[ad_1]
The championship will soon begin the first phase of a transient dynamometer testing program that aims to definitively put an end to conjecture about parity.
Engine performance has long been a bone of contention and has been brought back to the forefront following the completion of off-season category wind tunnel testing and a minor center of gravity change in recent weeks, not to mention a lopsided run of results at Hidden Valley last month.
The current supercar engine parity regime relies on accumulated engine horsepower (AEP) and engine weighted average horsepower (EPWA) measurements, which are a legacy of the five-litre pushrod engines that powered most supercars for 30 years.
While there have been multiple engine manufacturers at any point during this period, the task of achieving parity is undoubtedly more difficult today than it was when the championship featured only Fords and Holdens due to the different architecture and displacement of the Gen3 engines.
The fact that the Ford Mustang is powered by a 5.4-liter quad-cam engine—an unusually undersquare engine, to boot—and the Chevrolet Camaro by a 5.7-liter pushrod engine raises questions about whether the two engines accelerate differently.
Ironically, while Mustangs were consistently slower in the speed trap at this year’s season opener at Mount Panorama, new Ford engine supplier Dick Johnson Racing was reportedly forced to install a smaller air restrictor to ensure it didn’t exceed the AEP ceiling.
However, according to independent engine expert Pete Wallace, supercars should get rid of restrictors in order to try to achieve parity.
The solution, he says, already exists, thanks to the fly-by-wire accelerator that is standard on the field under Gen3 regulations.
Instead of the accelerator pedal being physically connected to the engine by a cable, the movement of the pedal triggers an electronic signal that opens the throttle.
Wallace, who was the engine builder for Stone Brothers Racing from the mid-2000s to the 2010s, says Supercars can map the throttles so that torque output is equal across the rev range.
“The throttle position is set in 10 percent increments from zero, and then the engines are designed to be identical,” he explained to Speedcafe.
“Let us be at eight percent [butterfly opening] and a 10 percent, but as long as the tightening torque remains the same, throughout the trip. No restrictor.
“Then, 100 percent [pedal]we could be 100 percent [butterfly] and the other one could be 80 percent, 85 percent, 90 percent… I don’t know.
“It’s going to change throughout the rev range. One engine relative to the other might be at 100 percent at 4,000 rpm and the other engine might be at 92 percent at 4,000 rpm, then it might be the opposite at 5,000 rpm, and so on throughout the rev range.
“Across the range, they won’t do it [necessarily] be the same.”
In short, the throttle is mapped relative to the throttle pedal mapping across the entire rev range, to make torque equal.
The problem with using a restrictor is that it is a fixed physical object and therefore cannot be adapted to compensate for engine-to-engine differences in rev range and throttle position.
“They would seek acceleration [on the transient dyno]” , Wallace said.
“They would also be looking for parity, which means ‘equal,’ and at the moment I don’t think they are equal because of the restrictor.
“The restrictor only works at 100% throttle, so at every other throttle position the two motors are different.
“You might be better at the beginning of the revs and it might change halfway through and then it might change again – that’s acceleration, and that’s coming out of the corner.
“On paper, it would be difficult to get the same 5.7/5.4 ratio, but not if you use fly-by-wire, which they imposed.
“If you had used a throttle cable, you would have had to use the restrictor, but if you use the restrictor, it must be calculated so that the exit angle is seven degrees; no wider.
“In the size of things I saw in Gen3, earlier, it would have been at least 350mm long at the throttle exit, and then what would happen is the throttle response would be better and that’s because the pressure recovery in the plenum would be faster with the seven degree exit angle.
“But, as I said, you don’t need that restrictor; you just set both engines up, 10% throttle on the dyno, equal torque on both engines, whatever percentage they need; 20% throttle on the dyno; and so on up to 100%, and both engines with equal torque, whatever throttle or RPM they need.”
According to Wallace, fuel consumption would be even closer, and therefore there would be no need to return to the use of mandatory pit stops as a measure of parity in enduros, a rule that was already removed last year.
The engines have already been shipped to the US for transitional dyno testing, with a setup phase to take place after this weekend’s NTI Townsville 500.
