BP Diesel causing knock?

[White Pointer]

G'day,

You can't really get "pinging" from a diesel. It's something else. I mentioned some possible causes earlier. I've had no response to those so I'll assume that none apply.

In a modern diesel, at a critical point in the compression stoke, atomised diesel is injected into the compressed air and the mixture explodes.

To get a lean explosion that might seem like pinging it suggests that the engine timing for injection is wrong or an injector may be partially blocked.

It may also suggest that the burn is being extended (i.e. a double explosion). The extension of burn is really critical in diesels. It must not occur because it imposes an extra load on the crankshaft in the exhaust stoke and slows the cylinders in the compression stoke. The symptoms of this may be rough running, noticable at idle, and some loss of power.

Apart from timing and injector and other mechanical problems that I have mentioned, fuel quality issues can be a concern.

The two major concerns are (a) ethanol - which is incompatible with diesel but has been bought cheaply and used to dilute diesel - and will extend burn and (b) bio-fuel diesel with incompatible cetane ratios and can extend burn but also fail to atomise properly and therefore not burn properly and can block injectors.

The risks can be significant.

Ethanol will have a scouring effect and clean the engine. This can be a good thing except that a layer of carbon deposits in a diesel actually raises compression a bit and reduces harmful emissions unless you do lots of cold starts. If you do lots of cold starts you might be better off, in the long term, with a petrol engine.

Bio-diesel is a risk unless your car manufacturer endorses its use to an international and Australian standard. To use it your car may have to be retuned.

The symptoms described may damage crankshaft, piston crowns, injectors, valves and the poor cumbustion may block and destroy the catalytic convertor.

I've used BP diesel in my Land Rover Discover TD5 for 8 years and over 160,000Km with no engine dramas. I don't work for BP and I don't own any shares in BP. I have no vested interest. Should we pursue this with BP?

Regards,

White Pointer

[Kevaclone]

I was using BP diesel for years, when I worked there, never had a problem with either the 2L-T in the 4Runner or the 2L in the Hilux, I did get a full pump rebuild(long over due and had nothing to do with the fuel, but it did start leaking too) in 2001 when they were paying to fix pumps affected by the fuel
I don't use it anymore because it is usually up to 10cpl more than surrounding servos

I normally use Matilda or Caltex at mango Hill, always cheap
7-11 fuel if I am near one, they are supplied 100% by Shell these days(previously Caltex)

[rowanda]

I was using BP diesel for years, when I worked there, never had a problem with either the 2L-T in the 4Runner or the 2L in the Hilux, I did get a full pump rebuild(long over due and had nothing to do with the fuel, but it did start leaking too) in 2001 when they were paying to fix pumps affected by the fuel
I don't use it anymore because it is usually up to 10cpl more than surrounding servos

I normally use Matilda or Caltex at mango Hill, always cheap
7-11 fuel if I am near one, they are supplied 100% by Shell these days(previously Caltex)

7-11 supplied by Mobil in NSW, but really most of the stuff comes from the same place anyway.

[Meherio]

Hell Boy,

I had an injector changed about 15months ago, the knock I have had more recently is a little different then the knock I had when the injector failed. When the injector failed it use to sound like the old girl was still cold after it had warmed up, that thin oil sound.

The more recent knock is mostly when you have backed off the power when driving from say 2000rpm and you just accelerate from about 1200rpm until about 1600rpm. Just dosn't sound right. Even the missus said to me "what's up with your car?"

I took it to one Toyota and they said nothing wrong with it so I took it to another Toyota they called me and said they couldn't hear it. So I'm waiting for it to happen again.

[White Pointer]

Hell Boy,

I had an injector changed about 15months ago, the knock I have had more recently is a little different then the knock I had when the injector failed. When the injector failed it use to sound like the old girl was still cold after it had warmed up, that thin oil sound.

The more recent knock is mostly when you have backed off the power when driving from say 2000rpm and you just accelerate from about 1200rpm until about 1600rpm. Just dosn't sound right. Even the missus said to me "what's up with your car?"

I took it to one Toyota and they said nothing wrong with it so I took it to another Toyota they called me and said they couldn't hear it. So I'm waiting for it to happen again.

G'day,

An ECU problem will be a constant, as will a valve problem. A dose of lousy fuel may cause a hiccup and then resolve itself when you get good fuel.

I would investigate the catalyst next. Try driving up a steep hill at maximum torque to produce hot exhaust gases. That will be somewhere around 3000RPM. If the exhaust has a sound like gravel in a mixer during this or after it, it means that the catalyst is RS. This can increase exhaust back pressure with consequent loss of power and load on the exhaust valves - which may explain the sensation of pinging.

Regards,

White Pointer

[FNQCairns]

G'day,

An ECU problem will be a constant, as will a valve problem. A dose of lousy fuel may cause a hiccup and then resolve itself when you get good fuel.

I would investigate the catalyst next. Try driving up a steep hill at maximum torque to produce hot exhaust gases. That will be somewhere around 3000RPM. If the exhaust has a sound like gravel in a mixer during this or after it, it means that the catalyst is RS. This can increase exhaust back pressure with consequent loss of power and load on the exhaust valves - which may explain the sensation of pinging.

Regards,

White Pointer

WP would a person also notice a rise in EGTs?

[marty666]

Nahh diesels do knock
in fact it's in their nature to do it since the ignition timing isn't variable like a petrol engine. Diesel burns much faster than petrol when it does go bang which is why you don't normally inject diesel BTDC

a badly adjusted injector pump will make one knock real bad
This is of course on older mechanical injected engine

The newer EFI engine have variable injection times and durations,

What are you basing that on..... you do know that even old injector pumps advance with rpm and direct injection ones change timing and also number of injections as well.

bp gets its fuel from caltex in SEQ then they add there changes to it. I dont use bp at all as i get better milage out of caltex fuel (i have spent ages testing all the fuels

[Kevaclone]

What are you basing that on..... you do know that even old injector pumps advance with rpm and direct injection ones change timing and also number of injections as well.

That is to keep the ignition timing at around TDC, Engine turns faster but the injection/ignition process speed remains static, if it didn't advance the injection/ignition would fall behind.

bp gets its fuel from caltex in SEQ then they add there changes to it. I dont use bp at all as i get better milage out of caltex fuel (i have spent ages testing all the fuels

BP make most of their own diesel out at Bulwer Island
they get more of their ULP from Caltex

The Ultimate Diesel is based on the normal diesel with an additive injected into the loading arms at the time of loading the truck

Mobil use the same BP diesel these days


But then that all depends on the status of the refineries at the time, shut downs mean a shift in the supply point. BP are about to do a major shutdown at Bulwer Island over the next 3 months

I don't use BP much at all, as I said earlier, it's usually much more expensive than surrounding servos

Of course if you buy Liberty fuel you may just be getting BP as much as you are getting Caltex or Shell(they don't use Neumann fuel)

[cormorant]

Wonder who is distributing this diesel??


http://www.smh.com.au/business/local...0706-zz0e.html