altezzaclub Posted March 4, 2011 Report Share Posted March 4, 2011 (edited) I have moved along and fitted an electronic dizzy, one that KE Motorsport sells. Certainly cleaner at low revs or when cold, and I just added advance until it felt OK. Today I plotted an ignition curve, and I found I was running 18deg static advance to make it get up and go! So I've reduced it back to 8deg and plotted this- One set of figures with the vac unit on, one with the vac unit disconnected, and a Piper dizzy chart for comparison. That is what the Honda Accord uses, and is similar to the other dizzys mapped here- http://www.jcna.com/library/tech/tech0015.html I think the car feels much better with more advance early on, and I wondered who has had theirs re-mapped, what the curve looks like, and who really knows what changing the curve does in each sector... Thge fgures I read were similar to Camerondownunder's specs, 9.5deg at 1700rpm and 13.5deg at 3100rpm, so maybe K dizzys just don't work... http://www.rollaclub.com/board/index.php?app=core&module=attach§ion=attach&attach_rel_module=post&attach_id=68403 Edited March 4, 2011 by altezzaclub Quote Link to comment Share on other sites More sharing options...
Evan G Posted March 4, 2011 Report Share Posted March 4, 2011 one thing ive noticed is 5k electronic dissy in a 4k doesnt feel right? even with the same timing etc etc 5k electronic dissy in a 5k, everything feels like it was made for eachother 4k advance weights must be different to the 5k ones? Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted March 4, 2011 Author Report Share Posted March 4, 2011 That's exactly what I found Evan, from the moment I first drove it with the new dizzy. Flat under 3500, so I just turned the advance up until it went fine around town. I could pull both dizzys apart and compare. Someone will know all about it.. Quote Link to comment Share on other sites More sharing options...
Evan G Posted March 4, 2011 Report Share Posted March 4, 2011 i found with 12 degrees witht he electronic dissy. engine doesnt like going faster than 110. just feels like its running outta puff with the 5k & electronic dissy. was like 20 degree adv. (no hard starting or anything) was halling a 4k in the boot and i didnt notice i was doing 140 in the same spot? Quote Link to comment Share on other sites More sharing options...
rian Posted March 4, 2011 Report Share Posted March 4, 2011 (edited) Altezzaclub I have the same dizzy as you in a 4kc and it seems really sluggish under about 3000rpm, seems to go alright above 3000rpm though. It's seriously annoying when you try to accelerate up a hill, even in the lower gears it struggles to gain any speed on a slope. The timing is at about 10deg and I'm pretty sure the old points dizzy was also at about 10deg as well but just felt like it went faster. I've never been able to do the same speed over hills as I used to when it had the old points dizzy :( Edited March 4, 2011 by rianwest Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted March 4, 2011 Author Report Share Posted March 4, 2011 Do you guys want to generate a timing curve on your dizzys?? We should get a dozen different ones for comparison. I turned the motor with a 19mm spanner to get the timing mark on 20deg, then marked the pulley with a white-out liquid correction pen around clockwise. Then I turned it backwards some more until my 20deg mark was at 20deg on the timing chain cover and marked another 20deg worth, so I had marks on the pulley from zero to 40deg. I held the timing light & my wife worked the throttle and wrote down the readings. Not hard to do, every 500rpm up to 3500 with and without the vac advance. I nearly shat myself when she revved it up past 4000 and it ran off the end past 40deg! It hit 50deg I'm sure! Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted March 5, 2011 Author Report Share Posted March 5, 2011 Here's step one- stock dizzy. If you've never seen under the plate, it looks like this. First photo has the rotor shaft off the dizzy's cam drive shaft. Second photo has it assembled. Those are the springs that control the rate of ignition advance, as those two centrifugal weights move outwards and turn the rotor shaft on the shaft inside it. That turns the rotor more, relative to the cam/crank and works the points earlier, so the spark arrives earlier. You would think that the weights move out to take up the gap and stop advancing when they hit the vertical tabs... but no, max advance is done with the rotor shaft in the 2nd picture having pins into slots of the base below! So, in the third picture you can see the rotating shaft's pins enclosed in red plastic sitting through the base plate slots. (well, one of them anyway) So to get more max advance you file the slot longer. The pin moves 3.4mm in the slot, and they are 24mm apart. So they sit on a circle of pi*24=75mm, and 3.4mm is 4.5% of that, which is 16deg, so max advance is 32 crank degrees... just what I measured yesterday! You can see that the weights and springs control the rate that advance is added, and the slots control the max spark advance you can get. On top of that, the vac advance pulls the points plate around, and ALSO adds and substracts advance. now to get it happening sooner... Quote Link to comment Share on other sites More sharing options...
