Why use a distributor?

[Alky V6]

I Run A Distributor. No Waste Spark Means Lower Egts.
It Is Not An Igntion Improvement By Any Means It Is
A Step Backwards.the Horsepower Gain Is Acheived
By A More Aggressive Tune-up. This Has Been Proven On The Dyno.
Waste Spark Ignites Un Burned Fuel In The Off Stroke Cylinder
Raising The Cylinder Temperature. The Best System For Sure Is
Cop Accurate Less Mechanical Parts And One Sequential Spark.

If that were true about the waste spark actually igniting whatever unvaporized, non compressed air/fuel mixture there is in the exhausting cylinder, I would be in a heap of trouble with intake backfiring. With my setup, the waste spark is going off while my exhaust and intake valves are open. No backfiring. On top of that, I use nitrous which makes it an even more volatile situation. Again, no intake backfiring. I'm running a comparatively high overlap cam.

My EGTs are not out of line for an alcohol engine.

The waste spark system has not kept me from running whatever ignition timing strategy I choose.

I agree about the COP system. The only drawback that I see to the COP system is the complexity. At least, compared to w/s. More expensive components to fail. Instead of worrying about 3 coils, you're worrying about six. And finding the room to hang 6 coils.

 

[cdsttype]

They May Not Be Out Of Line, But Would They Be Lower With A Dist???
All I Can Tell You Is What I Saw On The Dyno A Drop In Temp
With The Dist With The Same Tune.i Am With You On The Low Tech
Step Backwards With The Dist And Fought The Choice To Go There.
At The Time There Was No Reliable Cop Igniton Available

 

[cdsttype]

By The Way Waste Spark Was Designed To Burn Unburned Fuel In
The Cylinder To Reduce Exhaust Emissions

 

[Alky V6]

If my EGTs were below 1,050F, I might have some trouble keeping the turbo spooled.

If the waste spark is burning anything at the top of the exhaust stroke, that just tells me that the burn at the top of the compression stroke was not efficient or missing is occurring.

For an a/f mixture to light off in the first place, it must be vaporized. Most, if not all of that occurs during the compression stroke. The heat generated by the compression of the mixture does this. If there is a lack of vaporized fuel available, you will not get a light off. The pressure of the mixture during a normal spark event helps to dictate the speed of the flame front. If you did happen to light off some stray vaporized fuel during the top of the exhaust stroke, it would be blown out before you knew it because of the lack of available air and fuel to sustain a burn and the lack of pressure. That's assuming most of the a/f mixture was burned during the power stroke, which if the power of the ignition system is adequate, it should have been.

Now add to that cam overlap. The exhaust valve and intake are open at the same time that the spark plug fires. With my system, and at high rpm, the spark duration is over 50 degrees of crank rotation from the start of the spark. So the spark occurs at 24 degrees BTDC on the exhaust stroke and continues to a point that the exhaust valve is closing or is closed and fresh air, nitrous and fuel is pumping into the cylinder during the top of the intake stroke. You can't tell me the spark is capable of igniting that mixture in the state it's in (mostly unvaporized, no pressure and heat buildup) at the beginning of the intake cycle. I've proved it's impossible.

And, let's say in some alternate universe the waste spark was burning some of that mixture and the piston and cylinder survived the ordeal, it would show up as an increase in BSFC. For what I'm doing with my engine the BSFC is very low on the alcohol scale. 1.14.

 

[dr_frankenstein]

If all you need is a powerful electronic spark control system, and don't need fuel injection control, you should check out E'motive's stand alone XDI ignition system.

I think I am going to go ahead and try the Mag since it seems to be the current trend on most blower V8 cars, Its worth a test I suppose. I will report back any information I learn for everybody to study.

A.j.

