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Discussion Starter · #1 ·
We have agreed that, for the most part, detergents in fuel are the same. Several of us have noticed excessive amounts of carbon build-up all the way at the end of the exhaust system. This kind of carbon build-up is a classic sign of it running too rich, it's not burning off all of the fuel that is entering the combustion chambers. The dealership says the A/F ratio is spot on with factory specs, though should I believe the same dealership that said it completed a 22-point inspection and said the tire pressures were at 32, but actually they were at 22 and 24 PSI?

On my last vehicle we had a similar situation, it was a V6 engine and it's intake design was pretty poor, the fuel trim between the front bank and rear bank was significant enough that anyone who ran nitrous destroyed the engine in short order. There was a company the developed a cold air intake system with a piggyback that corrected fuel trims, the result was around 20 WHP extra. Whereas other CAIs with no form of fuel trim correction were netting between 8 to 10 WHP. MPG observations with the intake and piggyback remained very close to factory EPA MPG ratings.

So there lies the goal, cut out the fat and either improve gas mileage or improve performance while maintaing current gas mileage. Given how much fuel it is wasting, neither of these are impossible goals.

So more air or less fuel? Air is, by far, easier to accomplish with an air intake system, but is that enough air? Does the factory air box restrict that much air?

Fuel is much harder to control, long gone are the days of vacuum controlled fuel pressure regulators on the fuel rail. Most modern systems eliminate it all together and regulate voltage to the pump to control pressure. Being a returnless fuel system is part of its downfall, instead of dumping excess fuel into a return line to the tank, it dumps all the fuel that makes it to the rail. They say the fuel pump module is supposed to purge excess fuel before it leaves the tank, but this carbon build-up shows that system is flawed.

Several of us have pulled out our plugs and the general synopsis was, "They are not that bad," however there was carbon on the plugs and the plugs were not cleaning themselves. Spark plugs have optimal cleaning ranges which is dependent on both the spark plug's heat range and the temperature of the engine. So is the factory plug too cold? Is the engine staying too cold? Is the gap not open wide enough?

Reading the stock number of our plugs (Which are NGK, BTW) they are a heat range of 5 (With NGK 1 or 2 is the hottest and 9 or 10 is the coldest). They do not make a 4 in that stock number or anything hotter. However grab the NGK plug catalog and look up plugs by dimensions and you find hotter does exist. Part number 4043, stock number ZFR4F-11 is predominately a plug for BMWs and if memory serves only comes in V-Power copper, not platinum as our factory plugs are. Notice it has a heat range of 4, one step hotter than ours. The 4043 has the same 14mm thread, 3/4" reach, 5/8" hex and the ISO, extended, projected as ours does.

So here is another train of thought, we can either up the heat range or up the spark energy. I have never understood the materials we use in spark plugs. Copper, the plugs that have been around forever, has the highest electrical conductivity of any metal, right under silver. Platinum has one of the lowest electrical conductivity of metals, yet it's tensile strength is pretty high compared to some copper (Depending whether annealed or hard drawn copper). Now we have iridium, which has double the electrical conductivity of platinum, but still falls far short of copper.

Copper 595.8 1/mohm-cm
Platinum 94.34 1/mohm-cm
Iridium 188.679 1/mohm-cm

So why should you pay $7 a plug for a plug that has less than half the spark energy of the $2 plug?

Let's get some things rolling. Ideas? Thoughts? Opinions?
 

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The reason behind the platinum and iridium plugs is for longetivity, not performance. People do not take care of their own vehicles the way they used to, so it has forced the auto manufacturers to develope ways to make the motors last longer for people who don't take care of thier own vehicles. One of those is the platinum plug which last longer and don't need changed as often. I had a Ford Thunderbird SC that used platinum plugs. While some had changed out for copper core plugs and got better performance, most still used the platinums because of the huge PITA it was to change the plugs in that car. Our plugs seem easy enough to get to, it might be worth it to try running a copper core V-power plug just to see what happens. If all else, you are out maybe $10 on a set of plugs. As far as the resistance difference between the different metals, I'm sure they factor that in when designing the plugs. Remember, even the old copper plugs have resistor cores to help build up the energy before the spark plugs fires to allow for a bigger spark.

As far as the whole air/fuel discussion. You are right in that we can't really control the fuel side of it, but adding more air really doesn't work either, because the computer is programmed to keep within the factory set A/F ratio, so if you add more air, the computer will just add more fuel to compensate. You can "trick" the computer using an IAT mod in the reverse direction as the "20hp chips" you can buy on Ebay. Instead of using a resistor to trick the computer into thinking it's colder outside, you can trick the computer into thinking it is hotter outside so it doesn't add as much fuel. But then again, you are still stuck with the factory air/fuel ratio tables built into the computer. The computer will "learn" it's way around the IAT resistor trick over time. Putting in a hotter thermostat might work better, but then you get into maybe running the motor too hot and causing problems that way. Running a coolant additive that allows for quicker heat up like Redline Water Wetter will help get the motor up to temp faster, and will also keep the motor running at it's operating temp even in extreme heat conditions. I use it in my truck and it does make a difference.
 

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Discussion Starter · #3 ·
The 4043s are in, no check engine light, no misfires. I have started recording mileage today.

I noticed something I did not notice before, the factory plugs ARE copper. I guess the Caliber does not fall in that 83% of new vehicles using platinum or better. I am tempted to try out the Silverstones, never run them before.
 

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I know that regarding the type of material the plugs are made of, in relation to my Wrangler and Jeeps in general that is, that the copper plugs have ALWAYS worked better. The AMC engines have always ran best with plain old cheap Champion truck plugs. Dont ask me why, they just do. Maybe the Caliber is the same way?
 

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Yeah salesman told me this afternoon that the plugs are NOT platinum and need to be changed at the normal interval NOT the 100k most manufactures say.

Cool post guys very interesting read!! Please keep us updated on the mileage for the hotter plugs.
 

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Discussion Starter · #6 ·
First tank went by with the new plugs and it averaged out in the low-20s for MPG. However, right now I have gone 140 miles on this new tank of gas and only spent 1/4 of the tank, that figures up around 38 MPG.
 

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CoolCallie said:
First tank went by with the new plugs and it averaged out in the low-20s for MPG. However, right now I have gone 140 miles on this new tank of gas and only spent 1/4 of the tank, that figures up around 38 MPG.
Being that the fuel gauge isn't linear, meaning it moves slower above the 1/2 mark. That observation means little. Fill it up and see what you get.
 

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Prop1 said:
Being that the fuel gauge isn't linear, meaning it moves slower above the 1/2 mark. That observation means little. Fill it up and see what you get.
X's 2
If I used the same theory I just got 40MPG on my 1/4 of a tank, but the only way to check is to fill back up and divide gallons added into the mileage traveled
 
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