Delco Voyager marine ignition system

[DeepBlue2010]

In this thread
http://forums.iboats.com/forum/engi...ngine-rpm-hesitation-at-4600-rpm#post10057679

Post #6, Bondo said the following
Btw,... A brand new Delco Voyager marine ignition system, complete withthe distributor, 'n new plug wires is 'bout 1/2 the cost of replacin' yer Merc T-Bolt ignition ICM,....

I made some research on this system and my understanding ? so far ? is that this system has no ECM, it uses its own coil so Mercruiser coil have to go; and finally it use a single advancement curve for 4, 6 and 8 cylinders GM engines.

If this understanding correct, how can a single advancement curve fits all of these different engines?
Is it really that simple to just drop it in place in any of the engines mentioned above and it is good to go?
No thunderbolt ECM needed? nothing?!

If this is the case, why TB IV, V cost that much for Merc ignition systems, is this the marine thing rip off?

 

[San_Diego_SeaRay]

Another old thread discussing these two systems....

 

[alldodge]

The way I see the issue it comes down to money. Replacing a TB4 or 5 module cost quite a bit. Most don't want to drop 4 to 500 on a new module so the EST is less costly alternative. The timing curve is different and going to EST will change your performance. Just comes down to cost

 

[Scott Danforth]

You could go with a Mallory dizzy and tailor your advance curve anyway you want

 

[JustJason]

If this understanding correct, how can a single advancement curve fits all of these different engines?

It's not a single advancement curve. The pickup coils between a 4, 6 and 8 cylinder are different. The module gets its trigger signal from the pickup coil. The pickup coil sends a signal to the module that tells it both the number of cylinders, and the rpm of the engine. From there the module knows how much advance to apply, and at what rpm.

 

[DeepBlue2010]

If this understanding correct, how can a single advancement curve fits all of these different engines?

It's not a single advancement curve. The pickup coils between a 4, 6 and 8 cylinder are different. The module gets its trigger signal from the pickup coil. The pickup coil sends a signal to the module that tells it both the number of cylinders, and the rpm of the engine. From there the module knows how much advance to apply, and at what rpm.

And how is this being accomplished without an ECM with a memory and processing unit to change advancement based on these two input variable?

The table AllDodge posted above has only one advance values per RPM; are you sure of the accuracy of your info?

 

[bruceb58]

The V8 module has one advance curve. My understanding is that the same module is used on all but the V8 ends up having more advance curve but not sure how that is accomplished.

 

[fishrdan]

It's my perception that the EST is a "one-size-fits-all" ignition system, and while the 4-6-8 curves may not all be the same, all the 4 cyl are the same, all the 6 are the same and all the 8 are the same. Thus the need for the conservative advance curve, which can limit performance.

If you want the best, go with the TB ignition, if you want cheap and reliable, go with the EST.

 

[JustJason]

And how is this being accomplished without an ECM with a memory and processing unit to change advancement based on these two input variable?

Think of the module as a mini ECM that has 1 purpose in life, to control spark advance. For all intents and purposes the pickup coil is a crankshaft position sensor, and the EST ICM is a computer. There is a little microchip inside of the thing.

The V8 module has one advance curve. My understanding is that the same module is used on all but the V8 ends up having more advance curve but not sure how that is accomplished.

The modules are all the same. 4, 6 and 8 cylinder all take the same ignition module. Part number is the same on all of them.

It's my perception that the EST is a "one-size-fits-all" ignition system, and while the 4-6-8 curves may not all be the same, all the 4 cyl are the same, all the 6 are the same and all the 8 are the same. Thus the need for the conservative advance curve, which can limit performance.

It's not a one size fits all. But even if it was. The advance curve is not conservative vs any other ignition system. On a V8 TB4, it's 19 degrees of advance. TB5 normal advance is about 25 degrees. But the TB5 module has an acceleration mode, as well as a mean best timing mode, as well as spark knock detection. On as basic EST only, advance curve is back to about 18/19. But EST used along with a MEFI ECM gets you back to about 25 degrees, along with spark knock detection.

If you have a TB4 system and you have a dead TB4 ICM it makes sense economically to replace it with a stand alone EST system. Performance will be exactly the same.

If you have a TB5 system with a dead ICM, a TB5 is better than a standalone EST, so it would make sense to replace the TB5 ICM. But if you were to replace it with an EST would felt performance be the same? More or less yes it would, you might notice a 100 to 200 rpm drop in top RPM's. (that can vary boat by boat) But for 99% of the people out there would be no perceptible diffence.

 

[Fun Times]

The modules are all the same. 4, 6 and 8 cylinder all take the same ignition module. Part number is the same on all of them.

For the "triangular design" modules (amplifier) 'back in 1987 the new style modules started out with Merc part number 15248A1 for the 24 degrees but they added a few other numbers over the years for certain engine models as evident inside the bulletins linked below...Of course they changed the advance curve internally like mentioned and show the curve numbers on the outside casings.

http://www.boatfix.com/merc/Bullet/87/87_17.pdf
http://www.boatfix.com/merc/Bullet/95/95_11.pdf
http://marinemechanic.com/merc/dist...lder/thnbolt-IV-module-replacements_EN_14.pdf
Item 25, http://www.mercruiserparts.com/Show...NESS/ELECTRICAL(MOUNTED+ON+DISTRIBUTOR)+TB+IV

In August of 1986 General Motors made a design change to the 305/350 CID engines. Incorporated in this change was a new cylinder head design (Figure 1) and a different spark advance curve. Because the Thunderbolt IV HEI Amplifier controls the advance curve electronically, MerCruiser changed the advance curve of the amplifier to accomodate this change. In August of 1987 MerCruiser also had a cosmetic and electrical design change to the amplifier (Figure 2).

DeepBlue2010, Since this is more of a conversation and not really a repair, we're going to move this one on up to iboats Non-Repair I/O and Inboards Discussions not involving troubles or repair. Sponsored by Bel-Ray Thanks.

 

[DeepBlue2010]

DeepBlue2010, Since this is more of a conversation and not really a repair, we're going to move this one on up to iboats Non-Repair I/O and Inboards Discussions not involving troubles or repair. Sponsored by Bel-Ray Thanks.

Sure thing, thanks

 

[kbsunlovers]

A couple of other options if you choose to roll your own curve. I've been using the pertronix dizzy for a couple seasons, I curved it as close as
possible to the TB-IV V8-24 it replaced. Seems to work just fine. SBC with Alpha One & Interrupt.

http://www.summitracing.com/search/...y=Default&SortOrder=Default&autoview=SKU&ar=1

http://www.summitracing.com/search/...SKU&keyword=pertronix marine distributor&ar=1

 

[JustJason]

The modules are all the same. 4, 6 and 8 cylinder all take the same ignition module. The part number is the same on all of them.

For the "triangular design" modules (amplifier) 'back in 1987 the new style modules started out with Merc part number 15248A1 for the 24 degrees but they added a few other numbers over the years for certain engine models as evident inside the bulletins linked below...Of course they changed the advance curve internally like mentioned and show the curve numbers on the outside casings.

When I say the modules are all the same I mean the EST modules, not the old tb4 modules.

 

[REV6String]

A couple of other options if you choose to roll your own curve. I've been using the pertronix dizzy for a couple seasons, I curved it as close as
possible to the TB-IV V8-24 it replaced. Seems to work just fine. SBC with Alpha One & Interrupt.

http://www.summitracing.com/search/...y=Default&SortOrder=Default&autoview=SKU&ar=1

http://www.summitracing.com/search/...SKU&keyword=pertronix marine distributor&ar=1

Did you use the original coil, or upgrade to a PerTronix?