitable for all four cylinder TR's. The plugs have a thread length of 12.7mm. and cost £16.54p (free postage) for a set of four. The part no. is WR78G. Contact details: sales@allcarpartsdirect.co.uk. They are located in Sittingbourne. I've ordered a set for my 3A. Tom. Edited March 7, 2015 by Fireman049 Quote Link to post Share on other sites
Guest Posted March 7, 2015 Report Share Posted March 7, 2015 (edited) Interesting! I put the Beru version of these in my Spitfire 1500 back in the mid 90s and in my Saab 96. On both occasions something weired happened after restart: the 'idle' revs went up to about 1700 rpm and stayed there for a few minutes! Then it settled down to a modest 800 or so rpm. On both occasions I had to reset my carbs + CO2 level. My guess is that the these improved plugs burned away (small) carbon deposits inside the head and cylinders. Menno Edited March 7, 2015 by Menno van Rij 2 Quote Link to post Share on other sites
RogerH Posted March 7, 2015 Report Share Posted March 7, 2015 Hi Tom. keep us update on what happens when you put them in. Have you got a new set of the plugs that you usually use. It would be interesting to fit these forst and run it for a few miles to see what the standard is. Then put the 'Tetrodes' in. Roger Quote Link to post Share on other sites
Fireman049 Posted March 7, 2015 Author Report Share Posted March 7, 2015 Thank you Menno and Roger ~ Roger ~ At the moment my engine isn't ready to be run due to the total rebuild. I shall take your advice and run her with the normal NGK BP6HS plugs for a few hundred miles and then fit the Bosch plugs and compare performance. I'll certainly keep you posted ~ Watch this space! Keep smiling ~ Tom. Quote Link to post Share on other sites
Guest ntc Posted March 7, 2015 Report Share Posted March 7, 2015 Bye bye pistons Quote Link to post Share on other sites
Guest Posted March 7, 2015 Report Share Posted March 7, 2015 Bye bye pistons huh? M. Quote Link to post Share on other sites
Nick Jones Posted March 7, 2015 Report Share Posted March 7, 2015 Bye bye pistons What, again?? The earth is actually round you know! Or are you just winding us all up......? You should try some - you might even like them...... every one else who has tried the 3 electrode plugs has, (and not a melted piston in sight). I'd expect the 4 electrode plugs to give the same benefits because they share the side-electrode layout. Nick Quote Link to post Share on other sites
Guest ntc Posted March 7, 2015 Report Share Posted March 7, 2015 It will all come out in the wash Quote Link to post Share on other sites
JohnG Posted March 7, 2015 Report Share Posted March 7, 2015 Neil When I decided to use BUR6ET plugs in my '6' last month, you were distinctly cool about the idea In order to broaden my knowledge at least and the knowledge of the TR community as a whole, could you expand on your lack of enthusiasm for multi electrode plugs please? I am genuinely interested to learn. Quote Link to post Share on other sites
Peter Cobbold Posted March 7, 2015 Report Share Posted March 7, 2015 This paper shows multiple ground electrode plugs are worse at cycle by cycle variability ( ie they give a higher COV): http://www.sciencedirect.com/science/article/pii/S2090447912000883 "Multiple ground electrode designed spark plugs significantly slow down the early flame development, due to the increase in heat loses and the reduction in flame growth due the restricted flow directions." - so they should result in rougher running than the standard plug. Why TRrers are finding the opposite I dont know. Peter Quote Link to post Share on other sites
Peter Cobbold Posted March 8, 2015 Report Share Posted March 8, 2015 One possibility is the multiple ground electrodes may allow the central electrode to run hotter by shielding it from cooling blasts of intake air: http://www.stealth316.com/images/spt-heatinout.jpg A hotter running live electrode requires less breakdown voltage, as this 90 year old paper shows: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091244.pdf The central electrode heat range is about 400-800C in modern plugs too. The poor COV due to the multiple ground electrodes cooling the kernel (post 10 above) may be more than offset by a better spark from the hotter cathode in TR engines. This analysis assumes that the spark was not improved in the experimental engine of post 10. Peter Quote Link to post Share on other sites
