spark plugs
- Thread starter st185rc
- Start date
First post for a while on here and I am already pointing out shit.
Electrodes on spark plugs are made as thin as possible because it is easier for an electron to leap away from a thinner surface than a thicker surface. A precious metal electrode is thinner than a copper electrode because it can handle the heat of combustion in a thinner state. This allows you to run a larger gap which generally helps if you have an idle problem. It does not give you a bigger spark as the spark energy is determined by the coil. If you have made no modifications to your engine you want to run the plug type and gap recommended by the manufacturer. If the manufacturer recommend a precious metal plug and you use a copper plug you will need to tighten the gap.
The only reason you want to go to a colder running plug is because you are seeing signs of the plug overheating. This can be seen as 'chalking' around the electrode.
Roger
Electrodes on spark plugs are made as thin as possible because it is easier for an electron to leap away from a thinner surface than a thicker surface. A precious metal electrode is thinner than a copper electrode because it can handle the heat of combustion in a thinner state. This allows you to run a larger gap which generally helps if you have an idle problem. It does not give you a bigger spark as the spark energy is determined by the coil. If you have made no modifications to your engine you want to run the plug type and gap recommended by the manufacturer. If the manufacturer recommend a precious metal plug and you use a copper plug you will need to tighten the gap.
The only reason you want to go to a colder running plug is because you are seeing signs of the plug overheating. This can be seen as 'chalking' around the electrode.
Roger
I've noticed that the NGK has wires for the 90-91 and 92-32 ST185s.
Whats the difference?
Looking in the service manual for a 90 alltrac.
Recommended Gap .8mm or .31"
According to NGK site, their "oem replacement" plugs for the 90 celica alltrac come in .32"
Also, NGK shows that the BKR6EP-8 Double Platinum plug is the OEM standard replacement for our cars. the '90 service manual supports this -
"Recommend Spark Plug: ND PK20R8 or NGK BKR6EP-8"
It also states that plugs should be replaced every 100k km. which is a hell of a lot more than 2-3 oil changes. but i guess that is with their recommended platinum plugs
Thanks
Corey
Whats the difference?
Looking in the service manual for a 90 alltrac.
Recommended Gap .8mm or .31"
According to NGK site, their "oem replacement" plugs for the 90 celica alltrac come in .32"
Also, NGK shows that the BKR6EP-8 Double Platinum plug is the OEM standard replacement for our cars. the '90 service manual supports this -
"Recommend Spark Plug: ND PK20R8 or NGK BKR6EP-8"
It also states that plugs should be replaced every 100k km. which is a hell of a lot more than 2-3 oil changes. but i guess that is with their recommended platinum plugs
Thanks
Corey
Someone posted up a short guide ages ago with boost level to show which range to get and always gap them at 0.31" or whatever is stock. I think it was something like- you want to use stock up to 14psi, go a step colder up to 22psi and something special over that.
I have NGK 7's at the moment on 13psi and I am pretty sure they are causing some hesitation down low especially when cold but I am waiting on new ignition leads to make sure. I will swap 6's back in to see what happens. I imagine since most people who run low to moderate boost still spend almost all their time off boost anyway 6's would be the way to go.
Are there any merits to going 0.28 instead of 0.31?
I have NGK 7's at the moment on 13psi and I am pretty sure they are causing some hesitation down low especially when cold but I am waiting on new ignition leads to make sure. I will swap 6's back in to see what happens. I imagine since most people who run low to moderate boost still spend almost all their time off boost anyway 6's would be the way to go.
Are there any merits to going 0.28 instead of 0.31?
tw2":xl14zysi said:
This shows a miss understanding of how the plug works. The spark energy remains the same as the coil remains the same. A hotter plug will not 'boost the spark'. The plug heat range is a measure of the plugs ability to move heat energy away from the electrode. A hotter plug will have a hotter electrode. The electrode must be above a given temperature to burn the combustion deposit off so not to foul.
You only need to go down in plug temperature if the eletrode shows signs of over heating. This is influanced by the temperature of combustion and not the boost level.
A wider plug gap gives a greater surface area for which to ignite the charge. The down side it is harder to fire electrons over a greater gap especially when the charge is more dense. A reduced plug gap will reduce peak VE miss fires.
The stock plug is BKR6EP8. i.e. 14mm thread, 5/8 hex, projected tip, resistor type, NGK heat range 6, Platnuim plug gaped to 0.8mm.
If you run a non presious metal plug you will have to run a smaller gap.
The BGB has both metric and imperial gaps. Not that it makes any difference.
Roger
86turboswap
New member
Corey Darling":r3y6ldec said:
The 90-91 3S-GTE used 7-8mm plug wires in 92 they changed to the current toyota scheme of 5mm wires with clips that hold them into the cap. If you have a 92-93 you can switch to the 90-91 wires you just have to buy a new 90-91 cap.
I prefer the 8mm wires!
BriinumsBo
New member
Im running NGK iridium grade 8 on stock boost, the only mod is de-cat downpipe. would some OEM type grade 6 be better than grade 8 Iridiums? what can go wrong with grade 8 ?