Looking to buy 2015 TDI, mechanical questions

[flyingtoaster]

I was looking into buying a Prius, but I realized diesel is much cooler. I test drove one at the dealership and the cargo space was smaller than a midsize trunk, so I may wait for the Sportwagen. I read every technical brief I could find about the EA288, and diesel engines in general, over the past few days. Here are some lingering questions.

Since it uses urea injection instead of post-combustion injection for DPF cleaning, are the injection pumps the only potential issue with running biodiesel (over an older TDI)?

How does a DPF help the environment when the cleaning cycle sends all the particulate back into the atmosphere? Is there an actual chemical reaction happening, like in a cat, or does it catch the soot and blast it out later?

Is the engine mechanically different from the GTD version? I was reading that the Mexican assembly plant is not equipped to build GTDs. Since the main difference between a GTI and GTD is the engine, it seems like they are different.

 

[FreezingInSask]

Your confusing 2 different things. Soot(Carbon) is collected in the DPF, than through a chemical reaction the soot or Carbon combines with Oxygen and Nitrogen Oxide, to create Carbon dioxide and Nitrogen Oxide, clear gasses. What is left in the DPF is ash particles that it is unable to remove, usually from engine oils.

The Urea injection is there to remove the Nitrogen Oxide from the emissions. The EGR system is the first step, by putting the cooled exhaust gas back into the combustion chamber it lowers the temp in the cylinder which lowers the amount of NOx produced. Now with new emissions the amount of NOx has to come down even lower. The Urea is injected in the exhuast after the DPF and the heat in the exhaust turns the Urea into Ammonia molecules. The Ammonia molecules react with the NOx, and Nitrogen and water is produced.



The adding of Urea does not mean post injection is no longer needed as post injection is for the DPF(they may use it to make sure the SCR is warm enough of reaction to take place as well). The post injection is needed to warm the DPF system quicker and then needed if an Active regen is required.

 

[flyingtoaster]

Your confusing 2 different things. Soot(Carbon) is collected in the DPF, than through a chemical reaction the soot or Carbon combines with Oxygen and Nitrogen Oxide, to create Carbon dioxide and Nitrogen Oxide, clear gasses. What is left in the DPF is ash particles that it is unable to remove, usually from engine oils.

The Urea injection is there to remove the Nitrogen Oxide from the emissions. The EGR system is the first step, by putting the cooled exhaust gas back into the combustion chamber it lowers the temp in the cylinder which lowers the amount of NOx produced. Now with new emissions the amount of NOx has to come down even lower. The Urea is injected in the exhuast after the DPF and the heat in the exhaust turns the Urea into Ammonia molecules. The Ammonia molecules react with the NOx, and Nitrogen and water is produced.



The adding of Urea does not mean post injection is no longer needed as post injection is for the DPF(they may use it to make sure the SCR is warm enough of reaction to take place as well). The post injection is needed to warm the DPF system quicker and then needed if an Active regen is required.

Thanks for the detailed information. I understand the system much more clearly now.

 

[Cogen Man]

Excellent explanation FreezingInSask.

 

[03_01_TDI]

I test drove a Prius yesterday. The current year end sale prices are nice. Over 5k off. However they would need to drop 10k or more from the sticker price. The sound of the little engine and cvt trans was terrible. Sounded like a upset blender and felt like it didn't have the power to get up a decent hill. My wife even asked if I had it to the floor.

In comparison we test drove the lexus ct200h and I was impressed. It's still slow but lexus did a good job at masking the engine and cvt sounds.

 

[tdi90hp]

those CTs are neat

 

[srs5694]

I test drove a Prius yesterday. The current year end sale prices are nice. Over 5k off. However they would need to drop 10k or more from the sticker price. The sound of the little engine and cvt trans was terrible. Sounded like a upset blender and felt like it didn't have the power to get up a decent hill.

I think I read this in a review somewhere: The Prius is a cheap car with an expensive drivetrain. I think that simple statement is a useful starting point for understanding the Prius, and either accepting it for what it is or buying something else. It can be elaborated a bit by saying that the expense of the drivetrain is geared toward fuel economy, not performance -- hence your complaints. Viewed through this lens, a Golf TDI (which costs roughly the same as a Prius, depending on equipment) is a more expensive car with a (relatively) less expensive and conventional drivetrain, albeit one based on diesel rather than gas.

 

[tdi90hp]

I think I read this in a review somewhere: The Prius is a cheap car with an expensive drivetrain. I think that simple statement is a useful starting point for understanding the Prius, and either accepting it for what it is or buying something else. It can be elaborated a bit by saying that the expense of the drivetrain is geared toward fuel economy, not performance -- hence your complaints. Viewed through this lens, a Golf TDI (which costs roughly the same as a Prius, depending on equipment) is a more expensive car with a (relatively) less expensive and conventional drivetrain, albeit one based on diesel rather than gas.

Diesel drivetrain I would imagine is pretty darned expensive especially with all the emissions stuff. Those Prius cars do last. I often go to Vancouver and every cab is a Prius. 500,000kms is no big deal. But they do feel like a tin can after 100-150K

 

[flyingtoaster]

I think I read this in a review somewhere: The Prius is a cheap car with an expensive drivetrain. I think that simple statement is a useful starting point for understanding the Prius, and either accepting it for what it is or buying something else. It can be elaborated a bit by saying that the expense of the drivetrain is geared toward fuel economy, not performance -- hence your complaints. Viewed through this lens, a Golf TDI (which costs roughly the same as a Prius, depending on equipment) is a more expensive car with a (relatively) less expensive and conventional drivetrain, albeit one based on diesel rather than gas.

I am driving a 2014 Corolla rental with the 140hp eco motor. Part of the reason new cars get such good fuel economy seems to be drive by wire throttle and automatic/cvt programming, not the engine. The Corolla has the worst throttle response I have ever felt. S mode is a little better and B mode is beasty. My S2000 is DBW, and since it is tuned for power, pressing the gas either opens the throttle completely or not at all. With a CVT and eco tuning, the S2000 could go from 18 city to 25 easily. With S2000 mapping, the Prius would burn rubber through the quarter mile with the electric motor. I want the car with the best engine and chassis for the money and I believe it is the Golf. The only issue, as TDI90hp touched on, is the emissions equipment. I'd rather not pay for something I plan on removing, but these days, it comes with the territory and we wouldn't have a 2015 diesel anything without the DPF. And we couldn't insure 707hp RWD monsters without DBW.