Would Adblue put you off another diesel

[Sad555]

Haven't noticed any posts yet from Octavia and superb owners having paint damage from Adblue spillage?

[Ryeman]

That's a pretty enormous proviso. Take almost any diesel model that you care to mention and show me a petrol model that's equivalent in torque but that doesn't have much greater emissions and proportionately lower mpg. (Actually there won't be too many models where a petrol option even has the same torque as the diesel.)

Err, at the risk of sounding like a sad old geezer, the low reving 1.2 Peugeot does it and cleaner too.

[gadgetman]

Haven't noticed any posts yet from Octavia and superb owners having paint damage from Adblue spillage?

It damages fabric, plastic and painted surfaces as it's Ammonia.

[Ryeman]

If it damages paint the handbook will have a warning to that effect with a remedy.

[weasley]

It damages fabric, plastic and painted surfaces as it's Ammonia.

It isn't actually ammonia, it's urea, but it does decompose to ammonia if allowed to.

[Huskoda]

That's a pretty enormous proviso. Take almost any diesel model that you care to mention and show me a petrol model that's equivalent in torque but that doesn't have much greater emissions and proportionately lower mpg. (Actually there won't be too many models where a petrol option even has the same torque as the diesel.)

I did qualify my statement that the petrol of equivalent power would come at a much higher cost.

 

As for an example. My Subaru Forester. Both the diesel and petrol turbo have 350NM of torque so are comparable side by side. Which I did. And bought the petrol.

 

The diesel also has the same HP as the NA petrol (150) so you can compare both ways  They're both about the same price, but the NA petrol feels weedy and asthmatic.

 

People buy diesels because they're better value for money (assuming nothing breaks). There's nothing wrong with that, but there's no reason to pretend otherwise.

[prodata]

I did qualify my statement that the petrol of equivalent power would come at a much higher cost.

I'm not sure that you said that exactly, but perhaps the implication was there.

 

As for an example. My Subaru Forester. Both the diesel and petrol turbo have 350NM of torque so are comparable side by side. Which I did. And bought the petrol.

But what were the relative emissions and mpg values? That was clearly the point I was raising.

I'm not a supergreen by any means, but I'd really feel uncomfortable nowadays buying a car that was higher than 180-190 in CO2 emissions, quite apart from the admittedly limited extra costs of doing so. And I've always felt that there's a perceived difference in practice between the capital cost of a car and its running costs. Once you've bought the car that's a sunk cost, which you tend to forget about relatively quickly. But if your cost to fill up is say £80 rather than £60 (or if you need to fill up only every 3 weeks rather than every 2 weeks) then you tend to get reminded of that every single time that you fill up. It's not an economic argument of course but it is a practical pyschological one.

By the way, I don't disagree with the basic point - for equal torque (over a comparable rev span) then yes I'd opt for petrol over diesel. But the other compromises you have to make eg as in CO2, MPG, etc for me might make the petrol a non-starter. For instance I'm currently musing over getting a Macan. Realistically, the only option for me is the diesel (580Nm torque). The 'Turbo' petrol (which 'only' has 550Nm) is around the 210 CO2 mark (as indeed is the lesser petrol). So the petrols, for me, are out of the equation.

Edited 5 August, 2015 by prodata

[Breezy_Pete]

AdBlue is there to counter the increased NOX from the DPF Every time they add another system, its generally been to counter the new problem from the last 'emissions enhancement'. EGRs produce extra soot. So they added DPFs. DPFs increase NOX so now they're getting AdBlue.

 

Diesel is dead. The only 'advancement' being done to it is to chase ever changing emissions requirements.

Is that bolded bit right? I thought all diesel engines produce lots of NO_x irrespective of whether they have a DPF or not?  Got any references/sources?

[Huskoda]

I'm not sure that you said that exactly, but perhaps the implication was there.

 

But what were the relative emissions and mpg values? That was clearly the point I was raising.

