Project BMW Z4 M - Part 6 - European Car Magazine

Before we close the book on this series, or decide to go off on some crazy tangent like pulling the trigger on a warranty-blowing power upgrade--interesting thought--we recently performed an additional test that you may have a great deal of interest in.

Most car enthusiasts will participate in driver's schools and track days--I'm totally hooked myself. If your days at the track exceed three or four per season you probably want to purchase a set of dedicated wheels and tires so you can save your expensive street tires for everyday use. Of course, the other reason is to improve hot grip to get through the corners more quickly. Nitto Tire provided Project Z4 M with a set of NT01 DOT-legal, R-compound road racing tires, sized 245/40ZR18 for the front and 275/35ZR18 out back.

The NT01 is designed with an asymmetrical, non-directional tread pattern for easy rotation on either standard or staggered setups, and it has an extremely large outer shoulder to maximize the contact patch under heavy cornering. Nitto manufactures this tire with a high modulus rayon carcass and body ply construction for maximum lateral and high-speed stability. Tread depth is 6/32 of an inch and it can be shaved to 3/32 to reveal a "slick" tread surface with two circumferential tread grooves. It also features a specially formulated rubber compound for hot on-track performance, which delivers extreme cornering grip for faster and more consistent lap times.

After putting in a couple of proper heat cycles a few days before, and sufficiently playing with the hot tire pressures (40 psi seemed to work best in our track conditions), we felt it was time to put the NT01 to the stopwatch by means of our Traqmate GPS acquisition system. As usual, we attempted to be as consistent as possible testing with similar weather conditions, the same driver, and no in-car time displays as we've done for all previous track tests. The NT01s proved themselves admirably throughout our testing under dry conditions. Turn-in and feedback were precise and reliable. Cornering grip was astounding, while at the same time their breakaway felt progressive and forgiving. They also exhibited excellent consistency throughout the day even as the track temperature fluctuated, and they did not get "greasy" toward the end of a longer session when hot tire pressures were properly managed. Lap times were 1.5 seconds faster at our two-mile test track than baseline laps run previously with the Nitto Invo street tires in the same sizes (88.05 seconds compared to 89.55). The figures to the right show a speed versus distance comparison of the NT01 and the Invo along with an accompanying cornering force versus distance plot. Higher corner speeds and greater cornering g-forces are prevalent with the NT01 R-compounds.

This project has really been all about the numbers. We swapped out carefully chosen aftermarket tires, wheels, brakes, suspension components, air filter, and the entire exhaust system, along with a front strut brace and a pair of front camber plates. Along the way we demonstrated these mods' efficacy through controlled GPS track testing, and on the dyno in some cases. We collected a mountain of numerical data, much of which we've shown throughout the series, and we've been rather pleased with and even surprised by the results.

The table on the next page shows the progression of decreasing lap times with each new modification. Note that we have also tracked the power gain at the wheels as well so we can easily point to where the added speed is coming from. Notably we were able to "double dip" with grip and power in Part 2 with our lightweight wheel and tire upgrade. It's also interesting to see that the final 29hp power upgrade didn't reduce lap times as much as the individual handling modifications. However, the increased power and low-end torque made the car much more lively in all conditions and is easily felt from the seat of the pants.

The summary velocity-versus-distance figure also shows our real-world performance progression at the track. Note that more confidence-inspiring upgrades (like better grip and brakes) are the ones that really count toward improving overall performance. What the numbers can't account for, though, is driver improvement over time by building experience with the Z4 M platform. While the test driver (yours truly) has some 10,000-plus laps at this track, there's some learning over the four month test period that cannot be accounted for with in our data. On the flip side, there's a lot that can be learned from the acquired GPS data. It looks as though faster laps could be possible by improving consistency, especially when late braking at high speed into Turn 1. My chicken wings are still flapping after an unexplained off during testing back in Part 3.

The Z4 M has responded well to modification, offered an exciting challenge at the track, provided excellent driver feedback and involvement, and remained refined as a daily driver too. But how good is it when compared to more expensive, OEM-plus hardware? We'll find out next time...

ProjectPorsche Cayman X51
Part 1: To dethrone a legendOn a bitter cold January day in central Alberta, Canada, a lone five-car transport arrives at Norden Autohaus to deliver its cargo. Batteries are re-connected and five frosty Porsches are started, carefully unloaded, and parked on the lot at this, the most northerly Porsche Dealer in North America. The Arctic Silver Cayman S in this elite group was ordered in late summer specifically as the subject of a brand-new project car series.

Being an iconic sports car's "little brother" has its drawbacks. We all know that Porsche AG is steadfast in its position to never dethrone the legendary and continuously evolving 911 as the company's top performer, and so the Cayman variants remain underpowered when they roll off the assembly line. This immediately slots the Cayman into the "lesser" category in terms of things that we can easily understand, with "cost" and "performance" at the top of the list. The fact that the Cayman is about 120 pounds lighter, with a more optimally balanced chassis due to its mid-engine layout, is, unfortunately, irrelevant. So too is the fact that the two-seat Cayman is gorgeous to look at in the flesh, with flowing lines and curves and a definite lineage from both 911 and Boxster.

Purists and wealthy poseurs alike will always give the nod to the 911 because it's the top-of-the-line--911, there is no substitute! Behind the Cayman's wheel, though, you'll experience excellent feedback and nimbleness, a compliant ride, superb brakes, good power, and an intoxicating exhaust note. Its sporty interior also speaks of high quality in both form and function, and provides many of the same creature comforts as its brother. So what's wrong with the Cayman? Really, nothing at all. The only complaint could be that it is perhaps too refined, that is, it could really use a bit of the old je ne sais pas--rawness, quirkiness--that made Porsche famous in the first place.

We've seen pumped-up Caymans from Ruf with a 400hp supercharged engines, and from Farnbacher Loles with a 997S X51 engine also claiming 400 hp, in these very pages (December and January '07, respectively). That's all good, but what we really wanted to do with this project was to build one ourselves with the help of some local grassroots expertise, then perform some real-world, side-by-side comparisons with the Cayman's iconic sibling. This would determine the true feasibility of a Cayman performance upgrade. Will we create a 911 killer, or just a faster, more expensive Cayman?

If at this point you're thinking this sounds more like a science project, well, you'd be right.

After a great deal of research, the car's owner decided that the 997S X51 engine swap was most fitting for his goal of a turning a stock Cayman S into the ultimate street-worthy track car. He also wants to keep it serviceable at the dealer by including as many original factory parts as possible. And we'll require a great deal of technical of help. Fortunately, Norden Autohaus of Edmonton has an internal tuning arm, Norden Performance, with many key corporate alliances within the Porsche tuning aftermarket. More importantly, Norden Performance has full access to all in-house Porsche technicians. These talented guys will be doing the bulk of the work.

The series will progress thusly. Part two will include all aspects of the Porsche-to-Porsche engine swap. Part three will discuss preparation for the track and initial testing. And part four will be the full feature-length final test, when we put our "science project" up against the legend in an on-track shoot-out. I promise you won't want to miss it.