Diesel Expedition Rig, 4bt vs 6bt (or a Toyota engine..) (1 Viewer)

[greenarrow19]

80 Diesel Expedition Rig, 4bt vs 6bt (or a Toyota engine..)

Hey guys!
I have been thinking about what it is that I am going to do with my rig, a fzj80. Want to begin with the end in mind so that I can map out how to get there and so that all mods will work to that end. After reading several forum posts and considering our desires and lifestyle, we are going to make this fzj80 an expedition rig.

Growing up with diesels and considering them a superior engine, especially for expedition purposes, I would like to eventually transplant a diesel engine. The criteria for selecting the specific engine are fuel economy (60/40 split between hwy and trail), longevity, price and availability of parts. I have used the search function and read numerous posts over the last week about transplanting a diesel into an 80 and have learned quite a bit (if answers to the questions in this post can be found elsewhere, please point me to them!). What follows are some facts that I gleaned for verification and some remaining questions.

It appears the most popular options by far are Toyota and Cummins engines. From what I can gather, the Toyota engines are quieter, more expensive, and harder to find parts for and the Cummins are cheaper, louder, and easier to find parts for. My preference would be to stay Toyota but with the fuel economy and longevity being similar and the price and parts of the Cummins being lower, it makes Cummins nearly irresistible. So, I have settled on the Cummins. Now, that conclusion comes from forum posts and a bit of research and is open to correction and discussion. I welcome both! If my impression of the Toyota engines are off, I could easily be swayed.

So, help me evaluate the Cummins options, the 4bt and the 6bt.

HP: The 6bt provides loads more HP than the 4bt. Does that require changes or modifications to the stock set up of the 80? Seen more 4bt’s in the lighter TLCs but does the 4bt provided sufficient HP for the 6,000 lb+ 80?

Height: Both are quite tall. I have read the the 4bt requires a 4” lift at the least. Does the 6bt require a lift? Is there space for an intercooler on either?

Noise: The 4bt run considerably louder than the 6bt. Not sure if that is a con or not.

Shake: The 4bt runs run rougher than the 6bt. Is the vibration an issue (motor mounts, etc) long term?

Weight: The 4bt is lighter than the 6bt and its somewhat similar in weight to the 1FZ. Does the heavier 6bt require the addition of stronger axels? I have heard rumors that the additional weight is too much for the stock axel, but nothing certain.

Price: From what I can find, the 6bt is often cheaper then the 4bt. However, if the 6bt requires modification for the HP and the weight, then the 4bt would be more cost effective.

MPG: I have found very little information comparing MPG. I would think that the 6bt would have better MPG because it would be running at a lower RPM, though I might be way off. Still learning diesel theory If the 4bt has to be tuned up to provide enough HP for the 80, would that kill the MPG?

Pending correction, answers and discussion, the 6bt is the leading option. I appreciate any comments, ideas, suggestion, contributions, etc. Thanks in advance for them. Let the conversation begin!

 

[cody c]

If you have enough budget, get prophets or someone to throw a toyota diesel in it. If you want a 6bt it can be done, but I would suggest finding a NV4500HD then getting the $800 AA adapter to split-case, and putting in heavy duty springs.

Where do you plan on taking your expedition rig? south america, north america, africa, wall-mart etc.. Kind of effects the basis of whats the best for you based on parts availabity in other area's.

BTW, wheres that youtube flick about expedition vehicle questions with the animated dogs? I think someone needs to post that on here...

 

[greenarrow19]

If you have enough budget, get prophets or someone to throw a toyota diesel in it. If you want a 6bt it can be done, but I would suggest finding a NV4500HD then getting the $800 AA adapter to split-case, and putting in heavy duty springs.

Where do you plan on taking your expedition rig? south america, north america, africa, wall-mart etc.. Kind of effects the basis of whats the best for you based on parts availabity in other area's.

BTW, wheres that youtube flick about expedition vehicle questions with the animated dogs? I think someone needs to post that on here...

