4th generation coming 2015!

3rd gen EGR is prone to build-up. Hope they address that.

 

ALL EGR systems are prone to build-up. It's simply a service item.

 

True, but some are worse than others.
I can imagine a cooled EGR having a quicker build up of deposits than the traditional type. Dropping the gas temperatures could lead to more solids coming out of solution.

 

Well, it's an arduous, undocumented maintenance item. Everything from the exhaust manifold, through the EGR and the intake manifold is prone to tarry build- up.

 

If 7% more exhaust gas is recycled, the warm up time should be shorter too, as more exhaust heat recovery is possible.

 

Next Toyota Prius Hybrid: 40-Percent Thermal Effiency From Engine, Toyota Says

 

Just curious:
I have not measured the 2015 Prius v, but might the "pouty lips" add about 6" to the otherwise same size predecessor? Visually, they do.

 

what is this build up you speak of? my '04 has 135,000 miles or so, with no ill effects.

 

It's a tar-like 'coke' accumulation that gradually builds up inside the EGR system...unseen...until its presence chokes proper EGR operation off.

 

thanks, what causes it, and when does it typically become an issue?

 

It's basically the ash from the fuel. The same stuff that turns the inside of the tailpipe black.

 

All the more reason to own a PiP!

 

About the spare tire discussion earlier: Flat Tire Moment In A Nissan LEAF - Video

 

Does the dealer bend you over with or without lube at the time of purchase?

 

is it worse in some parts of the country?

 

I don't think there is enough difference in gasoline formulations. Perhaps, ethanol produces less?

 

The ethanol dissolves the buildup. Higher percentage ethanol in your gas the less buildup will remain.

I use 100% gas almost exclusively but I do run some ethanol laced gas a few times a year to remove buildup.

How often I need to do it I don't know but since it is similar in cost per mile it isn't a big loss for me to do it too often.

Check out puregas.org for stations near you that have 100% gas with no ethanol then compare gas prices vs the 5% or 10% or whatever% ethanol in your area. Figure you'll lose gas mileage at about the percentage of ethanol in a Prius (10 % ethanol might drop your mileage by 15% at most, likely will be less). So if the gas prices are $2.20 for 10% ethanol or $2.40 for 100% gas I'd get either gas because it is about a 9% price difference, If the comparison is $3.30 for 10% ethanol vs $3.50 for 100% gas I get the 100% gas because it is about a 6% price difference. The bigger the price difference the more it makes sense to use the ethanol, the less price difference the more it makes sense to use pure gas.

 

just doesn't seem to be much of an issue in the first one or two hundred thousand miles. am i wrong?

 

I'm not an expert on EGR but general knowledge leads me to this path of thought:

Engine temp / Catalytic temp affect how full / complete the combustion is. The lower the temp of combustion the more particulates left behind to cause the buildup.

Thus short trips and/or cold environment will increase buildup. Long drives / hot environment will help prevent it (but not remove existing build up).

OK here is a blurb to back that up

Thus the change in engine design was to reduce smog at the expense of increasing carbon build up inside the engine. If the fuel combusted completely there would be less solids / more gases but the gases are toxic so they made the adjustment.

I'm not sure how accurate the changing the oil part is. I'm just quoting it for the temperature of combustion line of thought.

So back to your question on hundreds of thousands of miles. It might happen to one driver in 40,000 miles and it might happen to another driver in 300,000 miles. Just depends on temps vs miles.

Though since the Prius is very adamant about running the gas engine to warm up the catalytic converter ASAP maybe the Prius just won't be very susceptible to this as a major issue at any number of miles?

Reading back up thread someone said Gen 3 was more susceptible than Gen 2. I wonder how much more if any?

 

when you see people reporting that they pull over and shut down the car and restart to spoof the warmup, i suppose there could be any number of whacky things happening.