Petrol or Diesel

[tofufi]

Originally Posted by XC90Mk1

Anyone working with fuel and combustion will review this thread and think it’s full of the tin hat brigade!

What a joke!

Well said

These days, diesels with DPFs are typically better performing in terms of PM2.5 than port fuel injected petrol engines. GDI engines are a rather different kettle of fish and hence they have GPFs

If asked to choose between petrol or diesel, it would very much depend on the type of use. Long runs, rural areas - diesel. Short runs, town journeys - petrol vehicles.

[Laird Scooby]

Originally Posted by XC90Mk1

Anyone working with fuel and combustion will review this thread and think it’s full of the tin hat brigade!

What a joke!

That must be all the diesel proponents then!

[James_N]

Originally Posted by Laird Scooby

I'm in the process of converting my 760 and will then also be converting my other car - both will be gas injection and i don't envisage any problems except maybe the initial set up. What i'm looking forward to is fuel at ~£2.25/gallon (based on 50p/L for LPG) or thereabouts.

I'd love to do this with a 740. My old 740GLE was LPGed (on the cheap by some dodgy bloke off here!) and it never really ran right, lumpy and what not, but it ran.

I'd love to get myself into a 740 again due to the simplicity, room and bomb proof reliability they offer. Now i have family, i can't afford 18mpg fuel costs, especially as my dad lives a 100 mile round trip away and i go and see him most weeks. Luckily on the way to him is an LPG place at 50p/l so i'd love to get into a 7 series again and get it LPGed, but again its all money.

Can i just ask how much you are looking at for a conversion? The mrs always says no to me getting a 740 but again this is purely because of fuel costs. If i could find a way round that, it wouldn't be a problem.

I know a 740 estate will never be at the forefront of fuel ecomony, but LPG is a nice compromise.

[Laird Scooby]

Originally Posted by James_N

I'd love to do this with a 740. My old 740GLE was LPGed (on the cheap by some dodgy bloke off here!) and it never really ran right, lumpy and what not, but it ran.

I'd love to get myself into a 740 again due to the simplicity, room and bomb proof reliability they offer. Now i have family, i can't afford 18mpg fuel costs, especially as my dad lives a 100 mile round trip away and i go and see him most weeks. Luckily on the way to him is an LPG place at 50p/l so i'd love to get into a 7 series again and get it LPGed, but again its all money.

Can i just ask how much you are looking at for a conversion? The mrs always says no to me getting a 740 but again this is purely because of fuel costs. If i could find a way round that, it wouldn't be a problem.

I know a 740 estate will never be at the forefront of fuel ecomony, but LPG is a nice compromise.

Will reply via PM to save cluttering this thread James.

[XC90Mk1]

Originally Posted by Laird Scooby

That must be all the diesel proponents then!

It’s based on scientists and engineers. I respect your post history etc but I can’t help but think this is one of those times we won’t agree.

Modern diesels I do not believe (based on facts) to be comparable to the versions of the 80s and 90s

[Laird Scooby]

Originally Posted by XC90Mk1

It’s based on scientists and engineers. I respect your post history etc but I can’t help but think this is one of those times we won’t agree.

Modern diesels I do not believe (based on facts) to be comparable to the versions of the 80s and 90s

The big problem is you can't change the Laws of Physics or Chemistry. That is a simple fact. Diesel + combustion = heat + various waste products of combustion. Those waste products have not changed since Otto Diesel first created the compression ignition engine.
It doesn't matter what you hang on the exhaust like DPFs etc, the fact remains the same.

If modern diesels were as efficient as the diesel proponents are claiming, why, why, why do they need things like DPFs?

Consider the Pulsair emissions system on petrols. Fresh air was injected into the exhaust manifold to make the tailpipe emissions appear cleaner. That's like adding water to whisky. If you drink a gallon of whisky neat, you're likely to end up drunk. If you drink that same pint of whisky diluted with a pint of water, you'll still be drunk but need a pee as well as you will still have consumed the same amount of alcohol although twice as much liquid.

Now the problem is the efficiency of the DPFs and they're not as efficient as they would have you believe. You only need to look at medical evidence over the past 30 years to see that.

