No, real-time plug insulator deposit happens within a very short period of time.
Not on the motors I've built.
Some of the old straight 6 gas motors blacken up a bit but no light brown in this short time.
And some of the bike engines have the plugs read every run.
That's the shortest plug change interval I have seen in modern cars.
A little research on the web results in this cross-reference page: DENSO SPARK PLUGS
It appears that the car comes with the low end basic plug from Denso (not surprised). When it comes time to change mine, it appears moving up to the IXU22, their Iridium Power line, or VXU22 - their Tough line. They can yield minimal performance and fuel econ improvement, but most importantly, longer plug life (5x normal plug) in the case of the Tough line. DENSO SPARK PLUGS - Basic Knowledge
The IXU22 seems to be $12 a piece. VXU22 is hard to find, the only place I found in Japan is about $16 a piece.
Perhaps someone will know a better place to find Denso plugs. JCWhitney is a dealer, but their Denso catalog does not list smart in it.
I build a both motorcycle and small block ford and chevy racing motors as a side (cash producing) hobby. And while not a NASCAR or F-1 level tech I do have a world of practical experience... and a waiting list each season for one of my motors.
Both you guys are correct from a different perspective and I hate to see us argue the Process....
The real point is there are ways to "Read" a plug and make educated guesses about the fuel trim and cylinder health relating to rings and valve guide seals, in some cases we can see evidence of leaking intake air filtration, or a too heavily oiled gauze filter, or faulty Exhaust Gas Recirculation system
The various techniques to use the plug condition to diagnose something vary by what you are trying to detect...
When I simply want to use plug deposit color and density to tell me about fuel trim:
We start with a fully broken In motor. ON the test stand, or in a vehicle, first run is to get to full operating temp... then we insert new plugs.... 5 minutes of idle time to get plugs in their heat range soak.... then a run through all torque-loaded gear shifts up to 15~30 second duration in top gear loaded torque ( no free reving)...CUT motor and stop... then pull and mark each plug
These brand new plugs will have sufficient deposits to visually see (usually with a 3x~4X lighted mag) what we need to see to tune the ignition and fuel delivery systems....
In our quest for power (LATER) we still use the plug condition to determine if the headers, air filter, crank case breather or EGR systems are doing their thing properly...
Exhaust headers are always a compromise and many of our projects are one off adaptations to fit a vehicle... if you have all the plugs running Grey/deposit free with the test set up and the new set makes one (or more) plug soot up or (rarely) evidence of electrode erosion, then we can tell the primary tube for that cylinder is restricting flow... or (rarely) the scavenging effect from other tubes has that one sucking too hard leaning out and super-heating the exhaust valve and plug
Actually it is much More complicated because we have to consider valve lift, duration, and many other factors
Some of this is pure physics and science and much of it is ART or historical wisdom...
The bottom line is; Plug condition can tell you a lot and there are various techniques to prepare to use that information.
OK, no more.
And your right about the headers Fred.
I remember the first set I welded up when was a teenager.
That old GS motor never knew complications until I started screwing with it. To this day I only use proven exhausts as dyno runs have shown that lots are all show and no go. Well, maybe "go" if money flying out of my wallet is the only performance result.
All this is a moot point however as I am going to be buying a Smart that has no spark plugs!
Sure wish I did not have a day job some times... I would love to own a motor and chassis dyno...currently we borrow or pay for time on a local one....
Back to plugs.... there is a Brit tuner claiming some exceptional gains just in a plug change on this motor...so far Big Performance is being real coy on what plug they used and the few folks who got the mod are being equally tight lipped...
I scour several sites every few weeks to see if some one spilled the beans or cracked the code
I have a sneaky suspicion that they did four things:
I assume they noticed this motor runs a tad rich
Used one range hotter plug
Used thin Iridium or platinum tipped plug
Opened the gap way up
Indexed the Plugs so ground electrode is not shrouding the tip
... Indexed the Plugs so ground electrode is not shrouding the tip
I "sort of" tried that once with a set of "Splitfire" plugs, but didn't feel anything noticibly better. My engine consultant in the UK, Roger King Engines, had no enthusiasm for their use. I have seen others file the ground electrode to a quite narrow blade, claiming some improvement. And still others tried twisting the electrode off-axis but with no claims of sucess. In the later case they may have been contorting the flame kernel off to one side and getting an inconsistant or asymmetric burn.
In the end I found it best to spend my time and money on lots of fresh, best NGKs. In the case of the NGK "R"s, the ground electrode approached the center electrode at an angle from the side but did not crossover the top and "blind" it. They wouldn't last long enough for passenger car use.
Last edited by Old smart; 05-24-2008 at 11:24 AM.
Reason: Added photo. Note ground electrode on left (not box).
on what the hot plug to install will be. I am sure that there will be one other than the one shown by Fred. I have always gotten great performance, gas mileage and spark plug mileage from platinum tipped plugs or maybe even a more advanced type than that will be available by the time our smarties get 30K miles on them.
Indexing plugs or using the expensive multi spark pulsars can be seen on the dyno as a 2-5HP adder ...intresting that if you do both there is no added gain
Mostly we screw with these meager yield techniques simply as a way to optimize every system we can.. in the search to eek out every possible advantage or simply to keep on PAR with the other tuners
I have spent the time to do some of the techniques on my private car, motorcycles and trucks... no measurable gain at the BUTT or gas pump with any single mod but I can report that a combination of the correct intake, exhaust, fuel delivery, and spark control can all add up to 7~15 extra ponies and modest increase of MPG
Unfortunately these increases are all on 3L or larger motors...on my 1.3L motor cycle motor the gain is too minuscule to really tell
I am too new with the Mitsubishi design to know if there is really any factory inefficiencies that we can exploit... in my experience the last 7~12 years the factory guys are doing a great job of eking out max performance from the get go... the days of finding 20% or more out of a factory motor are mostly behind us
This of course is an observation from a mechanical engineering point of view... I am keenly aware that the world of computer mapping the various control curves has a lot of potential to optimize the power band
Also note... it is a good thing that at least one of the two O2 sensors is the Bosch Wide band version
The normal 02 sensor is a low tech and low cost device with a 0 to 1 volt range of change...and the individual points between 0 and 1 volt are few so it is a course calibrated device
Some years back Bosch developed a Wide Band sensor that out puts 0 to 5 volts and because there are more discrete steps from rich to lean it is a finer or closer calibrated unit
With more precise data, the ECU can be programed to have many more steps in it's mapping curve.. thus being more precise in it how it manages the ignition timing, valve phasing (we have variable intake valves), and fuel injector timing and pulse width
The motors, with the more expensive sensors can stay longer in the best optimum fuel air ratios to maximize power and fuel efficiency
The second "down stream" O2 sensor is ALWAYS part of the health check for the catalytic converter and almost always a narrow band lower cost sensor
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