Alec Pringle Posted March 8, 2015 Report Share Posted March 8, 2015 Neil isn't the first person I've noted offering cryptic concern about pistons. I heard similar comments more than 20 years ago as a motor factor. As I have previously observed, personal experience suggests that multi-electrode plugs offer more benefit in some types of engine than in others, but whether there are any reasonable rules enabling us to forecast improvement, or otherwise, I know not. One thing I have yet to see is a piston of older generation engines damaged by newer plug designs - that is not to deny the possibility of such a thing happening, I just haven't experienced it . . . . . nor yet seen any evidence of it. Apocryphal accounts yes, theoretical concerns yes, empirical evidence not as yet . . . . Chapter and verse anyone ? Cheers Alec Quote Link to post Share on other sites
Guest ntc Posted March 8, 2015 Report Share Posted March 8, 2015 Alec About the same time scale if not more alas,granted not a Tr however a ford crossflow built and dyno set up by QED for rallying ie Cosworth pistons steel crank etc you know what I mean so three events later the buzz word was this type of plug.I asked QED about this at the time was advised against it not correct unless the plug is central to the piston,this like a fool I ignored this and sure enough the next event massive engine failure the engine went back to QED for check and guess what one holed piston due to a spark plug tip melting and the rest was also close,one very expensive lesson learned.The physics around this I do not know maybe Peter can shed some light? Quote Link to post Share on other sites
Don H. Posted March 8, 2015 Report Share Posted March 8, 2015 One possibility is the multiple ground electrodes may allow the central electrode to run hotter by shielding it from cooling blasts of intake air... There are also hypotheses that the greater thermal mass of the additional electrodes will allow the plug to run hotter, promoting detonation. The 3.4L 5VZ-FE on my Toyota Tacoma has dual-electrode plugs as original equipment, and I stay with them. Seems kinda gimmicky to go with multiple electrodes on a car not originally designed for it, IMO. I used to play with stuff like that in my cars (not TRs) as a kid, and never really saw any advantages. I mostly ignore upgrades like that these days. Old skool for me. What do you expect to get from the 4-electrode plugs, Tom? (And BTW -- when is this car about which we've followed so many upgrades gonna take to the road? We're lookin' forward to it.) Quote Link to post Share on other sites
Fireman049 Posted March 8, 2015 Author Report Share Posted March 8, 2015 Greetings Don ~ I really don't know what to expect from the plugs ~ it's merely a short term experiment. Regarding my TR. I'm now in the process of putting everything back together. If I hadn't carried out so many modifications she would have been on the road way back! Mind you, going on so many sea cruises hasn't helped progress!! Hopefully, later on this year she should be back 'on the run'! (but we're going on another four week cruise in April to New Orleans and other destinations). Best regards ~ Tom. Quote Link to post Share on other sites
Peter Cobbold Posted March 8, 2015 Report Share Posted March 8, 2015 (edited) Alec About the same time scale if not more alas,granted not a Tr however a ford crossflow built and dyno set up by QED for rallying ie Cosworth pistons steel crank etc you know what I mean so three events later the buzz word was this type of plug.I asked QED about this at the time was advised against it not correct unless the plug is central to the piston,this like a fool I ignored this and sure enough the next event massive engine failure the engine went back to QED for check and guess what one holed piston due to a spark plug tip melting and the rest was also close,one very expensive lesson learned.The physics around this I do not know maybe Peter can shed some light? Neil, An over-heated electrode is the silent killer, through preigntion. I guess the failed piston looked as if a blow torch had melted it? Perhaps the plugs of the correct heat range for the application? If they were too hot then that would explain why all four pistons suffered, and not a chance event. I dont know how plug manufacturers relate the heat ranges of a given J-plug to their wire plugs or their multi-electrode plugs, but they can. Peter A single earth electrode takes up ca 8% of the plug's total heat flow: http://www.stealth316.com/images/spt-heatinout.jpg So