run a colder plug with engine mods or not?

[cals400ex]

i just ordered a 10.8 ross with a hotcam. i was wondering if i should run the colder plug made for the 400ex?

[Silverfox@C&DRacing]

According to JE pistons they say that a colder plug is a must. I am going to try one in my bike :)

[YZROOSTINYA]

run a dpr9z if you have any bore and added compression.

I runa 8 in the dead of winter(10 degrees in the snow)

[2001EX]

So does that mean you should use the plug with the 9 in the number if youve got a higher compression piston?

[Silverfox@C&DRacing]

stock for the 400ex is the 8 if you have a big bore or higher compression piston then run the 9 :)

[Glamis400ex]

I still have in my 8z. Why do I need the cooler plug? What will it do?

I just did a 416 with porting...

Glamis

[cals400ex]

the dpr9z is suppose to keep it a little cooler. it is a colder plug. i don't think you have to change it but i will try it out when i get my cam/piston installed. i have read before that the difference between two plugs is 10 degrees F. is this right? i don't have a clue.

[bmw500hp]

This is an intersting topic. Maybe me but have not seen it before. More info please!

[cals400ex]

only reason why i started this is to find out more info. i am in the process of building a camaro and i was told that for every 100 horsepower you increase over stock, you should go to a one step colder plug. i guess we can find out by trial and error. i am still waiting for my piston/cam but when it comes, i will let you know my opinion.

[bmw500hp]

O.K. colder plug with higher comp. Sounds convincing..got that!

A couple of questions......

#1 What does Curtis Sparks reccomend for his high comp 400ex racing motors.

#2 Have any other notable engine builders reccomended a colder plug..

#3 What BRANDS, other than NGK might we use in this application...:)

[Glamis400ex]

This needed a bump...I don't think this question was fully answered.

I went to my local shop to inquire about a colder plug and he told me I didn't need it...:confused:

Glamis

[Derno24]

your local dealer don't know crap listen to C&D they are the one's building motors each weak not your local dealer

[drummer-on-a-EX]

This is from a article in 4 wheel atv-

I use a DP9EA spark plug. It’s a colder plug that helps lower the head temperature by five degrees. The spark plug is very close to the exhaust port, and it can warp the valves where they seat. If you run the cooler plug and the lead additive it will help the engine last longer.
—Mickey Dunlap, FST

For the whole article-
http://www.4wheelatv.com/detail.asp?id=82

Later - Drummer

[kargaaro]

Your dealer is just going to tell you whatever the book says. He's definately NOT going to tell you to run different plugs. This is an easy adjustment once you must do with a modified engine. I didn't notice a bit of difference in performance running the 9.

[Glamis400ex]

alrighty then...1 DPR9Z coming up. I should really be in good shape here soon with the extra oil cooler, a 50/50 mix of gas and a cooler plug.

Thanks

Glamis

[bmw500hp]

Originally posted by drummer-on-a-EX
This is from a article in 4 wheel atv-

I use a DP9EA spark plug. It’s a colder plug that helps lower the head temperature by five degrees. The spark plug is very close to the exhaust port, and it can warp the valves where they seat. If you run the cooler plug and the lead additive it will help the engine last longer.
—Mickey Dunlap, FST

For the whole article-
http://www.4wheelatv.com/detail.asp?id=82

Later - Drummer

tyler, nice work finding that proof source. I switched to a dpr9z a week ago...no apparent loss in performance...

Keep this info comming just a bit more..:cool:

[bmw500hp]

How does a DRP9Z differ from a DP9EA ??????

Originally posted by bmw500hp
How does a DRP9Z differ from a DP9EA ??????

The DPR9Z is a resistor type (Letter R), and also has a thick 2.9mm center electrode (Letter Z). The DP9EA has a 19mm (3/4") thread reach (Letter E) and is a special design (Letter A).


http://www.in.net/~eholman/

[bmw500hp]

Thanks mx 18..

Man, it's so good to get away from the arguments and chit and get back to to a good info exchange!

Thank you mx..

[bmw500hp]

Originally posted by QuadMX18
The DPR9Z is a resistor type (Letter R), and also has a thick 2.9mm center electrode (Letter Z). The DP9EA has a 19mm (3/4") thread reach (Letter E) and is a Special design (Letter A).


http://www.in.net/~eholman/

mx, checked the site..do you have any idea why Mickey might have chosen the DP9EA...?

Originally posted by bmw500hp
do you have any idea why Mickey might have chosen the DP9EA...?

Im not sure on his reasoning for why he chose that plug. I would call him up and ask to be sure.

Originally posted by drummer-on-a-EX

For the whole article-
http://www.4wheelatv.com/detail.asp?id=82

Later - Drummer

Very good article! I recomend people read it. It has a lot of useful info. Thanks

[bmw500hp]

I agree totally... I would assume that the article was written some time ago but the information is still very valid...

Originally posted by bmw500hp
I agree totally... I would assume that the article was written some time ago but the information is still very valid...

I actually posted the same thing. When was it written? But i went back and searched on the website and it was written January 14th 2002. I thought it was from like 99' when the 400ex first came out but it is only a little over a year and a half old. Anyway back on subject. Did anyone figure out the reason for the DP9EA over a DPR9Z?

[cals400ex]

i would also like to know the reasoning for the dpr9ea. the dpr9ea is the colder plug for my trx 300 4x4. i have actually put it in my stock 300 to see how it would run and it made it really hard to start. i know it isn't needed in a stock 300, but i just wanted to see how it worked. maybe i should just start putting the plugs for utilities in my 400ex. lol :D

[bmw500hp]

Originally posted by QuadMX18
I actually posted the same thing. When was it written? But i went back and searched on the website and it was written January 14th 2002. I thought it was from like 99' when the 400ex first came out but it is only a little over a year and a half old. Anyway back on subject. Did anyone figure out the reason for the DP9EA over a DPR9Z?

Well at this point we know that the plug is colder. Wondering about the thread length and other issues that might make the dp9ea a better choice. Curious to know if deck height has any effect on this decision. Like taking a few "pot shots" at the hypotheticals before we ask the Master...lol

[cals400ex]

i think i still have the dpr9ea at my house. i know i have a few drp9z's laying around. i will look to see if can see any differences with the naked eye.

[bmw500hp]

thats cool, we will have to wait to ask mickey anyway, he out on va-ca for a few...let us know what ya find:)

[cals400ex]

well i just got around to comparing the two plugs (dpr9z and dpr9ea). this is what i found found the dpr9ea is approximatly 3mm shorter. i did not measure to the bend on the plug. i measured from the tip in the center of the plug. the threaded part of the plug (where it seats in the head) to where the bend is welded on, is approximately 2mm shorter on the dpr9ea. the dpr9ea is a about 1mm shorter from the tip (the side that the plug wire connects too) to where the plug seats into the head (the metal washer was not measured). sorry that i don't know the name of this part, but the piece in the middle of the plug that goes inside the insulator sticks out farther on the dpr9ea than it does on the drp9z. its seems as if it sticks out of the insulator about .5mm more on the dpr9ea. i just thought i would post what differences i could see by comparing them side to side.

[bmw500hp]

Cals, thanks for takin the time to compare...personally, I believe i will grab the dpr9ea and give it a shot. Certainly can't be a bad move if Mickey Dunlap does it...Meanwhile, maybe he or a well known engine builder will shed some light on the technical diff..in plug heat range & design. :)