TurboXS Front-Mounted Intercooler, J-Pipe, and More

After a long period of no modifications, we made a few more changes to the WRX in the fall. A TurboXS front-mounted intercooler lays the groundwork for future power increases. A TurboXS J-pipe frees up exhaust flow. On the outside of the car, we installed some STI-style mirror turn signals, and an F1-style rear brake lamp.

In many ways, the front of the car is the best possible location for the intercooler. It gets 100% cold, fresh air blasted directly onto it, so cooling efficiency is maximized. The air doesn't have to flow through any scoops or ducts and doesn't have to turn any corners.

With the older STI turbo layout, the plumbing runs for a front-mounted intercooler (FMIC) were pretty long, but on the 2015+ WRX the turbo is right at the front of the car, so the air piping isn't much longer than for the stock top-mounted intercooler. (It would be shorter if we flipped the intake manifold around so the throttle body faced forward, but that's a discussion for another time.)

The TurboXS front-mounted intercooler kit comes complete with a replacement bumper reinforcement beam/intercooler bracket structure, hard intercooler plumbing and silicone couplers to connect them all. The huge intercooler core is almost three times as large as the stock TMIC core.

See the picture of the TurboXS FMIC kit at right -- the factory intercooler core is on the left side of the photo. Note the tubular-structure replacement bumper beam, which also incorporates a tow hook/license plate mount receptacle.

Installation of the FMIC kit was not  as complicated as we feared. We did trim some of the front bumper cover to get everything to fit, but it wasn't as much as we feared, and the intercooler core sits quite nicely and discreetly behind the stock lower radiator grille opening.

To help out on the intake side, we added a Perrin silicone turbo inlet. This part replaces a problematic stock inlet made of plastic. The stock item can crack and leak, so it makes sense to replace it while we're working in that area. The Perrin item is much smoother for higher flow, plus the reinforced silicone rubber construction should hold up for a long time.

At the same time we upgraded the intercooler and the turbo inlet, we swapped in a TurboXS catted J-pipe. The J-pipe is the first exhaust component after the turbocharger, and the aftermarket version from TurboXS has larger 3" diameter plumbing, plus a high-flow catalytic converter to increase flow and power potential. In addition to the bigger diameter and higher flow, the new pipe is all fully-polished stainless steel, so it looks great.

After the new mods we put the car back on the dyno for some more custom tuning. It did much better, at 292 awhp and 281 ft-lbs to the wheels, but that was not as much as we were hoping for, and not as much as some similarly-modified customer cars that we have run on our dyno.

If this was the last stop on our modification journey, we would pull everything apart and investigate why the car wasn't making as much power as we expected, but instead we decided to push ahead to the next phase on this car. Stay tuned for more of those plans in our next post.

On the outside of the car, we installed some STI-style turn signals into the mirrors. The Subaru WRX STI comes with mirror turn signals and standard, but we installed some aftermarket items instead, for some extra pizzazz. Ours feature sequential turn-signal action, plus a white running lamp for when they are not in turn signal mode, and we think they look great. They do require a little extra wiring, because the WRX does not have factory mirror turn signals at all. Our kit includes everything you need, including OEM STI mirror caps with notches in them for the lamps. We wrapped our new mirror caps in black vinyl to match some of the black badging we've been installing around the car.

Finally, on the back of the car there is a little rectangle that looks like it should hold a lamp, but at least here in the U.S., it just has a blank piece of plastic. We fixed that by installing an F1-style brake lamp in that spot. We tied the lamp into the existing brake wiring, so everytime we hit the brakes, the center low-mounted stop lamp comes on. It even blinks when it first turns on, just like the F1 cars.

The lamp comes in a red version, which is what we chose, or a smoke version that is a little more discreet when it's not on.







