CRAZZY THOUGHTS (DIESEL)

[92tank]

So i know this is a little off the stroker area(kinda) or maybe off the wall is more like it.




i have been pondering this thought for awhile, would it be at all possible to turn a 4.0 or any one of the strokers into a diesel run motor? and if so what would have to be done and what would it do power and efficiency wise. the only reason was thinking this way was to put a 4.0 in a tractor and not need to have the gas on hand to feed it. i know that Farmall had the MDiesel tractor that you started on gas to warm it up and then switched it over to diesel, could somebody possibly do that with a jeep motor. i know you would need to work out the bugs(like fuel management, timing, compression, spark, and others for sure) BUT could it be possible. any thoughts and it will be interesting to see were this one goes.



i was thinking like twin injectors one diesel, one gas, on the same intake. or carburator in place of the throttle body with diesel injectors in the same place they are now. just some thoughts

[4.whoa]

I know some diesels run something like 16:1 compression. I really don't see that on a 4.0 but if you could, will the headbolts/ gasket hold?
Also it would just about have to have a turbo right?

[unlimitedrubicon]

If you do some research into the force it takes for diesel to work (sheer compression, no spark) you would quickly find that it would not be feasible to build a 4.0 or stroker that could withstand the cylinder pressures. This is especially true with the turbo diesels where the true power and efficiency is found. This is not even getting into fuel injection and combustion differences... You would be better off using a small diesel from something else and even that would be a chore.

[unlimitedrubicon]

Speaking of headgaskets, check out the sleeving and o-ringing that goes into a heavy diesel... Then again those pressures would grenade our engines in just moments...

[amcinstaller]

yea, the idea of a 4.0 on diesel would sound cool, but the inner magic of a diesel engine just isnt there on a 4.0. not enough compression, nor heat without damaging something, and the control system is wrong (controlling air vs controlling fuel pressure)

[92xjcowboy]

To make it work you would need to use cylinder liners (sleeves), Head studs, High performance head gasket (strong material to keep from blowing up), Stronger pistons, stronger connecting rods, stronger crank. Not to mention the fuel management and all the custom head/injector work needed.

Our block probably could hold up to it but it wouldnt make any power or be very efficient. I tore apart a Detroit 60 series engine today and looked at the size of the materials used and its a night and day difference between most gas motors and most diesel motors. Diesels run just under double the compression of a gas motor and will do it for 1,000,000 miles before being rebuilt. Pressures get into the ridiculous zone and material thickness needed to hold it also becomes insane.



My guess as to what will happen if you do this is this:

I think that the cylinder walls and the head might hold up to the pressures but they wont be rigid. My guess is that they will have tiny amounts of flex that will cause cavitation in the coolant passages because of the pressures needed to heat the air to 700* (auto ignition of diesel fuel).

You wont have pinging problems unless you use a power adder (propane, nitrous, water/methanol) because you dont inject the diesel into the cylinder until right before TDC (when pressures and temps are highest) You should be fine with temps as well because diesel cylinder temps usually dont go much higher than 4000 degrees (only the combustion process)

You would be best off having the main bearing journal sizes increased and having a custom crank made because of the pressures involved with diesel. This would also require custom rods if you increase the rod journals as well.

You could probably get away with putting your injector in the spark plug hole but if you dont then you need to have a custom head made that allows the placement of an injector in the combustion chamber.

Getting the fuel system (electronics) to work right would not be fun but it wouldnt be impossible if well thought out.

Those are just what comes to mind when I think of issues with the conversion. Remember how well GM's 350 diesel worked out?

Matt

[SkylinesSuck]

How would you propose even getting the CR up high enough to ignite Diesel? I don't think domed pistons on a thin head gasket are going to cut it.

[Cheromaniac]

I know some diesels run something like 16:1 compression. I really don't see that on a 4.0 but if you could, will the headbolts/ gasket hold?

I agree. It's not even worth the effort to try to convert the 4.0 to a diesel 'cause it was never designed to be one in the first place. If anyone really wants to convert an XJ to diesel power, there are plenty of modern turbodiesel powerplants that can do the job. You could keep it in the Jeep family by swapping a 2.8 CRD diesel from a KJ.

[amcinstaller]

i just worked on a 46 chev the other day where the guy had put in a small generator diesel. smallest cummins ive ever seen. noisy though, and a rough ride, especially at idle

[4.whoa]

Here's a diesel jeep
http://www.youtube.com/watch?v=KyS9A3jbwLM

[amcinstaller]

that looks like the engine this truck had!! man those things smoke bad when you start them up on a cold morning

i like this one, even though its not as cool, same engine. i like his sticker on the back window

[92xjcowboy]

How would you propose even getting the CR up high enough to ignite Diesel? I don't think domed pistons on a thin head gasket are going to cut it.

You dont absolutely need to have a 16:1 CR you just need to have the cylinder temps at 700 degrees for the diesel to fire (when atomized with an injector)

The more air you force into a cylinder the higher your pressures are going to be and the higher the temps will be.

[Biggrnjeep97]

How would you propose even getting the CR up high enough to ignite Diesel? I don't think domed pistons on a thin head gasket are going to cut it.

You dont absolutely need to have a 16:1 CR you just need to have the cylinder temps at 700 degrees for the diesel to fire (when atomized with an injector)
The more air you force into a cylinder the higher your pressures are going to be and the higher the temps will be.

Unfortunately, there is no Turbo/Supercharger that would "Force" air into a cylinder at idle, so yes, you do need a decently high (15:1 and up) CR. The only reason modern common rail diesel engines get away with lower (~17:1) CR's is their injection systems idle with 3-5kpsi, cruise with 7-10kpsi and max at ~25kpsi, atomizing everything that goes through them. Better atomization= easier ignition= fuel economy= power=...
-Will

[johnj92131]

A diesel conversion on the 4.0??

You should do some research on the 1978 Oldsmobile diesel. This was an original and VERY strong/sturdy gas engine. Olds/GM engineers made the bottom end stronger. But the engine was a failure because it blew head gaskets from the high diesel compression. Ask me how I know. Blew one head gasket, had it fixed, then the other one blew. No fun.

Think the factory finally cured the problem by going up to 6 head bolts for each cylinder. But the reputation of the engine was garbage by then.

If you want a diesel, get a MB 3.0 Turbo diesel and hot rod it. Don't lead, follow past practices. Learn from mistakes of others.

Got lots of money? look at the MB 2005 3.2 litre in line 6 turbo diesel. Stock, around 370 lbs/ft and 215 hp. Look at european chip tuners for lots more power.

Or find a 3.0 BMW diesel with something like 300 hp. Will not be cheap at all. But with dual turbocharges, it will HAUL ass. Need more? Chip tune from Europe!

You will spend cubic dollars (or maybe lots more) trying a diesel 4.0 Look at older diesels from Europe for better economic policy.

Need another project? How about a 14 valve head with 6 intakes and 3 exhaust valves? Yes - it does not add up.

Not sure what you would need for a transmission to hold the diesel torque. Turbo Hydro 400? Yes, but how efficient is that?