Full exhaust system for BMW Z4 28i


The development of the exhaust system for the Z4 E89 28i has come to an end.

This car is equipped with a 2.0 4 cylinder turbo engine, even if the name may make you think of a 2.800 cc 6 cylinder.

The name of the engine is N20 TwinPower Turbo and may make you think it's a twin turbo, but the "twin" word is connected to the "twin scroll" technology, with two separated manifold that enter the turbo charger, one for the cylinder 1 and 4, the other for 2 and 3.
This type of turbocharger has reduced lag, and brings a power delivery similar to a bigger NA engine.

This engine is also equipped with High Precision Direct Fuel Injection, dual Vanos (variable valve timing on intake and exhaust valves) and Valvetronic (electronic control of the lift of the single valves, makes possibile to control the engine without the use of the throttle body).

The results of tech parade is an engine that merges the compactness, the lightness and the lower fuel consumption of a 4 cylinder with the power and torque of a bigger displacement engine.
This are the claimed figures:
Horsepower 242 Hp @ 5000~6500 rpm
Torque 350 Nm @ 1250~4800 rpm

Our dyno testing of the car in stock configuration confirmed these values:

The vibrations, increased from the naturally balanced 6 cylinder engines of the previous models, have been compensated with two balance shafts, placed in different locations, while a centrifugal pendulum integrated in the dual-mass flywheel tames the engine in the very low rpm range.

Sadly, the price to pay is the loss of the classic 6 cylinder BMW sound.
The sound is quite disappointing. From the engine bay come the ticking noise of the direct injection, and the exhaust note is quite impersonal, audible only when driving aggressively, when the bypass valve on the rear exhaust opens.

Another "issue" is the extremely high temperature reached by the exhaust gasses. The  ceramic catalytic converter right after the turbocharger irradiates huge amount of heat in the engine bay, and it's an obstacle to the gas flow.

The development of the exhaust system was focused on getting a much better sound to the Z3, bringing back the sportiness lost with this engine, on increasing the efficiency, to reduce the thermal and mechanical stress on the engine, and on increasing the performance.

The same engine of this car is also fitted to X1, 125i F20, 328i F30, 528i F10.
For the 1 and 3 series the full exhaust system development is planned and will be available later this year.

The system is composed by:

987121: downpipe with HJS metallic cat, allows for better flow, optimal dejection of pollutant substances and better durability to extreme temperatures.
The entry pipe is 90mm, the cat has generous dimensions, with 130mm of diameter. The flex joint is the best available on the market

It's also available a decat downpipe (987111)

987102: front exhaust, with direct flow silencer and the usual Supersprint qualities.
The entry pipe is 70mm, the two exits are 54-

It's also available a pipe only version, which in exchange for a slight comfort loss brings a more aggressive tone (987112)

987113: Centre Y-Pipe, with exit diameter brought back to 70mm.

987106: E.E.C. homologated muffler, again with a direct flow silencer. The chosen endpipes are 80mm, slash cut and  lipped, and fill perfectly the bumper arch,

The dyno results of this system, development for the best efficiency, are very good:

The comparison chart shows clearly the improvement:

Aside from the max power, that goes from 243 to 252 cv, the gains are:
+13,2 hp @ 2700 rpm
+15 hp @ 4300
+23,4 hp @ 6600 rpm

The torque gains are:
+41,1 nm @ 2000 rpm
+24,4 nm @ 4300 rpm
+26,2 nm @ 5900 rpm

The real life driving feeling is a more meaty low and medium rev range, with a much more convincing top end.

Sound-wise, the difference is huge. The low end has a deep, growly tone, and it becomes more aggressive ascending the rev counter, with nice lift-off pops.

For more info, prices, pictures please go to the specific model page:

BMW E89 Z4 328i --> http://www.supersprint.com/en/prod-7023-11771-bmw_e89_z4_28i_n20_20l_4_cil_turbo_2011_E28093E280BA.aspx

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