Cavi Mike, its the 9th post back from the end of the thread. It is difficult 4 me, I'm totaly computer illiterate & post from phone. I lost phone the other day & had a hard time configuring new 1, then didnt know how 2 enable cookies so couldnt log on 2 answer u, sorry mate. When I went 2 school I dont think the school even had a computer, let alone students. Cheers
modified cdi and cr 80 coil
- Thread starter damo99
- Start date
crmachineman
New Member
You're talking about this post and this image?
http://motorbicycling.com/showpost.php?p=298658&postcount=32
Excuse me Cavi Mike, this is interesting; is this some type of amplifier to boost the input to the coil? Looks really cool. I just ordered a DC fired race CDI for scooters and such to run my 66cc unti. I will run a small 12volt battery in a rear compartment to power the ignition. Are you guys essentially building your own CDI ?
Thanks
Yes, its a CDI, the 1 shown in that pic is not the CDI this thread was created for, go back thru this thread (page 17, 6th post, by Headtrauma, posting 4 Ivan H) for the schemtic & tips on modifying 2 suit ur own needs, or go to pge 43 of "roll ur own CDI" for schematic (note, the redrawn schemtic has 1 small error in the scr's kathode circuit), pics of both sides of the board & layout. Perhaps someone computer proficient could lift them over 2 this thread. I'm not, I had 2 snail mail headtrauma the origonal hand drawn schematic to get it posted. Cheers
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Ok, I thought I'd revive this as it an integral part of getting the power/smoothness I've got from the reed app that I have posted development of in the thread "Reed Kit" in the Hi Performance Tips section. This cdi will run fine as is, a little more advanced than the Jag, the retard kcks in at about same. To bring 2 Jag spec u need 2 reduce 27ohm pull down resistance to 16ohm. Also add a 220 ohm & jumper 2 earth in parellel 2 the 120ohm. Outta phone screen, nother post
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In between the Kathode & Gate of the SCR u need a 1k ohm & 390 ohm in series. The resistor in the R/C timing network is increased from 620 ohm to 760 ohm to keep the retard curve kicking in @ same time. Either 1 off the 2 CDI's will give smoother, more powerful opperation, on any China motor. U will need an external coil, CR80 gives hottest spark. The schematic is on Page 17, 6th post, this thread. Cheers
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CroMagnum
Member
Keep in mind that posts per page are selectable in the UserCP, so "Page 17, 6th post" doesn't work when the entire topic is only 5 pages long. Maybe you should use the post number in the upper right hand corner as a reference instead. For instance mine is #195.
Ok, the origonal schematic is Post #166, this thread, by Headtrauma, posting for Ivan H, thankyou very much Headtrauma, or it still wouldnt b on here. If u want it to the Jag spec c post #193 & #194, this thread, I have posted those values. Either 1 works fine, or u can try changing values, the circuit is pretty forgiving, within reason. Cheers
dracothered
New Member
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Ok, so u've got jumper selectable 16 & 27 ohm pulldown resistance with the A jumpers in parralell. I ran my first 1 with 27 pulldown & 1k+100 ohm in series between gate & kathode. My second built (jag spec) uses 16 ohm pulldown & 1k+390 ohm in series between gate & kathode. To have selectable pulldown u also want selectable 100 ohm or 390 ohm to keep the timing of right. Good job. Cheers
the easiest way would b 2 have 1k, 100 & 390 in series with jumpers bridging both the 100 & 390. Then u could select 27 pulldown, leave the 100 unbridged & bridge the 390, or select the 16 pulldown, bridge the 100 & leave the 390 unbridged. Both would need the ability to be bridged but u'd only need 1 jumper as 1 would always b bridged & 1 not. I like how u've made the pulldown selectable, I hadnt thought of. Well done. Cheers
dracothered
New Member
Is the above layout correct for the CDI that I posted? What should be changed on it to fix it or make it more tunable?
Yeah, ur all good, just do like I said with the 1k, 390 ohm & 100 ohm with jumpers in paralell with thr 390 & 100 ohm. Im gunna do 1 like coz u've made it so u can advance the timing where with just the 2 A jumpers in paralell with the pulldown it only retards so u've made a lot more combinations possible. The charge caps r X2 type 275VAC polypropylene. The timing caps r 35V Tantalum. Note they r polarized, marked +, which must go to earth. Cheers
dracothered
New Member
Ok here it is with all the jumper and up dated parts...
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Now that Dracothered has sorted so timing can b advanced we need 2 know its not 2 far advanced. Ur plug is a good indicator. The sides of the center electrode should have an all over even covering of tan oxide. If the very end 1/2 mm or so shows a band of bare metal the timing is a bit 2 far advanced & the heat generated from this has burnt the oxide off. Advancing the timing can make good power but u dont wanna hole a piston. If u've ever got the motor apart, look at the underside of the piston crown. If its black from burnt oil ur running 2 hot. Cheers
dracothered
New Member
I'm not 100% sure which jumpers do what, so if you could clear that up I will up date the drawing so everyone knows what ones do what.
ok, test 2 set overall timing under low RPM load (acceleration). The most advanced would b to select the 27ohm pulldown, no other jumpers tho it may b 2 far advanced. U could bridge the 100 ohm 4 next most advanced but bridging the 390/100 unbridged is the most advanced I've used. Add either the 120 ohm or 220 ohm will retard it by about 3 or 6 degrees. Outta phone screen, nother post
Now we get 2 Jag spec. Select 16 ohm pulldown. 4 a bit more advance leave the 100 & 390 unbridged, tho 100 bridged/390 unbridged is stock Jag spec. Again, add either 120 or 220 ohm will retard roughly 3 or 6 degrees. If u add both it will retard a bit more. I imagine that between all settings there will b some overlap. 1 more post. Cheers
Ok wotever setting gives best low RPM performance is the right 1. Both 0.47uf caps could b on jumpers if u want tho 1 is good enough. Adding steepens the Hi RPM retard curve. Test 4 position @ WOT windout 4 best speed. Start without jumpers then add 1 @ a time if u use 2 jumpers. Highest speed setting is the right 1, button it up. Thanks heaps Dracothered, u've been invalueable. Cheers
Hi, the way I said 2 add the 120 & 220 ohm jumpers is back 2 front. Add the 220 will retard a little, the 120 about twice as much, the both 4 twice as much again. 4 people in Oz wanting 2 build, components r instore or online thru JAYCAR. Polypropylene charge caps r catalogue No. RG-5240, $2-50 each. Timing caps r catalogue No. RZ-6640, $0-65 for the 4.7uf & RZ-6626, $0-60 for the 0.47uf. The 1/2 watt 1% metal film resistors r there for a few cents each,, as is the prototype board @ about 4 bucks. Cheers