Power and smoke

[h1x2]

I'm trying to figure out if my truck is working correctly and if there are adjustments for more power.

I've got an M818 250 Cummins. 2006 depot rebuild. Currently has 2500 miles on it. Trucks smokes at idle all the time. White/gray. White smoke on acceleration. Not like coolant smoke though. Seems to have low power and can barely do hills when loaded. I'm just trying to figure out if this is par for the course or if I have an issue. Exhaust smells and kind of burns your eyes if it blows into the cab.

Also, does a turbo make a huge difference?

 

[cx65083]

I'll let others, more knowledgeable address the white smoke at idle and the burning eyes part...but ANY of the 809's with Cummin's 250's are going to be DOGS. You have to be patient going anywhere in these trucks. Being Loaded just makes it work worse. Super singles loaded? Forgetaboutit!
You can turn up the fuel a little as is, but only a bit. Much more than 20-30 hp and she'll get hot and burn pistons. Adding a turbo adds more air into the mix so you can add more fuel. Again, you can only turn it up so far before you have to worry about burning pistons. If your going to turn up the fuel even a bit, adding a Pyrometer is pretty much MANDATORY!
Good Luck.

 

[wreckerman893]

I cut my teeth driving an aged International cabover with a 250 Cummins and a ten speed Roadranger transmission. I pulled a 45 foot drop deck Kentucky furniture van hauling new furniture. It was a poor way to make a living and I cursed every mile I put on that truck. The 250 is a dog and always will be. There is no cheap way to make power. You might as well invest in a 400 and be done with it. It is also and old engine and finding a competent old school mechanic to work on it is hard to do. Parts can be hard to find too as I discovered when the 250 in my M816 ran away and I had made the decision to cut my losses and sell it. White smoke usually means you have bad rings (that would explain the burning eyes) and unburned fuel is coming out of the exhaust. Low mileage on the speedo does not necessarily mean that is the mileage on the engine. The truck could also have suffered abuse somewhere down the line. I have seen GL people jump in a truck, crank it and run it wide open until the air built up. If the truck sat a long time the rings can get stuck and when broken loose can cause damage. Low compression equals low power.

 

[ichudov]

Are you saying that about all Cummins 250 engines in the M939 series prior to -A2s?

 

[cx65083]

We're saying that about ALL 250's! These things have one major design flaw. Cast pistons with NO lower cylinder lube or piston "squirters" to keep the piston skirts happy and cool. That means they have to be run mild to keep them alive. Mild means low HP. Low HP mean dog. I have learn LOTS of patients driving these trucks...and then even more after going with big *** super singles. I hardly ever used 1st gear in traffic before, (with the 11x20's) Now I HAVE TOO. 1-3 in traffic isn't too bad. But once you shift to 4th....break out the calender to measure how long till your next shift! UGH. 0-65mph in several minutes!
Forged pistons and piston squirters would help tremendously! I've heard of someone using a 335 as a swap-in that turned out well. If you go 350 or 400 big cam youre going to suck diesel like it's going out of style and the drive line wont last long under that much Umph!
I sure wish I could put a 10 speed in my 813. that would help a bit, cause 5 just isn't enough!

 

[ichudov]

So, say, if I am driving a truck powered with said engine NTC-250, I just need to make sure that the engine runs at below 2100 RPM and preferably much below? Right?

 

[cx65083]

Below 2100 yes. Much higher and you will break things. But RPM is a tiny part of it, And is control by a governor on the motor anyway. More important is the exhaust temps at the valves! You want to keep them below 1200`F. If you heat the exhaust valves up past that, they tend to melt. This is why I HIGHLY recommend a pyrometer that measures exhaust temps. Keep the R's below 2100 and the temps below 1150` and your motor should live a long happy life. (pending reg. maint.)

 

[ichudov]

OK, what kind of pyrometer would you recommend and where do I put the sensor? thanks

 

[73m819]

Think you will find that you will melt pistons a long time before you melt valves, the problem of over speed is that the valves WILL float and HIT the pistons, this leads to BAD things, CUMMINS calls for 2100 rpm, it is in all there tec sheets,

The trick is to UP fuel for a bit more power, at the same time watching the EXHAUST temps so no piston melt, while doing this keeping the RPMs to close to 2100, Cummins had the 250 (realy a 240) and a smaller short live engine that was a NON squirter engine, When they went to the turbo 290 and up (think there was a short live 265) squirters were used, these are used for piston cooling AND lower skirt lube, Remember Cummins spends close to a million dollars in research before they makes a change, so with that said, if Cummins came to the conclusion the squirters was needed for higher HP engine LONG TERM longevity I would tend to believe them. These 855s are a long time, well thought out , long lasting engine family, that will last about for ever as long as it is kept and maintained in the Cummins PARAMETERS

I dropped my button from 27 to 22 for more fuel in my NON turbo, 36,000 lb m819, I can tell the difference on a long hill pull, also have BLACK smoke, a LOT on the pull, just a bit on normal rolling (like black smoke), I do have to drop from 5th to 4th at times on the pull, not from loss of power but to keep from burning things up.

Put the PYRO. in the exhaust right above the lower bolt flange that the exhaust pipe or muffler bolts to.

"Trucks smokes at idle all the time. White/gray. White smoke on acceleration. Not like coolant smoke though"
Once WARMED there should be NO smoke at idle, sound like a bad cylinder (cold), either from a bad valve or rings, could also be a bad injector (not closing ) , white is fuel, once warm, should have a trace of BLACK on acceleration (more fuel going to the engine than it can use till the engine catches up)

 

[rangereter]

The Power Torque 270 and Formula 290 were/are real strong runners in the small cam family. You might have air entering your fuel feed...try running the engine from a fuel can right into the PT pump and see if your white smoke issue goes away.
Regards, Bob

 

[cx65083]

While I cannot post a link for a particular item in a CURRENT sale (RULES- READ THEM!) I think It's ok to post a link to a ended sale. Autometer makes a nice one that has the right swing (reads 270` easy to see changes) and temp range (0-1600, more than that and you've got a melted pistons anyway!) like this: http://www.ebay.com/itm/141017939854?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 . Comes with the harness and the thermocouple. I'm saving up for one now. But bills come first and I'm not caught up yet.

 

[73m819]

http://hewittindustries.com/pyrometers_2_inches_250_sweep.html

try the above for a nice pyro, gauge even can be had to match and with a RED light for night, and in 24v

 

[h1x2]

Is there a good write up on turning up the fuel a little bit? Think I'm going to order a pyrometer