MSefi.com read only forum (Jan.15,2018)

Ok, after upgrading from 2.881 to 2.886 I'm now having problems with xtau spiking which is causing the egine to stumble at idle. I've noticed that the dwell kicks about too.
With the MS on and the engine not running, xtau and dwell flash to zero every now and then, while all other inputs appear stable.
I've checked all my tuning parameters and they are as they were before the upgrade.
This problem occurs on both of MS boards and also occurs when they are plugged into the stim.
Any advice would be much appreciated.

I have compared 2.881 and 2.886 and i don't see any changes that would affect x-tau or even any of the inputs. The big change between these codes is the angle-based ginition timing, which in all my testing has proven to be very robust and accurate.

Do you have a copy of your msq that was saved just before you switched codes ?

If so, is it identical to a fresh one you make by saving with the 2.886 code ?

If you switch back to 2.881 does the problem go away ?

If you turn off x-tau with 2.886 does the problem go away - other than it might be worse under accel/ decel ?

The problem doesn't go away if I revert back to 2.881 nor if I load any of my old msq files.
Strange thing is that it still does it after I reload the boot file but haven't as yet loaded my current msq, eg it does it with the default settings.
And it is the same for both boards whether in the car or on the stim.
If I turn off xtau I don't get the spikes appearing on log but they do still happen on the megatune gauges.
I've also noticed on my logs some map spikes which aren't apparent on megatune
I'm totally screwed on this on

Something must have got corrupted when transferring files. But twice?
I did buy a new usb to serial interface recently, could that be the problem?

From what you are saying this is not a code problem and it's not an msq problem because it happens with the default msq. So it sounds like the code isn't getting loaded properly and that could definitely be due to the new usb cable. But it is very weird that it would happen in a consistent manner like this. If the code were corrupted it usually doesn't run at all. Plus you should get error messages from the downloader.

Is the problem you are seeing real in the sense that if you disconnect MT and just run the car without any comms, can you feel it in the engine ?

I would try downloading with a different pc and different serial cable.

The problem is real enough because the engine splutters and dies after a few seconds. This happens with both boards so the problem is something common on the software side of things. If I run megalog I see spikes all over the place.
The USB cable I'm using is a Prolific brand and from what I've been reading on this forum others have also had issues with them.
And I don't think running Vista helps much either (maybe that just my anti Vista bias showing through).
If anything it just makes file downloading etc much more difficult.
I'm taking both boards to work tomorrow and will hook them up to a computer with a straight serial comms connection.
Hopefully that will fix the problem.

I'll let you know either way, as this problem could also be effecting others out there in megasquirt land.

Thanx for your help so far, much appreciated.

Fixed

It was that new usb adapter I bought.
I loaded a fresh copy of 2.886 etc from my works computer using a straight serial port, reloaded my latest msq, and both boards worked fine on the stim and in the car.
I was even able to repair my old faithful usb adapter (cracked solder joint on 9 pin plug) and I tested it out by loading the s19 file etc and it was fine too.
I might look around for a pcmcia adapter, the ones the computer techs use at work is rock solid but at nearly $300 I'll have to wait till they leave one laying around.

Look here.
http://www.usconverters.com/index.php?m ... xwod_CW9Ew

That's cheap, but now that old faithful is working again I think I stick with it.