Ignition Mods & MPG

[2000StreetRod]

According to what I've read on this forum, the general consensus seems to be that the stock V6 SOHC ignition module is adequate for the stock engine (block/heads/cam) performance. However, numerous Explorer owners have performed ignition mods. Has anyone noticed a related improvement in fuel economy?

I'm considering adding a double-fire ignition capability. They've been used for years on very large engines but not commonly on passenger cars.

 

[IZwack]

How does this improve MPG? The spark on the exhaust stroke is a "wasted" spark/energy. As I understand it, the "dual" spark is used on more primitive ignition design to simplify the system. But on modern vehicles, each cylinder is controlled independently to its optimize the overall efficiency of the vehicle. I guess "dual" spark is kind of like batch injection (and to some degree, bank injection) versus sequential injection.

 

[2000StreetRod]

How does this improve MPG? The spark on the exhaust stroke is a "wasted" spark/energy. As I understand it, the "dual" spark is used on more primitive ignition design to simplify the system. But on modern vehicles, each cylinder is controlled independently to its optimize the overall efficiency of the vehicle. I guess "dual" spark is kind of like batch injection (and to some degree, bank injection) versus sequential injection.

I guess that I should have been more clear. I'm not talking about the "dumb" ignition system used on stock Fords and many other brands that fires a wasted spark in a paired exhaust cylinder. I'm talking about an ignition system that fires a plug under compression two or more times. MSD manufactures a capacitive discharge system that fires a plug for 20 degrees of crankshaft rotation during lower rpms. It is claimed to improve idle and possibly gas mileage. At high rpms, there is not enough time for the MSD system to charge and fire the capacitor more than once per cylinder.

 

[2000StreetRod]

Greater mpg due to ignition mod?

Do any of you think you're getting better gas mileage because of ignition modifications? I'm considering attempting to build a modified ignition system that fires each plug twice even at red line.

 

[2000StreetRod]

Still looking for feedback

I'm still looking for some responses from anyone who thinks that their fuel economy improved because of modifications or replacement of the stock ignition system on a SOHC. Most of the threads I've found claim a smoother idle but no significant fuel economy improvements.

 

[2000StreetRod]

Used coil pack & delay

I purchased a used ignition coil pack and have started thinking about a way to delay the PCM to coil pulses to fire the second coil pack. A variable delay based on engine rpm would be more effective but also more complicated. A fixed delay would be a good evaluation project to determine if there is any potential fuel economy or performance improvement from a second spark. Some members have reported idle stability improvements from ignition upgrades.

Has anyone experienced fuel economy or performance improvements after replacing a functional stock coil with something else?

 

[2000StreetRod]

Dual coilpack, second fire ignition

Thanks to the generosity of snoranger I now have another ignition coil pack and electrical connector and will resume the dual coilpack, second fire ignition project. The idea is to mount the second coilpack above the stock coilpack (hopefully there is enough room), apply a high voltage to the primary of the 2nd coilpack (using a capacitive discharge ignition kit), delay the PCM trigger to the 2nd coilpack (using insulated gate bipolar transistors), isolate the high volt secondaries of both coilpacks (using high voltage diodes) and then combine the outputs of both coilpacks to each ignition wire. The first spark will ignite the air/fuel mixture in the combustion chamber. Once the mixture starts to burn the pressure in the chamber rapidly increases. The second higher voltage spark will overcome the increased cylinder pressure and extend the spark duration. Insulated gate bipolar transistors have an inherent delay when transitioning from conduction to nonconduction which is when the primary field in the coil collapses inducing a high current spike in the coil secondary.

 

[Dono]

I'm looking forward to where this goes. Interesting concept.

 

[snoranger]

Dale,
I can tell you from experience, that the MSD DIS-4 I ran on my '90 4.0l did infact give me a slightly better idle, a slight change in exhaust tone, and about a 1 MPG increase in fuel mileage. Most people will say it just a perceived gain, you changed your driving style, ect. (I never changed my driving style, I ALWAYS drove it like I stole it.) I have tracked ever tank of gas on that truck from the day I got it to the day I retired it (over 10 years, 20K+ miles a year). I ran it for about 4 years mostly stock and 6 years with the MSD.
I had a tach adapter go bad and had to disconnect the MSD on the side of the road. I didnt bother replacing it for about 2 months. I can tell you exactly when I wasnt running the MSD just from the drop in MPG in my log book.

 

[jd4242]

Dale,
I can tell you from experience, that the MSD DIS-4 I ran on my '90 4.0l did infact give me a slightly better idle, a slight change in exhaust tone, and about a 1 MPG increase in fuel mileage. Most people will say it just a perceived gain, you changed your driving style, ect. (I never changed my driving style, I ALWAYS drove it like I stole it.) I have tracked ever tank of gas on that truck from the day I got it to the day I retired it (over 10 years, 20K+ miles a year). I ran it for about 4 years mostly stock and 6 years with the MSD.
I had a tach adapter go bad and had to disconnect the MSD on the side of the road. I didnt bother replacing it for about 2 months. I can tell you exactly when I wasnt running the MSD just from the drop in MPG in my log book.

i looked at this box but couldnt bring myself to spend $569+ for so small of gains.would love to have it tho
http://www.summitracing.com/parts/MSD-62152/

 

[snoranger]

i looked at this box but couldnt bring myself to spend $569+ for so small of gains.would love to have it tho
http://www.summitracing.com/parts/MSD-62152/

Dont forget about the PAIR of tach adapters you would need.

