Wetstacking.....is this a thing?
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Wetstacking.....is this a thing?
So I was told that letting your diesel truck idle for long periods of time is bad without a high ilde. That the unburned fuel will leak into the oil. Is this true?
Is a high idle setting needed. I have a 02 7.3 psd.
Is a high idle setting needed. I have a 02 7.3 psd.
Hotshot
Joined: Nov 2006
Posts: 11,286
Likes: 263
From: North of Greenville
It is true, but I don't know how significant the problem is with our 7.3's. The general recommendation I've seen is that "extended idling" should be kept at about 1100-1200 rpm. I can't give you a specific time duration for what is considered "extended idling", but given the common sense observation I have from just driving around town, I would think anything over about 5 minutes should suggest the need for a high idle condition.
I will also say that most chip programmers will offer a high idle tune to address this, and there are also some Auxiliary Idle Controllers (AIC) available as aftermarket add-ons (https://puredieselpower.com/ford/dfu...oller-aic.html).
Now, with the 6.4's, it can be a particularly nasty thing because of how the regen cycle can push extra fuel past the rings if the regen takes place during idle conditions. Ford came up with a program update to discontinue idle regens, but I'm not sure how effective that solution was nor if everyone even got the update. Lots of the 6.4 owners in '08 actually had problems with their fuel sump level INCREASING due to the extra fuel wash from idle regens, and I believe there were a number of engine losses due to the loss of lubrication because of excess fuel in the oil. BUT... that was the 6.4's.
I will also say that most chip programmers will offer a high idle tune to address this, and there are also some Auxiliary Idle Controllers (AIC) available as aftermarket add-ons (https://puredieselpower.com/ford/dfu...oller-aic.html).
Now, with the 6.4's, it can be a particularly nasty thing because of how the regen cycle can push extra fuel past the rings if the regen takes place during idle conditions. Ford came up with a program update to discontinue idle regens, but I'm not sure how effective that solution was nor if everyone even got the update. Lots of the 6.4 owners in '08 actually had problems with their fuel sump level INCREASING due to the extra fuel wash from idle regens, and I believe there were a number of engine losses due to the loss of lubrication because of excess fuel in the oil. BUT... that was the 6.4's.
Lead Driver
Joined: Jun 2003
Posts: 8,298
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From: Damon (South East Texas)
Do you have a pyrometer to measure EGTs? Unless you are seeing idle temps below 350-400* for extended periods, you should be alight. I had the high idle feature and used it occasionally, even in the Texas climate during the winter months. I also like to monitor the EGT to let the temp cool sufficiently before shut down.
Tuned
Joined: Feb 2005
Posts: 478
Likes: 10
From: Minnesota
I know idleing was considered bad in the 6.0s and the 6.4s to the extent that many people check the engine hours to miles ratio and make sure the truck averaged at least 40mph through its life. But I don't think it's as big of a problem in the 7.3, or we don't worry because there is no way to check running hours.
I know idleing is not desirable on any engine. But I don't think there should ever be unburnt liquid fuel left in the cylinder to leak into the oil. I would think you'd have oddles of black smoke out the tail pipe before you'd be leaving anything behind.
On a side note it's really hard on the stock 6.4s because it forces them to Regen often. And it's double hard if they Regen while sitting still, and can cause unburnt fuel to slip past the rings into the oil. That's probably where this idea started.
I know idleing is not desirable on any engine. But I don't think there should ever be unburnt liquid fuel left in the cylinder to leak into the oil. I would think you'd have oddles of black smoke out the tail pipe before you'd be leaving anything behind.
On a side note it's really hard on the stock 6.4s because it forces them to Regen often. And it's double hard if they Regen while sitting still, and can cause unburnt fuel to slip past the rings into the oil. That's probably where this idea started.
Hotshot
Joined: Nov 2006
Posts: 11,286
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From: North of Greenville
From what I understand, the entire wet stacking issue is one of combustion temperature, but since we do not have a way to monitor actual combustion temps, the EGT is the next best thing for a surrogate measurement point because it can be more closely correlated to the combustion temps than any other measurement point we have (i.e. EOT, coolant temp, etc.).
Fleet Mechanic
Joined: Aug 2006
Posts: 1,465
Likes: 17
From: Jacksonville, FL
The main reason, as I understand it, was more of an issue with the 6.0 and on engines isn't really due to wetstacking in itself more the havoc idling plays with emissions equipment, EGR's and DPF's.
Sure wetstacking can be an issue on any diesel, especially in lower ambient temperatures, but from what I have seen and read the 7.3's aren't too bad idling for long periods (I have some CAT C32's that wetstack even when loaded, which CAT themselves can't figure out, so it can be engine specific).
If you're going to idling for several hours it may be wise to high idle, but for shorter periods I wouldn't worry about it. I idle for minutes, sometimes over an hour in traffic at times and have yet to see an issue with fuel dilution from any oil reports I have sent in.
Sure wetstacking can be an issue on any diesel, especially in lower ambient temperatures, but from what I have seen and read the 7.3's aren't too bad idling for long periods (I have some CAT C32's that wetstack even when loaded, which CAT themselves can't figure out, so it can be engine specific).
If you're going to idling for several hours it may be wise to high idle, but for shorter periods I wouldn't worry about it. I idle for minutes, sometimes over an hour in traffic at times and have yet to see an issue with fuel dilution from any oil reports I have sent in.
Hotshot
Joined: Nov 2006
Posts: 11,286
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From: North of Greenville
From what I've read, wetstacking did not become an issue of potential concern just because of the '08's, as it existed well before that time frame because I recall reading in my first year or two of ownership ('06-'07) about high idle controllers for our 7.3's to help prevent the issue. I just never have been in much of a situation where it could have applicability for me except for the one day it took 6 hours of mainly idling for me to travel just 45 miles to get home in a freezing slushy nightmare of traffic.
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Lead Driver
Joined: Sep 2010
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From the numbers that mueckster posted, my ride runs cold then. Even in dead heat of summer, my truck idles around 125*-150*. After a good run, the temps drop to that , Purdy quickly
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Logistics Pro
Joined: Oct 2011
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From: Mcdonough, GA
Where is your EGT probe screwed in?
Elder User
Joined: Sep 2011
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From: Vancouver
I used to service diesel generators. I advised my customers to not "test" their generators unloaded. Both Cat and Cummins recommended against unloaded generators. I don't know if pickups are different that way. It would seem that more soot would be produced at idle from low temp running.
Lead Driver
Joined: Jun 2003
Posts: 8,298
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From: Damon (South East Texas)
My probe was installed in the left up pipe just after the manifold. I can't say that the readings may not be a little off, as well.
Logistics Pro
Joined: Oct 2011
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From: Mcdonough, GA
So i kept forgetting to look at egt with truck warmed up. Got a chance tonight to look at it. Engine at operating temp, 50 degrees outside, egt 200. Temp sensor in left manifold before the up pipe connection.