Help:research on mixing up diesel and petrol when filling up
 

Ok, so here's the deal. I'd like to know more about when let's say you tank petrol in a diesel car or doing the opposite.

What creates a bigger problem. I'd like some technical info on the subject, what happens and which things have to be done to fix everything.....

I know Zfrk will probably know the answer to this....anybody else????

Thx, I need this infor for an article I'm doing...

You have to completely drain the fuel system. I don't know the chemical reasons, but its a very expensive mistake.

Diesel is made to be combusted through heat and compression. Gasoline engines don't have the compression needed to make the air/fuel mixture combustible, nor can you generate the heat neccassary.

The theory behind diesel combustion is pretty much detrimental to a gasoline engine as the detonation causes and is caused by, increased cylinder temperatures which can melt pistons, burn valves and blow apart piston rings. Back when carburettors were being used, if the mixture was too lean, or the engine was running too hot, on shut down, the fuel that had been drawn into a cylinder would detonate and keep the engine running. While this happens, it sounds like a diesel engine and the only way to stop it would be to either block the engine by putting the trans in gear (manuals only) or by blocking off the air intake so that no air would be allowed in and the engine would choke out. This hevily damages the engine if allowed to carry on for an extended amount of time.

Generally when diesel is mixed with gasoline these days, the car wont run or will run like ass. In any event, as graywolf pointed out, the fuel tank has to be drained and refilled with fresh gas. after the remainig diesel is pushed out of the lines the car will begin running normally. Engine damage can occur but only in severe cases. If allowed to happen long enough, the parafin content of the diesel fuel may build up in the intake, cylinder head, and exhaust systems after it is burned off. This could be very costly since these parts usually require a few hours to remove, clean and reinstall.

When the tables are turned in a diesel engine and gasoline is added, it causes the engine to "ping" or pre-ignite (also known as detonation) because the gas is more volatile than the diesel. So again, the engine will either run like ass or not at all. With diesel engine components made for the brutal conditions they endure, i don't think the risk of engine damage is quite so high. But again, draining and refilling the system is needed.

i have info around here somewhere about flamefront temps and speeds during normal combustion and detonation in gas engines, but i'll have to dig through my notes to find it. My knowledge of diesel is pretty limited though so if there is anything beyond what i've mentioned or if i'm not 100% accurate, i apologize. (you have a fact checker, right? :mrgreen: )

thx for the very usefull info.

still, if anybody has anythig to add, it would be great.

thx again :D

/* shaking head ...

Boy Mr. Z ... that's a very amateur and fact-weak response. I expected better.

Here's my fact rich and insightful response as agreed upon by David Hobbs

Diesel fuel in Gasoline engine = Gasoline in diesel engine = Ka-blam-o :wink:

Zfrk - the BMWs have something that detects if petrol is going into the diesel engine, don't they?

That prevents the fuels mixing and is cheaper to replace - am i right? I'm not sure on this :?

Honestly, i dont know. We don't have the diesels over here yet so they don't teach us anything about the diesel technology. Given the tech they have now though over here, i would think that they would have something in the fuel tank measuring the conductivity of the fuel, much the way the oil sensor works. I would think that diesel and petrol have different conductivity levels. I know that the semi-trucks and heavy duty pickups here that are diesel powered are able to detect water in the fuel, so why not petrol contamination :bah:

:roflmao: :roflmao: :roflmao:

Beautifully put :lol:

Hmmm.. I was torn between whether it was the flash point or the Density.
Learn something new every day.

^ it's anybodies guess really. But i'm going to be in Atlanta for New Engine Technology and E90 training in June. By then maybe they'll have added the diesel technology.

hmmm....that could be possible as well...I'll have to ask my roomate when he gets back. He's a Mercedes tech and they've got a diesel engine over here, so he should know the answer to this.

Ok, i asked my roomate what happens and he confirmed that diesel engines "detonate like a motherfucker" with regular gas mixed with the diesel. I also forgot to add that after draining the fuel in a gas powered car, you need to replace the spark plugs too because they'll be fouled horribly.

I also found the notes i took on the anatomy of preignition:

Under normal combustion, generally, spark occurs and the burning of the air/fuel mixture begins at around 8 degrees BTDC (i will explain this at the bottom of the post for anyone who is confused). This burn is called the flame nucleus.

From here, the burn begins to hatch out. Flame fingers travel across the cylinder burning the mixture.

At 10 degrees ATDC, the flame has reached 5,500 degrees farenheight and is in full burn. This is the propogation stage of the burn and where the maximum thrust is produced. Flame front speed is between 300 and 400 MPH.

By 23 degrees ATDC, the burn is complete. The entire process has taken approx. 3ms.

Pre-ignition is generally caused by increased cylinder temps due to lean mixture, over-advanced ignition and of course bad/contaminated gas.This conditon will double flame front speeds to 700-800 MPH and jack up cylinder pressures and temps. because the combustion process has been moved further from the opening of the exhaust valve.

According to the article in the Jan. 04 issue of F1 (The Beast Inside) the normal load on a piston is 8000Gs when it changes direction at the end of it's stroke. Now this is in a 3L V10 spinning at 18K RPM, so it's a little more than what your engine experiences :wink: but the theories are still the same.


Now for those who may be a little lost on what BTDC and ATDC means:

Top Dead Center (TDC) refers to the upper most limit of the piston's travel in the cylinder before the crankshaft begins pulling it back down. BTDC refers to Before Top Dead Center, the piston is still travelling up, and ATDC refers to After Top Dead Center, the piston is now travelling down.

but what happens when you add in the new corn based fuel E85? adding that into either tank? also what about propane and Kero.? what don't we use that? I know Kero. is cheap. and some companies run on propane. but why not the major usage? :|

thx man, I really eppretiate the effort! You helped a lot 8)

Did the article today and the boss was pleased, so thx again 8)

naaah!! now you must give Z a part of your salary because he made your research and 90% of your article :P

I don't think E85 is that widely enough used to really know the effects yet. I know there aren't any filling stations here, so we haven't seen any effects yet. I don't really know much about E85 either :?

I know there were alot of Propane/CNG powered vehicles in Phoenix, but that was due to a badly executed plan to get people to buy them. The Arizona gv't was giving rediculous rebates to people who had there cars converted to run on either of them. So there were people picking up GMC Youkon Denali's for like 35 grand and other gas guzzlers. The downfall was i think there were 5 places around the city that filled the cars. Apparently it wasn't as easy as going to the propane tank filling station and plugging in.

Why they aren't as popular i think is the hassle of getting the car converted to run on it and the cost is higher than regular gas IIRC. So you pretty much pay more to pollute less.

No problem man. Happy to help 8)

In terms of vegetable oil, putting it in a gas engine is a nono.. For example John Deere just released an announcement to this effect about there tractors. The leave deposits in the injectors and chamber since they dont fully burn.