Advantages v disadvantages of a diesel!!!

OK, here we go.

Referring back to my AutoItalia review of the Alfa 159. Remember this mag. has a definite 'sporting' bias:

2.2 JTS (Petrol): Competent and sounds great, but does nothing better than the 1.9JTDM 16v.

1.9 JTDM 16v (Diesel): Best all-rounder and would be my everyday choice.

I think that says everything you need to know about modern diesel technology. OK, so I'm not a fan of the 6-speed boxes, but that's something that's being forced upon the petrol versions as well as manufacturers chase ever higher output / litre.

So what you're saying is that a fuel that releases more energy per litre is good, then?

Yes. But diesel has 15400 calories per lb and petrol about 14700.

But thats not the reson diesels do more to a gallon!

And methanol has only 7000 calories per lb, but alcohol burning motors make big power! Lifes not so simple...

Noppes the end.

If you have forced induction on an engine you can escape the ugly bits of normally aspirated engines whose power is not limited by the fuel you get in but by the air you get in.

Forced induction is not already there on a diesel and where it is installed, it is certainly not for free.

Examples? We have 2 NA-diesels in the company: a 68 HP 1.9 Citroen Berlingo and a 64HP Volkswagen Caddy. They are cheaper than the HDI or TDI-engine from Citroen / VW. The main advantage of the engines is that they are sort of unbreakable.

If you compare engines on performace you have to compare normally aspirated to normally aspirated, turbo'd to turbo'd, compressor to compressor.

On the performance side a petrol engine wins always: it is not limited in RPM because it has an explosion as the combustion opposed to burning the fuel. Compared to a diesel engine a petrol engine is lighter (mostly because the diesel cycle needs high compressions and generates heavy stresses)

What forced industion does is -simplified- putting x % more air in the engine, if you have 50% overpressure then that turbo-engine compares roughly to a NA- engine with 1.5 times displacement of the turbo-engine.

A NA-diesel has a maximum performance of about 40 -50 HP per liter displacement, you can't go higher because the cycle doesn't work above 5000 RPM.

A NA-petrol engine -commercially avaiable- of 1 liter displacement can turn out about 200 HP @ 16.500 RPM. The limits on a petrol engine are the max piston speeds or ohterwise said: the diffenence between piston rings that seal or piston rings that cut.

Forced induction diesels can go about 150 HP/ liter whereas the limit on forced induction petrol engine is not clearly marked: there has been a petrol turbo- engine with 1500 cc displacement producing around 1500 HP...

Tom De Moor

" 3,437 of the "hybrid" cars were sold in the UK between January and July "

Well I know where 3 went (all Priuss, Priuses?) The replaced an R34 Skyline a

400+bhp Stagia and a Z350

The point I've deliberately avoided mentioning so far, is something you keep failing to mention when you attempt to enlighten the rest of us with your 'wisdom' - it's the living proof, that you patently don't really understand the main differences between the two fuels in terms of why they burn the way they do, and thus produce the results they do when burnt in the controlled environment that is the 'combustion engine', that I've given you enough rope to hang yourself by.

Diesel, litre for litre by comparison with petrol, contains more *energy*.

This is why, apart from the actual process that is needed for it to catch fire in an explosive fashion to create the 'bang' necessary to turn a crank, a diesel runs a higher compression ratio which in turn needs less accelerant in addition to the oxygen also burnt in the process.

They're not running 'weak' at all, YTC.

And the thing you appear unable to absorb, is the likes of VAG and BMW appear to have realised the potential for oil burners in a performance application, and are continuing to develop vehicles to that end, that still in general give the relative economy benefits compared to - I guess they have it *all* wrong, eh... LOL

Anyway... keep it coming... it's quite funny to watch.

but what if you don't want to drive an audi?

If you say so.

Is it just me that thinks the only diesel you've ever driven for any length of time is your s**te old Ducato?

For production car technology it is, though. Or we'd all be using alcohol fueled cars.

that's what I have been trying to say all along you cannot rev past 5k in a diesel because it just doesn't work like that playing along with the silly gearing needed to get it to the speeds comparable with a petrol engine you have to make the engines bigger and more powerful and if you compare power for power, the petrol car will win everytime

the only problem is economy, and even then it's not worth paying the extra for the diesel

I think we should save these references for the day an oil burner wins Le Mans. It's coming, and will be sooner than you think if the rumours from VAG and PSA are to be believed.

Er - not unless it's knocking. Petrol is burning, not explosion. It may burn faster though..

cheers, clive

110.9p/l is what they are charging for the normal unleaded in Sloane square and with prices only going to go up, I can see fuel blockades going back in again in a short time the government is screwing too much tax out of the motorist and it's all going to hit the fan again

Exactly.

There's always something better !

My point exactly. There's always something better !

Agreed. I didn't say otherwise.

Er, which ones ? I can't think of any current naturally aspirated Diesels ! All you can compare is Turbo Diesels, because that's all there is :)

Agreed.

Agreed. Normally Aspirated Diesels are s**te. So it's a good job they no longer exist :)

The extra expense to the factory, is simply a couple of hundred quid for the blower and the intercooler. Aside from that, there isn't really any additional complication or things to go wrong. But you already know this :)

Agreed. I didn't say otherwise.

No it wouldn't !

The petrol equivalent, is normally aspirated.

The Turbocharged petrol engine uses *lots* more fuel than the TDI. How is it "equivalent" ?

The "equivalent" engine to the TDI, is one that costs a similar amount, and makes a similar sort of power. You'll find it's almost always normally aspirated, unless it's a low-blow setup.

Turbo Diesel = Normally Aspirated Petrol. This is the "normal" performance class.

Forced Induction Petrol = VTec. This is the "higher" performance class.

The only effective blockades will need the haulage firms, they will be happy with a cut in duty on what type of fuel?

You just think nothing has happened because of the smooth, quite and fuss free way it's propelled you too banning speeds.