Stock RB dizzy internals

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Poida
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Post by Poida »

Yes, in the S.C./Jaycar programmable ignition kit, you set the advance weight at their maximum advance position which advances the "cam plate". I disconnected the vacuum advance totally but you can also setup a microswitch that signals when a load is being placed in the engine. From memory the total advance is 45° (crankshaft) and the programmable module sets the actual advance curves according to engine revs and the vacuum signal if you use that as well.

It reads the dissy signal at 45° BTDC and waits the programmed time period then fires at the prescribed point, continually adjusting as the revs rise or fall. The curve can be programmed to begin rising at a base rev point, then it rises to a programmed rev point for the first sequence, it then continues to rise, or fall depending on how you want the curve, till it peaks at another set rev point. The beauty of it is you can change advance curves on the fly with a few keypad moves. The chip can hold two different programs and can be switched between the two at a moments notice.

When the engine first starts the circuitry retards the ignition 45° (crankshaft) so it's firing at TDC till the engine revs reach the base rev setting. It then switches to the programmed mode.
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Post by Josh »

Yeah I just had a look at them jaycar kits... I might give it a go, Jaycar stuff is pretty reliable and it says it can be used on reluctor type systems
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Post by FieldEffect »

I disconnected the vacuum advance totally but you can also setup a microswitch that signals when a load is being placed in the engine
Run the vacume line from the dizzy to a MAP sensor instead of the diaphram thing and you have one axis of an ignition map.

K, ill have a crack at the maths, tell me if i stuff somthing up.

So at idle - say 1000rpm or 16.67 revs a second.

Each cylinder revolution or 360 degrees takes 60 milliseconds.

So if i get a pulse at 45degrees BTDC or 7.5 milliseconds BTDC from the points / hall effect sensor / reluctor.

So if i crack open a timer after the pulse, each millisecond i pause after the pulse coresponds to an avance of 45 + 6.

So if i pause 6 milliseconds spark advance is 45 + 30 = 15degrees?
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Poida
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Post by Poida »

Don't need to go to that effort to program the ignition programming device. It's all done in simple form. You need to enter a number of parameters in sequence.

Min rpm 4 digits (point where advance begins)
Mid rpm 4 digits (point where first stage advance ends)
Mid advance 2 digits (degrees advance at point where first stage advance ends)
Max rpm 4 digits (point where max advance ends)
Max advance 2 digits (degrees advance maximum)
Dwell 2 digits (dwell angle)
Vacuum advance 2 digits (degrees vacuum advance)
Cylinders 2 digits (number of cylinders)
Security code 2 digits (security code to unlock for entering programming mode)

An example of a dual curve that might be progranned into the device.

Image

Note that it is possible to actually program the second stage to retard the ignition curve if required
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Post by FieldEffect »

Don't need to go to that effort to program the ignition programming device. It's all done in simple form. You need to enter a number of parameters in sequence.
Urm, i wanted to build my own from scratch. Possibly using an ATMEL microcontroller or similar, so i can add a laptop interface for programming, as many points as wanted, any other ideas i can think of etc etc

Is the maths correct?

Also i had another idea, this was what i was thinking of at work today:

Image

You use the reluctor input as a timing reference similar to the programming ignition kit. Each lobe represents 45 BTDC for each cylynder but it doesnt tell you which cylinder, the rotor button in the top of the cap transfers the spark to the right cylynder.

Say in the distrubutor cap you put 4 hall effect disk sensors and mount them to the wall such that the rotor arm passes into them as it would normally pass the spark to the right cylinder. (maybe retard it alittle so you have plenty of warning which cylinder will fire next)

Now you have an electronic input which defines which cylinder needs to fire next.

The inputs can go to a micro controller which then triggers a coil on plug style ignition system.

No more HT leads! Can up the spark voltage as much as you like without crossfire, plus probably other advantages i cant think of.
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Post by Josh »

Thats way too much f*#cking around for a gemini engine mate

If your wanna f*#k around that much you might as well get a top fueler engine and run magnitos

GOSH

:)
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Post by FieldEffect »

yeah but i wanna build my own electronic ignition dammit.

What better car to try it on that one with $50 engines? :P
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Post by FieldEffect »

If your wanna f*#k around that much you might as well get a top fueler engine and run magnitos
I work on the RMIT formula SAE racer..... but it just doesnt completly fill the void.
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Post by Gem_Kid »

internals fomr an rb dizzy - $50

ford XF module - $7

small heatsink - $2.50

wiring - $2

solder - $2

....

PM SoK.

hes done a few kits.
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Post by ZD1T »

gemkid, where do you get a ford module for $7

and... have you even done this?
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Poida
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Post by Poida »

And how about an RB dissy for $50? Most wreckers won't even consider parting with one for under $100. They know it won't gather dust on the shelf. It's the best selling bit of an RB Gemini.

By the way, you don't need an external module with an RB dissy. They have a module inside the dissy so why would you replace it with an external one?
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Post by Gem_Kid »

pizza wrote:gemkid, where do you get a ford module for $7

and... have you even done this?
sorry typo*

yes. wreckors charged me around $17 for and XF module.

Poida wrote:And how about an RB dissy for $50? Most wreckers won't even consider parting with one for under $100. They know it won't gather dust on the shelf. It's the best selling bit of an RB Gemini.
wreckors sold me it for $64.50, but they gave it to me for $50 as i go there alot.
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Post by FieldEffect »

so is my maths right or what?
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Poida
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Post by Poida »

LOL, I didn't get out the calcy but the theory sounds good. Imagine how many nanoseconds you'll be counting at maximum revs if it advances all the way out to 7k!! Lucky we are working at the speed of light to begin with.
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Post by FieldEffect »

Poida wrote:LOL, I didn't get out the calcy but the theory sounds good. Imagine how many nanoseconds you'll be counting at maximum revs if it advances all the way out to 7k!! Lucky we are working at the speed of light to begin with.
Well in theory the smallest amount you can increment the timer is one clock cycle.

So say at 4MHz: 1/4 000 000 = 0.000 000 25 of a second timing increment.

Aparently formula 1 computing requirments are reaching the limits of what can be produced with semi-conductors these days.

Ill pick some brains at work tomorrow but most late model cars with coil on plug systems (yes im really going to buy a paddock bomb and give it a go, i hate distributor caps and HT leads) are double over head cam and have the spark plug buried into the top of the middle of the cam cover.

The gemmy spark plugs stick out the side and are right near the exaust and im wondering if the surounding area will be too hot for the coil packages?
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