Over the last couple of years I’ve spent more than an average amount of time sitting in laboratories listening to and occasion talking to scientists and other assorted boffins. I’ve done this in a wide variety of places, ranging from a huge complex just outside Sheffield, to Ferrai’s engine production facility in Maranello, through to Battersea Power Station, the pit lane at Spa during the GP weekend and now ProDrive’s facility up in the Midlands just outside Kenilworth.
The common denominator has been scientists from Shell that have been making me wise in the ways of fuel development and by association engine design, and engine management systems.
As part of the Shell V Power Network of Champions I have had access to some very clever people. People who are clever enough to be able to explain very complicated things to someone with an A level in Chemistry gained 20 years ago now. Don’t get me wrong, I’m not thick and still keep a very active interest in science, but a lot of what these ladies and gents know is well beyond my ken.
I’ve already written in some detail about the detergents in Shell V Power Nitro+ and how the effect the engine efficiency and ultimately the power of both diesel and petrol engines. I’m not about to repeat myself and if you would like to catch up on that, you can so here. This time I want to focus on two other aspects of the engine/fuel relationship but firstly that requires a little bit of a lesson in how engines work. Bear with me as I try and explain it as straight-forwardly as the boffins did to me.
|a 4 cylinder petrol direct injection engine|
Although there are two main types of fuel for cars, there are effectively 3 different sorts of engine. Firstly there are diesel engines, which are all the rage at the moment due to a variety of factors including emissions, power and fuel economy. Modern diesels, as I found out in the MINI Paceman Cooper D recently, don’t sound like tractors and are even fun to drive. Second and thirdly are the conventional petrol engine (with spark plug led ignition) and the newer direct injection petrol engines (which use pressure to ignite the petrol rather than spark plugs). Different sorts of engines face different challenges and to a degree the issues faced by a direct injection petrol engine like VW Audi Groups new 1.4TSI unit are quite similar to those faced by a diesel engine.
Direct injected engines trigger combustion via pressure. Very high pressure in fact but the long and short of it is the fuel is delivered into the combustion chamber in a different way to a conventional petrol engine. The injection is delivered by an injector- basically a milled metal device with some tiny holes in the end. Actually tiny doesn’t really do these holes justice. They’re about 70 microns across. That’s narrower than a human hair and amongst the smallest holes that we can mass produce. And fuel is being squirted through these thousands of times a second. There are 6 of these nozzles on a diesel injector and 5 on the VW direct injection petrol injector. If you want perfect combustion you need these holes to be clear because the margins of error involved are tiny (much like the injector nozzles really). So you can imagine what happens when deposits build up round the nozzles- and they do because don’t forget they’re right in the middle of what is for all intents and purposes a fairly impressive explosive event on an extremely regular basis. That explosion is what drives the pistion and turns the crankshaft.
The first problem that can occur when the injector nozzles become partially blocked is the fuel being delivered to the combustion chamber in either the wrong quanity or mix or it could be delivered later than it should. This will lead to sub-optimal combustion and a drop in power and performance.
The second problem leads on from the first in clever modern cars. Non optimal combustion often results in knocking, due to the noise it makes. If you couple this with the fact modern engine management systems are complicated, it can exacerbate the problem. The degree of complexity varies depending on the car you buy but a lot of cars out there have an anti knock sensor that is clever enough to work out which cylinder has sub optimal combustion and it will reduce the pressure to that specific cylinder. If the pressure has been reduced, the power will also be reduced and your car wont be running as well as it can. The engine management system does all of this in less time than it takes to blink, and continues to do it all the time, silently behind the scenes. It makes sense that the management system is doing this, after all it wants to protect your engine but it exacerbates the problem.
To see this in practice the mechanics at Shell have had a field day. They’ve taken an off the shelf car and heavily tinkered with the engine. What they’ve done is effectively remove the fuel pump and replace it with two fuel pumps, one to each side of the engine, servicing two cylinders each. This means you can supply each side of the engine with different fuel and dynamically switch it with a flick of a switch. Couple this with some clever monitoring systems, and we could see in real time the effect that Shell V Power Nitro+ had on the internal pressure inside the engines cylinders. And remember, the dirtier the injector nozzles, the lower the pressure is likely to be.
|V Power in the left hand cylinders|
|V Power switched to the right hand side of the engine|
|Lots of fans and computer monitoring of the engine going on|
|Heavily modified for technical useage|
At the end of the day, it was very impressive how the pressure increased whichever side of the engine had V Power Nitro+ being fed to it. The results speak for themselves- it was up to about 10% better. To let us see the results outside the lab, Shell have kindly provided a months worth of fuel for testing. This is something even their senior scientists don’t get, so I feel privileged and will report back on my findings later.