Melbourne tuning specialist APS (Air Power Systems) has recently unveiled 3 power-up kits to suit S14 and S15 Nissan 200SXs. Here we'll focus on the 'entry level' JR1 Spec upgrade...
The JR1 Spec kit comprises three main components - a replacement exhaust, an additional high-flow intake duct and a UniChip (an interceptor module that allows adjustment of fuel, ignition and boost). The recommended fitted price is AUS$3650 (plus freight).
To check the merits of the JR1 Spec kit, we went along to Adelaide's Turbo Tune workshop to oversee installation and perform step-by-step power runs on a new S15...
Baseline Power
The first step was to establish a repeatable baseline power figure, using Turbo Tune's Dyno Dynamics chassis dyno.
The standard power curve - plotted in green hereon- shows a peak figure of 111kW at the wheels. Note, however, our demo car had travelled only 850 kilometres. Typical to all standard 200SXs, its power curve is very progressive - indicative of a flat torque curve.
The lower section of the graph reveals air-fuel mixtures. The standard vehicle runs as lean as 11.5:1 under maximum load, and then dips off the scale at higher rpm - Turbo Tune's Autronic air-fuel ratio meter is unable to measure mixtures richer than 10.0:1.
Standard boost pressure varies between 7.6 and 9 psi across the rev range - peak boost arrives in the upper mid-range. (Detailed 'before' and 'after' boost curves can be viewed at the end of the story.)
Exhaust - Standard
The S15's standard exhaust system is extremely restrictive.
Starting behind the turbo, the cast iron dump pipe has internal lumps and bumps and its outlet ID is a quite small at 57mm.
Next comes the front section of steel pipe, which measures 54mm ID at the front and only 45mm ID at the rear. Like every other section of standard system, this pipe is heavily press bent.
The standard catalytic converter bolts to the back of this pipe, and - interestingly - it has a much larger 66mm ID inlet and outlet. Flowing on from the cat is the intermediate pipe, which - again - closes down to 45mm ID all the way along its length. A centre resonator is integrated into the intermediate pipe.
Once past the axle, gasses flow into a bend and - finally - the Calsonic rear muffler. The right-angle bent pipe leading into the muffler is 45mm ID and the box has twin 42mm ID outlets.
Exhaust - APS
The APS replacement exhaust is very similar to that used in the MY01 WRX power-up we covered previously - it's made from 304-grade stainless steel piping, with reinforced brackets used throughout. Finish is exceptional, and - unlike the MY01 system that we saw - the polished mufflers arrived with absolutely no dents.
APS's cast iron 'high flow turbo discharge housing' immediately looks less restrictive than the standard item - it matches the turbine flange perfectly, flows into a smoothly contoured elbow and exits through a larger 74mm ID outlet. A stainless steel under-bonnet heat shield is mounted to its body.
The front section of stainless pipe maintains that 74mm ID all the way through, and it has a much smoother radius bend than the factory part. Bolting to its rear is the APS cat converter - a 74mm unit. The intermediate pipe continues the 74mm ID, and a straight-through offset centre resonator fills the space of the original. Another slim-line 'hotdog' style resonator is found prior to the pipe reaching under the axle.
Unlike the APS MY01 exhaust - where pipe diameter tapers towards the rear - the S15 system maintains its full 74mm ID all the way to the exit of the rear muffler. Again, this is a straight-through design, but its outlet is only around 65mm ID. The polished oval tip is relatively over-sized and restriction-free.
Dyno Time - Exhaust Only
With the intake duct and UniChip yet to be fitted, we tested the effects of the APS replacement exhaust on its own.
This graph shows the improvement, plotted in blue. Note there's a gain all the way through the rev range - a minimum of 10 percent down low, up to around 16 percent toward the top-end. Peak power at the wheels is now around 125kW, up from 111kW.
As evident on the lower half of the graph, the big exhaust created air-fuel ratios leaner than standard. We saw a leanest figure of 12.3:1, running to about 10.2:1 through the top half of the rev range (compared to a leanest 11.5, moving beyond 10.0:1 in standard form). These are still quite safe.
