of course not, they are specifically made for the Renesis and the best plug for it IMO

 

Likely due to the 10 heat range......Although there doesn't seem to be an issue with water/meth or Methanol

 

I was only relaying information that my engine builder gave to me .... He has a lot of experience with rotary drag cars etc so I thought it worth mentioning.


I do remember MM talking about electrodes falling off and I may have been parroting that info , but don't know which specific plugs he was talking about .

Maybe iridium electrodes don't stick to the plug body as well as platinum ones do

 

R7420 & R7440 are iridium tip, platinum electrode
R6725 is platinum tip & electrode
BR10EIX is iridium tip, with a platinum disc welded to a ? electrode


Note that there are two different BR10EIX plugs
Part# 6957 is a solid end terminal nut and probably the preferred choice, called BR10EIX SOLID
Part# 6801 is a loose end terminal nut (threaded), called BR10EIX

 

interesting difference in end design between the R7440 and the R6725/R7420...

 

any insight as to why ?

 

I am currently going back and forth on the spark plugs, leaning towards the denso's because of cost and availability 26.79, and I like the 9, 10 heat range,

or the r6725's 10.5 and 11.5 but I think those will be too cool for my application.

 

No, I just happened to stumble across it in the NGK Racing catalog. The RX8 plug is much more open/exposed than the 13B plug, but it looks like the RX8 electrode is angled out to about the same OAL depth despite the shorter reach. I'd suspect that it lights off easier. That said, most of the more knowledgable people I have access to seem to prefer the R6725 over the R7440. Not sure if it's for cost or some other reason. There's plenty that I don't get told about.

 

1000 odd kms down the road . Just pulled these after a 200km road trip cruising at 3200 rpms most of the way .

left side is trailing 11.5s right side leading 10.5s Was expecting the trailings to be black but they look pretty good to my untrained eye .




And for reference ...... here are the recently replaced BUR9EQPs next to the new plugs

Trailings on right . Leadings on left

 

Not bad at all!!
How was mpg did you notice any AFR or ltft changes with the new plug?

I am running the 10.5 in trailing now.

 

MPG was worse if anything ... have not done a good test of that yet though.
Not noticed AFR changes but I did notice that idle vacuum seems to be a bit lower ..... could be a coincidence

 

Have you noticed any changes ?

 

big difference I think, my idle trims went from negative to positive about 10% swing
I run about .3 leaner up top now too seeing 11.1

could be plugs, but perhaps the summer gas, or 90 degree temps are contributing...

 

sitting here debating on adjusting the tune....

 

Just pulled the 10.5s again after 6000kms with a track day thrown in . In excellent condition ,very little carbon and look like they will last a lot longer .

MPG seems the same as before ... nothing negative to report.

 

thats fantastic news!! I should check mine sometime this winter

 

Great info! Was reading this and the rx7 post regarding the Autolite AR3932 plugs as I was interested in a lower cost alternative that is readily available locally. I found it interesting that a month after this thread was started the rx7 guy Howard posted that he was going away from the Autolites. Appears one of his plugs lost some ceramic in the motor after a detonation when he blew his fuel pump fuse while boosting at 25psi. A bit extreme circumstances, but thought it was worth mentioning. I still plan on trying them, as I don't plan on being in the 500rwhp realm. Of course, plans change now and then

FD Spark Plug Tech 2013 - Page 4 - RX7Club.com

 

Slash just change his spark plugs, he better update us!!!

 

LOL... I also posted in my thread. Update on the AR3932 plugs I installed back in January. I have been getting a few occasional misfires so I checked the plugs last night. They were pretty well worn so I replaced them. Much better They lasted 6 months running 10psi boost. Started out gapped at 0.025" and ended up worn to about 0.040". Not sure how many miles it has been, but unless there is bad weather this is my daily driver. At $3.99/ea I don't mind changing them a couple times a year.

Left to right = FL/FT/RL/RT

 

They look pretty well fouled as well . Def. would be replacing those way earlier than you did.

 

The savings from cheap sparkplugs will be long forgotten compared to the expense of a rebuild ... might as well get some cheap gas, some cheap oil, cheap coils, cheap sparkwires, etc. while you're at it.

 

Brettus I'll be checking them sooner this time around.

 

No concern that they erode so quickly?

 

Honestly when I ran BUR9EQP they eroded pretty quickly as well. Not quite as fast as these, but not far off...

 

Exactly my point ....