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Good day. I am building a Turbocharged Honda D16A that will be running only on LPG. The LPG system is a vapor sequential injection. Would like some advise if anyone can. My thinking is, seeing that the fuel is a dry vapor, the flow won't rely on a fuel film being formed. So, in theory, will it be okay to tune the car solely in steady state? That is eliminating the transient tuning aspect as it maybe unnecessary? Any input or assistance/suggestions are welcomed.
Thanks in advance.
I worked on a CNG powered vehicle (Bonneville streamliner, see pic below), gaseous vapor at the injectors. One thing that caught us out, the injectors would leak after the engine was stopped, and would flood the cylinder / manifold, making the car hard to start. The solution was to stop the engine by running out of fuel (we turn off the fuel solenoids), and the engine will use all the fuel (and reduce the pressure) so that there is nothing to leak when the engine is off.
I will say that at Bonneville we aren't worried about transient fueling issues. But you are right, you do not need to add any additional fuel.
I spent time at the company that supplied the injectors (Clean Air Power) characterizing the injectors using their flow bench and a variable power supply. At the time I was involved in the data logging side of things, and the tuning was handled by Shane Tecklenburg.
David, must say, that's a pretty cool build. My project goals would be a lot more modest. Hoping to achieve around he 200HP mark. I don't think leaking injectors would be an issue, as they are standard LPG gas injectors designed for street use. Couple questions if you don't mind.
Did the car have any issues with cold starts?
Any idea what sort of percentage compensation was done to the fuel map with respect to fuel pressure and temperature?
What sort of target afr was used under high load?
Sorry for the questions and going off my own topic,but haven't come across many people with first hand experience in performance CNG/LPG tuning.
The injectors we use were also used in CNG street vehicle (garbage trucks!), but I don't think they ran them at 120 psi pressure. Until we found that problem we would struggle to start the car, particularly first thing in the morning -- like 15 minutes of cranking, a bit of a puff, then nothing. Eventually we use the WOT while cranking to clear the flooded condition. Now it starts easily as soon as we get sync.
The fuel map just looks like the torque curve of the engine, the load axis is MAP/EMAP. There is a simple MAP compensation (double the pressure, double the fuel...). No Fuel pressure/temp comps. We ran closed loop with a target of Lambda 1.0 - 0.87 depending on load.
Thanks for the response David. Your time is very much appreciated.