Boosting the power output of Project Gruppe R, our 2013 VW Golf R, is one of the last big ticket items on the build sheet. We have intentionally left this field blank while we focused on the brakes, suspension, wheels and tires, and aero, because as much as people equate power to bragging rights, it really ought to be the last consideration on a true holistic performance build.
The factory power and torque numbers were top of the range when the Mk6 R came off the line in Wolfsburg. But having been eclipsed by the Mk7 and competitors like the Focus RS, our car is looking a little left out.
Our approach to power will be admittedly conservative, a true WRC rally car only outputs in the neighborhood of 315 horsepower, their fiercely strained 1.6-liter mills live on the edge. Gruppe R will never match the emaciated weight of the WRC Polos, so power to weight will not be a fair comparison. We seek to bump up our 2.0-liter powerplant to a comparable performance level, without the hand grenade life span. We turned to Remus Exhaust, APR, and VP Racing Fuels to see that our rally/recce project keeps up with the times.
VW reports 256 horsepower and 243 lb-ft of torque at the flywheel for the Mk6 Golf R. We covered the driving impressions of the power delivery in our introductory article, but suffice to say it’s great, but there’s always room for improvement.
Wheel horsepower is what really matters when you’re talking seat of the pants dyno, so we decided to take our own baseline readings. The Power Automedia garage is well equipped with our own Dynojet 224xLC dynamometer, but for AWD cars we have to look to our local network. Just across the way from our headquarters we find MakSpeed, and import tuning authority Myles Bautista.
“I’ve been at this location for five years. I used to have a company called RevHard back in the day that produced many of the Honda turbo kits available at the time. I sold that company, moved to Temecula, and worked for a dealership for a while before I decided to start back up again with MakSpeed,” Bautista introduced himself.
Rather than using a conventional drum style chassis dyno, Bautista uses two pairs of Dynapack 2000 series system to create an AWD model. Think of it as four individual dynos that work together to read the output directly at the hubs. This system requires you to remove the wheels and install splined hubs that engage the dyno. This system may not be as convenient as rolling up onto rollers, but it is known for its accuracy by removing variables like tire slippage, tire pressure, strap tension, and the rotational mass of the wheels and tires.
“You can run Dynapack dynos at nearly any RPM and any load because they use a hydraulic load control system rather than an electrical eddy current system. There’s no tire slippage, so if you have a car that’s making a lot of power at low RPM, the tire isn’t going to slip like it would on a roller,” Bautista explained.
After we got the Golf mounted onto the dyno, we made a few pulls to confirm our baseline numbers. As we mentioned, VW rates the Golf R Mk6 at 256 horsepower at the flywheel. We put down 248.2 hp and 264.4 lb-ft of torque on the first pass — that must be some efficient driveline to have such a minimal parasitic loss.
New Wolf Inside With Remus
The sound emitted by any custom car is an important part to the haptic and immersive experience as a driver. Driver involvement is becoming more and more of an abstracted connection, as so much control and sensory input is removed in the name of comfort and civilized manners.
There are no shortage of exhaust suppliers on the market for the Golf R. From all over the world, these vendors gather and try to distinguish themselves from each other. How does one choose who to pick?
The OEM exhaust is, as expected, very tame – however, it exhales a deep note that subtly draws the attention of those within earshot. What if VW offered a “plus” package, where the OEM exhaust was tuned to the enthusiasts’ ear? That’s where Remus comes into the picture. Remus is not only a world-wide supplier of performance aftermarket racing exhausts, they also hold a number of OEM contracts to produce factory equipped exhaust systems for VW, Audi, BMW, Porsche, AMG and more.
“There has been a long history of racing since Remus was founded in 1990,” says Mike Bower of Remus. “Names like Damon Hill, and Jacques Villeneuve can be found in the history of Remus racing. Remus is involved as a technical partner in different racing series – we do exhaust development for several rally and touring car teams.”
Remus Racing Exhaust Specs
100 percent stainless steel construction
70 mm racing tube
98 mm carbon fiber tips
Uses OEM hangers
Like an experienced bartender or sommelier, the acoustical engineers at Remus ply their command of materials and design to complement a specific automotive platform with a suite of pleasing exhaust noise — making deft pairings to ensure the end result is pleasing on the auditory pallet.
“Remus in general is not going to be obnoxious or super loud. We air for a deeper tone when possible, it might not be too loud at idle, but it really comes alive when you are at wide open throttle,” explained Bower.
Construction And Development
We apply several different testing procedures in our sound chamber for every specific exhaust system. Using different exhaust prototypes for one specific vehicle, we do sound profiles outside and inside of the car. -Mike Bower, Remus
Building that right sound for a given application is a part arbitrary, part scientific endeavor. Using audio measuring equipment and software like Catia and ProEngineer, Remus engineers go to work in the sonorous chamber.
