Build Mitsubishi 4D34-3AT3B diesel swap into 94 FZJ80

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Just a quick mileage update - I have been getting about 340 miles out of a tank of combined city and highway driving at 70 mph. This is with 295s and a roofrack, in hilly road conditions. To compare, the truck used to get around 200 miles for the exact same usage.

I would bet it would be significantly better on the flats at constant highway speeds. I took it on a backwoods fishing trip and it still managed to get 250 miles to a tank, with most of that on sand/dirt roads and a lot of low speed crawling.

The power is acceptable but I am going to be looking into some mild upgrades, finishing the 3 inch exhaust, and working on the turbo. Right now the wastegate is disconnected, I need to get a replacement as it leaks slightly. It's great around town but on the highway it feels a bit winded. I'm also not quite at 30 mpg yet, so I will be starting to accumulate parts for a part time 4wd swap.
 
Works great, with a few quirks. It does not stay in first very long. A few seconds and you are in 2nd. On steep hills, like my driveway, it will not downshift into first unless you really floor it, then it shifts down and immediately up again. It will just slip the torque converter in 2nd all the way up. I don't think this is a defect, it's just the way it is programmed. I think that with the original axle ratio, the Fuso would have used 1st as a "low" only in extreme situations. The straight cut gearset also whines a bit, kind of like the first gear in a Dodge K car.

It's not really an issue as, if you really want to use a lower gear, you can throw it in 1st, or shift into low range. I should caution that my driveway is steeper than most any road you will encounter and I use low 1st when pulling a trailer as it's quite the climb.

It is pretty much exactly like the original gas drivetrain with respect to load and shifting. The 1FZ needed to downshift into third to hold 60 mph on a big hill on my way to work. This one needs to do the same. It will hold 55 mph in 4th, then you give it a bit more pedal, and it drops into 3rd and away you go.

I should mention tha i have an unfortunate ATF leak from around the front pump, so I will have to pull the trans and re-seal it at some point.

A few cruiserheads have had a chance to drive it and they all think it works slick. In low range first it is an absolute bulldozer and puts the 1FZ to shame.
 
sounds like it is beggin for a 5 speed!
 
Sorry SH, I never made it to Jersey, I will be down soon enough and will let you know.

A few random things I wish I would have known while doing the swap:

There is a water outlet on the timing cover that ends up very near the power steering box/frame area. It sticks straight out the side and is for the heater. If you can, unscrew the nipple (or drill it out, not sure how it is affixed) and put a 90 degree elbow in there. The hose fits, but it has to make a sharp bend to clear the frame and I will eventually have to address this and put an elbow in. Much easier with the engine out.

I have found a major issue with the timing, which may explain the reason why the engines are timed at 3BTC instead of “sooner”. Originally when I put mine together, I replaced the injection pump and had blue smoke issues right off the bat due to severely retarded timing. I also had an issue with a recurring check engine light due to a pre-stroke actuator code. So, I bumped the mechanical timing, figuring that I had a mechanical timing issue due to the pump swap.

It got better, but I still had the fault code, which I eventually traced to reversed pins for the prestroke relay. Once I fixed this, the engine started performing very differently. It’s almost like it went from badly retarded to, well, quite a bit of advance.

Now that I have run a few tanks through it and had a baseline, I decided to look into the timing. I did some testing with a spare prestroke actuator, and it looks like although the mechanical timing is quite retarded, the prestroke actuator advances it in a massive way depending on engine load, but also advances it at idle. If I unplug the actuator and start the engine, it is lazy and sounds like the timing is way retarded (like an old Benz). And with it plugged in, it’s much louder.

Then I got to thinking that perhaps I had made a mistake by bumping the timing forward, when I had a non-functioning prestroke actuator (due to the relay issue).

So last night I pulled the timing back to stock marks, and boy did it ever make a difference. The annoying vibrations are gone, the low end torque has gone up, and the highway performance is about the same. I also have a feeling that the mileage may improve as the dramatic reduction in vibration is an indicator that I had the timing way too advanced.

I’m going to run another tank through it with the timing the way it is now and see if the mileage improves. If it gets worse, I may try and advance it a bit (not as much as before) but I have a gut feeling that it will be better. . I still have the wastegate stuck closed (Mitsubishi sells the wastegate actuator as an assembly with the turbo so I have to get a universal one and make it fit), and I believe this is the reason I am not getting as much top end as I should. The engine is designed with a pop-off valve to deal with any boost over 15 PSI, and in my case I am likely over speeding the turbo and just pumping a ton of air for no reason, with massive restriction in the exhaust.

