automatic advancing and retarding of engine timing?

[Cliff Jefferies]

Building an ECU for a bike is a pretty simple affair if you know electronics. You simply need to charge/discharge a capacitor at a specific interval. I'm told the two most important things are keeping the unit at an ideal temp (i.e. cool) and signal propagation delay (which is why the wiring loom is the length it is).

Thats old school thinking even it is correct. True the electronics is next to trivial. A single FET transistor will single handedly drive an ignition coil nowadays.

Today its about software/firmware and features.

Hi all.

Its strange this thread has just popped up as I'm currently developing an ignition system for the "older" bikes. The first prototype has gone on to Rob Johnson's ( of AIGOR fame ) road guzzi and soon there will be one on his race bike. The aim is to have a simple system where the rider will be able to select from a number of builtin advance curves. Input can be taken from a number of sources, points, halleffect/optical and reluctor. Anyway end of SPAM. Its not ready yet.

Bikes that have points or other digital input probably don't
do any advance. It is too hard to predict when to spark from the last trigger. My first attempt to run on Robs bike did try this. Above 3000RPM it seemed to run quite well as the flywheel keeps things consistant. Towards 2000RPM it started getting rough and would die off suddenly with a few backfires. This was running only one of the two cylinders and running off the standard points.

Those bikes with coil type pickups can do some advance as the pulse is stretched over time and you can choose the point on the pulse to trigger off so as to change the advance.

Most EFI bikes get many pulses during the cycle so can easily keep track of where the motor is at.

The only bikes I know of that have variable timing are the late model HD and they do this with a knock sensor. Perhaps some BMWs do something fancy also.

A new better technique is to measure the current through the sparkplug ( driven at 400V DC ). This allows you to indirectly measure the pressure within the cylinder. You can then position the pressure peak to be around 20 degrees after TDC to maximise the power. Advancing till it knocks could be too advanced.

[pete376403]

If you were to use methanol in a injected v twin, then the oxygen rich mixture will change the exhaust temp ( usually around 1425 ish ) which will fool the ecu in to injecting more or less fuel ( I cant remember if you use larger or smaller jets in a methonol carb bigger I think ....ie the INjection system will compensate ..not the cdi ......( as motu said the closed loop system will delay signal letting it fire the coil at the most suitable advance/retard position)
Stephen
BTW methanol doesnt like aluminuim I think . becareful ......

Methanol jets need to be MUCH larger than for petrol - ideal ratio for petrol/air is around 12 - 13:1, for meth it's more like 5 - 6:1. Further meth doesn't contain anywhere near the same amount of energy for a given amount as petrol (which is why you need so much more of it) and it runs a lot cooler. If that doesn't confuse the computer, go for it. And meth will live in an ally tank ok (my speedway bike used the same tank for years).
On the plus side it's very difficult to get a motor detonanting with meth, so the compression ratio can be very high, 14:1 or more. The high comp helps the speedway bikes achieve the acceleration which they need out of the gate and out of the corners.

[Brian d marge]

Methanol jets need to be MUCH larger than for petrol - ideal ratio for petrol/air is around 12 - 13:1, for meth it's more like 5 - 6:1. Further meth doesn't contain anywhere near the same amount of energy for a given amount as petrol (which is why you need so much more of it) and it runs a lot cooler. If that doesn't confuse the computer, go for it. And meth will live in an ally tank ok (my speedway bike used the same tank for years).
On the plus side it's very difficult to get a motor detonanting with meth, so the compression ratio can be very high, 14:1 or more. The high comp helps the speedway bikes achieve the acceleration which they need out of the gate and out of the corners.

Yes I couldnt remember which way round it went, and I had often wondered about why the Speedway bike all ran high comps ,,,,,So my 5.5 to 1 Enfield is eerr out of the running then .....

Thanks

Stephen