When VW launched the Polo GT Twins in India, I doubt they had any idea how cult these cars would become in the Indian Market. The GT TSI came with its swanky 1.2L turbo engine mated to a slick and super fast double clutch auto gearbox and fancy ESP and other electronic nannies. For the diesel GT TDI, VW stuck to the good old Hot Hatch formula; small light hatchback; a big 1.6L TDI engine from a Sedan one segment higher mated to a manual gearbox and devoid of any electronic nannies. That is what the Polo GT TDI is, the First true hot hatch in India, and with a fuel we Indians love to use; DIESEL!
Mayank and I debated all night over a bottle of malt about which GT he wanted, and after a sleepless alcohol filled night the decision was done. A GT TSI! Somewhere in the middle between sleep deprivation and hangover, he went ahead and got a GT TDI the next day. Only two reasons for chosing the TDI over the TSI, Manual GearBox and 250NM Torque. That is what started the story of this build. Good single malt, a hangover and then a test drive of big torque going thru a manual gearbox.
The Polo GT TDI makes 105hp and 250NM in its stock state of tune, but with the help of Tune O Tronics, we were able to bump up the power output to 130 horsepower and 280NM of torque. To keep things under control, the car was outfitted with wider wheels and tires. The wheels size was kept to 15 inch to be able to use the car as a daily driver, and also simply because 15inch rims weigh roughly around 2-3Kgs less than a 16incher. Lower wheel weight means more of that 120hp goes to ground!
In stock form the car is serious quick, but when remapped; it becomes a whole new monster. Acceleration in the gears is instant, and it can easily embarrass nearly every family petrol and diesel sedan and hatch on the road. Any VW/Audi/Skoda 2.0TDI will eat this car’s dust till some pretty high and illegal speeds. But Mayank wanted more so he went ahead and opened up the exhaust to a custom straight pipe setup. With the turbo having more room to breathe now ToT send him an updated map that made more power. Up the boost a bit more along with some fine tuning and this car was sitting 135 horsepower and 330NM Torque; in a hatchback! The car can pretty effortlessly cross the 200kmph mark and can keep going.
While all this power is good, the stock suspension leaves a lot to be desired of. Being designed for a comfortable ride, the car was severely compromised on track, with terminal understeer till the point of no return. The cornering ability of this car needed serious work for it to be able to set a good lap time at the NASA Time Attack Track Days. With Coilovers out of the question due to the daily commute of this car, we went for the next best thing. A WhiteLine rear adjustable sway bar.
Install is straightforward and the adjustability helps tune the car’s handling to suit various conditions. The sway bar really settled the car while keeping the ground clearance and comfort of the stock setup. With the Sway Bar installed the terminal understeer that plagued the stock car on track was more or less neutralized unless you go into a corner faster than you should in a FWD car. What was hilarious was the amount of oversteer this introduced into the car with the sway bar set to full hard. The real proof was in the laptimes which reduced from hovering around the 2:45-46 mark to 2:41!
Next up was improving the engine life. Like in any remap that increases boost, the intake air temps go up. With the boost upped to north of 16PSI and summer on top of us, a quick log showed IATs hitting nearly 85-90 degrees in just 3-4 pulls. Granted Diesel engines run hotter than petrol ones, but in no case is a IAT of 90 degree C ever acceptable. We need a bigger Intercooler! A lot bigger.
Enter Darkside Development UK. For those who don’t know, Darkside specializes in tuning and parts for the VAG groups diesel engines. They do ONLY diesel parts for nearly all VW/Audi/Skoda diesel engine. We ordered a larger intercooler that had nearly 5x the capacity of the stock unit along with full custom piping for it to mate up the the OEM Turbo outlet pipe and the throttle body. With the intercooler installed, the IATs never went beyond 55 degrees, no matter how many repeated pulls we did. Problem 1 Solved.
While doing the repeated data logging runs to test the intercooler efficiency, we noticed that the engine temp needle kept going up. A quick check of the Engine Oil and coolant temps showed that the car was heating up and after some digging we figured that the Turbo in the car was both Coolant and Oil Cooled and with the boost upped beyond stock config, more heat was being transferred to the engine oil. Now under normal conditions this won’t pose a problem but on a car that’s regularly doing track duty, high oil temps is a very bad thing.
Enter Darkside Development again!
They carried a Mocal Oil cooler with a thermostat mating plated to replace the tiny joke of an oil cooler that came stock with the car. A quick track day with logging for oil temps showed the temp needle planted firmly at 90, and no overheating on the oil.
That’s where we are with this mad mad car as of now. But Mayank isn’t done yet. He got a lot planned for this car so stay tuned to this build thread.