How do you choose spark plug heat range?
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Joined: Nov 2011
Posts: 80
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From: Indonesia
Hi,
I'm David from Indonesia. I'm planning to build an engine conversion of an old skool Mazda 808 sedan with 13BT REW engine. I'm planning to use the car for street driven and hard driving occasionally. My target power is 350rwhp over if possible. My set up is as follow;
Lead Coil for stock ignition
Magnacores Wires for stock ignition
Greddy Elbow w/ flange
Greddy Type RS BOV
Denso Fuel Pump
Lightweight Main Pulley
Water Pump/ Alt Pulley Kit
Power Steering Pulley
Rebuilt Starter
Greddy Boost Controller
PS/AC Belt
Street Ported Rotor Housings ( Ceramic Coated )
Water Jacket Mods
Install Rotor Bearings
FD OH Rebuilt Kit ( 1011# )
HKS Twin Ignition
Used Apexi Intake with glass beading and filter service
Coolant sensor
Used Apexi Power FC Gen 3 with New commander Gen 4
PWR Intercooler
PWR Radiator
PWR Oil Cooler
PWR Fan 385mm
Greddy T78-33D Turbocharger
4 X 850cc Sard Fuel Injectors ( RHD Japan )
Sard Fuel Regulator + Adaptor
Oil Catch Tank
Rice Racing Water Injection Kit
RF300 exhaust ( Exhaust Technology )
Mid Resonator ( Exhaust Technology )
Complete OEM Apexi Seals
Could you suggest to me which kinds of spark plugs suitable for my set up ? Your advice is highly appreciated. Thanks a lot.
David L
I'm David from Indonesia. I'm planning to build an engine conversion of an old skool Mazda 808 sedan with 13BT REW engine. I'm planning to use the car for street driven and hard driving occasionally. My target power is 350rwhp over if possible. My set up is as follow;
Lead Coil for stock ignition
Magnacores Wires for stock ignition
Greddy Elbow w/ flange
Greddy Type RS BOV
Denso Fuel Pump
Lightweight Main Pulley
Water Pump/ Alt Pulley Kit
Power Steering Pulley
Rebuilt Starter
Greddy Boost Controller
PS/AC Belt
Street Ported Rotor Housings ( Ceramic Coated )
Water Jacket Mods
Install Rotor Bearings
FD OH Rebuilt Kit ( 1011# )
HKS Twin Ignition
Used Apexi Intake with glass beading and filter service
Coolant sensor
Used Apexi Power FC Gen 3 with New commander Gen 4
PWR Intercooler
PWR Radiator
PWR Oil Cooler
PWR Fan 385mm
Greddy T78-33D Turbocharger
4 X 850cc Sard Fuel Injectors ( RHD Japan )
Sard Fuel Regulator + Adaptor
Oil Catch Tank
Rice Racing Water Injection Kit
RF300 exhaust ( Exhaust Technology )
Mid Resonator ( Exhaust Technology )
Complete OEM Apexi Seals
Could you suggest to me which kinds of spark plugs suitable for my set up ? Your advice is highly appreciated. Thanks a lot.
David L
Here's my experience with the BUR9EQ, BUR9EQP, NGK R6725, and NGK BR10EIX
BUR9EQ: cheapest. Confirmed safe up into low 400s, at least with the way I tune cars. Least expensive. Doesn't last very long--definitely 5000 miles or less if you are using an ignition amplifier.
BUR9EQP: close in price to BUR9EQ. Confirmed safe up into low 400s, at least with the way I tune cars. Lasts longer than BUR9EQ.
Both of these are a little more resistant to fouling due to slots and surface discharge design.
BR10EIX: cheap 10 heat range with irridium. Pain in the *** because they require an expensive thin wall socket. If you make a DIY one with a grinder, you are risking something going wrong. These are lacking in durability in my experience; I cracked the porcelain on a couple sets. I've found a BUR9EQ will hold up better than one of these.
