TOPIC: Gadgetguys with gas analyzers - EGR / DPFE test

It's finally spring and I'm getting ready to groove.

TracyG wrote: I just had a look, thanks Again for providing useful valuable reference material Greg! I didn't know the EGR vac. solonoid vented man. vac. to atmosphere, crap, it's a factory installed vac. leak!! It's also very interesting to read that the vac. signal strength is modulated by the solonoid. This of course means the ECU varies the amount of EGR flow, not just on/off. I see a vary obvious way to mod this...

Like this? This has the potential to throw a code:

Connect the manifold vacuum source of the EVR Solenoid to the downstream side of the DPFE sensor. ECU will (probably) see greater than expected pressure differential and command the EGR "to close" (or not open/actuate). Easy enough to reverse if there is a code. Might destroy DPFE. You'd know if the EGR valve was open from the vacuum sound at the downstream port of the EGR tube. Upstream would stay in place at the DPFE. Keeps the system dynamic, which the ECU might need.

If this is successful and doesn't throw a code, the downstream tube on the EGR tube would need to be capped.

another resurrection, based on chasing the highest manifold vacuum possible at all times:

I got curious about this again given some recent SUPER low fuel consumption I've been seeing since the weather has gotten summer-like of late. Are these numbers because the intake air is so much warmer than the computer has been used to til now, killing the need for the EGR valve to open, thus preserving manifold vacuum? If so, why, and how to make it happen at all times?

Well, some web searching has yielded a few hints.

"exhaust gas recirculation in an internal combustion engine" in a search engine got a bunch of results that included the Exhaust gas recirculation - Wikipedia on EGR gas that turned the scientific/engineering speak of research papers into more easily understandable language. These papers described that introducing exhaust gasses into the intake does indeed reduce peak combustion temperatures to reduce the production of NOx, but it does so by moderating the speed of combustion of the air/fuel charge, and THAT reduces the "loss of thermal energy to combustion chamber surfaces," which leaves the THERMAL energy of combustion on the power stroke "available for conversion to mechanical work"...which is exactly what we want for maximum efficiency. However, as noted in an earlier post on this thread, it may have some negative aspects. If the block doesn't get warm, the ECT sensor may not see conditions for closed loop operation of the engine, meaning the computer might throw malfunction codes and still dump fuel into the engine, causing mileage to drop; further, you might not be able to get the cabin warm enough in cold weather.

The procedure might be to let the computer continue to moderate the amount of exhaust recirculation, but change the location of where the exhaust gas gets re-introduced into the intake air stream: I'm guessing that place might be between the MAF and the throttle plate rather than inside the intake manifold to maintain manifold vacuum (an EGR re-route - active to passive, like the PCV re-route we already do - rather than full system deletion/defeat), but this may throw an EGR malfunction code if an insufficient quantity of the EGR gasses can pass through the valve with a more passive vacuum. It may possibly be necessary to find a way to restrict the efficiency of the cooling system (a smaller radiator? blocking some surface area of the existing radiator?) so that coolant can get warm enough to trigger closed loop and you can melt the ice on your windows and keep your toes warm in cooler weather.

This could be an advanced or expert level mod because it may require a lot of fabrication to be involved, along with some trial and (hopefully not too much) error. all for how much of a gain in efficiency and reduction in NOx production? No idea...but to take your groove to the next level, this could be something to get serious about.

I would try cutting the output tube from the EGR valve and using the natural gas piping that Dan mentioned earlier in this thread to re-route the metered exhaust to between MAF and throttle plate, and then capping the port to the intake where the factory intended the EGR gasses to go. I can only surmise/hope that by leaving the factory location for where the EGR systems get their supply of gasses (upstream of the upstream O2 sensor) alone, and just turning the system into a passive rather than active one won't cause any O2 sensor malfunction codes...

