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FWIW, i have been running the modded 6601s but haven't been able to really test them as i have a slightly occluded rear primary injector. i will take a quick trip to see one of my fav people, Bob Banner, at Fuel Injector Connection and have them cleaned. as far as just driving, they seem to work no diff than the (6601) stockers.
Last edited by Howard Coleman; Aug 14, 2023 at 01:42 PM.
no drama ATM. i have a few hundred miles on them, almost all 3rd gear pulls, and all is well my motor has been gaining compression. i am prepping for a dyno session in Pennsylvania which will provide lots more stress and key data.
since we are at post 131 i offer a quick refresher as to why you should consider running a non traditional plug in the trail/top position especially w a single turbo setup:
perhaps the best reason is because MAZDA did. why did the FD come w the weird plugs?
Mazda did not want to cause pre-ignition and detonation due to the conventional ground strap acting like a glow plug. the four large grounding platforms exist so as to avoid pre-ignition. the have too much mass to overheat.
the TRAIL plug is actually the FIRST plug to be exposed to the new face of the rotor that contains a combustible mix. since it positions earlier (than the lead plug) the mixture is less compressed and therefore is much more easily ignited. if the mixture ignites early (pre-ignition), it causes huge mechanical stress as the expansion is countered by the decreasing volume as the rotor heads toward top dead center. a collapsed rotor face and detonation often follow.
according to Richard Green (Green Brothers, New Zealand):
"With any decent inductive ignition you need to run a full surface discharge plug in the trailing. If you don’t, you will get knock over approx 500hp."
many of us have no interest in 500 hp but Richard is talking about an optimized setup. a tank of semi bad gas and the exact dynamics appear at 400 hp.
when we convert to single turbo we generally add a colder plug. since NGK doesn't make a colder copy of the weird looking OE plug we swap into a plug w a thin single ground strap. the single thin strap can act as a glow plug and especially in the top position can pre-ignite the mixture which can cause great harm to our motors.
an excellent trail plug option exists, the NGK R6601. a surface gap (no ground strap) plug available in a number of heat ranges and containing a resistor... made by NGK.
a forum member has been running them in all 4 positions on his motor for years. he reports decreased knock readings. another member also reports 15% lower knock readings running the plugs in all four positions. i ran the non modded plugs in all four positions for a couple of months. they were 11 heat range. based on my experience i recommend 10 heat range in the lead and 11 in the trail.
i did swap in all four of the modded R6601s. 20 to 30 third gear pulls around mid 500. no drama. i wasn't able to draw any conclusions as to a performance difference but if i had the option to place the spark closer to the action i would happily pay the price. i recently was on a dyno making 575 SAE. i elected to run traditional (Denso 11) plugs in the lead/lower and the modded R6601s in the trail/top. no knock. here are the plugs after pull number 10.
.
Last edited by Howard Coleman; Jan 1, 2024 at 10:50 AM.
no drama ATM. i have a few hundred miles on them, almost all 3rd gear pulls, and all is well my motor has been gaining compression. i am prepping for a dyno session in Pennsylvania which will provide lots more stress and key data.
Do you know how much more compression you have gained with the modded r6601s placed in the trailing and leading positions vs other traditional plugs.
Lets see what Howard Coleman says. Logically moving a surface discharge plug closer to the edge of the housing should decrease the blow by when the apex seal crosses it. Thus increase compression. It'd be nice to know what those number difference are.
If you're referring to this quote, you might be taking Howard's comment out of context:
Originally Posted by Howard Coleman
no drama ATM. i have a few hundred miles on them, almost all 3rd gear pulls, and all is well my motor has been gaining compression. i am prepping for a dyno session in Pennsylvania which will provide lots more stress and key data.
IIRC, this was a new engine that Howard built, and he was probably referring to the motor gaining compression following the accumulation of some break-in time & miles.
"a new engine that Howard built, and he was probably referring to the motor gaining compression following the accumulation of some break-in time & miles."
yes, of course unrelated to the plugs.
BTW, for those interested, i note what i think is a relatively new website for I-Seals. i enjoyed reading about their developmental history.
