The ByKolles-run squad returned to the WEC this year with the non-hybrid Vandervell 680 LMH, the successor to the troubled CLM P1/01 LMP1 car that failed to finish Le Mans 24 Hours in six successive attempts.
Vanwall’s season so far has been plagued by a number of reliability issues, most notably a brake explosion at Portimao that led to Jacques Villeneuve’s race-ending crash and an engine failure at the Le Mans 24 Hours that forced the team into another retirement.
In the previous round at Monza, the team also lost a chunk of the time in the pits to clear brake ducts amid overheating issues, leaving it 20th - and behind eight LMP2 cars - at the finish.
However, Guerrieri, who has been part of the Vanwall LMH programme from its inception and is the only driver to have taken part in every race with the team in 2023, explained that the Vandervell 680 is gradually turning into a reliable machine and has encountered no major technical problems recently.
“I would say during Monza we didn't have any big reliability issues and so far this weekend [at Fuji] as well,” Guerrieri told Motorsport.com. “So in that area we are doing pretty good.
“There are little things here and there, like today [Friday] we had an issue with the steering rack, probably [ran] over a kerb or something.
“Things can happen, we assess this as an issue as well. But [the reliability is] looking much better.”
Asked if that meant Vanwall could now put more effort into extracting more speed out of the car, Guerrieri said: “We don't have any reliability issues, definitely yes.
“Performance-wise and set-up we have been trying different directions. But it looks like there might be more structural issues or problems that we need to improve and it's not only around the set-up.”
Vanwall looks unlikely to be in the mix in this weekend’s Fuji 6 Hours, with Guerrieri’s team-mate Joao Paulo de Oliveira conceding that the team is still several seconds off the pace.
“Having the reference from Monza, I know we are going to be two to three seconds off the pace of the top cars,” the Brazilian told Motorsport.com.
“We were less than two seconds in FP2, which is a good sign. We will just try to keep working. We don’t really know in terms of pace if we go anywhere further ahead.
"I see some potential to be unlocked [in the car], but I’m not making the decisions. I just follow what is decided as a team.”
Vanwall was one of the two privateer LMH teams to sign up for the 2023 season, the other being Glickenhaus, and is sharing the grid with factory cars from Porsche, Toyota, Ferrari, Peugeot and Cadillac.
A limited testing programme put Vanwall on the back foot going into the campaign, and a lack of a test car has since held back the German-based team in its quest to catch up to its rivals.
After five rounds, Vanwall has a best class finish of eighth to its name, achieved in the season-opener at Sebring, and it has regularly looked inferior to Glickenhaus’ more reliable and competitive 007 LMH.
Guerrieri feels Vanwall has made plenty of progress since the first race of the season in March, but feels there is room to improve the team’s operations in order to be more competitive in WEC.
“We started a bit late with the development project of the car, so there was not really much useful testing that we could have done during last year,” he said.
“So we went to the first race in Sebring a little bit like, ‘okay, let's make a starting point here and try to earn a lot during the experiences of a race weekend’, which is also very important, which is where you have the most tension.
“I cannot really [rate the season] with a number but I can tell you we are improving every time and learning from things that are happening during the race weekends because we basically haven't done any testing since the year started.
“There are some things you cannot change from one day to another, it's more like a structural thing that we need to improve. But we can always improve on the operational side, with the procedures.
“I think there is room there for improvement and we are assessing this and we are working on the direction to try to maximise the potential that we are having right now."
