Rockauto Newsletter (Cummins Diesel Mj)

[onlyinajeep726]

Thought this was interesting.  Never knew of the Cummins B3.3 until now.  34 mpg out of a Jeep?  Can't beat that!

http://www.rockauto.com/Newsletter/archives/101812.html

 

Dave's 1986 Jeep Comanche

This is my 1986 Jeep Comanche. It has a Cummins B3 3.3 liter diesel engine. All of the accessories are from the original 2.5L Jeep engine. The AC compressor, expansion valve, drier, all 4 shocks, and steering stabilizer have all been replaced with parts from RockAuto.com.

 

I travel 50 miles per day and consistently get 34 MPG! I now have over 130,000 daily driven miles on the diesel conversion. I love this truck, and RockAuto has helped me keep it going.

 

Thanks,
Dave in Georgia

[87sparTruck]

That's cool :eek:

[GirsMJ86]

Interesting little engine from the little I just read about it. Weighs in at about 606lbs and makes 60-85hp with 158-224 lb-ft of torque. The oil change schedule on those things is crazy though, 350-hour/3-month intervals on the turbo or 500-hour/6-month intervals on the weaker naturally aspirated model. Not sure if that is the norm what that would translate to in miles but that seems kind of crazy. Of course I'm running on very little sleep right now so I could be whats crazy at the moment.

 

http://cumminsengines.com/b3-3-tier-3#overview

 

Doing a google search on the engine turns up quite a few YJ, FJ, and a few other things that have had it swapped in. The MJ is of course the coolest.

[terrawombat]

It's not uncommon for diesel engines to have 10,000-15,000 mile oil change intervals.  The oil I put in my VW TDi recommends changing it every 10K.

 

The owners manual for my '04 Ram states to change the oil every 7,500 miles in the 5.9L Cummins, but 10K intervals can be done if you're not towing.

 

You also have to remember that these engines take more oil than gassers so while the oil changes may seem more spread apart, it costs more per oil change.  My 5.9L takes 12 quarts per change.

 

Check out some of the larger engines on that site like the ISX15 and ISX12 - their oil change intervals are up between 15-40K depending on how the engine is used.

[92tanMJ]

I wants it :drool:

[comanchedude]

big heavy , no power... I don't know why people do it other than to say they did it. met guy at off road show has the yellow MJ you see alot (very nice MJ) with the same engine and he admits it painfully heavy .. and is a big disadvantage off-road.(very nose heavy) but is cool if your into the oil burners and have deep pockets and don't  do aggressive wheeling.

[terrawombat]

Fuel mileage.  The MJ in the OP is clearly not a wheeling rig - it's a DD.

 

Unfortunately many of the smaller diesel engines offered in the US are just variants of larger truck engines so they're generally very heavy.  I will agree that the B3.3 is a poor choice for a swap into an automotive application, but the guy likely yanked it out of some industrial machine and got it for a good price.

[Oddmodman]

big heavy , no power... I don't know why people do it other than to say they did it. met guy at off road show has the yellow MJ you see alot (very nice MJ) with the same engine and he admits it painfully heavy .. and is a big disadvantage off-road.(very nose heavy) but is cool if your into the oil burners and have deep pockets and don't  do aggressive wheeling.

I do believe the "yellow one" is the 4BT. In which case it weighs just over 200 lbs more than the 3.3. The 3.3 is not too bad at about 550 lbs. However at over 750 lbs, yes I'd say the 4BT would be a big disadvantage offroad. I think the 3.3'd be perfect, and according to one gentleman who did it in his Comanche (I can't for the life of me remember where I read about it), he was not only perfectly happy with it, but impressed as well.

[Oyaji]

Interesting comments so far guys - keep 'em coming.

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I am gonna toss out my choices one at a time and let you pick them apart. Let's start with the OM 617. Pros: acceptable performance in automotive application (revs fast for a diesel), a lot of them around, reasonable price, great reputation for economy and longevity. Cons: not-so-hot-horsepower, it's a non-stock conversion, needs adapter plate, a little heavier than the 4.0 (iirc 600 pounds), old diesel technology (maybe this is a pro, not a con?).

