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May 30, 2007

The Best Sounding M3 in Michigan

Love it or hate, the E46 M3 BMW comes with a very distinctive mechanical sound straight from the factory. The so-called “rasp” actually comes from the engine and not the exhaust as so many people think. Nonetheless there are all sorts of exhaust “rasp eliminators” on the market today with a few actually doing a pretty good job of muffling the distinctive S54 engine note. But none of them add to the performance of the car.

At VRPerformance, we’re more interested in objective matters-- things that make the car perform better. So when we analyze an exhaust system, we’re looking at better flow with just the right amount of back pressure, the exhaust note is a by-product.

The OEM headers are surprisingly restrictive (bulges are the primary cats)

When we’re lucky, a system improves the objective of increased performance and the subjective sound of the exhaust. And that’s exactly what we have in this case study.

We installed a complete Supersprint exhaust system, front to rear, including long tube stepped headers, race catalytic converters, mid-pipe, and race mufflers. Along with an aFe cold air intake and updated software, we’re looking at a 10% increase in power output—which, on a normally aspirated engine that is already in such a high state of tune from BMW, is excellent.

Supesprint headers and race cats

Two sets of pre and post cat O2 sensors-- with some tricky re-routing, some of the cables can be re-used without splicing. We had to lengthen one set.

Nice tight fit, but it works.

Here you can see two things: one, how poorly separate components can fit sometimes (requiring a bit of "tweaking") and two, the density of the race cat honeycomb.

A nice view of the completed system.

Installing a complete exhaust system like this is next to impossible without a lift and a good set of tools. As is typical with aftermarket kits, some cutting, bending, shaving and general tweaking is required. But for most enthusiasts, the end result is worth the time and cost.

New Video:

May 20, 2007

Take the 959 to Dakar

What to do on a lazy, cold and wet Michigan Sunday afternoon? Cruise the web for some interesting video, that's what.

Before Porsche became the all conquering fashion statement for the gold chain rich and famous set, it produced some real four wheeled engineering marvels. The Porsche 959 shares top shelf space in my hierarchy of great cars along with the McLaren F1.

Even more impressive than the street car is the Paris to Dakar Rallye race car. Enjoy.

May 19, 2007


I'm in the middle of working on an article about so-called "car films" and came across the famous chase scene from Steve McQueen's Bullitt posted over on Google Videos.

Bullitt is a murky police drama that starred McQueen as a gutsy, no frills San Francisco cop assigned to guard a mafia informant. The real stars of the film of course are the green 1968 Ford Mustang driven by McQueen and the black 1968 Dodge Charger R/T of the “bad guys”. Thanks to McQueen’s attention to realism, the 7 minute chase scene between these two cars is still one of the best. Just the sound of the two V8s under full throttle makes for great entertainment.

Well worth a few minutes of your time if you have not seen it lately:

May 11, 2007

The Cannonball One Lap of America

Long before there were rallies like this year's ill fated Gumball 3000, or the Bullrun, there was the Cannonball Baker Sea to Shining Sea Memorial Trophy Dash-- the Cannonball Run. A stick in the eye of the 55 mph national speed limit, it was an event designed to prove that one could traverse this great nation at extra-legal speeds in comfort and safety.

The 1970s era Cannonball Run was instigated by automotive rancantour Brock Yates. It was a balls out race against time from New York City to Redondo Beach, California. After 5 races without incident, Brock Yates decided he proved his point and set about creating a new-- totally legal-- event.

The first Cannonball One Lap of America was run in 1984. The format has changed over the years a few times before settling on the current formula of timed events at race tracks http://www.onelapofamerica.com/about/index.shtml?about=pastTracks around the country.

I ran in the One Lap with my brother 3 years, 1995, 96 and 97. It was gruelling-- driving on average 1000 miles per day for one week-- but great fun. This year's event started May 5th at the Tirerack HQ in South Bend, Indiana and will end back there May 12th.

Here are a couple of great websites about the event to check out:

May 09, 2007

Braking News

We all know brakes are a very critical system on your car, but few of us have a strong understanding of what a braking system consists of and how it works. We’re going to go through the basic components of these systems and give you a better understanding how they all work together.


