The UAK18’s underbody and diffuser package has also undergone some changes that are central to tuning and safety. A new shape at the front and sides of the sidepods are visible, as is the hole in the floor used to cut downforce on the speedways.
A significant advancement by IndyCar’s technical department has removed the unloved dome skid that was required in recent years to be used directly beneath the car. The dome skid served its purpose when a driver was caught in a spin; while sideways, the rounded skid helped produce downforce as air went under the car from the side and gave the driver greater control, but teams were also forced to raise the car’s ride height which affected performance and handling.
The new solution has been to remove the dome skid and install elongated ‘bumps’ (pictured above) on the outer edges of the underwing. Those rounded add-on oval safety pieces act in the same manner by creating downforce while sideways but, thankfully, teams do not need to raise the ride height.
Another notable trait that’s new to the UAK in Speedway configuration is the sensitivity to hot track temperatures. With the underwing responsible for a much greater portion of downforce production at Indy, hot days and a hot track means thinner air is working beneath the cars. Just as that thinner air makes less downforce when running below the front and rear wings, a much bigger loss is experienced below the car’s biggest wing – the one out of sight that sits inches above the circuit.
If it’s hot in qualifying or the race, teams will need to pile on more topside downforce because they do not have the ability to make more downforce with the underwing. There are no provisions for doing so in the rules, and as we’ve already covered, the rules do not give much leeway to use the topside wings to glue the cars to the ground.
The last area of tuning for engineers is found with the diffuser, and frankly, the options there aren’t worth exploring. Through 2017, teams were allowed to remove one or both sidewalls, which came with a heavy downforce cut and a minimal drag reduction. Most drivers could get comfortable running with only one sidewall in place, and only the brave – and crazy – tried lapping with both sidewalls taken off the diffuser.
For 2018, IndyCar has given teams three sidewall choices: the standard sidewalls can be used (the longer sidewalls from 2017 have been banned), a highly trimmed sidewall version can be installed, but those are close to having no sidewalls, and teams can remove both sidewalls. The option to remove a single sidewall has also been banned which, in all reality, means most teams will likely stick with keeping both standard sidewalls attached in qualifying.
Only the desperate would take the second or third options.
A few Gurney options, some wing angle, and a lot of talent will be required to extract speed in qualifying. Knowing how few aero options teams have at their disposal, mechanical setups will be more important than ever.
Some might get most of the pieces in order but, as a whole, solving the UAK18 puzzle just might be impossible at Indy this year.