a three-ground plug might well take up more heat from combustion, which would be partly compensated by faster loss to the cool intake mixture. But most of the heat taken up by the exposed part of the plug ( 80%) doesnt go to the intake air it goes into the steel casing and into the cylinder head. So each ground electrode might tend to run a bit hotter than a standard single electrode - But the plug manufacturers would design to prevent them getting overhot. I dont see the new plug types being damaging as long as the heat range is appropriate for the TRs and only the manufacturers can tell us that. For his supercharged TR6 application John Jervis had excellent advice from NGK on the correct heat range of their Iridium wire plugs - from his blog post: """I contacted NGK regarding the S/C by email via their UK web site with all detail and scenarios I could think of. They called me 10 minutes later! Basically they know of the Moss kit: I didn’t tell them. They asked if that what was fitted and whether the upgraded boost pulley was fitted. Their recommendation is to go up one or two plugs cooler, there is a 3rd cooler but they thought that would be too much even for hot climates in Europe. The Iridium plug they recommend is BPR7EIX or BPR8EIX, there is also a 9. I did mention the problem of knock affecting iridium plugs but in NGKs’ opinion it should not be a problem unless I have a poor set up or a problem anyway. The guy I spoke to did say that if it does suffer severe vibration from detonation it was possible to damage the iridium plugs but since a lot of race cars use iridium plugs he does not think this should be an issue, all things being equal of course! So NGK Iridium plugs it will be.""" Peter Edited March 8, 2015 by Peter Cobbold Quote Link to post Share on other sites
Guest ntc Posted March 8, 2015 Report Share Posted March 8, 2015 (edited) Peter The piston was holed due to the tip of the plug melting off if I had pics from then I would post them,my point being that the engine was built and set up by those that know and I ignored there professional advise and paid the price.We went on to use Champion R with no issues,ie there is no tip. Big download but worth the read at the end http://www.motospecs.com.au/assets/files/downloads/Champion_Spark_Plugs_Catalogue_2010(V1s).PDF Edited March 8, 2015 by ntc Quote Link to post Share on other sites
JohnG Posted March 8, 2015 Report Share Posted March 8, 2015 Tom Hope you are OK with my putting my two penneth into your post Neil / Peter Thanks both. I don't claim to understand all the deeper technical stuff, but, what my brain can compute is the potential for melting tips and the need to be aware of temperature ratings. I my case, I was careful to get multi electrode plugs of the same temperature rating as the original plugs, however, from reading your words, I should be down a couple of steps. Following the above, regular checks of the plugs are now on my 'routines' list. I will only be doing about 3k or 4k this year, in reasonably short doses, so, hope all will be well. If I hit a point where you could say "told you so", I will swallow my pride and let you know, via this forum Again, thanks for the info. Quote Link to post Share on other sites
Peter Cobbold Posted March 8, 2015 Report Share Posted March 8, 2015 (edited) I'm not sure what advantages the multiground plugs bring to TRs. Is it smoother running, easier starting? Maybe the younger generations ( sad, that plural) compare a TR engine with moderns and expect it to run equally smoothly? While the oldies are happy with cranking and making do with whatever they have been used to for...decades. TRs were modern once, warts and all. Or is the improvement real? after all, the fuel has changed enormously, no going back there. Peter Edited March 8, 2015 by Peter Cobbold Quote Link to post Share on other sites
JohnG Posted March 8, 2015 Report Share Posted March 8, 2015 (edited) Peter I am, my children and grandchildren tell me, old. As a kid, my dad had Standard 10 / V8 Pilot / Humber Super Snipes / Triumph 2000 My 1st cars were minis / Mk2 Cortinas, always modified one way or another, so my expectations are, I think, reasonable. My lack of experience is in PI, it is why I try to listen to all the opinions on this forum and am not going to dismiss any, without trying them first. All I would like, and have almost achieved, is a 6 pot start and the elimination of that dead spot as I pull away, cold. I accept that the latter is going to be more difficult to achieve than the former, however, both are much less obvious than they were when I bought the car. This has been achieved with small changes in a number of areas, which I feel, is usually the case. Edited March 9, 2015 by wjgco Quote Link to post Share on other sites
