[viking427]

So Im told (reading) the DD 2 strokes should not sit idling more than 5 minutes before fully loading them, or else "wet stacking" occurs - excess injection fuel washes down the cylinders, prematurely wearing the rings, scuffing the cylinder walls & pistons. Resulting in reduced engine life before rebuilds.

Im assuming this is due to the lack of rpm - fuel control in the old style unit injectors. Its also my understanding the fuel modulator feature (option ?) on the Turbo engines is merely a "max" rack shaft rotation limiting device until boost comes on, and does not "reduce" injector fueling at idle rpm.

This being the case, how do ya'll warm up these beast in cold temperatures ? They dont even begin to build enough heat to begin defrosting windshields for 15 minutes idling in the driveway, before its safe to drive away on a warmed engine.

Further more, once the engine is fully warmed, under way and in use throughout the day, its still not advised to idle them more than a few minutes, presumably also because of this excess fueling at idle. Reality is, most folks running these automotive type 2 strokes in their trucks will quite often have their trucks idling for 10-20 minutes or more out of necessity (putzing with trailers, equipment etc.). It would seem to me, there would be hazing or black smoke at idle if there was excess fuel at idle. Was this recommendation just for the industrial single speed engines with larger injectors/timing, or all DD 2 strokes.. Any experiences/comments on this ?

 

[A310]

I've been running my 4-53T daily for three winters. Yes not recommended to idle them, but from time to time I've had to idle mine for 15-20 minutes or so. I plug mine in and run a winter front to help warm up times. I plug in for 30 minutes before I leave in the mornings. I start the engine, wait 30 seconds to get good oil pressure, then drive away slowly. I take it easy for the first 2-3 minutes and then after 5 minutes I drive it like I stole it. As my route starts out flat for 3 minutes, then up an 8-10 % grade the engine is warmed up in 5-7 minutes. The Detroit's run very cold idling and that's the reason for the wet stacking. Combustion temps are not high enough to burn all the fuel, so eventually they slobber and wet stack. I've had zero issues with slobbering or wet stacking. Airbox and exhaust pipe are very dry. I keep it working as best I can and once a month I usually am on a road trip. If you drive them hard they will run well.

 

[viking427]

Interesting. So it's the cooler running combustion chamber temperatures inherent to the DD 2 cycle design ..presumably from ejecting the hot chamber air every two strokes, instead of four.. that causes the residual raw fuel wet stacking. Under this premise, it wouldnt matter how big or small the injectors are (to a point), if peak cylinder temps at idle aren't high enough to ignite the fuel. Theoretically, retarding the injector timing should result in higher chamber temps, correct ? ..and likewise, low port cylinder sleeves should run hotter chamber temps also, all else being equal. A310, if I remember you're running 7A77 injectors and a fuel modulator as well, correct ?

 

[wolf-creek-steve]

I think someone has blown smoke up someone's butt! (It isn't as big a deal as you are suggesting) Back in the day when these engines were being worked on the road, if it was cold and you wanted to sleep in the sleeper, you had to let the engine run to stay even a little bit warm. When my dad had his company truck home over night and it was sub zero, ( no garage, no APU, no plug in heater) he let it run all night. Yeah it wet-stacked, but the other choice was a charcoal fire under the oil pan. What was one to do, put up with wet-stacking or accidentally burn it to the ground?

 

[A310]

Interesting. So it's the cooler running combustion chamber temperatures inherent to the DD 2 cycle design ..presumably from ejecting the hot chamber air every two strokes, instead of four.. that causes the residual raw fuel wet stacking. Under this premise, it wouldnt matter how big or small the injectors are (to a point), if peak cylinder temps at idle aren't high enough to ignite the fuel. Theoretically, retarding the injector timing should result in higher chamber temps, correct ? ..and likewise, low port cylinder sleeves should run hotter chamber temps also, all else being equal. A310, if I remember you're running 7A77 injectors and a fuel modulator as well, correct ?

Yes I run 7A77's at 1.47" timing and the fuel modulator. Retarded injector timing does help for cold starting and warm up. As I plug mime in I didn't think this was necessary. On the topic of wet stacking, all diesels with do this with extended idle periods.

 

[Neodan]

Viking--- As Steve said , you're overthinking the problem, and paying more attention to the naysayers. Did you just acquire a 2 stroke ? Blocking type thermostats help on warming the engine by reducing flow to the radiator and forcing it through the thermostat bypass tube , On the inline engines, the blocking plate looks like an oversized flat washer, and is suspended beneath the bulb on the stat . . These are common in the parts store and available in 180* and 195* . In 38 years with two different 4-53s in my pickup, covering over 300K miles, I haven't had a wet stacking problem

 

[Dougal]

If you can run a block-heater, why wouldn't you?

 

[viking427]

Thanks gents.
Been around DD's for 40+ years, finally getting around to digging into them. Just trying to understand the operational thresholds where the engine only slobbers (as designed) -vs.- wetstacking (not designed) with warmup, and after warmup with extended idling. The engine under consideration wont always have access to 110vac. Glad to hear its not as common as urban myth.

 

[Neodan]

Personally I believe wetstacking is more of a problem when the rings haven't seated yet, like after a fresh overhaul . There's certainly lots of engines that don't slobber, and never did. . If your reference info is gleaned from a pickup conversion owner, it's really hard to put a load on a solo engine . If the person has a trailer to drag and add some loads, then get out and hammer down on an interstate for 500 miles or 1000 miles it may help . Having had a turbo engine in my conversion........with boost guage, it's obvious that 4-5 pounds of boost ain't much load.........when it's capable of 16 PSI .