could a diesel run petrol if you put in spark plugs?

[Percyhahn]

i was having a debate with someone last night, we was wondering if you was to put spark plugs in a diesel, would it burn petrol ok?
simplistically, i would say its possible, on modern ones anyway because a common rail is a diesel form of fuel injection is it not? aqnd by putting in sparks, your changing the atmosphere to a spark, rather than a warm environment from the glow plugs however i'm sure there's something we didnt think of, and google didn't bring up anything, so wondered what people on here thought?
btw dont worry, neither of us was thinking of actually doing it

 

[RuSZ]

Isn't the compression differnt as well?

 

[popsprocket]

Not only the compression but diesel fuel delivery systems run at a MUCH higher PSI.

 

[Noddy]

A diesel engine has higher compression as it uses this to cause the heat to ignite the fuel/air mixture. Because of this extra compression the injector pressure has to be higher to overcome this.
What happens is that the compression heats up the fuel/air mixture untill it reaches its ignition temperature at which point detonation occurs. This should be just prior to TDC (this allows for the compression to build up as the piston passes TDC) and the piston is then forced down.
If you put petrol in this detonation occurs earlier as petrol is more volatile. This causes pinking which damages the piston crowns. Also petrol burns at a higher temperature causing the engine heat damage as the cooling system isnt designed to cope with it.

 

[craigb244]

no reason why not...

the compression will need to be lowered.
diesel injectors blocked off.
petrol injectors fitted into the intakes. (and an ecu capable of running them)
throttle body fitted (otherwise you will just get full throttle)

that would make it run...
But run well?... no
diesel pistons and heads have strange mixing patterns and areas cast into/onto them... petrol would not agree with it much.

diesels rev much much lower... a petrol engine of the same size most likely be making most of its power on and after the red line of the diesel engine....

petrol engines run much much hotter then diesel

diesel fuel is an oil... diesel engines are designed with less oil supply to the bores and maybe even top end then a petrol because the fuel itself works as a lubricant

so chances of it self-destructing after a short time is likely.


has a diesel that runs on petrol ever been made?... yes ... old school tractors used to start on petrol before been switched over to diesel.

 

[Ffoxy]

What?
And exactly how would the sparks be created & timed?

I vote No... No way... Not at all... Ever...

 

[Percyhahn]

thanks people. its amazing how at 1 in the morning you dont think as technically as you do in the day lmao, not one of them crossed our minds.
thanks people lol

 

[craigb244]

how many drink did you have lol

 

[chaos]

diesels rev much much lower...

IIRC the reason for that is because you can only compress the air/diesel mixture so fast.

 

[David C]

What?
And exactly how would the sparks be created & timed?

I vote No... No way... Not at all... Ever...

It has already been done.

Someone converted a 2.4 JTD to Petrol.

 

[Davren]

It has already been done.

Someone converted a 2.4 JTD to Petrol.

You could convert a wheel-barrow to petrol if you added enough parts.

 

[Radlet6]

It has already been done.

Someone converted a 2.4 JTD to Petrol.

One word - Why?

Yes in theory diesels will run petrol - its called the big bang theory.

Back in the 70's we used to put petrol in the diesel fuel to stop it waxing up in cold temperatures during the winter. You could actually get away with as much as 5% without trouble. Thing is if you put too much in the engines would start to race and couldn't be switched off. You just had to sit there and wait for the pistons to melt. I wasn't that soldier, but I sat (with a cup of coffee and a fag) next to the guy who was.

 

[wegi]

Any diesel can burn petrol... it just runs super rich and eventually kills it.

However, putting diesel into a petrol engine is suicide.

 

[craigb244]

IIRC the reason for that is because you can only compress the air/diesel mixture so fast.

well... you are not really compressing air and diesel... just air... diesel is injected into the hot compressed air. the timing of the injection is more or less the same as what the spark timing in a petrol engine does.

reason for them reving so low is that the flame front speed (how fast the fuel burns) on a diesel is very slow when compared to petrol

also on a petrol you can have lots of advance on the ignition to keep up with very high piston speeds. where a diesel... even if injected early on in the cycle, if the compression is not high enough there wont be enough heat to start ignition... so at high rpms the slow flame front will be just chasing the piston and not pushing it.

luckily for diesels the fuel has quite a lot more energy for volume than petrol. also it burns cooler so more energy used to push the car rather then make heat.
high compression means better efficiently/more power


personally... im not keen on them lol

 

[Radlet6]

well... you are not really compressing air and diesel... just air... diesel is injected into the hot compressed air. the timing of the injection is more or less the same as what the spark timing in a petrol engine does.

reason for them reving so low is that the flame front speed (how fast the fuel burns) on a diesel is very slow when compared to petrol

also on a petrol you can have lots of advance on the ignition to keep up with very high piston speeds. where a diesel... even if injected early on in the cycle, if the compression is not high enough there wont be enough heat to start ignition... so at high rpms the slow flame front will be just chasing the piston and not pushing it.

luckily for diesels the fuel has quite a lot more energy for volume than petrol. also it burns cooler so more energy used to push the car rather then make heat.
high compression means better efficiently/more power


personally... im not keen on them lol

Personally I love them - have done since I had Citroen CX diesel as a company motor. On the Croma I can set the cruise control to 75 and get 46 to the gallon; and the torque when you boot it.

That said, I'm not adverse to petrol engines so long as they have at least 6 cylinders. I am still in love with the sound of my S3.

 

[Ffoxy]

It has already been done.

Someone converted a 2.4 JTD to Petrol.

I dont want to be pedantic but.....

Link or its untrue...
Anything CAN be converted to anything...
But...
Why would you?
What did this fabled "someone" pay for the privilege?
How did he recover the work costs?

And for the Posters who have not read the Thread properly...

This is about CONVERTING a compression ignition motor to a SPARK ignition motor... NOT accidentally adding petrol (or adding some petrol deliberately...)

Take 30 mins & consider the proposition... Definitely NOT WORTH IT on a modern CI engine...

 

[craigb244]

maybe he means someone put a petrol engine into a car that had a 2.4 JTD?

 

[Big Black Stilo]

Any diesel can burn petrol... it just runs super rich and eventually kills it.

However, putting diesel into a petrol engine is suicide.

modern petrol engines its suicidal, but older cars, say, an none injected capri, can run on a diesel/petrol mix. it just smokes like dot cotton

as for petrol in a diesel, the mrs put 7 litres of petrol in our 306hdi. i brimmed with diesel and it ran, but a month later fuel lines became a bit damaged and im still getting fuel leaks now. petrol destroys rubbers and plastics not suitable for it

 

[David C]

I dont want to be pedantic but.....

Link or its untrue... ...
This is about CONVERTING a compression ignition motor to a SPARK ignition motor... NOT accidentally adding petrol (or adding some petrol deliberately...)

yep:

Read Here

 

[The Beard]

Not quite the same thing, but about 10 years ago, Scania converted a number of 11 and 12 litre diesels to spark ignition in order to run on Luiquified Natural Gas. This was designed for supermarket chains who had to deliver into urban and suburban areas (mainly in London) where the emissions levels of normal diesel trucks were too high.

These were older vehicles and had the engines re-built as part of the process. This was considered to be a cost effective solution as the alternative would have been a fleet of the latest trucks at considerably higher cost. The LNG route would have provided emissions below those envisioned for many years.

I'm not sure if the project was taken much further as the gas would have had to be stored at transport depots as there wouldn't have been enough fuel stations on the public roads prepared to stock it.