The B204 engine was designed on the basis of the first Saab 2.3-liter B234 engine, which appeared on cars back in 1989 and in some details was compatible with the old B202 engine.
The 2-liter B204 unit debuted on the second-generation Saab 900 in 1994 (at the same time the B234 engine was seriously upgraded). The two-liter is essentially a “shortened” version of the 2.3-liter engine: the stroke of the pistons is reduced from 90 mm to 78. We should add that the blocks of these engines stand vertically under the hood, while all their predecessors were installed at an incline, as if half of a V-shaped block.
The 2-liter engine was produced until 2002 and was available in both a single atmospheric version and two turbocharged versions. Just such an engine – B204E with a low-pressure turbine we will take apart. This engine was removed from the Saab 9-3 (restyled 900 second generation) 2001 with a mileage of 200,000 km.
The turbine in this engine “blows” 0.4 bar, the power unit produces 155 hp and 219 Nm. A more powerful version (B204L), in which the supercharger pressure is 0.73 bar, develops 185 hp and 263 Nm. There was also a 200 hp B204R, with a turbo blowing at 1 bar.
All turbocharged Saab engines of this generation were equipped with an ignition system with individual coils for each plug. The engine is controlled by a Trionic5 ECU of its own Swedish design.
Reliability of the Saab 2.0T (B204) engine.
This engine is very reliable and hardy. And is an object of tuning. It is widely used as a basis for racing cars, removed under 700 hp on the standard block. Blow turbines under 3 bars. Swedish engine Saab B204 as an inexpensive, but very worthy donor is put not only on projects on the basis of Saabs, but also on the basis of various old Opel, and even Daewoo Lanos and Mazda RX-8. In general, this Swedish engine due to very strong block, hardy piston group and well thought-out lubrication system among connoisseurs competes with legendary Japanese motors.
Trionic control unit
In 1993, the Bosch Jetronic unit was replaced by the Trionic 5 control unit on Saab turbo engines. The block is very advanced, it “sees” detonation by ionization in the combustion chambers, controls injection and turbine performance.
In addition, this block is quite easy to program – re-flashed with modified firmware to increase power. It is said that turbocharged Saabs with stock firmware on the roads are a minority.
True, to increase the power of the 150-horsepower B204E turbo engine, it must be equipped with a supercharger control valve.
Ignition coils
On Saab engines, individual ignition coils are combined into so-called cassettes. These units run quite well, but can fail due to saving on spark plugs or “lighting” your car or another.
Cassettes use a capacitive charge to create a spark and are capable of collecting and transmitting combustion and detonation data to the Trionic control unit based on the ionization of gases in the combustion chambers.
The standard cassettes come in red and black color, physically they are fully compatible, the engine will be able to work with either of them. But by factory red cassette is used with Jetronic or Trionic 5 ECU, black cassette is used with Trionic 7. The red cassette is more expensive than the black one, so often owners are tempted and put the black one in its place. But this should not be done.
First of all, the black cassette gives a spark from AC, while the red cassette gives a spark from DC. Secondly, if you put the wrong cassette, the Trionic control unit will not be able to detect detonation and take measures to combat it. Practice shows that with the wrong cassette detonation can kill the engine literally in 5-10 km of active driving.
One of the important features of the Trionic ECU is its excellent work in preventing detonation. The unit flexibly adjusts mixture composition, ignition advance angle and limits boost pressure in order to keep the engine alive. By the way, such abilities make tuning a Saab engine easier.
Crankshaft position sensor
With a faulty crankshaft position sensor, the Saab B204 engine starts to stall as it warms up and won’t start. The same symptoms with lack of spark and fuel supply can be observed in extreme heat. When the engine cools down, it will start again.
Turbo
The two junior turbocharged variants of the B204 engine are “supercharged” with a Garrett TB25 turbine.
The 200 hp B204R engine is fitted with a Mitsubishi TD04L turbine.
Supercharger control valve
Back in 1982, Saab turbo engines were equipped with a special valve that allows flexible control of the supercharger. According to the company terminology it is called APC (Automatic Performance Control). It is also called BPC (Boost Pressure Control) or simply “N75 valve”.
B204 engines with more than 185 hp have APC valve, less powerful engines do not have it. This valve controls turbine output and boost pressure by command of the control unit.
This valve is connected by three pipes to the bypass valve (outlet W), the “cold” volute (outlet C) and the intake manifold up to the compressor (outlet R).
Balancer shafts
The balancer shafts and their chain drive on the B204 engine are the only weak point in the mechanics of the engine. The balancer drive chain wears out in 100,000 to 150,000 kilometers. It starts to rattle. In addition, the liners on which the shafts rotate also wear out, and scoring occurs on the balancer journals.
Balancer shafts are needed to balance the second-order forces of inertia. Many 4-cylinder engines have no balancers at all.
Therefore, there are several opinions on balancer maintenance on the B204 (and B234) engine. Somebody puts in a rebuild kit. And someone throws out the balancers, their chain and its tensioner, muffles the oil channels of the shafts and tensioner. According to reviews, only the 2.3-liter motor after this begins to run at idle with more noticeable vibrations. Many notice that the engine without balancers begins to “spin” easier. Also, when tuning the Saab B204 engine, the balancers are always gotten rid of.
Transmission timing chain
The timing chain is quite survivable and can serve up to 300 thousand kilometers of mileage. When stretched, it emits a characteristic metallic rustle. In the replacement of the timing chain on the Saab B204 engine is quite inexpensive.
Oil pump
The oil pump of the Saab B204 engine needs revision on occasion – there is often a depletion between its gears and the housing, which significantly reduces its performance.
C connecting rod covers
Rarely, but it happens that the life of the B204 engine ends with a wedge due to the fact that the connecting rod caps simply unscrew. This is, of course, nonsense, but such cases are known.