Piston Slap: Hocus Pocus…Focus???

Zack writes: Hi Sajeev, I've been following a series of discussion on a MK3 Ford Focus forum; in particular I've been following the technical discussion about how to squeeze more power from the MK3′s new 2.0 GDI motor. Of course, this involves talk of CAIs, Cat-deletes (inadvisable), and free flow exhaust. One of the more curious things to emerge is… …the notion that re-gapping the spark plugs can account for +5whp. I'm dubious to say the least that something seemingly inconsequential could generate that much power. It's almost seems akin to slapping turbo badges on the rear lid expecting some similar black magic. This being an internet car forum there is much breathless back and forth, but few actually explanations. I was hoping you might have heard of this "trick" and whether or not there's any validity. I think for questions like this we need a carforum Snopes.com, but then again we have you. Thanks in advance! Sajeev answers: You sir, have made my day.  Putting me on par with Snopes is a high honor indeed. That said, now I wonder if Snopes is has horribly inaccurate and clueless as yours truly on many, MANY occasions. (sad trombone sound) Now about the spark plugs: I won't say that a re-gap cannot possibly increase horsepower.  I will say that it isn't very probable.  At all. Two things:  Spark plug gap can make a huge difference, especially in forced induction (turbo or supercharger) applications where adding extra boost is on the table.  But that low hanging fruit (i.e. extra power) is usually not there in factory setups: they normally hide the power in tame air/fuel/timing parameters in the engine computer's tune. If it isn't backed by a dyno sheet from a local tune shop, this is pure, un-stepped on, pharmaceutical grade bullshit. Look, I've been messing with Ford products for a looooong time. And while not everything I do has been proven with dyno results, there's always that low hanging fruit proven many times over with other's dyno sheets: conservative factory computer tunes, intake boxes with inlet tubes significantly smaller than the engine's throttle body and mediocre (i.e. quiet and restrictive) mufflers on inadequately shaped crush bend exhaust tubing (older models only).  The first is solved with an SCT tune, the second is free (remove something) or requires a trip to Home Depot for a slice of PVC pipe/glue/black paint,  and the latter is not a big deal with an exhaust shop and a muffler from a 2005-present Mustang GT. But spark plug gap? The forums never show that as a credible performance modification.   Perhaps GDI motors are a game changer, but I doubt it.  That will be optomized to perfection by Ford's engineers, the low hanging fruit will be the things mentioned in the previous paragraph. Best and Brightest, you go right ahead and prove me wrong. Snopes ain't got nothin' on me. Or not.   Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you're in a hurry. from The Truth About Cars http://www.thetruthaboutcars.com

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