Sonoma Weekend Notebook

***Renger van der Zande has the pole position for today’s race, Round 18 of the season for the Pirelli World Challenge, in the No. 31 EFFORT Racing Porsche 911 GT3 R. The green flag occurs from a rolling start at 4:50 p.m. PT and local time.

***Following last weekend’s round at Miller Motorsports Park, both the Cadillac ATS-V.Rs and Nissan GT-R NISMO GT3s have been hit with Balance of Performance adjustments. Both have received lower Boost Limit ABS; the Cadillac is down 0.03 mbar and the Nissan is down 0.02 mbar. Additionally the Audi R8 LMS ultra has received a 10 kg minimum weight break.

***The 2016 Pirelli World Challenge schedule is coming together, with a majority of the races on the 2015 schedule set to return. A handful of events – including at least one further potential new venue – are on the radar or are in discussions with the series to be added. A formal announcement should come around or at the season finale weekend at Mazda Raceway Laguna Seca.

***Nick Catsburg was due to race this weekend, but the Dutch driver has been sidelined due to circumstances out of his control. The Blancpain Racing transporter was involved in an accident en route to California.

***After their withdrawal from Miller citing an issue with the series’ boost adjustments, K-PAX Racing with Flying Lizard Motorsports’ pair of McLaren 650S GT3s are back in action at Sonoma this weekend. It comes at the team’s home race, with the Flying Lizard headquarters based at the Northern California facility.

***TRG-AMR has its biggest weekend of the year at Kevin Buckler’s team’s home race, with five GTS class Aston Martin Vantage GT4s joining Christina Nielsen in the sole GT3-spec Aston Martin V12 Vantage GT3. Nielsen returns after missing Miller due to her IMSA commitments at Virginia International Raceway. Buckler’s team also held its annual Petaluma headquarters party on Friday night.

***While Renger van der Zande fills in for Ryan Dalziel this weekend with Dalziel on assignment at the Nürburgring, EFFORT is working on its 2016 series program. An announcement of its 2016 car is expected within the next month.

***Both “Heds” return to action this weekend with Scuderia Corsa’s Mike Hedlund of Woodsideback for the first time since Long Beach, now classified in GTA in the No. 65 Ferrari 458 Italia GT3, and DragonSpeed’s Henrik Hedman here for the first time since Canadian Tire Motorsport Park in the No. 10 Mercedes-Benz SLS AMG GT3. Hedlund made a particular impression last year at Sonoma, with sixth and fourth place overall finishes.

***James Sofronas, GMG Racing team principal and driver, is sidelined from driving again this weekend due to his back injury. It leaves GT Cup class driver Alec Udell as the lone GMG entry this weekend, several hours north of the team’s Santa Ana, Calif. base.

***WC Vision announced Saturday it will donate $5,000 to the children of Justin Wilson – the Wilson Children’s Fund — as well as any fines from the GT, GTA, GT Cup and GTS division races this weekend for the Pirelli World Challenge rounds at Sonoma Raceway. All teams have tribute decals on their cars too.

***In GTS, three cars make their season debuts, in the form of the long-awaited Hyundai Genesis coupe from GAINSCO/Bob Stallings Racing, the new Audi TT-RS from Compass360 Racing, and a Lotus Evora GT4 from VSA Motorsports. Nissan GT Academy driver Nic Hammann also makes his class debut in the Skullcandy Team Nissan 370Z; the GTS field has ballooned to a season-high 25 cars, with the previous best 23 at Barber.

***The GAINSCO/Bob Stallings Racing Hyundai has had four days of testing, primarily shakedown runs, with Jeff Harrison behind the wheel filling in for Jon Fogarty, who is at the Nürburgring for the FIA World Endurance Championship this weekend. Harrison, of Grapevine, Texas, is an open-wheel veteran who has also made a handful of Porsche Supercup starts; he’s known Stallings for more than a decade. He’d actually raced Bentley Team Dyson Racing’s Guy Smith in a European junior formula, the Vauxhall Junior series.