Petrol in Diesel

[lump_a_charcoal]

I used to add 1/2 a L of kero into my old TD lux every few weeks - No ill effects, cleans all the injectors and lines out nicely, and makes it go much better!

[want33s]

I've heard of this before, the kero also absorbs any water in the tank and allows it to gt burnt in the combustion process

Kerosene and water DO NOT MIX...
Go out to the shed and try it..
You must be thinking of Metho to absorb water.. A common trick in petrol tanks.

Jas.

[ajsr]

I've heard of this before, the kero also absorbs any water in the tank and allows it to gt burnt in the combustion process

Kerosene and water DO NOT MIX...
Go out to the shed and try it..
You must be thinking of Metho to absorb water.. A common trick in petrol tanks.

Jas.

AJSR DID"T WRITE THAT SOMEONE ELSE DID
I'M BEING FRAMED JAS

[MightyMouse]

How can petrol cause preignition in a diesel ? Given the fact that injection is timed, how can what hasn't been injected pre ignite ?

I think you just answered this question....

Here....

Yes - ignition delay is a factor with diesel engines, severely limiting theoretical maximum RPM. Petrol addition significantly reduces this delay and so can raise the obtainable upper RPM of a diesel engine

If the petrol reduces the delay then the fuel is burning before it should!!

Ignition delay in a diesel is different to preignition ( which can't happen when there's no fuel ) Igntion delay covers the total time taken for all the injected fuel to ignite.

They are quite dfferent and one cant happen.

[want33s]

AJSR DID"T WRITE THAT SOMEONE ELSE DID
I'M BEING FRAMED JAS

Sorry mate... fixed now.

[AZZA'S HJ47]

very bad to put petrol in a diesel you can get away with it in a old dunger so long as it is not a 60% petrol to diesel mix, however you are going to have done considerable damage to the injector pump and injectors may not show up immediatly but thats not the point. New common rail systems hate even having the slightest amount of petrol present and i can tell you from replacing items on these motors can be upwards of 2grand easily.

Bottom line dont put petrol in a diesel UNLESS you like giving your money away.

[KiwiBacon]

Yes - ignition delay is a factor with diesel engines, severely limiting theoretical maximum RPM. Petrol addition significantly reduces this delay and so can raise the obtainable upper RPM of a diesel engine. This of course assumes the engine is mechanically capable of higher RPM and many aren't.

However the overall situation is far more complex, combustion rates, thermal loads and cylinder pressures change significantly - things that could easily lead to engine damage.

The difference in lubrication for injection components is a also a factor to consider. Differences in normal diesel concern the manufacturers let alone "home brew" fuels.

I'd be very cautious with a road application - especially if reliability was a priority.

Yet funnily enough, fumigating a diesel engine with gas does exactly this, but worse (the gas is present to ignite before the diesel is injected).
Yet there are plenty of people paying good money so that does happen to their engines.

Hmmmm.

[amtravic1]

I had a friend who used to put a litre of petrol into a full tank of deisel at every fill. This person was the most particular engineer I have ever met and would never do anything that would harm an engine. This was a non turbo GQ. The engine ran perfectly for the 6 years he had the car. The motor did not die, unfortunately my friend did.

[MightyMouse]

[quote="KiwiBacon]
Yet funnily enough, fumigating a diesel engine with gas does exactly this, but worse (the gas is present to ignite before the diesel is injected). Yet there are plenty of people paying good money so that does happen to their engines.

Hmmmm.[/quote]

Don't know much about the use of additional gas, however whats the point of injecting diesel at all if the gas is buring before injection ? It also seems counter intuitive - how is the gas combustion timed ? If its burning significantly during the compression stroke the engine won't run. Timed combustion is essential in petrol and diesel engines.

My understanding is that the reduced quantity of injected diesel is used to ignite the gas mixture at the correct time, whilst the introduced gas provides the energy.

But its not my are so could be wrong.

[bazzle]

[/quote]I've heard of this before, the kero also absorbs any water in the tank and allows it to gt burnt in the combustion process[/quote]

Metho "helps" absorb water NOT kero.

