automatic advancing and retarding of engine timing?

[Motu]

All the ones I've seen on cars just use a simple AC generator like an ABS sensor - but like I said...I just work on cars.

[k14]

Don't electronic speedo drives use the Hall Effect? Or is it something similar?

Yep the induced emf from the magnet passing a coil can be detected and converted directly a frequency and thus converted to speed knowing the circumference of the wheel.

I thought that most ignition systems are triggered from an inductive pickup that senses off the flywheel. Then the signal from the inductive pickup goes straight to the coil which then goes to the sparkplug. Think thats how it works on my rs anyway, could be different when there is a battery etc involved.

[Ixion]

But they are German though eh...quality before quanity,unlike their competitors,and in bed with Robert Bosch.Hall effect generators are delecte and a motorcycle enviroment is a bit harsh for them....unless of course you are using car technology in your bike like BMW does....I suspect the hall effect will be tucked away under the front cover nice and safe.

Buggered if I know where it is. I don't understand it or how to fix it. And bits on bikes that I don't understand or know how to fix, I close my eyes and pretend they don't exist. And go back to playing with stuff that I understand .

This prevents me form getting into deep shit meddling beyond my capabilities.

[Ixion]

..Despite having umpty-zillion sensors, there's no knock sensor, and as far as I know, no bikes have them, so you just have to make sure you're using the right fuel for your bike, which would be 91 in your case, I would imagine.
..

BMW K1200 has a knock sensor (of "new advanced type" whatever that means). Not sure about earlier models, I'd have to go read the manual , which is where I'm not. There's certainly a shit load of magical stuff, all of which the manual indicates is out of bounds for mere mortals.

[vifferman]

I thought that most ignition systems are triggered from an inductive pickup that senses off the flywheel. Then the signal from the inductive pickup goes straight to the coil which then goes to the sparkplug. Think thats how it works on my rs anyway, could be different when there is a battery etc involved.

Most bikes just fire whenever the inductive pickup causes a pulse, even if the cylinder is on an exhaust stroke, as it doesn't matter. I think they use a spring-loaded plate to vary ignition timing if they don't have an ECU.

The VFR has an ignition pulse generator, which generates a small voltage (less than 0.7V) which is passed to the ignition control circuitry in the ECM, which then sends pulses to the coils, based on other information from another sensor on the cam that tells the ECM what position each cylinder is in, and the program for ignition timing vs. engine revs, throttle position, etc. But no allowance is made for knock.

[vifferman]

This prevents me form getting into deep shit meddling beyond my capabilities.

Until Mrs Ixion says, "You can feex stuff! Just do eet!" (in the pseudo-Cajun accent of that guy on "The Waterboy".

[F5 Dave]

Unless the system has a piezo detonantion sensor & closed loop ignition then it won't adjust to the petrol. Take it as it won't. 91 will be just dandy & if you are coming from a GN250 then a bicycle will feel overpowered so how 'bout worrying how to ride it.

[TwoSeven]

[The following is just my opinion – I’m still learning about this area, so it most likely is total bollox].

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).

As to knock sensors; knock will cause incorrect ignition (pre-ignition) which means the fuel won’t be burnt properly - the O2 sensor will pick this up if you have one. However, it’s not just as simple as that - the air/fuel ratio that bikes require runs over a huge range depending on temperature of the air and the engine, throttle setting and velocity of the machine. For example, try something like 4:1 on starting, 8:1 on idle and 16:1 on 3/4 throttle stationary, 14:1 on full throttle (not adjusted for variation).

To start measuring that you need to start adding more sensors to the bike, certainly a modern machine should have a throttle position and O2 sensor in it. That makes your ECU more complex as you now need to send a signal to the injectors before sending out the ignition signal. This is done by using a map of pre-set settings (a linear map). But if you want to change the settings for each individual cylinder (say because the inner ones run hotter than the outer), then you need to have a map for each cylinder (a 3d map). Using a map means you don’t have to measure sensors (which takes time) and it also means you don’t have to perform calculations (which also take time). Remember, at 14,000 rpm you have to make about 60 measurements and calculations per second (roughly).

Changing the type (methane/ethanol etc) of fuel has no real bearing on octane rating since that’s just a measure of the iso-octane a fuel has in it. 0% octane rating means you have a ratio of 89% percent iso-octane (2,3,4 trymethelpentane) to 11% n-heptane (dypropyl methane). 100% octane rating means you have no n-heptane in the fuel. The objective of the mix is to create a detonation wave that propagates at a fixed rate (too fast or slow and the power wave will be buggered) and at a desired temperature with a desired heat output/absorption. You can use any mix of alkanes to do this but the petrol mix is generally the most efficient. (You can find all this info in the wikipedia).

