Project Aerio - Aerio Turbo Part II

The pump is an in-tank unit pumping out 190 LPH at a very high psi. With it installed, the car made 171.1 hp, but the key factor is the power was made at an air/fuel ratio of 11.5:1, according to our Motec PLM air/fuel ratio meter. This is generally a safer air/fuel mixture to run. Ideally we would try to run a 12.0:1 to 12.5:1 ratio, but in this particular situation we felt a much richer mixture would keep the engine cooler and lasting longer. Now it was time to bring the boost up, and for that we turned to our old friend, the A'PEXi AVC-R. Wiring the unit to the ECU requires finding the vehicle's ignition power, ground, injector signal and speed sensors. Once these are hooked up and the boost solenoid was connected we had plenty of boost control to regulate our engine at 7 psi. One of the handy options on the AVC-R is it translates injector pulse width to the injectors' duty percentage, and in doing so informs you if your injectors are maxed out. At 7 psi our car put out 188.8 hp to the wheels at 5700 rpm. But the strange part was the loss of power from 5700 to redline. If you examine the dyno graph from 4000 to 5700 there seems to be a little bit of a breakup throughout that section, then after 5700 the power just falls off completely. It's obvious if we could clean up this section we could easily break the 200-hp barrier, but it looked as if the breakup was due to a boost leak or boost controlling problem.

On the next pull we found our problem and it wasn't a boost issue. As the rpm started building up to 4000 rpm, the engine hit redline at a rate that signified a wheel spin or some type of clutch problem. We then tried sampling the next run in fourth rather than third gear, and we ended up with the exact same problem, but without the wheels breaking free; the clutch was toast. Remember, referring back to the first part of Project Aerio, our vehicle was one of the original test vehicles that ran at the track. That means brutal track abuse during what any other car would use as a break-in period. Since we blew the clutch out at 188.8 hp, that doesn't necessarily mean these results are typical for all Aerios running this kind of power.

A quick call to Suzuki landed us a brand new pressure plate, clutch disc and release bearing. Rather than install the new OEM parts right away, we decided to send them out to ACT to have it rework the OEM clutch assembly into a stronger one. ACT reported the O.E. clutch is capable of handling up to 161 hp. This means the clutch took a beating when we were at 171 hp, and the added boost was simply adding more fuel to the fire. In fact, ACT found the O.E. disc is capable of handling the extra horsepower, but the pressure plate was the weak link. The factory unit didn't have enough clamping force to withstand the power. ACT did discover a stiffer diaphragm for Nissan Sentras in its inventory, which was identical in size to the Aerio's. This means it replaced the SX diaphragm with an ACT unit, and the O.E. clutch disc remains intact. The newer diaphragm increased its working range and clamp load. While ACT does offer race discs, we were informed the stock disc is probably good up to 240 hp at the wheels. Once the clutch was installed we found the pedal would engage the pressure plate halfway up, instead of the O.E. unit grabbing at the end of the pedal's play.

Back on the dyno, we now know we shouldn't run into any type of problems whatsoever. On the very first dyno pull the Aerio put out 211.3 hp at 6200 rpm and a whopping 194.0 lb-ft of torque at 4900 rpm. We broke the 200-hp barrier! What was more amazing was this was done at exactly 7 psi of boost with an A/F ratio at 11.5:1 in the midrange and 11.3:1 in the higher rpm-perfect for safe street driving.

And we got these results without even tuning the S-AFC. We know for a fact that fine tuning the AFC will help out in the long run, and with the initial wiring complete all that's left to do is figure out which car select number to input in the unit. The AFC will eventually play a powerful tuning role in the Aerio, whether the car is normally aspirated or turbocharged. We just need a little more time to get the unit working with our Aerio.