<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Joseph Davis &raquo;</TD></TR><TR><TD CLASS="quote">

No, you have plenty of time, because at really high rpms torque is dropping off and as such the mixture is a LOT easier to light off than at torque peak. Further, you have plenty of time to fully charge the coil - or close enough that it does not matter - at high rpms. Trust me on this - I have fried four coils in the last month and a half playing with dwell settings in order to get a grasp of charge times and how to manipulate them.

Most of it is just fooling around; the majority of ignition problems when using good stock components are resolved by tightening the plug gap. Fiddling charge times has only netted, thus far, improvements in or around torque peak where you have plenty of time to charge the coil... it works exactly like tightening the plug gap in most cases.</TD></TR></TABLE>

I thought thats what CDI ignitions were developed to do, give a more uniform spark more of the time?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
No, that is not how it works. Caps are not like batteries.
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Ok, There not desiged like a battery but they do hold a charge, the CDI box has no charge tiime.
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That can work if you make a point of just charging the coil, but if the ECU ever sees the higher voltage it'll just shorten dwell time so that the coil only takes on the OE-specified charge. If you get any significant gains from doing this you either have something wrong with your ignition system or, I repeat, you needed to tighten up your plug gap.

Paying close attention to AFRs is also important. Some setups simply will not fire if you try to run them too rich past a certain power level. The car needs to be correctly tuned before you can really pinpoint the ignition as being a weak spot.


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I never tried this but was reading a book by Mr Jacobs and he went into adding inline batterys to your coil input for short periods of time. The book was copywritten in the late 70's though. Also mentioned in the book was that CDI ignitions out perform inductive ignitions pretty much always but then again he sold CDI's so ...

Your opinion and knowlage always appriciated with my posts.
Tony1 thats sweet info too cuz I have a spare merc coil , might just hook it up.

 

Be carefull what you hook up a Mercury coil to, since it's almost a dead short to ground, it'll kill most MSD boxes. I think the 7 series will fire it, but i don't think the 6 series will work with it. Definitely don't hook it up to a stock ign. system. Or if you do, get it on video... lol

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">There is no charge time on the coils.</TD></TR></TABLE>

Sure there is, it's an inductor that stores up current in the form of a magnetic field.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">Also, there's some good CDI discussions on the EFI101.com forums.</TD></TR></TABLE>

Gotcha, will check into it.


Thanks, everyone.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Joseph Davis &raquo;</TD></TR><TR><TD CLASS="quote">

Sure there is, it's an inductor that stores up current in the form of a magnetic field.
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Even if the CDI box is sending the high current signal to the coil, not a typical 12v signal?

 

Well, for what I am talking about where I manipulate charge time via the ECU with a conventional coil setup:



Tau is the time constant dictated by the inductance L and resistance R of the circuit, so that Tau = L/R and 5 Tau is charge (or discharge, flip the curve above) time.

With the amount of time a Honduh engine takes to complete one cycle - or more to the point of a single coil 4 cylinder: one-quarter of a cycle - charge, discharge, and potentially most important cool off time is critical.

That is the hat I am wearing while having this discussion.


Now, for a CDI ignition? I seriously dunno. I am more than happy to take a poke at Google and the EFI101 threads and then take a stab at the subject.

 

Ok so you made me read more and I found out that . 1) a capacitive discharge ignition still has a charge time and the sensor opens the circuit to the capacitor so as the capacitor dumps its charge making the coil go off. The CDI ignition has higher spark energy but a shorter duration. 2) I think I got this right, A CDI ignition can have trouble igniting leaner afrs because the field from the high energy spark can push the fuel out of the way and fail to ignite the af mix. I was wondering why I had to run a richer af @ idle.

 

What injectors are you running?

 

dsm 450s

 

I've found that injectors with shitty spray patterns don't atomize well and need to be run at a richer a/f ratio at idle, otherwise they'll misfire. RC injectors are some of the best i've used in that aspect. Every their big 1000cc injectors will usually allow a 14.5:1 a/f ratio at idle w/o misfiring.

 

DSM 450 have good spray patterns, they shouldn't do that. You need to verify their spray pattern, IMO, and make sure yours still function correctly - they are nearly 20 year old pieces with a lifetime of use on them.

