USING 4TH GEN ENGINE AND EGR INTO 3RD GEN

Did you use the 3rd or 4th generation exhaust manifold?

If you used the 3rd gen manifold, you should review the previous threads here where people have tried that. The trouble is, the 3rd gen manifold delivers the exhaust at a higher pressure than the larger 4th gen EGR components expect (they are larger to flow the right amount of EGR with the lower-pressure exhaust tap on the 4th gen).

You can try to improvise some kind of restriction to avoid getting too much EGR flow, but so far I don't think I've yet seen anyone report getting the engine to run well that way.

 

Completed my 4th gen swap yesterday. JDM motor.

As @ChapmanF stated, I believe I’m going to have to restrict EGR flow. She runs flawlessly at idle and full throttle and has zero tendency toward running hot. My coolant routing is water outlet on back of block > EGR > Cat > Heater core > bypass tube wrapping around block back to thermostat/ water pump.

The only issue I have is suspected excessive EGR flow at partial throttle. It stumbles slightly, like a very soft version of a misfire, intermittently.

I am running 4th gen EGR on a 3rd gen exhaust and intake manifold. Bent then cut/welded the pipes to fit perfectly.

I will try blocking the flow soon with a putty knife to see if the EGR is indeed the culprit… right after I take it to work and verify there is no EGR replacement/relearn option in a high end scantool.

 

How I fit it:



I wish I would have read about the issues with the 4G egr system in a 3G prius before I used it. I chose it because that core has much larger passages inside. Much harder to clog.

I quit life as a Master Toyota tech in 2010. A friend worked there until last year and said he still can’t think of a 4G car coming in with a clogged cooler, ever.

 

4g egr factory takes exhaust after the cats. You may get more hydrocarbons before the cat.

 

Yeah… I didn’t learn that it takes much lower pressure gas in higher volume from further downstream until after fitting the 4G EGR. Or I would have stuck with what I had.

(My 4G engine did not come with an exhaust manifold.)

 

They learned a thing or two from third gen...

If you still have your gen 3 components, I'd consider going back to them. That may require a replacement exhaust manifold, depending on how beat up your mod'd one is.

 

I heated, bent, cut, and welded the rear pipe to perfectly fit the 4th gen EGR.

Before I explore reverse-metal-fab, I’m going to drive it with the good old putty knife in there to confirm it is due to an excessive EGR flow, then I’ll fab a restrictor plate in a location which is easy to clean as a temporary proof of concept before deciding on a plan.

I’m fairly committed to the 4th gen EGR, having cut and spliced and combined heater hoses to route coolant where it needs to go. It’s VERY different from a 3G car.

Outlets on cooler are very different and I have it plumbed: outlet on block > EGR > Cat > Heater core > return to thermostat housing.

So far it hasn’t risen above 194.5, and although it is only 70ish here as a high, I would gladly trade my EGR issue for a lack of the coolant problems others have experienced. (If I actually dodged that bullet.)