Boost rose considerably. Manifold pressure now ranged between 8.5 and 10.8 psi across the rev range, compared to 7.6 and 9 psi - both configurations peaked in the upper mid-range. (As mentioned, you can jump to the last page to see the boost curves.)
The APS exhaust system has an appealing, subdued note that's given its diameter, is remarkably quiet. It meets the EPA's 90dB regulation and APS claim it's completely drone-free.
Intake - Standard
Like the exhaust, the S15's standard air intake system is also quite restrictive.
The factory intake begins with an over-the-radiator snorkel leading down into the airbox. The feedhole into the airbox is around 102mm x 43 mm, giving a cross-section of approximately 44 sq cm. The S15 airbox is quite angular, the filter insert looks around the same size as found in a VL - VS Commodore and an airflow meter is fitted further along.
Intake - APS
Interestingly, the APS JR1 Spec kit maintains all of the factory intake hardware. Extra flow comes from the addition of a second high-flow duct that picks up air from the inner guard and delivers it through the side of the airbox.
The APS duct looks simple enough, but it's quite a complex shape. The triangular end - which matches the side of the airbox - flows beautifully into an oval shaped pick-up. The triangular end has a 40 sq cm area, while the oval end is nearly double that.
Installation is not completely straightforward.
To make space for the new duct, the original radiator over-flow bottle is discarded and the supplied replacement is mounted on the inside of the right-hand guard. A new length of hose is supplied to plumb the radiator filler cap to the bottle.
Then, the airbox itself needs to be removed from the vehicle and a hole is made in its lower half. As you can see, the side of the lower half of airbox is triangular - hence the triangle end of the new duct. Once the hole is cleaned of dags, a series of small mounting holes are drilled through the box and the new duct is bolted into place. The airbox assembly is then reinstalled.
Dyno Time - Exhaust and Intake Only
With the APS intake duct fitted - in addition to the exhaust - our S15 made some runs with its untouched standard management system.
As you can see from the pink plot, adding the APS intake duct yielded nothing at low rpm but up to around 6 percent in the top-end. The standard intake snorkel to the airbox was obviously holding back airflow at high rpm and load. Peak power rose to 132kW at the wheels, up from 125kW previously.
Mixtures weren't dramatically affected. The pink plot on the lower section of the graph shows a leanest mixture of 12.6:1, enriching to around 10.4:1 through the top-end (these figures were previously 12.3 and 10.2).
Again, there was an increase in turbo boost. Pressure now ranged from 8.5 to 11.6 psi across the revs, compared to between 8.5 and 10.8 psi - again, both sets of figures peaked in the upper mid-range.
The extra induction noise from the APS duct was barely detectable - if at all.
UniChip
The final piece to the JR1 Spec kit is the fitment of a UniChip.
The UniChip is a programmable interceptor module that adjusts fuel, ignition and boost parameters. It intercepts the input and/or output signals of the factory ECU, altering them to deliver the desired fuel, ignition and boost behaviour.
One of the biggest attractions of an interceptor module is it retains 100 percent factory ECU functionality. It continues to deliver factory quality cold starts, air temperature compensation, knock sensing and - amongst other things - closed-loop mixture control under light-load cruise. On the other hand, an interceptor such as the Unichip cannot make an effective fuel changes during light-load closed loop operation (where the ECU self-corrects using the input of an oxygen sensor).
In this application, however - where only high-load alterations are needed - that's irrelevant.
APS provides two separate modules - the UniChip A and UniChip X.
UniChip A is responsible for altering fuel and ignition timing, while UniChip X - the smaller module - is used to control boost pressure only. Because both units arrive pre-programmed by APS, connection into the standard wiring loom is all that's needed.
In addition, a small restrictor is inserted into one of the wastegate hoses - the one feeding boost pressure to the control solenoid. This restriction helps deliver the desired boost changes.
Note that - despite this aftermarket management device - the JR2 Spec kit is claimed to carry ADR 37/01 emissions approval.
