Scope Creep (Bimota DB2 2v 944 and custom ECU)

Noobie

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I've been thinking over what you wrote there and I also agree something is odd. Mostly because I was lost on page one but I am enjoying your thread and posts and they are interesting reading. Good luck (y)
 

hindsight

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I've been thinking over what you wrote there , and I agree , there's something odd .

Given how good ( and accurate ) modern injection / ignition systems have become , I can't think of any sensible reason why fuel
should ever be injected to closed inlet valve .

I suspect the answer is in the ECU - TDD made these ECUs in limited numbers, and mainly for Italian Group-N rally cars (as I understand), so they wouldn't have been designed with V-twins in mind (bearing in mind that there were only 148 or so Bimota DB2SR's produced with these ECUs). I suspect they would have more normally been used with banked injectors across multi-cylinder car engines (banked, because there are only two output channels for IGN and INJ).

Perhaps the code in the firmware just didn't accommodate adjusting the fuel pulses between the channels (because, as we know - ignition timing is very crucial, but fuel delivery is not), because the ECU was generally used on cars with more cylinders that output channels (I'm guessing - I don't know for sure).

It's going to make the next combustion stroke over-rich , surely ?

Depends on how you look at it, I suppose.. but it would be accounted for in the map once tuned. Bear in mind that a carburettor is *always* spraying fuel into the port, even on a closed inlet valve - it's the same thing, isn't it?

Though, I agree it just must be more efficient to time the spray to an open valve - and that's something that the custom ECU *can* do for half of the load, but for reasons mentioned previously (no cam sensor), it'll be squirting twice in each engine cycle, so half will be still against a closed valve. (y)
 

Barry Hell

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I've been thinking over what you wrote there , and I agree , there's something odd .

Given how good ( and accurate ) modern injection / ignition systems have become , I can't think of any sensible reason why fuel
should ever be injected to closed inlet valve .
It's going to make the next combustion stroke over-rich , surely ?

Seems like throwing out the baby with the bathwater !

BTW - Keep up the great work and the fascinating posts .... really enjoying it ...... (y)
I think H-D developed constant firing just to give their engines a chance 😁
 

Duke of Prunes

Well-known member
Bear in mind that a carburettor is *always* spraying fuel into the port, even on a closed inlet valve - it's the same thing, isn't it?

Hmm .... not sure if I agree on that point ..... I'm still ruminating
Traditional carburettors rely on the Venturi effect to work , which depends on air flow .

I would think that no air flow means that no fuel leaves the carb ( regardless of needle position )
then on the induction stroke , the inlet valve opens and the descending piston creates suction ( air flow ) .
I watched someone doing artwork with an air brush , and no paint comes out without the air flowing .

On a side note , I was binge watching some car restorations over the weekend .....
" I found an Italian supercar in a barn " .... you know the sort of thing .

Those TDD ecus came up a couple of times , and they seem to be in the "Rocking Horse Poo" category ,
not least because salvaged units rarely work ( I think they tended to burn out injector drivers on the board )

There's a firm in Florida that have started prototyping their own "copy" boards
and claim to be able to take all the data off the old units and write it to a new one .

So it looks like it is do-able ..... ?
 

hindsight

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Those TDD ecus came up a couple of times , and they seem to be in the "Rocking Horse Poo" category ,
not least because salvaged units rarely work ( I think they tended to burn out injector drivers on the board )
Interesting!

The ignition and injection drivers on them are fairly standard IGBT or MOSFET components, so easily replaced if they fail.

Aside from the one on the DB2, I have another two TDD ECUs sitting on my desk right now - condition unknown. Not the same version as used on the DB2 unfortunately - I think these were from a V-Due, and probably use a different microcontroller and software (though, I've yet to open them up and investigate).




There's a firm in Florida that have started prototyping their own "copy" boards
and claim to be able to take all the data off the old units and write it to a new one .

Ultimately, that's what my little project is doing also - a plug-and-play replacement for the original TDD ECU
 

Duke of Prunes

Well-known member
Ultimately, that's what my little project is doing also - a plug-and-play replacement for the original TDD ECU

More power to you , that's what I say (y)

I think there is rich seam there , just waiting to be mined .

Some of those restoration fanatics spend silly money on just the electronics parts alone ,
but in some cases , the smarter guys hunt down the very same unit that was used on a way cheaper vehicle
eg. Fiat / Lancia / Peugeot / Renault .

Example : The hydraulic slave unit that works the F1 paddle-shift gearbox on Ferraris
....... was also used on a mid-priced Lancia !!!

On my own bike , all of the sensors needed for the ecu are actually BMW parts , except for the throttle sensor ,
which is made by Weber

I'd like to be able to post some links to the cars that needed those TDD units , but I just watched so many videos ,
and I only picked up on this thread again this morning ..... sorry !
 

Barry Hell

Elite Member
Subscriber
More power to you , that's what I say (y)

I think there is rich seam there , just waiting to be mined .

Some of those restoration fanatics spend silly money on just the electronics parts alone ,
but in some cases , the smarter guys hunt down the very same unit that was used on a way cheaper vehicle
eg. Fiat / Lancia / Peugeot / Renault .

Example : The hydraulic slave unit that works the F1 paddle-shift gearbox on Ferraris
....... was also used on a mid-priced Lancia !!!

On my own bike , all of the sensors needed for the ecu are actually BMW parts , except for the throttle sensor ,
which is made by Weber

I'd like to be able to post some links to the cars that needed those TDD units , but I just watched so many videos ,
and I only picked up on this thread again this morning ..... sorry !
I'll bear the Ferrari tip in mind, thanks 😁
 
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