Thanks for the reply. I looked into a few post that mentioned having Proffits put in a Toyota and the price tag was high, like $10K+ high, and there is likely a wait time. Might have been dated information, I'll call Monday and get current info.

With the NV4500HD, the AA adapter and the heavy duty springs, I am guessing the price of the 6bt conversion would be under the 10K Proffits conversion. Thats based on first impression but might have to put the pencil to it to be sure.

We are planning on using the rig in the Americas. In my dreams it sees action in Africa and Europe, not sure if that will ever be reality...

 

[joseywales]

As soon as you get away from the US or Mex, Landcruiser diesels are everywhere. I wouldn't let that be your deciding factor. Any parts you might need can be sourced in Canada easily, or, shipped from Japan overnight freight. If you need a new head or block, that might be a bit spendy though. The mid 90s multivalve Toyota diesels are awesome. They are also available with a 5spd in an 80 series, so direct bolt in is possible. As far as 6bt vs 4bt, you would probably be waaaay farther ahead looking for a Proffits 80 that is done and for sale, than converting your own. I have heard a lot of people are not pleased with the noise/vibration level in a 4bt conversion, and many are being resold. If you are serious, I am on Vancouver Island in BC Canada and there are quite a few JDM shops here. I looked at an 80 yesterday with diesel 5spd... I could make some inquiries for you if you like. I know Uncle Sam has issue with you bringing in the JDM 80 as a whole, but what about drive train? PM me if you want me to look into pricing.

 

[greenarrow19]

PM sent... Thanks for the post and offer of assistance!

 

[randito]

What about the Isuzu diesels? They seem to be a nice intermediate between the Cummins and Toyota and are probably the cheapest of the options.

 

[alia176]

The criteria for selecting the specific engine are fuel economy (60/40 split between hwy and trail), longevity, price and availability of parts.

I know that your mind is set on a diesel conversion so these points are moot but I'll ask them anyway.

Given that our hwy speed limits are 70-75 mph, which translates to me driving at 75-85 mph, do you think you'll achieve a fuel econ of anything better than 15mpg at that speed? Of course, once you get to the trail head and air down, you'll be sipping diesel whereas your buddies with petrol will be sucking it down.

 

[Fantom]

I know the 1HDT enigne (JDM 80 series) gets better milage than anything domestic ever does on the highway and off. My friend's has no issues in doing 120+km/hr on the highway and still pull off way more kilometers to a tank than the gassers. A good, strong, turbo diesel will get you further on any terrain. Banks managed to beat some speed records with his trucks and his modifications.

 

[derelict]

I am building the same sort of thing and am starting with a BJ60 with the H55F. I thought about a diesel 80 conversion but the 4BT is anything but smooth, its heavy and tall requiring 35" tires, and considering I want to cruise with windows down most of the time, its LOUD. I chose a factory diesel for worldwide parts availability whereas a Cummins does not really match up. I'm looking at putting a turbo kit on it and with that, I will have more than enough power for what I need to do. As for mileage, I'm averaging 18 mpg in 100% city driving and my truck is pretty built up already. A gas version with the same equipment on it would be lucky to hit 13 city. With that comes more range which is the reason I wanted diesel. I am still learning and by no means an expert but a factory diesel will be far easier to service abroad than a swap using US market parts. Also, nothing can come into the country newer than 1985/6 so that kills an 80 series factory diesel. You can swap Toyota stuff into an 80 but that's big bucks.

 

[alia176]

I know the 1HDT enigne (JDM 80 series) gets better milage than anything domestic ever does on the highway and off. My friend's has no issues in doing 120+km/hr on the highway and still pull off way more kilometers to a tank than the gassers. A good, strong, turbo diesel will get you further on any terrain. Banks managed to beat some speed records with his trucks and his modifications.

I'd be curious to know what a 1HDT mpg is at a steady 120 km/h over a long trip. I assume it gets 17 mpg easy but not sure.

 

[alia176]

As for mileage, I'm averaging 18 mpg in 100% city driving and my truck is pretty built up already. A gas version with the same equipment on it would be lucky to hit 13 city.

do you have any idea of your mpg at 75 mph over a long trip? Can you maintain that kind of hwy speed w/o having any EGT issues to worry about? Just curious.