First thing we’re all familiar with is the brake pedal. We all know that you push the pedal and the car slows down. What is happening (behind the dashboard) is the pedal is attached to an arm that has leverage about a fulcrum pushing on a rod connected to a piston. This piston is located in the master cylinder and the cylinder is filled with brake fluid and pressurized by the piston. The pressure is then split between the front and rear brake lines in what is essentially a pressure regulator. The reason for this is more pressure is sent to the front than the rear because of the weight of the car – more accurately the weight transfer. As a car slows down, weight is transferred to the front tires giving them more grip than the rear. This increased grip allows a higher percentage of the brake force to be generated by the front tires compared to the rear.

The brake fluid flows through a tube (or brake line) under pressure actuating a piston that is located inside the brake caliper. When there is line pressure this piston pushes on the brake pads which in turn push on the brake disk (or rotor). When the pads contact the disk it generates friction between the two surfaces causing the disk to slow down. The byproduct of this friction is heat, sometimes extreme. To dissipate the heat there are vents in the rotors and they look like little webs between the two rotor surfaces. These vents essentially pump air through the webs from the inside out when rotating. Race cars often put flexible air ducts from an inlet on the front of the car to the rotor giving a better supply of cool air. Due to the high temperatures these components are subjected to a good boil resistant brake fluid is necessary. This fluid should be bled or changed regularly-- more frequently with aggressive use.


Rotors have been developed significantly through racing and the technology is readily available for the street. To better deal with the heat generated by repeated use, rotors have taken on a two piece construction. The rotor is separate from the center portion commonly known as the hat which connects the rotor to the hub and wheel. The hat is usually made from aluminum while the rotor is often cast iron. These two components are attached together with small bolts. The main benefit of having a two piece (or floating) rotor is that it allows the rotor to expand and contract with the change in temperature which significantly reduces warping tendencies of solid one piece rotors. The attachment holes that the bolts go through are slightly oval in shape and this allows the rotor grow in diameter. These attachments also give the rotor the ability to move slightly in and out from a cross car perspective. Springs are sometime used to keep the rotor from moving too freely which can generate noise.

Holes and Grooves

Another detail of rotors is the holes (a.k.a. cross drilled) or grooves (a.k.a. slotted) in the friction surface itself. Cross drilled rotor holes go all the way through the rotor while a slotted rotor has grooves cut partially into the surface in a variety of different patterns. Cross drilled and slotted rotors are effective because these features allow the gasses generated to escape from between the pad and rotor. Gas generation is normal when the pad material is ground off against the rotor. The problem with not allowing these gasses an escape route is they will actually cause the pads to float slightly on the rotor not unlike an air hockey puck. These features also help a similar case where if the brake system is wet it gives the water a place to go allowing optimal performance of the brake system.


Moving on to brake calipers there are two basic kinds - floating and fixed. Floating calipers go with fixed rotors while fixed calipers go with floating rotors. A floating caliper typically has just one large piston located on the inboard side of the caliper and a structure that wraps around the rotor allowing it to retain two pads. This style of caliper is floating because it is able to move in a cross car direction with the application of the brakes and also to adjust as the pads wear down. It is strong, effective and less expensive to produce than a fixed caliper.

The fixed caliper’s body does not move just its piston move to push the pads to the rotor. The designs do vary, but the most common type is a 4 piston set up whereby two pairs of horizontally opposed pistons provide the pushing force of the pads to the rotor. These caliper structures are designed to be strong to withstand high pressure, better dissipate heat and high overall brake performance. Another term you might hear is “monoblock” and this means the caliper is machined from a solid billet of aluminum. This is beneficial because it is the best combination of weight and strength while avoiding the seam whereby two halves are bolted together as with most fixed calipers. Race cars often use monoblocks, but they are more expensive due to the added machining time. The pistons are also important in how they are sized for the weight of the car and master cylinder.


Pads are an important part of the equation too. They have a significant impact on the systems overall performance because they can be made from a number of different compounds all designed to give different levels of friction and longevity. Pads for a street car would likely target low noise, good friction properties and longevity. On the other hand a track pad may have no noise considerations, high friction properties and depending on the length of the race, longevity may be a few hours. Brake pad dust is another thing that street pads try and minimize, but we’ve all cleaned wheels to find out it doesn’t last as long as we would like.


One last thing I want to bring up is brake lines. Not the main lines running from the master cylinder to each corner of your car, but the reinforced rubber lines that run the short distance from where the steel line terminates to the caliper fluid inlet. Due to suspension movement these cannot be hard lines. One popular upgrade for those going to the track is the replacement of the rubber lines with braided stainless steel lines. These are stronger; reducing the expansion of the line as pressure goes up in the system. This stronger line improves pedal modulation and feel.