Pros and Cons of Blocking EGR

Apologies for the immediate topic drift, but: how many miles on yours, and have you done any cleaning?

 

There might be some "pros" and "cons" to discuss, but to get first things out of the way, that video linked in #1 is so completely shot through with misinfo it is no place to start. I don't know who "Auto Info Group" is and haven't looked at what other topics they might have videos on, but it appears they are posting nonsense to get per-click ad revenue.

The misinfo starts at fourteen seconds in, "As the function of EGR is to reduce engine efficiency for emission standards, ...". That's already false before the first comma. The EGR system in the Prius, and in spark-ignited (SI) gasoline engines generally, increases engine efficiency, as well as reducing emissions. The several ways the efficiency is increased have already been discussed in numerous EGR threads here on PriusChat.

It's possible the video makers were thinking of diesel engines. The video does mention DPF (diesel particulate filter) at 1:49. If they were thinking of diesels, that could excuse some of the misinfo in the video. Some of the ways EGR improves efficiency in SI gasoline engines do not apply in diesels, so the first EGR systems in diesels really did reduce efficiency in trade for emissions improvements. Accordingly, "EGR deletes" as a thing originated in the diesel community. People who carry it over blindly to SI gasoline engines are imitating the diesel crowd without understanding that the engines work in very different ways and that changes how the engine efficiency is affected.

Because the claim at 0:14 is already false, those at 0:31, 0:42, 1:20, 1:28, 2:15, and 2:48 are also false.

What it says about carbon soot is one of the few true things in the video. Our EGR systems do get sooty.

It is also true that a Prius will eventually detect blocked EGR, and once it does, it will take protective measures that dial back engine efficiency to protect the engine from damage.

Certain ways of doing an "EGR delete" will be detected immediately (P0403 code), and so the engine will protect itself immediately. Other ways of doing it will not produce the immediate P0403. They will produce an eventual P0401, but only when the ECM has had time to test the EGR flow twice in a row and see that it is blocked. The engine will be run with dialed-back, protective measures after that, but will be at increased risk of engine damage from detonation until then.

In general, the video doesn't seem like something made by some folks who forgot they were thinking of diesels and made honest mistakes. There's just way too much BS in it, making it seem more like something just deliberately constructed to drive clicks and ad revenue.

 

Erm, well. the goal of "reducing emissions part is right, I'm not so sure about increasing efficiency in any engine though, spark-ignited or not. Sure, recirculating some of the unburned fuel in exhaust gases works perfectly, in theory. That and PCV systems do reduce pollutants by burning what would otherwise be vented so I wouldn't remove/disable them for a daily driver on those grounds, but. Memory says about 10% of exhaust is not burned completely, sound right to you? That EGR valve doesn't know which which part is completely burned and which is unburned though, so Law of Averages says the recirculated part is about 90% completely burned, which means reduced combustion chamber temps and reduced NOx so we're still dealing with reduced pollutants. But on the efficiency front? All you're really doing is reducing the available O2 to the combustion chamber which means less fuel and less power.

But okay, prove the point. NASCAR and quarter mile is all about increased efficiency as expressed by beating the other cars around the lap and faster pass times, show me functional EGR and PCV systems on those engines.
<grinning and running away...>

 

If you're not sure, there are plenty of sources you can learn from, including threads here on PriusChat that had hashed over the details long before this one was posted.