Products mentioned in this blog post:

• TurboXS 2015+ WRX Front-Mounted Intercooler Kit
• TurboXS Catted J-Pipe
• Perrin Turbo Inlet
• Sequential Mirror Turn Signal Lamps
• F1-Style Rear Brake Lamp

Summer 2018 Update: Racecomp Coilovers, 19" Rota Wheels, and More

The Mach V WRX has been busy over the last half year or so, doing lots of parts delivery to our track-side store at Summit Point Raceway, plus other errands and general-use duty. We've done a good number of parts changes during that time, too.

On the cosmetic side, we did a set of JDM WRX S4-style fog lamp bezels, and some LED front turn signal indicators. The bezels maybe require a little bit of explanation. In Japan, the WRX S4 model has special front daytime running lights (DRLs) that are integrated into the fog lamp bezels. The original-equipment Subaru parts are very expensive, so we sell an aftermarket equivalent version. Actually, we sell two versions. One lights up white, just like the original JDM item; the other also switches to amber to act as a turn signal. That "switchback" model is the one we installed on our car.

The LED turn signals come in clear, smoke, or black color schemes; we chose black. They are a plug-and-play item, so installation was easy. There's an additional resistor you can clip on if you need to, to prevent super-fast flashing caused by the LEDs lower resistance, but we already have an LED-specific blinker module, so we didn't need to do that.

On the back and sides of the car, we removed the OEM chrome badging and switched to black badges. That's a pretty simple modification -- the new trunk badges just peel-and-stick to install -- but our technician did use a bunch of painters tape to line up and make sure the new badges were in the same position and were level.

The side badges attach to the plastic fender trim panels, which remove using a couple of bolts. We chose some blue STi-logo black badges for that. Yeah, the car is not an STi, but the blue matched our (custom powder-coated) STi Brembo brake calipers, and we didn't have any WRX-logo badges in stock at the time.

We changed up the wheels and suspension yet again. On the suspension front, we installed Racecomp Engineering Trophy Cup coilovers. These are an adjustable-height coilover with an excellent fixed-rate Bilstein damper. We ended up with a ride height about 2" lower than stock. The coilovers gave a ride that's a little more comfortable than the OEM STI suspension we had on the car previously, but the lower ride height and center of gravity give an amazing improvement in cornering ability.

The latest wheels are a 19x9.5" Rota KB-R. With a relatively conservative +40 offset, these wheels clear all STi Brembo brakes, and we think they look terrific. The weight is pretty good, too, at 21.25 pounds. (By way of comparison, Subaru's own factory STI 19x8.5" wheels weighs 28 pounds.) We had hoped that our 265/30R19 tires would fit without rubbing, but they JUST skim the fenders under full compression. We rolled the fenders just a bit, and so far the tire scuffing is minimal, so we can live with it.

Products mentioned in this post:

• JDM WRX S4-style fog lamp bezels
• LED front turn signal indicators
• Black fender badges
• Black trunk badges
• Racecomp Engineering coilovers
• Rota KB-R 19x9.5" wheels

Edit: I forgot to publish this post back in summer 2018, so here it is March 2019 and I've finally posted it.

Interior Enhancements; Getting Back to the Track

Interior Enhancements

We did a couple of interesting upgrades to the interior of our WRX over the summer, including a new carbon fiber/leather contoured steering wheel, and a inside-trunk pull handle, plus we tried on another new shift knob. We also installed some new shocks, and got the car back out to the race track in the fall.

We've always coveted some of the fancy Japanese contoured steering wheels, but they are hard to get and very expensive. We finally found a supplier that we liked, with a good quality product at a price point that seemed more reasonable. The wheel has a thicker rim compared to the stock item, and there are shaped portions that fit your thumbs and fingers. The top and bottom are finished in carbon fiber, and the 3-and-9 positions are in leather, perforated for ventilation. The frame is cast aluminum, just like the stock steering wheel.

The wheel installs just like a stock one; we carefully transferred over the stock airbag and spoke covers from our stock wheel. The clock spring, steering angle sensor, and airbag module are delicate and easy to damage, so if you choose to do this upgrade, have a trained mechanic install this part.

We really like the new wheel in the car. The fat rim is easy to grip and feels good. The indentations promote a good proper hand position on the wheel, and they feel comfortable. Plus the new wheel looks great. Several people asked us if it was a factory item.

