X5 35i vs 35d

[MotoWPK]

Originally Posted by 42pilot

Horsepower is torque times RPM, divided by 5252. Torque is measured and horsepower is calculated on dynos.

The constant depends on your power and engine speed units; HP, KW, RPM, RPS, etc. And in addition to measuring torque, you're also measuring engine speed.

[lowlevelhell]

Originally Posted by MotoWPK

The constant depends on your power and engine speed units; HP, KW, RPM, RPS, etc. And in addition to measuring torque, you're also measuring engine speed.

And since we're talking about HP and RPM, the constant is 5252.

[drjoe66]

Originally Posted by Ricsuaq

How short is short? I have a diesel and sometimes I worry about this.

These maybe were issues in the 70s. The soot filter does not need to regenerate too often and can even do this on short trips.

[MichiganMike]

Originally Posted by drjoe66

These maybe were issues in the 70s. The soot filter does not need to regenerate too often and can even do this on short trips.

Diesel Particulate Filters (DPFs) did not exist in the 1970s. DPFs were widely introduced in light duty diesel vehicles since 2000. BMW reports it did pioneering work on diesel particulate filters in 2004.

http://www.bmw.com/com/en/insights/t...le_filter.html

There are certain conditions that need to be met for efficient regeneration of DPFs. Passive regeneration occurs at higher speeds and typically may require 20 or 30 minutes to complete at highway speeds. Active regeneration of the DPF may be possible at lower speeds but also requires 20 minutes or more to complete after operating temperature is achieved and presents some additional issues.

http://www.honestjohn.co.uk/faq/dies...ulate-filters/

"As widely predicted, the problem is that diesel particulate filters have a limited life of perhaps 80,000 to 100,000 miles before they become completely clogged with ash, cannot be cleaned out or 'replenished' and need to be replaced.
Many owners are now finding out that the cost of that can be anything from £1,000 to £3,500."

BMW's replacement interval for the DPF may be up to 150,000 miles. Incomplete or improper regeneration of the DPF may reduce the life span.

http://pmmonline.co.uk/technical/die...-you-need-know

"As a warning, if the owner only carries out short journeys and the vehicle never completes the regeneration cycle, it could cause the condition of the oil to become very poor due to the fuel passing into the oil. If this continues it could then cause the car to run away or start to run on its own oil which will usually end in destruction of the engine. "

[MotoWPK]

Not questioning honest John's honesty, but I wonder if this is the most up-to-date information. While there have been some diesels who have experienced relatively short DPF life since the introduction of DPF's, things have continued to develop on this front, notably the use of ashless lubricating oils and the development of DPF cleaning methods and their increasing availability. The latter can return a DPF with excess ash to service at considerably less cost than replacement.

An interesting discussion on the subject will be found at DieselNet; https://www.dieselnet.com/tech/dpf_ash.php.

Note figure 3 illustrating backpressure increase vs. distance traveled for lubricating oils with varying levels of ash content. Ashless oils had effectively no increase, and the lubricating oils being used in diesels these days (at least light diesels) is ashless.

Lubricating oil is not the only source of ash, others being fuel and engine wear particles, and other factors pertaining to the DPF regeneration will certainly affect DPF life, but it seems as if the situation with DPF life has improved from even a few of years ago.

[MichiganMike]

Originally Posted by MotoWPK

Not questioning honest John's honesty, but I wonder if this is the most up-to-date information.

As you suggest, research to improve the performance and longevity of diesel particulate filters will no doubt continue. It is difficult to predict future developments. In addition, the technology is complex and probably not in the wheelhouse of many on this forum.

http://gearpatrol.com/2014/08/04/adv...-only-be-good/

One issue not addressed in your thoughtful comments is the presence of sulfur in diesel fuel that contributes to particulates. In reading the abstract of the Bodek article from which the Figure 3 you referenced is reproduced, I note the Bodek abstract states: "Despite significant effects from lubricant sulfur and phosphorus, loss of LNT NOX reduction efficiency is dominated by fuel sulfur effects." So even if ashless oils are used as you suggest the sulfur in the diesel fuel remains an issue.

The US has been slower to require ultra-low-sulfur diesel (ULSD) than many European countries and has set a less rigorous standard.

http://www.autoblog.com/2008/05/27/u...-eu-countries/

While ULSD is now widely available in the US the standard is no more than 15 ppm sulfur, whereas many European countries are encouraging or mandating use of ULSD of 10 ppm sulfur or less. In Germany, sulfur levels in diesel fuel of 5 to 6 ppm have been common since 2006. It follows that due to the higher sulfur content in US fuels, diesel particulate filters may operate under more challenging conditions in the US making proper regeneration of the DPF all the more important.

https://en.wikipedia.org/wiki/Ultra-low-sulfur_diesel