Dyno Time - The Full JR1 Spec Kit (Exhaust, Intake and UniChip)
With the complete JR1 Spec kit installed, we put the S15 through its paces for the last time.
Having adjusted fuel, ignition and boost via the UniChip, this graph shows the massive improvement. Our new red plot shows a huge gain all the way through the rev range - between about 15 and 24 percent. The final power tally is a tad over 147kW at the wheels, up from 132kW using standard management but with the intake and exhaust modifications.
Interestingly, mixtures aren't that much different at lower revs. The leanest mixture now touches 12.9:1 (previously 12.6), running to a richest of 10.7:1 in the top-end (previously 10.4). From an engine durability point of view, these new pre-programmed mixtures are still quite conservative.
Note that ignition timing is also adjusted via the UniChip, but these figures are unavailable.
Certainly, much of the UniChip's power and torque gain comes from a substantial increase in boost. Manifold pressure is now more consistent across the rev-range - there's around 14.7 psi through low rpm, tapering to a minimum of 13.3 psi in the top-end. This is in contrast to the previous run, where we saw a minimum of 8.5 psi at low rpm, and an 11.6 psi peak in the upper mid-range.
Summary
The APS JR1 Spec kit highlights how easy it is to extract more power from the S15's SR20DET engine (the S14 version apparently responds very similarly).
With just an exhaust, intake duct and management upgrade (giving, among other things, increased boost), we saw rear wheel kilowatts leap from 111 to 147 - a gain of 32 percent. Torque throughout the rev-range is also massively improved.
At a cost of $3650 - installed - the JR1 Spec kit represents pretty good value.
There is, however, a much cheaper way of attaining a similar top-end power increase.
Unlike the Subaru WRX MY01 (which runs bulk rich when tampered with), the S14 and S15 200SX doesn't need expensive management changes to unlock large gains. There's nothing stopping you from bolting on 'your own' exhaust, intake and whacking on a boost control system for up to around 15 psi; this will give nearly the same peak power as the APS JR1 Spec kit. There's no question about this fact - in past articles we've already shown the dyno graphs that prove it.
To our way of thinking, however, the extra cost of the APS kit can be justified when you consider more than just maximum power.
For starters, the inclusion of the management upgrade - the UniChip - allows for improved throttle response and a greater spread of torque throughout the rev-range.
The APS exhaust is also a major drawcard. Unlike a custom exhaust, you can rest easy knowing the tried-and-tested APS system has no resonances, it won't clunk against the body while cornering hard and - most importantly - it complies with the EPA's 90dB limit. Made from high-grade stainless steel, it will probably offer better-than-average durability as well.
Furthermore, the kit's ADR 37/01 emission compliance should not be overlooked. Again - for personal piece of mind - you'll appreciate knowing there's no way of being busted for excess smog; you won't have to stress every time a police officer looks your way.
We also liked the lack of induction noise compared to an aftermarket pod filter.
It's these factors that make the APS JR1 Spec kit the most 'complete' 200SX power-up on the market. If you want 'only' a 30-ish percent power increase for your S14 or S15, this is the ultimate package.
Footnote:
For those people interested in the next power level, the JR2 Spec kit adds a big front-mount intercooler and water spray into the equation. The JR3 Spec kit - the ultimate APS development - involves different injectors, a larger turbo and a high-flow airflow meter. This set-up is good for a claimed 280kW at the flywheel; getting that amount of grunt to the ground is the problem...
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The Boost Factor
Interestingly, every incremental step in the APS JR1 Spec kit gave a boost pressure change all on its own.
Without deliberately attempting to increase boost, we'd already seen maximum boost rise from 9 psi to 11.6 psi before the UniChip came along and created the desired boost curve. These plots illustrate the boost curves in standard form (green), with the exhaust (blue), with the intake (pink) and - finally - with the UniChip (red). Note the strange 'lump' in the curves in the upper mid-range prior to the UniChip. As you can see, it's important to measure boost pressure when you're making other - seemingly non-related - mods. Contacts:Turbo Tune
+61 8 8297 1030 Air Power Systems
+61 3 9720 9170 http://www.airpowersystems.com.au/
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