SCR DEF Freezing Question

What problems does a winter front cause ..?

In my experience the oem engineers blame everything else (but their poor design ) for emission problems .

 

Winter front reduces the effectiveness of the air-to-air cooler, also the outside air temperature sensor may be effected by it making the computer think that it is warmer than it really is.

One trick to help prevent an air dryer from freezing is to shut the truck off at night while the air compressor is still in the middle of building up the air pressure in the tank. Just something I heard a long time ago.

 

Well, true, if one is keeping the winter front on above 20F. But there is more than ample cooling for the CAC when we are talking about sub zero type of temps. Not like we are talking total enclosures here. Seems a bit of stretch to think that the ECM ambient air temp sensor would be negatively affected. The winter front just stops the full flow of the very cold air, but more than ample cold air is getting near any sensor. Proper winter fronts are slotted and allow more than enough cold air thru, and you have cold air coming in thru the underside and the fender area.

I recall some time ago reading a article where some OEM's had determined that USING a winter front also improved the downstream emissions stuff, in that, the exhaust did not cool as quickly and that improved DPF performance. Will have to try and dig that article up. Either way, I am curious why no one considers putting on a secondary DEF tank warmer that could be easily powered by an APU if one has that. Would not be much for wattage to keep a DEF tank and lines from freezing, and it would virtually eliminate the early running issue with DEF on a cold start up.

 

Sounds to me more like the truck was not ordered properly with the arctic package.

 

I saw a guy that wrapped his exhaust from the turbo to 1/2 way up his stacks in an asbestos type wrap and swore that it keep the exhaust from cooling too fast and actually ran the EGT temps about 200° cooler.

If you think about a wood stove and what happens when the flue pipe is cold it makes sense. Claims it moves air faster because you do not have the cool air fighting against the hot air trying to get out.

 

Yeah, My turbo has a blanket on it and the flange pipe wrapped. Been that way for the entire 465,000 miles on the truck. Yes, it does keep the exhaust from cooling too quickly, which also facilitates faster exhaust flow, so the overall EGT's are lower. Even on a hard pull on a grade on a very hot day, EGT's hardly ever go over 900F unless I goof and don't down shift soon enough and RPM's start getting too low.

One benefit that also is realized, is that the blanket on the exhaust side of the turbo prevent radiated heat from affecting the compressor side. Intake air temps are 20F or more cooler than if the blanket wasn't on. So the air is more dense on the compressor / intake side which is a good thing. Though I have a regular turbo, I am convinced that those with VG turbos would benefit greatly from using a turbo blanket. It is on applied to the exhaust side and it would prevent that heat from radiating onto the VG actuator, thereby reducing failure risks. The blanket is effective enough, that you can place your hand on the blanket with the motor running, even after working the truck down the road. I have done it frequently showing others how effective they are. That is a lot of heat that is not being thrown into the engine compartment.

And this all also complements a winter front on the grill when it is sub zero temp. Plenty of cool air circulating around under the hood.

 

Talked to Brenntag today at the Toronto truck show ( Truck World 2016 ) about DEF freezing.
The rep said this fall they will be announcing that new DEF fluid I mentioned in an earlier post that will be rated to -40 degrees before freezing. It will sell at a higher price.