Speed Battle on Wheels: BS106 Intercooler vs BH116 Non-Intercooler

Which bus would win in a race: the Daewoo BS106 equipped with an intercooler, or the BH116 premium seat model without an intercooler?

BS106 Intercooler VS BH116 Non-Intercooler Speed Comparison

This analysis was prepared by Mr. Lee Chul-Hyup, Assistant Manager at Daewoo Motor’s Commercial Vehicle Maintenance Team.

The engines mounted on Daewoo buses are products of Daewoo General Machinery (formerly Daewoo Heavy Industries). The turbo intercooler engine installed on the BS106 bus is called the DE12Ti, which is based on the DE12 engine. When a turbocharger is added, it is designated as the DE12T, and when both a turbocharger and an intercooler are added, it becomes the DE12Ti. Currently, due to environmental regulations on diesel emissions, the electronically controlled engine DE12TiS is used. Therefore, all buses produced today are equipped with DE12TiS engines upon delivery.

Of course, this applies to the engine models used in the BS106 and BH116. For reference, the V8 engine known as the DV15TiS is used in express and tourist buses (such as the BH117 and BH120).

First, the DE12Ti engine installed in the BS106 produces 280 horsepower, while the newly introduced electronically controlled DE12TiS engine produces 290 horsepower. The DE12T engine used in the BH116 produces 300 horsepower. However, the standard engine for the BH116 is actually the DE12Ti, with the DE12T being an optional choice. The DE12Ti engine, as standard in the BH116, delivers 340 horsepower. (It is said that some BH116 units were shipped with a 310-horsepower engine.)

At this point, one might wonder: Why do engines with the same base design produce 280, 340, or even 310 horsepower? The difference comes from the installation of a turbocharger and an intercooler, whose efficiency can affect output. Of course, that’s not the whole story. Differences in compression ratio, injection timing, and the settings of the injection pump — the most critical component in a diesel engine — also lead to variations in performance, even with the same base engine. (Explaining all of this in detail could fill an entire book!)

Some enthusiasts may raise another question: Why not install the 340-horsepower engine in the city bus BS106? The answer is simple — as long as the engine performance matches the operating conditions of the vehicle, there is no need for excessive power. Higher horsepower does not automatically mean a better bus.

Now, returning to the main topic, let’s compare the two buses: BS106 (DE12Ti, 280 hp) and BH116 (DE12T, 300 hp). Some might ask why we aren’t comparing the 290-horsepower version of the BS106 instead of the 280-horsepower model. The reason is that more 280-horsepower BS106 units were sold than the 290-horsepower ones. After reading this article, those interested can try comparing the 290-horsepower BS106 with the 300-horsepower BH116 themselves.

Before comparing the two, we should note that buses have an enormous range of optional configurations — far more than passenger cars. In fact, most of a bus’s major components can be customized to the customer’s needs, making each bus almost like a custom-built order.

Therefore, we will compare the basic specifications that could be applied to both models.

The key components here are the engine and the transmission. The transmission must be matched to the engine’s output and torque. If the transmission cannot handle the engine’s torque, it could break or fail to withstand the load. This is why the BS106 and BH116 use different transmissions: the BH116’s maximum output and torque occur at higher RPMs. Similarly, the final gear ratio must be adjusted accordingly, as it directly affects the vehicle’s top speed and hill-climbing ability. Horsepower generally relates to hill-climbing performance, while torque determines acceleration and speed on flat roads. Interestingly, increasing torque usually reduces horsepower, and vice versa. Therefore, the balance between maximum output and maximum torque is determined at the point where the two curves intersect on the engine performance graph.

Now, before we make a theoretical speed comparison, we should first discuss how speed is calculated.

Vehicle speed is determined by the following formula:

Vehicle speed (km/h) = (2π × Tire loaded radius (tire radius) × Engine speed (RPM) × 60) / (Gear ratio × Final gear ratio × 1,000)

Therefore, the vehicle’s top speed is determined by the maximum engine RPM, the gear ratios of the transmission, and the final gear ratio.

Let’s apply this formula to our two buses.

First, we need to know the gear ratios for each transmission. Fortunately, the K1005C and K1205C transmissions have identical gear ratios.

The loaded radii of the two tire types are: 10.00-20-16PR = 0.506 m, 11R22.5-16PR = 0.508 m. The final gear ratios are 39/10 (3.9) and 39/11 (3.545), and the maximum engine RPMs are 2,100 and 2,200 respectively.

Let’s apply these values to the formula.

For the BS106 in 1st gear: Vehicle speed = (2 × π × 0.506 × 2,100 × 60) / (6.608 × 3.9 × 1,000) ≒ 15.5 km/h

By applying the formula for each gear, we get the following theoretical maximum speeds:

Now, the answer becomes clearer.

In theory, if both buses were to race, shifting gears at their respective maximum speeds and with perfect timing, the BH116 would have a slight advantage. However, this is only a theoretical result — in real-world driving, instantaneous acceleration plays a critical role. While it is possible to calculate instantaneous acceleration, the process is much more complex.

Furthermore, since the actual vehicle weights differ, applying the laws of speed and acceleration to the formula would yield different results. And if a 290-horsepower engine were installed in the BS106, the outcome would change again.

With these questions in mind, we conclude this report on the speed comparison between the BS106 and the BH116.