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DB2SR - winter project turns into lockdown project
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hindsight



Joined: 13 Feb 2010
Posts: 126
Location: Central Scotland

PostPosted: Thu Oct 15, 2020 6:19 pm    Post subject: Reply with quote

Hi Ralph - long overdue for an update, I think.. but an update with mixed results..

So, in the last update, I had got the v3 board up and running, and it was quite happily running the engine, so I started tuning the cold-start fuelling.

Along the way, I started to notice that it wasn't running just quite as well as the previous board, and digging into it a bit more, it became clear that the new board was losing sync with engine TDC regularly (the microcontroller needs to keep track of where TDC is on each engine revolution in order to calculate when to squirt or to fire).

The previous board had no problem with keeping in sync. Since then, I've spent a fair amount of time trying to understand where the problem lies. It's almost certainly an issue with electrical noise interfering with the crank sensor signal, and it has to be either a physical problem with the v3 board, or a circuit design issue, but annoyingly, it's not something I've managed to nail quite yet.

In other news though, somewhere along the line, the original ECU developed a fault. I sent it off to Italy to TDD (the original manufacturers), and not only have they repaired it, but they've found a 944cc chip for it.

Additionally, they're having a rummage around to see if they have the original software for connecting and tuning it.

So - the onward development of the new ECU is a touch frustrating, but I'll keep at it from time to time to try and understand what is going on with it, but I still have options with both the v2 ECU board and also the OEM unit.

Mike
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Fri Oct 16, 2020 9:37 am    Post subject: Reply with quote

Sounds like sterling service from an italian supplier/manufacturer.....I either get great service....or absolute zero replies......theres never a half way house with Italian companies.....glad you got the former repsonse
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hindsight



Joined: 13 Feb 2010
Posts: 126
Location: Central Scotland

PostPosted: Thu Dec 24, 2020 5:45 pm    Post subject: Reply with quote

Long overdue an update on proceedings, I think..

So - in the previous episode, the original ECU had developed a fault, and I had managed to make a good contact within the original manufacturing company (TDD Racing), who to my utter amazement was up for having a look at it.

He confirmed that it had developed a fault, which had fried the microcontroller, the EPROM and a few other components, but was confident that he could put it right.

A few months later, he got back in touch to confirm that the ECU was fully repaired. Not just that, but he had located the original software for building an EPROM image, and found a 944cc image... exactly what I was looking for previously, before the whole ECU build became a thing!

As you said Steve, a sterling service from an Italian manufacturer. They're based not far from the Ducati factory, so at some point when touring/travel becomes a thing again, I do hope to pay him a visit.

Additionally - last month, I got the fairing back from the paintshop, nearly a full year after I dropped them off, prior to doing even the 944 upgrade. There's a few reasons for the time taken, including the whole COVID thing, but none of that matters, because it was actually useful to not have to store that bulky one-piece fairing, and he's done a fabulous job - while it was only minor blemishes that I originally expected him to finish, he did a full respray (for which I had to get Imageworks to put together replacement decals), and it now looks fabulous.







It's worth also mentioning that I've also recently told this story over on https://www.ducati.community/threads/scope-creep-bimota-db2-2v-944-and-custom-ecu.24950/ - (and probably more coherently than the ramblings here, I suspect Smile ). But while doing so, it got me thinking about the home-made ECU, and the future for it, given that I'm in a good place with the original ECU now.

I think it's definitely still a useful and interesting thing to have done, and certainly if the OEM ecu ever develops a terminal fault, then it would be useful to have a replacement like this, so I've been doing some more work on it recently, and in light of a previous comment that I made about electrical noise on the board, I've designed an update, which I hope to be an improvement - it's currently being manufactured in China, and hopefully I'll get it in January for testing - here's a picture of what it will look like (without the connector and Arduino installed). Very similar to the previous, but some key changes to the crank input processing.



That said, one of the components that I need to build up another ECU is in Germany, and the supplier is refusing to ship at the moment, citing Brexit and Covid as a reason... Sad

On the original Bimota ECU, I've also been investigating the software that TDD sent through to me, and I now have the capability of easily and quickly generating new EPROMs for that original ECU, so I suspect that at some point in the future, I'll be taking the bike along to a local Dyno shop, and confirming the AFR behaviour, and cutting a new EPROM to suit.. and the useful thing is that now I have access to all the fuel map data, transposing any fuel map between the old ECU and the new ECU (or vice-versa) will be trivial.


Seasons greetings to everyone,
Mike
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri Dec 25, 2020 2:10 am    Post subject: Reply with quote

This is for the update hindsight.

The paint job on your DB2 looks fantastic!!!


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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
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welshlamb



Joined: 09 Mar 2011
Posts: 592
Location: South Wales , Nr. Abergavenny

PostPosted: Tue Dec 29, 2020 7:10 pm    Post subject: Reply with quote

Looking Brill I must say. This is turning ( I hope you agree!) a very nice bike into an really excellent one. Will have to stage a DB2 meet up at some stage as there are a fair few (by Bim standards) prowling UK highways now. Roll on summer 2021!!
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Wed Dec 30, 2020 10:55 am    Post subject: Reply with quote

welshlamb wrote:
Looking Brill I must say. This is turning ( I hope you agree!) a very nice bike into an really excellent one. Will have to stage a DB2 meet up at some stage as there are a fair few (by Bim standards) prowling UK highways now. Roll on summer 2021!!


