3126 smoke

Overloaded: Lets just say your cruising along at 2100 -2300. Engines running great, no smoke and life is good. You hit the throttles to full, injectors deliver full fuel and you get some smoke until the turbo's spool up. Your now at 2400 or so, turbo's up at max boost, engines in a deep lug condition and overloaded as you accelerate to rated rpm where the fuel rate backs off to hold the rpms at 2800. Under these conditions, would it be considered normal for you big boat 3126 guys to see the smoke Dagoby is referring to?
 
Last edited:
OK. My GPS is on the boat. I'm going to try and fix my tachs. I will report exact speed and RPMs this weekend.
 
Great. Maybe try this while your out. At wot, feather back the throttle on one engine to make her sister work. Look at smoke and tach. Try to get a feel for the power and quality of burn out of each...
 
BonBini said:
Overloaded: Lets just say your cruising along at 2100 -2300. Engines running great, no smoke and life is good. You hit the throttles to full, injectors deliver full fuel and you get some smoke until the turbo's spool up. Your now at 2400 or so, turbo's up at max boost, engines in a deep lug condition and overloaded as you accelerate to rated rpm where the fuel rate backs off to hold the rpms at 2800. Under these conditions, would it be considered normal for you big boat 3126 guys to see the smoke Dagoby is referring to?
Click to expand...


Pretty sure the turbo's are already spooled at 2100-2300 RPM
 
ImpulseIII said:
Pretty sure the turbo's are already spooled at 2100-2300 RPM
Click to expand...

Let me rephrase: The turbo directly responds to exhaust pressure/flow. With governor control set at 2100, loaded and pulling say 200 horse out of engine. The turbo is responding to the engine burning say 20 gph.... Now move the throttle lever to full, say 30 gph is now deliver to the engine instantly. More fire, more exhaust volume through the turbo. The turbo takes some time to react and spin up faster to deliver more air.

The turbo is an air pump. It's output is measured in boost pressure. With a governor set at 2100, rpms stable at 2100, no load on engine, boost pressure may only be 3 psi. Put a 100 KW load on the engine and the governor responds by delivering more fuel to burn to maintain the 2100 rpms. The turbo responds to the increase in exhaust flow by spinning faster, hence pumping more air, boost pressure now may be 12psi.
 
BonBini said:
Let me rephrase: The turbo directly responds to exhaust pressure/flow. With governor control set at 2100, loaded and pulling say 200 horse out of engine. The turbo is responding to the engine burning say 20 gph.... Now move the throttle lever to full, say 30 gph is now deliver to the engine instantly. More fire, more exhaust volume through the turbo. The turbo takes some time to react and spin up faster to deliver more air.

The turbo is an air pump. It's output is measured in boost pressure. With a governor set at 2100, rpms stable at 2100, no load on engine, boost pressure may only be 3 psi. Put a 100 KW load on the engine and the governor responds by delivering more fuel to burn to maintain the 2100 rpms. The turbo responds to the increase in exhaust flow by spinning faster, hence pumping more air, boost pressure now may be 12psi.
Click to expand...

At a given RPM, isn't the amount of exhaust gas flowing to the turbo the same regardless of the amount of fuel being burned?
 
Last edited:
The only time I see smoke is right at 2000 rpms just before I climb on plane and if I'm moving the throttles moderately fast. As soon as I transition to plane, the smoke goes away, so really it's more like a puff of smoke. I've never looked back when I'm cruising at 2300 rpms and punch the throttles.
 
OK, It’s probably a good time for me to jump in and post what I’m going through now to bring my WOT which presently is only running 2600 back to the 2800 WOT that my 3126TA’s (420 HP version) are supposed to able to reach. We have noticed a little more soot on the starboard transom when cleaning the boat which also shows the boat seems to be running more loaded.
This is the first bigger boat and or diesels that I have had and I certainly didn’t know enough before or since I bought the boat & continue to learn. I went back to my original survey as that is the original written baseline I had from where it was when purchased to date. As is often the case, the memory begins to fade and a written base line is the best way to see where I was.
The survey which was done July 07 with full fuel (350 gallons don’t recall the water or waste level but assume 50%) the boat by the bridge gauges ran Port 2750 & Starboard 2775. The surveyor took them as well from the face of the engine flywheels and at WOT were within a few rpms of the bridge gauges which confirmed the readings gauges were closely representative of actual readings which was a good thing. GPS at readings during the same survey indicated in the ocean of Ft Lauderdale at cruise 2400rpms the boat ran 21knots and at WOT 2800 which we couldn’t actually achieve she’d run 24+.
Over this year’s boating season the boat seems to be slowing down and to the point now about 2600 is about all she wants to turn. We had Cat come in just before our summer vacation run and lash the valves as it was due according to the Engine maintenance schedule. We normally run the engines up to WOT a couple of times during the season for a limited time when headed back to the marina for the last couple of minutes to see if all is ok. While I don’t recall having any problems I can’t remember after the vacation if there were any problems reaching 2750+-. The hull is pressure washed in the spring before we start taking weekend trips and before our summer vacation cruise. Pulled 3 weeks ago to check the bottom and in pretty good condition. Bottom paint on her second year and has been redone this past week.
Pulled the wheels and had them sent off to be tuned/check and gave the prop shop the drop in RPMs to see if maybe we should take a little pitch off and the shop stated they were in great shape. Based on his research he confirmed they are the right props, 22” diameter, four blades Nibal with no pitch change and he stated he wouldn’t recommend any change to the props.
I changed the primary and secondary fuel filters to make sure we aren’t starving the engines for fuel. Running gear & props have had Prop Speed reapplied and plan to splash the boat back in the water tomorrow and see how she runs compared to original survey. Hoping she will turn up to 2750+- and not sure if I really need to achieve the 2800 and if so I assume the prop’s pitch will need to be taken down a little bit.
I talked with Cat and they stated that the turbo’s might need to be service even though we are only in 650 hour range so I’m assuming Monday I will call them to line that up if we don’t see 2750+-. How important is it to fully achieve the 2800 vs. 2750? What steps should I follow from here on out to achieve the 2800 if so needed?

