Back in January, I switched over to Denso IT-24's upon getting my built motor. I was using NGK TR6's before that. I was told that the Denso's were a higher quality plug, provided a better spark, and had better durability. Well, recently my truck started idling rough...i.e. noticable misses and vibration as well as hesitation. So....for S and G's I had the plugs changed yesterday. In short, three of the Denso's were pretty much useless...one of the the plugs was even missing the insulation Now granted, I run some pretty good boost. The truck has been down the track 6 times this year. I guess I would have expected the Denso's to last longer than they did. Anyway, I went back to the NGK's. I figure if I am gonna have to replace my plugs twice to three times a year anyway, Denso's at 80 bucks a pop are not worth it. Some of you may have a differing viewpoint, but I am just sharing my experience.

 

I had many sets of each in my truck. I saw a higher failure rate with Densos than NGK's.

I remember DL having one bad right out of the box at Cecil and making all of us scratch our heads.

Try the NGK BR7's for real high boost, they work REALLY well and are not to cold for the street.

 

Denso's = Great plug if your sponsored and change em every run.

NGK's = Awesome for the average dude

 

I have to agree the NGK's simply hold up better.

 

Your burning up plugs because your tune is off. Plain and simple.

I have run Denso's for over a year now with no problems.

Denso's perform better but they arent as forgiving as the NGK TR's when it comes to a wrong tune. If you get your tune right on the money, you'll see the Denso's outperform the NGK TR's everytime. Just ask BTJ.

BACK ON TRACK

 

what a know it all,

 

JJ, i heard KY Jelly out performs Petroleum Jelly in your life style. I guess thats all in the tune too, huh?

Dialed in tune or not, Denso'a are weaker. They also have the least amount of porcelain, which allows less misfire, but weakens the durability of the plug, severely.

 

If you want durability go to the Autolite AR-93s, you will never burn those up...as for Densos, I put in a set of IT-24s last month and havent had any problems..I noticed that my af gauge wont go rich on me as it used to with the NGK 8s though.....I have also seen a KB powered HD burn up 2 sets of NGK 8s and 1 set of 9s on the dyno before switching to the Autolite AR93s.....

 

I've been saying this about the Denso for over a year and nobody wanted to hear it. If it cost $90 then it's got to be great.

In the beginning people that were breaking them wouldn't even post about it. I don't know if it's because they were embarrassed about paying all that money or the fact there is no way it could be the plugs fault for failing.

The misfire chart that everyone seems to tout is the biggest bunch of bull***** of all. That was not done in a combustion engine where temperatues rise (especially in the plug). Heat can change the plugs characteristics along with the fact of how each plug transfers that heat.

I ran Splitfires until I went larger than a 2# pulley. According to the chart Splitfires are misfiring pretty good above 4500 rpm. It's damn funny that the Splitfires gave me my best ET's and MPH at that time period over any other plug. The NGK TR5 was the next closest. Now anybody that knows anything about drag racing, knows that HP on the big end produces MPH. If the plugs were doing all of that misfiring at high RPM then how do you explain the MPH.

I moved to the TR5 with 4# pulley because I think it is a tougher plug and time has proven that out. I never lost a Splitfire even with the 4# pulley but I thought it was best to be on the safe side. When I moved to a 5# pulley I eventually moved to the TR6 to be on the safe side.

To run your highest MPH the rule of thumb is to run the hottest plug you can get away with. I also discovered that TR5's and TR6's idle smoother at .035" as opposed to .040". You might give up the smallest amount of performance but the idle is very close to the Iridium plugs.

Yes, I tested the NGK TR5 Iridium plug and there was no increase in performance just a smoother idle (which I told you above how to correct). The TR5 Iridium actually cost me 1.5 mph and burned more like the TR6 which also cost me 1.5 mph.

I don't think there are very many out there that have done more plug testing than me on the same lightning for over 3 years. So if you are running 5#'s or less you can use this as a guideline. Anything over 5#'s I'll leave to others.

 

My truck has been dyno tuned. It runs 11.2 - 11.4 A/F and 14 degrees of timing on the street side. I did get an awful tank of gas back in March. Besides that, I think it is a bit presumptious to think that I have a bad tune......Are you saying my tuner doesn't know what he is doing???

 

I've been trying to say this ever since I've been a member here.I used to sell Denso and then switch to NGK's.Reason NGK are hands down the BEST bar none.Shop proven shade tree proven absolutly no defects and I could not say that about the Denso's.When Subaru started sending their US built Legacy's with Denso's we would have 1 out 6 cars come in off the truck with 6 miles on them with a fouled plug change them to NGK and no problems.
Jeff

 

Im pretty sure the tune I had worked very well for the ET's I ran with the mods I had.

Denso's are a good plug, but the OUT THE BOX failure rate is alot higher.

Plain and simple....

URAFAGNITROJJGREY

 

ngks are just straight up a bad *** plug, i used the densos recently for a week and was absolutely disgusted with them, i put my old ngks back in and the truck was just awesome.
ive used them in everything and NEVER had one problem with them. dont even get me going on the price comparison.
oh yeah JJ your a ****

 

I will be switching from Denso IT20s to NGK TR-6s soon myself...

 

You guys would not be saying all this BS about DENSOS if they cost the same as NGKs and vice versa. Plain and simple the DENSOS are a superior plug. If you had problems with DENSOS it was either a problem with the engine or tuning or the plug was faulty before you put it in. But as for performance plug for plug it is far better.