MM5AHO
Well-known member
I thought " DERV" was the vehicle not the fuel? (Diesel Engined Road Vehicle)
Is paraffin the same as diesel?
- Thread starter GODOT
- Start date
alanabnala
Member
Sigh!
Right.....!
I really can't be bothered, but I'll make the effort.......
Under NORMAL circumstances petrol will not detonate due to compression alone. Put NEAT petrol into a diesel engine and it will not ignite. Unlikely you will ever put NEAT petrol into a diesel as there is usually some diesel fuel left in the tank for it to mix with. Dependant on the "mix" of petrol to diesel, it will either not fire at all, or run perfectly ok with no side effects and every variation in between.
When petrol does ignite due to compression (and heat) it is know as detonation (not pre ignition, that is a different phenomena). Pinking, pinging, knocking are all names given to the sound you hear due to detonation.
Detonation occurs AFTER the plug has fired, so definitely not “pre ignition”. I won’t go into the causes of detonation, there are many things that can cause it, suffice to say that the normal burn process is incomplete before the end stage of gas detonates. As the A/F mixture is ignited by the plug the flame front advances away from the plug. During the burn process temperature and pressure increase in the cylinder. Detonation occurs when this build up of temperature & pressure exceed the octane rating of the fuel and the final un-burnt gasses spontaneously ignite. It is this sudden pressure spike that causes the sound you hear.
Detonation is not necessarily destructive to engines, but it does cause increased cylinder temperature. The increased cylinder temperature can lead to pre ignition, which is fatal to all engines, no matter how strong they are, very quickly (we’re talking seconds..!) Pre ignition (as the name suggests) is when the A/F mixture is ignited BEFORE the spark plug fires. Sources for this can be the plug itself becoming too hot, carbon build up, a thin edge on the cylinder head etc etc… Pre ignition normally occurs during the induction stroke, so as the inlet valve closes, before the compression stroke has really started, you already have a pressure and heat build up, which the piston now tries to rise against. Complete engine failure occurs moments after pre ignition starts in EVERY case.
You can see now why I couldn't really be bothered, and I have only skimmed over the topic.....!
Right.....!
I really can't be bothered, but I'll make the effort.......
Under NORMAL circumstances petrol will not detonate due to compression alone. Put NEAT petrol into a diesel engine and it will not ignite. Unlikely you will ever put NEAT petrol into a diesel as there is usually some diesel fuel left in the tank for it to mix with. Dependant on the "mix" of petrol to diesel, it will either not fire at all, or run perfectly ok with no side effects and every variation in between.
When petrol does ignite due to compression (and heat) it is know as detonation (not pre ignition, that is a different phenomena). Pinking, pinging, knocking are all names given to the sound you hear due to detonation.
Detonation occurs AFTER the plug has fired, so definitely not “pre ignition”. I won’t go into the causes of detonation, there are many things that can cause it, suffice to say that the normal burn process is incomplete before the end stage of gas detonates. As the A/F mixture is ignited by the plug the flame front advances away from the plug. During the burn process temperature and pressure increase in the cylinder. Detonation occurs when this build up of temperature & pressure exceed the octane rating of the fuel and the final un-burnt gasses spontaneously ignite. It is this sudden pressure spike that causes the sound you hear.
Detonation is not necessarily destructive to engines, but it does cause increased cylinder temperature. The increased cylinder temperature can lead to pre ignition, which is fatal to all engines, no matter how strong they are, very quickly (we’re talking seconds..!) Pre ignition (as the name suggests) is when the A/F mixture is ignited BEFORE the spark plug fires. Sources for this can be the plug itself becoming too hot, carbon build up, a thin edge on the cylinder head etc etc… Pre ignition normally occurs during the induction stroke, so as the inlet valve closes, before the compression stroke has really started, you already have a pressure and heat build up, which the piston now tries to rise against. Complete engine failure occurs moments after pre ignition starts in EVERY case.
You can see now why I couldn't really be bothered, and I have only skimmed over the topic.....!
Heckler
Active member
"Put NEAT petrol into a diesel engine and it will not ignite"
What planet you living on?
Diesels will burn any type of oil that will go thru the injectors and pump. whether it does the engine any good that is another matter! They will also run on gas, in fact one could say that all internal combustion engines are gas engines, they only difference being in the manner in which they turn "oil" in to a combustible gas. Petrol engines use carbs or injectors to atomise the fuel, diesels use injectors to atomise the fuel.
Stu
Last edited:
alanabnala
Member
Obviously not cloud cuckoo land where you live! Why don't you ask the 1000's of people, how far they got after filling their diesel vehicle up with petrol ? Or if they have it wrong, how about the AA or RAC who have to recover the vehicles? ? Oh, but if they've got it wrong too then you must be right! Well done for putting me right on that one!
Heckler
Active member
I dont need to ask anyone, I used to do this for a living and I know what I am talking about. The reason peeps have to call the breakdown services is that petrol does burn in diesels, unfortunately it burns in a manner that causes damage to the engine. Modern engines have sensors that detect the uncontrolled burning of the wrong fuel and shut the system down to avoid damage.
Stu
SailBobSquarePants
New member
I just wanna know...
