Resistive Spark Plugs

[Pete Lewis]

My views are not cast in stone but many cars i seehave problems and the Spark Plugs have an R in the suffix    this is resistive and i feel corks up our feeble  HT of 22kv

on a modern this is overcome with a much higher HT 

here is a you tube of a guy doing some fairly basic tests to show how the spark voltage is reduced on a resistive plug 

so its love em or hate em choice is yours 

 

[dougbgt6]

So NO to resistive plugs then?

db

[1969Mk3Spitfire]

Point taken, Pete 😃

[Wagger]

My first means of transport (moped) had a magneto. Spark plug gap was 18 to 25 thou. The coli ignition scooter stated 25 to 30 thou. Until mid 1970's all my HT leads were metal with thick insulation. The screw-on suppressors had resistors of several meg-ohms in them. Then resistive leads were introduced instead of using suppressors, which many of us removed when we had mis-firing.

So, now we have resistive plugs as well. The mis match of parts is horrendous. I ran my race tuned bikes, with coil ignition, with spark gaps of 25 thou. It did not reduce top speed or acceleration.

If I get a sooty plug, I still resort to closing the gap to as little at 20 thou on coil ignition. It prolongs the sooting up period. My 30 year old Hayter mower is now set at 15 thou or it won't start. It's not had the plug out in three years.

[Badwolf]

I would like to see what 'elf and safety' would make of the assistant's 'protective clothing' in the workshop!!!

[Pete Lewis]

this is all down to preferences  our coils are not made to run resistive plugs , i have had many a local car with misfires and dumping the R plugs has worked out fine  

others use them with no apparent problem 

this guys simple test does suggest quite clearly   R gives you a reduced HT at the spark plug that cant be good 

for the miles most do in a season or two  using  high cost  plugs seems excessive for the mileages covered 

same logic as you dont spend £6k on an engine and only go to sainbury's  or park in the local field show 

Oils have the same problem most never get the life out of whats in the sump as they change it each year not every 3k 

and read the service  sheet and the filters are changed every other oil change  

theres a lot that can spend your money for little pay back and running a classic can be a wallet sucking hobby without making it worse 

sorry  dinosaur mode  while the suns out 

Pete

[Mjit]

I only ever use resistive spark plugs in my car...but then I've converted to MegaJolt so have to

[Pete Lewis]

and thats fine as the  HT would be very much higher than the std 

Pete

[1969Mk3Spitfire]

25 minutes ago, Badwolf said:

I would like to see what 'elf and safety' would make of the assistant's 'protective clothing' in the workshop!!!

I think I could be persuaded to train to become the elf and safety inspector for that investigation. 😁

[Badwolf]

2 minutes ago, 1969Mk3Spitfire said:

I think I could be persuaded to train to become the elf and safety inspector for that investigation. 😁

Get in the queue!!! 

[Pete Lewis]

1 minute ago, 1969Mk3Spitfire said:

I could be persuaded to train

Nah  there's  no trains    ..........strikes at work 

Pete

[Colin Lindsay]

I've the intention of trying a set of these Brisk plugs on the Herald shortly:

Brisk NR15S

https://briskracing.com/products/brisk-silver-racing-nr15s-spark-plug

They were highly recommended despite being resistive. Cost about £5 each.

[Pete Lewis]

the glazing problem seems to have caused lots of problems  

but bog std plugs have lasted us well over the past 50 years   now we run into all this 

it my   thought its poor running that soils the unglazed plug insulation , if its running clean there is no problems 

Pete

[Badwolf]

Makes me wonder. In one of the boxes of cast off spares, in the bottom with the muck and the spiders webs are old plugs going back to...well, who knows when. They were, as we all do, replaced as a matter of course at regular service times. In view of the quality of so many spares I am wondering, are these plugs, even in their current state better than some of the new stuff? Should I dig them out again, clean them up and give them a try. I know what the 'purists' here will say, but it makes you wonder?? 

[johny]

As Ive said before mine have been in at least since 92 and going fine  - ok not done loads of miles but saying that an electrode will probably shatter now!

[Pete Lewis]

with all my years of motoring i have always dumped old plugs  keep one just in case has never been needed 

.......Yet

doing 150 miles on sunday to Bressingham and return    i expect her to be trouble free

having some trigger finger problems this month so probably wont be able to let the stg wheel go !!!

never mind the plugs 

Pete