terryj Posted September 16, 2021 Report Share Posted September 16, 2021 Having seen discussions on use of these spark plugs I am a bit confused regarding W78, WR78 and WR78X. I want to try these in a Vitesse 2l Mk2 but don't know which to order. I note Pete's comments about not ordering plugs with an R in the number but also others have used WR78 satisfactorily. Green Spark Plug Co. are out of stock of W78 but do have WR78 and there are some on ebay WR78X. Is there any difference and which would you recommend please? Terry Link to comment Share on other sites More sharing options...
johny Posted September 16, 2021 Report Share Posted September 16, 2021 Not sure what the X means but R indicates this plug (or ones from other manufacturers) has an additional small internal resistance which helps reduce the radio interference generated by the passing of the high voltage current. This obviously causes a voltage drop but how much effect it has on the quality of the spark is the subject of ongoing debate☺️ Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 16, 2021 Report Share Posted September 16, 2021 this is pretty conclusive that yes its on a motorbike but some simple comparisons show a non resistive managed around 30kv the resistive plug managed 13kv its does go on a while but proves the resistor is corking up the HT A LOT Link to comment Share on other sites More sharing options...
johny Posted September 16, 2021 Report Share Posted September 16, 2021 Trouble is ignition and combustion are a complicated subject and of course vary from one engine to the next. I think spark energy and duration come into it not just the voltage generated and then of course one engine might need the best spark possible to achieve maximum combustion efficiency while another can still do the same with less spark... Link to comment Share on other sites More sharing options...
terryj Posted September 17, 2021 Author Report Share Posted September 17, 2021 Thanks Johny and Pete. The video does indeed show that non-resistance plugs appear to be preferable so I phoned Green Spark Plug Co. to ask when their W78 plugs would be back in stock and was told that they are now obsolete. They suggested WR78 plugs would still do the job adequately. Terry Link to comment Share on other sites More sharing options...
johny Posted September 17, 2021 Report Share Posted September 17, 2021 Resistance plugs seem to be ok for modern engine manufacturers who you'd think would find an alternative if there was a reduction in ignition/combustion efficiency. Thats not to say they dont make a difference in older design engines but without some controlled testing on each model who's to say.... Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 17, 2021 Report Share Posted September 17, 2021 the number i have changed with missfires on R plugs needs two hands to count on, there again most are NGK and you need to add in problems of rich running contaminating the unglazed insulator which was discussed in the spark plug posting a good while back hence suggestions of bosch W78 which have themselves become rare i wouldnt touch anything with an R in the prefix reducing the HT KV by such a large degree cant be beneficial how ever you look at it. Pete Link to comment Share on other sites More sharing options...
Nigel Clark Posted September 17, 2021 Report Share Posted September 17, 2021 I've used Bosch WR78 and NGK BUR6ET multi-electrode plugs successfully in Triumph four and six pot engines for about 15 years. Sorry to contradict, but my experience is that I've had absolutely no problems with these resistive plugs, indeed they've given easier starting, smoother idling and crisper acceleration than the standard non-resistive single electrode plugs. all a little subjective, and merely my experience. If the ignition system is in good condition, I would say resistive plugs are perfectly suitable for our cars. Nigel 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 17, 2021 Report Share Posted September 17, 2021 Nigel thats good there's always two sides to a story ha but the test showing such a large reduction in an already weedy HT makes no sense to maybe just me Pete Link to comment Share on other sites More sharing options...
Chris A Posted September 17, 2021 Report Share Posted September 17, 2021 I've been following this discussion just out of idle curiosity. It seems that the R type plugs may be ok, but there are cases of them not being so. In that case what is the advantage of using them? If the car is equipped with electrical stuff that could suffer from interference then I would say there is a case for considering them. Otherwise do they improve engine performance? This seems far less clear to me. Them there is the other point raised here, multi electrodes. The case for using them rather than single electrodes does seem to be more in their favour if a) High mileages are done b) getting at the plugs to re-gap them is difficult or a chore. In the end it comes down to what works for each person/car, as long as the pros and cons are known. In my case I run my 13/60 on NGK BP6ES and am happy with them, bought from my local car spares specialist so have confidence they are genuine not copies. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted September 17, 2021 Report Share Posted September 17, 2021 36 minutes ago, Chris A said: In the end it comes down to what works for each person/car, as long as the pros and cons are known. I think I tried about every available version at one time then realised I wasn't doing either the speed or the mileage to justify most of them. In the end I went for standard single terminal plugs, although I was recommended Brisk motorcycle plugs and have bought four to test at some future stage. Link to comment Share on other sites More sharing options...
