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The Denso IKH24 Thread + Plug Gapping and Install Tips!

RjRacing

Go Kart Champion
Location
Philly
This topic has a lot of myths surrounding it and I wanted to make one post explaining the basics on the Denso IKH spark plugs for those who are interested along with some plug install and gapping tips. This is NOT a Denso vs RS7 plug post.

If your car is stock (as in not-tuned), there is no need to “upgrade” from the factory platinum plug, as it’s a good unit for the OE setup and will last a while. The factory plugs come gapped at about 0.028” and the recommended changing interval is 60,000 miles. The factory part number is 06K 905 601D and expect to pay between $10-13 per plug.

Once you have started modifying and tuning your engine, you have introduced more heat and air flow (or boost) into the combustion chamber, so changing the spark plugs to a colder temperature range and reducing the gap slightly will improve reliability, drivability and performance. When you have a tuned car, especially if you are running a setup that is pushing the turbo, fuel system and/or engine to its limits, I suggest pulling your plugs every 2.5-5K miles (or every oil change) to inspect them as there is no better way to checkup on how your car is running over a period of time than inspecting your plugs. Check out this link here on how to read what your spark plugs are telling you about how your car is running…. http://www.onallcylinders.com/2012/12/20/reading-101-how-to-read-your-spark-plugs/

The Denso IKH24 is a Iridium spark plug that is very popular throughout the entire tuning market. It is a proven high performance plug used in many 4cyl 1000whp+ builds throughout the industry and has some very cool tech that allows it to be so efficient. It uses a 0.4mm iridium electrode (smallest in the industry), which allows for the fastest, most precise and efficient spark. The laser welded ground uses Denso’s patented U-grove and taper cut design that also allows for a faster spark and promotes flame growth by sending the spark to the outer edges of the ground. I believe this plug is able to physically outperform any factory VW/Audi NGK plug, especially when running higher boost pressures and aggressive fuels. APR introduced this plug to the our market and suggests running them gapped at .024 +/-.002. They come from the factory gapped at about 0.028" and this plug is one step colder than OE plugs with a maximum service life of 10-15K miles. They only cost $5-6 each if you know where to look and even less if you buy them in bulk, so at this price they are nearly disposable. I personally change them every time I pull them for inspection to keep things running tip-top 100% of the time, which is usually every oil change because I'm anal about maintenance lol.

A few people have had problems with the insulators breaking on the IKH24’s, but 99% of the time this is due to user error. Improper installation and not gapping them with the right tools can crack insulators. If the tune is too aggressive causing knock/detonation/pre-ignition or if your combustion temps are too high it can also crack insulators. The plug is very popular, so much so that there are actually fake Chinese versions of these on the market too that will crack very easily, so make sure you buy them from a reputable distributor.

There is also another performance Denso plug called the IKH01-24, which is their “racing version” of the IKH24. It has a 100% iridium 0.4mm electrode and a 0.8mm 100% pure platinum ground that is supposed to be good for at least 30k hard miles and costs about $20-30 per plug. It has all the same tech as the other desno, except the platinum ground allows it to last a lot longer and run cooler for longer too. Its insulator is much less prone to damage from detonation due to its recessed design and the ceramic throughout is also ~30% thicker too. I personally have never ran it in my cars, but I know of a couple guys locally running it in their tuned MK7 R’s with great results.

For those running water/meth injection, it is highly recommended that you use only iridium plugs and to steer clear of any platinum plug, as methanol can have a negative reaction with platinum and cause it to break down and prematurely corrode. You can still run platinum plugs, but the service life is greatly reduced and expect to change them much more frequently.

And of course there is latest trend in our platform, the RS7 plugs, which is another great option too. I recommend these to people that aren’t capable of checking/changing their plugs frequently because they have a longer service life compared to the IKH24. They are made by NGK and current part number is 06K905601M for these plugs. These plugs are one degree colder, cost between $11-20 each (depending on where you go) and they come “pre-gapped” at 0.028". Some of you may not know this, but the RS7 community actually tightens their gaps when they tune their engines to 0.024”, so you may need to close the gap some if you run into misfire issues as these plugs are still newer to these engines. There seem to be two styles of RS7 plugs on the market too, your standard ground over electrode design and then the "side gapped" style found in most dealers today. You can measure and adjust the gap on "side gapped" style plugs too . You'll want to slide the feeler gauge in at a 45* angle to measure the gap and make sure that you maintain an equal ratio of height and length between the electrode and ground strap as you are adjusting them. Jeff at HS Tuning did a great write-up on these plugs and highlighted the point that these insulator are designed to prevent flash-over too.


