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Banjo

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Hi Geoff,

               I dragged out a few bits & pieces, so you can clearly tell whether the ebay dizzy you have purchased, is an equivalent to the small Denso one, or the larger Bosch one.

DSC01457sm.jpg.e0429e4c603e6a9ccd68ec186af4f784.jpg

The dizzy on the LHS is the Bosch one, with a CAS module inside.

The middle housing is the Bosch one, without the CAS fitted.

The far RHS housing is the smaller Denso one

The bottom S.S. disk is suitable for the CAS module on the far LHS.

DSC01456sm.jpg.6134086d2d482e674bcd938d7e9cb5bc.jpg

 

DSC01461sm.jpg.312819f0012f6213230d33e3eb1c7a4f.jpg

DSC01463sm.jpg.53983e16406cc368cf165faf2a05507d.jpg

The inside diameter dimension of the Bosch casing is 75 mm.

The inside diameter dimension of the Denso casing is 60 mm.

The outside diameter of the CAS module is 65 mm.

The outside diameter of the S.S. slotted disk, is 50mm.

DSC01464sm.jpg.b39f08667cf40c8edb684621c15e93b2.jpg

This picture directly above indicates that the disk itself will fit inside the smaller 60mm I/S Denso casing. However, the CAS module O/S diameter dimension is 65mm, so you definitely need the larger Bosch dizzy housing.

Hope this assists.

Cheers Banjo

 

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Hey Banjo, 

    thanks for the update, that is a huge difference in the sizes and the cas looks like it needs the bosch dizzy to fit. 

    However if the dizzy i bought was too small i was going to hack it off at the red line, and in the tafe class i would use the lathe to turn out a new body large enough that i can bolt on to the base of the dizzy left after i cut it off. hopefully its just tapping the holes in the base and using some screws that can go through the cas sensor, through the new body and into the base of the dizzy.

image.png.1d4dc1e302e3848538bc50734361916b.png

    so once tafe opens again I will continue the machining course, or until i can get a lathe at home and then try turning this out myself. however I work in IT so the electronics and wiring is the easy bit for me, the mechanical and machining is the learning. The only question i would have is the base is steel and i would most likely turn out am aluminium part so i am a little concerned of galvanic corrosion so i might put a brass plate in there to stop that. 

Edited by wenisman
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Hi Geoff,

               The dizzy you purchased off ebay, is the best dizzy, for a Standard Rolla engine.  It is not an olde "points type".  It is an electronic type, with a reluctance sensor.

It would be an absolute shame to hack it up.  Someone on here, will certainly take it off your hands.  

It certainly would be neat to turn up a complete housing for a off-the-shelf CAS, with lid to suit.

Bear in mind that the cases for the dizzies are of a cast aluminium/dicast construction.  There is a bush/bearing pressed into the shaft extension, at the bottom.

The base of the case is not very thick, as you will see, when you receive yours.  They all have a little hole in the bottom, to drain away any engine oil, that makes it's way up into the body via the shaft.  You can guage the depth of the base, by looking at this hole/s.  (some have two holes)

I would cut it off, just up the side wall a little, & then turn a body to suit, that could step out, like the Bosch dizzy body, to accommodate the larger diameter CAS.

It might be an interesting exercise to find an existing CAS, with the smallest overall diameter.  You could then use the smaller Denso dizzy body.

I've got plenty of those you could have for free.

Maybe someone reading this, has already discovered a CAS module with O.D. < 60mm, that could fit inside a Denso dizzy case ?

Cheers Banjo. 

              

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Hey Banjo, 

    whilst trolling the interwebs i found that you can get smaller pickups like these, its just the sensor without the bottom plate

https://www.alibaba.com/product-detail/Brand-New-J520-Ignition-Control-Crank_60702769841.html?spm=a2700.8267363.selected.1.2ce43e5f4meR3c

 

    i am not sure what the minimum disc size that is required but I&#39;m asking the guy selling them to see what we can get away with. this might be enough to fit inside a denso style with a 50mm disc or maybe even 40-45mm just would need larger holes cut in it? although i think this is an optical sensor, i am not sure if the sr20 cas is an optical or hall effect?

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Hi Geoff,

                It would be great if we could source a smaller CAS module.  Let's see what we can find out there.

Please have a look at this technical video from the Haltech guys.

https://www.youtube.com/watch?v=mh4hxnfMfGA

 It discusses a problem, I have been experimenting with, by using the larger number of teeth on the flywheel ring gear, rather than a small toothed wheel attached to the crankshaft pulley.

The problem they are trying to overcome, is the "flex" in toothed rubber timing belts, at high revolutions.  The K series engines are to some extent free from this problem, as we have a chain & sprocket driving the camshaft.  However, as we all know, you can get "slop" in the chain when they are old & stretch, or the oil pressure driven tensioner, doesn't perform as well, as it used to.  There is however, a way to overcome it, by adding a second single pulse from the crankshaft, that produces two pulses per engine cycle, (in our 4 cylinder engines) &  "AND" those 2 pulses with a "covering" pulse from the camshaft "Home" pulse, which results in a single "home" pulse per cycle, sychronised to the crankshaft, & not the camshaft.  In that way any slight flex or slop, in the camshaft home signal is irrelevant, in terms of timing accuracy.  All that is needed is for the camshaft pulse to be slightly longer, & overlap the crankshaft synch pulse.

However, if you go waste spark, you can time everything off the crankshaft, if necessary, & not need any camshaft sensor at all.

I know it sounds a bit complicated, but it really isn't that hard.  I've tested it extensively, & am now just getting the pulse width & overlap fine tuned mechanically, so there is no need to actually adjust anything.  The result is a very reliable & accurate synch or home reference signal.

Cheers Banjo

 

 

 

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