How are you logging AFRs? Through the ECU and some datalogging package, or via a heads up display? It sounds like you might have a ground issue skewing the accuracy of your readings.

I've also seen not enough ignition timing, or more to the point wierd distributor positions affecting injector firing angle, cause popping at idle.

 

What about spark plug gap? I've found that for whatever reason the further I close my spark plug gap the richer I have to run idle in order for it not to pop.

By the way, this thread kicks ***, lots of good info.

 

Thanks for the ideas everyone! I'm gonna check all that stuff out I idle good @ 13.8-14.0 af but 14.5-15 and get some poping. I run Crome pro and a plx 300.

 

this is my story, i had my car dyno tuned yesterday. my stock ignition keep misfiring at 4800rpm right at the vtec crossover point, so we put on the MSD DIGI 6 PLUS with a SS BLASTER COIL, changed to new plugs and leads........... even worse, mis fired all the time thro the whole rpm range. this is a built h22 full race turbo kit on AEM EMS
any thoughts?

 

and my autometer tacho was going made, all over the place!

 

Your problem is probably either a trigger problem that's very common with aem and the oem dist (my cam trigger kit will fix that), or a tuning problem.

By your description though, misfiring at 4800 right as crossover, i'm going to go with a tuning problem.

 

Sounds like the car is having to make a large timing jump on crossover if it's missfiring there.

 

i never tuned the car, but what do you mean? is there something i can check? is there anyway i can get the msd to work? its all brand new, i would want to waste it, looks like an awesome bit of gear! its a major mis to, but the rest of the rpm range is great! right after it misses, at 5200rpm to 5750 it goes up 200hp im only running 1 bar boost on a SC61 i was planning on running 22psi, but the tuner didnt want to push it with an ignition problem. any thoughts?

 

its always made me laugh to hear people say high energy spark. whats high energy about it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hyabusa hunter &raquo;</TD></TR><TR><TD CLASS="quote"> im only running 1 bar boost on a SC61 i was planning on running 22psi, but the tuner didnt want to push it with an ignition problem. any thoughts? </TD></TR></TABLE>

I defer to tony1 on the MSD issues, and I told you in PM exactly what tony1 said about your "ignition" problem at 4800 with stock coil - only I went into greater detail.

You've been told everything you need to know twice now, is there anything else you need?

 

I know, I know the coils only gonna work as hard as it has to to jump the plug gap.
Are you saying that when a cdi ignition and a inductive ignition fire a coil your getting the same spark energy and duration of spark time? I'm gussing the currant is greater with a cdi ignition not the pressure to jump the gap and since the flow is greater the duration shorter.

I fixed my idle by shortining my plug gap and can run closed loop now! No miss fires.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Joseph Davis &raquo;</TD></TR><TR><TD CLASS="quote">
No, that is not how it works. Caps are not like batteries.</TD></TR></TABLE>

I kind of get what the guy was saying, in a sense, capacitors are like batteries, neither creates energy, and both are used for storing energy.

 

If you really think a cap is anything like a battery then you lack a fundimental understanding of electricity. They are governed, in part, by math similar to that of inductors, and unlike a source they block current and voltage in a DC circuit.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quik sol &raquo;</TD></TR><TR><TD CLASS="quote">

I kind of get what the guy was saying, in a sense, capacitors are like batteries, neither creates energy, and both are used for storing energy.</TD></TR></TABLE>


I was using lame mans terms, obviously too lame for this forum! No problem.
Better not to give someone the wrong idea and I don't mind being corrected. Just makes me go and read more so I understand more.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Joseph Davis &raquo;</TD></TR><TR><TD CLASS="quote">If you really think a cap is anything like a battery then you lack a fundimental understanding of electricity. They are governed, in part, by math similar to that of inductors, and unlike a source they block current and voltage in a DC circuit.</TD></TR></TABLE>

ok...did you get my broad statement?....Don't tell me what I understand and don't understand. Answer two questions, yes or no only...

Do they store energy? Do they create their own electricity?

YES and NO....tada...I was just stating they had the same characteristics.

 

I suggest you pick up a book on basic electronics and start there.