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Location:
sunny coast, qld
Registered:
October 2002
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mulit coil vs distributor setup
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Sat, 30 July 2005 00:52
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Hi guys,
was just having a chat with my mechanic before and he was talking about this debate. Why is it that a multicoil setup is better?
All the coils have to do is send the charge to the spark plug and make it spark in a given amount of time (depending on revs) and be able to produce a strong enough spark. So why are small standard coils better than a distributor setup?
To increase the spark voltage on a multi coil setup you need a CDI unit which is about $900 or so and you can do the same thing with an MSD until for $250. I have seen this MSD unit make an extra 17rwkw in the top end of a sr20de silvia.
He said he fitted a cressida dizzy to a 7mgte supra and that fixed its breaking up at high revs problem.
What are your thoughts?
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Location:
Brisbane
Registered:
May 2002
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Re: mulit coil vs distributor setup
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Sat, 30 July 2005 05:48
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If you have a distributor you have only one coil, which becomes a limitation at higher revs because you have much less time between each spark for the coil to build up its charge.
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Location:
Brisbane
Registered:
June 2003
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Re: mulit coil vs distributor setup
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Sat, 30 July 2005 05:50
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why not put an msd on there to increase your spark?
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Location:
sunny coast, qld
Registered:
October 2002
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Re: mulit coil vs distributor setup
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Sat, 30 July 2005 07:23
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| Norbie wrote on Sat, 30 July 2005 15:48 |
If you have a distributor you have only one coil, which becomes a limitation at higher revs because you have much less time between each spark for the coil to build up its charge.
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If these calcs are correct at 6000rpm one cylce takes 6ms. Because it is a 4 stroke it is 2 revs per cycle so a total of 12ms. I thought the time to make it spark was only 1.5ms or so. So you are going to have to be really high up in the rev range for the spark to become too slow.
They still use distributors on top fuellers etc. so they must be able to handle big revs when setup right.
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Location:
Brisbane
Registered:
February 2003
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Re: mulit coil vs distributor setup
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Sat, 30 July 2005 07:26
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MSD is still has this handicap...| Quote: |
have much less time between each spark for the coil to build up its charge.
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...to overcome.
the ultimate solution would be after market coil packs (either CoP or waste-spark) - driven by an aftermarket computer with built-in igniters and dwell control.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: mulit coil vs distributor setup
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Sat, 30 July 2005 07:55
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There is no 'best' igniton setup.
Points: forget under any circumstance, even lawnmowers give trouble with them.
Single coil HEI: (dizzy) used on many cars, and adequate for most jobs
Single coil CDI: Often used when HEI is no longer able to keep up due to RPM, or boost/nitrous/etc. 'blowing out the spark' - has the disadvantages of short duration spark (not great for emissions/light load, lower RPM), and high voltages making plug leads, dizzy caps etc. susceptable to leaking/cross firing
Waste spark: used by people who can't afford an ECU with the full number of ignition channels
Multi coil HEI: With adequate coils, and maybe a voltage booster, will keep up with almost anything people can dream up, provided the hardware is good. Some OE coils can tend to be a bit weak for those looking for triple the power, so people sometimes say these systems 'must be crap'
Multi coil CDI: Useful for the 35+psi, 9000+rpm lovers, but with the disadvantage of short spark duration still.
Top fuel ignition systems are done a different way altogether. One reason for this is redundancy - from what I understand, with the physical volume of liquid that runs through these engines (due to use of nitromethane), if the ignition actaully fails to fire once, they will hydraulic lock, in a relatively spectacular fashion 
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Banned by his request
Location:
moved to tamworth
Registered:
July 2002
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Re: mulit coil vs distributor setup
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Sat, 30 July 2005 08:20
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go the Magneto's.
mick
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Location:
sunny coast, qld
Registered:
October 2002
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 01:43
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Thanks for that MrShin. Makes some sense.
Just one thing, what about a waste spark setup with a CDI? I assume this sits somewhere in between waste spark and multi coil CDI. Good enough for most systems?
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Location:
perth wa
Registered:
June 2005
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 04:00
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some bloke on tv rekoned top fuelers actually "diesel" at the end of the track - ie. the combustion chambers are so hot the fuel mix ignites itself
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Location:
sydney,nsw.oz.
Registered:
July 2002
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 06:42
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| Chris Davey wrote on Sat, 30 July 2005 10:52 |
Why is it that a multicoil setup is better?
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As Norbie said " More time for Flux to rise = bigger voltage"
| Chris Davey wrote on Sat, 30 July 2005 10:52 |
So why are small standard coils better than a distributor setup?
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Less voltage loss,more accurate than a dizzy and cheaper to make 4 coils and some wires than 1 distributor.
| Chris Davey wrote on Sat, 30 July 2005 10:52 |
He said he fitted a cressida dizzy to a 7mgte supra and that fixed its breaking up at high revs problem.
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There wouldn't be much difference in the 2.
Must've been something wrong with the dizzy in the 1st place
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Location:
sunny coast, qld
Registered:
October 2002
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 07:00
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Putting the dizzy on fixed the problem so must have been something wrong with the coil packs then.