[Zebster]

Originally Posted by Laird Scooby

The big problem is you can't change the Laws of Physics or Chemistry. That is a simple fact. Diesel + combustion = heat + various waste products of combustion. Those waste products have not changed since Otto Diesel first created the compression ignition engine.
It doesn't matter what you hang on the exhaust like DPFs etc, the fact remains the same.

If modern diesels were as efficient as the diesel proponents are claiming, why, why, why do they need things like DPFs?

Consider the Pulsair emissions system on petrols. Fresh air was injected into the exhaust manifold to make the tailpipe emissions appear cleaner. That's like adding water to whisky. If you drink a gallon of whisky neat, you're likely to end up drunk. If you drink that same pint of whisky diluted with a pint of water, you'll still be drunk but need a pee as well as you will still have consumed the same amount of alcohol although twice as much liquid.

Now the problem is the efficiency of the DPFs and they're not as efficient as they would have you believe. You only need to look at medical evidence over the past 30 years to see that.

You are (deliberately?) conflating the issue of raw manifold emissions from the diesel engine (e.g. pre-DPF/cat/LNT) with the tailpipe emissions from the vehicle it is fitted to!

Your arguments would once have had some basis, say a while ago when diesels and petrols did NOT have to meet the same standards. But now they do! So you are now arguing against the standards!!!

The Pulsair system did not merely dilute the exhaust emissions with fresh air, its purpose was to oxidise unburnt hydrocarbons and CO emissions... https://www.sae.org/publications/tec...172/?PC=DL2BUY

As I said before, arguing about whether diesel or petrol is the most polluting is petty hair-splitting... they are both polluting!

[Laird Scooby]

Originally Posted by Zebster

You are (deliberately?) conflating the issue of raw manifold emissions from the diesel engine (e.g. pre-DPF/cat/LNT) with the tailpipe emissions from the vehicle it is fitted to!

Your arguments would once have had some basis, say a while ago when diesels and petrols did NOT have to meet the same standards. But now they do! So you are now arguing against the standards!!!

The Pulsair system did not merely dilute the exhaust emissions with fresh air, its purpose was to oxidise unburnt hydrocarbons and CO emissions... https://www.sae.org/publications/tec...172/?PC=DL2BUY

As I said before, arguing about whether diesel or petrol is the most polluting is petty hair-splitting... they are both polluting!

I'm not conflating anything, just pointing out what comes out of the engine is still the same as it was 30, 40, 100 years ago.

Nothing to do with standards and not arguing against them. Simple reason being they all meet a standard when they leave the factory, it's after that there is precious little control and with the reduced servicing (sealed unit engines for example) things can only get worse, no matter how many DPFs, PPFs etc you hang on the exhaust - those things have a finite life and at some point will no longer perform their duties.

I'm well aware of the Pulsair intention to oxidise NOx and Carbon particles that were unburned but if it had worked, there would be no need for cars to be fitted with 3-way cats, would there?

Another simple fact is that diesel has always been more polluting than petrol and always will be - i'm not saying petrol is a perfect fuel but it IS better than diesel, likewise LPG is better than petrol.

Thing is, to really argue the case for diesels you need to understand they still produce just as much rubbish as they always have done but a lot of it is now trapped by DPFs etc.

If they were that good at producing clean emissions why is it that diesel fumes still stink so badly? If there was nothing coming out of the tailpipe that was nasty, they wouldn't smell. Likewise with petrol cars that have cats on them - they produce H2S or hydrogen sulphide gas - highly toxic in the right quantity which isn't much!

It's no accident that you can legally decat a petrol car with an LPG conversion!

[Whippy]

Which is a bit like saying that car engines are unacceptably noisy, if they don't have silencers. Or that if you take the wings off an aircraft they're just dangerous.

[tofufi]

Originally Posted by Laird Scooby

Thing is, to really argue the case for diesels you need to understand they still produce just as much rubbish as they always have done but a lot of it is now trapped by DPFs etc.

NOT trapped. Converted into things which are understood to cause less damage to the environment or people's health.

The tailpipe emissions are what matters, not the raw engine emissions before aftertreatment systems.