DDK - Die Deutschen Klassiker

In a moment of madness I accidentally put around 20 litre of diesel in my 3.2 - having realised my mistake I topped it up with another 30 litres of unleaded hoping that it would dilute it enough to get me home.

Apart from a rough idle, it ran OK and I'm now safely at home, my question is do I need to drain the fuel system, or as proven on Fifth Gear just slowly drive it out

Cheers

Hello Beaky.

You do know the CR of the 3.2?

Dump the lot and if you get away with it breathe a sigh of relief!

Kind regards
David

Dump the lot ASAP ... but what's the relevance of the compression ratio question ?? (probably be as well to change the fuel filter too ... not sure why I say that , just a residue thing maybe ?)
Consider yourself lucky if that's the end of it !

Hello, Cortina.

The CR is vital..an old vw with a cr of iirc 7:1 will just about run on paraffin..with a octane number of nix..
but the higher the cr, the higher the octane needed to prevent preignition and total engine destruction..

Kind regards
David

don't worry about preignition with diesel in a petrol engine
Diesels run at CR's from 14:1 up to 24:1, since they need self ignition

so diesel fuel , won't blow up a petrol engine
it will not run though, and i doubt it will dillute enough with a 50/50 mix

empty the tank before you end up stranded

Good ... glad someone else is on the same wavelength as me !!
We assume the patient has recovered ????

Good point..I agree on that.

ie it will nto run on delisel at all..

But I think we are not talking about that case are we?

What we have is a mixture amounting to a veery low-octane petrol, which most definitely will run!

Now my submission is that this is a recipe for detonation.not pre-ignitio, nor dieseling..

My limited understanding of detonation is that the spark initiates the burn normally, but as the energy builds, the falme front spreads too slowly to burn the mixture progessively, and the heat build causes uncotrolled, literally explosive, detonation of the unburnt mixture distal from the spark.
This is astonishingly destructive..nothing at all like the knock or pink you sometimes hear with hot engines and crap petrol at open throttle and low rpm.tho' that's not good.

There is a lot of evidence about this: one of the main reasons why race engines are freshened regularly is to avoid oil in the chamber: most modern very high performance engines run crankcase vacuum to keep the oil down ..when this leaks and the preassure allows chamber oiling, they destruct in short order.

I'd be interested to find any links dicsussing this..I'll look when I have time..

Kind regards
David

diesel has a high octane
petrol has a low one

if anything , that 50/50 mixture will have a higher octane then even racing fuel or aviation fuel

onlyway to find out is finding out what octane diesel has ( it's hardly ever documented , so i wouldn't know )

and then you add both , devide by 2
that formula is correct as far as i know, something in the 911 performance handbook by Bruce D. that covers this

anyway , i'm pretty sure that Diesel , does not lower the octane number of petrol , it's the other way around , it raises it to the point where you can't even ignite it with a spark plug.

Hello there.

Octane is not the same as low ease of ignition: octane decribes literally the content of octane, ie the 8-carbon hydrocarbon.

Which was the original low-detonation petrol.

Of course many other compounds also have high antiknock propeties..xylene for example..

Engine Oil has a low ignitabilty, but produces impressive detonation..trust me on that!

Kind regards
David

davidppp wrote:Hello there.

Octane is not the same as low ease of ignition: octane decribes literally the content of octane, ie the 8-carbon hydrocarbon.

Which was the original low-detonation petrol.

Of course many other compounds also have high antiknock propeties..xylene for example..

Engine Oil has a low ignitabilty, but produces impressive detonation..trust me on that!

Kind regards
David

engine oil yes, but diesel ??
sure , it's both oil, but additives and what not

i mean , diesel engines all run high compression
a lot higher then petrol, if it were so easy to ignite the diesel mix
they would be able to run a lot lower compression, lighten the heck out of the diesel engine blocks, whereas now they are heavy as hell , because they have to make it a lot stronger due to high cr

whether it will run or not isn't really the point. If it was a £200 knacker that you used for taking your grass cuttings to the tip then experiment with it running on diesel.

But this is obviously your pride and joy 3.2 litre Porsche that is worth 15K+ Bit of a no brainer, just dump it and lose £50-60 in fuel and filter, surely the most sensible and cheapest option.

Sorry ... I couldn't resit this:
I thikn it's tiem to stpo this threda ... before it gest completeyl out of contorl
Excuse typing , I didt'n have time to chekc it !

Epilogue,



The tank was fully drained this afternoon, access gained via the sender unit under the bonnet, drainage by way of a handheld drill powered pump.



A full tank of fresh Optimax plus a bottle of injector cleaner has been added and I will be clocking up the miles this weekend, once through a full tanks worth I'll change the filters.



First I let the car idle for some 5/10 minutes to clear as much of the diesel still remaining in the pipework as possible, the car did smoke some and the idle was erratic, but soon settled down, this was followed by steady 30 mile cruise up and down the A10, car now seems to be running fine, looks like this time I got away with it

Best thing you could have done - hope you get away with no damage

Stu