Expected mpg improvement from EGR etc cleaning?

Ummm... yeah, The converter converts raw exhaust mixture to a closer approximation of the composition it would've theoretically had with stoichiometrically perfect combustion. Fewer nasties, just carbon dioxide, water, and nitrogen. I'd suppose the cleaner, simpler mixture would be easier to manage as an EGR source.

 

Different, anyway, and for anyone curious about different how, the aforementioned papers exist.

 

If the cars computers just analyze overall EGR flow, and by this time cyl one EGR flow has pretty much stopped, then cyl one has more oxygen than the computers anticipate, and will be running lean and hot?

 

The risk that seems to chiefly concern the engineers, when EGR ratio is lower than intended, is not so much running-lean-and-hot, as detonation.

 

How about ignition advance with egr? Being able to advance more appears to be one of the egr advantages and improve efficiency. At least with turbo but SAE article mentioned atkinsons as well because they are often ”high loaded” as well (not fully understand why). Just thinking that if egr passage clogged and..

 

That's why any time the ECM detects a problem with EGR flow (P0401) or the valve control circuit (P0403) it sets the corresponding code, lights the check-engine light, and dials back to a fail-safe value for ignition advance.

And why you probably don't want to have one cylinder receiving a deficient amount of EGR that the ECM doesn't know about.

 

That one cylinder usually being cylinder one.

 

The "high loaded" comment may have to do with the fact that Prii engines spend most of their time operating with lowish manifold vacuum, even at times when power demand is fairly low. In other words, by slowing down the engine (as well as generous EGR, and late closing of intake valves) to limit power, instead of by throttling the intake more. However, Prii engines are not highly loaded, compared to ordinary car engines (much less turbocharged ones!) running at WOT.

Your suggestion about ignition timing was correct.

 

since cylinder 1 is the one losing egr flow and killing these engines is there a way to monitor it since the car has no idea? i see that we keep up with the valve but that's not that helpful.

 

Remove, check and clean the intake manifold at least every 50k miles. Clean or replace the PCV valve while the manifold’s off is good too.

 

Fair enough. Like a timing belt every so often on the old cars. We all just need to learn how to take care of the old stuff and keep it going. A wrench here and there won't hurt. As long as it isn't constant which would get very old. lol
Although, I love to mention the alternative as its the easiest.

 

Yeah intake manifold removal is relatively easy, and you can leave throttle body coolant lines attached.

just did that, and the EGR components, last Thursday IIRC. Kicking myself for forgetting to clean PCV valve while IM off. I’ll get it with spring oil change, from below.

 

It's tight, but I have replaced a Gen 3 pcv valve without removing the intake manifold. IIRC, I had to remove and plug a coolant hose or two.

 

What about the inverter pump????

 

I'll go this route:

from below. With the Spring oil change, with the engine underpanel off, as usual. Unless I snap sooner...

Have managed it before. I started trying from above, just after buttoning up, intake manifold back on, but such a forest of hoses there, complicated some by my OCC plumbing, I could touch it, but couldn't see getting a wrench on it, never mind maneuvering it enough to click the ratchet. I have done it before from below.

Still, very frustrating, 'cus I just had the dang intake manifold off.

I'm very loath to disconnect coolant lines too. I do it for the EGR cooler obviously (last Thursday), but beforehand I drain two quarts of coolant (at rad drain spigot), which leaves the the EGR system high and dry.

A little tip: I pushed a short section of surgical rubber tubing onto the rad drain spigot, to make for more controlled, splashless drain, and then got a notiion: why not leave the tube on permanently:

 

What about it?

 

Replacing it, have you done it, without removing the whole front end and/or inverter?

 

Why? did it fail? Does it throw A CEL failure code like the engine coolant pump does when its about to fail?

 

I don't think there are any codes for when the engine coolant pump is about to fail, only for when it has failed.

The Gen 3 inverter cooling pump is controlled in pretty much the same way and has pretty much an identical set of codes that can be reported. I'm not sure whether everybody gets one of those before getting a P0A93 overheating code though.

 

I haven't yet done a Gen 3 inverter pump. Several Gen 2, which are easy, but not a Gen 3.