The integration with the stock steering wheel controls and airbag is seamless. You can't really tell which part is aftermarket and which is original, which is the way we like it.

One tiny annoyance on the 2015+ WRX and STI is the lack of any handle to pull the trunk lid down. Many modern cars have a handle you can grab from the inside to close the trunk. We developed a Mach V trunk handle strap that you can attach to the inside of the trunk lid. This prevents you from getting your hand dirty on the soot and grit that sticks to the back of the trunk, plus you don't have to worry about scratching up the rear of your trunk lid. You can install our trunk pull strap on either the left or right side of the trunk lid; if you install it on the right, as we did, you just have to drill a single hole in the trunk liner. Otherwise, there is no cutting or drilling of the metal trunk. It's a small thing, but it makes us happy.

One last interior modification was to try out another new Raceseng shift knob. This one is called Raceseng Slammology. The -Ology shift knobs are all modular, so you can swap out the Delrin covers to mix and match colors or shapes. The Slammology knob features a full rounded Delrin top. We really like the feel of Delrin in the hand -- it's soft and doesn't get too hot or cold. Plus we love the look -- the smooth Delrin contrasts nicely with the finely-machined stainless steel
peeking out at the bottom of the shift knob.

More Suspension Changes

We had a customer with a 2016 WRX STI that found the stock suspension a little too uncomfortable. We ended up swapping shocks with him, so our WRX got STI shocks. The rear shocks are pretty similar in construction, but the front STI shocks are a fancier inverted monotube design.

The ride with the STI struts is a little bit more nervous in daily use, and you feel small undulations in the road surface more than with the WRX struts. This is something we have experienced before driving the STI, and the struts seem to be a big part of the difference in feel between WRX and STI. But the faster the car goes, the better the STI struts seem to work. At high speeds, even over bumpy surfaces, the STI struts show outstanding road-holding.

Track Testing

We haven't been out to the track with the WRX in a couple of years. The last time out, the car was on stock WRX struts, stock sway bars, our Mach V lowering springs, and Hankook Ventus Evo V12 tires. This time, we had STI struts, the same Mach V springs, our Mach V 22mm rear sway bar, and a set of 265/35R18 Continental ExtremeContact Sport tires on our Mach V Wicked Awesome 18x9.5" wheels. One more difference was that although we were at the same track -- Summit Point Main circuit -- the track was just repaved, so we had brand new fresh tarmac.

Photo by Finish Line Productions

The car performed great. Grip was excellent, with higher cornering speeds at any given part of the track. Chalk that up to the tires. The Continental ExtremeContact Sport offers excellent dry grip, and the grip stayed good as the track sessions went on.

With our Mach V lowering springs (yes, the Mach V springs work and fit perfectly well with the STI struts), our 22mm rear sway bar, and the STI struts, the car felt very neutral. It turned in promptly, with only the slightest hint of understeer on high-speed corner entry. On power exiting corners, the back end would step out just slightly. The whole car felt very planted and easy to control, with no unexpected behavior.

One other modification we made prior to track day was to install some DBA XP650 brake pads. These are a brand new product from DBA. The XP650 compound is specifically recommended for track day use. As promised, the pads held up great, with no fade even after 30-minute track sessions. they worked just fine cold, too, which is unlike some track-oriented pads. On the way to and from the track, they behaved just fine and stopped without squealing or creaking.

The only downside to using these as a street pad is the dust. They put out clouds of black dust. Even on the way to the track, the wheels developed a thin film of brake dust, and after a couple of track sessions there was a distinct plume of black dust down the sides of the car and coating the back bumper. That's par for the course for track brake pads.

We haven't yet decided to stock the DBA pads, but we may offer them in the future. Stay tuned.

