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I think I know what you are asking.
The engine design really contributes the most to the feel of it when considering engine performance. Automakers balance many factors: performance, emissions, economy, noise, packaging, and above all COST.
The late 240 engine is a wonderful thing. It offered sufficient power for the application, near bulletproof reliability, reasonable economy, and it was fairly cheap and simple to build.
One thing to understand is that it's a 4-cylinder inline engine. This results in certain vibration and roughness issues at certain RPMs. All manufacturers deal with this to some extent, as this design is used by many companies.
The cylinder head design is the biggest deciding factor in engine "feel". Honda and similar designers often build wonderful engines that make power at high RPMs. These are often multi-valve configurations. In many of these designs, the engine sacrifices low-end torque for a very high specific output at upper RPMs. Great for a motorcycle, or a light, performance oriented car. Not so desirable in a family sedan. The automotive press cited the Acura models early on, for being SO strong top end, that they felt anemic at low speeds. Obviously a matter of perception and a balance of matching performance and vehicle/people needs.
The B21/23/230 cylinder head design is fairly modern but very straightforward. It was designed to control emissions and give good low speed power with either auto or manual transmissions. Automatics really require more low end than manuals. Volvo's engine made more torque than many comparable size engines, but less horsepower. This has a lot to do with cam profile. The stock "M" or "T" cams fitted to these engines (in the US) really have a lot of compromises built into them. Most notably, power falls off drastically at 5000-5500 rpm. The engine simply can't breathe. This is why a performance cam, such as a KG Trimning unit or IPD or a VX grind offers such an improvement in engine feel for the performance-minded.
It's instructive to look at the design Volvo chose (with design guidance from Porsche, by the way) for the aluminum engines. First and foremost, cost considerations appear, and it's not a bad thing: the engines are built in 4-cyl (1.9), 5-cyl (2.3 & 2.4), and 6-cyl designs (2.9). They have the same front engine casting with the seals, water pump, and oil pump; they use the same rear casting with rear main seal, bearings, bell housing design. In between, the engines can be machined on the same equipment, saving costs. Obviously the 4-5-6 arrangements require different cams, cranks, and blocks, but all the pistons, valves, little pieces interchange.
The engine is a very long stroke design, giving reasonable low-end torque. It has a fully modern double-overhead-cam cylinder head, with 4 valves per cylinder, giving free breathing and the potential for great power at high revs. It's a very versatile engine and worth a test drive if you haven't. The more common 5-cylinder has a bit of a weird growl to it, unlike most other cars due to the unique firing order. Combined with the ability now to fit variable (hydraulically controlled) valve timing, these engines eliminate a lot of the compromises of earlier, simpler designs.
Hope that helps explain some of the tech behind the seat-of-the-pants feel of your car.
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Rob Bareiss, New London CT ::: 87 244DL, 88 245DL, 90 745GL, 84 242DL project, 89 244 parts, 88 244DL to replace the 87
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