Recently the ZR1 was SAE rated at 638 HP, 18 more ponies than previously expected.
Today speculation on the CTS-V is putting its output 17 HP over the expected 550 HP.
While the CTS-V’s LSA small-block is similar to the ZR1’s LS9, it has a smaller displacement supercharger (1.9L vs the LS9’s 2.3L) and a slightly less exotic valve-train and rotating assembly. Boost in the LSA is down to 9 psi from 10.5 in the LS9, so the LSA ditches the titanium con-rods and exhaust valves, and opts for hypereutectic (rather than forged) pistons.
While the LS9 has dual heat-exchangers, the LSA uses a single larger heat exchanger - this is a more efficient set-up permitted by the added room beneath the bonnet of the CTS. Also, the LSA has a dedicated third belt for the supercharger, unlike the two belt arrangement on the LS9. Both the LSA and the LS9 use Eaton’s new Generation 6 twin rotor, four-lobe arrangement. They claim it is quieter and increases adiabatic (thermal) efficiency to 70% . For reference, centrifugal superchargers commonly achieve around 40% (excepting Rotrex), and turbos are commonly ~80%.
Considering gearing (3.73) and power-to-weight ratio (4200#/550+HP), I’d spec it to run 12 flat.
A GT500KR is rated at 540 HP and ~3900# curb weight, is geared with 3.73s, and runs 12.10s.
The Cadillac has a 300# weight penalty over the KR. It also has IRS, which is Greek for “Wheel Hop”, which means shitty launches, which costs tenths.
However, it has a) more displacement and b) a more advanced supercharger - that could potentially mean a broader torque curve and more high-end pull. Also, It has Delphi’s second generation Magnaride suspension – the same one going on the ZR1 – which is more advanced than the one currently employed on the Ferrari 599 Fiorano. That should give it better launches than IRS is traditionally known for.
There’s also the X-factor – will the power figures be underrated? Traditionally GM underrates as a rule in performance based applications. In recent years, a solid 20 HP can be chipped off just about anything. Sparing a lecture on the rated and demonstrated outputs on 3rd party dynos, this could be a factor.