Cooled EGR and the Prius c
 

Cleaner exhaust and more fuel efficient. What’s not to like?

Wayne Gerdes - CleanMPG - Sept. 16, 2012

2012 Toyota Prius c – $18,950 to start while providing a 53/46 mpgUS city/highway rating. When it comes to fuel economy, the c is currently the most fuel efficient modern hybrid we have ever driven.

When you search, you find out the coolest things… In this case, it is the fact the Prius c comes equipped with the smallest and possibly most thermodynamically efficient EGR cooler made for an OEM automobile to date.

Cooled EGR

In an effort to meet stricter fuel efficiency and exhaust emission regulations worldwide, DENSO developed its first EGR cooler for gasoline engines. The newly developed EGR cooler is 30 percent smaller than the smallest currently available on the market, while offering equal performance.

How it Works

EGR systems recirculate a portion of engine exhaust gas back into the intake manifold.

At low loads, the use of internally recirculated exhaust gas, commonly referred to as burned residual, or externally recirculated exhaust gas (EGR) has been shown to reduce pumping losses through the combined effects of displacing intake air and decreasing the charge density through heating. Meanwhile, at high loads the addition of cooled EGR substantially reduces the knock tendency of the engine, resulting in an opportunity to advance combustion phasing and improve the combustion cycle efficiency.

For more on EGR in relation to fuel economy, consider the following: Cooled EGR improves fuel economy and emissions in gasoline engines

EGR coolers decrease the temperature of hot exhaust gases recirculated into the intake manifold, which also increases the density of the exhaust gas. This helps increase the performance of EGR systems, which reduce engine loss and prevent engine knocking. Vehicles with EGR systems equipped with EGR coolers can potentially increase fuel efficiency by 2 to 3 percent.

DENSO’s EGR cooler uses finer slits, said to be just 1 mm wide compared with conventional models, with internal fin slits measuring 4 to 5 mm in width allowing the system to discharge more heat per unit volume. This design enabled the EGR cooler to be 30 percent smaller than the smallest product in the market, all while offering equal performance.

Maybe this is what makes it so darned fuel efficient ;)

Re: Cooled EGR and the Prius c
 

You would not think that would help FE, But!!! H

Re: Cooled EGR and the Prius c
 

Nice articled! I got more intimate with the EGR system on my C now. Im going to go under and caress the cooler now hehe. So far Im at 66mpg on the tank and have 100 miles left in range so lets see if I can get to 70mpg with basic driving techniques.

Re: Cooled EGR and the Prius c
 

My Acura K20A3 engine needs no EGR. It accomplishes the same thing with fancy valve timing.

Re: Cooled EGR and the Prius c
 

1mm slits?.. clogging potential anyone?

Re: Cooled EGR and the Prius c
 

Hi Jay:

Read the SWRI paper for more. It is not just valve timing and phasing. This is fuel economy tuning with knock elimination and timing advance on the one side and reduced pumping losses on the other while reducing NOx and CO out.

Wayne

Re: Cooled EGR and the Prius c
 

I realize we're talking gas engines here, but yea clogging egr is why so many in the diesel trucks rip it off