I'm not a supergreen by any means, but I'd really feel uncomfortable nowadays buying a car that was higher than 180-190 in CO2 emissions, quite apart from the admittedly limited extra costs of doing so. And I've always felt that there's a perceived difference in practice between the capital cost of a car and its running costs. Once you've bought the car that's a sunk cost, which you tend to forget about relatively quickly. But if your cost to fill up is say £80 rather than £60 (or if you need to fill up only every 3 weeks rather than every 2 weeks) then you tend to get reminded of that every single time that you fill up. It's not an economic argument of course but it is a practical pyschological one.

By the way, I don't disagree with the basic point - for equal torque (over a comparable rev span) then yes I'd opt for petrol over diesel. But the other compromises you have to make eg as in CO2, MPG, etc for me might make the petrol a non-starter. For instance I'm currently musing over getting a Macan. Realistically, the only option for me is the diesel (580Nm torque). The 'Turbo' petrol (which 'only' has 550Nm) is around the 210 CO2 mark (as indeed is the lesser petrol). So the petrols, for me, are out of the equation.

 

MPG isn't brilliant, I get about 29MPG and fill up weekly, compared to my diesel 4x4 Octavia which got 39mpg and was filled every 2 weeks. Emissions are not really comparable. More CO2 (which is relatively harmless at street level) from the petrol, but much lower on toxic gasses like NOx (which is quite harmful at street level, like many things pumped out by diesels). I will be honest, though and not pretend eco-friendliness had any influence on my purchase. Its a petrol turbo Subaru, for goodness sake

 

I did the sums on running cost, including the horrific depreciation (my less than a year old demonstrator had lost 30% of its value when I bought it) and decided I was happy paying a higher, steady cost for a more enjoyable driving experience and none of the crap that comes with diesels (DMFs, DPFs, slow warm up etc).

 

Is that bolded bit right? I thought all diesel engines produce lots of NO_x irrespective of whether they have a DPF or not?  Got any references/sources?

 

They do, but during regens its even worse due to the extra fuel injection and greatly increased temperatures. The EGR is primarily there to *lower* combustion temperatures to reduce NOx (which is why it also increases soot), which is why its somewhat amusing they then stuck a DPF on which basically reverses both effects of it.

 

http://www.telegraph.co.uk/motoring/news/10862975/Emission-tests-substantially-underestimate-pollution-pumped-out-by-diesels.html

 

“When a DPF regenerates there’s a spike in exhaust gas temperature, fuel economy worsens and NOx emissions increase,” says Molden. The effect is especially pronounced under acceleration, when the NOx levels typically double compared with the same acceleration with the DPF operating normally."

[Breezy_Pete]

Ah, that makes sense. Only during regens.

Thanks for clarifying.

[VAGCF]

I'd think more people prefer the torque you get with a diesel, for pretty low power/cost. The diesel driving experience isn't that great, with very frequent shifting due to the narrow power band. A petrol with the same amount of torque as a diesel, side by side, is far better to drive. Between a diesel and petrol of the same horsepower, yeah, the diesel feels better as it has more go

 Not meant as a comparison but my wife's Mini Cooper S is a joy to drive (better in some ways than the TT!). Not because of it's 175BHP but because of the way it pulls from low revs in all gears (this is why it's better than the TT where 6th is too high unless blasting down an autobahn!). It really is a torquey motor (1.6 turbo) and is lovely when driving in a relaxed manner or giving it some beans. Not bad on fuel either.

[gadgetman]

If it damages paint the handbook will have a warning to that effect with a remedy.

Says it in my manual. Damages paint, plastic and fabric. Wash spillages immediately with plenty of water.

[old newbie2]

 Not meant as a comparison but my wife's Mini Cooper S is a joy to drive (better in some ways than the TT!). Not because of it's 175BHP but because of the way it pulls from low revs in all gears (this is why it's better than the TT where 6th is too high unless blasting down an autobahn!). It really is a torquey motor (1.6 turbo) and is lovely when driving in a relaxed manner or giving it some beans. Not bad on fuel either.

Interesting. All our 2.0 TSi's pull well from low (1.1k 'ish) rpms, but the 2 Skoda's have much lower gearing , 3k rpm in 6th = 77 mph, but the EOS is different, 3k in 6th = 95 mph,

with similar differences in the lower gears.

 

It's possible that your Audi has similar gearing, we do notice that the EOS is usually 1 gear higher than the Skoda's, & that if we find ourselves in a hurry, we need to downshift more.

