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From memory, the actual nub at the exterior end of the plug seemed smaller, so I was just as worried that the plug wire wouldn't fit as tightly as I was about the boot length. I guess I need to dig my set up, as I also have a loose set of plug wires at the moment.
@Howard Coleman Would you happen to have feedback on the 6601's in a 13B peripheral port naturally aspirated engine? I just took apart my peripheral port and found that with AR3932X's in the trailing and stock 9's in the leading, I had definitely had the SPM on both housings and warped all of my apex seals within 4000 miles. Could I run the 6601-11's without getting them machined? The housings are still useable (not cleaned off in this photo) but I'll be saving these for a project I don't care about as much and buying new housings.
a pretty easy read... both plugs were way too hot. the only NA experience i have is the six seasons i raced w Mazda. while we turbo guys deal w mountains of combustion chamber pressure i would think NA isn't in the same neighborhood. around 259 flywheel hp from a 12A. (this was with a Weber dual downdraft choked to 38 mm)
when Roger Mandeville delivered my car he gave me a large supply of surface gap sparkplugs. they were insanely expensive and i don't think they were even generally available. i received a lot of them and never had to buy any in the 6 years 72 races plus a bunch of Runoffs i ran.
they were really cold plugs! we had to use warm up plugs before the race and switched them in at the 5 minute bomb.
just looking very simply at your situation i would say you should be running 10.5 plugs top and bottom..
i prefer Denso over NGK but both are good. they are listed on my website.
@Howard Coleman Thanks for the feedback! While true that you have much more combustion pressure to deal with, wouldn't high RPM also contribute to increased temperatures with IGN1-A coils? The AR3932X were supposed to be equivalent to a 10 heat range but as you stated, that was clearly not enough. Maybe it's worth trying 10.5's and 11's?
Also, unfortunately for me, Denso S31A's are on national backorder with no ETA and 6601-11's are out of stock most places I've looked.
pretty sure those NGK R6061-11 plugs are all over ebay for cheap, but just making sure you know those don’t have a resistor
and assuming you weren’t referring to the NGK R6725-11 that does have a resistor, which unfortunately the source I posted up not too long ago appears to have sold out (Qty 4 for $45 shipped):
pretty sure those NGK R6061-11 plugs are all over ebay for cheap, but just making sure you know those don’t have a resistor
and assuming you weren’t referring to the NGK R6725-11 that does have a resistor, which unfortunately the source I posted up not too long ago appears to have sold out (Qty 4 for $45 shipped):
Good looking out! Actually, I was referring to the NGK 6601-11, not 6061-11. The 6061-11 you've referenced are completely different plugs then what Howard Coleman was discussing in this thread. Was that a typo?
a pretty easy read... both plugs were way too hot. the only NA experience i have is the six seasons i raced w Mazda. while we turbo guys deal w mountains of combustion chamber pressure i would think NA isn't in the same neighborhood. around 259 flywheel hp from a 12A. (this was with a Weber dual downdraft choked to 38 mm)
when Roger Mandeville delivered my car he gave me a large supply of surface gap sparkplugs. they were insanely expensive and i don't think they were even generally available. i received a lot of them and never had to buy any in the 6 years 72 races plus a bunch of Runoffs i ran.
they were really cold plugs! we had to use warm up plugs before the race and switched them in at the 5 minute bomb.
just looking very simply at your situation i would say you should be running 10.5 plugs top and bottom..
i prefer Denso over NGK but both are good. they are listed on my website.
Hey Howard, so what is the consensus on the best plut to use in the 500+WHP range? The Ngk 6601 or the Denso surface discharge plugs?
Howard really likes the Denso S31A, but they are now discontinued. We were able to find an Ebay seller that has a large lot remaining for sale. Granted they are old plugs, but I don't know that a plug has a shelf life if unused. I know Howard purchased a handful and I purchased 4 myself.
I know the NGK 6601-11 would work, but they have a 19mm reach instead of 21mm. This might be the best potential trailing surface gap plug we can get, especially for that heat range.
It seems like sparkplug.com has them for 6.58 a plug and it does not state that they are discontinued.
Originally Posted by iceman4357
We are bouncing a little between threads.
Howard really likes the Denso S31A, but they are now discontinued. We were able to find an Ebay seller that has a large lot remaining for sale. Granted they are old plugs, but I don't know that a plug has a shelf life if unused. I know Howard purchased a handful and I purchased 4 myself.
I know the NGK 6601-11 would work, but they have a 19mm reach instead of 21mm. This might be the best potential trailing surface gap plug we can get, especially for that heat range.
Shows them as "Notify when available." That website is also owned/ran by Denso. I called Denso and spoke directly with their top tech. He said that the S31A plugs have been on order since December of 2023! There are still outstand orders that need to be fulfilled since then, but have not. He said most distributors have cancelled orders as its been on backorder for so long. There is a small quantity they have in CA, but those will go to the existing orders when they are fulfilled. He didnt know when they would be processed, but only a few hundred plugs to multiple distributors.
He did a lot of digging and even called me back after a day and told me the bad news that this series of plug is being discontinued completely. Hence the reason Howard and I ordered from Ebay. IF we do see the S31a or even the S29a(lower heat range) pop up, we need to jump on them.
