Thunderbolt IV ==> Thunderbolt V?

[harringtondav]

So I'm wasting my Sat. afternoon time pipe dreaming, and probably will be wasting some of your time too.
I'm wondering if my '96 4.3LX could be converted from it's Thunderbolt IV to a V. Assuming the graybeards don't answer "Nope", I have questions.

First mine is working fine, and hopefully will continue. But if it dies, I see there is only a few $$ between a replacement IV ICM and the V that is used on the '98 -on 4.3LH Gen+. In fact the ICMs look the same, except the IV includes a jumper harness (apparently worth $25).

Since I'd sunk the big $$ into the ICM, I might want to go to the full Thunderbolt V Knock Sensor system. It's timing advance curve looks like it could provide advantages.

So:
1) My manual shows the V's knock control module piggybacked on the ICU, but I can't find any knock sensor p/n's. Is it separate, or built into the V's ICM? If so, what is the p/n?

2) Integrating the wiring could be my show stopper. Online parts manuals are vague with the V's connector. This makes integrating the knock control module a big question. Any thoughts?

2) My manual also shows the knock sensor in the starboard block, in front of the starter. Does my LX have this port plugged? Is it in the water jackets or oil pressure gallery? My manual shows a common knock module signal wire with the ICU, but doesn't show the knock sensor input?

Whew, and thanks.

 

[alldodge]

Yes, you can remove the TB-IV and install the TB-V, but you also need a knock module. The issue so far is not sure as there is a knock sensor been made for a V6. Not saying there isn't but will keep looking.

Now that said, you can also wire up the TB-V in place where the IV was, but connectors will be an issue, unless you can find a parts motor

 

[Scott Danforth]

I would probably simply switch over to a Delco Voyager if your TB IV fails.

 

[harringtondav]

Thanks. I'll check out the Delco controller. I didn't know anyone had broken Mercs. monopoly. I'll never live long enough to pay back any benefits from the the full-blown TB V

 

[achris]

TB -IV is no longer available. If you use the TB-IV part number it supercedes directly to the TB-V. Even for the V6. As for knock sensors for V6, yes. I know my MPI has then and I think the carbed, TB-V 262 Magnum had them. And the superseded part has all the harness adaptors too.

Chris. ....

 

[harringtondav]

TB -IV is no longer available. If you use the TB-IV part number it supercedes directly to the TB-V. Even for the V6. As for knock sensors for V6, yes. I know my MPI has then and I think the carbed, TB-V 262 Magnum had them. And the superseded part has all the harness adaptors too.

Chris. ....

Thanks moderator. I've got Scott Danforth 's Delco Voyager penciled into my parts manual. But I'll continue pondering the TB V based on your input. I'm assuming the merc TB IV to TB V substitute (15247T02 - Ignition Control Module With Harness) dumbs down the spark advance to safe levels without knock sensor input. (???)

 

[achris]

Knock sensor is used by the ignition module to retard timing in the event of spark knock/detonation. Without a knock sensor the module will assume a 'standard' curve. Which, in most circumstances, is just fine. Engines ran for year without knock sensors..

The V6 TB-IV module was a -805361T1, which has been supersedes to 15247T02, which includes the harness. A knock module is 806611T and the sensor is 806612T. The wiring is very simple. Knock module requires a ground, power (for the coil +), a wire from the sensor, and the input to the TB-V module, which is the purple/wht, the wire you ground to set the module in base timing mode! Does that mean all the knock sensor does it put the module into base mode? No, not at all. Base mode is achieved by grounding the wire. The knock module applies a voltage to the wire, that will make the module perform in a different way. It will retard the timing, about 2 degrees at a time, until the knock stops.

To install knock sensor, only one required, remove the water drain fitting, fit a new fitting, part number 22-8067051, into the hole. Fit the knock sensor into one of the holes in that fitting, and the water drain plug into the other.... Like this....



Hope this helps....

Chris.........
(Only a moderator when someone's being naughty. )

 

[alldodge]

I'm assuming the merc TB IV to TB V substitute (15247T02 - Ignition Control Module With Harness) dumbs down the spark advance to safe levels without knock sensor input. (???)

No, the spark curve is basically the same, and IMO your over thinking the issue way to much. While knowing if there is a preignition knock is vital, the V or EST in there basic advance curve does nothing for this. The V requires a knock module, and the EST requires similar but none is available without a ECM (MEFI 1 thru 4).

Suggest stay with what you have until which time it fails, but also in IMO, its going to be a really long time from now, unless something drastic happens

 

[achris]

..... The V requires a knock module, and the EST requires similar but none is available without a ECM (MEFI 1 thru 4)....

TB-V is a stand-alone unit, and can be configured with or without a knock sensor. MEFI is a different fish...Here's the TB-V timing graph.... If there is no knock sensor, then there is no knock sensor input, so we don't have the knock retard function. Timing curve remains the same (as the graph indicates) for all other functions.

 

[harringtondav]

No, the spark curve is basically the same, and IMO your over thinking the issue way to much.

I am. But I'm a retired obsessed optimizer. I have achris 's timing curve in my merc. #18 manual, and those MBT cruising spark advances look like fuel savings. But, as I said I, probably won't live long enough to pay for the upgrade,...unless my TB IV dies soon. And if it does, I'll be pondering hard on the trade-off between the Delco Voyager and a TB V convert. I've kept my 22 yr. old Larson pristine, assuming my son will take it over. But he wake boards and tubes, and won't care. But this chat is going to a Snipping Tool print out, and into my parts manual.

Thanks experts.

 

[achris]

... those MBT cruising spark advances look like fuel savings. ...

Yes, but not as much as you'd think. Because a marine engine is always 'under load', unlike a car which runs up to speed then 'throttles back', that spark advance needs to be carefully controlled and it's not a great deal, or you end up with 'see-thru' pistons.

The main advantage of TB-V is the idle control.and the acceleration advance. Neither of which are fuel savers.

Chris....

 

[alldodge]

TB-V is a stand-alone unit, and can be configured with or without a knock sensor. MEFI is a different fish...Here's the TB-V timing graph.... If there is no knock sensor, then there is no knock sensor input, so we don't have the knock retard function. Timing curve remains the same (as the graph indicates) for all other functions.

Your trying to make a point which was not made. The V requires a knock module like 806611T to retard timing

The V was initially installed with the MEFI 1 and later changed to EST. The MEFI retards the timing.

Now if you know of a knock module used with the EST then this would be new info and would like to know

 

[achris]

...The V was initially installed with the MEFI 1 and later changed to EST....

Just curious, which engines had a TB-V module and a MEFI1 unit on at the same time? (As far as I was aware, an engine had TB-V and a Carb OR a MEFI and injection)

Chris.......

 

[alldodge]

Just curious, which engines had a TB-V module and a MEFI1 unit on at the same time? (As far as I was aware, an engine had TB-V and a Carb OR a MEFI and injection)

Chris.......

Should have said MEFI 3 it's in manual 25 and 26, here is 5.0 and 5.7

 

[achris]

Should have said MEFI 3 it's in manual 25 and 26, here is 5.0 and 5.7

That's the injected engine, with MEFI. The distributor has a sensor in it which feeds (cam) positional information back to the ECU. No TB module here. The diagram a few pages before that one, which does have a TB module, is the carbed engine. .. and that doesn't have an ECU....

 

[alldodge]

Guess we are splitting hairs, its a TB distributor