So far I love the truck, it's a thousand times better than the gasser, it gets good mileage, sounds like a bus, lots of torque, tows OK (could use more power but I think that is my wastegate issue) and the mileage is pretty good, and I think I can improve on it. Like I said in the beginning, I want 30 mpg, not there yet...
 
northernrighty said:
sounds like it is beggin for a 5 speed!
Click to expand...

I just wanted to deal with this comment.

To me, the whole point of this swap is that you can use the stock trans - Auto. If I was putting a 5 speed in, I would probably have used something totally mechanical (4BD1T, 4BT, 15BT etc) and gone a different route. I think the Mitsu 4D3 is the easiest engine swap for an 80 series out there unless you go Toyota. However, a big part of that is the A442F trans.

I'm trying to be totally honest in my descriptions of how it performs so I am listing the negative and perhaps not putting as much time on the positives. I love the auto, I did not want a 5 speed for this truck. I have a Toyota 1PZ in the garage that could have gone in this truck with an H150 but I wanted to stick with auto. My wheeling truck will have a 5 speed, but for a daily that sits in traffic, I'd rather have the slushbox, especially since it's so freaking heavy duty.

So, if you are reading this, contemplating this swap, and you wanta 5 speed, I would find another option. For the ones that like an auto, this is where it's at....
 
Fromage said:
Sorry SH, I never made it to Jersey, I will be down soon enough and will let you know.
Click to expand...

Not a problem, I'm actually putting my trans back together tomorrow. If all goes well I'll be getting started on my swap soon enough!

Fromage said:
A few random things I wish I would have known while doing the swap:

There is a water outlet on the timing cover that ends up very near the power steering box/frame area. It sticks straight out the side and is for the heater. If you can, unscrew the nipple (or drill it out, not sure how it is affixed) and put a 90 degree elbow in there. The hose fits, but it has to make a sharp bend to clear the frame and I will eventually have to address this and put an elbow in. Much easier with the engine out.
Click to expand...

This is the kind of stuff I love to hear. I'll take a look at that ASAP and see what I can come up with.

Fromage said:
I have found a major issue with the timing, which may explain the reason why the engines are timed at 3BTC instead of “sooner”. Originally when I put mine together, I replaced the injection pump and had blue smoke issues right off the bat due to severely retarded timing. I also had an issue with a recurring check engine light due to a pre-stroke actuator code. So, I bumped the mechanical timing, figuring that I had a mechanical timing issue due to the pump swap.

It got better, but I still had the fault code, which I eventually traced to reversed pins for the prestroke relay. Once I fixed this, the engine started performing very differently. It’s almost like it went from badly retarded to, well, quite a bit of advance.

Now that I have run a few tanks through it and had a baseline, I decided to look into the timing. I did some testing with a spare prestroke actuator, and it looks like although the mechanical timing is quite retarded, the prestroke actuator advances it in a massive way depending on engine load, but also advances it at idle. If I unplug the actuator and start the engine, it is lazy and sounds like the timing is way retarded (like an old Benz). And with it plugged in, it’s much louder.

Then I got to thinking that perhaps I had made a mistake by bumping the timing forward, when I had a non-functioning prestroke actuator (due to the relay issue).

So last night I pulled the timing back to stock marks, and boy did it ever make a difference. The annoying vibrations are gone, the low end torque has gone up, and the highway performance is about the same. I also have a feeling that the mileage may improve as the dramatic reduction in vibration is an indicator that I had the timing way too advanced.
Click to expand...

This makes me glad I had a running donor, I'm not touching anything, just putting it in as it came out.

Fromage said:
I’m going to run another tank through it with the timing the way it is now and see if the mileage improves. If it gets worse, I may try and advance it a bit (not as much as before) but I have a gut feeling that it will be better. . I still have the wastegate stuck closed (Mitsubishi sells the wastegate actuator as an assembly with the turbo so I have to get a universal one and make it fit), and I believe this is the reason I am not getting as much top end as I should. The engine is designed with a pop-off valve to deal with any boost over 15 PSI, and in my case I am likely over speeding the turbo and just pumping a ton of air for no reason, with massive restriction in the exhaust.
Click to expand...

You are probably causing seriously high intake air temps in this situation by running that turbo that fast. I'm willing to bet you're going to see improvements just as noticable as your timing issues when this is resolved.

Fromage said:
So far I love the truck, it's a thousand times better than the gasser, it gets good mileage, sounds like a bus, lots of torque, tows OK (could use more power but I think that is my wastegate issue) and the mileage is pretty good, and I think I can improve on it. Like I said in the beginning, I want 30 mpg, not there yet...
Click to expand...

Are you talking 30MPG US or imperial? Because if that's US, that's insane.

Fromage said:
I just wanted to deal with this comment.