NGK R6725 10.5: very expensive but work with a conventional socket. They definitely hold up longer than the other plugs.
Both of these sets of plugs have noticeable loss in idle quality and low load driving. I have done back-to-back swaps with these running the exact same tune, and had to add significant fuel to get AFR's from being too lean. Basically, brake specific fuel consumption increases in around-town driving. If you do foul them, you're probably out a lot of money.
I think people underestimate just how cold the stock heat range plugs are. I mean that is REALLY cold plug. There are a lot of piston engines with very high exhaust temperatures making a lot of power with a combustion chamber pressure that only run 7's or 8's.
BUR9EQ: cheapest. Confirmed safe up into low 400s, at least with the way I tune cars. Least expensive. Doesn't last very long--definitely 5000 miles or less if you are using an ignition amplifier.
BUR9EQP: close in price to BUR9EQ. Confirmed safe up into low 400s, at least with the way I tune cars. Lasts longer than BUR9EQ.
Both of these are a little more resistant to fouling due to slots and surface discharge design.
BR10EIX: cheap 10 heat range with irridium. Pain in the *** because they require an expensive thin wall socket. If you make a DIY one with a grinder, you are risking something going wrong. These are lacking in durability in my experience; I cracked the porcelain on a couple sets. I've found a BUR9EQ will hold up better than one of these.
NGK R6725 10.5: very expensive but work with a conventional socket. They definitely hold up longer than the other plugs.
Both of these sets of plugs have noticeable loss in idle quality and low load driving. I have done back-to-back swaps with these running the exact same tune, and had to add significant fuel to get AFR's from being too lean. Basically, brake specific fuel consumption increases in around-town driving. If you do foul them, you're probably out a lot of money.
I think people underestimate just how cold the stock heat range plugs are. I mean that is REALLY cold plug. There are a lot of piston engines with very high exhaust temperatures making a lot of power with a combustion chamber pressure that only run 7's or 8's.
Rotary Enthusiast
Joined: Aug 2006
Posts: 1,216
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From: Melbourne FL/San Antonio TX/Okinawa Japan
I was going through a box of old spark plugs and found some NGK 6701's.
Looked them up on sparkplugs.com and they are for RX8. 19mm reach. I do remember collecting a few of them when I worked for Mazda a few years ago.
Any one know if the rotor housing on the RX8 is thinner the the rx7's?
Also noticed there are Denso 21mm reach plugs for the RX8.
Looked them up on sparkplugs.com and they are for RX8. 19mm reach. I do remember collecting a few of them when I worked for Mazda a few years ago.
Any one know if the rotor housing on the RX8 is thinner the the rx7's?
Also noticed there are Denso 21mm reach plugs for the RX8.
Joined: Mar 2001
Posts: 31,830
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From: https://www2.mazda.com/en/100th/
I was going through a box of old spark plugs and found some NGK 6701's.
Looked them up on sparkplugs.com and they are for RX8. 19mm reach. I do remember collecting a few of them when I worked for Mazda a few years ago.
Any one know if the rotor housing on the RX8 is thinner the the rx7's?
Also noticed there are Denso 21mm reach plugs for the RX8.
Looked them up on sparkplugs.com and they are for RX8. 19mm reach. I do remember collecting a few of them when I worked for Mazda a few years ago.
Any one know if the rotor housing on the RX8 is thinner the the rx7's?
Also noticed there are Denso 21mm reach plugs for the RX8.
the trailings are longer, and people use them, but i don't see how it seals, maybe with a couple extra washers or something.
Rotary Enthusiast
Joined: Aug 2006
Posts: 1,216
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From: Melbourne FL/San Antonio TX/Okinawa Japan
At 9/10 psi, think at 7500rpms it made 280 in third gear on a mustang dyno, pump gas. Running the V-power heat range 11 plugs gaped at .020. No issues. Not sure if this is a indication about noise in the ignition system but it is some thing.
