Ignition Options-gctid822161

[mister_larry]

Let us agree that a new boat with a guarantee and stock loading and weight distribution should perform exactly as the boat builder made it to perform. Any change to that build can negate the warranty. This conversation is about after-market modifications to used boats whose owners know how to drive the boat, know how the boat performs, and want something better. Engine modification has been discussed at length in another thread. But in those posts there was no input regarding the ignition system.

Undoubtedly other boaters will have advice as to quicker, or cheaper, or easier ignition tweaks they have used. Fine!.However there is one system used exclusively by marine and auto racing machines: the multiple-spark system. If we invest in a piece of performance equipment, but still drive the same way and don't ask it to perform, we get better mileage. The flip side of performance can be economy. This is true of multiple-spark ignitions. Allowance needs to me made for the possible delivery of more air and fuel, but if you don't deliver the A/F charge to the ignition there is nothing to ignite.

There may be others, but i know the US Coast Guard has approved the system manufactured by Autotronic Controls Corporation. Their multiple-spark distribution (MSD) ignition module needs to be joined by their performance distributor and hi-performance coil with more capable plug wires delivering spark to bullet-proof plugs. A mariner could be into this system for a bit of money but the results are well worth it. More powerful spark delivered more times at each plug firing equals better use of fuel. What if the difference is 10% better economy? What is 10% of the cost of feeding two, big block 454's during a long, hot summer?

The MSD installation involves installing a module that is loaded with powerful capacitors and re-wiring the existing ignition triggering signal through the module. The capacitors grab their voltage directly from the coil and instantly dump their load to the plugs, thus not waiting for the coil to charge. In the event anything goes wrong, it's only a matter of plugging the points wiring back into their original connector and the stock ignition is then in play.

The MSD folks have a very informative web-site and parts are available via many auto and marine parts stores. They have a special marine catalog with a variety of plug-n play modules, distributors and other components. I have found their technicians willing to talk if you have an application they don't have a wiring diagram for.

I have a book written, partially on this subject, available through the BOC mall. Fuelish Pleasure Boats has charts and graphs and data to confirm what can happen if the boat is modified this way. Beyond changes to trim and attitude, the ignition system offers one of the easiest and best ways to get some improvement in fuel-efficiency.

[SprinterX]

I'd be interested to hear your thoughts on the Nology line of ignition products and their theory of producing a better, more efficient spark.

[Ruffryder]

TB 4 is a great ignition system & very simple!

Good TB4 VS MSD discussion here...

http://www.offshoreonly.com/forums/general-q/138186-msd-thunderbolt-4-a.html

[mister_larry]

Thanks for the heads-up on the Nology line of ignition products. It looks like a great system for certain applications. Obviously, vehicle needs vary and powerboat needs are often a lot different than those of an automobile. Notice that the Nology folks have not tried to get the USCG approval on all their products. That approval is quite time consuming, therefore expensive. So you can get some wires for personal watercraft, and that's it. Nothing approved for a couple of big block 454's on the water.

I might mention that their marketing description of "faster, more complete combustion" makes a lot of sense. However, if you change the timing a bit on your stock ignition system, you can get faster spark, and if you use a hi-performance coil you can also get more complete combustion. The fact that the wire acts as a capacitor and delivers quicker spark when it finally dumps the load to the plug, only becomes significantly advantageous when the engine is turning at a higher rate of speed. Considering the speed of electricity, you can see that the difference between a charge delivered a couple inches away from the plug vs. a charge delivered through the distributor, two feet away from the plug will not be that measurable while cruising at 2500 RPM. But if you are racing at 6,000 RPM this means a lot in the performance/power curve.

Off hand I would say that their primary market is the automobile and it will stay that way for some time.

[mister_larry]

There is no question that the TB4 system is simple and that it works. One would hope that the ignition system installed by the engine manufacturer would be reliable and efficient. It is when those fail, or when skippers want more power, that ignition differences come into play. It seems that too many of the ignition decisions are made without thought being given to what the boat is used for and/or how it is driven.

In the larger pleasure craft (or gas powered work boats for that matter) the engines rarely cruise at a hi RPM. Marine engines that are always under load and cruising between 2000 and 3000 RPM have special needs if we want to eek the last bit of power out of every ounce of fuel. Electronic Ignition triggers are a good place to start when replacing old fashioned points. Ignition amplifiers and Hi-performance coils boost the spark to the plugs and generate more power at each firing. But all these leave a fair amount of unburned fuel in the combustion chamber. Dished piston or not (this seems to be an issue on other threads) the research in combustion reveals that the flame front only travels so far before the massive confusion in the chamber causes some unburned gases swirl behind it, and the plasma front is extinguished, then sent out the exhaust valve.

Assuming for a moment that the various systems deliver the same voltage to the plug, at the moment of firing they will get the same result. However the MSD unit delivers another spark. That second jolt ignites some of the unburned fuel delivering some power,and creating more confusion. Then it does it again, and again. As fast as it can for a crankshaft 20degree rotation, it's jolt after jolt. Sure, the piston is on it's way down so each firing is less powerful that its predecessor, but it all adds up.

I have scoped the MSD unit and can confirm that at 1000 RPM it's firing five times. It drops down to one firing per revolution at just over 3,000 RPM.

Only the skipper will know where the boat cruises, and whether the investment is worth it in the long term. In the short haul, there is no contest when trying to plane and proceeding through that 1000 to 3000 range. No ignition system delivers more efficiency. It is expensive, though.

[builderdude]

"mister larry" post=822420 wrote:
I have scoped the MSD unit and can confirm that at 1000 RPM it's firing five times. It drops down to one firing per revolution at just over 3,000 RPM.

MSD fires for 20 degrees of crankshaft rotation only up to 3000 RPM. How does this compair to a Mercruiser TB ignition? Any testing on the TB? IMO 3000 RPM and above is where ignition matters most on these cruisers.