Anyone run the DPR9EIX-9 Iridium Plug?

[NacsMXer]

I'm considering switching to the NGK DPR9EIX-9 Iridium plug for my 400EX. It is the iridium equivalent to the DPR9EA that some 400EX owners run.

If you look at NGK's part number decoder chart here: http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf
You will notice that the "E" designates a thread reach of 19mm. In a standard copper NGK DPR9Z, the "Z" designates a thread reach of 21mm.

So the iridium plug would not reach into the combustion chamber as far as the standard copper plug (19mm reach vs. 21mm). Not sure how critical this is, or how it would affect performance.

Does anybody run this iridium plug in their 400EX? How does it run?

[NacsMXer]

Nobody, huh?

I did some research and the shorter plug reach supposedly should not hurt anything. Newer 2005+ 400EX's supposedly came factory equipped with the shorter thread reach plug.

I decided to go with a Denso Iridium over the NGK however, i'll let you guys know how it works out.

Here's the breakdown of how I selected the correct part number plug. Newer (I beleive 2005 and up) 400EX's came with a NGK DPR8EA from the factory (shorter 19mm thread reach plug). The one step colder heat range plug option for that is the NGK DPR9EA.

The Iridium version of the NGK DPR9EA is the NGK DPR9EIX-9.

Finally, the Denso Iridium equivalent of the NGK DPR9EIX-9 is the Denso IX27B.

Specs for the Denso IX27B:
IX27B (5377) DENSO Iridium Spark Plug
DENSO Iridium Spark Plug 12mm Thread, 19mm (3/4") Reach, 11/16" (18mm) Hex Size, Gasket Seat, Resistor, Removable Terminal, 0.4mm Iridium Projected Center Electrode, Tapered Cut U-groove Ground, .035" (0.9mm) Gap, Heat Range 27

[CJM]

Im curious to know why you would want that plug over the stock one?

[NacsMXer]

Iridium plugs tend to last longer than standard copper, and more importantly they have a MUCH lower misfire rate compared to copper. Many people report a smoother idle, and in general a much smoother running engine through the RPM range. They also tend to burn more efficiently/completely and are more resistant to fouling. XR400 iridium users also report that the motor starts easier/faster than before, has better throttle response, and overall better "snap".

I'm in the process of converting over to NGK Iridium plugs in my blown F-150, and came across this data log someone put together using various plugs in their F-150 Lightning truck. There is an astounding difference in the inherent/normal misfire rate of standard copper/platinum plugs compared to iridium. The smoother revving engine and idle that people report running iridium plugs is directly attributable to this.
http://www.svtlightnings.com/sparkplugmisfires.htm

[Nac's22]

No experience on this with the 400EX but I noticed my 250R ran way better when I switched over to an Iridium plug. I'll be watching this and if it actually makes a positive difference I just may switch over. Keep us posted.

[NacsMXer]

Originally posted by Nac's22
No experience on this with the 400EX but I noticed my 250R ran way better when I switched over to an Iridium plug. I'll be watching this and if it actually makes a positive difference I just may switch over. Keep us posted.

I shall. I noted the same thing with the 2 stroke guys as I was researching. Guys with 250R's and Banshees liked them saying their engines ran cleaner and fouled out less plugs. Pretty sure the newer Honda 450R's come with iridium plugs from the factory as well.

[Pipeless416]

also subscribing.. not for my quad, but car haha.

[wckedclownz69]

ive heard good things about bosch and NGK's platinum +2/+4s.. suppose to last longer and better mpg's..my friend used them on his truck and he said he gets better mpg's and if one ever breaks or gets bad he can just take them in and get free ones.. not to sure about that part..

[CJM]

Apparently denso makes an iridium power plug for the stocker-its part # IXG24, however apparently its a japan only part. I found 1 website that carriers it in japan that will ship to US and 1 plug on ebay, both were very costly at 20/per

I was able to find out on thumper talk they had a hard time finding IXG24 as well, many went with IX24 instead and reported no issues.

http://www.thumpertalk.com/forum/archive/index.php/t-152605.html

edit, found NGKs version for sale on thumper talk! http://shop.thumpertalk.com/ProductDetails.asp?ProductCode=TR_380183 but you need to order 2 minimum. Ill take one if you order them.

