spark plugs

[johnbirchjar]

Just received the latest edition of the club mag ,and an article inside mentioned spark plugs for air cooled & watercooled engines as C9E's,surely this should be C8E's ?J.B.

[Interpol2471]

C8E watercooled
C9E air cooled is general rule.
I used C9E and C8E in my air cooled depending on winter or summer but then I am very strange...

[kanonkopdrinker]

I have had a response to the article in the latest mag.

One member has expressed an interest in ten of the UG80PV plugs for his IP2.

Anyone else? Remember it’s a box of 100, so only another 90 to go!!!

David

[johnbirchjar]

I always used C8E's in the Classic(20years and 60 odd,000 miles )and ditto with the Commander engine in the old girl (never heard about C9E's )J.B.

[BlackIP2]

I thought I read somewhere that if you have used 'normal' plugs in the rotary, changing back to the surface discharge types might cause problems? The normal plugs apparently leave carbon in the recessed area that would not be there with a surface discharge plug fitted, and this gets scraped off as the surface discharge plugs gets screwed in?
I am not 100% certain of this but it did put me off as I was worried in case the carbon jammed the engine.
Anyone else shed any light on this or am I totally wrong? Happy to be corrected if so!
Mark

[Interpol2471]

It would have to be a high mileage engine on ngk to have sufficient carbon built up to worry about.
The air cooled engine I have just stripped had high carbon build up on the rotors but the plug threads were clear.

[GeoffD]

Just checked my air cooled. It's fitted with C9ES, should I change them?

[GeoffD]

Oops, that should have read C8ES.

[BlackIP2]

Can anyone tell me why we can't use these surface discharge plugs that seem readily available and amazingly cheap:
https://www.ebay.co.uk/itm/Champion-sur ... SwzgRWu2Mg
Is it the size or heat rating that counts them out for Norton rotaries?
The ebay seller is RGM who do Norton big twin spares.

[johnbirchjar]

The reason that I never continued using the Discharge Plugs was that way back in the late '80's& early '90's they were very expensive (compared with the"Normal" GKN's)and I for one could see no difference in performance,economy or starting from hot or cold ,perhaps Richard could explain why Norton chose them in the first place?(and if memory serves, Shenstone fitted GKN C8E's on my first factory re-build way back in 1999 ) J.B.

[Zed]

The reason for the surface discharge plug was an attempt to reduce what in Jan Norby's book is called 'breathing volume'. The bane of peripherally configured rotary engines is tip leakage and over the years many attempt have been made to reduce this. This volume is small compared to a peripheral inlet or exhaust port hence why change between surface discharge and conventional my go unnoticed. Also a suspect the conventional may have a stronger spark at the same rating.

Getting the spark deeper into the chamber was always the holy grail and laser ignition was supposed to offer this, but it would never work for a rotary as oil on the wall would mean the optics could not be self-cleaning. Mazda was pursuing compression ignition, but rotaries are not very good at high compression. I think Mazda may have solved this but it did not make financial sense to commercialise it. There are other options and I can see how Brian Crighton made a Euro 4 rotary.

Zed

[johnbirchjar]

Your Ref: to"Euro 4", is that the "Emissions" Reg:?(the bane of all rotories )J.B.

[Zed]

Yeap. It involves minimising or eliminating the 2 stroke oil, reshaping the chamber, going lean, etc. or the direction Garside went in moving away from the Otto cycle.