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Rewriting the MS programming


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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....

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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.

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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.

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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.

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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:

post-1194-125102382444_thumb.jpg

The hysteresis doesn't make a difference. Can someone suggest why this would be temperamental?

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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 :huh:

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.

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