What is a Torque Request system and why is that different?

Back in the 80’s when forced induction vehicles came to the mainstream the systems used to operate them were pretty crude. The boost level was entirely controlled by a pneumatic system. The fuel system hardly acknowledged the additional fuel demands, and didn’t do much to assure they were correct. The ignition system operated in its own little world that barely recognized the other systems were even involved. Turbochargers had a very short service life because they ran so hot (and had such poor cooling and materials) that they would frequently glow bright orange with self destructive results. This was a dysfunctional union with too many systems and the low performance levels were the result of this strained relationship. Pushing the power train farther could quickly result in damage that may mean the end of your vehicle.

In modern torque request systems (applies to most Volvos since 1999) the equation is different. For starters, all of those systems are controlled by one processor which contains maps that consider the way the systems interact. In the old days the boost would go up and there was a hope that the other systems would react appropriately, but this wasn’t really linked, assured or checked. In the new world, all these systems receive their instructions from the same map and the reaction and outputs are cross checked to make sure the requested actions were actually completed (and the resulting outputs were as expected). If the results are not as expected, the processor will make appropriate adjustments to correct or, even more importantly, protect the power train from damage. Since there is a built in safety net, the engineers feel more comfortable with pushing the engine closer to design limits and this has resulted in production cars delivering higher performance levels.

In the process of bringing all of these controls “in house” there was also a shift in the way the engineers thought about the output in general. In the past they would specify the boost, fuel and ignition limits but the resulting output was simply the result of those inputs and ambient conditions. That result would change depending on air quality, temperature and fuel quality (among other variables). In the brave new world the engineers proactively decide what the output (result) should be and allow the processor to make whatever adjustments are needed (within preset limits) to hit this target with the least amount of effort. The path that the processor chooses to hit the target may (and will) change according to current operating conditions. This is very logical from an engineering standpoint since there will be times that you can accomplish the goal (output torque level) with less effort (boost and fuel). A win/win proposition.

But there is a problem in this modern harmonious feel good engineering world. This problem is especially troubling for the performance enthusiast.

The enthusiast makes changes to the vehicle with the expectation that performance will be improved. For example, an exhaust system is added with the expectation that the additional exhaust flow will allow/induce greater performance. However, the entire system is set to hit a specific target measured in output. So installing a better exhaust may help the vehicle reach that target faster or with less effort, but the performance will not go beyond the target (and the vehicle could probably hit the target without the exhaust upgrade). Faster to target but still the same target.

In a nutshell, you may improve the performance under the curve (a little) with less resistance to flow but the maximum number (as measured on a wheel dyno) will not change. In fact the vehicle may run less aggressively since it can hit the target more easily. This explains why some people notice fuel economy improvements when they make performance upgrades. But that wasn’t really their goal, was it?

So the short version here is pretty simple. If you do not install a proper tune with new specified torque targets you will not see significant maximum performance improvements. All of these bolt on parts make it easier to hit a higher target but do not change the existing target. Your car needs to want to make more power and only proper adjustments to the map will do that.

Let’s throw in one more twist here. If you manually override a system (such as a manual boost controller) the processor will actually make changes to attempt to bring the car back to target. Even if this generates a higher boost figure it will probably actually be slower on the wheel dyno. Many times people will confuse the spikes in performance caused by these corrections with actual power gains. More often the case is that the vehicle is making less power and simply delivering power in a very poor curve while trying to override the manual changes. Sudden boost spikes/surges are actually a bad thing.