ignitions compared (1 Viewer)

[coiled40gary]

Hi,

I've been sitting on this for a long time. A long time ago, some of us on the LCML were talking about putting a book together on LC electronics. I was going to do a chapter on ignitions. But that is not going to happen. I see often people wanting to know about which ignition to put in their LC, including a recent thread, which made remember I had this stuff, and now that I'm on a forum that I can put pictures on...

Now, I'm not claiming to be an expert, but I did take some automechanics in High school 30 years ago, and spent a year analyzing ignitions on a Sun scope. Ignitions back then are very different from ignitions today, but the basics is still the same. So here is some info, take it or ignore it as you see fit...

To start, in this pucture you will see two traces, the lower one is the primary ignition circuit: battery, ballast, + side of the coil, points, condensor. You will see the points open, higher voltage, and the points close, lower voltage. The upper trace is the secondary circuit: coil high tension lead to spark plug.

Focusing on the part of the traces that we are most interested in, the spark... You will see at the instant the points open, there is a spike in the secondary circuit. This is the energy dumped to the spark plug to bridge the gap with an arc. The larger (higher voltage rating) the coil, the larger this spike will be. Then you will see a changing (fading)voltage level, this is the energy depleting across the spark in the plug gap. Then you will see another spike. When the fuel actually ignites, the blast will "blow out" the spark making the plug gap an open again. The length of this second spike is an indication of the energy remaining in the coil after ignition has occured. My contension is that the length of that second spike is a valid measure of the ignition. If there is no second spike, then we don't know if the fuel ignited, or if the energy ran out, and there was a miss fire.

 

[coiled40gary]

The above picture was of the stock '76 points ignition without the Toyota ignitor.

Below is the secondary trace of the HEI ignition. You will note the large initial spike, but the second spike actually varied quite a bit in length.

 

[coiled40gary]

This is a Jacobs Omni Pak on the stock '76 LC distributer.

You will note that the first spike is as long as necessary to establish the spark, and there is plenty of energy remaining after fuel ignition.

Got to go see the PT for my should... I'll be back with an other trace or two, but you got the stock points, stock points with Jacobs, and the HEI.

gary

 

[dfmorse]

Scope pictures

coiled40gary; thanks for the great shots. Now I know why my FJ40 will do a 1/4 mile in 10 sec at 110.567 mph...

David in Denver

 

[coiled40gary]

I'm back...
Here is another shot from the Jacobs on the stock '76 distributer, you will see that even when it has to dump more energy into the initial spark to establish the arc, there is still plenty of energy left when the fuel ignites.

 

[coiled40gary]

Here is a standard electronic ignition from a Dodge Lancer

 

[coiled40gary]

Though I am currently running a DUI HEI in my 2F, I still think my best performing ignition was the stock '76 distributer, recurved machanical only, with points and the Jacobs Omni Pak. And I think the scope traces back up what I felt. I have run two different MSD ignitions in the past, but both were short lived for me, and the factory said there was nothing wrong with them. They did "feel" the strongest, which I can not explain.

Another Oregon Bush Hackers (OBH) member, brought a fancy scope home from work (Techtronics). We tried to get others on the list with other ignition types, particularly requesting someone with an MSD ignition, but no one stepped forward. We had hoped for more extensive testing of more ignition types, but this is what I have. I hope it is useful to someone...

gary

 

[yotanut]

Gary, thats some great info. I'm glad you posted it. When you were talking about a stock 76 ignition, how did you take care of not having a condensor?
Is it the same distributor that came with the ignitor setup?
-Duane

 

[Pin_Head]

As long as the spark ignites the air/fuel mix, it is all good.

 

[Coolerman]

I have to agree that the Jacobs Omni-Pak is a great ignition. I just have a huge problem with their support. I ran one (actually two, see below) in a Pathfinder and there was no doubt that the truck had more power especially in the mid band. I was able to run a plug gap of .055. However, the first one lasted exactly one year and 20 days then quit. Jacobs warranty is (was) only 90 days but they agreed to replace the unit if I would ship it back and pay them $75.00. I did this. The new unit lasted almost exactly 11 months and failed again. This time they would not replace it. I called tech support on a whim and asked some questions about the Omni-Pak. I was told that the early Omni-Pak system had a flaw in the design. A resistor was undersized and would fail due to heat. Several phone calls and letters later and still no joy. I was out over $300 and had less than two years of use. Not my idea of a company standing behind a product.
So while it is a excellent unit when it functions I personally will never buy anything from them again. I don't appreciate being a test subject. (This flaw has supposedly been fixed in newer units. )

Be interesting to see some traces of a stock Toyota ignition from a later (1987) FJ60. I'm about to put one in my 1971

 

[cardinal fang]

Wish you would do a pertronixs setup just to compare it with the others. A lot cruisers are running the pertornix setup.

 

[bonzai]

Keep in mind I am new

No MSD
Are MSD's not as good?

