Carbeurated diesel
 

Ok guys help me out here. I'm in school for diesel tech and there's a guy here that thinks he can take an old n/a 7.3L Ford diesel and put a gaser intake n carb on on it bit yet still keep it a diesel.

We think he needs to go to the funny farm lol!
What yall think?

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ummmm.....NO, you cant do that lol. the diesel needs to be injected at just the right time to fire correctly there is no other timing to it. if you did put a carb on it, then fuel would flow all the time and cause a runaway! there is no way it would work!

i do not believe that is true. the valves in the engine tetermine when fuel and air enter the cumbustion chanmer. and the throttle stop in the carb would determine air flow. to little and it would die out due to a super rich mixture just like a gas engine. each cylinder sucks air/fuel in at a specific tim NOT ALL THE TIME!!! so it the carb is tuned correctly there is no reason it wouldnt work. old 6.9s and 7.3 idi's are injected into the manifold not the cylinders.

food for thought... if you take the multiport fuel injection off of a gasser truck and swith it to an old school holley intake/carb will it run? YEP and run well. not quite as efficient but it will run.

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also there would be no reason to ever change the cam timing on the engine??? this is what tells the valves to open when they do. that was an irrelivant fact in the above post. all engines need to be Injected/timed at the right moment to run properly

i didn't say anything about cam timing, there would be no timing for the fuel to go in or spark timing to time when the fuel burns is all i meant, therefore if the intake valve is open sucking fuel in the entire time it will run away if you even try to rev it up.

you are comparing an apple to a bannana yes they are fruit but not the same at all, a carb will not work on a diesel period. thats why they don't do it.....ever. a diesel has to have a precise fuel timing in order to run correctly, without that it will not run. and if it does you will have some serious damage.

try it with yours and see, put a throttle plate on there and start spraying fuel in and see what happens when you rev it up make sure to get a video too :tu:

to the op it won't work.

never said it would run well but with a throttle plate you can slow the air which cools fire. it would most likely idle great run decent in gear but rev to the moon and take a VERY long time to idle back down after you reved it up in neutral, but it WOULD idle run.

All diesels inject the fuel directly into the cylinder. When they are talking about idi it is a prechamber in the top of the cylinder where the fuel is injected but it is still the cylinder.

It would not work to just put a carb on it. It is like turbostang said it has to be precisely timed. If you just run it through a carb the cylinder would fill with fuel and air when the piston came up and hit a point where it could burn it would no matter where in the cranks rotation that was. The next problem with it is the fuel has to be atomized to burn right which would be one problem a carb would have.

The reason you can take multiport off a old gas truck and put a carb on it is because a gas engines ignition is timed by spark and a diesel is timed by fuel.

exactly^^ no way it will run might idle like s**t for about 10 seconds then load up and die if you don't lock it up with too much fuel. like i said, try it on your truck (take a video) and let us know what happens :tu:

interesting. at what compression does diesel ignite? ive been wrong a million times before probably am again. i just cant fathum how an engine can run away if it is getting anywere near close the amount of fuel it needs to run. atomization would suck no doubt.

to me fuel timing would be acomplished by valve timing. but if it ignites before tdc comp. the it no doubt would knock itself to death not RUNAWAY!

so you fill it full of air compress it some fill er full of fuel compress it some more then bang. if that s the case wouldnt it be going bang as the fuel is being injected?

here to learn like everone else.

It does go bang as its being injected. It doesn't in the injector lines because it has no oxygen and has not been atomized. I don't know if there is a exact compression ratio that it ignites there are many factors that go into that heat, how well the fuel has been atomized, cylinder pressure.

I can tell a story of experience of why not to dump small amount of diesel down the intake to get one to start. We had a old junk chevy with a 6.2 that would not start so we took out the can of diesel and dump a small amount in the intake a couple of cranks and a few loud pops and we had a busted piston.

it does go bang when the injectors open thats what causes the bang. when a diesel opens the injector it is already starting to burn it fires at what could be considered when the spark plug sparks. no fuel is in till then only sucking air and compressing it. then when the compression is just right and it is at the right time the injector opens and sprays in like i said already burning at this point.
diesel will not ignite if it isn't atomized good, and the compression is too low it will just fill it up untill there is enough heat from compression (friction) to ignite it.
a diesel will also run away if it is getting any amount of fuel over what it needs to idle, thats how they rev up not like a gasser where you have to allow the throttle blades to open creating less vaccuume. a diesel revs acording to how much fuel is injected (crudely said i know)
we are all here to help each other bud :rocking:

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oh and as for your compression questions there are many variables that can play in here, how much boost, injection timing etc that it can vary widely, most high boost racers or pullers have a low compression ratio to allow for the extra boost, (and bigger camshafts to allow for valve reliefs lol)