 

[HP Man]

Hey Guys, a lot of good info here on this posting. I like the coil on plug set up, my next question would be a dual injector cylinder head like a lot of new performance cars run. (Lexus is using one direct injector plus a second one located in the intake runner) Just a thought. Thanks. Gene

 

[TurboTR]

Don I think you have the basic conclusion nailed already, the "gain" is likely mostly from also going to a CD ignition box. The problem is of course, as you make more power and spin the mill higher naturally (because of higher and higher trap speeds, etc), you just begin to run out of time to fully charge the coils in our inductive system. At only 6000 rpm there's only 10ms to get 3 coils charged and fired per rev. There's only a single EST signal line to carry these charge/fire pulses to the module. Add in the dead band enforced between EST events and you wind up with less than 2.5ms to charge each coil basically, already at just a measly 6000 rpm. As the rpm climbs from there, the amount of time available to charge each coil just gets smaller, and thus the spark output also gets weaker and weaker with increasing rpm.

A CD ignition OTOH requires no "dwell" time to charge the ignition coil. It works by switching some ~ 400-500v onto the coil primary when it's time to fire a spark, which results in an immediate spark basically. Thus since it requires ~ no dwell time, in that regard at least it's inherently far superior to an inductive ignition at high rpm. As long as you can recharge that 400-500v across the capacitor inside the CD box before the next spark event comes along at least.

Like others have said, even though the stock ignition can be run with good success on into the HD power zone there's probably a lot of room for improvement at high rpm with a more suitable racing ignition setup

TurboTR

 

[Alky V6]

Speeder also touched on that idea. The XDI and TEC3r have a unique circuitry built into their ECU to charge the coils and provide a spark that even beats the CD box. No other system can come close to Electromotives ignition power and accuracy. Not even Motec.

 

[lazaris]

"Now add to that cam overlap. The exhaust valve and intake are open at the same time that the spark plug fires. With my system, and at high rpm, the spark duration is over 50 degrees of crank rotation from the start of the spark. So the spark occurs at 24 degrees BTDC on the exhaust stroke and continues to a point that the exhaust valve is closing or is closed and fresh air, nitrous and fuel is pumping into the cylinder during the top of the intake stroke. You can't tell me the spark is capable of igniting that mixture in the state it's in (mostly unvaporized, no pressure and heat buildup) at the beginning of the intake cycle. I've proved it's impossible."

Don,

If what your saying is accurate, how do you explain the lower EGT's Bill has seen on the dyno tests? Very interesting topic.

 

[Alky V6]

It would be foolish for me to even speculate. Now if Bill wants to supply more data about these dyno sessions, I think it would be interesting to dig into this to see if we might figure it out. But seriously, at the top of the exhaust stroke, how much a/f mixture can be left to burn? The initial burn would have had to of been totally lame.

Most TRs are using cams that have zero or very, very little overlap. There isn't even the chance of the awaiting intake charge to be in the cylinder at the time the waste spark goes off. That means it would have to be a/f from the previous charge. The only way I see that charge affecting EGT is if the ignition is missing and a/f is being pumped into the exhaust system. Maybe someone can add their observation of what happens to exhaust temps when it's obvious that ignition missing is taking place.

 

[85HOT-T]

The only way I see that charge affecting EGT is if the ignition is missing and a/f is being pumped into the exhaust system. Maybe someone can add their observation of what happens to exhaust temps when it's obvious that ignition missing is taking place.

I by no means is an engine expert but what I would see happening if the stoke misfired and dumps into the exhaust the heat in the exhaust manifold pipes would ignite that mixture and raise egts, which brings us to the previous post of lower egts. If you ask me what I have logged in my head from this topic is high rpm misfire. That is the concern with the stock DIS. Now what I have to bring to the table is if RJC's dual coil system has two coils, that means it should handle high rpms no prob. Only reason I bring his up is the debate of the stock system. So now the question is will dual coils do it, is the distributor setup oboslete now?

 

[speeder]

OK, I can buy the fact that misfires raise EGTs in a waste spark system. Two of the stock igntion systems in a 6 coil arrangement would still misfire as badly as the stock system, but probably not contribute to the EGT problem. The E-motive provides the benefits of multiple coils and high performance ignition drivers.

