Denso's Twin Tip spark plugs
 

I read about Denso's TT spark plugs in a mag the other day and the principle seemed OK: The spark jumps between two tips, both have smaller than usual diameter which supposedly allows lower voltage, etc. Then the claims: Increased power, 5% lower fuel consumption. Yeah, right.

easiest path to ground
 

there will not be spark at both electrodes , the spark will take the single easiest pathway to ground ,
which may vary as the gap erodes and conditions inside the combustion chamber change .

spark plugs with two and more electrodes were OEM specified by many , including VW Audi , Toyota - there was a difference in how the engines ran and overall emissions if the OEM recommendation / specification for spark plugs was not strictly adhered to .

but
on later current production VWs at least
the newest systems use only single electrodes , with multi strike spark

having said that
never use Bosch Platinum +4 or +2 spark plugs , they were never OEM specified for any system and do not perform as well as
the correct OEM specified part# for the system in question

Sparks also jump easiest from a sharp edge or point and not from a rounded nub, that is why NGK V-power plugs seem to work well, the center contact has a simple v grove creating two points for sparks to jump, of course the sharp edge of a standard post works well too, splitting the electrodes is not a new idea.
If you really want to get in deep, the SAE published a book a while back on spark plugs and spark plug design and explained a lot of the ideas behind some of the different designs along with their draw backs.

When the Splitfires came out years ago, I remember that one of their marketing explanations was that the ground electrode was split in order to expose more of the fuel vapor to the spark. I was never sure about the efficacy, though, since it always seemed to me that they were counting on people's infrequent maintenance of their spark plugs (gapping, replacing, etc.) for all of their claimed gains.

If you really want to improve a sparkplug the best way is to use a radioactive element in the electrodes. This ionizes the gases between the spark gap thus making a hotter and fatter spark. Corrosion and fouling of the plug will inhibit the effectiveness of this so it would be best combined with a platinum plug technology. Of course whether you could see a difference from tank to tank is still debatable. :)

From what I've read on these forums (and if I haven't mixed it up), the actual combustion process itself is very close to something like 95% or 99% efficient. Anything that improves on that, even bumping it up to 100% efficient, still won't be noticeable by the time it goes through the drivetrain and wheels. It MAY barely help (performance and/or emissions) in an old engine in desperate need of a tune-up, but a newer engine won't show anything.

Man oh man! I want those radioactive sparkplugs to go with my hydrogen generator. Wouldn't that be da bomb! ;)

-mort

Small piston aircraft have dual sparkplug systems. Part of the warm up and check procedure is to run off one side then the other to check for fouled or faulty plugs or a bad magneto. Normally you run off both and you can usually feel/hear that they get more power from the same amount of fuel running on both sparkplug systems. So a hotter and fatter spark will play a roll. Like I said how much is debatable.

Any gains you see are not going to be from more of the fuel being burned but more so from how fast the fuel ignites and how fast the flame spread happens, that is part of the idea of indexing your spark plugs is that the spark is then facing the incoming fuel/air and flame spread happens faster, dual spark plugs work the same way, igniting the fuel at two points instead of one, the same amount of fuel is burning but it's burning faster, creating more pressure right away.

The only scientific study I can find is from 1931

http://aerade.cranfield.ac.uk/ara/19...report-359.pdf

Note: They won't be pinned down in there opinion on how it applies to a real engine.

I retract the comment about radioactive elements in sparkplug electrodes.

ENGINE VOLTAGE REQUIREMENTS USING SPARK PLUGS PRE-IONIZED WITH RADIOACTIVE GOLD

:o

Edit: at least with Beta radiation. With Alpha radiation there may still be a possible improvement.

Edit Edit: it would help with cold starting though :)

I often question these numbers as they seem to refer to the after cat burn rate, where your fuel gets burnt is more important than how much of it eventually burns. When a typical Detroit motor is running open loop with a 10-12:1 AF ratio 95% of the fuel cannot burn completely in the motor because there isn't enough air.