URIKA i figured it out.

first of IM WRONG carborated or throttle bodied diesel wouldnt work
second thanks for getting the gears to turn guys.

this is gonna be kinda long but im pretty sure i figured out why it wont work.

first problem- if it were carborated at an idle it would be scavaging like crazy (flooding itself if it were gas) but because it a diesel it would still be chugging away blowing LOTS of black smoke. when the throttle is then cracked it would go nuts because it would have so much unburned fuel in the intake manifold and now excess air to light the fire. thus a runnaway.

second problem- if said diesel fuel explodes at say 14 to 1 compression and you have a 20 to 1 engine. ( numbers flying out of the old ars here) then the abundance of fuel would ignite before the piston had reached DTC and would VIOLENTLY knock. if it could even overcome the blast which i kinda doubt.

a throttle body could solve the runaway problem but WOULD NOT solve the pre ignition catastrophy. a throttle body WOULD work IF the compression ratio was lowered to the exact number in which diesel ignites, but what would be the point and changes in altitude and temp ect would affect this greatly.

i think???

if peak compression was lowered to ignition of diesel fuel theoreticly this might idle but load up still or flood, BUT it would be almost impossible to start. plus any wear on the engine would make it useless lol, but like you said any change in altitude, temp would make this thing one cranky pos. it would have to be exact right temp, humidity, altitude, air density etc for it to work.

p

I guess if you tweaked every single variable you could get one to run on a carb until the slightest thing changed. It's just a bad idea it would be like putting a carb on a turbine jet engine I guess you could get it to work but it wouldn't be worth a crap.

i dont think one would run on a carb because the engines vacume would pull excess fuel from the bowl. i believe a trottle body --could-- work because the engine couldnt load up. but would be worthless, because of the lack of compression and fluxuating everythings

Wow didn't expect this much info on the subject!

Thanks to all who replied! Going to show this thread to the guy and see what kind of crazy idea he has now, lol!! :c:

Nah. Let him do it. If it does work ( or run at all ) he should get some kinda diesel engineering award. I know I wouldn't want to be the one tryin to jet that thing:c:

Lol, I showed him the thread but he's a crazy guy and says "I'll figure out a way to make it work". I dunno where he's getting this stuff from cause his grades in class are horrible most of the time with a rare decent one lol!!

Re: Carbeurated diesel
 

Let him try, maybe he is on to the next big diesel mod hahaha I have a holley 950 sitting in my shed hmmmm gets me thinking lol


Still wont work too many variables not enough controll in a carb setup

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It's all not a good idea. Someone coming up with this idea its no wonder hes doing bad in the class. Take a highly precise fuel injection system off of a truck and put a carb on it doesn't sound like a great idea to me.

Plus I don't think your just going to find any old gas intake and have it match the ports of a 7.3. You would have to cross referance a gas motor tha has a pretty close deck height. And even then the ports don't have to be dead nuts but should be close. The chances of that are slim and none!

High octane gasoline has a much higher autoignition temperature than Diesel fuel. Methanol and propane don't typically ignite until the Diesel fuel is injected; high octane gasoline isn't as resistant to detonation as propane or methanol, but it is resistant enough that fumigating it into the cylinder of a Diesel engine with a carburetor is vaguely feasible.

To work the "carburetor" would need to be modified to do what you want; I wouldn't think you'd do it with throttle plates, so without the throttle it would be dumping gas in at all times. I imagine that fumigated gasoline at low load would just pass through as ridiculous hydrocarbon emissions, not hurt the engine but really burn the eyes; that's what about 10 LPM of propane does at idle on a dyno. You'd want it under boost, that's where you'd stand to make power... So if you were going to do it I'd advocate using a fuel injection system, which would look really similar to a water/methanol injection system. Also, if you inject water along with the gasoline, it will make detonation much less likely.

The closest your buddy should ever get to oil is making fries at McDonalds.He MUST have the best smoke in school.

Lmao!

It's guys like that who made me want to learn how to fix my own trucks.

Wow were you serious about this? The kid is retarded...

Lol! Yes BRE, he's totally serious. I along with everyone else in the world say he's a tard but he's determined to make it work. He says "it will just be a show truck to say it can be done, don't plan to actually use it". At this point we all just say ok man whatever floats your boat lol

Carbeurated diesel
 

That's about all you can say; typically when people have hit that level of stupidity there's no talking them down. They just can't use that dime sized brain of theirs to grasp the fact that they're wrong. Too busy using the rest of their brain capacity figuring out how to reverse engineer a functional cornerstone to our world... If only all of our diesels used a carb and were show worthy. We'd all starve and I'm pretty sure the Germans would rise to finish what they started in WWII... They lost bc of pud pounders like this guy


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