[NacsMXer]

Originally posted by CJM
Apparently denso makes an iridium power plug for the stocker-its part # IXG24, however apparently its a japan only part. I found 1 website that carriers it in japan that will ship to US and 1 plug on ebay, both were very costly at 20/per

I was able to find out on thumper talk they had a hard time finding IXG24 as well, many went with IX24 instead and reported no issues.

http://www.thumpertalk.com/forum/archive/index.php/t-152605.html

edit, found NGKs version for sale on thumper talk! http://shop.thumpertalk.com/ProductDetails.asp?ProductCode=TR_380183 but you need to order 2 minimum. Ill take one if you order them.

I came across that very same info during my research lol. The set on thumpertalk is at a great price, but it's for the DPR8EIX-9 plug, which is the hotter heat range plug (equivalent to a NGK DPR8Z copper). I haven't run a stock heat range plug in a long time.

Also, the Denso IX24B iridium plug is = to a NGK DPR8Z copper plug. The Denso IX27B that I bought is equivalent to the 1 step colder NGK DPR9Z copper plug. (These are both the shorter 19mm thread reach iridium plugs). The higher the number, the colder the plug.

I also found out that a Denso IX24 and IX27 (without the "B" at the end) do not have a "projected tip". In the stock NGK DPR8Z for example, the letter "P" designates a projected tip. So either a Denso IX24B or an IX27B is more appropriate since it is closer to the stock plug design ("B" designates projected tip).

Now the Denso IXG24 and IXG27 used to be EXACT iridium replacements for the NGK DPR8Z/DPR9Z. They are of the same design/dimensions and have the same 21mm thread reach as stock. But good luck finding them here. As far as I know they have been discontinued here in the U.S.

So the best thing we can run is the 2mm shorter thread reach Denso IX24B/IX27B. Which, again should not cause an issue with the shorter thread reach (recall that newer 400EX's came with 2mm shorter thread reach DPR8EA plugs from the factory). I found posts from XR400 guys using those shorter iridium plugs for several years without any issues, only improvements in ease of starting, throttle response, etc.

Also if anybody was wondering, here's the difference between a plug that uses a projected tip, and one that doesn't use a projected tip (stock 400EX uses a projected tip). This is an example only, not pics of 400EX plugs.
http://img.photobucket.com/albums/v227/tickford_6/sparkplugs3.jpg
http://img.photobucket.com/albums/v227/tickford_6/sparkplugs4.jpg

[Nac's22]

I don't know much about plug heat ranges, so what is the advantage/dissadvantage from going either hotter or colder?

[dave07ex]

The proper heat range to use is determined primarily by the temperature produced in the combustion chamber. This is directly related to, and determined by, the amount of torque that the engine produces. At some point during the upgrade process your plug's heat range should probably be changed to a colder rating. I don't know at what point that is with the 400ex engine though. I know that when i upgraded the turbo/intercooler/injectors in my car ('02 WRX EJ20T), we went one range colder with iridium plugs. At that point the engine was producing about 100 to 125 (a 50+% increase) more hp and torque than stock. I was told that after reaching the 50% increase mark, that the plug heat range needed to be one step colder than stock. FYI, this was on a forced-induction engine, not an NA like in our 400ex's.

[CJM]

Im guessing that for most applications the regular heat range would work-your not gonna crank out 40hp out of one of these atvs too easily-that would be my guess for where the colder range would be needed.

If anything, for most applications if you can get that IXG24 plug you should be fine.

[martnmx288]

Good thread. I am excited to hear your feedback

[dave07ex]

I'm curious to hear from the hardcore racers here that are making a lot more power over stock. They may be able to shed a bit more light on this subject. Maybe a link to this thread should be posted in the 450R and/or yfz sections so some the people who race those machines could chime in on the heat range thing. CJM is right though, almost alll of us aren't making 40+ hp with a 400ex motor. An iridium plug in the stock heat range can't possibly hurt anything. I would think the longevity alone may be a good reason to make the switch.