A coil dwell of 2.5 Ms from a single coil sounds pretty short for a high revving, high output motor. And this at only 6000 RPM and decreasing with revs. With several EFI systems I have worked with, I have wound up with much bigger dwell times at higher RPMs for best performance. No doubt that the Mega -Joule, flamethrower MSD boxes help with a distributor and single coil, but I think that this is running the ignition system on the edge, where the slightest problem in the secondary circuits can cause big problems. I see multiple coils being a big benefit in setting optimum dwell times.

Being an electrical engineer, I trust (quality) electronics over mechanical things and brute force high voltage systems. To me, more coils don't add unnecessary complication when they can eliminate long ignition wires and caps/rotors. The whole secondary system is under much less stress - everything less critical.

Still, ya can't argue with what works for folks, and obviously the distributors do work. As a long-time lurker here, I'm amazed at the results some guys on this forum get.

I do have to admit to "the more electronics the better syndrome" - that's just how I roll.

 

[cdsttype]

I THOUGHT BUT MAYBE I AM WRONG THESE WERE TURBO CARS
I ALSO THOUGHT WE HAVE BEEN FIGHTING AN AGE OLD PROBLEM
OF BACK PRESSURE IN THE CYLINDER YOU SPEAK LIKE THE EXHAUST
STREAM ON YOUR ENGINE IS ISOLATED

 

[Alky V6]

Something else to think about in the scenario that the waste spark is igniting anything at the top of the exhaust stroke. Let's say the a/f mixture went through the ignition cycle without lighting off. Now the piston drops and uncompresses the mixture.

When this occurs, isn't some of the heat from the previous compression now drawn out from the decompression?

When an a/f mixture is decompressed, does some of the mixture condense into larger droplets from the previous vaporized state, due to the drop in pressure and temperature?

Isn't most of the charge expelled from the cylinder way before the 24 or so degrees before TDC of the exhaust stroke? In fact, most likely past the turbo by this point with a short runner exhaust system?

The piston speed is very slow by 24 degrees BTDC exhaust stroke. In tuned exhaust systems, the charge would have exited the primary tube and a low pressure pulse would have traveled back up the primary and would be pulling residual and the next intake charge into the chamber by this time. Assuming a large overlap camshaft and the unburned charge would be traveling at the same speed through the primary tube as a higher volume and pressure burned charge, which I realize it wouldn't.

I would think that if the charge that was expelled from the cylinder did light off, it lit off way before 24 degrees before TDC ex somewhere in the exhaust system from exhaust system heat.

 

[Alky V6]

I THOUGHT BUT MAYBE I AM WRONG THESE WERE TURBO CARS
I ALSO THOUGHT WE HAVE BEEN FIGHTING AN AGE OLD PROBLEM
OF BACK PRESSURE IN THE CYLINDER YOU SPEAK LIKE THE EXHAUST
STREAM ON YOUR ENGINE IS ISOLATED

Dont' quite understand what you're getting at. How do you feel exhaust bp plays a part in all this?

 

[Alky V6]

I by no means is an engine expert but what I would see happening if the stoke misfired and dumps into the exhaust the heat in the exhaust manifold pipes would ignite that mixture and raise egts, which brings us to the previous post of lower egts. If you ask me what I have logged in my head from this topic is high rpm misfire. That is the concern with the stock DIS. Now what I have to bring to the table is if RJC's dual coil system has two coils, that means it should handle high rpms no prob. Only reason I bring his up is the debate of the stock system. So now the question is will dual coils do it, is the distributor setup oboslete now?

Regardless of what type system it is, it must be capable of putting out the initial voltage level to jump the spark gap in extreme cylinder conditions. You could be using 6 coils per cylinder and if the necessary voltage level isn't there, no spark. The answer is making sure that the system you use has the reserve voltage capacity to do the job you're demanding from it.
The distributor is just a tool used to distribute the voltage to the plug. It's perfectly fine to do this without a distributor.