You can’t get higher than 100% octane rating no matter what you add to it. The effect of moving to ethanol or methanol just means that the fuel has a higher cooling effect on the engine - you will lose power because it has a lower BTU rating and it will also change the speed of the detonation wave. Cooling the engine more means you can move to a higher compression ratio or you can use more fuel (the latter results in higher compression ratio but more stuff to go bang and more cooling which is what dragsters require whereas road bikes require the former)

Changing the octane rating in petrol doesn’t cool the engine as much as using ethanol, instead it’s the opposite. It allows you to raise the temperature of the engine and therefore the temp at which ignition of the fuel occurs. The only way you can raise the temp of the engine is to raise the compression.

However, raising the octane also raises the base temperature at which ignition won’t occur (i.e. if its not warmed up, you wont get ignition - you'll notice this sometimes on bikes where a cylinder might not fire on cold mornings until the bike gets warm, then it kicks in). This means you need to change your plug to cope with the new heat range - since an NGK9 plug works at around 400-500C (91 octane at about 11.5:1 compression), going to 96 octane at 11.5:1 would mean the engine would never get hot enough (wouldn’t burn efficiently) to ensure the plugs self cleaned themselves hence the cold fouling. If you raised the compression (and therefore the heat) of the engine to say 12.5:1 then you'd be back into the operating range of say an NGK 7 (I cant remember the heat numbers for the plugs sorry) at about 600C which is well within the plugs self cleaning range and operating temp (400-750C).

Anyhow - back on topic. A slight trick to changing the compression and therefore the heat range the engine works at is simply to retard or advance the ignition. Since peak compression say 12.5:1 occurs at TDC advancing the ignition 5 degrees means that compression may be as low as 12:1 or even 11.5:1 depending on the machine. As you can see above, that greatly reduces the heat range that the engine operates at and also the power/torque figures. (Also, increasing octane without increasing compression is the same as retarding the ignition a few degrees). Building this functionality into an ECU suddenly makes things well harder because you need even more sensors on the bike. Having such a wide variation in heat ranges would also make your plugs say nuts as well.

Also, I guess, if you want to get nice and precise, you'll need to ensure that the spark wave front arrives at the piston crown just after the piston has passed TDC (so you’ll need to tune the detonation wave). Otherwise, if its too early, you have a spark wave front arriving on an upward moving piston (that’s effectively going to slow it down and in extreme cases burn a hole in the crown) or a wave front that is chasing the piston down the barrel (and cooling resulting in sooting up if the mix is too rich). That means there is a minimum and maximum advance/retard setting that you can use in the engine (I think Honda only allow 2-5 degrees on cibby engines but am not sure).

So in answer to the original question an 11:5:1 ratio engine is likely to be tuned to run on 91 octane petrol using an NGK 8 or 9 plug (If I remember the temps correctly), and changing the fuel content will likely lose you power. The auto retard/advance feature is probably only there to cope with the heat range the engine is designed to go thru.

[scumdog]

BMW K1200 has a knock sensor (of "new advanced type" whatever that means). Not sure about earlier models, I'd have to go read the manual , which is where I'm not. There's certainly a shit load of magical stuff, all of which the manual indicates is out of bounds for mere mortals.

Speaking of which, where in the South Island is a BMW dealer with the BigBoxofMagic that a late model BMW bike can be hooked to for TuningRepairAndAnalysisOf Problems?? Mate of mine reckons there isn't one south of Christchurch.

[Brian d marge]

Most bikes just fire whenever the inductive pickup causes a pulse, even if the cylinder is on an exhaust stroke, as it doesn't matter. I think they use a spring-loaded plate to vary ignition timing if they don't have an ECU.

The VFR has an ignition pulse generator, which generates a small voltage (less than 0.7V) which is passed to the ignition control circuitry in the ECM, which then sends pulses to the coils, k.

You know , Dont you just hate it when you feel comfortable with a bit of info , and then 20 years on you have to drag that rusty bit of info from the dark recesses and have a fresh look at it ....

Honda uses both types of ignition , Hall effect and inductive ( I remember the course at honda ...when the I think it was the fireblade( cant remember the model for sure and I dont have the course note at hand ) , and the reluctor ring had changed from 8 or so vanes to 30 odd ( thats why they were harping on about it), now that used a hall effect pulse generator which produced a square wave with a large gap between the reluctor vanes to tell the engine I have done one revolution ie reset the Ecu
As motu says hall effect are delicate , so most use a inductive pickup where the magnetic field is pushed out of the way by a lump of metal causing it to trip( move over) over the wire which is wrapped around a soft iron core causing a current to be created in the wire which then heads off to the ecu .
Now I had a quick trawl through the internet , but there is so much rubbish out there I havent the time to do a complicated search.

I will see if I can locate my notes , ( you know I can see the page in my mind even the location of the picture explaining Hall effect , but stuffed If I can remember the model it was for !!!)
Hall effect btw is when a current flows along a conductor ( usually silicon ) and a manetic field is close by ....all the smoke dust ( see images section for picture of Lucas smoke) , well they all try to move away from the magnetic field ie to one side of the conductor , in doing that they create a voltage difference small but noticeable and at right angles to the current ( smoke) originally flowing,,

I know the original post was about advancing /retatding for differing gasoline , But Motu made me think
I am always up for a reality check now and again ...thanks for that ....