I/m just curious as to where the OP found paraffin / kerosene in a PUMP to get 30 litres??
The last time I saw a kero pump it was in my grandfather's auto fuel station, where he had an huge rectangular steel tank, and a giant handpump on top.
Now all I can find is paraffin in £5 plastic white containers in hardware stores...and I doubt the OP poured those into his fuel tank.
I/m just curious as to where the OP found paraffin / kerosene in a PUMP to get 30 litres??
The last time I saw a kero pump it was in my grandfather's auto fuel station, where he had an huge rectangular steel tank, and a giant handpump on top.
Now all I can find is paraffin in £5 plastic white containers in hardware stores...and I doubt the OP poured those into his fuel tank.
alanabnala
Member
Perhaps the key here is "used to do this for a living".......
I do this for a living and have done for the past 30 years, but like I say, you know best mate!
AngusMcDoon
Well-known member
There are still one or two in deepest darkest rural Wales that have a pump. There's also the oil company who do all the DIY shop prepacks in Rhuddlan who sell in in drums or will fill yours, but that's not much good for the darn sarf lot.
vyv_cox
Well-known member
Why, have the combustion chacteristics of petrol changed?
A few minutes with Google tells me that diesel engines will most definitely run on petrol but, as Stu rightly says, not for long.
ProDave
Well-known member
Interesting debate.
My very first car, a MK1 Ford Escort 1300, used to often "run on" for a few seconds when you turned the key off. So clearly it was igniting the fuel somehow without a spark.
People told me it was "pre ignition". But unlike what you say, it never caused ill effects (apart from the engine did not always want to stop) and it did not destroy the engine in seconds.
I had the car for two years like this, and it went on for at least another 2 years with the next owner.
badman
New member
Thanks for all the info guys, when I read stuff like this it reminds me keep my wits about me on the forecourt at the filling station.
badman
New member
Same as my Rover 2000 sc I used to stop with it in gear then take my foot off the clutch to stop the enigne ran it like that for a couple of years, I was told it needed a decoke.
grafozz
Member
running on
I , like badman , also use the "stall " method to stop the engine in my old Healey , and have done for years . it seems to have done it no harm ? I always put it down to a big engine in a small space where there is a lot of heat build up ?
It has had several different piston/ head / compression configurations but always runs on after the ignition is switched off . I was informed a long time ago that this running on is bad for the engine and should be arrested immediately. I seem to remember that if allowed to continue to run on it could actually break the crankshaft !
So ,can any of you "fuelers " please tell me what is really happening in there ?
I , like badman , also use the "stall " method to stop the engine in my old Healey , and have done for years . it seems to have done it no harm ? I always put it down to a big engine in a small space where there is a lot of heat build up ?
It has had several different piston/ head / compression configurations but always runs on after the ignition is switched off . I was informed a long time ago that this running on is bad for the engine and should be arrested immediately. I seem to remember that if allowed to continue to run on it could actually break the crankshaft !
So ,can any of you "fuelers " please tell me what is really happening in there ?
RichardS
N/A
My Dad was in the REME during the war working on tank engines.
I think that these were/are diesel engines and he used to tell me that they could run on anything combustible as fuel supply was unreliable at the front - he reckoned that they tried engine oil, cooking oil, kerosene, paraffin, anything and I'm sure they must have also tried various grades of petrol
Onviously these were not modern engines and probably not even standard diesels for the 1940's but, if I'm right, this would seem to suggest that, in principle, a spark is not required for ignition.
Richard
I think that these were/are diesel engines and he used to tell me that they could run on anything combustible as fuel supply was unreliable at the front - he reckoned that they tried engine oil, cooking oil, kerosene, paraffin, anything and I'm sure they must have also tried various grades of petrol
Onviously these were not modern engines and probably not even standard diesels for the 1940's but, if I'm right, this would seem to suggest that, in principle, a spark is not required for ignition.
Richard
Cruiser2B
Active member
Heckler
Active member
I retired, so that cheap shot doesnt work.
If youve been doing it for 30 years you havent learned much along the way!
Stu
DownWest
Well-known member
Not sure, but, I thought most army stuff was petrol in WW11. Junkers ran some diesel aero engines (JU 88?) Any body?
A
A
Heckler
Active member
The garage up the road from us sells "kerosene" from one of his pumps, (he has two garages and the other sells "red" from the pump) I asked him about it and he said it was 28sec oil, so in fact it is heating oil, quite why anyone would buy heating oil in a container?
Perhaps the local farmers have worked it out that their "tractors" will run ok on it?
Stu
Davy_S
Well-known member
The Greek taxi drivers certainly know that their taxis will run on it! At half the price of diesel, it is worth the risk
Heckler
Active member
The running on is caused by something glowing hot in the combustion chamber, thats how glow plug engines in model aircraft work, an electric glow pin to start it and then the pin is disconnected from the battery BUT continues to glow from the heat of the combustion.
In the olden days the need to decoke every year was driven by the build up of carbon from the less sophisticated lube oils and fuels and the relatively poor control of the mix of fuel and air.
The hot spot can also be a piece of a rough head casting
Stu
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