Cadillac DPi teams to race with smaller engine

Cadillac DPi teams to race with smaller engine

IMSA

Cadillac DPi teams to race with smaller engine

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The three teams representing Cadillac will go into the 2018 season with redeveloped engines installed in the back of their Dallara-based DPi-V.Rs.

Following a year where the Cadillacs from Action Express Racing and Wayne Taylor Racing won 70 percent of the IMSA WeatherTech SportsCar Championship events with a 6.2-liter naturally-aspirated V8 powerplant, the brand – with a new car added in for Spirit of Daytona – will pursue another title using a 5.5-liter V8.

The loss of 700ccs of capacity from the combustion chambers, which equates in volume to approximately two 12-ounce cans of Coke, will take some power and torque away from the two AXR Cadillacs and the pair of SDR and WTR DPi-V.Rs. The de-stroked 6.2-liter engine will also bring the Cadillacs closer to the general performance figures found in the other DPis from Acura, Mazda, and Nissan, and the spec Gibson V8 engines that power the WEC LMP2s in the Prototype field. 

Cadillac tells RACER its DPi-V.R powertrain (approximately) meets the IMSA-mandated power level, generating 580hp at 7,050 rpm. It features an Earnhardt Childress Racing-designed semi-stressed engine mounting system with integral oil lubrication (a self-contained dry sump lubrication system), a dynamic pressure (ram-air) intake system with IMSA-mandated sonic air restrictors, and in terms of exhaust has a rear-facing, top exit, dual outlet, multi-branch exhaust header system.

From IMSA’s side, having the four DPi models and all of its P2s in the same Balance of Performance hemisphere should make its job easier and, in theory, prevent the need to apply heavy BoP restrictions to the DPi-V.R or other cars to establish parity.

“I think it will be a performance difference, and there are pros and cons with it. It’s a little bit smaller, so you lose some torque, but you also gain drivability, so it balances out,” defending Prototype champion Jordan Taylor told RACER. “As a driver, it will be interesting to learn how it will affect working through traffic, and how it will change tire life with the different energy being put through the rear tires.

“But the thing we’ve been talking about the most as a team is how the engine lines up a little better with the other engines in the class, so when IMSA is looking at making BoP adjustments, they’re not looking at this big 6.2-liter engine; they’re looking at a more relatable 5.5-liter engine.”

This weekend’s Roar Before the 24 will give Cadillac teams a first look at the performance attributes of the motors prepared by ECR.

“We haven’t run the engine yet, so we’re as curious as anyone to see what it’s like,” said AXR engineer Iian Watt, whose team won three consecutive Prototype titles from 2014-2016. “It’s a Cadillac engine, so we know it will be good. I think of it like a new tool, like a golfer getting a new putter. You learn how to work the tool to the best of your ability, and then go compete with it. It’s a plug-and-play kind of thing.”

Taming the Cadillacs required some extraordinary measures from IMSA’s technical department in 2017. As Taylor found in his Wayne Taylor Racing DPi-V.R, tiny air restrictors, fixed first and second gear ratios and low downforce made the car increasingly difficult to drive. The anticipation of what’s ahead with the smaller engine has been a relief of sorts for the Floridian.

“There were some creative things done last year – taken to an extreme level – to pull the Cadillacs back, so if there’s a need so slow us down or speed us up, I think it will be done in the same kind of way used with the other prototypes,” Taylor said.

“I think we’ll find horsepower and torque will be in line with everyone else, so for us, we know we can go as hard as we can and don’t have to worry about the BoP side so much. ECR builds great engines, so the only thing we’re going after now is more mileage on the 5.5-liter engine at the Roar to get ourselves ready for the big race.”

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