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Old 08-04-2014, 11:41 PM   #1
samuraivince
 
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Bigger Spark plug?

Can you go up one size spark plug? ( like 5673 to a 5674) my buddy was telling me it's a cheap way to get some power on a Chevy motor, but wasn't sure if it would work on the yaris or if it would just shut the car off. Anyone heard of this?
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Old 08-05-2014, 12:00 AM   #2
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To give you an idea on spark plugs, found this to be a good read.

An important aspect of a spark plug is its heat range, which refers to the rate at which heat is drawn away from the spark plug's central electrode. A spark plug with a short central electrode is a cold spark plug because heat has a short distance to travel to the water jacket in the cylinder head. A spark plug with a long central electrode is a hot spark plug because the heat takes longer to dissipate into the water jacket.

On modified cars you can check if you are using spark plugs of the correct heat range by inspecting the spark plugs after driving in different conditions, such as stop-starting, cruising, and full throttle racing. After driving the car under one driving condition, remove and inspect those car parts . If the spark plug electrodes are covered by soft sooty black deposits, then the spark plug is too cold. However, the soft sooty black deposits can also indicate that your air/fuel mixture is too rich; and if the deposits are moist, it means that oil is finding its way into the combustion chamber. If the porcelain insulator of the central electrode is white or brittle, and/or there is excessive erosion of the electrodes, then the spark plug is too hot; though this can also be an indication that your ignition timing is advanced too far, that you air/fuel mixture is too lean, or that there is a leak on your air intake manifold. If the spark plug electrodes exhibit grayish to light brownish deposits then spark plug is of the correct heat range.

Of course, if the spark plug is too hot, you need to change to a spark plug with the lower heat range, and if the spark plug is too cold, you need to change to a spark plug with the hotter heat range. Anytime that you change to spark plugs of a different heat range, you must to test all driving conditions again to ensure that the spark plug is appropriate for all conditions. In our previous section we looked at the spark plug heat range and how to determine the most appropriate heat range for your particular engine. Now it's time to turn to the spark plug gap.

The spark plug gap, along with the combustion chamber pressure and the ignition timing has a direct bearing on the amount of voltage you require from the ignition system. The bigger the spark plug gap, the more voltage you require to have the spark arc across the gap. The same applies when the combustion chamber pressure is increased. The spark plug gap also has a bearing on engine performance. The bigger the spark plug gap, the more air/fuel mixture will come into contact with the spark and the easier it will be to ignite the air/fuel mixture. However, it's not simply a matter of increasing the spark plug gap and the output voltage from the coil. Firstly, there is a limit to the amount of voltage the ignition system can handle and, secondly, there is an optimal spark plug gap that will best performance for your engine and your driving style.

Ironically, the car manufacturer's recommended spark plug gap is not optimal! The recommended spark plug gap is designed to be adequate for cold starting and smooth driving on a car that is in need of an engine tune up. If you drive your car normally and tune the engine regularly, you can increase the spark plug gap by about 0.010" for better performance and better fuel economy. However, if you drive at full throttle most of the time, you should reduce the gap by about 0.010" for better performance. Ultimately, you'd need to run your car on a dynameter to find the best spark plug gap, and the right ignition timing for your engine.

Remember that when you increase the spark plug gap you need more voltage from the ignition coil to create a spark across the spark plug gap. We'll discuss ignition voltage at a later stage. When a greater voltage is required to create a spark, cold starting and firing fouled spark plugs become more difficult. Therefore you should ensure that your secondary, high-tension ignition wiring is at least 8 mm in diameter, and that it is always clean, dry and in peak condition.
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Old 08-05-2014, 05:55 AM   #3
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Quote:
Originally Posted by samuraivince View Post
Can you go up one size spark plug? ( like 5673 to a 5674) my buddy was telling me it's a cheap way to get some power on a Chevy motor, but wasn't sure if it would work on the yaris or if it would just shut the car off. Anyone heard of this?
Good way to really screw up your car IMO.
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Old 08-05-2014, 07:26 AM   #4
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would be stupid
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Old 08-05-2014, 09:21 AM   #5
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I would not mess with it, as you could change your head temperature, possibly causing some long term damage.


Quote:
Originally Posted by samuraivince View Post
Can you go up one size spark plug? ( like 5673 to a 5674) my buddy was telling me it's a cheap way to get some power on a Chevy motor, but wasn't sure if it would work on the yaris or if it would just shut the car off. Anyone heard of this?
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Old 08-05-2014, 11:05 AM   #6
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thanks for all the input everyone! i know how hard it is to squeeze more ponies out of the yaris.
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Old 08-05-2014, 04:09 PM   #7
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Originally Posted by samuraivince View Post
i know how hard it is to squeeze more ponies out of the yaris.
not as hard as you're thinking .... Follow @tooter

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