Why use a distributor?

Don, if you look back in the Stage II forum archives this has been discussed several times. First, using the distributor makes it easy to get a two-step function compared to the stock ignition module which won't resync reliably after a cylinder is dropped. Second, having a second "waste" gap in the distributor cap is not all that different from a second spark plug so I don't think the voltage requirement is very different (I don't know what the rotor to cap spacing is and what that firing voltage is at underhood temperature and atmospheric pressure compared to a spark plug gap in the hot exhaust gas 20-40 psig environment in the chamber when the waste spark fires but having done some spark discharge experiments at different pressures and gaps in the lab my gut says not more than maybe 3-5 kV different tops). Third, there is a lot of belief and some evidence that getting rid of the waste spark event makes more power. Several guys have reported gains of 40-80 hp on 1000+ hp engines on the dyno when going from a stock setup to the distributor. Some of that is probably getting a hotter spark but maybe not all. Jason Cramer has a dual module dual coilpack setup on his tsm car that allows him to emulate a waste spark setup by firing both spark plugs, using separate coils for each plug, or to just fire one plug with one coil, so the plug that is firing a cylinder always gets full power from its own coil, and he has reported a noticieable gain without the waste spark. Fuzzy memory says maybe 10-30 hp on a 750+hp motor (9.90 at 3500 lbs is 710 rwhp on average). There are some theories in the archives here but I don't know if anyone has scientifically proven a reason for this. Lastly, in the stock ecm for sure all the cam sync signal does is identify which cylinder to fire next but all the timing is done from the crank sensor, and obviously in the old bank-to-bank classic FAST boxes this is true since they didn't use a cam sensor.

[Okay, see above post for the difference Jason saw :). And he only used one module but two coilpacks. Darn slow typing :). Oh, another option is the COP setup a couple of vendors are developing.]
 
I see a lot of comparisons being made to the 'stock' waste spark system. Are there any comparisons to any of the other available waste spark systems?

Could it be possible that there are a lot of different systems, regardless of the style that would be better than the 'stock' waste spark system?

ijames. Is the 3 to 5 kv difference in favor or against the distributor system? Higher kv with the distributor system? Pressures and gaps being equal? Were any long term tests done to see if there was any change due to rotor and cap terminal degradation?
 
all i can say is bless you guys. you guys are doing allot of research, have theories and ideas. i just know its getting cool listing to it . im enjoying this thread allot. its just fun to see how passionate we all can get about what we do. i love it.
 
A few questions. If the ignition secondary system was capable of doing so, wouldn't an increase in spark plug gap and/or the addition of a rotor to terminal gap, such as adding a distributor, cause an increase in the secondary kv level? With this increase in the secondary circuit load, would the spark at the plug be more powerful? At least initially? Maybe even just slightly because of the added resistance caused by the gap in the distributor? I realize that the voltage requirement to jump the gap is much less in the atmosphere of a distributor cap, but there still is an increase in kv resulting in a more powerful spark from that alone. Correct?

Then you could match that increased kv level with a waste spark system by just increasing the spark plug gap? Assuming that the basic system is capable of supplying the increased kv level?

Maybe comparing a distributor system to a waste spark system with identical spark plug gaps is not a fair comparison?
 
turbodragster said:
all i can say is bless you guys. you guys are doing allot of research, have theories and ideas. i just know its getting cool listing to it . im enjoying this thread allot. its just fun to see how passionate we all can get about what we do. i love it.
Click to expand...

The more this stuff gets bounced around, the more we all understand. I agree.
 
DonWG said:
ijames. Is the 3 to 5 kv difference in favor or against the distributor system? Higher kv with the distributor system? Pressures and gaps being equal? Were any long term tests done to see if there was any change due to rotor and cap terminal degradation?
Click to expand...
Don't know for sure which would be higher, but I'm guessing the difference is only a few kV and probably not enough to matter. What is the gap between rotor and cap? How sharp are those edges? Compared to the rotor-cap gap, the higher pressure in the cylinder would raise the voltage but the high temperature and any residual ionization would lower the voltage, so again, it's probably a wash. Don't know of any long term testing.

Having a second gap besides the plug gap will raise the total secondary voltage at the coil terminal but shouldn't raise the voltage available at the plug gap - the voltage will divide between the two gaps.
 
ijames said:
Don't know for sure which would be higher, but I'm guessing the difference is only a few kV and probably not enough to matter. What is the gap between rotor and cap? How sharp are those edges? Compared to the rotor-cap gap, the higher pressure in the cylinder would raise the voltage but the high temperature and any residual ionization would lower the voltage, so again, it's probably a wash. Don't know of any long term testing.

Having a second gap besides the plug gap will raise the total secondary voltage at the coil terminal but shouldn't raise the voltage available at the plug gap - the voltage will divide between the two gaps.
Click to expand...

So the gap in the distributor would demand a higher voltage output from the coil without any voltage increase after the distributor and at the spark plug gap?
 
FWIW, a new cap is $40, a new rotor under $10. I figure if you can afford to need a distributor, u can afford to change these parts somewhat regularly. :D
 
I'd gladly pay the expense, if I was sure there wasn't a better alternative.
 
The sum of the voltage drops across the individual loads of a series circuit is equal to the total voltage applied to the circuit. If any one of the resistances is changed in the circuit, all the voltage drops will change. The individual drops will still add up to the source voltage.

So what does this mean to us in reference to the secondary circuit of our ignition system?
 
In a series circuit, the same amount of current will be present in all parts and points of the circuit at the very same time.
 
Thanks Jeff. It's not that I'm looking for something different than what I have, I'm just trying to understand what the short comings are of a waste spark system. I'm burning pure alcohol. Certainly not the easiest type of mixture to fire. I've run it at ratios approaching 4 to 1. Even harder to fire. So far I've been to 32 psi boost, and with a high overlap cam by most peoples standards for a turbo engine. I'm running a waste spark system that has been flawless on top of it all. I'm just looking for a reasonable explanation why everyone is so against waste spark.
 
Don, when I bought my MSD 7A from Dusty, he spoke of more HP and he also made a comment about reduced bearing wear without the waste spark. It was never really explained to me why the waste spark would effect the rod bearings.
Jeff
 
Waste spark has been with us for over 20 years. It's used on the vast majority of domestic vehicles in the U.S. I find it very hard to swallow that waste spark has anything to do with bearing wear.
 
On a scope, the typical waste spark system fire line and spark line of a cylinder on the compression stroke are not unlike any other ignition pattern except for maybe less coil oscillation. And since a spark is a spark is a spark, where's the extra hp coming from? If a waste spark system can be had that can put out the equivalent spark intensity and dwell time of another type of system, then I can't see any difference.
 
Don,

I too have wondered about this use of distributors among the Buick guys.

I know you use the TEC3... and there can be no argument that a 60-tooth crank trigger will give more accurate timing than a 3-magnet one.

The E-motive TEC3 has ignition circuits built - in that hits the coils on the DFU (Which contains 3 standard GM DIS Coils) with energy comparable to CD systems such as MSD. That's the difference. This is probably more than enough to make up for any energy lost by firing two coils at once.

On my Stage II (yes, I will shock the world when my project finally gets off the ground) I will be using the TEC3r to fire 6 coils in a non - waste spark configuration - but only because it's an odd - fire motor:eek: , using the GN cam sensor for a reference signal. I'm not very concerned about the accuracy of the cam sensor since the cam reference has a very wide tolerance. You could do 6 coils too with the TEC3 if there is a desire for even more energy to the plugs.
 
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