The trusty ol’ SR20DET in our S14 project car has proven to be quite the workhorse, requiring very little maintenance and repair over the past few years. That’s largely due to the fact that aside from bolt-ons and a tune, it’s pretty much stock. The 250 whp is pretty much at the limits of the stock turbo. An S14 with an SR making 300 to 350 whp has been proven to be an around ideal setup. It makes for a legitimately fast car without overpowering the chassis. By that, I mean when you get into the 400-plus-whp range, a lot of upgrades—and not just to the engine (think drivetrain, brakes, etc.)—are required to make it reliable and usable.
On the other hand, 300-plus whp on a setup such as ours is a turbo upgrade away.
Since this car is primarily used for the track, my motto is to keep it simple, so instead of going crazy with a new tubular exhaust manifold, downpipe, etc., I intended to use as many stock item parts as possible. My reasoning is reliability. The last SR-powered 240SX I built had everything done to it, a tubular manifold, built bottom end, etc., and it was nothing but a headache. The heat the manifold and turbo setup would produce would cook rubber tubes and brake lines and heat soak pretty much the entire engine bay. This led to frustrations and constant issues during lapping days.
This time around, I would do it the right way: stick with the stock manifold, retain the heat shielding, and build a capable setup around it.
Up until just recently, the Garrett 2871R turbo was the de facto upgrade for most SR20 owners looking for a stock frame turbo to deliver 300-plus whp. However, Garrett has just recently released the new GTX2863R turbo, which promises to deliver even quicker spool-up than the 2871R while producing just a hair less peak power. That’s largely due to the new forged and fully machined 11-blade compressor wheel and ball-bearing cartridge housing.
Since the stock SR manifold will be used, two T25-flange exhaust housing options exist: a 0.64 A/R that will provide quicker spool-up at the expense of some top end and the higher flowing yet less responsive 0.86 A/R.
The 0.64 A/R housing is almost the best choice in every aspect, unless you are drag racing. For drift, track, and everyday street use, stick with the 0.64 (assuming you’re on a stock SR block).
Both exhaust housings come internally gated from Garrett and currently, there are no other options. However, these housings, particularly the 0.64, can suffer from boost creep at higher rpm. The easiest, albeit more time-consuming, solution is to weld up the internal gate and install an external one.
An external wastegate bung will need to be welded to the stock manifold. When I originally did this, I was unaware that ATP Turbo manufacturers a T25-flanged exhaust housing with an external wastegate flange built into it. That may be the better option in this case. That’s not to say the external wastegate mounted on the exhaust manifold is a bad solution. It just requires a proper drill press to cut out the required hole. I had the experts at Centerline Motorsports take care of the job for me since I don’t have the adequate tools at home.
Mounting an external wastegate on the stock exhaust manifold requires some fab work—nothing the guys over at Centerline Motorsports couldn’t handle for us.
For wastegate choice, Turbosmart’s new Comp-Gate 40 was the winner since the 40mm wastegate’s compact design allows it to fit into tight engine bays (like this one) while still providing excellent flow and heat-handling capabilities.
Plumbing the exit port of the Turbosmart wastegate back into the exhaust tract meant fabricating a custom dump tube. After ordering up the necessary stainless steel piping from Vibrant Performance, some measurements were taken and cuts made. I decided to include a Vibrant bellows assembly to account for vibration and heat expansion in the piping, otherwise stress cracks can frequently occur.
The dump tube was welded into the Tomei Expreme 02 housing, which makes for a tight squeeze at the back of the engine bay. But after a test fit, the entire piece comes off and on without too much cursing and swearing.
The new GTX2863R doesn’t come with a factory-style two-bolt inlet compressor housing. Therefore, the HKS intake setup that was on the stock turbo had to go. Instead, using several leftover AEM intakes and my newly acquired aluminum welding skills, a 3-inch cold-air intake pipe emerged.
There was also the issue of mating the compressor-housing outlet to the factory SR intercooler piping. This is where Vibrant Performance’s vast array of fabrication parts comes in handy. After a quick search, I found just the piece I needed—a tight radius cast 90-degree aluminum elbow. My trusty Miller Diversion 180 TIG welder made life much easier (this was my second time welding aluminum), mating the elbow to the housing. Sometimes equipment does matter, especially when you’re a novice.
The advantage to using the stock manifold and Garrett T25 exhaust housing is that the factory heat shields can be reused. Therefore, underhood temperatures should be near and close to what they were with the stock turbo. The only added source of heat is the wastegate dump pipe. Vibrant Performance comes to the rescue once again with its Sheethot performed pipe shield. Built with six layers of dimpled aluminum, its shielding is able to withstand 1,100 degrees F and will keep any radiant heat from the dump tube at bay.
With the turbo upgrade complete, there was just one more item to address: installing a baffled oil catch can. The factory PCV tube from the valve cover runs to the air intake, and as the intake creates vacuum, it ventilates crankcase pressure from the valve cover. The by-product is oil vapor that’s constantly drawn into the intake, and over time it deposits a film of oil inside your intercooler and piping and your engine ingests it. To combat this issue, a baffled oil catch can, like the one from Mishimoto, traps oil particles with its 40-micron bronze filter. The result is crankcase air free of oil and a cleaner, better-running engine.
And that’s where this story wraps up—but it’s far from over. A set of Kelford camshafts, 740cc HKS injectors, and even a race battery are on the list of necessary upgrades before a tune can tie it all together and make some serious power out of this setup.