The OM617 engine family was a straight-5 Diesel automobile engine from Mercedes-Benz used in the 1970s and 1980s. It is closely related to the straight-4 OM616. Starting in 1978, a turbocharger was fitted to engines used in the 300SD. With some Mercedes-Benz 300D/300SD diesels already exceeding 500,000 miles, and a few nearing 1,000,000, the OM617 is considered to be one of the most reliable engines ever produced, and is one of the key reasons for Mercedes' popularity in North America in the 1980s, as it was economical, relatively quick (compared to most other diesels on the market) and was trouble-free, unlike the Oldsmobile LF9 diesel V8.

.

The OM617.951 was introduced in 1979 and displaced 2998 cc, using a 90.9 mm bore and 92.4 mm stroke. Power output was 125 hp (91 kW). Torque was rated at 180 lb·ft (244 N·m).

Applications:

1981-1985 300SD Turbo

1981 300TD Turbo

.

Then there is the VM 2.5. Pros: lighter weight, used overseas in stock XJ application, good torque, mechanical injection. Cons: hard to get in the USA, ditto for parts,  just-adequate anemic horsepower.

2.5L TurboDiesel
VM 425 2499 cc (153 CID) I4, OHV Diesel 114 hp (85 kW) @ 3900 rpm 221 lb·ft (300 N·m) @ 2000 rpm VM Motori 425 OHV 1994–2001

[onlyinajeep726]

I like the idea of the VM 2.5 because if it is offered in XJs, then a big pro for me personally is the ease of swap, i.e., motor mounts, harness placement and the whole setup can just be swapped into the MJ.  But, the big con with that as you said is the availability of parts, especially here in the US.

 

Some one posted a thread a while back here on CC about a guy up north that does OM617 conversions on XJs and has done many.  He has all the stuff and his own shop and is certified.  Can't recall the price he would do all this but IIRC, it was quite steep for the average Jeeper's pockets...

[Oyaji]

I like the idea of the VM 2.5 because if it is offered in XJs, then a big pro for me personally is the ease of swap, i.e., motor mounts, harness placement and the whole setup can just be swapped into the MJ. But, the big con with that as you said is the availability of parts, especially here in the US.

 

Some one posted a thread a while back here on CC about a guy up north that does OM617 conversions on XJs and has done many. He has all the stuff and his own shop and is certified. Can't recall the price he would do all this but IIRC, it was quite steep for the average Jeeper's pockets...

.

I thought about getting what they call a "half cut", which is just the front half of an XJ cut off and shipped here from overseas. Evidently it is the easiest way to get what you need. The beauty part is that since it cannot be put on the road, it is classed as "parts" for import. Would probably need to get 2 though, just to have a parts source! I wonder what the total cost would be including shipping...

.

Cost seems to be prohibitive for any diesel alternative, but for someone who intends to keep his vehicle on the road for the long term (like a Comanche owner, for instance :)), I figure that eventually fuel savings would pay for the swap.

.

Eagle's cam swap idea seems to make the best sense so far, practically and financially. But I can't help but think that a diesel would be the perfect swap for a 1986 with a 2.8L V6.

[onlyinajeep726]

Cam swap would be the easiest and more practical, but diesel swap would be way more fun.  A lot of people said that swapping in a 4.0 into my '86 is more work than it's worth, but I was willing to take it on and I'm about 3/4th of the way through.  If you put your mind to it, you can do it.  May need some deep pockets and another job, but hey... you only live once.

[mpace6a]

I wanted to do the om617 swap on my 2.8 mj, but the hp numbers killed it for me. What little info i could find on tuning it said that without modifying the injection pump your limited to ~145hp. And its a very costly mod. I'm a power hungry kid so 145 will never do.

[terrawombat]

I wanted to do the om617 swap on my 2.8 mj, but the hp numbers killed it for me. What little info i could find on tuning it said that without modifying the injection pump your limited to ~145hp. And its a very costly mod. I'm a power hungry kid so 145 will never do.

 

You don't do a diesel swap for horsepower.

 

You do it for torque, reliability, fuel mileage and the ability to run it on french fries.

