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We originally intended this install to take place alongside our bolt-On Shootout (July). Bruce Wayne at MagnaFlow had rushed over a muffler and resonator to barely beat our parts deadline, and the plan was to assemble a custom cat-back exhaust as the header went on. Unfortunately, this was curbed when we came up a hair short on the right size of tubing. Fortunately, MagnaFlow was just about to release a full cat-back system for Nissan's QR25DE 2.5L engine.
A few weeks later, a large, but well-packaged box containing one the first of these fine three piece systems arrived by courier from across the country right to my desk.
Once you get through the foam injected shipping dress-up, the shiny stainless steel muffler and resonator pieces come into view. Inside the package were three-prefabricated 2.25-inch pipe assemblies, including a resonator, mid-pipe and 5x8x14 inch muffler with elliptical tip, some hardware and a simple set of instructions.
Installing this bad boy is a straightforward affair and Nap Tiqui tackled it in under 30 minutes at TAG Racecraft. But before that action commenced, we put the Spec V back onto the Dyno jet 248 and discovered a new baseline of 156.9hp and 152 lbs./ft. of torque.
On the morning of the install, the car had been at the dealership for a scheduled 12,000-mile tune-up and 21-point inspection. 91-octane gasoline had been poured in the night before, so we felt it was important to establish a new baseline. With several hundred miles of driving with the previous modifications, the ECU had surely learned the new operating parameters by now.
We noticed a 5.5 percent increase in horsepower, but an unexpected 2.4 percent decrease in torque. There was also a clear drop off on both curves - torque had deviated from 2,700 to 5,350 rpm as can be seen in the New Baseline Dyno chart.
With a new baseline established, it was time to put the car up on the hoist and get rid of that nasty factory exhaust. See how huge that muffler is? The only thing free-flowing about it is its volume! In no time flat, the 2.25-inch MagnaFlow stainless steel cat-back exhaust was pieced together, hung, and the car lowered back down to earth. Before heading out on the road, however, it was back onto the dyno to see the improvements. And improvements there were!
After a three-month break-in period, the AEM cold air intake, Hotshot Tri-Y header and Unorthodox underdrive pulley had made an obvious difference, but a 3,000rpm gap had developed in the middle of both the power and torque curves. Thank goodness MagnaFlow stepped in when it did as this 2002 Sentra SE-R Spec V desperately needed that nagging condition to be cured. Horsepower and torque are up 7.7 percent and 6.4 percent respectively from the post Bolt-Ons dyno (June, pg.84). See the current Post-Mod Dyno chart.
Power is now delivered more consistently throughout the power band and there is no more bogging before the header punches in at 5,350rpm. Torque gets applied smoothly up to 166 lbs. /ft. @ 3,750rpm and the bumpy start from 2,000 to 2,700rpm is also flatter. Particularly straight is the horsepower line, and both power and torque curves are filled in quite nicely now. We're even more excited about the slight increases above 5,200rpm - you know, when your hair is on fire. See Dyno Comparison.
The resonator has a soothing effect while behind the wheel, but the sporadic reverberations from the system remind you that you're not at Sunday service. Regardless, this Spec V now has a cool, deep, classic, yet somewhat understated exhaust tone that's reminiscent of a 2.5L V6. It goes well with the header's higher pitched whine at the top end without being overly abrasive on the ears. No doubt, the resonator is functioning as intended. Overall, we're very impressed with the MagnaFlow cat-back exhaust.
This car never really had trouble passing slower-moving vehicles, but now it's a whole lot more fun. As for the clutch, it's turned out to be a lot better than the journalist originally reported and we're satisfied with how it is working, at least for now. Going from sixth to fourth gear on the highway instantly brings the engine to life thanks to better air and exhaust flow.
An ECU upgrade would be a great addition to this package. New wheels, tires, brakes and suspension will also help get this car up to 'Spec.' We may even have the chance to evaluate the performance of the aforementioned factory parts on a 2.5-mile international road course. If it happens, we'll gladly tell you how it went.
So far, the upgrade costs have been reasonable, but the next series of mods will have significantly higher price tags because there are four of everything. It's almost time to pull out the credit card.
Stay tuned to each and every issue of Modified because we're not sure when the next series will break. We're in the process of trying to book some track time, and hope that it pans out. Rest assured, we'll bring you more Spec V coverage as soon as we can.
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