I am always reminded of the funny cars with the flames coming out of the tailpipe.

Steady state at full operating temperature I don't doubt 95%+ is possible, but during acceleration, warm up or most any other time including idling I doubt anywhere near 95%. Take the cat off a warmed up modern car and take a whiff of the exhaust, if it smells like gas it isn't burning 99%.

i dotn have cats in my 07 charger. and it does smell like gas untill i leaned out the tune more and now its not as bad.

I would love to lean out my 010 cobalts tune, no idea how without a boatload of cash though.

well after I did the headers and other mods. i was at the track and got kicked off for the night because i dumped raw fuel out the tail pipe to the 60' mark. so off to the dyno and tuner i go. a few hours later we got the tune right. I can say the chevy tunes are easier to do and chevy tuners are easy to come by.

I believe that most of the difference goes away if the timing is advanced when running on single plugs. Longer flame travel distance on single ignition needs more spark advance.

The other, often overlooked fact of multi-ground strap plugs is that they take up more space in the combustion chamber, and bump compression slightly.

I had a Chevy Prizm with the 1.8L DOHC 1ZZFE engine, and it actually REQUIRED these twin-electrode Denso plugs. :shrug: Go figure.

I miss that car. Blew a connecting rod through the oil pan.

Got 34MPG no matter how I drove it.

evil03mustang -

Wow, I think I would like that requirement. I'd iesearch it until I found the Yoda who knew why. Here's an old news release from 2010 :

DENSO to Release Fuel-saving Spark Plug / News Releases | DENSO CORPORATION

CarloSW2

...plus, all those metal straps begin to act like both a "heat-sink" and mechanical "shield" around the central element...two physical events that actually reduce the chances of proper, reliable, operation!

Has anyone actually tried these, or found an independent review?

They sound good in theory, but I can't tell from the marketing BS whether they are better for FE than the pointy ended iridium plugs. The iridiums are generally only pointy at one end though, the electrode end, and not at the ground end. Whereas these are slightly pointy at BOTH ends, incorporating an electrode onto the ground. Thus not interfering with the spark and flame front quite so much. Apparently... It does seem feasible.

I am slightly concerned that the ground electrode, being a separate "chip", could come loose with time and wear, and wreck an engine.

Does anyone have any experience with these?

Denso TT
 

I found a link that explains how the TTs are a big improvement over the standard copper / nickel plug shape. http://www.youtube.com/watch?v=9j3s32neHnM

It's in Russian, but you get the idea! The TTs would seem to be the next best thing to the very pointy, dual tipped "SIP" super ignition plug, which seem to be less available for normal cars. The SIPs seem to be "OEM" only, not retrofit.

I'll give the Platinum TTs a try next time.

Hey, that actually makes sense--technical & logical--I'm actually impressed!

1) less "shrouding" of the arc = better ignition probability
2) smaller electrodes--both anode & ground = less heat loss material
3) wider gap = higher probability of ignition
4) smaller electrodes = easier arc creation (closer to 'needle-point')

...wonder how much ignition "retard" actually occurs (red lines closer to TDC)?

...I wouldn't "endorse" them without seeing actual test data, but from that video, I now actually think they MIGHT actually work!?!


NB: I taught electronic ignition systems for 8-years at Arizona West College, Yuma, AZ, and did a LOT of lab/field testing of sparkplugs during those years with help from Bosch, Champion, Autolite and Delco (samples, SAE papers, technical Q&A, etc.).

A small update, if you are considering these, check first whether the Denso "double needle" iridium tough are available - these have even thinner tips. There is a very limited range of these though-& beware most of the "iridium tough" range is not "double needle".

Yep. If you really want to have two sparks, use two plugs. Chrysler's Hemis have two plugs per cylinder. If it were really a unicorn then they'd advertise the extra plugs to get some benefit from it. I think that the head design has a lot to do with any gain from it because they don't use it in other engines.

That sums it all up nicely. It's always my recommendation with spark plugs.

