AMC Eagle Den Forum
The Mighty 258 => Emissions/Vacuum Systems => Topic started by: Canoe on July 14, 2020, 05:22:44 PM
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My thread about all the different EGR valves and how I can find out the specs for them has disappeared. ???
Due to some rough idle, I took my existing EGR valve off to clean & test it, only to find that the valve port had a piece of pipe stuck in it and which is welded closed. (I have a vague recollection of seeing this before...)
And there's no EGR Exhaust tube. And it's an aftermarket 4.0 exhaust manifold. This is going to be fun to replace...
(and I found the front diff breathing fitting & line hanging free)
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Well that was interesting. Had to re-install the faked EGR valve to be able to drive. With the cleaned surfaces and a new gasket, the engine runs a lot smoother. Still has the regular stumble, but the affect is very subdued, and there's noticeably more power off the line, and smoother throughout. Must have had a leak at the EGR valve gasket.
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Great to hear about the improved driveability. Gotta love those simple fixes!
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While at the junk yard, over the past year+ I've also been looking for donor EGR flex tube I can use to repair my EGR tube and get it back into service. I've not had luck. New donor parts are in the $80 range.
Finally had better search terms on google. That turned up results using the existing end connectors, with the cut tube joined in the middle with:- HVAC natural gas line Corrugated Stainless Steel Tubing (CSST): clamped, welded or compression fittings. Clamps (look like mini exhaust pipe clamps) seem to be regarded as questionable sealing & reliability.
- VHT Silicone (blue silicone?), clamped with a hose clamp (smooth style for longevity).
Cost and availability will likely determine which I try.
Next issue will be figuring out which EGR I should be using. With the 4.0 decked head, headers, high voltage coil, etc., and in particular modified exhaust system, it seems that the stock EGR value being a positive pressure type, is not expected to work properly. Having problems finding working specs of EGR valves.
Hmmm.
Apparently there's also FAC (Flexible Appliance Connector) tubing. May or may not be suitable...
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New EGR tubes are down to about $45 now. Used ones on EvilBay are ~$22.
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New EGR tubes are down to about $45 now. Used ones on EvilBay are ~$22.
Unfortunately, stock intake & 4.0 header -> custom size.
Plus prices in Canada.
Looks like I can get a stainless steel gas line FAC (Flexible Appliance Connector) that will do the job for under $20 CAD, all in.
How long it lasts is another factor... Need to compare wall thickness against getting CSST and connecting to my old connectors.
However, a longer length may offer some EGR cooling benefits. And CSST has larger diameters: for greater area for HX; and, for a given flow, a longer dwell time for HX.
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Looks like I can get a stainless steel gas line FAC (Flexible Appliance Connector) that will do the job for under $20 CAD, all in.
How long it lasts is another factor... Need to compare wall thickness against getting CSST and connecting to my old connectors.
However, a longer length may offer some EGR cooling benefits. And CSST has larger diameters: for greater area for HX; and, for a given flow, a longer dwell time for HX.
- FAC has a somewhat thinner wall than CSST.
- FAC is more flexible, presumably more vulnerable to vibration fatigue.
- FAC is supposed to be a one-time use: if you change an appliance, you should use a new FAC.
- For the examples I've seen online where they're using FAC or CSST for EGR tubing, I've not seen anyone report back on longevity.
Another odd observation: where I've found online diagrams or forums discussing an EGR cooler, the coolers are all water (coolant) cooled (Air-to-liquid HX), AND, the flow is Parallel-Flow, not Counter-Flow (which for a given size and flow rate, has the most heat energy is transferred due to delta-T). I suspect they're using water cooled as they'll get consistent results, whereas using air cooling, the air temperature varies with day/night, season and climate. No idea why Parallel instead of Counter-Flow.
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Probably not helpful, but for what its worth, one of the first things I did to my eagle was remove the EGR and bolt a block off plate to it, and its never once given me any trouble, and also doesnt soot up my intake every 20k miles.
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... remove the EGR and bolt a block off plate to it, and its never once given me any trouble, and also doesnt soot up my intake every 20k miles.
With finding the garage installing the engine (fixed/updated after the head & a piston blew up), had not installed the EGR tube and had sealed the EGR valve closed, it's effectively a delete.
I've never had an issue with a clogged intake. Perhaps that's not an issue when the engine is running well, or depends on what the components and additives are in the gas in different regions.
I want the EGR function back, to knock the toxic NOx emissions down, while getting the benefit of improved gas mileage. It's also illegal here to delete EGR.
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Two things...
I now remember the garage telling me of the difficulty with getting a custom EGR tube. They suggested installing the engine without a tube and block the valve, so I could get on my way. I was to fix that later. Which I completely forgot... So my bad. :banghead:
Apparently using air to cool the EGR gas, when that air can be < -30 C (-22 F) (and sometimes below -40 C (-40 F), even below -45 (-49 F), at some places I go a little north of here and up in altitude), may result in over-cooled EGR gas for mixing with the carb mixture, in conflict with the coolant-heated intake manifold.
- Below an air temperature, EGR usually is shut off. Perhaps that's not a big issue.
- Or perhaps using a coolant-cooled EGR cooler means the engine can use EGR gas over a greater ambient temperature range.
- Need to get more info before I can decide if I want to go beyond a simple EGR tube closest to the stock size.
- And, apparently a coolant-based EGR cooler results in faster engine warm up (and the sooner one has a warm heater core for heated air in the interior - bonus in winter). I've no idea if that change in warm-up time is significant. May need an upgraded rad! lol
(Self-inflicted can of worms...)
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The blue silicone with the orange lining is called VMQ silicone. It's tough stuff, and it's the only thing that holds up in those old AIR systems where there are rubber tubes hooked right up to the side of the catalytic converter (like would be in an 85 Camaro). Good luck finding some though. "Secondary air injection silicone hose" got one hit on the stuff through Google on an aircraft website at $6/ft for 3/4". Also I'm not sure what the ends look like, but a mobile HVAC guy has tools to bend and flare up custom pipes usually up to 1" diameter. He might even know where to get new tube nuts if it's that style.
As a side note, carbon in the EGR can only mean one of two things: a very rich fuel mixture, or it's burning oil. If there is any oil in your PCV hoses, 'there's your problem' as they say.
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Torn between a junk-yard diesel EGR cooler 'cause they're stainless steel (and efficient),
vs. a DIY cooler for a double-walled design (can't flood coolant into the EGR valve and hydro-lock the engine).
- Would use CSST for an EGR tube, with one or two (three?) loops forward from the header before going into the bottom of the intake manifold for the EGR.
- A coolant line, plumbed in parallel to the intake manifold, would have a hose or pipe wrap around the CSST EGR tube.
- An insulation wrap around their wrap.
- The resulting HX could be parallel-flow or counter-flow.
I don't know what material for the coolant line wrap is best. Could be a narrower CSST, FAC, heater hose (but would it take the EGR gas heat from the header... what will take the heat yet transfer heat instead of insulate), and vibration abrasion concerns. What's the failure mode...
Amazing the extra interest I found once I realized I could be warm in winter faster...