Needs to be a few more...or at least one DB2 from Wales prior to meet up....its not like you havent had time eh WelshLamb?

Within 75miles of me theres a DB2 Half Fairing and a DB2 FE.....and a 944cc DB2 FF.....and then of course my DB2.....And theres 3 No. DB4 tricolors and a DB4ie within the same distance....the closest being just 5 miles away....

Painters eh....the good ones take their time....and they never like to "touch up"....almost impossible to make invisible transitions between new and old....so...full repaint it always is....I dont blame him...You do need to replace that headlight unit with a twin beam version and get shut of the deflector perspex piece.....mind you....you could just peel it off now that its registered....not sure how much of a stickler your MOT man is>>??
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hindsight



Joined: 13 Feb 2010
Posts: 126
Location: Central Scotland

PostPosted: Wed Dec 30, 2020 5:58 pm    Post subject: Reply with quote

2bims wrote:
You do need to replace that headlight unit with a twin beam version and get shut of the deflector perspex piece.....mind you....you could just peel it off now that its registered....not sure how much of a stickler your MOT man is>>??


You are of course correct. At one point during the rebuild, I actually bought another one of those same headlights, and opened it up as I thought it might be possible to convert to UK spec (I didn't want to operate on the original one, just in case). Unfortunately not so, which is a shame because I quite like that headlight unit (apart from the sticker..). Another item on the to-do list..

Focussing on getting my 916 serviced and ready for spring now, as it hasn't turned a wheel in about 3 years. Smile
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hindsight



Joined: 13 Feb 2010
Posts: 126
Location: Central Scotland

PostPosted: Sun Jan 31, 2021 6:52 pm    Post subject: Reply with quote

Another update: two steps forward, one step back. (HEALTH WARNING: This is another geeky post, and involves no motorbikes unfortunately...)

I mentioned previously that I had designed an updated board. The new PCBs arrived a few weeks back. There were a few modifications to this new design, the main goal was to have more direct control over the crank signal processing. This is the part of the circuit that changes the sine-wave AC signal from the crank pickup into a square-wave 5v signal that the microcontroller can make sense of.

Here's an example:

The pink sine-wave trace is from the flywheel pickup, and the purple is the square-wave signal for the microcontroller. Sorry about the image contrast.

Previously, I was using commercially available plug-in modules for this, and I was finding that some of the components that they were using were introducing limits for the high-frequency signal that the 60-tooth pickup on the DB2SR. Under bench test conditions, this started to show up at around about 6500-7000rpm, where the ECU would lose sync with the (simulated) flywheel. On the road, that would be a horrible experience.

If you're interested you can see this happening on a bench test in the video at the following link. On the scope output, the purple trace is a tacho output from the signal generator with a period of one crank revolution, green is the flywheel signal (simulated with a square pulse for simplicity), and blue is the ignition pulse. The RHS of the screen is the view of what the ECU is seeing - in particular, keep an eye on the rev counter - the test cycle starts at 6000rpm, runs for 15 seconds then moves to 7000rpm, and onto 8000rpm where you can see that the ignition timing starts to drift badly, and the ECU loses sync and cannot determine RPM.

https://youtu.be/ELoxN8BbZ1s


The modules for doing the crank signal processing that I had were tiny, with schematics not always available to study, and difficult to rework by changing components due to the tiny surface-mount components that they use. So, armed with a little bit of knowledge and a few datasheets, I designed a new circuit to do this, right on the circuit board (rather than being an external module).

Once I started building up and testing the new board, it became clear that I'd made a couple of errors (some very silly), but I was able to rework the components on the boards, and learn loads from the mistakes that I had made. Here's the new ECU (in black) sitting next to the previous generation (in green). You can see some of the corrections that I've made with small wires soldered onto components.



I've now bench-tested the board up to 12,000rpm, with no signal dropout, which is good, but not the whole story, as when it's actually on an engine, the signal can be a lot noisier, which might introduce additional constraints. The new board is currently tuned with no hardware protection for electrical noise - that'll come later, if I need it.

I was also keen to test the performance/accuracy of the new circuit against the previous, so I hooked it back up to the simulator rig, and for the previous and new ECUs ran a test at every RPM value between 1000rpm and 8000rpm, with ignition fixed at zero degrees BTDC, measuring the timing of the ignition pulse. I think it's natural to expect a bit of retardation as RPM increases crank revolutions are happening pretty quickly at 8000rpm, and therefore even the slightest scheduling delay will cause a bit of retardation. Additionally - at least *some* of that retardation will be from the instrumentation (measurement error).

