David Reynolds and Warren Luff started Friday strong at the Sandown 500 with the third fastest time on a 1:08.931.
Luff was only 23rd in the co-driver practice with a 1:10.113s before Reynolds improved in the third practice on a 1:08.722 to end up 17th again.
By comparison, Winterbottom and Caruso were 13th, fifth, and 13th across the three practice sessions.
The #20 team felt it was down on straight line speed and has changed the engine overnight to bridge the gap to the front-runners.
At the end of Friday, Reynolds said the team had some work to do and foreshadowed an issue.
“Friday at Sandown went okay,” said the Bathurst 1000 winner.
Related Sandown 500 news
👉 The 10 co-drivers on Sandown 500 double duty
👉 Scott Pye in frame for full-time Supercars return
👉 Returning Whincup ‘a rusty sheriff’s badge’
“Car pace is okay, just that the last last run in practice wasn’t the best, probably made too good of a race car possibly and not the best quali car.
“I’ve got some ideas in my head why that is, but I need to talk to Krusty about it.
“But, all in all, good day. Luffy was on the pace, got some laps on good tyres. We’ve got a lot of data to pile through and come up with the best car for tomorrow.
“We rolled out fairly on the pace, I think track and tyre conditions probably helped us there, but, towards the end of the day, might have lost our way a little bit, but got some things to go through.”
Luff added: “It’s been a strong day. Good to get lots of practice in the car.
“We made a lot of changes and I think we’ve got a clear direction as to where we need to go to improve the car for tomorrow and obviously just start thinking about what a qualifying car is going to be.
“Weather tomorrow could be a bit of a factor in all that as well which, it’s going to be the same for everyone so not as fast as what we want it to be but we know what we’ve got to do to make it go better for tomorrow.”
Practice 4 at the Sandown 500 gets underway at 9:55am AEST.
Practice 5 starts at 12:05pm before Qualifying at 2:15pm and the Top 10 Shootout at 5:25pm.