Monday, June 26, 2017

An expensive lesson about diesel particulate filters

I have a diesel SUV, a Holden Captiva 2011. So far it's been a great car. This car has towed a camper trailer around the place and been serviced regularly. The Captiva has been a fabulous family SUV up until I ran into Diesel Particulate Filter (DPF) issues .

First up if you don't know what a DPF is go and read this Wiki - DPF

I had issues with my DPF. The DPF had became too blocked to clear through a normal regeneration process.

What's a normal regen you ask? That when the symbol below comes on in your dashboard. It kind of looks like a fart symbol. This indicator tells the driver that the DPF is nearly full and needs to run a regen process.

Image result for DPF light captiva

To regen a DPF you basically need to go for a long drive at speed (while the symbol is ON). keep the rev's above 2000RPM and the speed above 50 KM/H for around 30 minutes (if you find ANYWHERE inside of  Sydney to do this please let me know).

In my case this light came on and then turned off. Great that was a quick regen. Turns out the regen process did not work and now the DPF was getting rather full. This continued until one day driving along the hose for the turbo inlet hose fell off due to the backpressure (from what we knew later to be the the DPF unit). Performance of the car went really bad.  My local mechanic was kind enough to refit the hose for me. This however didn't fix the issue. Performance of my SUV was still really crap I had trouble getting the car above 50 KM/H.

This is when we found that the DPF had become completely full and blocked. This required having to remove the DPF unit and have it professionally cleaned 3 times and reinstalled. This wasn't cheap as it required an engine service at the same time (only had the same service 3 weeks ago) all up this cost me over  $1200 AUD to repair.

Interesting to note since fixing the DPF is that the car fuel economy has increased dramatically. I've gone from 12.9 - 13.9 L Per 100 KM down to 10.1 - 10.4 L per 100 KM's. My car has always sat around the 12L per 100Km in suburban areas I figure this means the DPF was at least partially blocked since we bought the SUV (the Captiva was bought used). The performance of the car seems to be much better too. It's quick to take off and acceleration seems a bit quicker (possible human bias here)

Ultimately this may prove to me that Diesel cars are great for highways but rather not suited for the short trip suburban market (unless you take your car for a long drive once every month or so). For me this also raises the question of how is the DPF better when it may cause us to use more fuel? don't get me wrong I know why we need to have DPF's to break down larger particulates into smaller particles but it's at the cost of more fuel use over a lifetime of the car which equals more carbon monoxide released. We reduce issues with particle inhalation as the expense of producing more carbon and pollutants.

Extra Note: If you do the sums on how much extra this cost us over 50,000KM since owning the car (based on diesel price of $1.22 per litre and 12.9 KM Per 100KM) we've had to pay an extra $1428.00 in fuel costs since owning the car + $1200 to repair  the faulty DPF.

Looking at the official Fuel ratings for a 2011 Diesel Captiva we should of been getting around 8.3L/100km (tested as 9.8L/100KM) Source.

Update 8-August 2017.
It's now a few months later and my Captiva is still running at around 10.2 - 10.4 L per 100\KM for urban area traffic which is almost a 20% fuel efficiency improvement over what it was previous to the DPF issues (also hints at this being a problem since we bought the car used).

If you find this article useful please leave me a comment.

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