1991 Nissan 240SX LE - Power Pages

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1991 Nissan 240SX LE - Power Pages

Installation: Steven RHIM OF G-Dimension
Dynamometer and testing: Robert Ting & Ultimate Tuning's dynojet dynamometer
Pros
Now, before you drop a line to mail@importtuner.com telling us how we're about five years too late on the whole drift craze, take another look at this month's Power Pages test pig; it's not a drifter, dragger, or a circuit car. It's a daily driver. When an automotive magazine editor who already holds titles to a JGTC Supra and an R33 Skyline GT-R needs to find a beater during his afore-mentioned rides' never-ending "downtime", a stock '92 Tercel just isn't an option. That's why our own Carter Jung chose to hit the bricks in style with this SR20DET-powered '91 240SX. The SR has proven its ability to endure repeated beatings on the track, which makes it the engine of choice to replace a street-driven 240's gas-guzzling KA; but can it be done so in a low-key, emissions-passing, stock-appearing fashion, while still making decent power? Retaining the stock side-mount intercooler, catalytic converter and 7psi wastegate, our test car will try to prove that it can.
Cons
No matter how closely we adhere to OEM specifications in retaining the SR's emissions compliance and stock componentry, the fact that it powers a USDM chassis makes the whole car illegal as per California's wonderfully open-minded CARB and Smog regulations. And since most referees can spot an SR conversion a mile away, some Californians may argue this test is a complete exercise in futility. But alas, Californians! Ours is not the only state in the country! SR swaps easily go unnoticed in states less hip to the game than Cali, and may be completely legal in others, provided they meet emissions regulations (something the SR can do easily). However, as much as we'd like to think tests like this might work to reverse backwards laws that prohibit the conversion to an engine a car was originally designed to use, they probably won't.
Notes
The car was taken to Robert Ting of Ultimate Tuning in the City of Industry, Calif., for installation and testing. G-Dimension's Steven Rhim made sure to check compression and ignition timing and give Carter's SR a full Mobil 1 synthetic oil change prior to establishing a baseline and installing any parts. Coming into testing, the SR had already been upgraded from stock in several ways; the OEM cast manifold was junked in favor of a less restrictive tubular one, and an aluminum Koyo radiator took the place of the original plastic and copper unit. SRs shipped to the states rarely include factory airboxes; this one had already added an A'PEXi power intake from the get-go. The SR does, however, retain factory power steering and air conditioning-two musts for a California daily driver. In this form, the 240 managed to transfer an average 152 whp and 150 lb-ft of torque, or about 74 percent of its claimed flywheel figures, to the roller of Ultimate Tuning's Dynojet dynamometer.
Pros
A'PEXi's N1 system started it all, and it continues to be a standard by which all others are measured. Born from endurance racing technology, the N1 design minimizes the number and degree of bends throughout the system-which means less restriction and more power. For the ExTi variant, A'PEXi replaces the conventional stainless muffler with a lightweight titanium one, which features a removable silencer and variable-length scorched tip. Our system bolted up perfectly to the cat and hangers and featured a drastically larger piping diameter than stock-crucial for forced induction. An integrated oval-shaped resonator managed to keep the exhaust note to a respectable level, while providing adequate ground clearance and maintaining a straight-through design.
Cons
With the exhaust installed, we noticed that part of the piping made contact with a seatbelt bolt protruding from the underside of the car. Asking around, we learned that this wasn't a problem other tuners were experiencing and attributed the miss-fit to the poorly manufactured, generic tubular manifold (Tip: Don't buy knock-off products!). The 240SX exhaust tract doesn't make use of spring-bolts or flex-pipe to compensate for imperfections, so proper construction of every component from the head back is crucial in maintaining proper fitment of all other parts.
Parts
Stainless steel mandrel bent piping with resonator; titanium muffler with silencer, tip and bracket, nuts, bolts, gaskets and stickers.
Tools
12mm ratchet, 12mm open-end wrench; impact wrench, breaker bar and/or WD-40 for loosening 200k-mile-old stock components.
Installation time
17 minutes with two people, a lift and no problems.
Notes
As suspected, replacing the wrinkled Pixy Stix-stock exhaust with the larger, straighter A'PEXi unit netted us some impressive gains. Power and torque fell slightly before 3,000 rpm, due to the reduction in back pressure, but the 5 to 17 whp we picked up above 4,500 rpm more than made up for it. Even without the optional silencer, the N1 ExTi's smooth tone was just perfect for the streets-not the least bit loud or offensive. Be sure to thoroughly soak the stock bolts with WD-40 before loosening them. Use of an impact gun is highly recommended, but you may run into the problem of nuts and bolts being too rusted to grip with any tool-an angle grinder or acetylene torch is the weapon of choice here. Just watch those fuel lines...
Pros
