Last month, we embarked on the first of the power pursuits for our 2011 BMW M3 with Competition Package. As you may know, in previous issues we installed carbon exterior and interior parts, H&R springs, Forgestar wheels, Conti tires and Brembo brakes. In the 3/11 issue, we made our first visit to the dyno to test a cat-back exhaust and cold-air intake from Advanced Flow Engineering – an American company that specializes in truck and BMW applications.
Despite good looks, improved flow, entertaining noise and affordable prices, the parts came up short, unable to provide the promised power. As we stated, this could have been related to a dyno problem, but we’ll wait to see how it turns out.
In the meantime, we were approached by GruppeM North America. As its name suggests, it’s the US distributor for the Japanese company renowned for its high quality carbon fiber intakes, and now titanium exhaust systems.
As you’ll see from our photos, the GruppeM (GpM) pieces are exquisitely manufactured but it’s reflected in the price. The M3 intake and exhaust we’ve installed will cost you about $8700, for example. Fortunately, fitting is straightforward and potentially a DIY undertaking if you have access to a lift for the exhaust.
At these prices, you’re naturally going to want to see some power, so we visited DC Performance in Culver City, CA to dyno the car. The company specializes in Dodge Viper tuning as well as dyno tuning and diagnostics (see sidebar). They have two dynos, expert staff and a great deal of patience – as we discovered!
Step one was to obtain a benchmark for our stock M3. We had removed the aFe components to give GruppeM a fair start. On the aFe Mustang dyno, the stock car delivered 287whp and 216 lb/ft of torque. However, DC’s Dynojet rollers recorded initial figures of 341.hp at the wheels and 251.5 lb-ft of torque.
This represents a substantial disparity that can partially be explained by the type of dyno used (Mustangs read notoriously low), as well as the six gallons of 100-octane fuel we’d added before these latest runs.
The race fuel was used at the request of our Tech Editor, Paul Piola, who was helping with the test. He used an Actron CP9185 Elite AutoScanner to monitor ignition timing, water temp and intake air temp via the OBD2 port, as well as oil temp via the in-dash gauge. Having conducted hundreds of dyno tests, he knew it was important to keep all the parameters consistent, and the race fuel would be more resistant to the ignition retarding as the engine got hot. Whereas, weaker 91-octane pump fuel is more likely to cause knocking as the temps rise.
It should be stated that the fuel was added before the test and remained throughout the three dyno sessions that day. All the temps and timing were kept consistent, and the numbers recorded only when the parameters were at the original settings taken on the first runs. This consistency represents the power added by the new components, rather than what happens when an engine gets hot.
In other words, it wasn’t done to cheat the numbers, but to make them accurate and consistent.
|ram air system||GruppeM||$3162.40|
We’d seen several GruppeM intakes before, but holding one in your hands is a different experience. You can examine the parts in detail and see how expertly they been designed and assembled. The combination of wet and dry carbon manufacturing, as well as aluminum and titanium hardware means they meet the highest standards. Being so light and almost paper-thin, the parts feel fragile, yet are obviously able to deal with the stresses put upon them. Color instructions are provided to take you through the major steps and, if you can build Ikea furniture, you should be able to do this.
The original plastic airbox and paper filter is discarded for a carbon heat shield with a K&N cone filter that’s claimed to increase airflow velocity.
Intake air is drawn from the same three places as stock – the hood vent, front grille and driver’s side brake duct. Each of these scoops is very similar to the stock pieces, although they look significantly better. We were slightly concerned by the extension of the brake duct insert, which directs air higher into the engine bay, possibly robbing our six-piston Brembos of some cooling capacity. However, we haven’t yet noticed a problem on the road.
The TIG-welded titanium cat-back GruppeM exhaust is one of the nicest we’ve ever seen. The quality of the welds and bends was unsurpassed and certainly helped justify the price.
Using 70mm (2.75") pipe, it has two mufflers with a crossover pipe, rather than the bulky suitcase muffler fitted as stock. At the back are four 80mm (3.15") shot-peened tailpipes that stick out from the bumper more than we’d expected. However, thanks to its titanium construction, the entire system weighs just 25 lb, compared to the 54 lb OE part – a significant saving!
Brackets are provided so the factory hardware can be mounted to the mufflers, although the center hangers on the OE system aren’t used by GpM, possibly because of the low weight.
This makes fitting a breeze, provided you have a lift. The only obstacle is removing the stock hanging rubber but some lubricant and a pry bar soon had them off.
With more than $8.7k in parts, we were heavily invested in the results. So with the intake installed, the car returned to the dyno for its next session. A number of runs were conducted to get the operating temps where they were before. Once warm, we were glad to see the graphs going up. Our preferred run showed 348.4whp and 254.3 lb-ft, an increase of 6.6hp and 3 lb-ft at peak respectively. The numbers under the curve were slightly better too, showing good gains from 5500-6700rpm and again from 7000-8200rpm, with a maximum gain of 10.5whp and 7.1 lb-ft at 7750rpm.
With the exhaust fitted, we were hopeful for more improvement and weren’t disappointed. Admittedly, power only rose 3hp to 351.3whp and torque grew 2 lb-ft to 256, but it was still moving in the right direction. And this time the gains in torque were lower down, giving us a little more tractability. In fact, the best numbers were 4.3whp and 3.6 lb-ft at 6330rpm. But remember, this was in addition to the intake numbers.
By looking at acceleration on the dyno, we were able to calculate the performance increase from 3000-8250rpm in fourth gear. The stock M3 did it in 8.91sec, whereas it took 8.74sec with the intake fitted, and 8.61sec with the exhaust. So we gained 0.3sec acceleration in-gear.
On the road
Comparing GruppeM to the aFe system, it gains in several key areas. Firstly, it’s significantly quieter, particularly at idle and low RPM where the aFe would drone. The GpM offers a deep note, but only slightly more so than stock.
At high RPM, the new system comes on song, giving it a distinct V8 howl, especially if you jump on the throttle. In fact, it sounds pretty good.
What’s more, the engine seems smoother than before. It could also be more spritely, although we’re hard-pressed to detect the extra 14hp under the right foot, but it’s nice to know it’s there…
Is this exhaust and intake worth almost three times the price of the aFe components? That’s a hard question to answer, and down to the individual owner. But at least we’re now headed in the right direction and they do look superb.
Modifications To Date
|carbon dash & door trim||BMW Performance||10/10|
|black kidney grilles||BMW Performance||10/10|
|carbon mirrors||BMW Performance||10/10|
|carbon kidney grilles||Turner Motorsport||10/10|
|carbon hood vents||Turner Motorsport||10/10|
|carbon side vents||Turner Motorsport||10/10|
|wheel spacers||Turner Motorsport||10/10|
|longer wheel bolts||Turner Motorsport||10/10|
|Gran Turismo brake kit||Brembo||11/10|
|carbon door trims||BMW Performance||12/10|
|carbon front splitters||BMW Performance||12/10|
|carbon trunk spoiler||BMW Performance||12/10|
|19" F14 wheels||Forgestar||1/11|
|ContiSportContact 3||Continental Tires||1/11|
In part seven of our M3 makeover, we’re trying to decide whether to test the new exhaust from BMW Performance, dyno some engine software or use Turner Motorsport’s downpipes, exhaust and software…