Explain HEUI Oil Shear?
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Senior User
Joined: Jun 2008
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From: Western WA
Explain HEUI Oil Shear?
Can someone please explain the HEUI system and how it relates to oil shear?
I also may need some background on how hydraulic electronic unit injection works.
My assumption has been that an electronic device triggers the fuel injectors via a pathway of oil/hydraulic, and the oil actually doing the open/close of the fuel valve. But people also bring up that the HEUI system is really tough on oil from oil shear. So I don't quite understand where the shear is.
Thanks,
Jake
I also may need some background on how hydraulic electronic unit injection works.
My assumption has been that an electronic device triggers the fuel injectors via a pathway of oil/hydraulic, and the oil actually doing the open/close of the fuel valve. But people also bring up that the HEUI system is really tough on oil from oil shear. So I don't quite understand where the shear is.
Thanks,
Jake
Post Fiend
Joined: Mar 2007
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From: Texas
I'll take a stab at this. The shear, as well as importance of anit-foaming agents comes from our HPOP (high pressure oil pump) that takes oil at normal pressure from the regular oil pump or LPOP (low pressure oil pump) and pressurizes it up to 3300 psi to fire the injectors. At 40 or 50 psi in an engine you don't have to worry about shear. At 3300 psi, it makes a difference.
Here's a link that explains the injectors. It has pictures, so it will be easier to understand than anything I type. PowerStroke
Here's a link that explains the injectors. It has pictures, so it will be easier to understand than anything I type. PowerStroke
Post Fiend
Joined: Feb 2006
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From: Middle Tennessee
Not so sure about the shearing as much as the need for an antifoaming oil. Our injectors are fired by High Pressure Oil Pump (HPOP) pressure. There are two rails in the heads that feed the injectors, one fuel and the other oil. The oil is built by the HPOP and fills the rails and injectors. When triggered by the PCM through the IDM, the injector fires a piston using oil pressure to push the fuel, this piston has a ratio that multiplies the existing fuel pressure in the injector and pushes it through the nozzle and into the cylinder.
That is the simplest way I can explain it to get to your answer. Now the answer is that the HPOP pressure varies from about 500psi give or take idling to up to 3000 on a stock truck. On "big oil" modified ones it can easily exceed 3800 in some instances sustained. I don't know how much shearing is taking place there but know that the HPOP could foam up some inferior oil for sure.
There is a lot more technical way to explain the system but I just thought I would simplify to answer the question.
...and now I see before posting another answer is at hand. Do a search if needed.
That is the simplest way I can explain it to get to your answer. Now the answer is that the HPOP pressure varies from about 500psi give or take idling to up to 3000 on a stock truck. On "big oil" modified ones it can easily exceed 3800 in some instances sustained. I don't know how much shearing is taking place there but know that the HPOP could foam up some inferior oil for sure.
There is a lot more technical way to explain the system but I just thought I would simplify to answer the question.
...and now I see before posting another answer is at hand. Do a search if needed.
Post Fiend
Joined: Jun 2004
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From: Parker, CO
Here in an article on oil shearing from BobistheOilGuy: Effects of Shearing
Hopefully now you can see after reading the article, why adding an HPOP to the setup will cause additional shearing. Add 2 HPOP's (like my truck) and even synthetics have a hard time making it to 5000 miles.
Hopefully now you can see after reading the article, why adding an HPOP to the setup will cause additional shearing. Add 2 HPOP's (like my truck) and even synthetics have a hard time making it to 5000 miles.
Lead Driver
Joined: Oct 2004
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From: Columbia, MO
Here in an article on oil shearing from BobistheOilGuy: Effects of Shearing
The radial piston pump that is the HPOP puts a lot of pressure on the molecules of the oil and causes them to shear. It's basically the high pressures between the two metal parts that causes it. Oil under pressure alone will not shear it, but the hard parts that are putting it under pressure will shear the oil in the area where the hard parts are making contact with each other.
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Fleet Owner
Joined: Jun 2004
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From: Rio Rico, AZ.
It's one of the reasons that I change out my oil every 2000 miles using Mobil 1300 Delvac 15-40.
It's not synthetic, but where I live and the frequency of oil changes makes no sense to use a syn.
Frequent oil changes are a LOT less expensive than replacing expensive engine parts due to loss of lubrication!
It's not synthetic, but where I live and the frequency of oil changes makes no sense to use a syn.
Frequent oil changes are a LOT less expensive than replacing expensive engine parts due to loss of lubrication!
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Post Fiend
Joined: Feb 2002
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From: Carhenge
Hey Kwikk did you know Mobil is doing their $3 a gallon rebate on delvac again this month?
http://exxonmobil.cmail4.com/e/525093/61jjdtj4t/
http://exxonmobil.cmail4.com/e/525093/61jjdtj4t/
Post Fiend
Joined: Mar 2007
Posts: 26,966
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From: Texas
Hey Kwikk did you know Mobil is doing their $3 a gallon rebate on delvac again this month?
http://exxonmobil.cmail4.com/e/525093/61jjdtj4t/
http://exxonmobil.cmail4.com/e/525093/61jjdtj4t/
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Hey Kwikk did you know Mobil is doing their $3 a gallon rebate on delvac again this month?
http://exxonmobil.cmail4.com/e/525093/61jjdtj4t/
http://exxonmobil.cmail4.com/e/525093/61jjdtj4t/
I buy oil by the barrel from a wholesaler and don't even know if the rebate applies to that sort of purchase.
FWIW buying oil by the barrel is not any cheaper than buying it by the case and sometimes more expensive.
But not having to manage a half a dumpster full of empty containers that have to be treated as something you cannot just throw in the landfill more than makes up for it.
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Senior User
Joined: Jun 2008
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From: Western WA
Some great info posted! Especially good reading from bobistheoilguy.com. The site gave me a much better understanding of the shear caused by the engine.
However, the HEUI oil shear is something I'm still trying to get my head around. From the sounds of it, the HEUI system places a lot of pressure on the oil. This high pressure is causing the oil viscosity to breakdown more quickly.
Does that sound right?
However, the HEUI oil shear is something I'm still trying to get my head around. From the sounds of it, the HEUI system places a lot of pressure on the oil. This high pressure is causing the oil viscosity to breakdown more quickly.
Does that sound right?
Post Fiend
Joined: Jun 2004
Posts: 9,293
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From: Parker, CO
It's not necessarily the high pressure itself that causes the shear, it's the way the pumps work, like what JTHarvey explained. It's those moving metal parts that cause additional stress to the oil.
Lead Driver
Joined: Oct 2004
Posts: 7,413
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From: Columbia, MO
Yup. It's not the pressure, but the oil being squeezed between the moving metal parts that make that pressure. It's obviously a very thin film that gets squeezed and sheared at one time, but as the miles add up, the more molecules you have that have become sheared until it's to the point that the viscosity suffers.