Remote-mount turbos. The concept flashed through my mind when I saw Honda had moved its exhaust manifolds to the back side of the engine in my 2001 Civic. Plop a turbo on the far side of the cat and you don't have to worry about firing it off in a timely manner to pass CARB requirements.
For me this was an idle, passing thought, but Rick Squires made the concept a reality and has a patent on the process to prove it. Squires Turbo Systems (STS) is developing remote-mount turbo systems that position the turbo in the space previously occupied by the muffler. The company's initial foray into the market will feature applications for 1999-and-up GM pickups and SUVs, 1993-and-up F-Bodies (Camaro and Firebird) with LT1 and LS1 V8s, 2000-and-up Toyota Tundra pickups with the 4.7-liter V8 and 1996-and-up Toyota Tacoma pickup trucks with a 3.4-liter V6.
Spool-up and turbo lag issues in regard to the length of the piping leading to and from the turbo will probably jump to the forefront of enthusiasts' minds. These issues aren't as critical as one may think.
From my viewpoint, turbo lag is a term used to describe turbo systems with poorly sized turbine housings and their consequent incorrectly sized turbine wheels and poor tuning. Or it could be a combination of the three at work simultaneously. The velocity of exhaust gas and the fact that the STS design features a good deal of straight pipe, coupled with what exhaust gas does when it enters a turbo, should help negate any "lag" in the system.
The conical shape of the passage from the turbine inlet flange to the turbine wheel dramatically increases the velocity of the gases, which is how a turbo can spin at speeds of 80,000 to 120,000 rpm. Engine size, the trim of the turbine wheel and the turbine housing's A/R have much more impact on spool-up characteristics than the amount of pipe between the engine and turbo.
On the cool side of the turbo, it's no secret that sharp bends in the pipe create a pressure drop and can hinder response. An intercooler also creates a pressure drop, but the added density and the accompanying increase in power potential make this compromise a no-brainer; dial-in more boost to regain the "dropped" pressure.
The STS system uses that long length of pipe as an advantage. Just as the exhaust pipes are HPC-coated to keep heat in, the intake pipes are HPC-coated to assist heat transfer out of the pipe. The pipe is the intercooler, and STS reports 52-percent efficiency in its CARB-legal systems. Finned tubes and inline intercoolers can be employed, but STS has seen favorable results with standard piping and the HPC coating.