Kero still works as it is a lube, petrol thins out the lube of diesel fuel.
You can add a small amount but better to use Standyne or Toyota additive.

Bazzle

[KiwiBacon]

Don't know much about the use of additional gas, however whats the point of injecting diesel at all if the gas is buring before injection ? It also seems counter intuitive - how is the gas combustion timed ? If its burning significantly during the compression stroke the engine won't run. Timed combustion is essential in petrol and diesel engines.

My understanding is that the reduced quantity of injected diesel is used to ignite the gas mixture at the correct time, whilst the introduced gas provides the energy.

But its not my are so could be wrong.

The gas combustion isn't timed, it happens when it happens then gets fed more diesel while it's already happening.

If you run gas into an idling diesel, it pre-ignites and runs like crap. As you'd expect. But the systems out there don't run gas into the engine at idle.
IMO there are some very good reasons why absolutely none of the diesel engine manufacturers run such systems.

[MightyMouse]

Well there our information diverges - just spoke to the Senior Diesel Trainer for Bosch Diesel Systems and he tells me its the injected diesel that ignites the gas/air charge. The diesel quantity is reduced by up to 90% - the gas ( LPG or CNG ) provides the energy.

He also confirmed the wear issues of adding petrol to rotary style injection pumps, concerns re injection pattern, peak cylinder pressure and temperatures, injector tips melting and dilution of lubrication oil in the sump.

Lots of interesting stuff... but its different to your info.

[KiwiBacon]

Well there our information diverges - just spoke to the Senior Diesel Trainer for Bosch Diesel Systems and he tells me its the injected diesel that ignites the gas/air charge. The diesel quantity is reduced by up to 90% - the gas ( LPG or CNG ) provides the energy.

He also confirmed the wear issues of adding petrol to rotary style injection pumps, concerns re injection pattern, peak cylinder pressure and temperatures, injector tips melting and dilution of lubrication oil in the sump.

Lots of interesting stuff... but its different to your info.

We're talking about quite different systems.
Your guy is talking about large generators etc which run mostly gas. I'm talking about the kits sold for diesel vehicles which run a small amount of gas to boost power on top of your normal diesel shot.

I haven't been able to find any information on the large systems running mostly gas (but I haven't looked that hard). So if you could point me in the right direction it'd be appreciated.

[Chucky]

I've heard of this before, the kero also absorbs any water in the tank and allows it to gt burnt in the combustion process

Kerosene and water DO NOT MIX...
Go out to the shed and try it..
You must be thinking of Metho to absorb water.. A common trick in petrol tanks.

Jas.

you're right, I was thinking of Metho

[ISUZUROVER]

Well there our information diverges - just spoke to the Senior Diesel Trainer for Bosch Diesel Systems and he tells me its the injected diesel that ignites the gas/air charge. The diesel quantity is reduced by up to 90% - the gas ( LPG or CNG ) provides the energy.

He also confirmed the wear issues of adding petrol to rotary style injection pumps, concerns re injection pattern, peak cylinder pressure and temperatures, injector tips melting and dilution of lubrication oil in the sump.

Lots of interesting stuff... but its different to your info.

We're talking about quite different systems.
Your guy is talking about large generators etc which run mostly gas. I'm talking about the kits sold for diesel vehicles which run a small amount of gas to boost power on top of your normal diesel shot.

I haven't been able to find any information on the large systems running mostly gas (but I haven't looked that hard). So if you could point me in the right direction it'd be appreciated.

To add to what Dougal said. The "dieselgas" and similar retrofit systems claim you use about 25l of gas to 100l of diesel. You are talking about systems which would use something like 120l of gas to 20l of diesel

[MightyMouse]

No he's on about automotive applications - so we are sort of stalemated.

I just can't see how uncontrolled combustion is going to work.... but there you go.

[ISUZUROVER]

No he's on about automotive applications - so we are sort of stalemated.

I just can't see how uncontrolled combustion is going to work.... but there you go.

Well he is wrong then. Diesel isn't reduced by "up to 90%" in any of the setups I have seen. google them and read the FAQs.

