Using Colder Spark Plugs
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Joined: Feb 2003
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From: saratoga, ca
20hp loss for 5 degrees retard? Louie showed a slight change in HP and its peak was pushed out a few hundred rpm. I retarded my timing 6 degrees and lost no hp but lost 15ft-lbs of torque down in an RPM range i never use, so the result was all good. I also am using the colder plug for these reasons, and they dont seem to have an issues with build up. they are a little darker than im used to, but they made no difference on the dyno.
are you saying that a 2 degree net change caused a 20 hp differnce? (you said 5 degrees lost 20hp and 2 degrees was the best HP)
mk
are you saying that a 2 degree net change caused a 20 hp differnce? (you said 5 degrees lost 20hp and 2 degrees was the best HP)
mk
Try it! Plugs are cheap. Start with the 5's (coldest available in this plug). If the insulator doesn't stay white, move up to 6's.
Which way are you trying to move the powerband? Up or down? Retard is up. Retard will also reduce cylinder pressures, so you have even less chance of pinging.
I was surprised that on the dyno with my '86 (similar to GT cams), 4-5° crank retard lost 20ish HP, and strangely, the exhaust AFR was leaner. 1-2° retard made the most power. I'm running straight up at the moment, and I miss having some advance for around town. 4-5° advance is nice for more grunt at low rpms. More advance requires better gas, and plugs to combat pinging!
Which way are you trying to move the powerband? Up or down? Retard is up. Retard will also reduce cylinder pressures, so you have even less chance of pinging.
I was surprised that on the dyno with my '86 (similar to GT cams), 4-5° crank retard lost 20ish HP, and strangely, the exhaust AFR was leaner. 1-2° retard made the most power. I'm running straight up at the moment, and I miss having some advance for around town. 4-5° advance is nice for more grunt at low rpms. More advance requires better gas, and plugs to combat pinging!
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From: Alabama '88 928 Automatic
For casual readers, keep in mind that the pros are discussing two different types of Timing in this thread:
1. Cam timing (when intake & exhaust valves open/close)
2. Ignition timing (when the spark plugs fire)
1. Cam timing (when intake & exhaust valves open/close)
2. Ignition timing (when the spark plugs fire)
Inventor
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