I have the older style DIS-4, before they made the DIS-4 Plus. I got it by trading a new 6AL and Accel coil for the new-in-box DIS-4. We put the 6AL and accel coil on a forklift w/ a 460. The 6al went bad about a year ago, we replaced it. I kept the bad 6al, sent it back to MSD and had it fixed for $50 or so.

 

[jd4242]

Dont forget about the PAIR of tach adapters you would need.

I have the older style DIS-4, before they made the DIS-4 Plus. I got it by trading a new 6AL and Accel coil for the new-in-box DIS-4. We put the 6AL and accel coil on a forklift w/ a 460. The 6al went bad about a year ago, we replaced it. I kept the bad 6al, sent it back to MSD and had it fixed for $50 or so.

I didnt know they had a old and new,you know what the difference is?is it two or three you would need,its been awile sense i looked into it but thought they did two coils each?i was looking into it when i was going to go nos.im sc now

 

[2000StreetRod]

waste spark diagram

The following article provides an informative and concise explanation of the Ford waste spark ignition:
Ford DIS/EDIS "Waste Spark" Ignition Systems
The waste spark schematic diagram shown below is from the article.

It is obvious from the diagram that a bad ignition wire or a bad spark plug will result in two cylinders misfiring since each pair of wires and plugs are in series. The diagram also illustrates that the direction of current flow thru one plug is opposite to that of the other plug in the circuit. The direction of current flow determines which plug electrode wears. I will soon be installing Champion Truck Plugs with alloy coated copper core center and ground electrodes.

There is only one spark plug per cylinder and one wire connected to it. If a second coil high voltage output were connected to the same wire the coil secondaries would interact with each other. I don't know what the effect would be. However, the coil secondaries can be isolated by installing high voltage diodes in series with each secondary output. The orientation (polarity) of the diodes for bank 1 will be opposite that of bank 2. I will have to determine the correct orientation since I don't know if the secondary windings are in phase or 180 degrees out of phase with the primary windings. There is a note on my 2000 ignition wiring diagram that "Each interrupt of primary current makes ignition coil secondary circuit produce an open circuit high-voltage pulse of up to 40,000 volts." I have not yet found any reasonably priced (I'll need a quantity of 12) inline diodes with a maximum reverse voltage greater than 25KV. I can wire two diodes in series to increase the voltage to 50KV (changes quantity to 24) which may be adequate if I utilize a capacitive discharge ignition power supply with the added coil pack. I also need to determine the forward current capacity needed for the diodes. The Accel 140035 is advertised as delivering 10-15% more energy than OEM but doesn't specify a quantity. I will check for the specification of other comparable coilpacks.

 

[2000StreetRod]

MSD DIS-4 Plus

i looked at this box but couldnt bring myself to spend $569+ for so small of gains.would love to have it tho
http://www.summitracing.com/parts/MSD-62152/

I saw a used one of those on eBay about 18 months ago and was tempted to buy it after reading the instruction manual. However, I learned that the unit was not complete (missing wiring I think) and I couldn't find a place to mount it in the engine compartment. I agree the cost is probably not justified except for racing. And even for racing it doesn't provide a second spark at high rpms. I also wonder if there is a different load on the coil primaries which may impact the voltage kickback sensed by the PCM causing it to set diagnostic fault codes.

 

[2000StreetRod]

better idle & fuel economy

Dale,
I can tell you from experience, that the MSD DIS-4 I ran on my '90 4.0l did infact give me a slightly better idle, a slight change in exhaust tone, and about a 1 MPG increase in fuel mileage. Most people will say it just a perceived gain, you changed your driving style, ect. (I never changed my driving style, I ALWAYS drove it like I stole it.) I have tracked ever tank of gas on that truck from the day I got it to the day I retired it (over 10 years, 20K+ miles a year). I ran it for about 4 years mostly stock and 6 years with the MSD.
I had a tach adapter go bad and had to disconnect the MSD on the side of the road. I didnt bother replacing it for about 2 months. I can tell you exactly when I wasnt running the MSD just from the drop in MPG in my log book.

Aldive (Al Franklin) also reported a better idle after installing a high performance coil and slightly improved fuel economy after increasing the spark plug gap.

 

[2000StreetRod]

coil specifications?

Published ignition coil specifications are rather limited and hard to find. After spending hours searching the internet I only found the following information. The MSD Blaster 2 is the old cylindrical style, oil filled, distributor compatible high performance replacement. It is not compatible with the Explorer DIS but it was the only coil I found with useful published data.