 

[coiled40gary]

When you were talking about a stock 76 ignition, how did you take care of not having a condensor?
Is it the same distributor that came with the ignitor setup?
-Duane

Yes, this is the original that came with an ignitor and no condensor. My ignitor died about 23 years ago. Looking at old receipts, I have two Toyota part numbers for condensors: 90099-52050 and 90099-52060. One of these if not both of these was made to work.

These condensors should have a tab with a hole on the body, and a connecting wire out the end. I bend the tab up away from the condensor body, and screw it into the outside of the distributer with the little screw in the side to hold the vacuum advance in position. The wire that comes through the distributer housing, I used crimp on spade connectors and made a small Y cable. One leg goes to the distributer, one leg to the minus (-) terminal on the coil, and one leg to the condensor. I cut the end off the condensor wire and crimped on a spade connector.

Hope that helps,
gary

 

[coiled40gary]

As long as the spark ignites the air/fuel mix, it is all good.

Yes, infact I had a line in the original post that I deleted before posting, that fuel ignition every time is the best you can hope for. All things left the same, a stronger spark makes no difference beyond that. Hot coils make the initial spike very large, but its the second spike that tells you the ignition did its job with some thing to spare.

Now, consistancy in the time period between discharging the coil and igniting the fuel is a good thing too. Then you can set you intial timing advance to compensate for this time lag at idle, and set your distributer curve to compensate for this lag as a function of RPM. The RPM will dictate how far the piston travels during this lag period, so as the RPMs increase, the ignition process has to start earlier to insure the fuel ignition still occures before TDC. If this lag period varies irratically, then the timing will feel like it is varying irratically.

A larger spark plug gap will create a longer arc, which causes the initial fire ball in the cylinder to be larger, igniting the cylinder sooner with more repeatability in the time period. This larger plug gap needs a stronger ignition. So, the benefit in a stronger ignition in an otherwise perfectly running ignition, is that you can enlarge the plug gap and gain that benefit.

gary

 

[coiled40gary]

I have had good luck with Jacobs service in the very beginning, but that changed then they became more popular. The phone tech support I've gotten from them was pretty much useless and very frustrating. Dr. Jacob wrote a very good book on ignitions, but it is very obvious that they do not require their phone people to read their own book. The last time I got good service from them, they replaced some parts for free after 5 years, but I had to debate with the first level of phone service until they passed me on to someone who actually had an idea how their ignition was supposed to work.

I got my Omni Pak in '95, and it lasted me about 8 years. Their Opti-Timer lasted me a couple years, and I have been running my entire truck (except the starter and now the welder) off their 100 Amp Accu-Volt for almost 10 years so far.

I did figure out that the Omni Pak is susseptible to issues in the supply voltage. A couple times I thought the ignition had started failing, and each time I discovered that cleaning my battery terminals solved my ignition miss. My battery terminals had this weird problem where they just turned black with a very hard coating I had to file off. When this coating would develop, I would soon start getting an ignition miss. I solved the problem with the battery by putting in an Optima (no more out gassing). I put the Accu-Volt on the truck to insure there was always 14.3V (setable) to the ignition regardless of the RPM. My ignition ran very well from there on out, except for the failure of the stock coil that pumps the frame. That is my one big beef with the Omni Pak, is that it gets it's trigger from the original coil, not just the points, and the original coil's high tension lead runs through a load to the frame. If this coil fails, the ignition fails. Anyways, the Accu-Volt also solved the problem with the wipers, blinkers, head lights, defrost fan all fading out together after about 3 seconds idling at a stop light on a cold rainy morning.

I had two MSDs fail on me in less than a year each. I now think that they may have also suffered from a source voltage issue.

gary

 

[coiled40gary]

Are MSD's not as good?

I think MSD are probably very good ignitions. When I ran my first one, close to 25 years ago, I really felt the improvement in the seat of my pants. MSD ignitions were not known back then, but I knew they had implented a CDI ignition that dumped three charged caps for each spark. I thought that was an interesting idea and bought one. A friend of mine back there in Tucson drag raced boats, and I tried real hard to get him to put one in his boat. He said if they were any good, everyone would be running them. I told him he needed to lead the pack not follow the pack if he wanted to win. A few years later after I moved to Portland, he told me any one who is anyone on the boat circuit is running MSD .

I just had bad luck with two units, and have not ruled out the fault may very well be my own. But I know others who have had good luck with them, and I have read LOTS of posts about how Jacobs it trash. Which is why I wanted to do the comparisones with the scope, and have real quantifiable data.

I ran the MSD ignition module, and coil for the DUI HEI I have now, and did not notice any difference from the DUI ignition module and coil. The MSD module was a long curved PC board, and the DUI unit was a much smaller hermetically sealed chip. But the non-DUI rotor rubbed on the mechanical advance mechanism making the timing stick.

gary

 

[Pin_Head]

Save your money. High voltage/ high energy/ super intensity ignitions have virtually no performance gain over a properly tuned stock distributor that is functioning properly. Zero, zip, nada, nichts, nichivo. They are less reliable.