Tearbo2 tuned. Car sounded GREAT!
Honestly think the gap of the plug plays the biggest part in having a reliable ignition setup. The most often over looked thing.
Joined: Mar 2001
Posts: 31,830
Likes: 3,232
From: https://www2.mazda.com/en/100th/
Rotary Enthusiast
Joined: Aug 2006
Posts: 1,216
Likes: 10
From: Melbourne FL/San Antonio TX/Okinawa Japan
Do you mean shorter plugs are bad for high boost or is there another reason for your comment?
Joined: Mar 2001
Posts: 31,830
Likes: 3,232
From: https://www2.mazda.com/en/100th/
I'm kinda confused with your comment about short plugs are bad. If the RX8 plugs are 19mm reach and the housing are the exact same as the older models, How is that bad? Is mazda wrong?
Do you mean shorter plugs are bad for high boost or is there another reason for your comment?
Do you mean shorter plugs are bad for high boost or is there another reason for your comment?
if the Rx8 plug is shorter, then the spark plug is further away from the combustion chamber which is bad.
if its longer then installing it is either bending something, or the sealing ring isn't sealing.
the point is the trailing plug is different.
also the Rx8 plugs appear to be the same as the racing plugs, just in a 6,7,8 and 9 heat range
Rotary Enthusiast
Joined: Aug 2006
Posts: 1,216
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From: Melbourne FL/San Antonio TX/Okinawa Japan
Want to stress, I am not advocating the use of shorter plugs or non-resister ones but do have another car story.
FD, FFE hall sensor trigger, LSx coils, V-power 3$ plugs gaped at .020, Haltech P1000, stock trans and rear end.
Just testing last night at the track went 132mph. Was going to try and launch the car on the next pass for a good ET pass but clutch let go. It sounds like the splines on the disc stripped out when he launched the car.
FD, FFE hall sensor trigger, LSx coils, V-power 3$ plugs gaped at .020, Haltech P1000, stock trans and rear end.
Just testing last night at the track went 132mph. Was going to try and launch the car on the next pass for a good ET pass but clutch let go. It sounds like the splines on the disc stripped out when he launched the car.
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Joined: Feb 2013
Posts: 1
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From: Canada
I am just wondering i have a street ported fresh rebuilt 13b and was running bur7eqp and bur9eqp it died while i was driving. i test fuel pump its good i tested spark and there is spark. i think the plugs got fuel fouled. would it be alright to run bur9eq all around? or do i need the 7? its a single turbo conversion with 850cc injectors and all the good stuff so its far from stock.
NGK R7420 Heat ranges 10 and 10.5... Going to run Adaptronic Plug and play engine management, AEM 50/50 Water/Meth injection, gtx3582R.....goal is 430-480 WHP. Still will never get over spending $150 on spark plugs...haha
Because the R7420 range is very hard to get in aus.
I have been using the R6725-115 in both street and race cars. As long as the tunes are good they don't foul and are actually very reliable.
I have been using the R6725-115 in both street and race cars. As long as the tunes are good they don't foul and are actually very reliable.
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Joined: Oct 2007
Posts: 799
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From: Plymouth, MN
What do you recommend for my setup?
13B-RE Big Streetport
21-25psi (480-580whp)
LS-2 Coils (thinking of switching to AEM smart coils)
Running on E-85
Currently I'm using BR9EIX plugs for both Trailing and Leading. Reason I'm a little hotter is that it helps with the E-85. What would you guys recommend for E-85 that last longer than the BREIX plugs?
Thanks.
C
13B-RE Big Streetport
21-25psi (480-580whp)
LS-2 Coils (thinking of switching to AEM smart coils)
Running on E-85
Currently I'm using BR9EIX plugs for both Trailing and Leading. Reason I'm a little hotter is that it helps with the E-85. What would you guys recommend for E-85 that last longer than the BREIX plugs?
Thanks.