Gapping and Install Tips:
Gapping plugs isn’t hard, but it requires the right tools and a little patience. You are going to want to use feeler gauges to get the gap perfect and the spark plug tool to adjust the gap that uses the prong to grab the ground. Do not use the coin shaped gapping tools for adjusting the gaps our plugs, it can damage your plug. Once you think you have done all four plug gaps correctly, go back over them one more time with the feeler gauge to ensure the tension between all four plugs feels the exact same when doing it back to back… I bet you will find at least one that feels different lol. Also ensure that the electrode and U-shaped ground is perfectly lined up, if its not, use needle-nose pliers to properly align them. If you drop the spark plugs at any point on a hard surface or make contact with the insulator with a tool, carefully inspect them to insure no damage was done… but I suggest tossing it out and getting a new one to be safe as the ceramic is very fragile.

If you want a step by step guide on how to gap spark plugs or the installation process, there are YouTube videos out there that can guide you along. Installing your spark plugs will take you less than an hour, even if you don’t know what you are doing (10-20min if you do), but I have some important notes and tips to ensure you get the job done right. First off, getting the coil-packs out of the spark plug tubes the very first time can be a major PITA, but pull straight up on them with a good amount of force to ensure that you do not rip or break the coil-packs. Apply dielectric grease to the coil-packs before re-installing them, this way they will come out 10x easier in future services. Put a very little amount of anti-seize on the spark plug threads before installing to ensure it’s torqued properly and doesn’t corrode. Use a spark plug socket to install them, DO NOT just drop them in the spark plug tubes as this can crack the insulator or close the gap on the electrode. And most importantly, torque the plugs properly to VW’s spec of 18ftlbs… too much torque will crack the insulator (especially as the combustion temperature raises and everything expands) and can cause damage to the threads in the head, too little and it will back off and lose compression.

To sum it up, the IKH24 is a proven performance plug at a bargain price, but it does require more maintenance than some others and that may or may not make it the plug for you. I hope that helps some of you
 
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Mars1

Ready to race!
Location
South FL
I have both the IKH24's and the RS7's, thanks for that in depth and informative post.

Great write up! :)
 

0bLiViOuS

Go Kart Champion
Location
Orange County
Good write-up RJ and explanation of the benefits! I agree that most failures are caused by some sort of trauma to the plug and properly handling them should eliminate possible failures.

One thing people may ask is why you don't say it's 1.5 heat ranges colder due to the design, where the RS7 is a true 1 step colder plug? I consider them the same personally but know you might get someone bringing that up
 

Oldschoolmk7

Go Kart Champion
Location
Yonder
Great information. I used to pull my plugs all the time on my Caliber SRT4 which I was tuning with map clamp. Plugs tell you a lot of information on how your car is running. Good stuff!
 

RjRacing

Go Kart Champion
Location
Philly
Good write-up RJ and explanation of the benefits! I agree that most failures are caused by some sort of trauma to the plug and properly handling them should eliminate possible failures.

One thing people may ask is why you don't say it's 1.5 heat ranges colder due to the design, where the RS7 is a true 1 step colder plug? I consider them the same personally but know you might get someone bringing that up

Thanks! The heat range topic can be controversial because NGK (which is what VW/Audi uses) has a completely different heat range chart than what Denso uses and spending on who you ask, they can be considered the same or different heat rating. On the NGK website, they list a heat range 8 (like the RS7 plug) as being equal to Denso's 24 rating. https://www.ngk.com/learning-center/article/225/heat-range-conversion-chart
 

phobos512

Ready to race!
Your quoted pricing on the RS7 plugs is a little high - they're very easily found for $11 - $15 shipped per plug.

For example: http://www.audiusaparts.com/oe-audi/079905626m

Also, you have a few typos throughout - "silky shoots"; "expect" instead of "except" are the two obvious ones I saw in the first few paragraphs.