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I supported Toymods
Location:
Australia
Registered:
November 2003
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 07:13
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If the CAS isn't connected properly, it will breakdown at higher revs.
This is nothing to do with Coilpack vs Dizzy, but dodgy wiring, or a bad sensor.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 07:41
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And the best bit being that the sensor in the GE and GTE are actually quite similiar...
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Location:
Brisbane
Registered:
February 2003
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 08:27
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| Chris Davey wrote on Mon, 01 August 2005 11:43 |
Just one thing, what about a waste spark setup with a CDI? I assume this sits somewhere in between waste spark and multi coil CDI. Good enough for most systems?
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it strikes a healthy comprimise between spark power (CDI gives strong spark and some systems will control spark duration and decent multiple-spark-events depending on rpm or load or ... etc) and waste-spark needs fewer ignition events to monitor (and hence syncronise with) and has simpler wiring & software to drive the less-complex hardware.
two other advantages of waste-spark systems are: cleaning of spark plug gap (arcing during post-combustion period reduced crap build-up in gap area) and assisted burning of post-combustion gases (e.g. left-over material is ignited or assisted in completion of burning) - this helps reduce overall emissions output from the engine, particularly when under load.
The design of some waste-spark systems also give you slightly better reliability and fail-over. The holden triple-coil-pack seen on most V6's and the US/euro EDIS systems have their own crank-pickup and can continue to run (in a limp-home mode) if the ECU stops telling it how much advance to include in any spark timing. Same applies for some of the early VAST toyota systems.
weird but true: if you have a relative/aquaintance/family member who has a pacemaker and is also universally disliked (e.g. a wanker) ... give them a good zap with a CDI ignition system - the voltages they pump out would give some digital heart-helpers a nasty whack and if you're lucky, turn them off 
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Registered:
March 2005
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 08:55
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people have looked past one of the most simple differences. THere are no moving parts to break in a coil pack setup as with a dizzy.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Location:
Brisbane
Registered:
February 2003
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 12:05
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| Sam_Q wrote on Mon, 01 August 2005 20:08 |
how is this MSN unit fitted? and whats it do exactly? just setup a multiple spark discharge?
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You mean MSD?
in its simplest form, you replace points with an optical/hall effect sensor, MSD box takes signal from sensor and drives a big coil which gives you a fat spark. Electronic ignition in a fancy box and inflated price tag
-older MSD boxes are not much more than an over-engineered ignitors/CDIs
-some do multiple spark discharge up to X rpm
-newer boxes can do all manner of smart stuff (waste-spark, CoP, boost retard, etc) depending on model, cost and input sensors
-popular with the hi-po engines that use dizzi's
-can be used with non-factory ECUs to drive big coils & coil-packs for big spark
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 14:22
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thechuckster: yeah msd, either a dumb typo or I was distracted.
so heres another one for you guys:
- how much of a difference would there be going from a dizzy to 4 independant coils on something like a 20V engine?
- how about going to multi coils to the same setup with CDI?
it looks like I am going to run with my 20V and Wolf 3.1 these; 2 twin channel M&W ignitors combined with 4 hyundai coils and extra short spark plug leads. I have other reasons but for power alone would I gain much if I went from one to the other?
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Location:
Montrose, VIC
Registered:
May 2002
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 14:39
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OK, well you're not going to gain big power by changing the ignition around on the 4AG, but you will gain by not having the dizzy cap in your way NA 4 potters generally don't have enormous ignition troubles, even with dizzystribulutors, simply because being NA they never realise the cylinder pressures of something turbo'd (yes, I realise nitrous will change all that....), and also because there are still only half as many spark events as an 8 cylinder engine. Usually if there's ignition breakdown there, it's because there's something weak about the ignition system in the first place. (i.e. crap coil)
I wouldn't bother with CDI, especially if you're using 4 coils.
By ditching the dizzy though, you not only gain from being able to make it fit under the bonnet, have less ignition noise, less places to leak, etc. Do what you've said you will and be happy.
Oh yeah, I detest dizzystribulutors, by the way! Does anyone remember back to the days when someone would have a Ford V8 with a blower on it, and have a dizzy belt driven off the front of the engine? The things people did before the IC and the transistor were invented!
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 14:44
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yeah I thought that would be right.
It sure will be easy to maintain with 4 of the same length leads and only the sparkplugs as the other disopsable item. Is there any advantage of an aftermarket M&W ignitor over an OEM one?
I think the worst setup would have to be the classic mini, just imagine any water through the front and bye bye ignition! I heard a chopped up rubber clove was a perfect fix over the dizzy cap.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 14:46
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| mrshin wrote on Tue, 02 August 2005 00:39 |
Oh yeah, I detest dizzystribulutors, by the way! Does anyone remember back to the days when someone would have a Ford V8 with a blower on it, and have a dizzy belt driven off the front of the engine? The things people did before the IC and the transistor were invented!
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LOL
VST... variable spark timing 
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Location:
Montrose, VIC
Registered:
May 2002
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Re: mulit coil vs distributor setup
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Mon, 01 August 2005 14:48
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Personally I wouldn't use the M+W ignitors if you have to pay too much for them... What have you got lying around?
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Location:
Montrose, VIC
Registered:
May 2002
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