Liquid fuel itself doesn't actually burn very well, we really want fuel vapour entering the cylinder where possible. The idea with this system is they're working on the principle that the injectors fitted outside of the inlet trumpets are going to provide better atomisation of the fuel, it's got longer for the fuel to mix with the air, meaning that we should end up with a more homogenous mixture of air and fuel as it goes into the cylinder, meaning that we have a better chance of combusting all of the oxygen that's making its way into the cylinder so it's really just mixing the fuel and air properly, fuel and oxygen properly and also introducing the fuel in a manner that's very easy to ignite. This is quite common there to, sorry DTM is the other class that I was trying to think of there, it's very common to run a set of primary injectors which are down in a conventional location, right down by the cylinder head flange, pointing directly at the back of the intake valves.Īnd then they'll have a secondary set of injectors which are mounted outside of the inlet trumpets, maybe out in the air box. So don't tend to see this so often these days but it was very common back the likes of the British Touring Car Championship, it was quite popular there where you've got a control class and basically the engine builders and tuners are trying to extract every last horsepower out of the engine. The other technique or other situation where staged injection is a popular option is in high output naturally aspirated engines. So basically that'll have you covered regardless just about how much fuel you need to deliver to the engine. So that's one strategy there and I'm talking staged injection, it may be that we are running multiple stages, it doesn't necessarily need to be a primary and secondary injector, that can be three, four stages, depending on the system that you're running and its capabilities. If we want to go to something a little bit more extreme, methanol which is a fuel that's very common in drag racing circles, you need to be running somewhere in the region of about 2-2.5 times the fuel volume compared to pump gasoline in order to keep your engine running reliably so that puts a massive demand on the injector system. This gets made even worse when we're starting to run on fuels where our fuel mass or required fuel mass starts to increase so for example, if we move from pump gas to the likes of E85 which is very popular today, we're going to find that we need to increase our fuel delivery by somewhere in the region of about 35-40% in order to maintain a safe and reliable air/fuel ratio or lambda target. So this is a big problem, particularly with engines that are making very high specific power levels so we most often see this applied with the likes of drag racing, high boost, turbocharged drag engines are the perfect advocate for staged injection. Obviously there is a limit with our injector sizing, if we go too large with our injectors, we're going to get to a situation where we can supply enough fuel to keep the engine happy at high speed, high engine RPM, high load, which is great but we may find that we struggle to be able to adequately control the injectors to deliver the smaller masses of fuel that we need for good control over our air/fuel ratio at idle. Most commonly it's used on engines where supplying sufficient fuel through a single injector per cylinder or per rotor in a rotary engine, is problematic. Now staged injection, I think we'll start by talking about what it is and why we would need it and there's a couple of different scenarios where you may want to consider staged injection. To demonstrate this, we are going to be using our FD RX-7 project car. This time we're going to be looking at the staged injection system, specifically on the Adaptronic modular ECU. Hey guys it's Andre from High Performance Academy here, welcome along to another one of our webinars.
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