Manx Club

I run an aerospace grade CHT digital gauge under #3 sparkplug.



http://thesensorconnection.com/egt-prob ... -series-ws

I replaced the sparkplugs a few weeks ago and decided to try running a cooler plug.

I was running Bosch WR7AC which I think are equivalent to NGK BR6HS and now running NGK B5HS which is a cooler plug.

I'm now seeing a 100°F drop on my reading. I'm pretty sure the engine temperatures are very similar, the oil temp and pressure are consistent to what I was getting before. On ECVW I was seeing 410°F+ pretty much consistently and now I get sub 300°F with the odd 315°F on long climbs. I had to reset my mental 'redline' on that.

I knew the B5HS was a cooler plug but did not expect that big a drop on the reading.
Just sharing my observations.

NGK numbering system is opposite of Bosch.
A 5 series NGK is comparable to a 8 series Bosch plug which is a hotter plug than what you were using.
Since your Bosch number has a resistor and the NGK does not I don't know it that could make a differences it what the temp you are seeing.
Since Bosch only has resistor plugs now, I have been using NGK plugs for years since the change. I ran NGK in my race cars too.
I have always had good luck with them.

I have been running WR8AC Bosch since the upgrades to Kermit and have found my temps higher that's what I expected. I changed to B6HS NGK plugs tonight and after a ride, noticed better oil temps and smoother running. Tomorrow, we will run when it's warmer and see if the trend holds. Thanks for the heads up!