We've been tempted to change the name of our Project Mazdaspeed Protege to "Project Perplexing." That's because it's always nearly impossible to know what'll happen when the wrenches start turning. Seemingly simple procedures often take gargantuan efforts, and once the car hits the rollers, the perplexing part continues. For example, mods that should lean out the air/fuel ratio do just the opposite. Case in point: iON Performance's Street Spec turbo-back exhaust system.
While it's true the ECU is moving to the forefront of tuning, bolt-ons can still make power. More precisely, diameter makes power. We figured we had a hit on our hands when we compared the piping of the 3-inch iON kit to the diminutive factory pieces we pulled from the Mazda. The OE S-pipe, or downpipe, seemed especially restrictive so we suspected (hoped) going into the installation that we were looking at more than the usual 4-6 hp.
The iON Performance Street Spec turbo-back exhaust system features stainless-steel construction, beefy flanges and well-designed sections that fit without complaint. The one-piece iON S-pipe fits perfectly and the system includes a high-flow cat and an O2 sensor bung to retain all emissions capability.
Turbo-back systems deliver big power, but you have to want it because installation of these systems can be very involved--exactly how involved depends on the application. Of course, the MSP was a problem child in this regard. Swapping systems involves draining and removing the radiator, dismantling most of the turbo system piping and removing the header/turbo assembly. Not a short order.
We had some excellent instructions from iON but discarded them immediately because we figured we could do the swap without lifting the radiator, etc. There were some wickedly placed bolts on the turbo, which were impossible to even get a wrench on, so we were forced to rescue the iON instruction sheet. All said, installation is about a four-hour affair. If you break for lunch, break for coffee, or break a head stud, allow more time (about an hour and five minutes for a head stud).
On the dyno, we continued to get mixed signals from the Mazdaspeed Protege. The power was there, but instead of leaning out the fuel curve, the situation got richer. At 4800 rpm the air/fuel ratio dove below the 10:1 level, never to be seen again. Still power went from a pre-exhaust baseline of 163.9 whp to 186.1 whp, a huge 22.2-whp gain and easily the biggest single improvement we've seen on the car.
Steady gains were realized from the time we hit the sample button to redline, and at 6700 rpm, the iON Performance system delivered a 31.1-whp kick in the pants. On the torque side, peak numbers improved from 163.1 to 175.6, a total improvement of 12.5 lb-ft. It should be noted that we observed the boost level rise to .5 bar and hold firmly for the entire run. Previously, the boost would hit .5 bar and fall off near the end of the run.
On the road the iON system is noticeably louder but by no means obtrusive. The power gains can be felt in the pants and the Protege is much more eager to spin the tires under abrupt throttle manipulation--when you floor it off the line or after a shift.
There's an overall feeling of authority under the loud pedal that wasn't there prior to the iON system installation. We're short on time with Project MSP so our next installment will be an A'PEXi AVC-R boost controller; maybe unleashing some extra pressure will shock our air/fuel ratio back into line. Stay tuned.
The iON Performance Street-spec turbo-back exhaust system is constructed from stainless steel and is 3 inches in diameter. Its mission statement is to eliminate restrictions in the OE system and increase exhaust flow. | 
When it comes to factory turbocharged cars, the power hides in the downpipe. The iON kit includes a one-piece, ceramic-coated downpipe, or S-pipe. | 
The Street Spec system includes a high-flow, 3-inch catalytic converter and bung for the engine's 02 sensor. |
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The main pipe is decidedly bigger in diameter. When it comes to performance exhaust systems, more diameter means more power, especially in turbo applications. | 
The iON muffler is a straight-through design that provides more gas flow but less noise muffling. This tradeoff is one of the classic compromises in engine performance. |
Comparing the cast, two-piece S-pipe to the one-piece, ceramic-coated iON piece, it's easy to see why there'd be big gains in swapping downpipes. | 
Installation requires removing the radiator, most of the turbo system piping and the entire turbo/header assembly. like we said, you gotta want it. |  |
Dyno 1: Baseline testing prior to installing the iON system revealed 163.9 whp. After installation, runs vividly illustrated that our efforts were worthy as the iON Street Spec turbo-back exhaust delivered the goods to the tune of 186.1 whp. That's a peak gain of 22.2 whp but the system showed big gains from the moment the sample button was pushed. | 
Dyno 2: On the torque side, the system showed a 12.5 lb-ft increase at the wheels. We were again perplexed by the engine's air/fuel-ratio readings. Despite a substantial gain in power, the ratio worsened, dropping off the graph (below 10:1) from 4800 rpm to the end of the pull. The silver lining? At least our injectors aren't maxed out. | 
Dyno 3: We positioned the cursor to illustrate the biggest gain. At 6700 rpm, the iON Performance system delivered a 31.1-whp kick in the pants. We also noticed the turbo rose to .5 bar and held its ground to the end of the pull. In the past, the boost needle would've peaked at .5 bar and slowly retreated to .4 bar by the end of the run. |