If you're referring to this quote, you might be taking Howard's comment out of context:
IIRC, this was a new engine that Howard built, and he was probably referring to the motor gaining compression following the accumulation of some break-in time & miles.
Lets see what Howard Coleman says. Logically moving a surface discharge plug closer to the edge of the housing should decrease the blow by when the apex seal crosses it. Thus increase compression. It'd be nice to know what those number difference are.
plug is going to make very little difference to the blow down across the holes, they are too far back.
it’s the same website for quite a few years. I’d have to go back to when I bought one of the first sets of the new steel apex seals from Mazmart. Seems like it was 2017 maybe.
Or at least I didn’t notice anything new. I usually check maybe twice a year.
.
since we are at post 131 i offer a quick refresher as to why you should consider running a non traditional plug in the trail/top position especially w a single turbo setup:
perhaps the best reason is because MAZDA did. why did the FD come w the weird plugs?
Mazda did not want to cause pre-ignition and detonation due to the conventional ground strap acting like a glow plug. the four large grounding platforms exist so as to avoid pre-ignition. the have too much mass to overheat.
the TRAIL plug is actually the FIRST plug to be exposed to the new face of the rotor that contains a combustible mix. since it positions earlier (than the lead plug) the mixture is less compressed and therefore is much more easily ignited. if the mixture ignites early (pre-ignition), it causes huge mechanical stress as the expansion is countered by the decreasing volume as the rotor heads toward top dead center. a collapsed rotor face and detonation often follow.
according to Richard Green (Green Brothers, New Zealand):
"With any decent inductive ignition you need to run a full surface discharge plug in the trailing. If you don’t, you will get knock over approx 500hp."
many of us have no interest in 500 hp but Richard is talking about an optimized setup. a tank of semi bad gas and the exact dynamics appear at 400 hp.
when we convert to single turbo we generally add a colder plug. since NGK doesn't make a colder copy of the weird looking OE plug we swap into a plug w a thin single ground strap. the single thin strap can act as a glow plug and especially in the top position can pre-ignite the mixture which can cause great harm to our motors.
an excellent trail plug option exists, the NGK R6601. a surface gap (no ground strap) plug available in a number of heat ranges and containing a resistor... made by NGK.
a forum member has been running them in all 4 positions on his motor for years. he reports decreased knock readings. another member also reports 15% lower knock readings running the plugs in all four positions. i ran the non modded plugs in all four positions for a couple of months. they were 11 heat range. based on my experience i recommend 10 heat range in the lead and 11 in the trail.
i did swap in all four of the modded R6601s. 20 to 30 third gear pulls around mid 500. no drama. i wasn't able to draw any conclusions as to a performance difference but if i had the option to place the spark closer to the action i would happily pay the price. i recently was on a dyno making 575 SAE. i elected to run traditional (Denso 11) plugs in the lead/lower and the modded R6601s in the trail/top. no knock. here are the plugs after pull number 10.
.
Got any pics of the modified R6601s inside a housing?
Howard and the rest of the club members,
My big question is, is it worth producing the modded plugs to sell to the members? For those you didn't read the rest of this thread, I had 8 plugs modded by an expert machine shop that does work for NASA, etc. here in the Huntsville, AL area. I sent 4 to Howard for testing. The shop is able to do these in bulk if the demand is there. I would then sell them myself for a small mark-up or get one or more of the RX7 vendors or shops to sell them for me. If there is enough demand, I would be happy to do this. If not, I will just use the modded plugs on my own car. I would do heat ranges from 9 to 11, if I were to sell them. Howard, what do you think? Other members?
Mike
I grabbed a couple of these a while back with another plug order. It's not just the length of the threads, the whole plug looks like a lawnmower plug or something. The portion that would mate to the plug wire is smaller. Any concerns with making a good connection there without custom wires?
I could cut the lock washer off and use the thin copper ones somebody posted about, but the rest of it concerned me too.