It bugs me , you know when you can remember something clearly, but not quite all of it .... Stufff.....must be getting old ...or was it a mis spent youth , cant remember now
Oh well happy days

Stephen

[vifferman]

As to knock sensors; knock will cause incorrect ignition (pre-ignition) which means the fuel won’t be burnt properly - the O2 sensor will pick this up if you have one. However, it’s not just as simple as that - the air/fuel ratio that bikes require runs over a huge range depending on temperature of the air and the engine, throttle setting and velocity of the machine. For example, try something like 4:1 on starting, 8:1 on idle and 16:1 on 3/4 throttle stationary, 14:1 on full throttle (not adjusted for variation).

On closed loop, the VFR uses two sensors - one for the two left cylinders, and one for the right two. However, closed loop is set up to run ultra-lean to meet EC and US emissions testing up to 2008 or summat. And it uses the O2 sensors only if there's no stored data (ie., the ECU's been reset).

To start measuring that you need to start adding more sensors to the bike, certainly a modern machine should have a throttle position and O2 sensor in it. That makes your ECU more complex as you now need to send a signal to the injectors before sending out the ignition signal. This is done by using a map of pre-set settings (a linear map). But if you want to change the settings for each individual cylinder (say because the inner ones run hotter than the outer), then you need to have a map for each cylinder (a 3d map). Using a map means you don’t have to measure sensors (which takes time) and it also means you don’t have to perform calculations (which also take time). Remember, at 14,000 rpm you have to make about 60 measurements and calculations per second (roughly).

Phew!
Lotsa sensors on the VFR: external air temp, throttle position, O2, airbox pressure and temp, road speed, cam position, revs, engine temp, barometric pressure...
Then it uses three 3D maps for each cylinder for fuelling. It's supposedly good for up to 16,000 RPM.

But there are problems with the programmed logic - one is that the 'closed loop' mode is too lean, and the other is that in the interests of fuel economy and emissions, the ECU likes to shut the throttle completely if you back off the throttle at low revs, necessitating some clutch-slipping or modification of riding technique in some situations. (Best one is to keep the revs above 5K).

However, raising the octane also raises the base temperature at which ignition won’t occur (i.e. if its not warmed up, you wont get ignition - you'll notice this sometimes on bikes where a cylinder might not fire on cold mornings until the bike gets warm, then it kicks in).

That's interesting.
This would explain why the VFR's a bit reluctant to kick into life running on 98, now that it's getting cold? It was better this morning, as I chucked $10 of 91 in the tank yesterday, as the blinky thing (tech term) was blinking, and I was in a hurry.

[Motu]

Speaking of which, where in the South Island is a BMW dealer with the BigBoxofMagic that a late model BMW bike can be hooked to for TuningRepairAndAnalysisOf Problems?? Mate of mine reckons there isn't one south of Christchurch.

The Bosch Hammer maybe - it's used on cars,no problem to have bike data on it too.Most expensive usless piece of diagnostic equipment you can get - Bosch lock them into it...you can be a service agent,or a parts agent,not often both,neither can access the others data,they charge a shit load for the CDs and the diagnostic gear and from all I have heard everyone who has a Hammer is spewing.

I was talking to my diesel man yesterday and he's full of woe - common rail,it's here and will have taken over in 5 yrs.Bosch control it - they will have a service agent in Auck,Wellington and ChCh,no one will be able to asscess information and parts unavailable to any but an authorised service agent.Robert Bosch let diesel technology slip out of his hands once....never again.

[thehollowmen]

Speaking of which, where in the South Island is a BMW dealer with the BigBoxofMagic that a late model BMW bike can be hooked to for TuningRepairAndAnalysisOf Problems?? Mate of mine reckons there isn't one south of Christchurch.

Doesn't Honda otago (formally uptown motorcycles) in Dunedin have one?
they sell lots of BMWs so I'd be surprised if they didn't.

[Pixie]

I know this sounds really silly, but how would I tell if the CDI is able to advance or retard my timing automatically?

I pick up a 11.5:1 650 fuel injected V twin tommorrow and I'll get less power on 91 if it retards the timing. On the other hand I could get a small amount of SDA (alcohol + small amount of methanol) from work to boost the octane (the manual says 10% etOH or 5%mtOH in petrol) and if it advances... happy days for me!

If your bike is fuel injected it will have a fairly sophisticated ignition system too.Taking advantage of the ECU for the fuel system.
It will have a thottle position sensor and the advance curve will be mapped.
Even the humble Bandit has a TPS and it has carbs.
Very few electronic ignitions are CDI -on road bikes.Transistorised switching of 12 Volts to the coils is what they do.
CDI's dump higher voltages into the coil's primary windings,Up to 300V.

[Pixie]

Don't electronic speedo drives use the Hall Effect? Or is it something similar?

It need only be a reed switch