I am enjoying my 2008 Cadillac STS-V; it is a terrific design right out of the box. Cadillac pulled out some stops in developing this unique 4.4L Supercharged Northstar variant. For example, the exhaust manifold was extrude honed to optimize flow. Originally the V was rumored to get 440 hp, but with some final tuning the team was able to raise the STS-V to 469 hp.
An engine dyno as in the graph above measures horepower at the crank (hp). A chassis dyno measures horsepower at the wheels (whp). Horsepower at the wheels includes inefficiencies of the powertrain.
For an automatic RWD automobile, powertrain inefficiencies often run 20% of the power. So for a 469 hp STS-V, one might expect to measure 469 x 0.8 = 375 hp at the wheels. From my research, most STS-Vs measure 360-370 hp at the wheels, so perhaps a bit more than 20% loss at 22-24% due to luxury isolation in the powertrain. One outlier pulled 379-387 whp however.
HP is often used to indicate hp at the crank, and whp, or wheel horsepower, is used to indicate horsepower at the wheels.
To go from chassis dyno wheel hp to hp at the crank, divide by 1-inefficiency. So if inefficiency = 20%, WHP/(1-20%) = WHP/80% = crank hp.
The classic hot rodding questions are,
- How much money do you have? and
- How fast do you want to go?
The hidden gem in this discussion is, before you sink a ton of money into your car, you should have a plan. If you want to achieve a specific goal, then you might start with a different car, for an extreme example.
Supercharged Northstar
My goals for developing my STS-V:
- It is a Cadillac: maintain luxury features, & avoid “noise for noise sake”
- Test and Tune: only add / change items which prove to add performance
- Phase 1: 500 hp, so 400 whp
- Phase 2: 550 hp, so 440 whp
What will that let me do?
- Be happy that the Cadillac STS-V is tuned to optimum performance
- Enjoy the journey of researching, selecting, testing, and writing about the Cadillac Project
My first Project looks set to be a Spectre intake from Jaime at StreetSideAuto. In Spectre’s tests the intake added 40+ whp. True Street Motorsports has agreed to help with testing the new intake once it arrives using their Dynojet dyno. First we’ll establish a baseline for the STS-V stock. Then hopefully we can get clear before/after apples to apples tests with and without each modification.
In my True Streets Motorsports correspondence they refer to the test as “Project Cadillac”, hence today’s title.
Other project ideas in sight:
- Custom Tuning
- Intercooler pump, reservoir or heat exchanger mods
More to come as things change, arrive, and evolve.
What would you like to see tested on a Cadillac STS-V? If you have a performance product you would like to have independently tested on a Cadillac STS-V, please let me know.
