Distributorless Ignition Systems Questions

[4OfaKind]

I have been studying DIS for my project and I have noticed the use of crank-triggers along with cam-sync plugs. What is the difference between the two? Is the cam-sync necessary? Is there an engine management system that can run coil on plug with just the crank-trigger and not use the cam-sync plug?

I want to run DIS on a TT SBC V8. I was going to use just a crank-trigger wheel. But now it seems I will need the cam-sync plug as well. Is this true?

Thanks,

Mal

[Larry Callahan]

I am running an Electromotive unit on my TT SBC V8 and I think it will work really well. I ran it for a short period without turbos and I like how it works and it only uses a crank trigger.

Check them out at http://www.electromotive-inc.com/

[4OfaKind]

Thanks Larry,

Electromotive was one of the units I was thinking of getting. I got nervous though when I saw Hot Rod's article on "F-Bomb's" motor by Nelson Racing Engines. It said Nelson uses a crank-trigger and an MSD cam-sync plug. Nelson said he liked the E-Motive unit because of the highly reliable timing signal; no danger of bending a rod due to a miss. Well I can't afford bent rods either.

What does a cam-sync plug do? How often do engine management systems misfire? I am probably worried over nothing but I am curious now so I gotta know.

I was also looking at the Accel-DFI Thruster EFI Engine Management System and MSD's Delphi MEFI 4 system.

Mal

[BB69]

A cam sync signal is used if you want sequential ignition. Systems that only use a crank signal are wasted spark. The coil fires each cylinder every revolution. Without the cam signal, the computer doesn't know if the cylinder is on the ignition stroke or the exhaust stroke, it only knows it's at TDC.

The chances of the computer "misfiring" is about zero. However, if the computer doesn't receive the correct signal you can run into problems. This can be an issue if your crank trigger wheel flexes, or the sensor mount flexes, or you get debris between the sensor and wheel, etc. If could also be a problem in the wiring. Some of the OEM crank sensors use shielded wire. If the shielded wire isn't used in an aftermarket installation, that could cause some interference. My guess is that problems with misfire are installation or hardware issues, not problems with the actual ECU.

Ken

[GetMore]

If you have one coil per cylinder you need a cam sync signal, so it knows if the engine is supposed to fire cylinder 1 or cylinder 6, for instance. (If you run a full-sequential EFI system you need the signal for the same reason, but for the injectors.)
If you use a "wasted spark" setup, where one coil is used for two cylinders then all you need is the crank trigger. (With EFI if you run a semi-sequential system it works the same.)

[4OfaKind]

Thanks guys,

That clears things up a bit. I was planning a full sequential coil-on-plug setup but with only a crank-trigger. I guess that would not have worked to well. So I would need the sync signal.

So I guess the question is: Is there a significant advantage to sequential coil-on-plug vs. wasted spark? (Other than the obvious timing)

Mal

[GetMore]

I know it adds even more dwell time to charge the coils, but I don't know if that's an issue with the wasted spark design, I believe they have enought time up until about 12,000 rpm.

If you have a plug or wire that shorts out, then you will have two misfiring cylinders with the wasted spark design.

Mounting the coils and running the spark plug wires will not be as pretty with the wasted spark setup.

I don't know if there are any real advantages to coil on plug, though I imagine there must be, since all the mfgs. are going that way now.

Unlike what you might think from looking at the system, the wasted spark setup does not fire both spark plugs at the same time. To fire the plug it must first ionize the gap of the plug. It is easier to ionize the gap in the cylinder with the compressed air/fuel mixture, so only the plug that needs to fire is fired. Convenient, isn't it?

[Ollie8974]

Thanks guys,

That clears things up a bit. I was planning a full sequential coil-on-plug setup but with only a crank-trigger. I guess that would not have worked to well. So I would need the sync signal.

So I guess the question is: Is there a significant advantage to sequential coil-on-plug vs. wasted spark? (Other than the obvious timing)

Mal

I dont know of the advantages of one ignition system over the other except the Ford EDIS is the easiest to adapt. All you need is the Ford EDIS ignition module, coil pack, a 36-1 wheel and sensor.
Summit Racing lists cam sync distributors for chevy and Ford, use key word Hole plug or dual sync.

[4OfaKind]

I dont know of the advantages of one ignition system over the other except the Ford EDIS is the easiest to adapt. All you need is the Ford EDIS ignition module, coil pack, a 36-1 wheel and sensor.
Summit Racing lists cam sync distributors for chevy and Ford, use key word Hole plug or dual sync.

Ollie,

How does the Ford EDIS connect? (Excuse my ignorance.) Using the Electromotive unit as an example, would the EDIS provide an alternate source for the cam sync? So I would just need a trigger wheel and eliminate the distributor?
Eliminating the distributor is so important because I plan to set the engine back behind the front axle; putting the distributor hole deep into the firewall.

Mal

[Ollie8974]

Ollie,

How does the Ford EDIS connect? (Excuse my ignorance.) Using the Electromotive unit as an example, would the EDIS provide an alternate source for the cam sync? So I would just need a trigger wheel and eliminate the distributor?
Eliminating the distributor is so important because I plan to set the engine back behind the front axle; putting the distributor hole deep into the firewall.