Chris A Posted September 17, 2021 Report Share Posted September 17, 2021 1 hour ago, Colin Lindsay said: I wasn't doing either the speed or the mileage So not driving fast, just Briskly then . . . 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 18, 2021 Report Share Posted September 18, 2021 back to basics many places only sell R plugs as the demand is more aimed at moderns than Non R for older cars and less sales volume if its not the specified plug why would you want to ?? yes upgrades when its "better" but this might work but R makes no sense bit like putting your finger in the dyke to cork it up we need all the spark you can get , why strangle it ??? pete Link to comment Share on other sites More sharing options...
avivalasvegas Posted September 21, 2021 Report Share Posted September 21, 2021 Anyone know what the X in W78X stands for? It took me a long time to find a full set of W78 plugs. The last two are currently on their way from Italy. I really hope they live up the forum's hype Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 21, 2021 Report Share Posted September 21, 2021 x was always the unknown factor ??? Pete Link to comment Share on other sites More sharing options...
terryj Posted October 4, 2021 Author Report Share Posted October 4, 2021 Thought you may like an update on this. Originally the engine would rev OK but was woolly and perhaps missing a little at high revs. All plugs (NGK) were firing and a nice colour brown. I fitted a new set of WR78 plugs and took the car for a short test drive taking it up to 4500 rpm in the gears and it accelerated and ran beautifully all the way. So it would seem that one of the old NGK plugs was probably breaking down at high revs. Certainly the WR78's have made a noticeable improvement. Thanks for everyone's comments - they were informative and very helpful. 1 Link to comment Share on other sites More sharing options...
Chris A Posted October 4, 2021 Report Share Posted October 4, 2021 To confirm if the improvement is really due to the WR78s you should but a new set of NGKs in and take it for a run to compare the results. Link to comment Share on other sites More sharing options...
Badwolf Posted October 4, 2021 Report Share Posted October 4, 2021 What about getting a set of everything and doing a comparison report for us all Link to comment Share on other sites More sharing options...
Iain T Posted October 4, 2021 Report Share Posted October 4, 2021 On 16/09/2021 at 18:20, johny said: Not sure what the X means Johny, Just read this thread, I believe the X denotes 1.1mm gap which is too wide for our cars. Iain Link to comment Share on other sites More sharing options...
Chris A Posted October 4, 2021 Report Share Posted October 4, 2021 1 hour ago, Badwolf said: What about getting a set of everything and doing a comparison report for us all There's a good idea, you are a bright spark ! Link to comment Share on other sites More sharing options...
avivalasvegas Posted January 16, 2022 Report Share Posted January 16, 2022 Pictured are two new Super 4 W78 plugs. No “R” and no “X”. Anyone know why they have different numbers printed on them? Link to comment Share on other sites More sharing options...
Chris A Posted January 16, 2022 Report Share Posted January 16, 2022 At a guess to identify when/where manufactured. Batch number/factory code. For example the 2 screw on tops are clearly made from different metals so different batches at least. More importantly, do they work. Link to comment Share on other sites More sharing options...
Steve P Posted January 16, 2022 Report Share Posted January 16, 2022 I have run my 2.5 Vitesse on the 3 prong Bosch ones for a couple of years now, does seem smoother on pickup,i am running a standard dizzy atm albeit with an electronic module.Will see what happens when i put the 123 Tune one in. Steve Link to comment Share on other sites More sharing options...
avivalasvegas Posted January 16, 2022 Report Share Posted January 16, 2022 38 minutes ago, Chris A said: At a guess to identify when/where manufactured. Batch number/factory code. For example the 2 screw on tops are clearly made from different metals so different batches at least. More importantly, do they work. Will find out in a couple weeks when I put them in! Wasn't easy finding these now obsolete W78s. Link to comment Share on other sites More sharing options...
Badwolf Posted January 16, 2022 Report Share Posted January 16, 2022 Typical..supply and demand. Great product but limited market. Lasts for ages so limited extra sales Limited sales means nobody wants them so discontinue them Eventually wear out so none now available Next thing cheap oriental rip off so everyone now buys them They don't work properly so nobody buys anymore Spare part madness!! KYB shock absorbers anyone? Link to comment Share on other sites More sharing options...
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