TheRecklessEngineer Posted August 18, 2009 Share Posted August 18, 2009 Due mostly to my own incompetence and inability to read a wiring diagram, when I first installed my MS ECU I managed to fry not only the fuel pump relay transistor, but also the corresponding output on the microcontroller. I understand this could be solved quite simply by buying a new microcontroller, but I'm not keen on forking out the £25billion it may cost for what may be a simple fix... What I would like to do is simply to re-label the FP output in the MS Extra code to use a different (i.e. spare) output on the microcontroller. A small jumper cable to the (new) transistor and MS can control the FP once again. Currently it is just ignition switched. I'm familiar with ASM code as I have spent a fair amount of time programming PICs, but I can't find the definition for the FP output anywhere in the code. Could someone point me in the right direction please? I'm also guessing I may need to modify the coding to MT to make the FP on light pop up at the right point, but I'll cross this bridge later.... Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 18, 2009 Share Posted August 18, 2009 If you're running MS-Extra code you can set one of the spare outputs to be on based on various conditions, one of which should be something close enough to "when the engine is running" to run a fuel pump. No ASM required. Quote Link to comment Share on other sites More sharing options...
Dave W Posted August 18, 2009 Share Posted August 18, 2009 Assuming you are using MS1 new CPUs cost £13 each. In the long term you'd be better off just buying a new CPU. However, you could modify the code and hardware to use a spare port but I'm not sure how big a job that would be. You could probably get most of the way there by using the user defined output triggering off the RPM ? That way you don't modify the MS code and it can all be done in hardware and MT. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted August 18, 2009 Author Share Posted August 18, 2009 Assuming you are using MS1 new CPUs cost £13 each. Where on earth from? If that's the price tag, I think I'll bite the bullet... Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 18, 2009 Share Posted August 18, 2009 http://www.diyautotune.com/catalog/cpu-megasquirti-cpu-p-105.html Unfortunately I've run out of spares, having grossly underestimated people's capability to break things Quote Link to comment Share on other sites More sharing options...
Dave W Posted August 18, 2009 Share Posted August 18, 2009 Where on earth from? If that's the price tag, I think I'll bite the bullet... Bill Shurvinton is where I normally get my kits/parts from, he seems to have a good stock in the UK so can ship pretty quickly. Listed in the official suppliers list http://www.msextra.com/viewtopic.php?f=94&t=22372 under "Bill's Bedroom' and I think he hangs around on LR4x4 sometimes. He's in Reading BTW. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted August 20, 2009 Author Share Posted August 20, 2009 Well, DIYAutotune want $35 shipping, and the cheapest I can find in the UK is £25 for a 2nd hand unit ex shipping. So, I've done as Fridge suggested above. The FP is wired into Output 1 (X4) and coupled to the PW (On when >1). I tried RPM, but the minimum value you can enter is 1 (=100rpm) which doesn't trigger until 150rpm. I'm cranking at 130 so no FP! Coupling it to the PW has the interesting effect of turning it off on overrun. It doesn't seem to suffer from this though. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted August 23, 2009 Author Share Posted August 23, 2009 Having now run this for a little longer, I've discovered that coupling to the PW doesn't work so well. When changing gear I get a massive backfire as the spark dies (PW to 0 on overrun) leaving fuel in the exhaust. I've been trying to get the output to work with the RPM. I tried this before (as above) but couldn't make it work at all - I figured originally that the output set at 100rpm wouldn't trigger until 150rpm. Trying it again, this doesn't seem to be the case. It quite simply seems to be temperamental - seemingly random on whether or not it triggers the output when cranking. Once runnning, its fine. My settings are: The hysteresis doesn't make a difference. Can someone suggest why this would be temperamental? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 23, 2009 Share Posted August 23, 2009 The hysteresis doesn't make a difference. Can someone suggest why this would be temperamental? Since it's counting in 8-bit unsigned, upping the hysteresis may well result in some strange maths, for example: Trigger point = 1 Hysteresis = 10 So on when RPM is greater than (1+10) = 11 Off when RPM is less than (1-10) = 245 It's probably temperamental because the cranking RPM bounces up & down a lot, you don't necessarily see it in the gauges but it varies quite a lot. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted August 23, 2009 Author Share Posted August 23, 2009 Well, I figured I probably ought to know my way around the MS code anyway. Delving into my incredibly rusty ASM, I found the definitions and just swapped output2 and fuelp. Works a treat. And I now have a much greater appreciation for the people who wrote the code. Quote Link to comment Share on other sites More sharing options...
Dave W Posted August 23, 2009 Share Posted August 23, 2009 Well, DIYAutotune want $35 shipping, and the cheapest I can find in the UK is £25 for a 2nd hand unit ex shipping. Did you contact Bill like I suggested ? Glad to see you got it sorted anyway Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted August 23, 2009 Author Share Posted August 23, 2009 Yes, I tried Bill but I didn't get a response. Quote Link to comment Share on other sites More sharing options...
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