[FJtest]

Forum member V-C provided me with a set of Denso IKH20TT iridium plugs pulled from his '08 manual-transmission FJC with about 94,000km (58.4K miles) on them.

Shockingly, the iridium tips on the center electrodes were MISSING on two of the plugs, and several other plugs looked like they were eroding so severely that they too would have lost their iridium tips if they had continued to be run in that engine.

These are the correct TT-series plugs for a 2008 1GR-FE engine.


Initial observations:
1. All external markings and the general plug construction leads me to believe these may be genuine Denso plugs. HOWEVER, I'll forward some of the photos to Desno and ask them to verify authenticity.
2. The laser-welded iridium alloy center electrode tip was completely missing from two of the plugs, resulting in a spark gap of over 2.1mm (.083") in the worst case.
3. On the remaining plugs that still had their iridium tips, the gap was ~(TBD)mm ( TBD ").
4. All plugs still had the platinum tip present on the ground electrode.
5. No unusual deposits were seen on the ceramic insulators; there was a smattering of tiny fused-on black particles on the ground electrodes.
6. There was no evidence of overheating of the ground electrode bodies or unusual erosion of the platinum tips on the ground electrodes.
7. There was no mechanical damage to either the center or ground electrodes.
8. On most of the plugs that still had their iridium tip, there was evidence of melting of the iridium tip. Rather than a general melting of a homogenous piece of metal alloy into a large hemisphere (like the tip of a tungsten electrode in a TIG welder), the melted areas had the appearance of hundreds of tiny spheres of melted material, leading me to believe that the iridium tip may be a tiny slug of sintered powdered-metal rather than a rod of solid iridium alloy.
9. On most of the plugs that still had their iridium tip, the point at which the tip was welded to the core center electrode was greatly eroded and under-cut. It would appear that with continued use, these plugs would also have continued to lose material from the weld area and have eventually become under-cut to the point where the iridium tips would have broken off.
10. All plugs showed some residual anti-seize paste in the threads of the plug body.

DENSO TT INFO
Denso states that the electrode material in their iridium-tipped plugs is an alloy of 90% iridium and 10% rhodium.
The 'TT" plug nomenclature stands for 'Twin Tip': there is a 0.7mm diameter platinum alloy tip attached to the ground electrode, and a 0.4mm diameter iridium alloy tip laser-welded to the nickel-alloy center electrode core.
Denso claims that: "The patented formula has the highest concentration of Iridium of any spark plug and outperforms in the most severe engine temperatures resisting oxidation and voltage wear for over 100,000 miles."
In their installation guide, Denso stresses repeatedly that iridium plugs do not need to have their gaps adjusted, and it is crucial that no tool of any kind (gap measurement or gap adjustment) ever contacts the iridium tip.

Lots of technical insight into Denso's TT spark plug design and construction can be found in their patent filings at: US6885137B2 - Spark plug and its manufacturing method - Google Patents

PLUG PHOTOS
Photo 1: Denso plug model ID markings on ceramic insulator

Photo 2: Denso iridium TT markings.

Photo 3: Laser-engraved Denso code on plug body.

Photo 4: Plug missing iridium tip from center electrode; platinum ground tip is intact.

Photo 5: Another plug missing its iridium tip.

Photo 6: Gap on one of the plugs missing its iridium tip was ~2.1mm.

Photo 7: The plugs that still had their iridium tips intact showed various degrees of undercutting and erosion that would likely have caused them to eventually lose their iridium tips.

Photo 8: Higher magnification revealed the iridium tips to be covered with tiny spherical globules of melted metal, looking more like a sintered or powdered-metal part rather than a solid rod of iridium alloy.

Photo 9: A different plug had a similar appearance of the iridium tip: under-cutting and tiny spherical globules. This tip was also not accurately 'centered' on the center electrode body.

I'm not drawing any conclusions here (yet), just presenting what I saw.

 

[FJC-MAN]

Scott, so what is the advantage of running these spendy sparkplugs over the stock 30,000 mile copper core plugs? Changing the plugs every 30,000 really is no biggy.

 

[FJtest]

I have never personally seen or heard of platinum or iridium fine-electrode plugs that look like those above, especially after only 60K miles.

I think something unusual is going on here, but I don't know yet what it is.

More typically, platinum/iridium plugs only show moderate electrode erosion at 100K miles, and not completely missing electrode tips.

Personally, I think the consistent performance over an extended period of time makes this type of plug cost-effective over the long run ... I run them in all my vehicles.

More investigation required ...

 

[JimMorris]

Cheap Chinese counterfeit plugs. There are a lot of them out there online Amazon, eBay, etc. Only buy OEM personally from a Toyota dealer, on online.

 

[FJtest]

Wild speculation, or do you have some specific basis for making that determination?

And of course there are many authorized Denso distributors that provide options for purchasing genuine Denso plugs other than through a Toyota dealer.

 

[JimMorris]

Wild speculation, or do you have some specific basis for making that determination?

