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Header Install Issue

anupaum

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Back in December I bought a set of Doug Thorley headers for my 2004 Sport Trac. I took them to a custom exhaust shop for installation today, and there's a problem . . .

The stock exhaust manifold has provision for EGR on the driver's side, but the headers do not. Has anyone run into this problem before? Would installing an EGR bung in the exhaust pipe behind the header provide sufficient back pressure for the EGR to function?
 


RonD

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Headers can usually be ordered with or without EGR bung(s), so yes it is fine to pay to have the EGR bung installed.
EGR valve pulls exhaust from pipe when it opens because of engine(intake) vacuum, if running straight pipe, i.e. no Cat or muffler, then EGR flow might be less, but headers wouldn't change "back pressure" much
 

anupaum

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Headers can usually be ordered with or without EGR bung(s), so yes it is fine to pay to have the EGR bung installed.
EGR valve pulls exhaust from pipe when it opens because of engine(intake) vacuum, if running straight pipe, i.e. no Cat or muffler, then EGR flow might be less, but headers wouldn't change "back pressure" much
Yeah, that's what I thought. It doesn't seem like it should be a big deal to weld in an EGR bung right behind the flange where the header bolts into the exhaust pipe. The shop owner was worried that the engine would throw a code and I'd have ongoing trouble.

But as long as the EGR is installed, won't the computer adapt?
 

RonD

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Not sure computer can adjust amount of exhaust in that manner, I believe is has a MAP sensor or similar as part of the EGR system that reads vacuum pressure, but nothing for exhaust pressure.
I don't see an issue though.
 

anupaum

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Not sure computer can adjust amount of exhaust in that manner, I believe is has a MAP sensor or similar as part of the EGR system that reads vacuum pressure, but nothing for exhaust pressure.
I don't see an issue though.
If what you've written is true (and it makes sense, now that I think about it), exhaust pressure ought not enter into the equation. The EGR is essentially a one-way valve that allows some exhaust into the intake manifold. A few inches behind the header should make no difference in its function.
 

simpler=better

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Sounds good to me, as far as I know the EGR pulls whatever it pulls, and then the O2 sensor trims accordingly. Just make sure the EGR bung is welded pre-cat to get any unburned fuel back into the engine.
 

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EGR isn't for unburned fuel.

It also doesn't work on pressure so much as it does vacuum. I imagine that it would be ok.
 

anupaum

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Okay, I had my headers installed this week. The shop drilled a hole in the exhaust pipe about 3 inches back from the collector. Initially, they installed a hose to connect the EGR, but it kinked and threw a code.

After clearing it, they made a few adjustments. Now the modified EGR leaks and my truck sounds like its suffering flatulence . . . (No codes, though!) I'm taking it back on Monday morning. Hopefully they can FIX it this time!

The real difficulty is that there's not very much room to work under there. 4WD complicates everything. I can't even find the spot in the exhaust pipe where the EGR is connected when I crawl under there. It's only accessible when the truck is up on a lift.
 

anupaum

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After fixing the leak on Monday, I have to take the truck to the shop tomorrow again because the problem is back. Ugh!
 

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I was not aware that Doug Thorley made 4.0 SOHC headers. The only ones I knew about were from JBA and cost an arm and a leg. Maybe that's why.
They have different part numbers for left and right side EGR.
 
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anupaum

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I've had the headers on the truck without further issue for several weeks now. They give the machine a nice, mellow sound without being too loud. As far as I'm concerned, they were worth every penny!
 

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