How far can you advance a Thunderbolt V...?

[AKJohne]

1997 5.7 LX, 4 brl carb. Thunderbolt V w/ knock sensor

According to the book base timing on this motor is 10 degrees.

I am not sure what ICM/module I have (its original), I am wondering what happens if I "cheat" base timing to get more TA?
Assuming the knock sensor/module is working properly, I believe I should be able to advance the TA to 32 or 34...

I have not been able to find a listing for what the TA should be on this motor, I know Merc made different modules?
I bought a spare ICM Module 807364-3 that a dealer had sitting on his shelf, I know this part has been superseded by 807264A01.
The plugs are different otherwise I assume they do the same thing internally........?

Typically we cruise at 3200-3400, we are propped OK at 4400-4600 WOT, I am expecting that to go up if I can get more TA.

Thanks......!

 

[alldodge]

Yes, you can advance the timing more but do this at your own peril. It can take just a few seconds to destroy the motor, and I would not suggest leave it up to the knock sensor, but its your boat

The module should have something like V8-20 or V8-22 marked on it, this will tell you how much advance and that its for a V8

Your reaching 44-4600 rpm at WOT, so why do you want more advance?

 

[harringtondav]

Listen to AllDodge . TB5 is sophisticated, with high TA under the right conditions. You won't gain anything except engine trouble. It may result in less performance as the TB5 reacts to the knock.

 

[Scott Danforth]

Typically we cruise at 3200-3400, we are propped OK at 4400-4600 WOT, I am expecting that to go up if I can get more TA.

Thanks......!

expecting what to go up? your top speed.....aint going to happen. this isnt a car, its a boat. think dumptruck fully loaded while driving up-hill in sand in top gear. more advance wont help. more motor will

 

[AKJohne]

Thanks guys, its a heavy boat and I am not looking for top speed, just best fuel economy. I only ran it to WOT to make sure we were propped right and 4400-4600 RPM only indicates the prop is right for XX advance.
The story gets slightly more involved as I have heard the Tbolt bashed by a local mech. He claimed they dont advance as much as they should. I trusted his opinion and first time out I checked TA at ~ 3200, unfortunately I dont remember the number..... however I turned the dist while running to just over 30 degrees.

We were seeing fuel burn of 2.2 MPG on average, we are using a NM2K paddle-wheel sensor and Lowrance LMF for our fuel gauge and fuel flow monitoring, however the real proof was when we refueled the boat and calculated the average.

In any case, the boat has been a 5 year project rebuild and the motor has low hours. At the end of July I planned a trip with my wife and when leaving the dock the motor crapped out. I finally diagnosed the Ign sensor in the distributor (it had the old style). I got a new sensor checked base and set at 10, fuel mileage on that trip was 1.9 and 4400 was max. Maybe 4500 on the way back when we had burned off 120 gallons of fuel.

In any case I am thinking we are slightly over-proped, before I start experimenting with props I want to make sure I am seeing the proper TA. I started to learn more about the TB5 and have decided to stick with it as I think its a good system (other than costly to repair) After the sensor failure I decided to get some spares and bought a ICM, it is NOS and does not have any indication of advance other than the part #. The boat is currently 400 miles distant and not EZ to lay eyes on the current module.

I think this motor can take 32-34 degrees TA, (with 90 octane) and assume the knock sensor will do its job, I can test that statically and underway. My plan was to check TA with base at 10, then set base at 12 and check performance and TA. If all is well go to base at 14...... and stop there.... I am assuming the module I have adds 20 degrees.

If the K-sensor checks ok, I assume if I went to far I should be able to see it on the tach and with a timing light..

Sorry for the long winded answer......

 

[alldodge]

Good to hear your doing the research, and even though I have a difference of opinion about TB, that's no biggie.

Your going this much to find things out, I would suggest getting an AFR meter and see what you fuel mix is, this will keep you out of harms way.

