I put this topic in this general discussion forum for now as that is all it is at the minuit.
Looking around the files in the Megatune/ firmware package for VEMS, i keep coming across various files and comments of dual table code. Some of this i suspect is actualy megasquirt left overs?? if so why is it still there so late on in the VEMS time line. Anyway
The reson I'm asking about this - with VEMS having dual WBO2 and EGT, dual VE tables would be a logical step, and, would be very useful in getting the siamese inlet port injection system to work on the Austin Rover A Series engine.
There has already been much research and code done for this on the Megasquirt controller, though, the way i see it, is limitted by hardware. Discussion can be found here
http://www.turbominis.co.uk/forums/index.php?p=vf&fid=32 here
http://www.turbominis.co.uk/forums/index.php?p=vf&fid=33 and here
http://www.turbominis.co.uk/forums/index.php?p=vf&fid=29Jean Belanger, working the code for Megasquirt in his spare time, Is president of Opal RT Technologies Inc Montreal
http://www.opal-rt.com/index.html , the leading provider of distributed real-time simulation and hardware-in-the-loop testing systems So its not entirely a enthusiat project, as such, there is some professional input here.
I dont think VEMS is far off actualy working the siamese problem, it just needs the coding. I know nothing of the code side of things, though i can pick things up, its slow, and starting from the very first page of things is where i would have to start. I dont have the time at the moment but after seeing the down sides of the SPi wet manifold system, though not unsurmountable, port injection does solve certain problems easily. Yet on the siamese ports it interjects other problems. Its also a bit of a challenge. I can see it working on VEMS fairly easily as the hardware is there, Its just the code!! Starting with a dual active table firmware would be one step closer. Does this exist in one form or another?
Here is the general theory of the siamese code, though not by any means the only one or the right one.
For starters, courtesy of Dave Coxon, here is the Rover patent appliction, which to my knowledge, the Mini MPi 1997 onwards, was the only car/ engine to run this system
http://www.davecoxon.co.uk/A_SERIES_PATENT.PDFBasics of it are, cylinder pairs 1/2 and 3/4 share the same inlet port (siamese), inlet valve overlap is such that as one valve is starting to close, the other valve is starting to open. The result is, in a port injetion system, as one cylinder is close to the end of drawing on the inlet port, the second cylinder starts to draw on the same port. Getting the right amount of fuel into each cylinder starts to become vague. Rover got round this, we suspect, by shifting the injection points for each cylinder into a 'window' of valve opening whereby only one valve is open at any one time
Other thoughts on this are perhaps the injection point is the middle of the calculated pulse width with dual tables firing the injector at different intervals (rather than all at the same point in the cycle). Wiring shows four injection drivers crossed over and commoned up to the two injectors, Mpi Crank trigger shows 4 missing teeth, two 180 degrees apart, ignition points? and the other two 180 degrees apart, but the second having a difference of 10 degrees so in reality 170/190 apart, injection points? Cam sync giving TDC#1 cylinder. In such a way that the pulse width looks as though it is one, you could then alter the pulse width between the tables so that the percieved injection point was shifting yet injection point stays the same(The Rover Mini MPi ECU was developed from the MEMSJ2 ECU used on the KV6 engine. This had dual Lambda and presumebly dual VE tables.) This way with dual Lambda pressent, you can tune the VE tables, rather than have dual active Lambda, so that if the middle cylinders are running rich and the outers lean, you can increase VE on the outer cylinders and reduce VE on the inner cylinders to balance out the AFR. In simple terms you have seperated the middle cylinders from the outer cylinders and given them their own VE tables.
One other thing that can also help reduce this port robbing situation is the use of a scatter pattern cam, reducing port robbing issues, but not eliminating it. One of which already specificaly designed for the injection engines with minimal valve over laps for use with Speed/Density metering, which is a bonus.
Please discuss this as at some point i will be coming back to this to actualy have a go at it, more input the better
If we were to get this workable, there is a whole other sales area just waiting for it to happen.
Sprox
