Instead of finding another RX-7 for testing, we proceeded with the work. Pete "Fei Low" has worked on hundreds of RX-7s, and is capable of performing the modification with his eyes closed. He removed the upper intake manifold and started replacing the factory rubber hoses with silicone hoses. When we asked why not use regular rubber hoses, he pointed out that the silicone hoses are more durable than the rubber hoses and are less likely to get hard and brittle.
He was also quick to note that any performance enthusiast planning to increase the boost pressure on the Mazda needs to have this modification done. Without the modification, the hoses can easily break off or be blown apart under boost. Besides replacing the lines with silicone units, Pete also added a touch of super glue to further secure the line onto the intended portal to prevent any possible blow-offs at higher boost levels.
With the Mazda all buttoned up, we took it for a quick spin around the corner and noticed an immediate improvement. The "7" pulled from 3000 rpm all the way to redline with no hesitation. It was once again strapped to the dyno and pounded the rollers at a healthy 230.5 hp to the wheels. We gained an additional 29.1 hp to the wheels. Although the modification for the vacuum hoses is not cheap, we were thoroughly content with the performance gains. The gains definitely outweighed the cost of the modifications on the RX-7. So if you think your RX-7 is not performing like it did back in the day, we recommend having the vacuum lines checked.
The first performance mod to be added to the Mazda was the A'PEXi Power Intake. The intake system comes with all the necessary hardware for an easy, bolt-in affair and replaces the factory air box. The modification only took us 15 minutes with a few simple hand tools. Since the Mazda was still strapped on the dyno, we immediately went back to testing and the rotary roared to 238.5 hp and 215.4 lb-ft of torque. The improved airflow to the turbo increased performance by 8 hp and 12.3 lb-ft of torque. Happy with the gains, we ventured on.
After letting the factory exhaust system cool down to working temperatures, we went to work. We sprayed WD-40 on the nuts and hangers for easy removal and installation. Removal of the exhaust system only requires taking off two 17mm nuts and three rubber hangers. With the stock system off, the new A'PEXi N1 system was bolted in place. The Mazda was fired back to life and growled with each blip of the throttle. With its new sounding exhaust tone, the '7 was back on the dyno. This time, the rotary spun the wheels to the tune of 242.6 hp and 233.9 lb-ft of torque, an improvement of 4.1 hp and 18.5 lb-ft.
ConclusionEvery enthusiast wants to make more power, but before you start adding performance goodies to your vehicle make sure it's running in top condition. Our RX-7 made its largest gains without any performance modifications. We only performed what was necessary to make it run like it did from the factory. We can't emphasize the importance of general maintenance. So before you start doling out the cash for parts, make sure your ride is running in top form.
The FactsEngine Tested: 13B-REW
Application: 1993-96 Mazda RX-7 TurboCommon Swaps: Datsun 510, Mazda
R-100, RX-2, RX-3, RX-4, 1976-'91 RX-7Replacements: 20B Three Rotor