Shows them as "Notify when available." That website is also owned/ran by Denso. I called Denso and spoke directly with their top tech. He said that the S31A plugs have been on order since December of 2023! There are still outstand orders that need to be fulfilled since then, but have not. He said most distributors have cancelled orders as its been on backorder for so long. There is a small quantity they have in CA, but those will go to the existing orders when they are fulfilled. He didnt know when they would be processed, but only a few hundred plugs to multiple distributors.
He did a lot of digging and even called me back after a day and told me the bad news that this series of plug is being discontinued completely. Hence the reason Howard and I ordered from Ebay. IF we do see the S31a or even the S29a(lower heat range) pop up, we need to jump on them.
Eric
I'll be interested in your findings regarding the old-stock plugs, as I bought up a bunch of those too. Haven't had the guts to run them (or a need to run them) just yet.
Shows them as "Notify when available." That website is also owned/ran by Denso. I called Denso and spoke directly with their top tech. He said that the S31A plugs have been on order since December of 2023! There are still outstand orders that need to be fulfilled since then, but have not. He said most distributors have cancelled orders as its been on backorder for so long. There is a small quantity they have in CA, but those will go to the existing orders when they are fulfilled. He didnt know when they would be processed, but only a few hundred plugs to multiple distributors.
He did a lot of digging and even called me back after a day and told me the bad news that this series of plug is being discontinued completely. Hence the reason Howard and I ordered from Ebay. IF we do see the S31a or even the S29a(lower heat range) pop up, we need to jump on them.
Eric
I apologize, I definitely overlooked that. So NGK 6601-11(4586) plugs it is. I also found the 7420 plugs to not idle as well in the past. Im happy to know that we have other options to run and have a crispy feeling engine!
Looks like the NGK 6601-11's are out of stock most places now too. I purchased the last of the units available on NGK.com and the Ebay seller I found cancelled my order as they're also out of stock.
Received my Denso S29 and S31 plugs. Still sealed new in the boxes. Going to swap out all plugs and use the S29A and keep the S31A for my higher HP build.
Good looking out! Actually, I was referring to the NGK 6601-11, not 6061-11. The 6061-11 you've referenced are completely different plugs then what Howard Coleman was discussing in this thread. Was that a typo?
that was my bad, not recognizing the part number difference coupled with age, health, and resulting poor eye sight and failing comprehension, etc.
not a fan of where this is going, but not attempting to knock those pursuing it either.
What are the current options for 10.5s, other than the NGK competition plugs? Anything cheaper that doesn't require machining?
I think the only known option is the NGK R6725-105. I bought a set, but I am concerned with running a plug that has a ground strap. The last thing I want to do is melt or break a ground strap off and have it fall into my new engine.
The next best option for a 10 range seems to be R6601-10. At least that's a surface discharge plug that doesn't have a ground strap.
I think the only known option is the NGK R6725-105. I bought a set, but I am concerned with running a plug that has a ground strap. The last thing I want to do is melt or break a ground strap off and have it fall into my new engine.
The next best option for a 10 range seems to be R6601-10. At least that's a surface discharge plug that doesn't have a ground strap.
There are a lot of people running the NGK 5501(7420) for years and high HP applications without issues. If you are specifically talking trailing plugs and wanting no ground strap, I agree that the R6601-10 is probably ideal although reach isn't 21mm.
I still need to install my old(new) S29A plugs to see how they react.
There are a lot of people running the NGK 5501(7420) for years and high HP applications without issues. If you are specifically talking trailing plugs and wanting no ground strap, I agree that the R6601-10 is probably ideal although reach isn't 21mm.
I still need to install my old(new) S29A plugs to see how they react.
I really don't want a ground strap at all, due to the potential for failure (melted one when testing plugs on my last engine). If it's proven that R6725-105's in the leading position can survive without melting a ground strap, I'll run those and then put the R6601-11's in the trailing (my 9's all the way around were way too hot).
Anyone have any insight on these? NGK 7420-10, 13b-msp, IGN1A coils, timing has been advanced beyond stock, target AFR 13.11, these have 1 trackday and 6 autocrosses (my autox venue is high speed where I regularly hit top of 2nd in an rx8), roughly 2,500 miles on them. Premix at 1oz/gal for racing, omp output increased by 40%.
The car idles perfectly, no hot/cold start issues, no change from the stock heat range plugs which were 9/7
Left is trailing rear rotor, right is trailing front rotor Left is leading rear rotor, right is leading front rotor
the trail plugs ground strap looks like the length is fully annealed. if so, they are too hot. i would switch the top to 11. you are looking for half the strap to be annealed. i prefer a surface gap plug in the trail.
the trail plugs ground strap looks like the length is fully annealed. if so, they are too hot. i would switch the top to 11. you are looking for half the strap to be annealed. i prefer a surface gap plug in the trail.
the leads could be a half click colder.
Thank you, I figured the trailing might be running too hot. I also bought the 7420-11's with the set so I will try those and see how operation is before I decide to try the surface gap options. The shorter ceramic length of the surface gap options do concern me though with the boot potentially not pushing on all the way.
