For years, Alfa's 60 degree V6 engine has been praised for its smoothness, sound, and lively performance. Alfisti are rarely the type to leave a good thing alone, however, and many have exerted considerable effort on wringing every last bit of horsepower out of this mill, often with excellent results.
One of the first places most people would look in the pursuit of performance is increased engine breathing through a less restrictive exhaust system. Several tubular header systems, from manufacturers such as Shankle (currently sold by AR Ricambi), ANSA, and International Auto Parts, exist to fill this need.
Tubular headers allow the 12 valve V6, as installed in the GTV6 and Milano/75 sedan, to breathe more freely than the stock cast iron exhaust manifold and down pipe system, thus making more power, especially at the top end.
However, users of these headers have long bemoaned the decreased ground clearance and problematic sealing of these systems.
When I heard of a V6 header system manufactured by CSC Marmitte of Italy that claimed to address some of these concerns, while still making substantial power gains, I decided to investigate.
This system, available through EB Spares of London, is a fully tubular exhaust system consisting of tubular manifolds and down pipes complete with flex pipes.
Since decreased emissions as well as increased performance was a main objective of my exhaust upgrade, I chose to pair the CSC Performance Manifold kit with dual Random Technology 8100 Series "Bullet" Catalytic Converters. These cats feature modern honeycomb-style free flow substrates and are only 4" in diameter, which allowed them to be installed in the stock location. According to their reputation, these are some of the most free flowing cats available.
The CSC system arrived from EB Spares in 4 days via US Postal delivery. It was extremely well packaged for transatlantic travel, with each piece individually shrink wrapped and sealed. The system showed high quality welds and attention to detail throughout. The mating surfaces were flat to the limits of my straight edge and all the mounting plates were quite thick and sturdy.
A few notable features include:
- Captive nuts welded to the manifolds to make bolting up the down pipes easier.
- The three primary pipes run side-by-side as they exit under the car. This greatly increases ground clearance compared with the more typical triangular configuration.
- The stainless steel flex pipes in each down pipe should cut down on vibration and stresses placed on the manifolds.
Overall, the system weighed in at 31.8 lbs, a notable improvement over the hefty stock cast manifolds and front pipe. The Random Technology cats only added 4 lbs per cat to this total, making this a fairly light weight system.
Fitting of the CSC system, although time consuming and sometimes frustrating, was a straight forward affair.
To ease the installation of the manifolds to the head, I opted to replace the stock lower bolts (3 per side) with studs obtained from Centerline Alfa Products. This allowed the manifolds to more easily mate to the head - on the passenger side at least. On the driver's side (LHD) there were several obstacles to a good fitment, including the fact that the power steering pump bracket fouled the runner for cylinder number 3, and the fact that the mounting holes on that runner needed to be enlarged as they were drilled slightly off. Once these issues were taken care of, installing both manifolds was a simple exercise in turning wrenches where space simply doesn't exist.
When mating the down pipes to the manifolds, EB Spares suggested I use exhaust cement as the kit is not supplied with gaskets for this joint. On the passenger side, this procedure again went smoothly. On the driver's side, a power steering hard line was, unfortunately, directly in the path the down pipe needed to take to reach the header and had to be temporarily moved.
Once both down pipes were firmly attached to the manifolds, I turned my attention to the joint between the down pipes and center muffler. I had been forewarned by a member of the GTV6.org discussion forum that the down pipes were too short to mate with the center muffler, and had purchased some short adapter tubes to make up the difference. However, I was not happy with this solution and vowed to have it remedied when my catalytic converters were installed.
For the installation of the converters, I consulted a highly regarded local custom exhaust shop. As maintaining ground clearance and heat protection were important, we decided to mount them directly below the stock heat shield. As an added bonus, this placement allowed the CSC flex pipes to be retained. The converters were mounted with bolt-on flanges at the front and rear. The rearmost flange mounted directly to the center muffler, eliminating the troublesome slip fit joints once and for all.
Upon firing the car up for the first time, one thing was immediately evident - the CSC system has a great sound to it, deep and bassy without being too loud or harsh. At low revs, the system burbles deeply then builds to a characteristic Alfa wails as the revs rise. In this application, mated to a stock center muffler and ANSA twin tip tailpipe, the sound is music to any Alfisti's ears.
An early test drive - with the headers but before the addition of the catalytic converters - revealed an engine with more torque and a greatly increased willingness to rev. Testing backed this up, showing a 13 rear wheel horse power (rwhp) gain over the baseline system (stock cast manifolds and Euro down pipes). The increase in power has made this 2.5L Milano a much livelier performer around town, and the added torque makes highway cruising and overtaking more effortless.
Installing the catalytic converters did nothing to muffle the beautiful sound of the system. Upon testing, we found this configuration produced 7 less peak rwhp than the CSC headers alone - still a 6 hp increase over the baseline system without cats. But, the numbers don't tell the whole story as the car feels extremely torquey and willing to pull well past redline. By introducing some backpressure, the converters may well have helped mid-range torque.
In short, this system has given the car a much appreciated boost and retains its performance advantage even with the addition of catalytic converters.