Swapping in a Gen 4 Prius' 2ZR Engine into the Prius v

All I have to go on is the fact that the TSB that directed changing the valve also directed upgrading the firmware in the same TSB. Could they have included two otherwise-unrelated changes, one hardware, one software, in the same TSB, maybe because both changes somehow addressed the cold-start issue in unrelated ways? Possible. I have no way to say yes or no. I don't even have samples of both EGR valves handy to compare.

But there has been talk in this thread of (one wonders where this idea came from) swapping two wires at the valve's electrical connector, so that in itself suggests more difference between valves than one is slipperier or something.

And then there are the reported driveability issues to explain.

I wonder if it could also be possible that the updated firmware did something equivalent to swapping those wires, so you would get different driveability results based on whether or not you swapped them and whether you were running the old or new firmware.

Even if all they changed in the valve was the taper of the pintle or something, that would change how far you would open the valve when intending to get a certain flow. Reading about EGR control algorithms, they are surely computing this according to engine load, sensed MAF, etc., so you would want the ECU to have the right formulas.

Toyota doesn't disclose these details, so of course I am speculating. That's what makes a project like this adventurous.

Wouldn't be their only example of matching firmware to hardware. You get different brake ECU firmware if you have 17" wheels rather than 15".

The chambers are Helmholtz resonators (see on Wikipedia). If you look closely, you can see that the intake air flow does not go through the resonators, it only passes by their openings, the same as when you play a Coke bottle or a flute.

That sets up a resonance inside the chamber that alternately adds to and subtracts from the air pressure in the intake. At key points where the engineers matched that to the engine rpm, the resonance assists charging the cylinders by increasing the intake pressure as the intake valves open. The reflected pressure wave when the valves shut is then canceled by the low-pressure half of the pressure wave in the resonator. The end effect is as if charging through a path of lower air resistance, while also quieting what you hear out the intake end; you can tell it's doing its job when you hear less of a train of pulses from the intake valves, and more of a steady whoosh.

There's a school of thought here that links going EGR-less with engine damage. I haven't seen as much detail as I would like (one question could be, for a short time how bad?), but the school of thought is there.

 

Lotta info there, thanks.

 

If you unplug your EGR by its plug, your issues will go away. Unfortunately your check engine light will go on and stay on the entire time. This will lead to the car not running all emission tests for you to pass smog


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Which issues? The ones caused by too much EGR? Or the ones caused by too little EGR?

 

It'll run hotter, pollute more and get lower mpg?

 

That is correct, you don’t want to go that route in the long run.


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The 4th Gen EGR is the issue. It’s getting too much flow which is causing poor engine performance at idle


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EGR should be off at idle. Does the valve fail to close?

 

I don't believe the valve to be malfunctioning i don't get any error codes for the valve not functioning.

But I am going to unplug it and see what, if anything, happens.

Like it would just be nice to flash Right on time firmware into my car since we are running same hardware...

I put alot of faith into project because of post on here that said they had no issues so must be something I can do.

Maybe put someones gen 3 EGR back which sounds dismal considering what I did to exhaust manifold. Loll

 

Maybe just hook up Techstream, see what valve step it is on at idle. If it isn't 0 or 1, use the active test utility and bump it down some, or up some, see if anything makes it run nicer. Won't be a fix, but could give info on what's what.

 

Unplug it. You will see


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Checked my exu for codes and switching wires cleared all DTC even the permanent one from the insufficient flow is cleared... Too bad my performance is suffering.

Unplugged the EGR got my CEL and the car works fine for the first 5 or so miles at various speeds. That means this EGR is definitely the culprit.

So do I go to Toyota and ask them to update my firmware and hope that is the difference, that I must be running the old gen 3 EGR with old firmware...

Or

Change back to gen 3 EGR that is pre firmware update and hate my life rerouting coolant lines and working on that side of engine.... Sigh

I am honestly thinking those could be the only differences here, barring some sort of grounded out or loose wire.

What do you guys think?

I'm not familiar with techstream

 

Bingo! Unplugging the EGR did the trick! Like I said before the Gen 4 EGR flows much better then the Gen 3.

Thanks for following up with a response



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But where to go now?

 

What happens after that?

It would be easier to say with a better idea what is happening.

There are a bunch of threads here about how to set it up, if you've got a beater Windows laptop and twenty or thirty bucks.

You can do a lot of things with it, such as monitor a lot of engine data items while it is running, and also active tests where you change things, like the EGR setting.

