Diesel or Petrol

[susi]

Politics, city-specific bans and mileage considerations aside, I'm more than averagely familiar with the progressively tighter exhaust emissions standards, and the current and future technologies needed to meet them. I'm aware of the strengths, weaknesses, servicability and reliability of EGR, SCR, DOC, DPF, plus the associated sensors needed to make them work properly. We run two cars, both petrol. Read in to that what you will.

[Gerrycan]

I would also tend to favour a petrol but I'm not sure that the diesel is necessarily finished yet.

As pointed out above they still  have to produce the stuff in the refineries to produce petrol and other petroleum products and they are not likely to throw it away.

There is always the chance of a technical breakthrough as well.

An Australian company is receiving government research assistance to extract fuel and other products from old tyres and achieving some success. They mixed some of the fuel extract with diesel and the university research facility testing it reported an unexpected bonus in that it reduced emissions and particles by about 30% .

I have also read that injecting small amounts of LPG with diesel combustion results in increased power and cleaner burning but that was largely for the older class of diesels and I have not read the results for newer applications.

Do diesels have the same emission problems with fuels sourced from renewable sources? After all Rudolf's original engines were originally designed to run on fuels sourced from nuts.

[nidza]

Diesel isn't finished and has its advantages. Market will arrange its survival (e.g. less demand, price goes down, makes sense further investment in research...).

 

Nevertheless, for a car such as (v)RS petrol suits more as it severely changes cars personality. Doesn't necessarily mean diesel never makes sense, of course it does. I will lose on my RS 230 at least 2500€ in fuel in 5 years comparing to TDI Superb which was another choice. Decided that 500€/y is worth this fun.

 

Edited 17 April, 2017 by nidza

[fabdavrav]

I have had more than a passing interest since about 1990 when lean burn "FIRE" petrol engines were trying to get proper gov backing....instead we all went diesel due to better CO2...& completely ignored the NOX etc.,...

 

I will only recommend diesel if you do well over 20,000miles a year on motorways etc. Doing it on 30mph school runs is a waste & pollutes more & doing low mileage is even worse for the engine..

 

I know several people who have diesels & do under 10,000miles a year...& they talk to me about the sudden hate towards their cars & tax rises etc & expect me to sympathise?....

 

I just keep winding one of them up as I get a calibrated 45plus mpg out of my 1.4TSI petrol estate which I drive fast.....& he's got a 2lt Jap SUV diesel which does 34mpg....& he doesn't have any need for a car bigger than mine!  He raved the other day as he's been using shell nitro diesel (as I told him to) & he's now getting 42mpg on a long run. That same day I had done a similar run & got 48mpg....

Edited 17 April, 2017 by fabdavrav

[Gerrycan]

Interesting you mention the governments previous lack of interest in NOX and concentration on Co2 regarding diesel because the newer lean burn direct injected petrol engines are producing higher levels of NOX than ever.

You would have to say that further petrol engine developments for even better economy are likely to produce even more NOX.

I'm thinking of the Mazda and their mooted compression engine petrol engines.

[Geek42]

Once again I precede my comments with a disclaimer as I am far from an automotive engineer, but someone on here posted a link to an article about variable compression being good for NOX. Effectively using a bigger block and changing the angle of the crank arm or something to make a full sweep at low compression for full power, but a reduced sweep at light load that gives both reduced swept volume and higher compression. I didn't really understand it, but it sounded good!

[fabdavrav]

9 hours ago, Gerrycan said:

Interesting you mention the governments previous lack of interest in NOX and concentration on Co2 regarding diesel because the newer lean burn direct injected petrol engines are producing higher levels of NOX than ever.

You would have to say that further petrol engine developments for even better economy are likely to produce even more NOX.

I'm thinking of the Mazda and their mooted compression engine petrol engines.

 

That's because the newest Mazda Skyactive petrol is 14:1 compression ratio...almost on par with basic diesel of 15:1...

 

Compression ignition WILL result in more NOX as it uses compression to ignite..& therefore you CANNOT get as complete a burn of all matter/particulates as a conventional spark ignition, the only reason for them producing is because mpg gets better so nice "headline" BUT at the cost of more NOX.

 

Personally a well designed spark ignition petrol, with light pressure turbo, direct injection, variable cams, & run on the best fuels is the best way to go, thankfully some companies make these!

 

My 14yr old Mk1 Fabia with its 1.4lt 16v AUB 100bhp..(cough) engine on its last MOT when I had it produced:-0.00% CO, 6ppm HC, Lambda 1.00, all on fast idle between 2500-3000rpm. & returned 38-44mpg on average.

[Gerrycan]

With the increasing emphasis on emissions I'm not so sure that Mazda will get away with just impressive consumption with the Mk2 SkyActive tech.