My engine always feels a lot stronger every time I tune it up and I don't have to change the ignition.

 

[Nick the Carpenter]

have to second that pin head, pentronics gave know more hp on the dyno but it hassel free and more aqcute on intion timing.The set up cost me $235 for sensor $100 for 3ohm coil (aus$) all matched up on a dyno.

 

[coiled40gary]

Save your money. High voltage/ high energy/ super intensity ignitions have virtually no performance gain over a properly tuned stock distributor that is functioning properly. Zero, zip, nada, nichts, nichivo. They are less reliable.

My engine always feels a lot stronger every time I tune it up and I don't have to change the ignition.

Well, sorry to have waisted your time.

But for others who may be interested...
If you are getting fuel ignition in a consistant time period 100% of the time, replacing your ignition will buy you nothing. An aftermarket ignition that claims 15% increase in horse power and/or gas milage is based on the assumption that your current ignition is not working properly, and they will simply give you one that is working. This is generally believed by the public because they are usually motivated to buy an igition when the old one is needing a tune up, and they see a noticable change. As Pin_Head pointed out, a tune-up would have given you the same change. If you are trying to pick an ignition based on which one will get you more horse power, you are making a mistake.

However, particularly in our Land Cruiser world, for those who are still running Land Cruiser power plants, and for those who say:

My engine always feels a lot stronger every time I tune it up and I don't have to change the ignition.

There are some very distint benefits to a modern add on ignition.
Many LCs still run points. I am a strong advocate for points ignitions. For field servicability you can not beat a points ignition. When my ignitor died two days walk out in the Arizona desert, with passengers that would not take a half days walk, I was real glad I had a condensor in the glove box and simply wired up a standard ignition and drove on. With a couple inexpensive parts that can live in your glove box for decades and still work, any electrical and many mechanical ignition problems can be diagnosed and solved in 10 minutes. But we are all aware of the draw backs of points ignitions. Those draw backs fall mainly in two camps, the points ability to handle the primary ignition current over a period of time, and the post wearing on the cam. These two issues lead to the need for frequent tune-ups. If you add on an aftermarket ignition that uses the points as a trigger only, then the primary ignition current no longer flows through the points. They will no longer burn or pit and will last for years. And the problem with the post wear is reduced to a slight retard in timing, and no longer effects the spark charge. As long as they open at all, your ignition will work.
I did a tune up once every two years for DEQ, and saw no difference in the engine running. Sometimes I did not tune up, and still passed DEQ. And believe me, a 30 year old de-smogged LC does not pass DEQ if it has a miss.
So a points ignition can benefit from a modern aftermarket add on by keeping your ignition in that just tuned up state a LOT longer, with a LOT less work. You can have the "set it and forget it" feature of a modern ignition and still keep the field servicability of a points ignition.
The reason I posted the traces is so those who are interested can make an ignition choice based on which ignition is more likely to provide 100% ignition, instead of basing it on highest voltage out, and horese power hipe.
There are real interesting advancements in ignitions, not even looking at the modern one coil per plug no distributer ignition, there are varying periodicity coils that perform better at both low and high RPMS. The MSD trys to insure 100% ignition by delivering three sparks (at least at low RPMs) hence the name, Multiple Spark Discharge. The Jacobs claims to use an impedence matching circuit to monitor when the spark establishes, then the fire ball starts, and when the fuel ignites, providing a real time dynamic spark profile to insure 100% ignition. The Jacobs also automatically by-passes it's internal ballast resistor when the RPMs get real low to provide a hotter spark in that range.

Hope that helps someone,
gary

 

[Pin_Head]

Well, sorry to have wasted your time.

But for others who may be interested...
gary

I think you are taking this the wrong way. I don't think it is a waste of time and I largely agree with you. My point is that the vast majority of the people buying the ignitions mentioned here are doing so because they are buying the hype about more horsepower and better economy that the vendors are pimping.

You can have all the benefits of a breakerless electronic ignition (if that is your preference) or the reliability and field servicibility of a points type breaker driving an ingitor (my preference and yours) without shelling out $300-$500 and getting something that burns out after a year. You can use the stock electronic ignition, which is a very fine distributor and ignitor, or you can use a stock points style distributor with an OEM ignitor or a $15 generic solid state ignitor from NAPA.

Many of the benefits touted by the aftermarket vendors are more hypothetical than actual. Multiple sparks, continuous sparks etc are meaningless because the fuel is ignited 99.99999% of the time on the first spark with a properly functioning ignition system. Some benefits are real, but they don't apply to the F/2F motors because they only become an issue at RPMs above approximately 7,000 RPM.

The reality check is in the emissions. If stock ignitions were so unreliable that you needed multiple sparks to ignite the fuel, the unburned hydrocarbon would go way up because of the misfiring. Your average stock engine puts out unburned hydrocarbons in the parts per million range, which is less than a spit in a bucket.