That could let us dig in more to things like:

"Flows better" is always a good thing when you're talking about a prostate, but when it's an EGR valve we would like it to flow when commanded open and not flow when commanded closed, such as at idle.

So it would be interesting to have the Data List up and see what position that valve is being commanded to when that is happening, and what position the ECU thinks it is in. If there is a mismatch, that might lead to learning something about the valve vs. firmware compatibility.

 

The TSB that you stated will address the issue pertaining to a Gen 3 EGR stepper motor/ valve assembly but, Michaud85’s issue doesn’t have that setup. I am not seeing how that would help, with the EGR Valve not being compatible between the two gen’s as they mate differently on the EGR cooler.

You also mentioned swapping the wires as a reason for the issue occurring or not with the updated firmware. The wire swap suggested makes absolutely no sense once you understand basic operation of a stepper motor. All that was doing was stalling out the stepper motor and preventing it from opening and closing correctly.

 

My only optionat this point is to make sure I've got the lastest gen 3 firmware flashed, especially if there was some sort of update in the middle of gen 3 production with EGR valves and firmware.

Not alot about this makes much sense.

Other members, several in fact, have run the same gen3 ecu and firmware with the same gen4 EGR, intake and engine without having these performance issues.

So there is something wrong with my firmware where maybe I just have an older first edition model with a strange firmware flashed or something

Or I have a bad gen 4 EGR with 40k miles on it, I mean the donor car was in an accident on the front end on the driver side of the vehicle so I suppose the egr could have been jostled lol but this seems so unlikely to me.

It's really odd, I don't think I have any grounded or loose wires because the car drove for 3 days and has no trouble codes whatsoever and all systems check clear and ready for state inspection....

So it's a matter of the way the ECU is expecting the engine to behave vs what is actually happening... This becomes clear when the EGR is unplugged and left wide open or closed or in the middle or whatever but we know once it stops talking to the computer performance improves.

I will have to look into tech stream and see what the egr is doing, not really sure what that is going to do for me in the long run unless I have another person's who's running gen4 setup in the gen3 car to run the exact same tests and compare the data with, also it would be helpful to have the same test run on a stock gen3 to see how the data compares.

It makes sense to an extent as well because whoever it was who tried to run gen 4 EGR the first time, essentially disabled their EGR by swapping those purple and red wires but also left it plugged in so it didn't throw an immediate code.

Either way this is not excitement anymore it is just sad.

I was willing to take a risk for the swap, I may be willing to take a risk for the long haul EGR unplug.

A small part of me wants to say this is a bunch of phooey and the car will run just fine no EGR. My gf car is a science experiment at this point anyway.

 

Refresh my memory: you threw away the 3rd gen EGR components?

Barring a revision to the Electronic Control Unit (and that seems a long shot, but you never know), I think it will be the tail that wags the dog, ie: you need to restore the car to 3rd gen EGR. Could the exhaust manifold survive another beating? Maybe.

 

Yeah, having that info might not lead directly to full understanding ... but not having that info will definitely stand in the way.

With no EGR, you can expect the following:

• Decreased fuel economy (from increased pumping losses)
• Increased NOx emissions (maybe you care, maybe you don't)

We know about those because those are the two reasons EGR is put on gasoline engines.

You might also be risking:

• early head gasket damage (?)

There is a PriusChat school of thought making that connection, though it so far appears to be what Wikipedia would call "original research".

One of the claimed mechanisms is increase of combustion temperature damaging the gasket. We do know EGR lowers combustion temperature below the point of forming NOx (after all that's the point), but no one has offered a source for the amount of temperature difference being anything the head gasket would care about.

On the other hand, there are Toyota tech training materials that say the engines can be prone to detonation if the EGR flow is impaired. Detonation usually has a characteristic sound, which can cue you to back off the throttle if you hear it. The engine also has a knock detector and the ECM will automatically back down on some parameters if necessary. So there shouldn't just be prolonged detonation going on without you noticing. Nevertheless, head gasket damage is one of the possible failure modes if an ongoing detonation problem isn't corrected.

 

I'm sure it could survive another but I honestly don't care to do it. The car runs 80% normally even with the performance issues and we're getting about 35 miles per gallon average across the tank

Also I may contact Toyota and ask about getting the latest firmware update for gen 3 with new EGR and see if they even know what I mean haha

Or I can play around with various air filter options until I hit the sweet spot haha