High EGT on 6BT's

[Carl]

Boat runs great, low back pressure with new risers and full 5" exhaust in place. With new to me 3 blade 20 x 21 I see 2650+ on the tachs...very good to me as they are rated to hit 2600rpm at WOT. Motor temps good, then I look at the Pyrometers...Starboard goes up to 700F at WOT and that's great...the port, however, will see 950F at WOT, I have to back her down to 2100-2150 to see the max recommended EGT of 850.

From what I have read I could decrease the motor load by depitching the wheels...but as she turns up past rated WOT I believe that would only be a workaround, besides the other motors EGT is perfect.

I have read it could be too much fuel...but there is no smoke whatsoever at any rpm...not even a haze.
I think I got it right in my thinking that diesel is the exact opposite of gas where IF a diesel gets too much fuel/not enough air it runs hot. Where lean on a gas motor makes it run hot.

SO Maybe not enough air??? Perhaps the turbo is not spooling up is my next thought. But I'd have thought I'd see black smoke or not see WOT or some lag getting up to rated rpm...but she pops right up there.
IF I didn't have pyrometers I'd think I was set with motors running perfectly dialed in. But that is not the case. A friend found a plug I can remove to hook up Boost gauges and compare. He's leaning more to the injection pump...but again no issues with power OR smoke.

So I'll hook up the boost gauges as my next step...but while I do that I'd like to hear ideas of those of you that know this stuff as I am a diesel newbie.

What am I missing that can cause the EGT to run hot on one side.

[1962 31]

maybe check inj pump timing i can send you the procedure if need be

[Carl]

Tom,
Yes, it was the injection pump timing he mentioned.
Is it the procedure in the manual? if so I think I have. I was reluctant to go that direction as she starts and runs awesome with no smoke...but that nagging too hot exhaust.

I think it may be the motor that had the pump was rebuilt before I bought them...supposedly a top-notch shop so didn't want to touch. But top-notch or not it still depends on who does the touching. Maybe they didn't get it quite right. Thanks for the input.

[Bruce]

Are you running one egt probe in the outlet, cause running rich can create burn in the manifold raising temps but cyl temps can be good. What about a faulty probe?

Did you try under load taking heat readings off each cylinder to see if they are with in range?

[scenarioL113]

Carl, you have CAV pumps and they are timed specifically to an individual engine. A mark on the timing cover is where its original CAV pump is supposed to be. If the pump is new or just a different than the original one equipped then the mark can be off slightly I believe.

1mm of movement of the timing mark (on the timing cover and the pump) is equal to 1 degree of timing. If you CAV pump was rebuilt or changed and the internal timing of it may slightly not correspond with the lines marked on the timing cover.

I believe that it will be close and able to run but to be be precise a tech would have to set up properly.

A few degrees off could give you your EGT discrepancy. Since you have EGT gauges you could play with a bit trial and error. (Thats is what I would do and you can watch the gauges and just revert back to the original line on the pump and cover).


ALSO


Is it possible the propeller is out of whack? or dinged? That could produce more load maybe...

[scenarioL113]

Inside the cav pump with the small side inspection cover removed there are "letters" that line up with a mark when the pump is in the TDC position. That letter needs to match the letter on the plate where your CPL is marked for timing.

DO NOT CONFUSE this with the letter on the timing gear. That is a different letter for timing and has nothing to do with the IP.

You do not need to do this IMO. If you ever did open that inspection cover on the side just be advised the pump is full of diesel and will make a mess...

[scenarioL113]

One last note on timing the pump. My engines are 32 years old and so are the pumps. They have been rebuilt a few times and to be honest I dont know if they are original or not to my specific engines. I think they are tho but it dont matter at this point.

I know on older gas engines (in my boats) we would power time them and would set them to where they performed the best. In other words leave the distributer loose and adjust while cruising. I would watch my flo-scans and rpms and when I felt they were in the sweetspot I was good to go and locked it down. That worked for me and never had a problem...maybe lucky maybe not IDK but it worked.

Similarly, last year I felt my port engine was not running right after a major rebuild. Long Story short there was a 2nd timing mark on the cover (from a previous owner) that was uncovered when I cleaned the paint off. I had set it to the wrong mark. Then I ended up getting the pump rebuilt and the original mark did not seem perfect either. I played with it and am prob 1mm to 1.5mm off the mark and found the sweetspot where it needed to be.

Remember being able to monitor your systems will be key for you to play around with the proper dialed in timing. This is where your pyro gauge will prob be useful to ensure you are not off too much on the timing.