I grabbed a couple of these a while back with another plug order. It's not just the length of the threads, the whole plug looks like a lawnmower plug or something. The portion that would mate to the plug wire is smaller. Any concerns with making a good connection there without custom wires?
I could cut the lock washer off and use the thin copper ones somebody posted about, but the rest of it concerned me too.
I had the same concerns with the smaller form factor. I do not know what if any drawbacks there are here aside from the obvious possible boot/terminal fitment issues.
I grabbed a couple of these a while back with another plug order. It's not just the length of the threads, the whole plug looks like a lawnmower plug or something. The portion that would mate to the plug wire is smaller. Any concerns with making a good connection there without custom wires?
I could cut the lock washer off and use the thin copper ones somebody posted about, but the rest of it concerned me too.
Did you take any measurements of these plugs to compare with those on the usual OEM NGK's? I'd like to see how the metal terminal (diameter & length) and the insulator (again diameter & length) compares with the OEM NGKs. I'd assume there should be little to no difference in the metal terminals since spark plug wire terminals tend to be standard across the board, but the fit of the insulator to spark plug wire insulator boots might differ.
I grabbed a couple of these a while back with another plug order. It's not just the length of the threads, the whole plug looks like a lawnmower plug or something. The portion that would mate to the plug wire is smaller. Any concerns with making a good connection there without custom wires?
I could cut the lock washer off and use the thin copper ones somebody posted about, but the rest of it concerned me too.
The reason the machined plugs are better in my opinion is that the machine shop retains the stock washer or ring for a better seal and much less hassle. You can remove and replace the plugs without worrying about the loose washer, etc. Also, you don't have to buy washers and stock them too.
The small overall plug size is concerning for wire fitment, but Howard stated earlier he didn't have problem with it. Maybe it is the plug wires he is using. My car is currently down, waiting for me to install a new engine, that has been under my lift for a while now, so I haven't personally tried the modded plugs, just Howard. Mike
Did you take any measurements of these plugs to compare with those on the usual OEM NGK's? I'd like to see how the metal terminal (diameter & length) and the insulator (again diameter & length) compares with the OEM NGKs. I'd assume there should be little to no difference in the metal terminals since spark plug wire terminals tend to be standard across the board, but the fit of the insulator to spark plug wire insulator boots might differ.
The unthreaded metal cylinder is shorter than the stock plugs. The ceramic portion again much smaller, as stated. The electrode also smaller, as stated. The machine shop takes off 2 mm of the metal cylinder, above the threaded portion, to make the reach the same as stock plugs. Howard had pictures and measurements of many plugs earlier in the thread. Also, of the modded plugs I sent him.
I can post a picture too.
Mike
Last edited by mikejokich; Jan 21, 2024 at 11:58 AM.
Here are several pictures. One is Howard's and some are mine from earlier in the thread to compare the plugs.
My thoughts on the R6601's is the smaller ceramic portion is likely related to the overall much smaller metallic portion of the plug. Less of a heat sink requiring less of a ceramic insulator? Any thoughts?
Mike
Howard's earlier picture. Stock plug. Stock plug. R6601 unmodified. R6601 unmodified. My modified R6601 My modified R6601 My modified R660. Measurement of the collar. Cut from 4 mm down to approx. 2 mm.
they’re a lot shorter on the external end the spark wire boot attached too, pretty sure this is what is being referred to
but there are pictures posted in this thread comparing them next to regular NGK rotary plugs that they should go take a look at
I know people who used them as-is, they said the spark boot fitment was ok, but barely cleared the housing due to the short ceramic. That was on a Renesis housing so possibly could be some variation to the older 13B housings. A longer boot end might need to be trimmed.
Which the modification to get the threaded end positioned correctly is making the external end shorter still. I go back to what Lance Nist stated though, that with the IGN-1A coil the spark boot should fully extend the full length of the ceramic to touch the metal grounding end.
and honestly, the “anything over 500 whp” claim goes against the proven history of many racing engines and pro builder recommendations, but just my perspective
to be sure, if too hot of a plug is used for extended WOT then the grounding strap on the standard rotary race plug is going to burn off …
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