I was told that the NGK BPR7ES is a colder plug than the stock plug on the evo and this is what I needed to run for a modded car running more boost to help prevent detonation and such. I bought a set and I pulled out the stock plug and it was a nice clean brown tint but I noticed that the heat range on it was a 7 as well but the plug is a Iridium type plug, so is a copper 7 colder than a Iridium 7? Does anyone know the breakdown meaning of the part numbers on the NGK plugs. I belive that R is a resistor type plug and the number is the heatrange but I don't know the rest to define what would be best. Any help would be appreciated. Thanks!

 

If I remember correctly the BP stands for the thread size, eg, 14 mm, the R is for resistor type, the 7 is heat range and the E stands for extended electrode.

You can get the same plug with a non extended electrode without resistor and it is called a BP7HS.

 

So the BPR7ES is not a colder plug , just cheaper then right?

 

Correct. The stock Iridiums are heat range 7. They are also $35 from you dealer.

I tried the coppers on my car, heat range 8, and didnt like them. BR8ES. Seemed to not fire as good, even with varied gaps. I tried from .020 to .028 and didnt like anything.

I ended up spending $14 a piece for some HKS Iridiums. They are just like the stockers, but a heat range colder, range 8. I think the part # is S40G or something. check www.hksusa.com to order some.

 

the heat range is the same on each plug (7) but the copper plug runs much cooler then the iridium... iridium retains more heat then then cooper, iridium is put in cars because they last longer then the cooper... i just repalced my stock plugs with the BPR7ES and my car's egt are 100 lower from idel to red line... B

 

Understandable, Thanks for the egt input!

 

Is that right? Where exactly did you come accross this information? Plug heat ranges are supposed to refer to the average electrode tip temperature dictated by the plugs design and ability to draw heat away from the electrode. If the iridiums actually run hotter then wouldn't they have a different heat range designation?
BTW iridiums have other advantages other than the fact that they last longer. Go read on any of the manufacturers web sites.

 

The "P" in BPR stands for protruding in the NGK letter designation & this isnt what you want to run in most turbo engines.

 

i have been racing 4g63 since 1993, i have a 10.80 1g, and 12.30 2g. the BPR7ES is what i been runnig for years with no problems... if you go to any DSM shop abd ask them what they run and they will tell you BPR7ES... B

 

I do not think that anyone is saying that copper plugs will not work, it's just that iridiums work better. Copper has a very wide thermal cunductive range based on it's operating temperature. As you approach it's limits (such as in this application) the thermal cunductivity begins to drop. Irdium has a far more consistant/narrow thermal cunductive operating range with a far higher temperature operating range. I might be interpreting the specs incorrectly here, but in this application it seems that iridium has almost identical thermal and electrical cunductivity compared to copper. Plus it has several other properties that allow for a superior design and a much longer operating life.

Copper

Thermal Conductivity 147 - 370 W/m.K
Thermal Expansion 16.8 - 17.9 10-6/K
Resistivity 1.82 - 4.9 10-8 ohm.m
Melting Point 1979.33 °F

Iridium

Thermal Conductivity 140 - 148
Thermal Expansion 6.5 - 7
Resistivity 5 - 6 10-8 ohm.m
Melting Point 4436.33 °F

Info from http://www.azom.com

For example the smaller electrode can fire off easier using less energy so the electrode tips do not necessarily run hotter, just because the tip is smaller. If that is the logic that leads you to believe that a smaller tip runs hotter?

 

Thanks for the info, I have a much better understanding of why and how iridium plugs outperform copper. I knew I could certianly feel a difference between to two plugs but I didn't know why. I now know what I am sticking with.