And of course there are many authorized Denso distributors that provide options for purchasing genuine Denso plugs other than through a Toyota dealer.

Search on the forum under Engine Performance, January 28, 2023, "Real or Fake Denso Spark Plugs?"

 

[FJtest]

I'm VERY familiar with that thread ... I posted to it several times. I have no doubt that counterfeit Denso products exist.

My question to you is: what specific clues did you see in the photos in the Denso spark plugs in the Failure Analysis thread that led you to conclude that those spark plugs were "counterfeit"?

 

[Virtual-Chris]

Good write up.

According to Carfax, these plugs were put in the vehicle by a previous owner at a Toyota Dealer. So I very much doubt they are fake. Now, I suppose it’s possible that those plugs were replaced at some point before I bought it with fake plugs and that didn’t appear on Carfax.

@FJtest… I’m going to start another thread this weekend to do some diagnosis of my engine using Torque Pro real time data to determine if I have any issues (lean/rich/etc). Problem is, I don’t know what to look for hence the thread. Would appreciate your input on that when I get it posted.

 

[Virtual-Chris]

It’s also worth noting that these plugs are not 100,000 interval plugs… they are 20K interval performance plugs. The I in the model number denotes the lower interval.

So they were in the engine three times longer than their specs dictate.

Service Life | Basic Knowledge | SPARK PLUG | Automotive Service Parts and Accessories | DENSO Global Website

An explanation of the relationship between the amount of electrode wear and electrode materials.

www.denso.com

 

[FJtest]

Interesting on the replacement interval for plugs with "I" as the leading character.

From the link you provided above, it's not clear if the "I" plugs have an expected life of 10,000 km or 20,000 KM. Regardless, either 10k or 20k km is a ridiculously short life ... why would anyone install these plugs in a typical street-driven vehicle??

From Denso:
Lifespan of iridium spark plugs
Not all iridium spark plugs are the long-life type, there are also some that have the same lifespan as a normal spark plug: 20,000 km (light automobiles: 10,000 km, motorcycles: 5,000 km).

20,000 km type [normal lifespan type]

Models beginning with “I”
[Examples] 　・IXU22C 　・IXUH22 　・IK20 　・IQ20 　・IW20 　・ITV20 　・IKH20　　　　etc.

From another Denso site, the TT-series plugs are simply described as:

• Iridium TT Twin-Tip Technology was developed from the Original Equipment Specification Super Ignition Plug (SIP) design, fusing our patented 0.4mm diameter Iridium- Rhodium alloy Center Electrode with an OE style 0.7mm Platinum Tip Ground Electrode.
• Combines the power and torque of a high-performance plug with the endurance of a long-life original equipment spark plug over 100,000 miles

 

[Alpine_FJ]

Wow! Those electrodes are toast.

 

[mstingray]

I have these types of plugs in my performance and turbo vehicles and check/gap them annually. Many people opt to change them bi(annually) as performance suffers once it's couple thou off spec (ex .026 to .028).

IMO they're probably not worth using on the 1GR (it's not a high output engine) unless it's a built/tuned motor, has SC or lives in high altitude or most of it's RPM life up top.

 

[Virtual-Chris]

I have these types of plugs in my performance and turbo vehicles and check/gap them annually. Many people opt to change them bi(annually) as performance suffers once it's couple thou off spec (ex .026 to .028).

IMO they're probably not worth using on the 1GR (it's not a high output engine) unless it's a built/tuned motor, has SC or lives in high altitude or most of it's RPM life up top.

Yeah, I'm surprised these high performance short-life plugs ended up in the vehicle, especially given the work was apparently done by a Toyota Dealership. At least these days, the plugs offered for this vehicle by my dealership are either the copper core OEM plugs (90919-01235) or the SK20HR11 Iridium plugs (90919-01191) which are long life 100K Mile (at least according to Denso).

 

[Kaiju]

Wow is right. Everything looks melted and blasted away. How about a metallurgical test to see if the blown metal parts actually consist of platinum and iridium and not something else? The rest of the steel parts of the plug still look intact and relatively undamaged. Definitely no over-rich indications or oil burning at least. VC, do you know what year those plugs were installed, not the mileage?

 

[Virtual-Chris]

Wow is right. Everything looks melted and blasted away. How about a metallurgical test to see if the blown metal parts actually consist of platinum and iridium and not something else? The rest of the steel parts of the plug still look intact and relatively undamaged. Definitely no over-rich indications or oil burning at least. VC, do you know what year those plugs were installed, not the mileage?

According to the CarFax report I have, the plugs were replaced by a local dealer in May of 2014 at 94K KM. So the plugs were in there almost 7 years and 90K KM. When I first bought the truck in late 2021, I had a local shop do a thorough inspection and they pulled a plug and said it looked good. They must have pulled one of the few that wasn't totally fried. If I had known the extent of the damage to these plugs I would have replaced them right away. Anyway, it's remarkable that it wasn't misfiring given the state of a couple of these which are missing tips.