Products mentioned in this blog post:

• Carbon fiber/leather steering wheel
• Mach V trunk handle pull strap
• Raceseng Slammology shift knob
• Mach V lowering springs
• Mach V rear sway bar
• Mach V Wicked Awesome wheels
• DBA XP650 brake pads

Changing Shoes and Improving Cornering

My WRX has been a faithful companion over the last year or so, just trundling around, carry people and parts, hauling me to and from our track store and our main office, and I haven't had much to report. It's been reliable and trouble-free, and getting around 30 mpg. I have swapped on a couple different sets of wheels, though, plus I added a new Mach V rear sway bar.

One of my all-time favorite wheels is the TWS Motorsport T66-F. TWS is a Japanese company that makes forged wheels -- it's one of only three companies in Japan that does. I actually went to the TWS manufacturing facility in Toyama, Japan, last summer. Forging aluminum results in a lighter, stronger wheel compared to traditional casting. The 18x9.5" T66-F is incredibly light -- more than six pounds lighter than the stock 17" wheel that came on my WRX, even though the TWS wheel is 1" larger in diameter and 1.5" wider! Of course they clear STi Brembo brakes, which is important since our WRX has been retrofitted with them.

I paired a set of 18x9.5" T66-F wheels in Gunmetal color with a set of 265/35R18 Michelin Pilot Super Sport tires. The Pilot Super Sport is one of my all-time favorite street tires, and combined with the super-light TWS wheels the car felt like it had limitless grip and a feeling of being light on its feet. Plus, the wheels looked amazing! We got tons of positive feedback about the way the car looked with this wheel set on it.

I would have kept those wheels on the car forever, but a customer took a liking to them and the TWS wheels went out the door. It was getting to be winter, so I swapped on a set of our own Mach V Awesome wheels, which are 17x9". For tires I chose Dunlop SP Winter Sport 3D, sized 245/45R17. The ride was suddenly quite plush, what with the additional 1/2" of tire sidewall, plus the softer winter tire. But unlike some of the previous winter compound tires I have run, the SP Winter Sport 3D was no slouch in terms of dry traction. I even drove in a winter autocross on them. (The Summit Point Refrigerator Bowl series, since you asked. Sponsored by Mach V Motorsports!) The sad part of putting on the winter tires this year was that we got almost no snow. Maybe next year we'll get some deep stuff and I can have some fun.

The last wheel I tried out was a new one that we just got in. As you probably know, the new 2018 WRX STI has a larger front brake package, which requires the wheels to grow in size to 19" diameter. The Focus RS also comes with 19" wheels, too. I figure we'd better get ahead of this wheel trend and start selling some 19" Subaru-fit wheels, so I ordered up a set of Linea Corse 818 wheels wheels in a massive 19x10" size. These wheels didn't quite clear the Brembo brakes on my WRX, so I put a thin Mach V 3mm wheel spacer in place between the front wheels and the hubs.

I installed Continental ExtremeContact DW tires in a 265/30R19 size. That tire size is a bit narrow for the 10" wide wheel, so the tire looks a little stretched on the wheel, but I didn't think a wider tire was going to fit under the fenders of the WRX. The result looks AMAZING, but the tire-to-fender clearance is very tight. I didn't drive the car hard enough to really test fender-to-tire clearance, but it looks close. I didn't plan to keep these on my car long-term, and I wanted to keep the wheels in nice enough shape to re-sell, so I took them back off after taking some glamour photos. With some coilovers for a stiffer ride, and some camber to get the tires to tuck in a little more, I think it could be a usable setup for street use. 

