Dubly wrote:Horsepower and torque will always cross at 5252. By the looks of the posted dyno graph the numbers are BS.
horsepower = torque X rpm / 5252
torque = horsepower X 5252 / rpm
http://www.carcraft.com/techarticles/868/
Wake Up! These "5252" numbers are just constants to allow for the imperial units that this particular equation is in (ft, lb-mass & minutes) as opposed to the SI unit version of the formula....remember, James watt defined 1hp as" the ability to lift 33,000lb-mass 1 ft high in 1 minute, ...they were small horsies!!)
My day gig is performing OEM engine power curves, and VCT engine developement, among other things, and they definitely do all not cross at 5252 rpm..........plus, where they cross depends on the relative graph scales used for tq & pwr axes.....believe me, some days i've run more power curves, than many people have seen in a lifetime....PROPER curves, held for 45 sec at every 250 rpm, not some flash in the pan Ramp run , in "shootout mode", whatever that means!!!
Generally, larger cam events (duration, IVC & EVO) all move the torque curve up in the rpm range, that's why you get more power (pwr= tq X revs...keep the torq the same, just push it up the rev range, and you instantly get more power)...that's how 1.8 litre 2ZZ toyo's & vtec hondas get big pwr numbers, a little bit of torque at a lot of revs. But the torque integral (area under the torque curve) is generally not much more than any other 4cyl dohc engine....indicative that BMEP hasn't changed (except s2000...much bterr BMEP). True, to shift the tq up higher does require good breathing to maintain tq (it falls away rapidly after peak tq on most engines, and power peak is when rate of increase in rpm is less than rate of decrease in tq...this is REALLY where thay cross!!!!)
But with careful balancing of cam events, and understanding of engine pumping loops, and gas exchange, you can sometimes have it both ways...more tq at higher rpm (more power), but maintaining most of the tq at lower rpms, and higher peak tq...all indicative that BMEP (cylinder filling & conversion of fuel energy into useful work) has been improved. VVT is the easiest way to do this, whilst maintaining driveability/emissions. But with fixed timing, there is a fundamental limit as to what you can achieve, because what's good down low is opposite of what's required up top. And what aplies for traditional engines (read 2v-v8) does not apply to modern 4v engines with big valve area to cylinder size ratios (ie: calculate valve curtain area ...to determine actual cam specs required)...heck my ducati runs STD factory cams 0f nearly 330 intake duration...........and it's still ok at low rpm!
AFM type systems are quite ok with bigger cams, just need to tweak spark maps (ie; base timing adj), but can strike trouble with pulastions & oscillations of the trapdoor at lower rpm,heavy load...but fine at the topend (except for restriction!!)...MAF (hotwire for all 1.8's) is much more sensitive to "backflow"...remeasuring air it has already measured as intake pulsations drive the air back and forth at low rpm, high load, and sometimes near peak tq. PITA to overcome, especially as Mazda MAF's are pretty bad in this respect (except VVT one, a bit better)...need late suby or ford focus MAF!!! 4 cyls te worst, as no overlaping intake pulses to damp the resonances. Secret is to keep overlap around 25-30 degrees, and should fuel OK (symptom is running rich at low rpm, high load)...elasewhere wil be ok. Spark will need to be tweaked though.
............i'm in that line also, just 20 yrs in front of you mate 
..........let it settle in & learn to overcome the difference, you'll be right 
