Before running in the Romanian National Rallying Championship, Valentin Porcisteanul competed in the Romanian Hill Climb Championship, obtaining two podiums in Abrud Hill Climb 2003 (3rd place, young drivers' classification) and Brasov Hill Climb 2003 (3rd place, Class N1.6).
Valentin Porcisteanu made his debut in the Romanian National Rallying Championship in 2003, his first appearance taking place at Arges Rally, as vorleiter. In his very first year he scored two class podiums in N1.6 Trophy, at the Harghita Rally and Cluj Rally, announcing himself as a strong candidate for the future seasons. Following the 2004 season in which he competed with a Dacia Nova GTI, within Class N1.6, finishing 4th at Brasov Rally, 3rd at Romania Rally and 4th at Harghita Rally, in 2005 he drove a Citroen Saxo VTS, his best event results being Class N1.6 victories at the Maramures Rally and Bucharest Rally. His positive development continued in 2006, when he scored two more Class N1.6 victories at the Sibiu Rally and Tara Barsei Rally. One year later, in 2007, he scored 7 wins in the row, at end of the season being 1st in the general classification of Class N2.
In 2008 Valentin Porcisteanu stepped into the top class of the Romanian National Rallying Championship, competing with a Mitsubishi Lancer Evo VII and finishing 7th in the Overall ranking and 4th in the Mitsubishi Lancer Cup. Porcisteanu started the 2009 season in the best possible way, with a win in Brasov Rally, followed by other outstanding results: two 2nd places in the Tara Barsei Rally and Banat Rally and two 3rd places in Cluj Rally and Arges Rally, securing a 4th place overall in the drivers' national championship. In 2010 he scored a win in Tara Barsei Rally and three second places at Brasov, Sibiu, Arad, finishing second in the Romanian National Rally Championship Ranking. 2011 is the year of the greatest success of his career – he scored wins in Brasov Rally, Cluj Rally, Arad Rally and Tara Barsei Rally, and ended up the season as the youngest ever Champion in the Romanian National Rally Championship history.In the 2012 season he won a second National Runner-up Title, after two victories in TESS Rally and Timis Rally and two podium finishes – 3rd in Transylvania Rally and again 3rd in Sibiu Rally (Intercontinental Rally Challenge).
In 2009 Valentin Porcisteanu participated in two European Rally Championship events, finishing 17th in the Rally Mille Miglia and on the 6th position in Croatia Delta Rally. In the same year he qualified and represented Romania at the final Pirelli Star Driver, a competition initiate to support young rally drivers, organised by Pirelli and the Fédération Internationale de l'Automobile (FIA).