...the Denso TT's sound like a "lower-cost" stand-in for the more expensive "dual-Iridium" plugs, with Titanium being substituted on the ground needle.

Dual plugs are for bad (slow) combustion chambers and for using lots of EGR where the flame spread is poor. It also allows about a point higher in compression on the same fuel grade to get a little more power. Among others, Porsche used it in the 964 (I think) version of the 911, Ford used it as a last gasp development of the Lima 2.3 from '88 to 2001. BMW and Suzuki use dual plugs on 650cc singles. Dual ignition also takes twice the amount of parasitic power to fire as single plug.



MFR recommended plug gap is not the ultimate for MPG or power. The gap is narrower to account for wear. For an old vehicle, I had purchased a Jacobs Omni something ignition. Basically it was a seperately powered coil with a 30A fuse to the battery. Very strong spark.

Anyway, with it came a spark plug tuning guide. It basically said to open the gap at .005" increments until a slight miss occurred at high load and high speed. Then back off .005" and that is your optimum gap. Re-inspect gap every 10,000 miles.

So when the Jacobs ignition eventually failed, I tried this same procedure with the stock ignition. Ya know what? Nearly the same benefit and it didn't cost $400 for a fancy coil. Sure, it wasn't as good as the Jacobs spark, but had I known this procedure in the first place I probably wouldn't have purchased the Jacobs coil.

Now I use the procedure on every ICE I own where I can get to the plugs relatively easily. This due to the more frequent inspection/re-gap interval. Results have been easier starting and smoother idle but I must say I haven't done ABA mpg testing. I can only infer that the part throttle burn is better though.

Edit: I'm stating this because I think a sparkplug discussion is not complete without knowing how to actually use the sparkplug to it's full benefit. Some racers make a black art of modifying plugs if ya really want to go nuts.

Typical 'minimum' spark ignition energy is 30 millijoules for a stoichiometric gasoline air-fuel mixture of 14.7:1 and 9-10:1 compression ratio.

Any inductive (coil) ignition system that provides that much energy will work fine.

However, having MORE than the minimum energy is OK with today's high-EGR engines, because the extra energy permits a LONGER (1,000 microsecond) "arc" duration to exist, AFTER the initial spark, which greatly improves "ignition probability"--the odds of igniting ALL the A/F-mixture that's swirling around within the combustion chamber--remember, EGR is not combustive!

But, it ALSO means the spark plug "electrode" AND ground terminal are FAR MORE LIKELY to get "eaten" away by physical metal loss...which is why noble metals are used; they're not as good electrical conductiors but their "hardness" to both heat and combustion mean they LAST far longer, but only "work" with high-energy discharge systems.

Anecdotal reference,,, BMW has been using the twin 4 prong plugs since the 80's...

1995 1.8 318ti gets consistent 34 MPG on the highway with E0 and 30 with E15. at 70...

Dave

My dad has spoken of horror stories about the slit style plugs arcing to the piston rather than the ground electrode and over time burning a hold in the piston. I don't know where his source is, but he just got a car that OEM calls for a split plug, but also accepts 6 other designs, including an older model plug which he bought whole sale that uses single electrodes. Car is a 1998 Camry, older style is 92-96 camry.

In either case, I would be sure to atleast stick to a plug that the OEM says to use unless there is good proof it is a bad pick.

When I was picking up new plugs for the Sportage November '11, the counter had the Denso TTs on display, it's a neat looking plug, and looked very similar to the NGK Platinum V-Power plugs I ended up purchasing.

I don't remember the exact pricing, but they were in the same ballpark as the NGK plugs..

Design-wise, the Denso TT did have a slightly wider shoulder gap on it, vs. the NGK.

I too was questioning the 'disc' portion of the electrode, whether it was formed in, vs. added: with the platinum cladding, I couldn't tell.

That's what I was thinking. An aircraft engine twin plug setup doesn't need as much advance because each flame front has a shorter distance to travel.

Never had any success with Bosch +4s. I run Champion copper cores in my truck. I could run iridiums, but only to extend plug change intervals...