Wish my 27 footer got 2.2 to the gallon

 

[Scott Danforth]

Thanks guys, its a heavy boat and I am not looking for top speed, just best fuel economy. ..

then get a boat with oars or a sail.

if it has a motor its going to use fuel, a boat is not fuel efficient Think gallons per mile, not miles per gallon. an I/O will burn 0.4# of fuel per HP per hr

 

[achris]

....The story gets slightly more involved as I have heard the Tbolt bashed by a local mech. He claimed they dont advance as much as they should. I trusted his opinion and first time out I checked TA at ~ 3200, unfortunately I dont remember the number..... however I turned the dist while running to just over 30 degrees.......

That 'local mech' is talking out of the wrong end of his digestive tract... Knows absolutely nothing about Thunderbolt ignition systems.

The TB-V system is adaptive, and will advance as much as is necessary to achieve the best results. Have you looked at the TB-V advance chart? (Has he?) With the knock sensor you will get the most advance possible on the engine for the given day, engine condition and fuel quality. You're primary goal is fuel saving, that is also TB-V primary goal. The only way to use less fuel, sell the boat. Boats are not, and never have been, cheap to run, due to the environment and how that operate, the engine is always under load. There is no 'backing off' like in a car where you accelerate up to speed, then back off and let the engine 'tick along' to keep you at a particular speed. If you back the throttle off on a boat, you immediately slow down.

Set the advance, in base mode, to what is specified and leave it there. If you over-advance it, there will not be enough retard available to adjust for low fuel quality and you WILL knock holes in the pistons...

This is an extract from the Merc service manual.... Just one of several features of the TB-V module...Worth keeping in mind....



MBT advance can add 10-15 degrees to the advance to the CURVE, not the base timing, the base timing PLUS the curve. Given that, on a good day, you could be getting a TA of 45 degrees... If the fuel quality and engine load allow it...

You really what to mess with that sort of engineering excellence?

Chris............

 

[AKJohne]

Good to hear your doing the research, and even though I have a difference of opinion about TB, that's no biggie.

Your going this much to find things out, I would suggest getting an AFR meter and see what you fuel mix is, this will keep you out of harms way.

Wish my 27 footer got 2.2 to the gallon

Thanks, that is a excellent thought, any sources or ideas on installing a O2 sensor on this motor.....?

 

[Scott Danforth]

To what end? Wet exhaust makes it nearly impossible to tune with an O2 sensor. Read the plugs

 

[AKJohne]

That 'local mech' is talking out of the wrong end of his digestive tract... Knows absolutely nothing about Thunderbolt ignition systems.

The TB-V system is adaptive, and will advance as much as is necessary to achieve the best results. Have you looked at the TB-V advance chart? (Has he?) With the knock sensor you will get the most advance possible on the engine for the given day, engine condition and fuel quality. You're primary goal is fuel saving, that is also TB-V primary goal. The only way to use less fuel, sell the boat. Boats are not, and never have been, cheap to run, due to the environment and how that operate, the engine is always under load. There is no 'backing off' like in a car where you accelerate up to speed, then back off and let the engine 'tick along' to keep you at a particular speed. If you back the throttle off on a boat, you immediately slow down.

Set the advance, in base mode, to what is specified and leave it there. If you over-advance it, there will not be enough retard available to adjust for low fuel quality and you WILL knock holes in the pistons...

Chris............

I have come to the same conclusion on the TB5, I like the idea of a knock sensor and I am fully aware that a boat engine is much more of a "stationary power plant" compared to a car engine.... thus I am asking questions. No need to suggest selling the boat,I didnt bother to reply to the snarky comment made by another member.

This motor did not come in this boat, so it may have been setup for a different application. I have looked at the charts... if I am looking at the right one....? Maybe I am missing something.......?

I would like to know what the TA should be with a 807264T ICM. That is the piece of the puzzle I havent found yet. Believe me I have searched before I asked, here and elsewhere, I spent several hours last night perusing the sticky for DIY by Don S. Very informative.... Still what is the TA?

 

[achris]

...I would like to know what the TA should be with a 807264T ICM. That is the piece of the puzzle I havent found yet....

