The Clutchmasters single-mass flywheel eliminates the rubber harmonic damper used to reduce NVH in the stock steel flywheel. By using a sprung disk design, the Clutchmasters hardware offers a much more precise engagement. The new aluminum flywheel weighs 13 pounds compared to the stock 24.25 pounds.
The PTE kit included new plumbing intended for the stock MAF meter to be mounted after the turbo, just upstream of the throttle body, so the air that's measured going into the engine is already pressurized. It's a rare and obtuse method of laying out a critical engine management sensor, and is often prone to aerodynamic turbulence, flow reversal and signal noise issues (something we also see in our Project MR2 Spyder, which is prone to random detonation, even after multiple re-tunes).
The noise and metering error in the original mounting probably caused the engine to go lean repeatedly and just beat the stock pistons into a pulp. Advocates of this type of sensor mounting cite the advantages of metering response and accuracy, as well as eliminating the need for a recirculating BOV. Ultimately, which way is better depends on the MAF meter itself, its mounting location, the distance from the intake or turbo, the throttle plate and the overall geometry of the charge piping.
From what we've seen, most turbo kits seem to prefer mounting the MAF on the suction side instead of the boost side. Using a blow-through meter on the boost side is only an option when there are mounting constraints, like not having enough laminar flow length between the air filter and turbo to get a clean signal, or when the factory MAF sensor harness isn't long enough.
We had FocusSport relocate our MAF sensor from the boosted side to the suction side. This puts the airflow meter at the bottom of the car on the exposed tubing with no undertray to protect it. This could be one reason why PTE made its kit a blow-through-type design. Notice there's plenty of length between the MAF sensor, the turbo and the filter element.
Our original PTE kit has the air filter coming right off the compressor inlet, which is mounted low, in front of the engine, almost at the level of the oil pan. This places the intake tube and the newly relocated MAF sensor low in the body with no undertray to protect it from debris. Not the best thing, but far better than popping another block. An aluminum plate was welded over where the MAF sensor originally sat and now houses the independent stock intake air temperature (IAT) sensor.
Tuning
We started the 500-mile break-in for the new engine and clutch while still on the original tune the car blew up with. We learned from our past mistake and kept out of the boost, since we had no idea how far off the calibration was with the relocated MAF meter.
With 500 miles covered and a fresh oil change, we sent the car back to FocusSport for a retune using the original SCT tuning software. In theory, the new bottom end should be capable of serious power on account of the forged internals and lower compression. But there are plenty of other limitations to the 2.0 SVT Zetec engine that kept us below our target of 300 wheel-hp. For starters, 300 wheel-hp is a lot of power to put through 225-width street tires, even with the Quaife limited-slip differential. Keeping the front tires from lighting up and torque-steering all over the place would be an issue.
Even with a proper tune, we would actually be making less power than the stock engine because the lower-compression pistons would have lower peak combustion cylinder pressures, resulting in a less powerful combustion stroke. The point of low compression is to reduce the knock threshold so more air can be shoved in at higher boost levels. Since boost was still at the stock 10psi (as regulated by the internal wastegate) we would need a simple manual boost controller to increase boost and move more air.
The original mounting location for the MAF on the PTE kit was welded up with a patch of aluminum, then drilled and tapped for the stock IAT sensor. IAT mounting location is critical--the ECU is calibrated to where the sensor was mounted as stock. This shouldn't be an issue for us since we can recalibrate the atmospheric correction curves with our SCT software to match this new mounting position.
We installed a Turbosmart Boost Tee manual boost controller in line with the stock wastegate diaphragm. The unit is just a needle bypass valve limiting the amount of pressure going to the wastegate so it opens later, allowing the turbo to generate more boost. Setting the boost is a matter of experimentation with a pressure gauge temporarily plumbed in-line to check boost pressures as the car was tuned on FocusSport's Dynojet dyno. The Boost Tee also comes with a nice set-screw feature to prevent tampering after setting the boost level.
More boost comes with a series of other problems, especially on the SVT engine. To measure the additional air properly, the MAF meter has to be able to read the amount of air being ingested. At 10psi, the MAF meter was already pegged out at its highest output of five volts. While the limitation isn't because of flow restriction from the MAF meter orifice diameter, the signal sent out from the sensor and read by the ECU would just read a constant five volts, even if airflow continued to increase. The ECU only sees that the flow limit is exceeded and trips into a fault mode, not knowing that there is still more air going into the engine. It will continue to deliver the same amount of fuel until the mixture goes lean enough to cause detonation and melts the pistons again.