NGK CR7HIX vs. CR8HIX spark plug By HotStuff2 (Read 6,098 times)

[HotStuff2]

This question came up in another thread, but I would like to ask the opinion of others, so I thought a new thread might be in order for it.

This was posted in another thread:

plug should be a CR7 (not a CR8 - which is longer)

I'm running the NGK CR8HIX Iridium IX plug; from what I understand, the CR7HIX and the CR8HIX are identical, except for the fact that the CR7 is a hot plug, and the CR8 is a cold plug. The length and dimensions appear identical between the two.

I did some searching on Google, and this is what the specs for both plugs are:

CR7HIX:
Thread Size: 10mm
Reach: 12.7mm (1/2 inch)
Hex Size: 16mm (5/8 inch)
Gap: 0.7mm (.028 inch) NOTE: .028 inches is actually 0.7112 millimeters
Heat Range: 7

CR8HIX:
Thread Size: 10mm
Reach: 12.7mm (1/2 inch)
Hex Size: 16mm (5/8 inch)
Gap: 0.7mm (.027 inch) NOTE: .027 inches is actually 0.6858 millimeters
Heat Range: 8

So if the specs are identical, the CR8 isn't any longer, no?

I'm concerned that maybe the CR8HIX might be...detrimental to the engine, somehow? Maybe it is longer (which could damage the pistons), and sellers are just posting the specs for the CR7HIX on the CR8HIX? I even emailed NGK to see what they have to say (no response yet, they don't open until 8:30am EST.)

But if the dimensions are identical, having a higher Heat Range is better, no?

-------------

edit: Got a reply from NGK:

Hello,

They are the same plug, except for the heat range. The 7 is hotter than the 8.

Best Regards,

Andrew Hauenstein
Technical & Training Specialist
NGK Spark Plugs (USA), Inc

Therefore, yep, using the CR8HIX is a better option, IMO.

[JR]

Totally disagree. I run the heat range of 7 in all my scooters, they don't start as well especially in cold weather with a 8 heat range and I did multiple long distance MPG tests with mine and the heat range of 7 yielded on a average of 4 MPG on my scooter.

JR

[alleyoop]

Yep, not to many use the 8
Alleyoop

[terrilee]

why would u want a colder plug ?

[HotStuff2]

Heat kills. Heat = bad, running cooler = better.

I'm not sure that the CR8HIX is a "cold" plug, it's just that it can handle a greater heat range - it can handle hotter engines, and the GY6 engines run hot.

[JR]

Again totally disagree and NGK does too.

ngksparkplugs.com/tech_support/spark_plugs/faqs/faqheatrange.asp?mode=nml

[89newbie]

Thinking here heat is the biggest problem we have to shorten engine life. Another guy, another site, got 30,000 out of his stock engine before heat claimed it. I agree run the 7, better mileage and who needs hard starts in cool weather.

[HotStuff2]

Apr 24, 2012 20:33:38 GMT -6 JR said:

Again totally disagree and NGK does too.

ngksparkplugs.com/tech_support/spark_plugs/faqs/faqheatrange.asp?mode=nml

I don't see anything that says NGK disagrees; in fact, one of the bullet points says:

Causes of Overheating:

Spark plug heat range too hot

The most serious result of selecting a heat range that is too hot is overheating. Overheating will cause the electrodes to wear quickly and can lead to pre-ignition.

Also, on the next page, NGK says:

If the engine is to be operated at high RPM, under a heavy load, or at high temperatures for long periods a colder heat range may be needed.

If you put a CDI in that advances the timing & removes the rev limiter (as I'm planning to do), NGK says:

A colder heat range spark plug may be necessary if the ignition timing has been advanced to near the knock level. Higher cylinder temperatures near the knock level will bring the spark plug firing end temperature closer to the pre-ignition range.

Thus, choosing a spark plug with a greater heat range would be BETTER, not worse.

I just don't get it...why would someone NOT want a spark plug that can handle a higher heat range?

[terrilee]

why would someone who doesnt have a 100 miles
on a scooter( any size)
argue with people who have tens of thousands of miles ?


guys ,i see now, you will never win a argument, NO MATER WHAT YOUR LIFE EXPERIENCES ARE, so you may as well give up now.

i mean isnt this the same person who argued with ALLEY about carbs.?
and alley is consider the guru on carbs on MANY forums.

oh well have a good life
im done

[JR]

Apr 25, 2012 10:02:09 GMT -6 HotStuff2 said:

Apr 24, 2012 20:33:38 GMT -6 JR said:

Again totally disagree and NGK does too.

ngksparkplugs.com/tech_support/spark_plugs/faqs/faqheatrange.asp?mode=nml

I don't see anything that says NGK disagrees; in fact, one of the bullet points says:



Also, on the next page, NGK says:



If you put a CDI in that advances the timing & removes the rev limiter (as I'm planning to do), NGK says:

A colder heat range spark plug may be necessary if the ignition timing has been advanced to near the knock level. Higher cylinder temperatures near the knock level will bring the spark plug firing end temperature closer to the pre-ignition range.

Thus, choosing a spark plug with a greater heat range would be BETTER, not worse.

I just don't get it...why would someone NOT want a spark plug that can handle a higher heat range?

I don't see anything that says NGK disagrees; in fact, one of the bullet points says:


Then you need to get better reading glasses:

It is a common misconception that spark plugs create heat. They don't. A heat range refers to how much heat a spark plug is capable of removing from the combustion chamber.

Selecting a spark plug with the proper heat range will insure that the tip will maintain a temperature high enough to prevent fouling yet be cool enough to prevent pre-ignition. While there are many things that can cause pre-ignition, selecting a spark plug in the proper heat range will ensure that the spark plug itself is not a hot spot source. More information about heat ranges can be found here.


It plainly says the spark plug does not cause heat but in the proper heat range removes heat.

The bullets you are refering to states one fact the hot and cold of a plug and what happens "if" you choose the wrong heat range.

We all know scooters come set lean and most people myself included set them up properly by adjusting the carb and doing a good PDI and by that alone they will run at the correct setting which is richer than the OEM settings thus in lots of cases especilly with my water cooled scooters a 8 range is then too cold. Add more fuel, neede hotter plug easy and simple.

I also have a 150 Bali and none can tell me about heat, I have a custom made oil cooler that works and I can even tell you oils that run hotter or cooler not by guessing but by tests I've conducted myself.

BTW I live where like last year we had 39 straight days of 100F+ temps and I ran my scooter in 105F heat on several occassions and it purrs like a kitten.

I agree heat is a enemy of any engine, a enemy to everything humans included but the 7 range plugs I run are not causing a heat problem and that's not a guess either, I have thermometers and temp gauges so I know what I'm saying.

I'll stay with the extra 4 MPG.

JR

[HotStuff2]

Apr 25, 2012 10:30:02 GMT -6 terrilee said:

why would someone who doesnt have a 100 miles
on a scooter( any size)
argue with people who have tens of thousands of miles ?


guys ,i see now, you will never win a argument, NO MATER WHAT YOUR LIFE EXPERIENCES ARE, so you may as well give up now.

i mean isnt this the same person who argued with ALLEY about carbs.?
and alley is consider the guru on carbs on MANY forums.

oh well have a good life
im done

What? I never argued with alley about carbs! I just asked questions. I'm not arguing here, I'm trying to post what I've read, and make sense of it.