And you wont find it. Merc have never published it (I know, I used to be a Merc dealer, and I asked for it)... As I said, it's adaptive, so the timing will be 'dancing around' if you point a timing light at it...

The best thing you can do it to trust that the Merc engineers know what's going on...

As for the engine being in a different boat, makes no difference, the timing is adaptive...

Chris..........

 

[alldodge]

To what end? Wet exhaust makes it nearly impossible to tune with an O2 sensor. Read the plugs

Ahhhh no, just need to install bungs and unless your going to run at 1/2, 3/4 and full throttle and kill the motor, your going to get incorrect readings. Each time you go to idle it will add some that may not be picked up. Just to many variables

 

[Scott Danforth]

The best place for bungs are in the elbows (to read entire bank) however its way to close to the water discharge for O2 sensor longevity, especially at low rpms. So i read plugs. And yes, 1/2 throttle for 2 minutes, then key off, read plugs. Then again at 3/4 throttle and again at WOT.

 

[AKJohne]

MBT advance can add 10-15 degrees to the advance to the CURVE, not the base timing, the base timing PLUS the curve. Given that, on a good day, you could be getting a TA of 45 degrees... If the fuel quality and engine load allow it...

You really what to mess with that sort of engineering excellence?

Chris............

Thanks Chris, I have read this as well, however it states
"Within this range, the ignition module can add approximately 10-15 degrees of spark advance to the base spark timing curve."

Also the
"Acceleration Spark Advance This feature is active during acceleration only. When accelerating, the ignition module may add more spark advance to the “Base Spark Timing Curve”. The amount of spark advance added, is totally dependant on how fast RPM increases (how fast the throttle is moved). This feature is also active within a certain RPM range. This range may be slightly different from one engine model to another. The approximate RPM range for this feature is 1200-4000 RPM. Within this range, the module can add approximately 10 degrees of spark advance to the base spark timing curve"

Seems to me under acceleration you can see +10 over base and when cruising it could be 10-15 over base....

 

[achris]

Thanks Chris, I have read this as well, however it states
"Within this range, the ignition module can add approximately 10-15 degrees of spark advance to the base spark timing curve."

Also the
"Acceleration Spark Advance This feature is active during acceleration only. When accelerating, the ignition module may add more spark advance to the “Base Spark Timing Curve”. The amount of spark advance added, is totally dependant on how fast RPM increases (how fast the throttle is moved). This feature is also active within a certain RPM range. This range may be slightly different from one engine model to another. The approximate RPM range for this feature is 1200-4000 RPM. Within this range, the module can add approximately 10 degrees of spark advance to the base spark timing curve"

Seems to me under acceleration you can see +10 over base and when cruising it could be 10-15 over base....

I see you have read the manual. Excellent. Yet you still want to mess with the base timing... :noidea:

 

[harringtondav]

I think you're as optimized as you're going to get. My little 17' 4.3lx TB4 averaged 4mpg on a 400 mile round trip thru 18 Miss river lockages. Mostly 3300 rpm cruising using only the front two bbls.

I've asked this same crowd of pros about upgrading to TB5. Doubt I'd ever pay for it in gas savings.

 

[AKJohne]

I see you have read the manual. Excellent. Yet you still want to mess with the base timing... :noidea:

I hear ya, I would like to know what TA is, I think its 30 degrees with base at 10, I think 32-34 would be ok for SBC.
I know chey used dished pistons at one time, maybe by 97 that trend was over...

 

[alldodge]

I hear ya, I would like to know what TA is, I think its 30 degrees with base at 10, I think 32-34 would be ok for SBC.
I know chey used dished pistons at one time, maybe by 97 that trend was over...

Depends on what is marked on the module post 2

The module should have something like V8-20 or V8-22 marked on it, this will tell you how much advance and that its for a V8

 

[AKJohne]

Depends on what is marked on the module post 2

I wish it was marked as such, the one I bought is only marked ICM Module 807364-3, it does have some Nippondenso numbers as well and I have searched extensively to identify the advance.