This would combine warm, moist exhaust gasses with blowby gasses from the PCV system prior to the throttle plate, so I don't know how that would affect the catch-can/air-oil seperator functionality/effectiveness in preventing fouled oil/"milkshake" and engine damage. Maybe TracyG can speculate/enlighten on that.

Greg,

Not sure what you are trying to do but I did read about rerouting EGR gasses to intake.
One thing I did was to take one of my EGR rubber tubes leading into the DPFE and route it to
the intake. Problem is that this will throw a P0401 EGR code so you have to go back to factory settings/rigging a week before inspection to allow ECU to clear the code naturally.

My idea was to put a plate over the manifold inlet where EGR gasses go into the intake manifold (to preserve or further enhance intake vacuum), then re-route the gasses - still under computer control - back to the passive side of the intake, possibly along with the blow by from our re-routed PCV.

Does that make sense? exhaust heat would possibly help keep whatever gas vapour is floating around in these gasses, both evacuated exhaust and blowby, in the vapour state it needs to be in to burn.

In your case Karl, from what I'm inferring from this comment, you're running with a CEL all the time except when you Undo your modification for state inspection. There's a method to defeating the DPFE in your case so that the EGR stays closed and codes aren't thrown...and I'm not sure if you're applying it correctly. That would definitely improve your mileage, Karl, getting rid of that light...if you're still having troubles.

I'm trying to remember your EGR setup for that truck...if it's like the Ford V6 engine I had, the tube that comes off the exhaust manifold and goes to the EGR valve has 2 smaller tubes off of it with hoses that attach to the DPFE, one closer to the exhaust manifold (upstream), the other closer to EGR valve (downstream). If memory serves, you pull the downstream one off the DPFE sensor and T-connect it into the PCV reroute. The DPFE needs to see the pressure pulses from the exhaust so it doesn't throw a code, and the exhaust itself can go to the passive side of the intake, and the sensor can be left to reference atmospheric pressure rather than occasional manifold vacuum.

I'd have to check my thinking on that to be sure, but that seems to be what my memory is telling me right now.

Why don't you give that method a try (if applicable) and let us know how it works out for you?

If it does, you just stick a hose on the sensor that hangs into the engine bay somewhere an inspector can't eyeball it easily and leave it year round. They'd have to be particularly sharp to catch it, since there would be 2 hoses on the EGR orifice tube and 2 on the sensor...and gubmint inspectors don't always bring their A Game. Especially if the CEL light is off, right??

ok, I've pondered on this, and I think I'm on the right track in this case. the outlets off the EGR tube itself are situated on either side of an orifice blockage in the tube itself. the downstream side sees slight/variable intake manifold vacuum when the EGR valve is commanded to open, presumably by the DPFE sensor seeing increased exhaust stream pressures from the upstream side, and possibly keeps the EGR open (or varies the degree it opens, which introduces a vacuum leak and in our case, messes with the waveform created by the groove) until it sees an "equilibrium" between intake manifold vacuum and exhaust pulsations (or maybe volume of gas? more hot exhaust gas means higher pressure AT THE SENSOR.

with the re-route I propose above in this post, the exhaust would continuously go to the intake manifold, but in a passive way, mixing with blowby from our PCV re-route and going back into the intake airstream to get re-burned, or have another kick at the combustion can. more complete combustion of fuels and gasses, at any rate, which should be ideal for emissions and economy.

forgive my rambles, if I did...it's been a long day.

Hello TracyG need to watch out using those drip water valves, I have been using them on my garden for several years they will brake any time. Have been replacing them as many as 5 times in summer. If you can find a metal valve it would be much better.
geraldc

hi Gerald!

Well the only place I have one of those plastic black irrigation valves is in the vacuum tubing hose between the dist. cap and the Venturi vac. port on the Weber carb. I thought it might be useful to regulate the airflow in the Ozone Cap setup. IT's in an undisturbed location, and has lasted for years w/ no trouble. There are small brass needle valves out there, I have some of 'em, but they are big, expensive and heavy compared to the drip irrigation one. But thanks for pointing that out!

Tracy G