 

[derelict]

do you have any idea of your mpg at 75 mph over a long trip? Can you maintain that kind of hwy speed w/o having any EGT issues to worry about? Just curious.

I do actually. I averaged 18.6 mpg doing 70- 75 mph from New Orleans to Arlington, Va. Dont have an EGT gauge so I have no idea about temps. I was doing very good on mileage until around Tennessee where things started climbing resulting in a few 3rd gear slogs up mountains. I really dont think I want to go too much faster than 70 though. The truck is a brick.

 

[alia176]

I want to go too much faster than 70 though. The truck is a brick.

That is the same conclusion that I came up with when I was hot on a diesel conversion. Quite a few of my wheeling trips start 300+ miles away from home and I want to cruise to the trail head at 75mph+. Unfortunately, regardless of which brand of diesel engine I ended up with, I won't achieve a decent fuel economy on the hwy. Now, if all of my friends had diesels and we just love to hang out on the right lane doing 65 mph, that'd be a different story My 7,000lb 80 series would get 17 mpg if I drove 65 all day and I've proven that to myself in the past. But alas, I have limited vacation time and need to get to places in short order.

I still dream of a diesel conversion, just can't seem to figure out a good justification yet.

 

[Workhorse]

My H150F manual doesn't have as long of legs as an automatic version. I usually head down the highway at between 60-65 MPH and get between 21.5-22+ US MPG consistently. It can go faster all day long-but I don't because I am in no hurry and don't want to beat on my truck.

My Father has an HDT with an auto and cruises between 70-75 MPG down the highway and gets between 18-21+ US MPG regularly.

On the trail, it gets better mileage than my old thirsty 1FZ-FE. It is heaps better all around, is completely Factory Toyota, and it is way quieter than a Wonderbread/Doritos van motor (4BT) set up to boot.

I have no problems at all getting any parts for either truck by the way.

 

[alia176]

My H150F manual doesn't have as long of legs as an automatic version. I usually head down the highway at between 60-65 MPH and get between 21.5-22+ US MPG consistently. It can go faster all day long-but I don't because I am in no hurry and don't want to beat on my truck.

My Father has an HDT with an auto and cruises between 70-75 MPG down the highway and gets between 18-21+ US MPG regularly.

On the trail, it gets better mileage than my old thirsty 1FZ-FE. It is heaps better all around, is completely Factory Toyota, and it is way quieter than a Wonderbread/Doritos van motor (4BT) set up to boot.

I have no problems at all getting any parts for either truck by the way.

I like those HWY mpg numbers, drool.... I wonder if any of the other engines (dodge/chevy/ford) would be able to duplicate that fuel econ on the hwy. I have two friends who drive a DMax and a PSD respectively. Neither of them can achieve anything over 16 mpg doing 75+ on the hwy on a consistent basis.

 

[derelict]

I could do 75 mph no problem. Revs would be probably about 2700 so that's no big deal. Flat landing I could top 18 mpg too but living in Va, I am smack in the middle of mountains but that being said, I am still able to get 18+ mpg and my truck is FAR from stock. I got the diesel bacause I wanted the extra range and I wanted all factory bits. No built 60 like mine in gas form can touch my numbers. Sure, I am not fast by any means but I'm not trying to be. I might spend an extra 30 mins behind the wheel but not having to carry extra jerry cans and being able to do 330 miles to a stock tank is COMPLETELY worth it.

If, when loaded down, you can get 15+ hwy in your gas powered rig, then that is incredibly impressive and stick with it. Is your rig stock?

 

[alia176]

I could do 75 mph no problem. Revs would be probably about 2700 so that's no big deal. Flat landing I could top 18 mpg too but living in Va, I am smack in the middle of mountains but that being said, I am still able to get 18+ mpg and my truck is FAR from stock. I got the diesel bacause I wanted the extra range and I wanted all factory bits. No built 60 like mine in gas form can touch my numbers. Sure, I am not fast by any means but I'm not trying to be. I might spend an extra 30 mins behind the wheel but not having to carry extra jerry cans and being able to do 330 miles to a stock tank is COMPLETELY worth it.

