Tales From the Dyno Cell: Part 2

[3]

In this instance, Speed Factory's Dynapack is illustrating why a race-grind cam is not well suited for the street. Too often the ego takes over and the bloodlust for a big number sacrifices all manner of street driveability. The cam in question is not at fault in any way-it actually comes through with flying colors. It's simply a race cam. The fault lies with any misguided enthusiast who puts such a beast in a street car.

The engine in this scenario features a built bottom end, 750cc injectors, a 57-trim T3/TO4E turbo, 3-inch downpipe and exhaust, chipped P28 ECU tuned with Crome tune and a fortified valvetrain [3]. The cam in question is a ZEX 59500. It delivers the goods, pumping up output by a staggering 63 whp, taking peak power from 300 to 363. Kemph is quick to point out that it loses power until 6400. "It's behind down low mostly because the engine suffers a 350-rpm loss in spool time versus stock," Kemph says. "But when it hits, it's fireworks. This cam is good for a drag application, but I can't recommend it for a street-driven car. You'd barely ever rev high enough [on the street] to feel it kick in and you'd be giving up big performance in the D16's sweet spot."

[4]

The Case Of The Redline Crossed
Redline means danger, really. Here is what happens when drivers don't seem to understand the term "rev limit" [4]. The vehicle was a brand-new '09 WRX that barely had 1,500 miles on it when it rolled up to Drift-Office on one of the company's Subaru dyno days. The customer mentioned he was really getting on it on the way to the dyno. The problem was he didn't know when to get off it. He said the car felt a bit off. The first run was low on power and the second featured rod knock at its crescendo. Ouch. "From what we heard," Bob W. says, "it was covered under warranty because of some 'known defective bearings.'"

[5]

The Case Of The Heat Range Round-Up
Yep, the crew at Drift-Office sees it all. This time around, the guys changed the heat range of the spark plugs in a DSM that came in for an A'PEXi SAFC NEO boost tune. The chart shows back-to-back runs with the second pass being the 6 Series plugs (red) versus a 7 Series heat range plug. Peak power jumps from 209 to 221 whp and there are substantial gains evident from pretty much the moment Bob hits the sample button [5]. The gains from 5400 on up are expected because this is where cylinder pressure is on the rise, which would compromise ignition performance. We are a bit surprised to see gains as low as 3500 rpm. Also, always remember to diligently gap your plugs. Improper gapping can perpetuate ignition misses, and when you're talking turbos or forced induction gapping becomes doubly critical.

By Evan Griffey

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