Spark Plugs

[GJ1]

I am currently on NGK BPR6ES plugs and considering putting new ones in as per the manual. However, when I looked at the servicing being done by SJS, it appears they use BPR7ES plugs.

What is the difference in the two versions?

Am I correct in thinking that the Gap on the ***6ES is 0.9mm and on the ***7ES it would be 0.8mm?

What is the general opinion of the forum on which to use?

Just a little confused at present

[amarshall]

6/7 etc are the heat rating numbers on NGK

Everything you ever needed to know about NGK plug codes : http://www.spark-plugs.co.uk/pages/tech ... l_code.htm

[mds666]

as standard all "base" cars (82-92) are fitted with BPR6ES and all "SE" (86-92) cars are fitted with BPR7ES. as stated before the sevens are "hotter" than the sixes, 6's will generall start better

[Simpatico]

My LC engine definitely runs/starts better since replacing the 7s with proper 6s last month

[GJ1]

Thanks for the info chaps

So from what I can gather then is that although I have a HC SE which probably left the factory with ***7s but is now fitted with ***6s, I am better of by sticking to the 6s as they are better for starting?

P.S. The car has always ran well on the 6s and even better after a clean up once in a while. So I suppose I should stick with them. Or...........

do i give the 7s a go decisions, decisions.

Oh well, at least I should count myself lucky that thats all I have concerns about at the moment with the Old Girl

[Redexcel]

The numbers 6 and 7 give an indication of the operational heat range of the plug. The 6 has inferior cooling to the 7 and can therefore only operate in a (relatively) cool environment such as found in the combustion chamber of the LC 160 BHP model. Lotus obviously felt the 7 was more suitable for the higher combustion temperatures of the 180 BHP HC engine.
I doubt if it really matters unless you drive your car hard all the time, but obviously Lotus had to take that possibility into account when engineering the HC engine.
There should be no difference in starting from cold with between the two assuming they are in similar condition and correctly gapped.