Their petrol compression ignition is a couple of years from introduction so the proposed more stringent consumption and 'on-road' emissions test may well be in place by then.

A few manufacturers are already making plans about how they will handle it like with the new VW 1.5tsi engine.

 

Quite a few engines are equipped with direct injection and turbo now but it seems that not all (in the budget brands anyway) have been successful in utilising it for improved power and economy despite sourcing the DI systems from the same manufacturer.

The new and  fancifully named 'Boosterjet' engines from Suzuki seem to be cloning the VW tech successfully.

Suzuki were driven to develop their own when negotiations to license VW engines broke down acrimoniously. I think that VW demanded a percentage of the company, or the CEO's first born, or something else that offended the Japanese.

 

[Ootohere]

All well documented up to September 2015 and the start of VW's public worst nightmare. 

Then plenty is known on what has gone since for the VW Group.

 

Suzuki finally bought back their shares from VW Group overnight as the Emission Scandal was about to break on September 2015.

(Now which Japanese company helped Suzuki fund that buy out that night?)

http://bbc.co.uk/news/business-34275917 

Coincidence.....Pigs flying past....

http://bbc.co.uk/news/world-us-canada-34298259 

 

VW bought into Suzuki to get to the Tech Suzuki had been involved with in partnership with GM & others on Turbos, Superchargers and hybrids.

Suzuki did a diesel engine deal with Fiat, with engines now under investigation.

Suzuki has the experience and success over many years of small capacity turbo charged and N/A engines, even ones they developed but were used by other manufacturers. Suzuki & Toyota even shared R&D and designs.

 

The VW USA CEO left VW to head Volvo in 2010 after being 25 years with VW and others. Stefan Jacoby once tipped to head VW Group, an insider by training and marriage.

He then left Volvo to go head GM International.

http://cbsnews.com/news/stefan-jacoby-leaving-vw-for-volvo-may-have-felt-passed-over 

Edited 18 April, 2017 by Awayoffski

[CookieMonster87]

I'm still unsure after doing a bit of research.

 

I have a 50 mile a day round trip commute on long, quiet rural roads with the possibility of that increasing in the near future (roughly do around 13,000 per year) with a monthly run out of a couple of hundred miles.

 

What kind of return in MPG would I expect to see from either the vRS diesel vs petrol (sensible driving style) based on the above?

 

After all the negativity with diesels being banded about lately I'm becoming slightly put off and starting to look at petrol alternatives (Audi A3 1.4TFSI S Line 40+ MPG for example) however I just don't think the petrol vRS will be cost effective for me.

[ahenners]

17 minutes ago, CookieMonster87 said:

I'm still unsure after doing a bit of research.

 

I have a 50 mile a day round trip commute on long, quiet rural roads with the possibility of that increasing in the near future (roughly do around 13,000 per year) with a monthly run out of a couple of hundred miles.

 

What kind of return in MPG would I expect to see from either the vRS diesel vs petrol (sensible driving style) based on the above?

 

After all the negativity with diesels being banded about lately I'm becoming slightly put off and starting to look at petrol alternatives (Audi A3 1.4TFSI S Line 40+ MPG for example) however I just don't think the petrol vRS will be cost effective for me.

 

Can't comment on the diesel, but I do about 15k/yr and have a 46 mile round trip every day, mainly covered on motorways. Usually get between 38 and 43mpg. I think you should be able to see 40 on A roads if there's no stop/start traffic. I suspect the diesel is about 10-12mpg better in the same circumstances but haven't owned one to know for sure.

[amwphotos]

On 11/04/2017 at 19:37, stu83 said:

 

For what it's worth I do around 15k miles and bought a petrol (230). I get roughly 34mpg average, which from what I gather isn't significantly less than the 184tdi engine. My previous diesel was averaging 39-40mpg on the same journies.

 

 

From HonestJohn real mpg 34mpg is right for a 220 and 230 isn't much different. However the 184tdi should get somewhere around 49mpg. That's 50% more and very significant!

 

Try both and see which you prefer. I prefer the feel of a diesel but haven't had a blast in a petrol vrs. Am sure they are both excellent.

[nidza]

 

Check my average in the signature. It is after 5000km, mostly highway ~140km/h, maybe one third stop & go around city.

[courty]

3 hours ago, CookieMonster87 said:

I'm still unsure after doing a bit of research.

 

I have a 50 mile a day round trip commute on long, quiet rural roads with the possibility of that increasing in the near future (roughly do around 13,000 per year) with a monthly run out of a couple of hundred miles.

 

What kind of return in MPG would I expect to see from either the vRS diesel vs petrol (sensible driving style) based on the above?

 

 

Should be looking at mid-40s or better. I do about that in urban areas in my vRS diesel and get around the 44mpg mark; just depends how busy the roads are. 

Best I've got on a long run is 58.9mpg last weekend; 340mile round trip.