Peter Cobbold Posted March 8, 2015 Report Share Posted March 8, 2015 John A tug on the 'choke' was what I used and throttle blips. Because the PI has no fuel enrichment to match the SU damper or Weber throttle pump, it is going to be somewhat lacking in transient response until warmed up.* Blipping the throttle doesn't richen the mixture like carbs do, but will heat up the TRs plugs usefully. Lack of transient enrichment means (without choke) the stone cold PI engine is trying to pick up with a lean mixture, and that might be improved by modern plugs designed to light lean mixtures. But its not going to match the cold pick-up of the Mini or Cortina. Peter * and even when hot it is not ideal: https://supertrarged.wordpress.com/2013/06/12/the-lucas-pi-lean-spike/ Quote Link to post Share on other sites
JohnG Posted March 9, 2015 Report Share Posted March 9, 2015 (edited) Peter An interesting article Things are never as simple as they should be; squirt some fuel in . . .big bang . . .lots of fun! A couple of thoughts; I would have thought that the manifold heating up would have had a positive effect on the atomising of the fuel mixture. If this is the case, is this the reason that the lean spike becomes less obvious as the engine warms? I know that everything is happening fast; at 3000rpm, the sytem is completing 50 revs per second, which, by my calculation is 25 "squirts" of fuel per cylinder, or 150 "squirts" over the 6 cylinders In a mechanical system, which, by it's very nature, will be built to tolerances and will have backlash built in, I guess it is no surprise that, when combined with the complexities of delivering the appropriate amount of fuel, mixed in exactly the right way, we are faced with an uphill struggle to get it right. It's fun trying though! Anyway, if I reach a point where I decide enough is enough, Clive Manvers is only 60 miles away and Mark at Classic Marks is only 80 miles or so from here. Edited March 9, 2015 by wjgco Quote Link to post Share on other sites
Peter Cobbold Posted March 9, 2015 Report Share Posted March 9, 2015 (edited) John, The PI intake manifold isn't heated, which is good for power (heat reduces density of the charge) but not good for reducing wall wetting with fuel. As the fuel evaporates off the walls the runners will tend to cool down. A fully evaporated stoichiometric mixrue is about 18deg C below ambient. So walls run cold. I suppose it could be possible to add hot spots in the floor of the six runners..... A stone cold engine needs a very rich mixture- way, way richer than in normal running. The choke provides this. The reason is that only a small fraction of petrol is volatile enough to vapourise in a cold motor. And the spark will only ignite vapour not liquid petrol. Once the engine has fired a few cycles the plugs work better and the temperature rise in the combustion chamber improves evaporation of liquid petrol that passes the inlet valve. So after a few seconds the choke should no longer be needed. Blipping the throttle helps carburetted engines dipesnse with choke because each blip pumps extra fuel ( Webers) or richens the mixture with the damper ( SUs) - but Lucas PI cant do that. Even so, I used to use blipping: each throttle opening adds more fuel via the MU diaphragm seeing pressure closer to atmospheric as the engine is acclerated briefly. So each engine acceleration adds more heat and speeds up warmup. Yes it is amazing that mechanical metering works at all, each squirt is tiny.** Yet AFR measurements that have been made show the mixture control with the PI is pretty stable. Its problem is lack of 'acceleration charge'. Put it down to its racing pedigree ! Peter **At full throttle each squirt is I reckon only about 0.035 cc (Atmospheric air is 1.225 g per litre or 0.4g per intake ( 80% of one cylinder displacement). Stoich AFR is about 7% petrol by mass, so one squirt = 28mg = 35microlitres. Thats 0.035 cc.or 35 cubic millimeters. Its equivalent to a cube with sides just over 3mm. And for leaner mixtures the volume is smaller still ! Edited March 9, 2015 by Peter Cobbold Quote Link to post Share on other sites
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