OEM Coilpack
Primary resistance: 0.3 to 1.0 ohms (Haynes Manual)
0.5 ohms measured
Secondary resistance: 6.5 to 11.5 Kohms (Haynes Manual)
13.0 Kohms measured

MSD Blaster 2 PN 8202
Turns ratio: 100:1
Primary resistance: 0.7 OHMs
Secondary resistance: 4.5K OHMs
Inductance: 8 mH
Maximum voltage: 45,000 Volts
Peak current: 140 mA
Spark duration: 350 uS


Accel 140035
Higher energy/voltage outputs
10-15% more energy than OEM

Airtex/Wells 5C1125
Primary Ohm Resistance: 0.3-0.9 ohms
Secondary Resistance: 11.0-17.0 Kohms

Beck/Arnley 178-8221
Peak Current: 8.2 amps
Primary Ohm Resistance: 0.5 ohms
Secondary Output Voltage: 36,000 volts
Secondary Resistance: 11,300 ohms

BWD E97P

Davis Unified Ignition/Performance Distributors Screamin Demon 31738
Spark gap - 0.060 to 0.065 inches
Max secondary voltage: 45,000 volts

DELPHI GN10178

Duralast C925
Primary Ohm Resistance: 0.3-0.9 ohms
Secondary Resistance: 11.0-17.0 Kohms

Master Pro 2-5188

Motorcraft DGE446

MSD Street Fire 5529
Vertical primary connector
Capacitive Discharge Technology?
Multiple Sparks?
Max secondary voltage: 48,000 volts

Original Engine Management 5188

Standard Motor Products FD480
Exceeds OEM specifications

Tru-Tech FD480T

United Ignition Wire C438

 

[2000StreetRod]

capacitive discharge ignition rejected

I spent some time researching the evolution of automotive ignition systems. Here's a link to an informative article: Ignition Systems - Basics to High Performance
I learned that for lean fuel mixtures and more complete combustion spark duration is more important than maximum voltage. With the old distributor/coil systems that depend on induction (collapse of the primary magnetic field induces current in the secondary winding) voltage maximum and spark duration were limited. The switch to a capacitive discharge ignition (CDI) system allowed an increase in maximum voltage but the duration of the spark was (and still is) dependent on the size of the capacitor and the time available to charge it. A CDI system typically had a higher ratio coil to achieve a high voltage (1:100 ratio with a 400 volt input = 40,000 volt output). When I built my CDI kit 1:150 ratio coils were available for its 300 volt supply (300 * 150 = 45,000).

With current coil technology and electronic ignition devices (power MOSFETs and insulated gate bipolar transistors) inductive ignition systems can be superior to CDI systems. CDI systems have resorted to multiple spark firings to remain competitive with the spark duration available from the latest inductive systems.

My CDI is about 40 years old (it kept my 1970 Wagoneer running for 24 years) with a small capacitor and single fire capability. It is fairly large and not an encapsulated unit.

The components probably have a lower maximum operating temperature than current technology which impacts under the hood reliability if I could find a place to mount it. I have decided to reject my old and the current CDI technology and incorporate a duplicate stock coil to extend spark pulse duration. I know from dynamometer testing that the stock ignition secondary voltage is adequate to fire up to the PCM rev limit of 6250 (or 6350) rpm. I also know that horsepower with my stock internals plummets above 6,000 rpm so higher voltage is not needed. But greater spark duration should improve low rpm torque and fuel economy due to more complete combustion.

 

[2000StreetRod]

High voltage diodes rejected

I have searched for high voltage diodes to isolate the secondary windings of my first coilpack from an additional coilpack. I wanted a max current flow of 200 ma based on the published current flow of the MSD Blaster 2 coil of 140 ma. I wanted a maximum voltage rating of 40,000 volts based on the note in my wiring diagram for my stock coilpack. I found a 12 pack of 20 KV, 100 ma diodes for $68 on eBay with free shipping direct from China. Even if 100 ma was enough current capacity I would have to wire two diodes in series to achieve the needed 40KV rating which means buying two 12 packs ($136). Then there is the issue of electrically and physically joining the diode pairs to the ignition wires. I suspect the end result would be an expensive, space consuming, vibration sensitive, unreliable mess to achieve minimal performance gains. I am rejecting the idea of high voltage isolation diodes. I still have two other possible implementations to evaluate.

 

[2000StreetRod]

Edis 6

Last night on eBay I "won" an EDIS 6 ignition module, coil pack, and connectors with pigtails for $1 plus $13 shipping. I'm interested in the module circuitry. I wonder if the coilpack is identical to my Sport stock coilpack. I'd like to build a table top ignition system for experimentation but I haven't come up with a way to simulate the 36 tooth trigger wheel with the missing tooth and the variable reluctor. The EDIS defaults to 10 degrees BTDC if no external ignition advance signal is present but requires the missing tooth reluctor signal to determine TDC. I can build a simple square wave generator to simulate the tooth present signals but don't know how to delete every 36th one.

 

[snoranger]

Do you still need the plug wires?

Yes, the coil packs should be the same. Ford only used 2 different style 6cyl coil packs... The only difference between them was the angle the connector attached at. (They use the same connector.)

I may a 36-1 wheel and crank sensor around, if you want to do it mechanically.