Where the real power came from in this little V6 after adding headers and high flow exhaust. I modeled the engine with Engine Analyzer and spent about 4 hours modeling various intake and exhaust cam position changes for best WOT power. Then used some cam knowledge and a little experimentation to figure out what the car liked best at light and mid throttle. Woke it up at every throttle position and fixed an annoying part throttle rough running condition this car has always had around 35-50 mph in Overdrive. Car would shudder noticeably in that speed range while driving uphill. The OEM programming had a massive amount of overlap programmed into it at light throttle and that RPM. Lots of internal EGR going on with the stock tune, not nearly as much now. I did keep a substantial amount of exhaust cam retard where the car cruises at 60-70 mph at light load. Fuel economy was better with more overlap there and since it is turning 2,500-3,000 rpm at that point it runs smoothly. However go uphill and I am quick to lose that exhaust cam retard for more torque. I can pull a long 7% grade without it downshifting to 4th now.
Intake cams can be advanced as much as 45°. Exhaust cams retarded as much as 30°. It was very apparant that the Nissan engineers hit their power goal with this engine and could have gone alot higher once I dug into the cam phasing tables. Engine modeling had a simple result. More engine speed = more exhaust cam retard for peak power. I am running as much as 15° more exhaust retard in the 7,000 rpm range and the engine LOVES it. 15° extra cam retard models out to be a 40 hp jump over stock cam position. Difference between making 340 hp and making 380 hp! I also modeled flow numbers of a ported set of heads, ITBs and long tube headers with open exhaust. It was showing the stock cams capable of 430 HP @ 8,500 rpm!
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