While I know this was long I tried to provide answers to most of the questions up front so you’d have good information to start from.
 
John: I hope the OP don’t mind if we step on his post as long as we keep it short! Step one before you start em up. Check controls for full throttle. Look at the governor control lever on the governor itself and be sure at full throttle it goes all the way, plus breaks over the break over spring and moves about mid way in the slotted window.

A little more soot on the starboard side could mean the engine not getting a good burn due to air or timing.

Is it posible from sea trial of 2750 to now 2600 the Admiral has been slowly loading the boat? How many pillows are on board?
 
Four Suns said:
At a given RPM, isn't the amount of exhaust gas flowing to the turbo the same regardless of the amount of fuel being burned?
Click to expand...

As more fuel is added, more exhaust gas is created via combustion. More ex gas through the turbine spins it faster. More boost pressure is created forcing more air into engine. A 3126; 1.2 liters per hole x 6 = 7.2L... A 7.2L engine at 15 psi (one atmosphere) can produce twice the exhaust volume as a non boosted 7.2L at the same rpm.
 
How does a clogged aftercooler come into play? Would this increase boost pressure? or does it restrict airflow and decrease boost?
 
Turtlesboat said:
How does a clogged aftercooler come into play? Would this increase boost pressure? or does it restrict airflow and decrease boost?
Click to expand...

Gumed up on the air side will restrict flow, just like a restricted air filter on a automotive engine. The pressure differential between in/out will increase as the core fins plug. That’s how you test one. Normally about a 1-2 psi difference will be seen when measured at max boost when all is good. Max boost in boat engines are in the upper rpms, cause there all about making horse power.
 
BonBini said:
Gumed up on the air side will restrict flow, just like a restricted air filter on a automotive engine. The pressure differential between in/out will increase as the core fins plug. That’s how you test one. Normally about a 1-2 psi difference will be seen when measured at max boost when all is good. Max boost in boat engines are in the upper rpms, cause there all about making horse power.
Click to expand...

My 3116's seem to create quite a bit of transom soot. Boat does achieve 3150 RPM with full fuel,half water and usual admiral stuff(digital Aetna tachs).
Would it be prudent to assume the soot issue dictates that the aftercoolers should be cleaned or also do above mentioned differential pressure test to confirm??
If test should be done is that something CAT techs should do or can this be done by any competent diesel shop??
If aftercoolers are restricted is there anyway owners can clean or do they need to be sent out to specialty shop for cleaning??
thanks for any advice...
Tom
 
margarita jane said:
My 3116's seem to create quite a bit of transom soot. Boat does achieve 3150 RPM with full fuel,half water and usual admiral stuff(digital Aetna tachs)....
Tom
Click to expand...

Tom:

Are you sure about those RPMs? 3150 RPMs is the approximate Max Bare Idle speed for the 3116/3126.....In neutral...no load....full throttle.
 
osd9 said:
Tom:

Are you sure about those RPMs? 3150 RPMs is the approximate Max Bare Idle speed for the 3116/3126.....In neutral...no load....full throttle.
Click to expand...

Yes, positive and props are 22x24 which I believe is standard Sea Ray size for the 97 400DA. Max bare idle was checked as well 3150...
 
Something is wrong Tom.....

You have the 800 series Hurth trannies. I'm pretty sure they are the same ratio as my 80 series Hurth trannies. The 400DA and 410DA are near identical in spec. The 3116 and 3126 are also nearly identical.

The 410DA came from the factory with 22X23 4 blade nibral props. At that, I had to cut them down to 22X22 to make rated 2800++ WOT RPMs. If you are in fact making 3150 RPMs with 22X24 props, then I would say that is way off....possibly your tachs.

What RPMs do you cruise at and what is your speed at that cruise RPM?
 
Aftercooler clean required specialised cleaning from a radiator shop,(they boil them up in a special brew- they were filthy) removal was fairly easy, new gaskets, be careful which way round the gaskets are placed or you will have to start again, gained approx 50 rpm. Also check turbo hose from a/c as this may be getting soft. Buy a can of white Cat paint for the a/c.
 
You must log in or register to reply here.

Forum statistics

Threads
113,184
Messages
1,428,135
Members
61,094
Latest member
Linword
Back
Top