Denso's Twin Tip spark plugs

[topcat]

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?

[topcat]

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.

[gone-ot]

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.).

[topcat]

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".

[Fat Charlie]

Originally Posted by mwebb

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 .

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.

Originally Posted by mwebb

never use... 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

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

[gone-ot]

...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.

[beatr911]

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.

[gone-ot]

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.

[dwtaylorpdx]

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

[ps2fixer]

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.