Spark Plugs
Thread Starter
Drifting
Joined: Oct 2008
Posts: 1,354
Likes: 1
From: Inland Empire CA
St. Jude Donor '10
Spark Plugs
I had some dyno tuning done today, and in talking to my tuner, he is experminting with spark plugs. He made a round cylinder with several threaded & machined holes around it for spark plugs. With a clear lexan top & bottom, he then attaches a compressed air line with a regulator to pressurize the chamber. This simulates a combustion chamber. He found that most spark plugs fire perfectly until the chamber reached 160-180psi, then some just won't fire.
Most healthy engines have compression around those numbers, and I'm sure a turbo or supercharger increases that number.
Very interesting test.
Most healthy engines have compression around those numbers, and I'm sure a turbo or supercharger increases that number.
Very interesting test.
Tech Contributor
Joined: Jun 2004
Posts: 20,944
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I had some dyno tuning done today, and in talking to my tuner, he is experminting with spark plugs. He made a round cylinder with several threaded & machined holes around it for spark plugs. With a clear lexan top & bottom, he then attaches a compressed air line with a regulator to pressurize the chamber. This simulates a combustion chamber. He found that most spark plugs fire perfectly until the chamber reached 160-180psi, then some just won't fire.
Most healthy engines have compression around those numbers, and I'm sure a turbo or supercharger increases that number.
Very interesting test.
Most healthy engines have compression around those numbers, and I'm sure a turbo or supercharger increases that number.
Very interesting test.
The 160-180 readings are peak compression readings. The plugs are usually fired significantly before TDC where the cylinder pressure is closer to 100-120 psi.
Those are cold plug results. Plugs are designed to be hot in the center electrode (not only to prevent fouling, but) to increase the electron emission capability to allow easier spark creation.
You neglected to mention the ignition system itself. A small plug gap at those pressures is easy to jump with a quality ignition system. A marginal system (with low energy or a slow primary current shutoff) won't develop sufficient voltage to ionize the gap.
Other factors to consider (if no arc was seen) are the dielectric quality of the wires. The arc (or coil energy) could have taken the easier path elsewhere.
Not trying to shoot down the message. Just trying to add additional stuff to ponder on the subject.
