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JPC Racing Three-Valve Intake - Short Running
MM&FF Tests The Jpc Racing Three-Valve Intake On A Supercharged '06 Mustang GT.
We also kept the stock throttle body because continual testing has shown little gains in centrifugally supercharged applications. JPC offers the intake with a single opening for those customers who have (or want) to use a single-blade throttle body.
One look at the intake and people quickly assume the short-runners will kill low-end power. Conventional theory about short-runner intakes versus long-runners dictates that the torque will decrease slightly at low rpm because the runners are tuned to flow more efficiently at higher rpm.
"This is typical of short runner intakes and because the runners are shorter than stock, the power band is shifted up. The runners are also slightly larger than the stock port dimension to aid in airflow. Our runners are about 33 percent shorter than stock and measure 6.9-inches in length. Again, we were shooting for an intake that had a decent runner length, but was shorter than stock to move the power curve up where it is easier to make power," noted Burcham. "Theory is great, but physical testing is the only way to know if your ideas are good. We went through a great deal of effort to keep the runners as long as possible, and since the runners are all cast with the same tooling, they're all equal-length."
Burcham and his staff tested several different designs before settling on this final product. The runners may appear short, but the real story lies inside the plenum box, where the runners extend a few inches into the center.
One theory that was put to the test was the addition of bell mouths at the runner openings in the box. Burcham explained, "if you look at any fluid dynamics book, it will explain that a bell mouth is the ideal way for fluids to enter tubes. We actually did a lot of testing on this for our own education during development.
"Several radius dimensions were tried on a flow bench to determine the ideal radius. Testing showed a 10-15-percent gain by adding a bell mouth to the end of a tube on our flow bench. One of the things that is interesting is that rounded edges are ideal for air speeds below the speed of sound and that sharp edges are good for air speeds above the speed of sound, so everything is as round as possible everywhere."
Real world testing proved the bell mouths were effective, even in this application where the fuel is added after the bell mouth openings. On the dyno, theories and real-world results clashed during our testing. Despite popular belief, torque didn't suffer, and when comparing peak versus peak output, the JPC intake gained 44 lb-ft of torque at the wheels. At one point in the curve, torque was 50 lb-ft better than the stock plastic unit! From 3,900 rpm until redline, the JPC intake produced more torque. That rpm range is where you are going to see quicker results on track, too. Below that rpm, the curves fluctuated back and forth but didn't stray too far from each other.
Moving to the horsepower side of the equation, 3,900 rpm seemed to be the threshold once again where the JPC intake's rwhp gains became apparent. Comparing the peak rwhp numbers, the JPC intake gained 23 rwhp (538 versus 515) as both peaks came at 6,500 rpm. We thought the intake would help this engine achieve 7,000 rpm, but it came back to the stock camshafts hurting the rpm capability.
Horsepower gains at the peak are nice, but the average increases were more impressive. At 5,000 rpm, the JPC intake produced 38 more rwhp, yet we saw a gain of 46 rwhp at 5,800 rpm. Generally speaking, the average power between 5,000 rpm and 6,500 rpm is where a Mustang operates on the dragstrip. "The gains will be seen on the dragstrip when the driver shifts and the rpm drops back to 5,000 rpm. An engine generally sees a 1,500-rpm drop (in engine speed) after the gear change," claimed Dez.