[honda400ex2003]

i guess ill play along a bit since i have tried a few things like new coils and such as a test guinea pig.

i think that in 400cc there isnt enough of a difference to make any power increases. .1hp is in the noise of a dyno imo.

it may be that it burns a bit cleaner but if it is jetted correctly theres not anything really to make burn better. it is as complete as its going to get when tuned correctly. a plug isnt really going to change anything if that is the case.

i guilt myself into changing my plug once a year just because. it looks great when i take it out lol.

i guess i dont see my 400 running any better because of a spark plug.

staying tuned for a test on it. maybe a plug will be better than the 50 bucks i spent on a monster coil.

steve

[fearlessfred]

you can determine if you need to go to the colder plug by reading the bluing on the ground strap of the plug if the discoloration occurs in the middle (between the end and the threaded circle base) than you are fine,if the bluing is close to the circle base than it calls for colder plug.as far as the projected tip goes,i think it is a matter of clearance. keep in mind that moving the plug tip in or out has a small effect on ign. timing and shrouding the plug is not normaly a good thing.it seems to me that by going to the shorter threaded plug that you will have to vary slight negative effects shrouding and slightly retarting the timing.who knows,it may all work well for your motor. please post on how it works for you

[JOHNDOE83]

I have a thread that briefly describes this subject.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441780&highlight=johndoe83

[4HundredEX]

Im running a Iridium plug, in the stock heat range. I have noticed it fires up just abit quicker, and it might have just a tad quicker throttle responce. As far as having more power... I say no, and there isnt any possible way a plug alone could do that. I put one in in Feb, just as a trial and error test. So far so good. I will still change it every year as I do in all my powersport toys such as the bike and boat.

It is possible that it runs more efficent, burning more fuel in each combustion cycle ie less wasted fuel.

My truck, 07 Sierra 5.3 vortec, runs iridium plugs from the factory.

The stock plug is a DPR8Z or NGK part number 4730, and it cross references to DPR8EIX-9 or part number 2202 with a little research. You will need the numbers if you go to the part store to get one. My local Oreillys always has the Iridium in stock, Advance and Autozone both have to order them.

[NacsMXer]

I got my Denso IX27B's today from Rock Auto. I didn't mess with the gap at all, they were pregapped at about .032". This is wider than the 400EX's max spec of .028", but you are supposed to run the wider gap with the iridiums.

It is slighty shorter than the NGK DPR9Z, but not by much (2mm). It was pretty nasty outside today...windy raining and snowing, so I didn't get to test ride it with the new plug yet. I did fire it up in the garage and the throttle response is noticeably snappier. Can't wait to actually ride it.

Here's a couple comparison pics. NGK DPR9Z Copper on the left, Denso IX27B Iridium on the right.
http://img31.imageshack.us/img31/302/dsc0004vu.jpg (http://img31.imageshack.us/i/dsc0004vu.jpg/)

http://img535.imageshack.us/img535/2482/dsc0006sz.jpg (http://img535.imageshack.us/i/dsc0006sz.jpg/)

[TORO1968]

Hey NacsMXer,

How's that Denso iridium plug working out for you? I'm thinking about installing one in my 400 as well and just was curious if you thought it was worth the money.

Also, any reason you went with the Denso over the NGK?

Thanks!
Jordan

[NacsMXer]

Originally posted by TORO1968
Hey NacsMXer,

How's that Denso iridium plug working out for you? I'm thinking about installing one in my 400 as well and just was curious if you thought it was worth the money.

Also, any reason you went with the Denso over the NGK?

Thanks!
Jordan

The Denso iridium plug is still letting my motor run like a champ. It's not a night and day difference over a "copper" plug, but it does run smoother and feels snappier. Plus I know for sure that that iridium plug is creating a much hotter and focused spark than a standard plug. Also a lot more resistant to fouling out, as the plug is pretty much self-cleaning.

No real reason I went with the Denso version other than they are known for making some of the best iridium plugs in the world. The Denso version has a finer wire iridium tip, so it is supposed to be the best you can get. I wouldn't hesitate to run the NGK version though, also very high quality. It will have a slightly thicker iridium wire tip, but I doubt you will notice a seat of the pants difference.

If a dealer charges $3-4 dollars for a standard NGK plug, given how often you don't need to change the plug on these motors, i'd pay $6,7, or 8 all day for the iridium version. Tip: if you have an Advance Auto Parts store nearby, they can special order the NGK plug and have it for you the next day for much cheaper than buying online.

[TORO1968]

Great, thanks for the information!