If, when loaded down, you can get 15+ hwy in your gas powered rig, then that is incredibly impressive and stick with it. Is your rig stock?

You have some GREAT mpg's!!

My 80 is not stock, far from it. But, it is geared to 4.56s, 315s and a part time Tcase. I live and play in the 5,000'+ elevation.

 

[derelict]

They're okay. I'm doing a few things to it that might increase my overall economy. I'm going to a skinnier tire and looking at a turbo kit which I've heard actually increases the efficiency of the motor. She is no rocket ship but I would say its peppy with the 5 speed and 4.11s. The problem is you have to want a diesel as the cost of a conversion and the increase in cost per gallon won't pay for itself for a very long time. The only real reason to get a diesel is to increase your range between fill ups. It sounds like you don't mind filling up a little more often though.

 

[greenarrow19]

Thanks all the post! Learning alot and love to see actually milage recorded!

I am building the same sort of thing and am starting with a BJ60 with the H55F. I chose a factory diesel for worldwide parts availability whereas a Cummins does not really match up. I'm looking at putting a turbo kit on it and with that, I will have more than enough power for what I need to do. As for mileage, I'm averaging 18 mpg in 100% city driving and my truck is pretty built up already. I am still learning and by no means an expert but a factory diesel will be far easier to service abroad than a swap using US market parts.

Seems like more and more people are suggesting going with the Toyota engine. Which is what I would prefer. I too like to roll with the windows down That and the fact that parts are more available both here and abroad than I thought has me trying to locate a 1HD-T or 1HD-FT. Any suggestions on where to find one would be appreciated. When you say that your truck is already pretty built up, what modifications have you made?

I have no problems going 65 the while way! Getting there has its own joys to me. However, I totally understand the time crunch factor.

My H150F manual doesn't have as long of legs as an automatic version. I usually head down the highway at between 60-65 MPH and get between 21.5-22+ US MPG consistently. It can go faster all day long-but I don't because I am in no hurry and don't want to beat on my truck.

My Father has an HDT with an auto and cruises between 70-75 MPG down the highway and gets between 18-21+ US MPG regularly.

I have no problems at all getting any parts for either truck by the way.

Would love to have either of those MPGs!! How would you compare/contrast the H150F and the H55F? From a pure economy point of view, the H150F looks to have the advantage.... Also, are you getting those MPG numbers with stock ratios?

They're okay. I'm doing a few things to it that might increase my overall economy. I'm going to a skinnier tire and looking at a turbo kit which I've heard actually increases the efficiency of the motor. She is no rocket ship but I would say its peppy with the 5 speed and 4.11s. The problem is you have to want a diesel as the cost of a conversion and the increase in cost per gallon won't pay for itself for a very long time. The only real reason to get a diesel is to increase your range between fill ups. It sounds like you don't mind filling up a little more often though.

Turbo.... there is just something to the sound of a diesel turbo that resonates with the soul Encouraging to know that you are getting those numbers with the stock ratios. Be interested to see how your future adjustments effect your MPG. Any speculation?

The only real reason to get the diesel is because you want a diesel We plan on having this rig for a good long while and really using it alot so the diesel suits that purpose, not the purpose of our pockets...

Keep the comment and conversation going

 

[derelict]

Turbo.... there is just something to the sound of a diesel turbo that resonates with the soul Encouraging to know that you are getting those numbers with the stock ratios. Be interested to see how your future adjustments effect your MPG. Any speculation?

Not too sure but Im looking forward to a turbo spooling. Its more for the power than an increase in mileage or efficiency for me. Being in the mountains around here, the extra "help" to get up the slopes would be fantastic. I can imagine that with the power increase, I will probably lose some mpg just enjoying the power but then Ill pull it back to normal driving. Doing some tests on the motor right now to make sure that she is healthy enough for it and then Ill go from there.