Tedjs recently took us on a brief tour of the fuel injection system on the 2.8 V6 that powers the Saab 9-3 Aero. This time, he’s giving us a closer, more in depth look as he slowly takes a bit more of this engine apart.
TedJS is a GM World Class Technician and professorial type at Tri-C – a community college in Ohio.
Many thanks, Ted. These inside looks have been fantastic.
Click to enlarge.
The Saab version of the (GM) high feature V6 engine uses a fairly common DOHC setup with one camshaft actuating the intake valves and one actuating the exhaust valves. An advantage of a DOHC cam setup is that allows the use of a ‘Pentroof’ style combustion chamber in which the sparkplug is centrally located in the center of the combustion chamber which results in a more complete burn of the air/fuel mixture. The other advantage is that is helps to reduce the valvetrain mass (in comparison to pushrod setup) by having the camshaft essentially actuate each valve by acting right on or near the valve itself.
The spark plug is centrally located in-between the two intake and exhaust valves. You can see the bee-hive style variable rate valve springs as well as roller followers in contact with the camshaft that open and close the valve:
Here is a Pentroof combustion chamber (had to borrow that photo from the General as I did not have the heads of this one just yet). That is direct injected Ecotec and you can see the injector peeking in the combustion chamber.
The intake ports that are part of the cylinder head on the B284L are rather large in comparison to what you would see (or if you have seen) a normally aspirated engine. Normally, larger intake ports such as this do not promote the efficient movement of air at lower engine speeds and result in undesirable idle characteristics. Two things work in the favor of this engine that permit the use of larger ports: Turbocharging and variable (intake only) cam phasing.
There are the chain driven dual overhead cams on the engine. You can see that the intake cam sprocket is different than the exhaust in that it uses a cam phaser or camshaft actuator. This permits the engine controller to continually vary intake camshaft angle (in degrees) relative to crankshaft position or what might be better thought of as piston position. Turbo X aficionados take note! The V6 engine shown on the Saab site and in the Turbo X brochure shows cam phasing on both sprockets – I suspect you are looking at the 3.6L version of the engine.
A close-up view of the intake cam sprocket and camshaft actuator solenoid and sensor. The actuator solenoid uses pressurized engine oil to move the cam phaser and the cam sensor tells the ECM ‘where’ the cam is in relation to crank position. This also lets the ECM know if the cam has moved the commanded number of degrees and set a DTC if it has not.
The larger part is the cam phaser actuator. The ECM can control how much oil pressure flows through this part and move the camshaft via that actuator on the gear. The sensor is a simple hall-effect or digital sensor that ‘reads’ the reluctor wheel built into the cam sprocket.
Some more detail on the camshaft with the ‘bearing’ cap removed. You can better see where the oil flows through the intake cam passage on the camshaft in this view.
One more shot of the intake cam phaser. One other thing worth of note is the roller chain which is the preferred design for strength. There are three timing chains on the engine and we just get to see one here.
Here is another view of the engine and some things worthy of note: The two lines are routed to the turbocharger. One carries pressurized oil and the other carries coolant. Near the bottom left is where two hoses would go to complete the circuit on the integral coolant warmer and oil cooler. The coolant reaches operating temperature much faster than the oil so it helps to warm it up during cold start. After the engine is warm the coolant now ‘removes’ heat from the engine oil. Very innovative!
With exhaust manifold removed. Not much exciting going on at the exhaust ports but the heads are of note. They are made of 356-T6 aluminum which I have learned is a rather expensive grade of aluminum that is primarily used in high performance racing applications. Other versions of this engine (the 3.6L used on many GM products) do not use these heads most likely due to cost and they most likely generate less heat than the turbocharged unit.
A close-up shot of the heads. I love that they cast ‘Turbo’ right into them.
Casting and serial numbers on the block:
A few exhaust manifold shots. The manifolds are very short dual wall manifolds that speed up flow to the turbo.
That’s it as far as the engine has been disassembled at this point. Even though it is on a stand, given the fact it is full dressed there is a lot to take apart on that unit. Overall I have to say though – it is one sophisticated engine and not something that you would just want anyone digging into should it ever need any sort of repair, which it hopefully will not.