I am not suggesting that you IP is the prob or its timing (it could be) but just just sharing my thoughts and it is another avenue to look into for troubleshooting

[Carl]

Bruce,
Yes one probe right after the turbo in each motor. I believe I already swapped the wires and probes...but that was last year and maybe confusing with the motor temps issue I was having. I'll swap them on my next run.

I did not check and compare cylinder temps...its is something I can look at on my next run as well.
Are you saying I could be running rich, but fuel is burning in the manifold with no smoke or soot telltale sign??



Frank-

One pump was pulled and rebuilt, not sure if I can find out which at this point. From what you said, it may have just been installed, lined up to mark, ran on a crate and called it a day. No fine tuning involved. Then again technicians today have a title and not always the skill to back the title.

I'll have to take a closer look at the pump and mark...

Yes, I've done the gas motor give the distributor a tweak and see. But that was more out of desperation and I'd rather not "play" with these motors.

[scenarioL113]

I will add that a very little bit makes a big difference with the CAV pump setting when you move the pump on either side of the mark

[Carl]

Alrighty then….


I check cylinder temps and all seem pretty close

I swapped gauges and starboard temp is high on both gauges




Then played with timing of injection pump. First I rotated pump CCW and took for a ride. I noticed a difference.. not huge but a difference so adjusted further.. not much better so went the other way. Motor sounded a bit wonky so went back the other way again,than again, then one more time.


What I have now is I can run up to 2k and motor is MUCh cooler.
At 2100 it’s about 800°
2200 I’m hitting my max temp of 850°

2300 I’m at 875° Too hot.


So I backed off throttles and she ran good at 2200, I’m up about 150rpm. I decided to leave there for a bit.

I may revisit…till then I’ll check boost


All in all better,but not great.

[scenarioL113]

Carl, post this on sbmar Cummins forum.

Tony Athens will def help you on this. Especially since you have all the gauges to monitor the systems and can report them on the forum it will be easier for experts to narrow down the problem.

FV

[Carl]

Thank you, Frank. I'll do that soon as I hook up some boost gages to the motors.
I have been searching and reading up on high EGT in 6bt's, his site always seems to pops up. From the posts I've read, the boost pressure is the first thing Tony wants to know.

[scenarioL113]

Turbo engines are a little funny (Not literally) when something is just slightly not right sometimes. For example a small leak in the charged air side of the engine can cause all kinds of power loss and increases in EGT.
I once had one blow off on my Excursion when I was towing a car years ago, when it happened I thought I blew a headgasket and my EGTs went thru the roof and power was gone...I immediately pulled over and for about 2 minutes I was 100% sure I blew the top end or headgasket or something... all it was was the hose that comes off the intercooler. Cleaned it off and reclamped and all was good.
Had a similar issue on a Mack Midliner I used to drive part-time and the noise was scary that it would make.

In that case all was fine until it started boosting. The clamp on the hose was bad but if the truck was not loaded it would not leak but once you loaded it up and it would boost it would leak.

I do not think this is your problem but I am just giving you an idea on how critical the turbo and charged air side of the engine can affect the proper operation. A very slight leak on the otherhand can cause issues too that may not be as noticeable unless you have gauges to monitor the various systems.

I think something (obviously) is causing a very SMALL extra load on your engine. You will get to the bottom of it for sure. It is mechanical and can always be fixed. Your numbers dont seem to be excessively bad but I know you want them to be 100% equal ( I would too).

I drive my Excursion every day and have an EGT gauge on it. The most slightest things can make big jumps in the EGT. Mostly from what I have noticed is from load. A car or vehicle is different than a boat when it come to loading tho.
A boat is always loaded (we all know this) and always traveling uphill (we all know this too). Now you factor in something that is slightly off (dirty air filter or insufficient air entering the engine compartment) can cause an increase in EGT.

I know you already stated that the exhaust does not smoke at all but I would still check these:

Are your engine boxes equally vented for outside air to enter them?
Did you "swap" air filters to see if possibly one is restricting some air?

A dinged prop could cause a slight EGT increase
A prop that has some stuff wound up on it (this would most likely cause some smoke tho but maybe not if it is slight).

Just some more things to troubleshoot because I know it is hard to think straight when you know everything should be working fine but its not...(not that you are off that much BUT you are a machinist so things have to be perfect for you...haha)

Imo from your description of the issue I think you would be fine all day long to run it as it sits. Most people dont have EGT gauges and you have ZERO symptoms of any loading problems...ZERO! Only a gauge that is giving you a reading.
Your engines turn up to the proper RPM that shows you are NOT overloaded.
This a is more just trying to get it perfect so that EGT gauge does not annoy you.

Keep us posted and I will follow your thread on sbmar Cummins section and see what Tony or Rob has to say