Mal

I am using a Megisquirt ECM, (I would imagine the Electromotive ECM is the same) in that the ECM sends a 12v signal to the ignition module to fire the plugs. EDIS does not requier a cam sync. Which plug fires is determined by the signal from the 36-1 sensor wheel.

This is the Megisquirt web site. There is a ton of info and support,
scroll down about half way on the left hand side to the Megasquirt Support Forums.

http://www.megamanual.com/index.html

[GetMore]

I know there is a product out there, I think it's made by MSD, that is an oil pump drive and cam sync sensor. It is very low profile, so it should work well for you if you won't have room for a distributor. It'll also kill two birds with one stone, so to speak, since it will eliminate the need for fabricating an oil pump drive to fit under the firewall.


Edit: Here's a link: http://store.summitracing.com/partde...4&autoview=sku

[amx2334]

If you have a plug or wire that shorts out, then you will have two misfiring cylinders with the wasted spark design.

If you have an open circuit you will lose 2 cyl. If you have a short to ground you will lose one cyl.

Unlike what you might think from looking at the system, the wasted spark setup does not fire both spark plugs at the same time. To fire the plug it must first ionize the gap of the plug. It is easier to ionize the gap in the cylinder with the compressed air/fuel mixture, so only the plug that needs to fire is fired. Convenient, isn't it?

The wasted spark fires both plugs. The firing kv on the compressed cyl. is higher.It takes more voltage to fire the plug with more cyl. pressure (also lean mixture). If you examine the paired cylinder plugs you can see that one is firing opposite polarity from the other.A good scope will show both firing lines(along with the spark line or Ionization line)Saturn actually used the higher kv to "find" the #1tdc eliminating the need for the cam signal.If using the waste spark method you don't need to know #1 tdc because you fire the 1&6 cyl. simultaneously.it just needs to know where TDC is.You will need the #1 tdc if running sequential fuel and or spark(cop).

On the ford edis how do you plan to control the timing?It is my understanding that you need a SAW (spark angle word) pattern.Otherwise it just runs 10deg adv. all the time.the edis is a pretty complex item compared to the gm.

you will need something to drive the oil pump and fill the hole in the block so it might as well be a synch plug. AEM make them also.

[BB69]

There are two wires that connect between the EDIS module and the Megasquirt system. One wire carries the position signal from the EDIS module to MS, and the other is the SAW from the MS to the EDIS that tells the EDIS when to fire the coils. The system may be complex, but adapting it to a car is easy.

The MSD distributor plug can be had with or without a cam sync signal (at least for a Chevy). I bought the one with the signal in case I want to go sequential in the future. It still sticks out of the manifold a few inches, but the small diameter would allow you to move the engine back.

One of the big advantages of the COP is the ability to put the coils close to the cylinder. With a system like the EDIS, you do get rid of the distributor, but you still need to mount two of the coil packs somewhere and run wires back and forth across the engine. It would be a lot cleaner to mount individual coils on or near the valve covers and have short wires to the plugs.

Ken

[4OfaKind]

I looked at the Ford EDIS system over the weekend and it is basicly a batch fire system. It and the electromotive unit are practically the same thing.

you will need something to drive the oil pump and fill the hole in the block so it might as well be a synch plug. AEM make them also.

It appears it is not possible to run Sequential w/o a cam sync signal. Even the GM LSx ECU gets a cam sync signal from somewhere. And I had completely over-looked the oil pump I was so focused on the distributor itself. I will probably buy a MSD plug w/ the cam sync signal and run sequential that way. Thanks for all the help,

Mal

[twov8sandat4]

Hi everyone,

Does anyone have a good understanding of MSD's DIS-4 ignition system? Can you wire four MSD Blaster II coils to be triggered by the DIS-4? This is going into a 95 Mitsubishi Eclipse AWD drag car. It is experiencing terrible misfires at high rpm (7500+,) and so far we have come out empty in finding a solution. It currently has a Coil on Plug setup with MSD DIS-4 ignition. We have the plugs closed down all the way to 0.022" and it still misfires. Boost is set to 34 psi. We swapped the Coil on Plug setup to the stock Coilpack and NGK wires, no change. We change plugs every round to eliminate them from the equation.

Will those Blaster coils even work on a high rpm setup? I am guessing we can't put out enough spark energy to overcome the high boost in the combustion chamber, and figured if we setup a strong spark source, we might resolve the problem.

Any other alternatives you guys can think of?

Any ideas, jokes, flaming welcome I know the car is not a Pro-Tourer, but figured you guys can come up with some ideas.

The car is running in the high 10s at 130+mph breaking up, and it is driving us nuts

Thanks

[GetMore]

Are you sure your valvetrain is working properly? I'm wondering if maybe you've got some valve float.

[twov8sandat4]

Are you sure your valvetrain is working properly? I'm wondering if maybe you've got some valve float.

It is not the valvetrain. The head is built to handle 10000 rpm. This actually happened to another car also with a similar setup, so that is why we are suspecting it is the ignition.

[EFI69Cam]

I have bench tested the following combo for my 540 BBC
Accel Gen 7 ECM
Accel dual sync hall effect dist
FAST eDist
GM LS1 coils

I hooked up the ECM EDist dist and coils, powered up the system and got spark out of each coil. I will not know for sure this system will run an engine until I put fuel in my 540.