C
Anyone running 6725-9's? I know its been said that bur9eq's are good up to about 400whp maybe a bit more with water injection, is it safe to assume that 6725's would handle similar power safely in the 9 heat range? I see that they are only 19.99 on sparkplugs.com and was thinking about trying a set in hopes of longer life, the bur9eq's ive been running have been wearing down the center electrode very quickly.
Joined: Oct 2001
Posts: 6,279
Likes: 728
From: Florence, Alabama
"I have been using the R6725-115 in both street and race cars."
no question the 6725s are great plugs when used w a CDI system.
i never had a plug related problem w this setup.
my interest relates to the 6725 plugs directed inductively using (only) the Mercury Marine/IGN-1A/AEM coils above 500 hp. (no CD)
howard
no question the 6725s are great plugs when used w a CDI system.
i never had a plug related problem w this setup.
my interest relates to the 6725 plugs directed inductively using (only) the Mercury Marine/IGN-1A/AEM coils above 500 hp. (no CD)
howard
"I have been using the R6725-115 in both street and race cars."
no question the 6725s are great plugs when used w a CDI system.
i never had a plug related problem w this setup.
my interest relates to the 6725 plugs directed inductively using (only) the Mercury Marine/IGN-1A/AEM coils above 500 hp. (no CD)
howard
no question the 6725s are great plugs when used w a CDI system.
i never had a plug related problem w this setup.
my interest relates to the 6725 plugs directed inductively using (only) the Mercury Marine/IGN-1A/AEM coils above 500 hp. (no CD)
howard
Been doing it for several seasons. No issues. You're chasing a phantom.
Rotary Enthusiast
Joined: Aug 2006
Posts: 1,216
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From: Melbourne FL/San Antonio TX/Okinawa Japan
V-power #6569 with around 25 test passes. 2 to 3 oz of premix per gallon. Never a problem. around 600+rwhp at 11000+rpms E70 fuel
Looks like these are the plugs for me. Even though there the 19mm reach ones.
Joined: Oct 2001
Posts: 6,279
Likes: 728
From: Florence, Alabama
"V-power #6569 with around 25 test passes."
CDI or inductive?
i note they have a large grounding strap.
i am on the dyno currently w the AR3932X plugs so we will see how they work. if you read my thread re fine wire plugs and inductive i do not have a conclusion regarding them... "possible" mismatch. i am posing the question.
further, perhaps the 6725s are just ducky w big inductives... if the AR3932X plugs work, and i suspect they will
i can buy 25 of them for one set of 6725s... i really like the much larger grounding strap(s) mass w inductive.
we will see.
howard
CDI or inductive?
i note they have a large grounding strap.
i am on the dyno currently w the AR3932X plugs so we will see how they work. if you read my thread re fine wire plugs and inductive i do not have a conclusion regarding them... "possible" mismatch. i am posing the question.
further, perhaps the 6725s are just ducky w big inductives... if the AR3932X plugs work, and i suspect they will
i can buy 25 of them for one set of 6725s... i really like the much larger grounding strap(s) mass w inductive.
we will see.
howard
Rotary Enthusiast
Joined: Aug 2006
Posts: 1,216
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From: Melbourne FL/San Antonio TX/Okinawa Japan
Did read you other thread on the autolite plugs.
One thing I find very interesting is, In another thread I brought up using a 19mm reach plug that was non-resistor and a few guys told me this type of plug causes issues. But when you mention using this type of plug no one says anything negative.
current setup is stock FC igniters and coils and not sure if the gap of the autolite plug is to large to fire with the current setup. But am in the process of testing them.
One thing I find very interesting is, In another thread I brought up using a 19mm reach plug that was non-resistor and a few guys told me this type of plug causes issues. But when you mention using this type of plug no one says anything negative.
current setup is stock FC igniters and coils and not sure if the gap of the autolite plug is to large to fire with the current setup. But am in the process of testing them.