 

The good point is that we seem to cruise the EOS a little faster than the other cars, whilst keeping the rpm's down. 

 

DC

[Ryeman]

From what I recall all cars reprocess their blowby gasses via an EGR valve but the diesel ones seem to foul more.

The DPF deals with particulates and the AdBlue converts the NOX into straight and safe nitrogen.

Petrol cars only have the EGR valve obviously.

[ejstubbs]

Petrol is for the fun stuff...

 

For fun stuff, I have two wheels rather than four (and petrol, obviously, though some odd people do make diesel bikes - apparently the military like them).

[muddyboots]

Adblue wouldn't put me off another diesel, it's just an occasional top-up isn't it ?

Compared to topping up my screenwash every few days in winter, and getting through gallons of screenwash, it doesn't seem like a big deal ?

 

In fact we're looking at buying a Superb 3 150 TDI, and that'll have an Adblue tank.

[muddyboots]

Does the use of Adblue replace the use of EGR ?

[Huskoda]

No, its in addition.

[weasley]

This has all come about because the limits for NOx have been lowered so much in Euro 6 that the use of EGR could no longer get below the limits alone, hence the need for the SCR to help out.

And don't think that petrol engines are safe from meddling. Direct injection petrol engines make a lot of particulates but of a very small size, so not seen as smoke and below the size that is currently legislated. This stuff is potentially more harmful than the larger lumps a diesel makes because it can get further into your lungs. Gasoline particulate filters are mooted for the future.

[Huskoda]

Diesels no longer make large lumps, due to the DPFs (and to a lesser extend, increased use of common rail injection, though that predates DPFs). Yes, GPFs (Gasoline Particulate Filters) are coming in for direct injection petrols too, though everything I have read shows that they are likely to be much cheaper to replace (due to not needing the same materials as the diesel ones) and being better at self cleaning (due to petrol's hotter running).

 

NOx and other toxic gasses from diesels have been ignored in the EU in the mad frenzy over CO2 at the cost of people's health. The Americans haven't ignored it and VAG have been forced to sell AdBlue diesels there for years now and its part of the ongoing stigma against the fuel there.

[Ryeman]

Does the use of Adblue replace the use of EGR ?

The EGR has the job of redirecting the oily blowby gasses past the rings from the sump.

It'll eventually clog up and need cleaning or replacement.

Petrol one do the same.

[muddyboots]

The EGR has the job of redirecting the oily blowby gasses past the rings from the sump.

It'll eventually clog up and need cleaning or replacement.

Petrol one do the same.

Think you're mixing that up with crankcase ventilation ?

 

EGR just introduces exhaust gases back into the intake.

[skomaz]

though some odd people do make diesel bikes - apparently the military like them).

 

Well I never knew that!

 

as an aside one of the guys at work parks his Triumph Tiger next to my Civic - awesome bike!

[weasley]

Diesels no longer make large lumps, due to the DPFs (and to a lesser extend, increased use of common rail injection, though that predates DPFs). Yes, GPFs (Gasoline Particulate Filters) are coming in for direct injection petrols too, though everything I have read shows that they are likely to be much cheaper to replace (due to not needing the same materials as the diesel ones) and being better at self cleaning (due to petrol's hotter running).

 

NOx and other toxic gasses from diesels have been ignored in the EU in the mad frenzy over CO2 at the cost of people's health. The Americans haven't ignored it and VAG have been forced to sell AdBlue diesels there for years now and its part of the ongoing stigma against the fuel there.

 

The diesels do make the lumps, but yes, the DPF catches them, so the exhaust gases are 'clean' (but the engines aren't).  GPFs may be cheaper/easier but are also likely to have a much smaller pore size so will block quicker.

 

Diesels run hotter than petrols - that's why they make more NOx.

[weasley]

Think you're mixing that up with crankcase ventilation ?

 

EGR just introduces exhaust gases back into the intake.

Indeed.

 

By sending some of the exhaust gas back into the intake you essentially remove some of the oxygen in the intake air, so it burns cooler, hence reducing NOx (but driving PM up, and introducing various other combustion products into the intake stream).