Finally I went back to my original wheel/tire setup, the 18x9.5" Mach V Wicked Awesome wheels. The summer tires I had on the car before were pretty used up, so I installed a fresh set of 265/35R18 -- this time I chose the brand new Continental ExtremeContact Sport. This is a tire I was introduced to at the SEMA show last November. Continental had a ride-along event where you could get driven around a little track layout in a sporty BMW with a pro driver at the wheel, performing massive smoky drifts. Although none of the Continental staffers said it to me straight out, I gathered that the ExtremeContact Sport is a direct answer to the excellent Michelin Pilot Super Sport. Indeed, my experience so far is that it has all the great traits of the Michelin tire -- very high dry grip, excellent wet grip, relatively low noise, decent wear -- at a lower price. As I write this the PSS in my preferred size costs $222.97, and the ExtremeContact Sport in the same size is $181.55. That's almost 20% less expensive.
One more modification I did was to bolt on a new Mach V rear sway bar kit that we developed. This is a 22m rear sway bar kit that comes with polyurethane bushings plus a set of reinforcement bars to strengthen the sway bar mounts. The bar is 46% stiffer than the stock 20mm part. (Pro tip: Sway bar stiffness increases with the fourth power of the bar diameter.) The bar makes the car feel more neutral in corners and, combined with our Mach V lowering springs, the cornering attitude is nice and flat. I am happy with our kit because it is complete, coming with everything you need, including the reinforcement brackets, for a good price.


Products discussed in this post:
TWS Motorsport T66-F 18x9.5" wheel
Mach V Awesome 17x9" wheel
Linea Corse 818 19x10" wheel
Mach V Wicked Awesome 18x9.5" wheel
Mach V 22mm rear sway bar kit

Improved Shifting, New Exhaust Note

The Mach V WRX is sometimes last in line for modifications, since we keep pretty busy modifying customer cars, but we were able to perform some more modifications since my last blog post. We installed a new Kartboy short shifter, Kartboy shifter stop, and and lovely Raceseng knob to top everything off.

The Kartboy short shifter is an interesting part. As you probably know, the WRX uses a cable shifter mechanism, which is a departure from the old lever-actuated shifters in previous WRX models. The shift lever operates a counterweighted pivot on the underside of the car, and the Kartboy shifter is a shorter version of that pivot. Unlike some of the competing short shifters, the Kartboy unit is itself counterweighted, which gives a nice feel and sense of mass to the shift motion. And since you asked, it IS compatible with the OEM Subaru short shifter available from the dealer.

Up on the inside of the car we installed a brand new Kartboy shifter lock, which limits the left-right travel of the shift lever, further tightening up the throws on the shift lever. There are other versions of this kind of part on the market, but most are made of metal, which can lead to some noise when the shift lever contacts the stop. The Kartboy unit is made of a high-strength glass-filled nylon, which is almost completely silent when the shifter contacts it. (Kartboy banged on it with a hammer to test its impact strength. It survived.) Our prototype part was black, but production parts will be yellow.

Finally, with all these improvements in the shifter action, we thought the top of the lever deserved an upgrade in the form of a nice shift knob. We chose the Raceseng Topologi, which has a massive stainless steel core with an outer layer of Delrin. We installed the red Delrin sheath for now, but might switch colors later -- the parts just thread together, so we can swap out whenever we want.

Shifter feel after these changes is light years from the feel of a stock car. The throws are short and weighty, and you can feel click-click when the lever is going from gear to gear. It takes a bit more effort to push the lever around, but it's a welcome trade-off for the improved feel.

One final modification we made to our WRX lately is to install a Cobb cat-back exhaust. I can't say enough good about this system. It fit up perfect to the factory J-pipe, it looks great, and it sounds terrific -- it's got a good growl under acceleration, but at idle it is just a pleasant murmur. It took us a while to get one for our own car, though, since demand for the new system outstripped Cobb's manufacturing capabilities at first. The supply situation has finally improved, so the systems are readily available now.

Parts referenced in this post: Kartboy 2015+ WRX short shifter, Kartboy 2015+ WRX shifter lock, Raceseng Topologi shift knob, Cobb 2015+ WRX/STI cat-back exhaust.

More Brakes!

When we last left our hero, he had taken the 2015 WRX to the race track for a HPDE event, and found the stock brakes...not really up to the task.  The car stopped fine, but the system quickly overheated, resulted in boiling brake fluid and a soft pedal.  Even before that, the pedal feel was kind of mushy and didn't provide very solid feedback.

