Diesel smoke is almost always due to pressing too much on the accelerator. It could be that the vehicle is overloaded, too high a gear is selected, or that a lot of acceleration is required at a particular moment.
Surbo fitted at the outlet of air filter of Mercedes Vito 111
According to our experience, one way to counter diesel smoke is to add a Surbo to the air intake of the diesel engine, at the air filter section. The Surbo will raise the air intake power as it creates a deep-suction vortex within itself to draw in more air, and this raises the torque and power of the diesel engine immediately, even at idle, shown by a higher idling speed. The driver would be able to move the diesel vehicle with less pressure on the accelerator due to the added air compression. Note that improved engine compression (in this case through higher air compression from the Surbo) directly results in an increase in engine efficiency, which means the engine will put out more power for the same amount of diesel put in, and so require less pressure on the accelerator. The diesel engine will also be able to rev to a higher rpm for the same accelerator travel, so that it can latch on the the next gear at a higher rpm and thus avoid over-stepping on the accelerator at too low an rpm and cause black smoke emission. The torque spread on a Surbo-equipped diesel is also wider, meaning more torque even at a low rpm, so the driver needs not press as much as before on the accelerator even at a low rpm. So, he can shift up earlier too, with less risk of causing black smoke. Downshifts can be made quickly and smoothly because the air supply from the Surbo is ready to meet sudden spikes in air requirement, and its air pressure holds the engine preventing it from losing too much rpm when the accelerator is released during a gearchange.
Higher compression for diesel engines with Surbo
The Surbo can also be used on turbodiesels, helping the turbocharger to spool up earlier. This is because the compressed air from the Surbo, even from a low rpm, pushes air more quickly through the exhaust, which turns the turbocharger up to speed earlier, and so it is able to provide boost from a lower rpm. This reduces turbo lag, which holds back engine power at very low rpm, and can be a cause of smoke by itself.
Adjusting the bolt below the accelerator so limiting the accelerator travel and diesel input also limits diesel smoke, but engine max power is down too, and adding a Surbo can put back some of this lost power. See the Nissan Cabstar '00 review.
We had installed the Surbo on a turbocharged Opel Combo 1.7 CDTi that was a few years old, and the torque and power was astonishing for a goods vehicle. The vehicle was in very good condition and there was no smoke problem. Recently, we did two more Combos around ten years of age. The first one had a turbocharger that was not functioning, or there was a leak in the pipes connecting the turbo to the engine. There was initially some smoke but we showed the owner, standing behind the vehicle, how to press the accelerator to activate the Surbo and reach the rpm limit without creating smoke. He shortly sent the vehicle for smoke testing and it passed. The other Combo had a still functioning turbocharger but the owner was caught for emitting smoke. He said that his mechanic could only clean the exhaust deposits, but the problem was really at the source, one of over-fueling. With the Surbo installed, he commented that there was quite a lot more power and the smoke was not seen anymore in the rear view mirror.