Twinky Posted March 5, 2011 Report Share Posted March 5, 2011 Would a stronger vacc source do anything worth while? I recently tried using one of those un used ports on the intake manifold, the idle ended up sitting around 15 degrees whilst the original carb source sat at 10 degrees. I have no rpm meter so I can't make a curve as to see any benifits/downfalls in using the source. Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted March 5, 2011 Author Report Share Posted March 5, 2011 I'm going to look at that Twinky, I'm hoping to borrow Rob's vac gauge tomorrow and try the carb port I use and the brake booster vac and plot the differences. You can run a lot of advance at idle as the mixture is so weak it takes a lot to fire it. I think ported vac use came in to do with emission control. Quote Link to comment Share on other sites More sharing options...
parrot Posted March 5, 2011 Report Share Posted March 5, 2011 Just get the dizzy recurved at an ignition specialist. Take all the guess work out of it. Your dizzy needs to be tuned to suit the other characteristics of your engine. You have seen what using a dizzy tuned for a van is doing to your performance. Think how good it will be if you get it recurved properly. http://www.performanceignition.com.au/order-and-delivery Quote Link to comment Share on other sites More sharing options...
Andy43 Posted March 5, 2011 Report Share Posted March 5, 2011 That curve doesn't look right, should be flat lining after about 3500 ???? I think For what it worth, All of our cams have bugger all vac at idle, I found the vac advance plays havoc down low, So I don't use it . On the track the engine lives between 4000 and 8000 RPM, I just set the advance for 34 at 4000 and away we go. At the engine basicly run's in two states hard on or hard off, I don't think we need a recurve, But I would be interested in others opinions on this. As I may have a flaw in my theory. Aggred for road running recuve is the way to go, As there too much to loose down low from bad timing. I'd be interested to know what others are running for total advance . Cheers Andy Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted March 5, 2011 Author Report Share Posted March 5, 2011 nah, you're right Andy, we did the same rallying. No vac, just set the max mechanical advance. ..and the hotter the cam, the lower the vac at idle. All that overlap. Rob just said he got his electronic dizzy re-done before fitting it to carry more inital advance and advance faster at lower revs. That's what I need I think. Quote Link to comment Share on other sites More sharing options...
parrot Posted March 5, 2011 Report Share Posted March 5, 2011 It's highly likely the vacuum advance mechanism would be removed for anything 'non standard' Quote Link to comment Share on other sites More sharing options...
camerondownunder88 Posted March 5, 2011 Report Share Posted March 5, 2011 Hi, Just though id add a quick comment. MANY old points cars I have serviced I note the advance is CRAP in them. Pop the dizzy cap off and the remove the rotor button. Under it should be a fiber or rubber disk. Remove it with a pick and put a drop of oil in there. That lubricates the shaft the moves to actually do the advancing. SO MANY cars I seen no one knows this small step in the service and the shaft will over time seize to the inner shaft and not actually advance at all. so a few drops of oil drive it one car I had took about 2 days but all of a sudden I had to re tune car as shaft started moving and ecconomy improved STACKS and power delivery was smoother. So before we all go ripping into our dizzys just look at this for all you know your dizzy has seized and isnt advancing at all. Cameron Quote Link to comment Share on other sites More sharing options...
snot35 Posted March 21, 2011 Report Share Posted March 21, 2011 Does anyone know what the advance on a 4K electronic dizzy is like? Cheers Mike Quote Link to comment Share on other sites More sharing options...
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