As you probably know, the higher-spec STI comes with larger and better Brembo fixed-caliper brakes.  I decided I'd retrofit those to my WRX. Since the car shares the same basic platform, and the WRX and STI have the same 5x114 bolt pattern starting in 2015, the parts would easily swap over.  Black Brembo calipers from the 2008-2015 STI will bolt directly on. Even the earlier gold Brembo calipers from back before 2008 will bolt up; the rears just need an adapter bracket.

I sourced some used gold Brembos from a 2004-2007 STI from our local JDM importer, Virginia JDM Motors.  I got them powder coated blue, partially because they were a little dinged up, but mostly because I just wanted them to look different.  I grabbed an STi brake rotor/pad/lines combo kit that we sell, and the aforementioned adapter brackets, and bolted it all up.

Our rotor/pad kit also came with our Mach V stainless steel brake lines.  Stainless lines don't flex under pressure like rubber lines do, which makes for a more solid pedal feel and better feedback under hard braking.

The STi brakes have larger and more massive rotors, but the aluminum calipers weigh a good bit less -- the entire swap removes almost four pounds of total mass, and weight is removed from the calipers (where we don't want it) and added to the rotors (where we do want it).  The result is very solid pedal feel, and vastly improved ability to survive hard use like our track day sessions.  Plus, the brakes definitely stand out under the wheels!

Note that the stock 2015 WRX wheels will not fit over the large Brembo front calipers.  You'll have to run some different wheels, or use at least a 10mm wheel spacer in the front.  Our 18x9.5" Wicked Awesome wheels have plenty of clearance, so that wasn't an issue for us.  (In fact, we could put a much larger brake kit under those wheels, if we wanted...)



Products mentioned in this post: Mach V complete brake pad/rotor kit; Gold Brembo adapter brackets; Mach V 10mm wheel spacers.

Lowering, Tuning, Tracking!

We've been busy with the Mach V WRX since my last update.  We added an HT Autos lower lip kit, which includes a front spoiler, side skirt extensions, and little rear skirt extensions. We found that kit easy and straightforward to install. We used a combination of factory body fasteners plus a few additional nuts and bolts to secure the additional spoiler bits.

Next we added some prototype Mach V springs. They have slightly firmer rates than the stock springs, and lower the car down a bit. You can see the results here. The production springs will probably end up a tiny bit lower than what you see here.  The springs are designed to be used with stock struts, or aftermarket upgrade struts in the future.  We were expecting the ride to get harsher with the lowering springs, but it didn't really change very much.  Body roll was reduced, but otherwise the car rides about the same as before.  The stock shocks are quite stiff, so they don't seem to have an issue handling the upgraded springs.

We also got the car on the dyno in bone-stock form.  With no modifications at all the car made 235 awhp and 246 lb-ft.  We then reflashed the car with a Cobb Tuning AccessPort Stage 1 map, and power/torque increased to 245 whp and 255 lb-ft.  Finally, we did some custom tweaking to the tune and managed a best of 256 whp and 273 lb-ft.  Again, all of this was with factory intake and exhaust -- no hardware modifications at all.  We plan to do some intake and exhaust modifications and see if we can extract some more power from the car, so stay tuned.

Our 10th annual Mach V Track Day event was on November 8-9.  We took the WRX out to the track with no specific prep work, to see how it would fare in near-stock form.  The result was "Not bad!"  Power felt great -- no complaints there.

The car handled nicely, with a modest amount of body roll and a neutral cornering attitude -- it wasn't particularly prone to understeer, nor did it oversteer.  It felt nice predictable in terms of breakaway behavior, and we never felt like it was going to bite us with any sudden unexpected moves.  The stock brake pads did suffer a bit as they got hot, but that's to be expected for a street compound.  The tires (265/35R18 Hankook Ventus Evo V12) were probably the weakest link.  Grip was never huge, but as they heated up they started to complain audibly and the grip fell off rapidly.  Not that I really blame the tires -- they are a perfectly fine street tire, but asking them to handling hard track duty isn't very fair.

Products mentioned in this post: Cobb AccessPort, HT Autos Bottom Line Kit