Super Diesel

[billyo]

Does super diesel make much difference? I think it is higher cetane and guess that like high octane petrol only a few cars can benefit from it?

[HDi fun]

I find the stuff to be quite good, especially BP Ultimate Diesel. Unlike spark ignition engines all diesels will benefit from high cetane fuel.

Cetane is a rating of the diesel fuel's combustibility, whereas Octane is a rating of petrol fuel's ability to resist ignition.

[petescustompipes]

so with a higher cetane rating would pre-ignition be a problem in a diesel?

[HDi fun]

It's impossible for a diesel engine to suffer from pre-ignition simply because the only thing in the cylinder bore during the compression stroke is air and air doesn't burn.

The ignition timing is ccontrolled by the injection of the fuel. It ignites because of the high temperature of the compressed air.

All Common rail systems (yours is a phase II CR system) use at least two injection phases per cycle. Some of the latest are up to FIVE!!!

The first is called a pilot injection - a small volume of diesel is injected to start the fire burning. Once underway the main injection phase commences and a larger volume is fed in. This two stage process eliminates the age old problem of noise which was a problem with all direct injection engines.

[petescustompipes]

thanks for that hdi, once again your a wealth of knowlage.

you say some of the latest have up to five phases per cycle, would this be for improved fuel economy or for torque purposes?

[HDi fun]

The FAP (particle filter) Peugeots add a third phase which is only used during filter regeneration.

I have written about this elsewhere so I won't regurgitate it, other than to say the purpose is to send buring gases out of the cylinders and into the filter to literally incinerate the accumulated soot.

I think the purpose of using additional injection phases besides the filter regeneration is because of the ever increasing diesel injection system pressures and having the ability to control very very finely indeed the amount of fuel delivered. Once the injector is 'opened' the accumulated pressure diminishes so perhaps opening and shutting 2-3 times in the main injection phase allows the fuel dose to be dished out faster.

So it's basically exactly what you've suggested, which is an attempt (a good one) to increase efficiency in terms of power delivery, fuel economy and emissions control.

I suppose that once the injection system is refined to the point that there is NO soot under any operating conditions then the particle filters can be abandoned - they are, after all, very complex devices that are doing what is a very crude job.

I'm not totally sure on this one though - I will do some research and provide a more comprehensive answer - bear with me

By way of note, the HDi system in your car operates at about 900 bar. That's 900 times atmospheric pressure!! The 2.2 operated at over 1300 bar. Current common rail systems are running at over 2000bar.

[indiaman]

In India we have two grades of Diesel fuel, normal and Hi performance, I have used both and see no difference in either performance or economy, IMHO, the only criteria should be that the diesel fuel be free of impurities and contaminents,and have a low sulphur content

[toothandnail]

A low sulphur content may be good for the environment, but it is less than wonderful for the engine, since low sulphur diesel is lacking in lubrication for the top end of the engine, and can lead to problems with injectors and other expensive parts.

Some additives help improve the lubrication propeties of low sulphur diesel, but too few people are aware of the need to use them, which may result in premature wear to pumps and injectors.

Paul.

[HDi fun]

You're likely to get a better fuel by buying from BP, Esso, Shell etc, than from the supermarkets. Despite the fact that the base stock is the same, and all fuels meet the MINIMUM BS or ISO standards, the premium brands will contain a better additive package than the supermarket fuels. It does go a long way to compensate for the low sulphur levels.

I rate super-diesel. I ran the Peugeot exclusively on BP Ultimate. We still run the little IDI NASP Seat on the stuff. And I still administer the odd can of Forte treatment or the occasional dose of Miller Diesel Ecomax.

Good fuel will preserve your engine. In modern diesels the injectors and pumps are under huge load with the huge rail pressures.

Adding £100 a year to your fuel budget is far cheaper than replacing injectors and fuel pumps. Injectors can be upwards of £300 EACH and can fail as early as 100,000 miles if they become clogged or corroded.

[indiaman]

Originally Posted by toothandnail

A low sulphur content may be good for the environment, but it is less than wonderful for the engine, since low sulphur diesel is lacking in lubrication for the top end of the engine, and can lead to problems with injectors and other expensive parts.

Some additives help improve the lubrication propeties of low sulphur diesel, but too few people are aware of the need to use them, which may result in premature wear to pumps and injectors.

Paul.

A low sulphur content is good for a diesel engine, as there is considerably less corrosion. Also please note the following:

Cetane Number is a measure of the ignition quality of a diesel fuel. It is often mistaken as a measure of fuel quality.

Cetane number is actually a measure of a fuel's ignition delay. This is the time period between the start of injection and start of combustion (ignition) of the fuel.

In a particular diesel engine, higher cetane fuels will have shorter ignition delay periods than lower cetane fuels.

Cetane number should not be considered alone when evaluating diesel fuel quality. API gravity, BTU content, distillation range, sulfur content, stability and flash point are also very important. In colder weather, cloud point and low temperature filter plugging point may be critical factors.

[HDi fun]

Also do not confuse petrol octane rating with diesel cetane rating. They are nowhere near the same thing and cannot be compared.

[jarrus]

I guess low sulphur would cause more damage in older diesel more so than new one's like HDi's car, because it was made when diesel has low sulphur so engineers will have designed to compensate for it,

I have used both BP ultimate and shell v-power diesels

I find the BP to improve performance the most but I'm yet to find a BP garage in my area that isn't a franchise because they charge £1.20 per litre for the regular stuff and £1.40 for the ultimate!! I'm sorry but that's daylight robbery to me, yes it's better but my tank holds 60 litres of diesel (62 if you run it dry) and that makes it over £80 to fill my car!?!?! Yes my little 306 costs £80 to fill on this stuff!!

The shell stuff I would say is a bit hit and miss, one time I will have a good tank the next it is rubbish,
but even the best tank I had still wasn't as good as the bp I have to say

Currently I use either esso, texaco or shell (normal) which ever I'm nearest to

Bp is the best super diesel

I also found it good when mixed 50/50 with bio diesel but my car is running a lucas pump at the moment so It decided it didn't like it after a few tanks...

[HDi fun]

THe later cars do accomodate the low suphur stuff. BP Ultimate noticeably increased the performance

[jarrus]

Yeah likewise,
you would you happen to know the chemical make up of both Shell V-Power diesel and BP ultimate diesel, It might help explain why they are soo different.

From what I know the V-power uses shells gas to liquids technology not sure how it works though...

[HDi fun]

I'm not sure either. But I can vouch for BP Ult diesel.