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Old 11-08-2011, 06:09 AM
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With tax season around the corner and a nice bonus on the way, I am seriously contemplating a 4bt conversion. Back-story: I put a set of 33's on and destroyed my gas mileage. I went from getting nearly 21 mpg's to 14.5 on a good day. I hear that (depending on the build) you could see 24 mpg's on average and still perform offroad with a 4bt.

I have done a lot of research on the subject and have found 2 kits: River Raider and Jeepyard. Does anyone have any experience with these companies?

Also, the engine will cost me between $3000-$6000 with a rebuild kit somewhere in the neighborhood of $500. I have rebuilt tons of 7.3's (if I could stuff one in the jeep I would), but never a Cummins product. Anyone ever done their own rebuild?
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Old 11-08-2011, 07:13 AM
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Are you contemplating a 4bt to increase your mileage because you do long trips and want to get a longer range out of a tank or to save money on gas?

Because if it is to save money on gas, it is going to take you a few years to offset the cost of the conversion.
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Old 11-08-2011, 07:24 AM
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Originally Posted by ludski View Post
you can easily get high 20s with a diesel on 37s.

but how did you lose so much mpgs with just 33s?!?!?!?!!?!

somethings not right there....
i lost 2mpg upgrading from 32s to 37s!
He probably has 3.21 gears. I seem to notice that the slightest tire size change with this ratio cuts down mileage to a ridiculous number.

The 4bt swap sounds amazing, but i can't imagine it could be done for less than 20k. I mean don't you have to change out the fuel system and everything?
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Old 11-08-2011, 07:50 AM
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Originally Posted by Dutchboy101
To answer your question about River Raider and Jeepyard, they are both good companies. Jeepyard is the company that came up with the 4BT Cummins conversion, and river raider uses the Jeepyard 4BT conversion kit to sell or install.
Keep in mind that the 4BT is a very heavy engine, and personally think that it is too heavy for serious offroading. They do say that you are able to get in the range of 27 MPG, which would be nice. Personally I'd rather get an aluminum LS engine in the Jeep. There is another shop that is working to get that kit out. Not sure if I can mention them, as I do not think they are sponsors on this forum.
Heavier than a hemi?
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Old 11-08-2011, 08:14 AM
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Not sure about 20k for a 4bt conversion. Never looked into a jk conversion so I have no clue what the cost is of the wiring harness and motor mounts. I did one on my yj for 3k. Look for a wrecked ups, fedex, frito lay truck or any delivery truck that size. I bought a wrecked one for $4200, kept the motor and either scraped the pieces or sold it. I did the veggie oil conversion and pumped up the motor. It was quick with lots of low end power. But the conversion on my yj was very easy(no computer). Deals are everywhere, just have to find them.
Good luck
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Old 11-08-2011, 10:28 AM
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The gears are the problem for me and they will be swapped with the motor. I want to do the conversion because I can haha. As for the motor, I just talked to a guy that has one. All I need to do is haul it off. He mentioned he needs his fence tightened (nothing comes free).

Now the kit. I think I will give the boys over at jeepyard a call. Then I will make my decision.
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Old 11-08-2011, 10:40 AM
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Bruiser Turbo Diesel had a fantastic 4BT kit at SEMA.

Last edited by armycop; 11-08-2011 at 11:40 AM.
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Old 11-08-2011, 11:39 AM
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My bro-in-law has a CJ with a 4BT. Lets just say that it is super noisy and shakes like a dog passing a peach pit. He loves the low end grunt out in the hills but really hates it around town..... mileage is good, he said he wouldn't do it again.
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Old 11-08-2011, 12:07 PM
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Originally Posted by matzjeep View Post
There is a company offering a VW TURBO conversion out there. I can't remember the name but a google search should work for that.

The jk version is being developed and the tj is ready now.
That engine seems pretty small for a JK. HPA's YJ sure looks good, though: ht_p://www.hpamotorsport.com/tdijeep.htm

Originally Posted by Cochise View Post
My bro-in-law has a CJ with a 4BT. Lets just say that it is super noisy and shakes like a dog passing a peach pit. He loves the low end grunt out in the hills but really hates it around town..... mileage is good, he said he wouldn't do it again.
A common rail would be much nicer.
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Old 11-08-2011, 04:34 PM
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Originally Posted by tslewisz View Post
That engine seems pretty small for a JK. HPA's YJ sure looks good, though: ht_p://www.hpamotorsport.com/tdijeep.htm
I dunno... the 3.8 v6 has 202 HP and 237 ft-lb at the crank. HPA's 1.9 i4 conversion has 190 HP and 289 ft-lbs at the crank. The diesel might actually be a bit faster. And getting 40+ MPG highway with 35" tires is very nice! On the other hand, at $1100 for the kit and about $5000 for a rebuilt long block (not even counting labor or sweat equity), it would take a long time to make up the difference in gas prices.

I'll have to revisit it once they get their JK kit finished. Hrm... I wonder if they need any trial users?
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