Is a BPR7HIX compatible with a BPR8HIX?

[azraeille]

For the second time, I've been sent the wrong sparkplug. The first was my mistake. I looked at my manual's suggestion instead of the plug in the engine. The second time, I don't know how it happened.

Point is, I ended up with a BPR7HIX instead of the 8

This is the 7. cf.mp-cdn.net/67/c8/a899308a9284abd8c5d41d391e97.jpg

Are these two plugs interchangeable? I've already spent $20 on plugs and I'm not in a hurry to spent another $10.

[scootinbow]

yep it will work just a colder plug is all

[jeremym]

yeah the number on the plug indicates the heat - lower number being hotter and higher number being cooler. I may be wrong but a hotter plug means a cooler engine and vice versa but somebody can correct me if that's wrong

[gregw]

A lower number retains heat, a higher number sheds heat to the head. A lower number can cause pre-detonation (plug so hot it will fire the cylinder upon sufficient compression, not spark timing, resulting in pitting of the piston crown). It's always safer to go to a higher number than a lower number if in doubt. Personally, I would not run a 7 if my manual said run an 8, especially on an air cooled scoot. Good luck!

[skuttadawg]

I use the 8 . I tired the hot plug when I was 16 thinking it would be better but it ran too hot and made the piston soft seize . They usually come gapped right but I would double check before putting it in . My scooter dealer told me he serviced a 2T that would soft seize . It could idle for a long time and be fine but it would seize in less than a mile . He pulled the plug and saw it was the hot one and in the summer time . Replaced with the correct one and made and easy 60 dollars

[slimshady]

I was looking in to switching to a Iridium plug. I use a ngk bpr7hs and i think i should use a bpr7hix does this sound correct? Maybe i'm just doing to much homework.

[skuttadawg]

I tried the 7 and it melted the prong off

[slimshady]

I just put a BPR7HIX in when i took out the old plug. I looked at the chart and it looks like it was good not to rich or lean. Ill pull the new one out in a few days.

[skuttadawg]

Run it at WOT and hit the killswitch . Pull over and remove it to see how it runs . Mine was a dark caramel . It ran perfect then poof blew the head gasket . Pulled the plug and I was like WTF ? You may want to get an 8

[OverReved]

Aug 20, 2012 20:35:51 GMT -5 skuttadawg said:

I tried the 7 and it melted the prong off

Aug 20, 2012 21:14:32 GMT -5 skuttadawg said:

...Mine was a dark caramel . It ran perfect then poof blew the head gasket . Pulled the plug and I was like WTF ? You may want to get an 8

You melted the prong off Skuttadawg, because the plug couldn't dissipate the heat quick enough. The plug tip needs to reach over 900 Celsius to do this and is easier to make happen in a lean burning engine. Your head gasket blew out because the pre-ignition caused by your now too hot (temperature hot and range hot)spark-plug initiated detonation. When detonation occurs the pressure in the cylinder spikes to extremely high pressure, momentarily, possibly reaching the thousands of PSI range. This is the magic that can knock holes in pistons, bend aluminum connecting rods, and blow-out head gaskets in just a few strokes of a crankshaft.

Spark-plugs are not magical or confusing. When you have one installed it needs to operate at the tip with a minimum temperature of around 450 Celsius to reach its self cleaning point.
What keeps the plug in this range, and not above or below it for the engine it is installed in and the conditions it produces, is determined by where the center electrode is able to dump its heat into the spark-plug body and the head.

Cooler plugs(Higher numbers) are able to connect the center electrode to the body of the plug sooner and therefore do not reach their higher temperature as readily.
Warmer plugs(lower numbers) will have to transfer their heat further down the center electrode to cool them selves off and will run at higher temperatures because of this.

When determining plug heat range it's always best to start with a cooler plug and work down( higher to lower in the numbering system) to the range that works for the conditions your engine will produce as it burns the fuel. Starting with too hot a plug can cause dangerous detonation conditions possibly destroying an engine very quickly.

I have a 12:1 compression engine that is water-cooled and runs slightly lean so it makes a lot of combustion heat that remains in the head instead of flowing out with the exhaust that has to be dissipated. Combined with my usually full throttle driving I use an NGK plug with a heat index of 11 to keep the plug COOL. NGK plugs range from 2 to 12 in their heat indexing. Number 2 would be the hottest plug and 12 the coolest.

[OverReved]

Jun 4, 2012 23:51:41 GMT -5 scootinbow said:

yep it will work just a colder plug is all

The Original posters 7 plug is a hotter plug than the 8 he intended to receive.

Jun 5, 2012 1:52:17 GMT -5 jeremym said:

yeah the number on the plug indicates the heat - lower number being hotter and higher number being cooler. I may be wrong but a hotter plug means a cooler engine and vice versa but somebody can correct me if that's wrong

Lower number=hotter
Higher number=cooler
You have that correct.
Hotter plug means the end of the spark plug operates at a hotter temperature -- So you are incorrect there.

The spark-plug has nothing to do with the actual temperature of the engine, just the temperature of the tip of the plug which is determined by how the engine performs in general. The tip can overheat in an engine that is running coolly or be too cool in an engine that is running hot enough to melt parts.

[skuttadawg]

I switched to BR8HIX the one with P is a longer thread . I found it the cheapest at Amazon which has bulk prices on the standard one

[slimshady]

I've been running a BPR7HIX for about 100 miles the plug looks good. Correct color, i have not noticed any change.