Power increases brought on by the addition of the downpipe seemed to mirror those of the exhaust; small gains of horsepower and torque low-end, followed by large gains in both from midrange to redline. Side-by-side comparison will show the increased size the A'PEXi downpipe offers over the ridiculously restrictive stock unit; it's no wonder large gains were made. Still especially impressive is that these gains were realized with the stock catalytic converter still in-line. The included bracket was easier to use than some; it's elongated mounting holes bolted to the factory chassis mount with adjustability to spare-perfect for use with jenky no-name manifolds.
Cons
It seems that A'PEXi has switched from machined flanges to cast ones, and areas where they were once robotically TIG-welded now appear to have been manually MIG-welded. But with the overall construction of the product just as solid as ever, it doesn't seem that A'PEXi is cutting corners where it counts; and you can't blame anyone for trying to save a couple bucks these days-And saving you a couple bucks in the end.
Parts
Downpipe, gaskets, bracket, nuts and bolts.
Tools
12mm socket with extension, 12mm open-end.
Installation time
5 minutes
Notes
We tested the downpipe after the addition of the exhaust to better show its contribution to increasing flow; had we installed it first, we suspect the restriction of the factory exhaust would have kept it from showing any power increases. Still, with the restriction of the factory catalyst present, we were surprised it made as much as it did. We would typically expect gains this large in cat-less race applications, where the downpipe and exhaust can reach their full potential.
Pros
It made power, installed in five minutes and looks good underhood. The A'PEXi Super Ground Stabilizer is universal to vehicles with electrical systems, meaning it can be easily transferred from one vehicle to another. And it's an all-inclusive product-there aren't any parts to lose in the shuffle. The included installation guide identifies grounding locations for popular platforms, and gives a good idea of where to fasten grounds in universal applications.
Cons
Negative reputation. It seems most people are slow to trust grounding systems in general, and we're sure we'll have to defend our reasons for adding the product to at least a few clowning skeptics every time the 240's hood is propped. Applying the kit to the SR20 engine required we attach one of the wires to the coil harness grounding point on the firewall side of the cylinder head-not the easiest place to access, especially on a hot engine. Nissan takes the heat for this "bad".
Parts
A'PEXi Super Ground Stabilizer (all inclusive)
Tools
10mm socket, 10mm open-end (Tools vary depending on application.)
Installation time
5 minutes.
Notes
Efficient electrical conductors (like wires used for engine grounding) are made of expensive copper, so, it goes without saying that OEMs will limit the application of ground wires from the factory to reduce production costs. Adding more grounds can often times be beneficial, but only when done correctly. Ground wires should be applied to stock locations as well as points where electrical noise might occur among sensors and other devices; DIY kits with more grounds or thicker wire than necessary won't result in more power. The A'PEXi kit includes just enough additional grounds at the right gauge to tame electrical noise and properly channel rogue currency back to the battery ground. It also offers an active voltage-stabilization control unit which further smoothes turbulent current with its electrical noise filter; something not found in DIY kits.
Conclusion
Replacing the downpipe and exhaust on our SR20DET-motivated 240SX reinforced a well-documented truth of import tuning; backpressure is the arch-nemesis of a turbocharged engine. Where the addition of a head-back exhaust system might normally free up to 10 whp in a similarly-powered n/a 2.0L application using a catalyst, the placement of turbo-back components netted a 28 whp improvement in our 7psi-limited instance. Allowing the turbo to boost higher would've shown even more power than could've been possible with the stock system. The addition of the Super Ground Stabilizer proved its worth on the dyno, giving a few additional ponies to disprove long-held claims of "snake-oil" that surround products like it. Most importantly, this month's testing shows the power production benefit of parts that should be added to street-going cars for other reasons: Swapping out restrictive stock exhaust components allows the engine to aspirate easier and the grounding kit frees the electrical system from performance-robbing interference; two modifications that ideally serve to increase overall efficiency, meaning greater fuel economy and longer engine life, as well as increased power production. Eliminating the only remaining source of backpressure in the system, the stock catalyst, would produce even more impressive results, but we wanted this test to show the benefits that can be obtained while adhering to popular emissions and noise regulations. While there's nothing we can do to change laws that restrict the use of certain engines in road-going vehicles, at least we're able to show there's no practical reason for their being.
CONCLUSION HP Level +HP TQ Level +TQ Baseline (with intake) 152.6 150.4 A'PEXi N1 ExTi Catback 169.3 16.7 162.1 11.7 A'PEXi GT Downpipe 179.6 10.3 169.2 7.1 A'PEXi Super Ground Stabilizer 180.7 1.1 170.1 0.9 Final 219.0 28.1 157.0 19.7
BANKROLL A'PEXi Power Intake (base) $130.00 A'PEXi N1 ExTi Catback $890.00 A'PEXi GT Downpipe $199.00 A'PEXi Super Ground Stabilizer $239.00 MSRP Total $1,458.00

Photo Gallery: 1991 Nissan 240SX LE Power Pages- Import Tuner Magazine

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