[onlyinajeep726]

:agree:

[mpace6a]

 

I wanted to do the om617 swap on my 2.8 mj, but the hp numbers killed it for me. What little info i could find on tuning it said that without modifying the injection pump your limited to ~145hp. And its a very costly mod. I'm a power hungry kid so 145 will never do.

 

You don't do a diesel swap for horsepower.

 

You do it for torque, reliability, fuel mileage and the ability to run it on french fries.

Well, yes, and french fry exhaust is totally a plus, but, be it hp or torque, still power hungry and the 617 can't  deliver the power I'm pointlessly chasing. Although, I've been thinking about looking into the newer electronic injected mercedes diesels, since the mechanical IP is the limiting tuning factor with the 617s. still unsure what I'm going to do, just that i need to do something worthwhile when the 2.8 comes out.

[krustyballer16]

i just picked 2 of these motors up a few weeks ago. they were displays that cummins took around to shows. they have ZERO hours on them and never had fluids in them. Paid quite a bit for them but cheaper than "new" and soo worth it! should be firing one up this weekend to see how it runs then i will start my swap into my MJ here in the next couple weeks. I'm excited!

[92tanMJ]

i just picked 2 of these motors up a few weeks ago. they were displays that cummins took around to shows. they have ZERO hours on them and never had fluids in them. Paid quite a bit for them but cheaper than "new" and soo worth it! should be firing one up this weekend to see how it runs then i will start my swap into my MJ here in the next couple weeks. I'm excited!

 

Nice please take LOTS of pictures! :thumbsup:

[onlyinajeep726]

:agree:

[krustyballer16]

i will be starting a thread today about it hopefully and we should be starting the project this weekend or next.

[Oyaji]

i just picked 2 of these motors up a few weeks ago. they were displays that cummins took around to shows. they have ZERO hours on them and never had fluids in them. Paid quite a bit for them but cheaper than "new" and soo worth it! should be firing one up this weekend to see how it runs then i will start my swap into my MJ here in the next couple weeks. I'm excited!

.

Naturally aspirated - 60 horsepower. Turbo version - 85 horsepower. Torque about the same as the 4.0 Jeep engine, at  ~220 pound-feet. 

.

Torque is fine, but with so little horsepower your top speed will be limited to 65 MPH or a bit more, I think. Acceleration will be  slow (painfully slow for someone accustomed to gasoline-powered engine performance). Hills  will be challenging at high speed. Climbing long grades at speed will be impossible: you'll have to gear down. Is that acceptable?

[terrawombat]

Turning up the fuel and boost on this engine shouldn't be too much of a problem as long as it's a similar setup to the 4BT (and I believe it is from what I've read).

[Oyaji]

Turning up the fuel and boost on this engine shouldn't be too much of a problem as long as it's a similar setup to the 4BT (and I believe it is from what I've read).

.

It's an option - but the more you turn it up, the more you lose advantages of economy and longevity.

.

On a mechanical injection fuel pump the easiest way to boost power and torque is to simply increase the charging pump pressure (by turning up the charging pump pressure regulator adjustment - usually all it takes is an Allen wrench and a couple turns or less). You can also fiddle with the timing  fairly easily; fiddling with the advance requires disassembly of the pump (best left to a specialty shop).

.

One job I had to work my way through college was to rebuilt pumps and injectors in just such a specialty shop. I wouldn't want to fiddle with them, at least not beyond maybe turning up the charging pressure a little...  and even then I'd want to do it on a dyno (~5%  gains or so,         10% max).

[terrawombat]

True - I'd be less concerned with the longevity of the B-series engine based on it's stellar reputation.  It's an overbuilt engine to begin with and there are quite a few folks running some serious modifications on stock internals...and they have been doing so for several years and hundreds of thousands of miles.  You're economy will likely take a hit if you're in the throttle too much.  I agree that he'll likely need to gear down to achieve a balance between sustainable highway speeds and fuel economy.  The 1998-2004 VW TDIs might be a good starting point for him to look at gearing as that engine has similar HP specs (90HP and 155ft-lbs) to the B3.3.  My '02 VW TDI can do 80+MPH with no problems, although I suspect a lot of that has to do with the aerodynamics of the vehicle.

[krustyballer16]

just started my thread about my swap. its in "pub"