“We apply several different testing procedures in our sound chamber for every specific exhaust system. Using different exhaust prototypes for one specific vehicle, we do sound profiles outside and inside of the car. We also do sound source location tests and recordings with our ‘head and torso’ system to see how the sound appears to the human ear,” Bower expanded.
Of course, performance gains are considered in tandem with achieving a pleasing sound. Remus develops their racing exhaust systems to maximize power while maintaining their EEC approval for road use.
“We do flow and back pressure optimization, in special cases we even do a proof of welding seam quality. There are two ways to design a perfect sport exhaust – in one hand we have the scientific calculations and design with modern software. In the other there is still the ‘cut and try’ approach (of course in a sophisticated way). Both ways are possible, and sometimes a combination leads to the best product,” Bower continued.
Exhaust Install And Results
Because Remus is an exhaust supplier to VW for OEM systems, their tooling and jigs make for a fantastic fitment of an aftermarket system. We were able to install our cat-back with the car on jack stands.
Our first step was to remove the original system. With some channel lock pliers we freed the muffler and mid-pipe from the rubber hangers. Our first step in installing the new system was to hang the new mid-pipe in the hangers.
This racing system eliminated the stock resonator, and to determine where the cut should be made behind the catalytic convertor we slipped the delete tube in the mid-pipe and marked a cut line.
After cleaning up the rough edges we could fit up all the mandrel bent tubing. With the stock muffler on the ground next to the new Remus unit, we transferred the rubber hangers and brackets. Lifting the new muffler in place we aligned the slip joint, and bolted up the hangers in the stock location. We left all the connections loose to get the exhaust tip protrusion from the rear valence where we wanted it. After tightening everything down it was time for a test run.
We depressed the clutch and hit the push-to-start, firing up the cold engine. To light the catalytic convertor, the ECU held the idle high and retarded the timing. This exhaust note was mellow but noticeably more rich than the stock sound.
The sound profile of this system is very low frequency, minimal rasp, and certainly no cheap tinny sounds. Driving around in city traffic, interior cabin noise is comparable to stock. As expected, the Remus system is not an in your face exhaust, it burbles unassumingly. Even without the resonator, drone is almost undetectable unless you are lugging the engine slightly.
When your right foot gets a little excitable, and you get a serious load on the engine up in the reaches of the powerband, things wake up. A strong European “ahem” from the exhaust is the first sound, but as the K04 turbo spools up, a sedate whistle is expelled from the exhaust – a lovely reminder.
The Remus racing exhaust is never loud, much like the demeanor of the Golf R in comparison to it’s contemporaries. Rather, the note is befittingly restrained. This exhaust is not going to piss off your significant other, neighbors, or prevent you from listening to the radio or taking a phone call, but when you’re out for a hot lap it rewards you.
APR Maximizes Our Options
It’s well known that manufacturers leave horsepower on the table when a car goes to market. Their reasons for doing this are manyfold; longevity, economy, and leaving room to grow as the platform ages.
“There are typically over 21,200 3D maps, tables, and numerical values within the Mk6 GTI ECU that can be adjusted, and over 15,800 variables to log. Finding each of those isn’t easy and takes years of reverse engineering, and even a little insider info, to figure it all out. Then finding how the maps all interact is even more troubling and difficult,” Arin Ahnell of APR explained.
“Once we’re in, we then have to reverse engineer the ECU. We have to locate all the maps, figure out how they are scaled, and how they all work together. From there, we’re able to update our tools for calibrating and datalogging the ECU so we can begin tuning. We’ll instrument the vehicle with pressure and temperature sensors throughout, and being down a long road of testing and tuning to increase horsepower and torque while ensuring we’re doing so responsibly. This means figuring out how the factory ECU controls output, and making changes to increase power while keeping factory control and safeguards in place. Once finished, we begin a beta testing process in the field at various altitudes and weather conditions, with multiple fuel types, assess the results, make changes where necessary, and then release the product to the public,” he continued.
As we outlined in our goals at the beginning of this piece, we decided to keep things reasonable and went with an APR Stage 1 tune. This level of ECU flash requires no bolt-ons, or modifications to the car in any way, and virtually no concessions are made to drivability or economy. In fact APR boasts a slight improvement in fuel economy. Claimed gains in horsepower and torque bring the stock numbers up to 302 horsepower and 297 lb-ft on 91 octane.
We asked what exact parameters and engine management changes APR makes to pick up the horsepower VW left on the table. We found that a complex combination of boost control, ignition mapping, cam phasing, and other tweaks are what get us the extra power.
