Generating an ignition spark with no ecu 2

[DanielHowden]

I wonder if anyone can advise me on a project I am working on. To cut a long story short I have an engine that I am converting from injection to carburetor.

My question is how do I produce a timed spark without using the ecu? From the research I have done I should be able to use a separate ignition control module, being far smaller than the massive stock ecu. However I am unable to get any further information on this.

If anyone here can help it would be great to hear from you or maybe some direction to some reading material I haven't found.

Many thanks, Daniel

 

[MikeHalloran]

Study a bunch of old shop manuals, especially the ignition wiring.

We might be able to help more if we knew which engine you are converting.

Since engines of all sizes now come with EFI, I'm intensely curious about why you would go back to the stone age. Please tell us the backstory.




Mike Halloran
Pembroke Pines, FL, USA

 

[DanielHowden]

So I love carburetor engines, I know about carbs and I kind of like the traditional look of it. This is a project I am working on using a Triumph Daytona engine from 1997, it was designed as an injection engine but I am trying to run it from a carb.

I know this may sound a little crazy but it's just what I like to do but electronics is not my strongest skill and I always have to learn on the job.

Thanks for the comment.

Daniel.

 

[BrianPetersen]

The traditional way, dating back decades, was to use breaker points and condenser (= capacitor). Normally these would be installed inside a distributor with the high-voltage spark plug wires going from the distributor to each spark plug.

Motorcycles traditionally did not use a distributor but rather ran "waste spark" in which a set of breaker points operated by the crankshaft at crankshaft speed were connected to ignition coils that fired the spark plugs once per revolution whether they need it or not. On a 4 cylinder there would be two coils and two sets of breaker points, one dedicated to cylinders 1 and 4 and the other to cylinders 2 and 3.

Breaker points are a pain in the tail, and on a high revving engine with wasted spark, you may not be able to get sufficient dwell time (coil "on" fed through the breaker points) to get a strong and reliable spark at high revs. If you want the engine to run halfway decently, you will need at least a centrifugal advance mechanism.

If you can accept having some electronics, you can get stand-alone ignition systems,

http://www.dynaonline.com/

I have no idea whether those are compatible with your existing crank position sensor.

 

[MikeHalloran]

I'm old. To me, a Triumph Daytona is a twin, not a triple.

All the photos I could find so far show a full fairing, and behind that, two pairs of top tubes enveloping the engine intake tract, so I don't see anything to 'look' at.

Perhaps a photo of your particular bike would help me see what you are talking about.

Guessing you want a cafe racer look, I'd be inclined to slice a pair of Keihins or Amals on their vertical centerplanes, and just wire the resulting half shells over some plain pipe in the outer intake tracts.

I would not give up EFI.



Mike Halloran
Pembroke Pines, FL, USA

 

[DanielHowden]

Thanks for the replies, yeah I guess this might seem like an odd thing to be doing but it keeps me occupied.

I am still looking for a solution but also looking at the DynaTek offering, thanks for the link.

Any more input here is greatly appreciated.

Thanks, Daniel.

 

[dgallup]

Why not use the existing ECU? It should keep working with the injectors disconnected. Anything else is going to require some calibrating to get a decent ignition advance curve.

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[dgallup]

Mike - Triumph has used and reused the Daytona name over and over. It's been everything from a 500 cc twin to a 1200 cc four with many many displacements in between and lots of 3 cylinder variations.

This list doesn't even have the latest variant as they have upped the displacement of the 675 triple to 765. They will be supplying all the engines for Moto2 starting next year.

https://www.autoevolution.com/moto/triumph/daytona/

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[DanielHowden]

I don't want to use the existing ecu because its the size of a brick and I have nowhere to hide it as this is a custom bike.

I never thought this was going to be easy!

 

[dgallup]

Take a look at the previous model, the '95-96 900 cc Triumph Daytona 900 Super III. It's carbureted so you may well be able to steal the ignition system from it, probably the carbs too although you may want something more exotic for a custom. Triumphs typically evolve slowly and reuse lots of parts. Even when parts get updated the interface remains the same. Or even easier just start with a '95-96, then you have nothing to remove.

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[MikeHalloran]

I thought about suggesting burying the ECU in a pocket in the bottom of the gas tank, or maybe in a phony oil tank in the traditional location, but on second thought, it probably needs some airflow over it to keep the electronics alive, so I'd recommend leaving it no less exposed than whatever is done on the stock bike.


Mike Halloran
Pembroke Pines, FL, USA

 

[DanielHowden]

Take a look at the previous model, the '95-96 900 cc Triumph Daytona 900 Super III

This is a great idea and something I hadn't looked at. Thanks.

 

[bradrs]

What are you going to use for coils?

The dynatek stuff will work, but if I recall correctly, they are designed for inline 4 where the cylinder spacing is equal.

FWIW, if you can find some details on it, there was a 97 Triumph Daytona that ran with carbs in an AMA Racing class, I think it may have been Pro Thunder class, by Orange County Triumph. I think it retained the stock ECU for timing, used a dummy load to make the ECU think the stock coils were still there. It initially had an MSD-6AL CDI/rev limiter on there, but was swapped to a Dynatek DRL-300. They(orange County Triumph) did sell a few conversions for carbs too.

If you are going for a clean look, I think I've seen some trigger wheels that had an centrifugal advance mechanism built in to it. Those would basically fit on the end of the crank to work with a crank trigger. You'd probably need to do some adapting to make it fi though, I don't think they were Triumph parts.

 

[TugboatEng]

Motorcycles since the 1980's have all had Capacitive Discharge Ignition before ECU's. They can be quite small depending on how many curves you want. It's also something you can repurpose or build yourself. They're triggered off a magnet on the flywheel and a Hall effect sensor if I'm not mistaken. The FI engine may already have everything required. CDI ignitions don't even require a rectifier regulator. They're common on dirtbikes and can run on unregulated AC or DC.

 

[bradrs]

If you try to run a magneto style CDI(unregulated AC input), you would need to get the magneto voltage to charge the capacitor somehow. It should be in excess of 200V AC. This is not the right way to do it, unless you are planning to entirely dump your charging system too. But if you are still running lights and not converting it to kickstart, you probably want to keep the charging system.

A 12V DC CDI as found on some dirtbikes will charge the capacitor from 12V, and just require a trigger mechanism. But few CDI boxes will have 3 individual coil outputs and triggers. Most of the 4 cyl ones were waste spark, only 2 channels. Adapting this to the 3 cylinder firing pattern will probably cause some issues.

Using the older Triumph ignition would probably work better than using a CDI box from some other application.

 

[LadaTrouble]

The original Britten used a couple of chainsaw ign systems - a chainsaw flywheel on the end of the crank, and a couple of coils in the appropriate places. Simple as, as we say here.