If I were going to bother with converting to COP, at the very least I would keep the secondary wires as short as possible. The real advantage of COP would be using no secondary wire at all. The coil directly on the plug. In that situation you've vastly eliminated the chance for secondary voltage leaks. Without that worry, you can now pump up the secondary voltage level without worrying about the previous problems I mentioned. If you use COP with long secondary wiring, you've restricted your secondary ignition voltage level to the limit of what the secondary wiring can handle. That would be the same level as most any other high performance ignition system. That would be a waste of time to me.

The secondary wires are the weak spot that limits how much kv level you can get away with in your secondary system. That is what limits me with my particular w/s system. The system is quite capable of putting out some massive kv, but then I just end up blowing it out the wires all over the place. Cross firing then becomes a big problem. That is why I decrease my spark gap with my system. To keep kv levels down to what the secondary wires will allow me to get away with. Also keeps from straining the coils. Longer coil life.

When you start pumping up your secondary kv, a single coil is going to see a lot of heat. More coils allows this heat generation to be shared. So less heat per coil. More coil life.

 

[cdsttype]

I Would Agree With Your Theory On The Valve Timing Events
On A Single Cylinder Engine But With A Manifold Or Collector
And Multiple Cylinder Engine Back Pressure Will Certainly
Play A Role In What Left In The Cylinder At The Extreme
Ratios We Run Compared To An N/a Engine There Is Fuel Left Over
The Fastest Turbo Cars That Are Tuned Well And Live Leave
Leave A Black Trail That Is Fuel

 

[Alky V6]

I Would Agree With Your Theory On The Valve Timing Events
On A Single Cylinder Engine But With A Manifold Or Collector
And Multiple Cylinder Engine Back Pressure Will Certainly
Play A Role In What Left In The Cylinder At The Extreme
Ratios We Run Compared To An N/a Engine There Is Fuel Left Over
The Fastest Turbo Cars That Are Tuned Well And Live Leave
Leave A Black Trail That Is Fuel

Yes it's fuel. But is it at an a/f ratio that can be burned? You need fuel AND oxygen to burn the fuel. Or fuel and a catalytic converter.

 

[cdsttype]

Why Use A Distributor?
That Was Your Question Was It Not.
You Good Some Good Information.

1.more Reliable Rev Control Very Important When Trying To
Win A Race.
2.when In An Actual Buick Class Race Tsm Tso Tsl Tse
Rules Very Tight No Cop Ignition Which Would Be My
First Choice.
3.because Of Tight Buick Class Race Rules Looking For Any
Edge In Horsepower By Lowering Egts And A More Aggressive
Tune. Is There Better Horse Power Gains Elsewhere Yes
But We Cant Take Advantage Of Many Of Them Because Of The Rules.
4.in Super 16 Which Is Run What You Brung I Also Would Not Use
The Dis Because Of The Short Dwell Time And Poor Coil Saturation
At High Rpm
5.in An Open Class Low Rpm Application You Could Run Dis
If Your Okay With So So Rev Control
6. Complication And Price Should Not Be A Factor To The Guys
Who Run The Dist Because Most Guys Who Run One Have Over
50k In There Cars And Are Competitive Buick Class Racers.

 

[lazaris]

"Something else to think about in the scenario that the waste spark is igniting anything at the top of the exhaust stroke. Let's say the a/f mixture went through the ignition cycle without lighting off. Now the piston drops and uncompresses the mixture.

When this occurs, isn't some of the heat from the previous compression now drawn out from the decompression?

When an a/f mixture is decompressed, does some of the mixture condense into larger droplets from the previous vaporized state, due to the drop in pressure and temperature?

Isn't most of the charge expelled from the cylinder way before the 24 or so degrees before TDC of the exhaust stroke? In fact, most likely past the turbo by this point with a short runner exhaust system?"

Don,

What I think you maybe missing in regards to left over exhaust to ignite, is the overlap , especially with bigger duration cams. The new fresh charge being pumped into the chamber during this overlap, some of it goes out with the exhaust. Cant help it. Lobe separation angle also plays a part here. When this happens I can see why it may raise EGT's. There may be enough fresh A/F to burn.