Dpr9z

[maclavin]

Just bought a used Ex that the guy said had a 440 bore kit in it.
He didn't know much about it because he bought it that way and didn't know or know to ask the specs. The deal I got was too good to pass on! So now I have a quad that runs great and will beat my stock Ex buy about six quads just getting into 5th gear.
So here's the question. Any reason it has a DPR9Z in it instead of the stock DPR8Z? The guy told him to run pump gas in it so I am guessing if the comp. is higher it must not be high enough to need race gas or a mix of race gas and pump gas. I would leave it alone but it seems real easy to flood with the DPR9Z and acts a little better with the DPR8Z. Thanks

[flauge]

If i remember right, a lot of racers use that plug so their engine can run a lil bit cooler, which is good for that 440 you got. Im thinking about using that plug but I couldnt find too much info on it.:ermm:

[Phillburt57]

I ran a DPR9Z once and I couldn't notice a difference at all. I don't know if it was because I had poor jetting then or what but I couldn't really tell a diff in temp.

[08400EX]

IIRC, in either the owners manual or the shop manual (maybe both) Honda specifies the "9" as an optional plug for high rpm usage(racing).

Here is an excellent article about Spark Plugs that will take some of the mystery out of this subject. Very imformative and will help you make better decisions concerning spark plugs.

http://www.ngksparkplugs.com/techinfo/spark_plugs/techtips.asp?nav=31000&country=US

[speedjunkie13]

Very good article. Hopefully this will clear up a lot of the misconceptions that are floating around.

[Brauap]

Could I ask, what is a DPR9Z and a DPR8Z?!

[ohsobad_chevy]

Originally posted by Brauap
Could I ask, what is a DPR9Z and a DPR8Z?!

They are NGK spark plugs.....the 8 and the 9 are the heat ranges. ;)

[REDRIDDER]

Originally posted by Brauap
Could I ask, what is a DPR9Z and a DPR8Z?! wow..... you didn't get that this whole thread was about spark plugs and to answer your question the DPR8Z and the DPR9Z are NGK spark plugs.

[maclavin]

Cool guys thanks. I will try both and check the temps. I knew the 9 was colder but i didn't know if it was a must for a 440.

[TRXRacer1]

Originally posted by maclavin
Cool guys thanks. I will try both and check the temps. I knew the 9 was colder but i didn't know if it was a must for a 440. You'll be lucky if you notice a difference. Due to the nature of the design a heat range change would be more noticeable in a liquid cooled machine that could take that less insulated heat away faster. In an air cooled machine like ours it will be a marginal change at best.

[Wheelie]

FWIW--Since I built the motor in my EX I've been running a 9. It's recommended in high compression motors to help prevent detonation and to help keep cylinder head temps and exhaust valve temps down.

[flauge]

I just looked up on it a lil more. I saw somewhere that said the 9 will bring the head temps down 5- maybe 10 degrees. Dont know how true that is but every lil bit helps, especially if youre sitting on the detonation threshold. :ermm:

[speedjunkie13]

It still seems that people are confusing what "cold plug" really means. Just because it is a colder heat range does not mean the entire engine is going to run cooler. the plug heat range merely controls temperature at the tip of the spark plug and inside the combustion chamber and keeps the spark plug at optimal operating temperature. Since a colder heat range dissipates heat faster it could actually put MORE heat into the cylinder head.

So on an engine that has higher compression, it could be necessary to use a colder plug if the cylinder temperatures have raised to the point that the factory plug is nearing it's thermal capacity and the plug is unable to dissipate enough heat to prevent pre-ignition.

It is not the job of the spark plug to control overall engine temperature, that is what the cylinder fins and oil cooler are for. If you are worried about lowering the temperatures on your engine then you need to focus on upgrading the cooling system.

[GPracer2500]

Originally posted by speedjunkie13
It still seems that people are confusing what "cold plug" really means. Just because it is a colder heat range does not mean the entire engine is going to run cooler. the plug heat range merely controls temperature at the tip of the spark plug and inside the combustion chamber and keeps the spark plug at optimal operating temperature. Since a colder heat range dissipates heat faster it could actually put MORE heat into the cylinder head.

So on an engine that has higher compression, it could be necessary to use a colder plug if the cylinder temperatures have raised to the point that the factory plug is nearing it's thermal capacity and the plug is unable to dissipate enough heat to prevent pre-ignition.

It is not the job of the spark plug to control overall engine temperature, that is what the cylinder fins and oil cooler are for. If you are worried about lowering the temperatures on your engine then you need to focus on upgrading the cooling system.

What he said. ^

[TRXRacer1]

Kind of looks like half get it and half don't. Simply put the purpose behind heat ranges is to change combustion chamber temps.