Quote:
Originally Posted by FastCougar
Well, I replaced the wires with stock units and the upper RPM stumble is still present. There is definitely an ignition and/or fueling issue above 6K RPM. Below that limit, the engine runs perfect now with the new tune and has plenty of power above 3K RPM.
I just thought of something ... my plug gap! I'm running a stock gap of .054 inches.
Now, keep in mind, I'm running 9:1 CR pistons with bowl work done on the heads, so I'm figuring roughly 8.8:1 CR. Wouldn't I want to adjust my plug gap considering I'm a full point of compression lower than stock? I would figure that I need to increase my plug gap to say .060 inches. Sound right?
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No, leave it stock or even a tad tighter. The plug gap is set to cause the highest energy spark. Tighter the gap with no changes to the coil voltages and you get a lower energy spark. Raise the gap will give more energy but also maybe a misfire. Lowering the compression will make it spark easier as well but not significantly I think.
If there is a higher rpm stumble then we could have ignition, fuel, air issues...or electrical connection issue that could cause a problem in one of those areas.
We have to have the datalog of every spark related parameter (spark, knock sensor, max allowed, borderline knock, mbt if available, etc), MAF, rpm, throttle position, load, maf counts, IAT, ECT, fuel trims, O2 sensors, and any relevant piece of information you have..