I bought a tune from Evolution Performance that gave my 06 GT another 30 horses over stock…and it feels like 110%. I read an article about this company in Hot Rod and wanted them to handle my engine’s first tune. This was a fun upgrade after the Eibach springs and Hurst shifter I installed last fall. The stock 4.6 does 320 torque; it’s now up in the 350 lb-ft range.
When I shift up at about 4k, third gear feels like a rocket and I can easily hit 80 mph in third at 5k. In other words, this tune dropped the torque curve back by about 1000 rpm. When it hits 3500 in 3rd, the torque feels like a shot of nitrous. That’s what I love, what I’m going for…naturally aspirated power, no power adder. Evo moved the torque curve down so 2nd lasts longer and 3rd packs more punch. Check out this video of Evolution’s Shelby. This would be a fun tune to test at the track, since I’d be able to keep it in 3rd most of the time.
Evo’s custom tunes for my car arrived in an SCT XCal2 with a JLT cold-air intake. I’d guess my low-restriction Flowmasters and CDC shaker air intake are worth 5 hp, so without a dyno run, safe guess is 335 bhp, or 11% power increase. I’ll bet it would do 340 bhp on 93 octane. On top of that, it gets +0.5 mpg fuel economy (20.5). My goal with this car is 400 bhp, doing all my own work (except for tuning). To get there: Comp Xtreme3 cams (+40), Roush underdrive pulley (+10), headers and x-pipe (+15), Canton oil pan and windage (+10). These are guaranteed numbers; I’ve been researching these upgrades for a year now. It’s awesome seeing so much improvement for so little cost.
My car’s 4.6L (281 cubic inch) engine is already putting out more power than a Boss 302, GT 390, or 428 CJ back in the old days, to give this some perspective. Back in the 60s, prior to 1972, horsepower was measured using SAE gross horsepower, which was measured using a blueprinted (i.e. not production) engine on a stand without accessories, so this is the max output of the naked engine, which is not a very useful figure. First of all, production engines are not blueprinted (finely tuned parts ported and polished to perfection). Secondly, the engine does not even have the transmission attached, let alone pulley-driven accessories. Modern engines are measured using SAE NET, which measures output of an engine at the flywheel (pre-transmission) but with all accessories attached.
The 70 Boss 302, which my car emulates, made about 325 SAE gross hp, and ran the 1/4 in the 14′s. The Boss 429 put out about 50 more gross hp. My car is putting out 330 SAE net hp. There’s no precise way to convert gross to net, but the average dyno results today versus reported factory gross hp is about 15% less. So, the Boss 302 probably put out 280-290 SAE net hp (from factory). The ”big block” engines such as the 428 Cobra Jet and Boss 429 put out 350-370 net hp (today), but these engines have stump-pulling torque in the 420-450 range. To nail home the comparison, a competent race driver (i.e. not me could take a tuned but otherwise stock 2005-07 Mustang GT and easily win on the drag strip or race track against a 65-70 Shelby or Boss Mustang.