We do our best to exploit what we find, and rewrite the playing field for a more ‘juiced’ up engine. -Arin Ahnell, APR
“We can tell the ECU to spin the turbocharger even faster, allowing it to force in even more air. The ECU then adds the correct amount of fuel based on the mixture ratio we’ve prescribed, and the spark plug fires at the most optimized point for all of the operating conditions and fuel grade characteristics, and the result is more power! Going beyond this, we tweak many other items, such as valve lift and cam phasing, where available, to optimize the volumetric efficiency of the engine and further increase output,” Ahnell delivered in layman’s terms.
APRs tuning not only affects engine output, but raises the rev limit from 6,800 rpm to 7,100 rpm, disables the top speed limiting, and allows for left foot braking while on throttle – all valuable changes for the track driven car.
Our local APR dealer was able to plug in and get us out in about 30 minutes. We opted to upgrade to allow program switching between performance levels depending on the fuel at hand. With four slots at our disposal we elected to retain the stock tune, and add APR 91 octane, APR 100 octane, and a valet mode which crushes the car’s performance should you hand the keys to someone. “This will depend on the application, but typically we limit power to lower than stock levels, limit engine speed to around 4,000 rpm, and install a 40 mph speed limiter,” Ahnell explained.
Switching between the maps is as simple as a inputing a cheat code in a game console. After inputing our unique four-digit security code, a series of indicator stalk movements and button pushes allows the user to change tunes.
During our baseline testing session we opted to test the Stage 1 map for ourselves. The curves did overlay just like APR advertised. The power produced at the wheels was 262.1 hp and 277.0 lb-ft of torque, if you consider a typical 20-percent parasitic loss from flywheel to wheels, that puts the power around their advertised claim of 302 hp at the crank. Our results were nearly exactly what APR promised. The power we picked up was mostly through the mid-range, making for a very usable boost in daily driving conditions.
“But, complex is good. The platform has a ton of closed loop control. That means it works off the input from sensors, and some assumed, or modeled, information to make adjustments to the calibration to ensure it’s always delivering the right amount of fuel, airflow, and ignition,” Ahnell conceded.
“This is a powerful ECU, and it has loads of ways to accomplish different things that are often left turned off and only enabled on higher end RS or sportier models on other platforms. Some of these items never see the light of day, but they are there for whatever OEM picks up the ECU and decides it’s the one they will use for their vehicles. We do our best to exploit what we find, and rewrite the playing field for a more ‘juiced’ up engine,” he concluded.
Unlocking Potential With VP Racing
The last phase of our powerplant tuning has us put all the pieces together for a final dyno session. APR does not publish numbers for the 100 octane tune in Stage 1, and we want to know what sort of potential we can unlock when on the right fuel, tune, and with our Remus exhaust. Because APR’s 100 octane version of the Stage 1 tune can account for the added detonation-resistance, the engineers can push boost, timing, cam phasing and other parameters further before any knock occurs.
To get the right go-juice in our Golf for this test we turned to VP Racing Fuels. Unleaded high-octane fuels have become a reality as chemistry has been forced to keep up with evolving emissions regulation and vehicle sensitivities. VP has developed California Air Resources Board (CARB) legal racing fuels that are tetraethyl lead free, but still carry the octane rating to support aggressive applications of timing and boost.
“These fuels are meant for the guy with a high performance car that requires a catalytic convertor or wants unleaded fuel. VP100 and VP101 are street legal, and under that product name they are only available at the pump because the tanker truck goes through the certification process, and they will not harm a catalytic convertor,” Steve Sheidker of VP explained to us.
Tetraethyl lead has long been the octane enhancer of choice for avgas, race gas, and pump gas (until it was phased out). The chemical engineers at VP have to work extra hard to formulate fuels to meet the demands of modern day racers while keeping up to CARB and EPA requirements.
“It’s extremely difficult [to bring up octane without lead]. I can tell you with confidence, to get this high of octane is one of the hardest things the chemists have to do. Without lead you have to do some fancy chemistry,” Scheidker concluded.
The final step of our plan to unlock some power in Gruppe R was to put all the pieces together. APR’s tune, Remus’ exhaust and VP Racing HP101 fuel to utilize the 100 octane APR map. We drained the tank and headed back to MakSpeed for a final test. Our ultimate results were 276.4 horsepower and 306.6 lb-ft of torque.
Our new curves show that we gained a considerable jump in horsepower and torque in the bottom end, mid-range and top end. The overall profile of the curves is far smoother than the original OEM plot – which proved the slightly laggy power delivery we experienced behind the wheel was quantifiable.
The new power in Gruppe R has helped transform our rally/recce project into something that truly feels like it has grown into its own personality. Before, the Golf R was a great platform but a bit lacking in a few of the performance focused areas we think are important. Not only does the car sound the part, but it delivers on the turbocharged thrust it promises.