IMSA: Twin-turbo Honda DP engine ready for testing

RACER's ongoing chronicle of Honda Performance Development's efforts to bring a Daytona Prototype version of its P2 engine has finally reached the point where the manufacturer will unveil the car on Thursday during IMSA's two-day test at Sebring International Raceway.

Peter Baron's Starworks Motorsport, winners of the 2012 WEC P2 title using Honda's twin-turbo V6-powered ARX-03b chassis, has been tasked with preparing a Riley chassis to accept the same powerplant in DP form. The car's debut looked like a possibility for the Jan. 3-5 Roar Before the 24 until scheduling issues pushed the project back to a post-Rolex 24 debut.

With Baron's DP and PC entries serving as his primary focus during January, work continued on fitting the Honda HR35TT powerplant at Riley Technologies facility before Starworks completed the process. IMSA had the 3.5-liter twin-turbo Honda V6 on the dyno this week at NASCAR's R&D facility, allowing the sanctioning body to benchmark its performance to that of Ford, Chevy and the Dinan-prepared BMW. And with the performance values of the Honda engine in its original 2.8-liter twin-turbo P2 configuration already known to IMSA, it should be rather easy for the series to quantify and performance balance the HR35TT for the upcoming 12-hour race.

Starworks' Riley-Honda will share the track at Sebring with Extreme Speed Motorsports' HPD ARX-03b P2 entry, creating a unique situation where the same engine, albeit at different displacements, will compete against each other.

Speaking with HPD technical director Roger Griffiths, the choice to develop its P2 engine into a DP motor – effectively creating competition for itself in the TUDOR United SportsCar Championship's Prototype class – was done out of curiosity and with a bit of urging from the series.

"It was an interesting challenge for us," Griffiths told RACER. "There were enough people that came to us and inquired about it, and the folks from Grand-Am had been chasing us for years to be involved in DP, and now, the time was right. It's been an interesting project."

IMSA's attempts to achieve parity between DPs and P2s for the Rolex 24 received plenty of attention, and as Griffiths notes, he's in the odd position of lobbying for both types of Honda's Prototype engines to be elevated.

"We're trying to ensure we treat both [P2 and DP] projects equally, and it has been somewhat unique talking with IMSA about performance balancing knowing we're now on both sides of the Prototype fence," he said with a laugh. "We don't want to do anything to detract with what Scott Sharp and ESM are doing in P2. But we're being open and honest with them and with IMSA, and they're doing their best to give us a level framework for both engines."

HPD expanded the P2 HR28TT engine to the DP limit of 3.5 liters, adding 700ccs of capacity, and made a few other necessary changes to the P2 V6, but for the most part, there are more similarities than differences between the two motors.

"It's a slightly simpler engine," Griffiths explained. "It's still direct-injection. It's still drive-by-wire. Many of the parts are identical. The crankshaft is the slightly simpler version of the P2 one because the P2 one is unique for that [2.8-liter] capacity. The engine mounting arrangement is different now that it's going into a spaceframe car instead of a carbon monocoque. But the induction systems are literally one and the same."

The Ford EcoBoost-powered Michael Shank Racing team went through some installation changes with the Blue Oval's 3.5-liter twin-turbo V6 DP engine when IMSA added venturi tunnels and a large diffuser to the cars for 2014. Prior to the implementation of those items, MSR's Riley DP had the EcoBoost turbo fitted with its exhausts and turbos extending straight out from the heads close to the car's floor, but with the installation of the downforce-producing tunnels, changes were made to raise the exhausts to clear the tunnels. By working with Riley on the Honda install, Griffiths says they were able to use the knowledge gained from the Ford project to ease the fitment of their engine.

"We worked very closely with Riley on the installation, and with the extra time we had, they knew how the installation needed to be done," he added. "It's been very straightforward. We benefited a little bit Riley gained from one turbo installation while doing ours. Conceptually, they're both twin-turbo V6 turbos and the parts are nearly the same, so they knew how the routing had to be done."

Initial testing by Starworks will be conducted by recent IndyCar Series driver E.J. Viso and sports car stalwart Scott Mayer, and despite the strong links between Baron's team and HPD, it is an independently run operation and is expected to complete the remainder of the championship.

"Our expectation is that if nothing goes wrong at the test, this is the package Starworks will run for the rest of the 2014 season," Griffiths remarked. "We're limited on our physical ability to support more cars; we're not looking to add more cars this year but would like to do so for 2015. It's put Starworks in a unique position where this is not a factory Honda program, but they will receive a lot of attention and they will place drivers in the car as they require. If there's any drivers from our family we can offer Peter, we'll be sure to do so.

"And I think you will see us increase our direct involvement in both DP and P2 programs in the future; I've noticed how other manufacturers have certainly stepped up their involvement in both classes, and can see that being a path we will go down sooner than later."

Griffiths also provided updates on two other sports car initiatives on HPD's horizon, starting with the P1 engine it announced at Le Mans last year.

"The project has had a slight change of direction and has become more of a R&D program at the moment," he said.

"RealTime Racing, our partners on this project, are working as many hours a day as they can," he said. "It's not ready yet; it's an optimistic target to have it ready for St. Pete and we'll only admit defeat when the green flag drops and we can't make it; but there's also a group of us saying that unless we can test beforehand, it might be best to wait until the next round. Everyone's working as hard as possible, and we'll do so until the car's ready."