All the setups I have seen are designed so that the engine still runs when you run out of LPG. if you reduced fuelling by 90% on the IP, then...

Diesel gas australia:

What size LPG tank do I need?

Typically, the LPG tank needs to be 1/3 the capacity of the diesel tank. 30l of LPG is sufficient for approximately 100l of diesel. In a 4WD, one litre of LPG is sufficient for 25-30km. Put another way, LPG consumption should be the range of 3-4l/100km. Tanks are available in a variety of sizes and capacities, so we can fit one to suit your vehicle and requirements. See Vehicles section for some examples of tank fittings.

http://www.dieselgasaustralia.com.au

Diesel gas technologies

How much gas does the system use? What size LPG tank do I need?

Typically, the LPG tank needs to be 1/4 the capacity of the diesel tank. 25l of LPG is sufficient for approximately 100l of diesel. Put another way, LPG consumption should be the range of 2-3l/100km.

http://www.dieselgas.com.au

[ISUZUROVER]

And the third option - D-gas:

Whilst our competitors seem to constantly come out with "the latest and greatest" advancements for their pre turbo fumigation systems, the D-GAS System has been injecting LPG AFTER the turbo from the very beginning.

a typical passenger car only requires a 15 to 30 lt LPG reservoir

http://www.d-gas.com.au

Note that the LPG is injected pre or post turbo.

Propane has an LEL (lower explosive limit) of 2.1% in air. Butane 1.8%.

[MightyMouse]

Well I know who I believe and it isn't Google... still each to their own.

[ISUZUROVER]

Well I know who I believe and it isn't Google... still each to their own.

That info is from the MANUFACTURERS of the diesel LPG systems. So I would be more inclined to believe them than some 3rd party guy, albeit from Bosch.

His info is contradictory. He says diesel use is reduced up to 90%, but the LPG only ignites when the diesel is injected. You cannot have both.

If we take the 3L/hr LPG consumption figure from the kit manufacturers, and assume a 4L diesel, that works out to somewhere between 0.5-1.5% LPG in the intake air. This amount is BELOW the lower explosive limit of both propane and butane, so he would be correct! The LPG only burns when the diesel is injected.

However if we take his value (90% diesel reduction), then that would INCREASE the LPG levels to above the LEL. So the LPG would cause preignition.

[marin]

Not sure why, but i seem to remember figures of 15% lpg for better economy (simply getting a better % burn of diesel in combustion chamber) and up around 30% LPG for out and out power increase.

And I think it says somewhere that the LPG is used as a catalyst for the complete diesel burn...

marin

[KiwiBacon]

Read this:

http://www.eng-tips.com/faqs.cfm?fid=1147

[zagan]

been told by the australian tech rep for lamborgini tractors that the go in turbo diesels paricularly is to use a small amout (a litre or two) of kero in a full tank. Apparently petrol runs too hot and causes preignition in diesels which is hard to pick in a normally rattley engine its supposed to be worse in turbos as they need the higher octane.
kero supposedly does a good job of removing carbon and tarnish buildups and runs only a little hotter.
lamborgini recommend it every 3rd to 5 th tank also good to stop iceing of fuel

Ive been useing it in my canter truck for two years no dramas
hope this helps
cheers andrew

How can petrol cause preignition in a diesel ? Given the fact that injection is timed, how can what hasn't been injected pre ignite ?

Also diesel systems use cetane rating not octane - the things are supposed to detonate - it their operating principle

I'm not going pro or con, but some of the info seems wrong.

Well Petrol has a lower ignite point than diesel I think 90 octane ends up being around 150C is auto ignite where as 50 Cetene is around or above 200C before the diesel ignites.

Also your squirting pressured fuel not simply pumping in fuel so this pressure could make the fuel hotter in the same way as compressing air will cause it to heat up.

Then once you do the squirt... it's going straight into a 200C+ cylinder so you'll be well over the ignite point of petrol, this could also melt the injectors too or should I say the needle in the injectors.

Depends on what sort of heat the injector will handle, I guess as well.

It's the like those cars that have a poor tune and it's cracking and popping all the time, that's pre/post detonation so they are damaging their motor every time that happens.