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Stephen's list of engine differences is spot on - the B235 engines in the 9-5 are nearly identical to the B234 engines in the 9000 cars - which seem to be more robust. The B235 was slimmed down for better fuel economy and quicker response, and there are some other differences.
(a lot of this info comes from some of the other SAAB forums where the posters do a little more of the down and dirty, and for that matter it's usually people with the older models finding this stuff out and hobbling these fixes together)
The engine oil will start to sludge up above a certain temperature, the B235 has two very efficient catalytic converters, with one nestled right up against the oil pan, that puts a LOT of heat into the oil.
- The B235 has significantly lighter pistons and connecting rods than the B234 in the 9000, so an AFR issue is more likely to overheat the 9-5 pistons and cause problems. (The thinner pistons along with lower tension rings work against preventing oil slidge, because the lighter shorter pistons won't transfer heat into the cylinder walls through the piston skirts as effectively as the taller more massive B234 pistons, so when the oil squirter jets spray up on the bottom of the pistons they can be hot enough under hard driving to start the sludging process.)
- B235's got much more efficient turbos
- B235's got much better flowing cylinder heads (but milder cams to keep emissions down)
- T7 is a much much faster system than T5, and is much better at producing it's rated torque output by varying timing and keeping to the output map of the engine rather than 'reacting; to the fuel injection inputs like the T5 uses, so it can make do with the milder cams.
- The fuel injection scheme is completely different - 9000's don't have air mass meters at all, they use a different set of input to control how much fuel is injected. The T7 system in the 9-5's primary input for mixture control is the air mass meter, and so it MUST be within spec to expect lots of engine longevity. For those with heavily tuned cars the MAF is often considered a scheduled maintenance item along with plugs and DI cassettes and is just changed at a certain mileage (the DI cassette was originally desinged to be a 'lifetime-of-the-car' component, and that didn't work out either, did it?
*******Go read the 9-3 or performance forums for what 9-3 and Viggen owners do for maintenance, lots of people will put a bit of a regimen into 100k mi. plus cars they buy of plugs, DI cassette, air mass meter, fuel filter, engine oil change, regardless of how the car seems like it was treated. If you're interested in keeping the car for a long time and it's been a while since any of those things, you might want to consider them.
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Basically, this boils down to the engine not being as overbuilt as earlier SAAB engines (the B20/H201/B201/B202 engine series from the 99 and 900 was co-designed with diesel engineers from Scania, who only know anything about truck engines - the old C900 turbo engines LOOK like diesel engines inside, but really beefy pistons, huge rods, and very wide cylinder bore spacing for how small the bore is).
In the modification community we take a few of the weak points out of the 9-3/9-5 engines for heavy modification in a really easy way - FIT RODS AND PISTONS FROM A '94-'98 9000!
The crankshafts for the 9000 and the B235 9-5's are essentially identical, the rod and main bearings are identical, and the end covers are essentially identical, so you can just get a beefy set of the 9000 rods, and a set of new OEM or aftermarket pistons meant for a 9000 and throw them in your 9-5 the next time the head is off for a cyl. head gasket, and you can replace the rod and main bearings at the same time.
Or go a step even more budget oriented that is becoming popular-
- ...The B234 block is identical to the B235 block (up through 2003 anyway, but it will work in '04 up also, there are only a few tiny differences), you can put a whole 9000 B234 engine in your 9-5, which will come with the better nitriding and hardening on the earlier crankshafts - the 9000 cranks rarely need re-surfaced, and if you do you cut right through the induction hardened bearing surface, and then you have to get it re-hardened and finish ground. Besides, a good engine shop will be able to spec you bearings that are 0.0005"-0.0010" undersize to make up the difference.
Anyway.... that became long. Some ideas.
Best,
Drew
, Mon, 17 May 2010 15:01:29
, Thu, 13 May 2010 10:12:22, Thu, 13 May 2010 05:56:58
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