All in all a good write up. I will say though that for informational posts like this it helps to keep the personal choice stuff (like silly short oil change intervals) out of the discussion, as people will tend to focus on that stuff and not the information you're presenting.


Sent from my iPhone using Tapatalk Pro
 

Mk7GTl

Go Kart Champion
Location
USA
I agree that the spark plug failures were due to improper gapping and not the plug itself. Do you recommend the RS7 plugs with water/meth?
 

Mars1

Ready to race!
Location
South FL
Does the depth of the spark/electrode into the combustion chamber affect heat range? That could be a way of comparing different manufacturers ranges, nope?
 

RjRacing

Go Kart Champion
Location
Philly
Thanks OP for the informative post!

So now we have a NGK part number for the RS7 plug. I'll be selling my "606" and going with these.

http://www.hstuning.com/product_info.php?cPath=24_32&products_id=5686
Thank you, I added this!

Your quoted pricing on the RS7 plugs is a little high - they're very easily found for $11 - $15 shipped per plug.

For example: http://www.audiusaparts.com/oe-audi/079905626m

Also, you have a few typos throughout - "silky shoots"; "expect" instead of "except" are the two obvious ones I saw in the first few paragraphs.

All in all a good write up. I will say though that for informational posts like this it helps to keep the personal choice stuff (like silly short oil change intervals) out of the discussion, as people will tend to focus on that stuff and not the information you're presenting.
Thank you for your input and you bring up some great points. There were (and probably still is) some errors in there as I typed this up at 2am on an iPad after a few beers last night lol. I received a bunch of PM's over the last few weeks asking for suggestions on this topic, which is why I made the post. I removed some of the opinionated details in there too, but I did make the post based on my experience with these plugs.

If anyone else has suggestions or additional info, I'm very open minded and will consider adding it to the post too :)
 

RjRacing

Go Kart Champion
Location
Philly
Does the depth of the spark/electrode into the combustion chamber affect heat range? That could be a way of comparing different manufacturers ranges, nope?
Here is a picture Jeff at HS-Tuning took of the RS7 plug next to the Denso, you can see the plugs look like they are the same heat rating too...
 

RjRacing

Go Kart Champion
Location
Philly
I agree that the spark plug failures were due to improper gapping and not the plug itself. Do you recommend the RS7 plugs with water/meth?
I think it will do just fine, as it's a iridium plug. I would consider re-gapping them though.

I actually tried these RS7 plugs two weeks ago to see what the buzz was about and had some issues. Looking back on it after doing some research on the RS7 boards, I think it could have been related to the excessive gap as I mentioned above, but I actually got knock at the top of 4th gear and was able to log it too. I also noticed a slightly more rough idle upon cold start, and I did re-check the plug gap after removing them and all four were perfect. Once warm, they ran the same at idle though and I didn't notice any other changes. I exchanged them the next day with the IKH24 plugs and haven't had any issues since. Here is the log with RS7 plugs...
 
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Lagger1

Ready to race!
Location
SoCal
Ok take this for what it is but the rs7 plug uses a different coil connection to the plug. The rs7 should have a spring that contacts to top of the plug that is why it doesn't look like the plug u removed. The reasons you might be getting knock or miss firing is because the connection at the plug is not proper between the plug and coil. I would suggest finding a plug that has the same connection style as the plug you are removing or getting coils that match the rs7 plugs. Best of luck.


Sent from my iPhone using Tapatalk

All GTI's/R (and presumably RS7) coil packs have spring top connectors. Some fall out during maintenance, while others do not.

The latest gen MQB spark plugs have longer insulators for greater flashover resistance. Currently running IKH22 now. When time comes to replace the IKH insulators appear to be cooked pretty good, will most likely replace to OEM style plug to prevent this. Otherwise will continue to run the IKH if this is not an issue.
 

2slowvw

Moderator
Location
VA
Car(s)
2022 Tesla Model 3
Great post, have been running the Densos for a while and have nothing but good things to say about them. Can also get them super cheap. As OP said, you just have to use proper gaping techniques and not damage the ceramics while installing.

I like them because they work and are cheap enough to replace routinely.
 
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