Euro VI NOx control will be a problem. If SCR is used, efficiency is retained (or even improved since the EGR level can be ahem...reduced). But consumers will moan about having to fill up the urea tank.

The other option is a Nox trap. But they require running RICH for a few seconds every minute or two, and this does hurt efficiency.

So small diesel installations will become relatively more expensive than petrol, with increased maintenance costs

A 3 cylinder boosted petrol engine WILL have a DMF-and it will be put under almost as much stress as a 4 cylinder diesel. Small petrols tend to require variable valve timing (inlet and exhaust) and increasingly use direct injection which bumps up the initial cost. Hybrid drivetrains all but eliminate manual transmissions. This is a turn off to traditional drivers and those (like me) who think that CVT isn't that great in practice.

Don't forget that the VAG group are now starting to fit cylinder deactivation technology to the small petrols. The 1.4 TFSI for example will shut down 2 cylinders between 1400-4000rpm if the car is cruising and not under load.

More marketing bull.

Cummins do that on their pushrod 6.7 diesel. Chrysler and GM have been fitting cyinder deactivation onto their V8s for 10 years. The gains just aren't great on 5.0+ V8s; on tiny 4 pots the gains are tiny. On pushrod engines cylinder deactivation is relatively easy because you simply use collapsable lifters. On OHC engines the system is a pain-you need a fairly complex valvetrain-which bumps up the cost.

Diesel engines don't really need this gubbins because they are seldom heavily air throttled.

Cylinder deactivation also puts diesel like stress on the DMF. When you try to make a petrol engine behave like a diesel engine, it will develop diesel like problems.

Am wondering if the new 3 cylinder Ford unit uses direct injection and if so, have they got around the problems VAG seem to have had with carbon build up in the inlet tract? Agree, these new generation petrols aren't going to be cheap to fix, with the extra complexity built in, Piezo injectors(?) integral manifold/heads etc.

Also, interesting that Toyota do not appear to be moving into direct injection and small turbo technology just yet, rather sticking with VVti and hybrid development.

With the up and coming launches of various small capacity, "highly efficient" turbo petrol engines, will lots of other manufacturers follow suit? Could this be the end for smaller capacity diesels and all of their potential problems.

Keep drinking the Kool-Aid. A stoichiometric petrol engine engine is never going to be as efficient as a lean burn compression ignition engine. Fundamentally, the thermodynamic efficiency is a at least 20-30% lower, and whatever you do with variable this or electronic the other, the basic fundamental principle remains.

The higher energy density of diesel flatters the mpgs even further (although diesels will-quite wrongly-complain atthe extra 5% cost at the pumps.

Whether I drink a powdered fuit drink or not, isn't going to alter my question.

The key word there is "stoichiometric

I don't think it's that simple. Most of the big diesel stationary engines are offered in spark ignition lean burn variants. Running on natural gas with an antiknock index of over 120, detonation isn't a huge problem. Boost and static compressin are kept high. Their brake efficiency is still considerably higher than the diesel variants. Lean mixtures burn slow and need too much spark advance.

They could run lean burn and even possibly eliminate the CAT as CO output could be slashed

Not really. If you go slightly lean, CO and HC emissions fall whilst NOx rises. As you continue to lean out, Nox falls and CO and HC start to rise as partial misfiring becomes more frequent. The burn becomes slow and unstable. Cycle by cycle variation increases and engine smoothness is impaired.

The way to avoid this is via charge stratification which is what er...diesel engines do!

Edited by unthrottled on 12/03/2012 at 12:59