Here's the results:


The red line shows the previous ECU, with the external module (that's the small blue PCB in the photo above). With ignition fixed at 0 degrees BTDC, you can see that the old ECU consistently shows more retardation than the new one, up until the ECU loses sync at about 6850RPM, and timing goes completely out of the window, clearly showing that the new PCB with the onboard signal processing is giving me far more accurate control of ignition timing. Up until the 6850rpm point, the old ECU is on average 3.3 degrees more retarded than the new one. If I need to add hardware noise filtering (capacitors), this may reduce this accuracy benefit, but we'll cross that bridge in due course.

While it was disappointing to have so many errors in that updated board, it still feels like a success, and it helped me learn loads more.

I also now have far greater control of that signal processing, which will allow me to trade-off signal/noise protection against maximum RPM, which I couldn't do on the other modules.

I've got an updated design with a few fixes and improvements, and once I've thoroughly checked it (hopefully better than last time), I'll submit it to the PCB fabrication plant, so I guess I'll be building up another updated ECU in about a months' time.

Mike
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glened



Joined: 15 Aug 2013
Posts: 135
Location: Lancashire

PostPosted: Mon Feb 01, 2021 7:41 am    Post subject: Reply with quote

Keep up the good/great work. It puts my little project into perspective. Watching with interest ????
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Anders



Joined: 05 May 2009
Posts: 121
Location: Norway

PostPosted: Mon Feb 01, 2021 8:25 am    Post subject: Reply with quote

Very interesting. I'm looking forward to every update Smile

On a side note:
Me and a mate made an EFI system for his '95 Duc 900SS many years ago. We are both software engineers, he has a degree in electronics design. I do also have some electronics education. We both have strong interest in mechanics, although no formal education.
My mate made the electronics and software, I made the throttle bodies. Very fun project. This was in the days before the wide band sensors. The project was abandoned after a summer of test-riding with a laptop in his tank bag, and he bought a pair of FCR carbs...
If we had waited a couple of years, the wideband sensor would have made the task somewhat simpler, as he could have used some closed loop regulation. I think he had stayed with the DIY injection in that case.
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Anders
bb1, Mille S2, Guzzi / Watsonian, Morini Corsaro 125, EC200, RD350YPVS etc
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hindsight



Joined: 13 Feb 2010
Posts: 126
Location: Central Scotland

PostPosted: Mon Feb 01, 2021 5:07 pm    Post subject: Reply with quote

Interesting to hear Anders.

Out of interest - were you calculating the crank angle in that project?, if so did you have a toothed wheel fitted to the crank, or were you relying on the existing timing/dwell marks on the 900ss flywheel?
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Anders



Joined: 05 May 2009
Posts: 121
Location: Norway

PostPosted: Tue Feb 02, 2021 7:56 am    Post subject: Reply with quote

To be honest, I don't remember. I wasn't very involved in the sensors and hardware, I just made the throttle bodies. I seem to remember that he set up a sensor (hall effect?) on one cam to measure the camshaft position, so I guess he didn't measure the crank angle on the crank. But as I said, I'm not sure.
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Anders
bb1, Mille S2, Guzzi / Watsonian, Morini Corsaro 125, EC200, RD350YPVS etc
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hindsight



Joined: 13 Feb 2010
Posts: 126
Location: Central Scotland

PostPosted: Tue Feb 02, 2021 9:01 am    Post subject: Reply with quote

I briefly considered whether I could swap out the standard Ducati magnetic sensor from the flywheel for a Hall-effect sensor also - that would have removed the need for all the stuff I just mentioned in the last post, as they natively give a square-wave output, rather than the sine-wave AC pattern.

I decided against investigating that line of thought any further, because I felt that swapping the sensor would be a step too far, as it would make it wholly incompatible with the OEM ECU.

It's worth pointing out that the DB2 only has a crank/flywheel sensor, and not a cam sensor, so the ECU cannot determine the phase of the engine and can only operate in wasted spark mode, meaning that the spark plug will fire at both compression and exhaust phases. But particularly given that the cylinder isn't under compression during exhaust, it's my understanding that this isn't quite as wasteful as it sounds.

The desmoquattro engines (and engine covers) have the facility for dual pickups - for both crank and cam timings, to allow the phase of the engine to be determined, so that each plug only fire once every second turn of the crank, as you might normally expect.
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Bud977



Joined: 03 Mar 2013
Posts: 525
Location: Sydney

PostPosted: Tue Feb 02, 2021 9:13 pm    Post subject: Reply with quote

At least a 4 stroke wasted spark system still fires once every revolution.

My RD350LC has a wasted spark system. A two stroke with a 180° firing order, so it fires every 1/2 a revolution. It has a simple single coil with two HT leads and two triggers on the rotor.
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hindsight



Joined: 13 Feb 2010
Posts: 126
Location: Central Scotland

PostPosted: Mon Mar 01, 2021 1:04 pm    Post subject: Reply with quote

Here we go again, updated board just arrived from China (in green on left of picture) Very Happy



Though, it'll probably be a week or two before I finish building it up, as I'm midway through a service of one of the other bikes that I'd like to get out of the way.
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