Just curious about Gasoline to Diesel conversions. 1

[TZSiR]

I've seen one in person, but at the time I wasn't interested enough to check it out.
I'm curious is to if anyne has any experience with this? If so was it done with the stock components or did it require extensive modifications? Basically I'm looking to convert a port injection engine into a diresct injection, but I have no idea where to even begin looking for this info... Yes I'm aware of the problems that occur from high sulfur contents of pump-gas. That's why I plan on running something like an alcohol.

 

[franzh]

I'm sorry, but your post makes absolutely no sense.

Franz

 

[TZSiR]

Sorry, I was up a little late so I probably wasn't making much sense even to myself.

I've seen a gasoline engine converted to a diesel with a fuel injector installed where the spark plug belongs normally. I was curious if anyone knew anything about this. I'm looking to do this conversion with a Honda engine, but instead of using diesel for fuel I will be using alcohol if at all possible. Opinion's on whether this is a accomplishable task, or not is always appreciated.

 

[TheBlacksmith]

Diesels are typically much heavier than the same size gas engine to withstand the relatively higher compression ratios and firing impulses aka, the converted gas engine will fail quickly, ala the ill fated Olds/GM 350 CID conversion of the '70's. Unless your goal is to deplete your bank account as quickly as possible, while walking to the parts store frequently, my advice is to find another project.

Blacksmith

 

[vinodkarthik]

I think the Blacksmith has not properly understood the problem. If I am right, you are trying to convert a gasoline engine to an alcohol engine without altering the compression ratio. So, there is no question of higher cylinder pressures causing engine damage in this case.

However, where I see this modified engine fail, is in the area of mixture formation. This is of course assuming that you would be using a stratified mode of mixture generation, which would be advantageous with regard to throttling losses. To accomplish proper mixture formation, you would require extensive revamping of the piston and combustion chamber shape.

Also, alcohol would require a different fuel metering system, due to its lower calorific value. Another thing you have to keep in mind is that alcohol has poor ignition performance and you have to ignite it with a spark plug afterall. So, you will be unable to simply replace the spark plug with injector.

Therefore, though I would not recommend it if you are short on time, it would be a good acomplishment if you do manage to do it. All the best!!

 

[Metalguy]

vinodkarthik,

Uh, if he screws an injector into the spark plug hole, where does he screw in--ah, never mind.

 

[TheBlacksmith]

I guess the title Gasoline to Diesel confused me.

If you want to burn alcohol, just fill 'er up and adjust the current injection system (injector size and/or pressure and/or program) to inject enough alcohol to account for lower BTU value.

If you want direct injection, figure out how to fit the injector into the head along with the current intake valve, exhaust valve, and spark plug.

If you really want a diesel cycle aka compression ignition with engine power and speed controlled by the quantity and timing of fuel injected into the cylinder, I stand by my first post.

Blacksmith

 

[franzh]

Actually, I think we are reading the post incorrectly. He states "Gasoline to Diesel" conversion. The diesel cycle does not use spark plugs but compression generated heat to ignite the air and fuel mixture. You cannot use alcohol as a diesel cycle fuel. Also, I think you did see the Olds diesel fiasco, it was a dismal failure.

Blacksmith is correct in his first reply, along with Metalguy. How deep are your pockets? Its easier to use alcohol as a spark ignited fuel engine, them adapt the injection curve to suit the particular fuel. Also, alcohols are corrosive to certain engine components which is why it has not caught on in big numbers. Stainless steel pumps, lines, tanks, injector bodies, fuel rails, and so on.

Franz

 

[Rob45]

The important problem with using alcohol in the Diesel cycle is the very low cetane rating of alcohol fuel.
That is, it is very resistant to compression ignition.
The Brazilian government has sponsored a greaty deal of research into using alcohol in Diesel-cycle engines, as any web search will turn up, and they have concluded that, for straight alcohol, "Research has demonstrated that it is not possible to establish this substitution program in diesel cycle engines."
They have run blended fuels with alcohol contents as high as 11%, but they point out there are safety concerns in the storage of such blends due to their having a significantly higher vapor pressure than does straight Diesel.

Finally, no discussion of dismal failures among "converted" SI engines would be complete without mention of the VW Rabbit Diesel of the '70's.

 

[TZSiR]

Thanks that's the info I was looking for. I was trying to figure out how to ignite the mixture, but I couldn't without some drastic reshaping of the head, and accompanying materials. I wanted to use this in a racing situation where 1/4mi blasts are all that would be ran, but I guess I have to get a custom head made to do this.

Sidenote ~ This was an effort to maximize the fueling quality entering the cylinder, and to help improve the ratios on a turbo application for highest mean output. Sorry for the confusion, but I figured that the title would be a hint at what I was trying to get at.

 

[evelrod]

TZSir, it surely would have helped us if you had taken the time to post your last in the FIRST place!!!!!!!
As it stands, I will stick with Franz's first post as being the DEFINITIVE of this thread. I think in future threads a bit of forethought would be greatly appreciated by the very knowledgable engineers that have taken their time to try to decript your posts.

Rod

PS I vote to give your star, Blacksmith, to FH. LOL

 

[TZSiR]

Sorry I don't speak English very well so I don't really know how to say things clearly the first time. I knew what I wanted to say, but it didn't come out right at all. Being tired doesn't help either. Yes there are some very knowledgable engineers here, and I hope I can learn as well as contribute to this forum.

 

[Metalguy]

Your English is orders of magnitude better than my Italian, so don't sweat it. You're doing great. Most of us here just need things spelled out real simple!

 

[evelrod]

Your English is just fine but most of us "get the hint" only when it is accompanied by a "sharp rap with a hammer"!
I ment no disrespect in my last post even though it does look rather severe when you see it in print.

Rod

 

[TheBlacksmith]

Rod -

"Sharp rap with a hammer" - are you setting the timing on the BBC motorhome again without a distributor wrench?

Blacksmith

 

[evelrod]

I am sooooooooooooooo offended!

Rod me after a 1st place Sunday and enjoying our 85 degree weather. Na, na, na na na!

 

[Metalguy]

Well, Connie Grats!

 

[Dzldood]

This is kind of a funny thread... I actually worked for a company that did just this thing... We started with a Subaru 3 liter, 6 cylinder gasoline engine and converted it to run on JP-5, or kerosene. We used a relatively low compression ratio (13.7:1), along with a EFI diesel injector in the spark plug hole. The cylinder head was a pent roof type so fuel/air mixing was pretty bad and therefore power output was down (~100 HP for the engine).

As for controlling cylinder pressure (90 bar max for engine), it is amazing what a pilot injection (a small squirt of fuel before the main injection) will do for you...

Kevin

 

[Rob45]

Here's my nomination for "silliest thread of the year".

Is there ANY competition?

 

[Nothegger]

Ok, I don't know about these fiascos, so could you tell me what is the weak link in a gas engine being converted to diesel. I'm not planning to run it on diesel, I'm just considering using a diesel-like compression ratio while experimenting with other fuels like various blends, hydrogen etc. Dont some racing engines (turbo, blown) have similar effective compression ratio as diesels? What would have to be upgraded?