To me, the whole point of this swap is that you can use the stock trans - Auto. If I was putting a 5 speed in, I would probably have used something totally mechanical (4BD1T, 4BT, 15BT etc) and gone a different route. I think the Mitsu 4D3 is the easiest engine swap for an 80 series out there unless you go Toyota. However, a big part of that is the A442F trans.

I'm trying to be totally honest in my descriptions of how it performs so I am listing the negative and perhaps not putting as much time on the positives. I love the auto, I did not want a 5 speed for this truck. I have a Toyota 1PZ in the garage that could have gone in this truck with an H150 but I wanted to stick with auto. My wheeling truck will have a 5 speed, but for a daily that sits in traffic, I'd rather have the slushbox, especially since it's so freaking heavy duty.

So, if you are reading this, contemplating this swap, and you wanta 5 speed, I would find another option. For the ones that like an auto, this is where it's at....
Click to expand...

I'm glad you addressed this comment, I feel the same way. The AW450 makes this conversion almost a no-brainer when it comes to simplicity and efficiency. So few components are changed, it's really a very cool conversion in my book.
 
Updates...

I pulled the old wastegate off and bent the pressed lip up, and removed the "hat". Sure enough, the diaphragm has a 1/2 inch tear. I sealed it up with silicone and it's curing, doubt it will hold but it might allow me to test drive it and see how it should be performing.

This wastegate issue has me a bit worried. All the wastegate actuators I have seen have a smaller head than this one does. I had a Volks TDI one stashed away in the basement and it's much smaller, so I question its ability to keep the wastegate shut at 12 PSI without being sprung super tight.

Years ago Banks came out with an increased cross section actuator called the "big head". If they weren't so expensive I might try one.

I'm debating buying a diaphragm for a Tial wastegate on ebay and seeing if I can make it fit. It would be great to only have to replace what is actually broken...
 
Same question I asked in SuperHatch's thread - what year did Mitsubishi switch to the Aisin AW450 transmission? I have a friend with a 1992 truck that has the Jatco automatic.
 
Updates:

I bought a wastegate on Ebay and installed it, but it was a 1 bar model and I thought it would work out OK by setting it up a bit loose. I also installed a boost gauge.

The 4D3 has a wastegated turbo. I think the stock bypass pressure is around 7-8PSI. It also has a pop-off valve in the intake, to make sure boost never goes above 15 PSI. So, I set the replacement wastegate to open around 13 PSI, thinking that would raise the boost a bit without opening the pop-off valve.

Well, it did not. All I ever see on the boost gauge is 10 PSI, regardless of how much load, heat, acceleration, etc. Based on what I am seeing, I think the computer starts de-fueling when the MAP sensor sees 8-10 PSI, and right now my wastegate isn't doing anything, except restricting flow, and the computer won't let boost increase high enough to open up the bypass.

So, I disconnected the wastegate completely, (as in, always open) and I went for a ride. Although it took a long time to build boost, I saw 5-6 PSI with the wastegate fully open, and it seemed to breathe a lot easier.

The next step is to get a wastegate actuator that is rated for 7-8 PSI, and see how the engine responds to having a much more free-flowing exhaust. I also need to finish the exhaust I am building for it, out of stainless, and I think both those things will improve performance a lot.
 
How frustrating to be chasing these wastegate issues!!! I'll let you know when my wastegate opens as soon as I can.

FWIW, I attached what the FSM says... 36kPa is 5.22psi... quite low!
boost.webp
 
5psi sounds strange. I'd expect at least 12psi to make the rated power and burn clean.

What air sensors do these engines have? Airflow or just MAP?
 
Dougal said:
5psi sounds strange. I'd expect at least 12psi to make the rated power and burn clean.

What air sensors do these engines have? Airflow or just MAP?
Click to expand...

Thr 5 PSI is in the service manual and is just a test with the engine free revving while not under load. It does not really relate to anything other than the OEM's stated service criteria but it does verify that my turbo is working correcty as per their criteria. I am susprised that the wastegate pressure and max boost is not listed anywhere in the manual.

air temp (post cooler), map. That's it for air monitoring.
 
Update #1 I actually used susprised in a sentence. I need to re-read.

Update #2 I am getting closer. I think my 10PSI ceiling is not engine tune related but the point at which the wastegate is opening due to exhaust gas pressure. Even with the wastegate hose unhooked, I was seeing a maximum value of around 10PSI. I adjusted it tighter last night and I am now seeing 11 PSI. I will ratchet it down much tighter tonight to see what the true maximum is (I suspect it will be 15 PSI, where the pop-off valve opens). Noticeable difference from 10 to 11 PSI. If I can get it to 14PSI it will be aweome. Then to plug the pop-off valve.
 
Fromage said:
Update #2 I am getting closer. I think my 10PSI ceiling is not engine tune related but the point at which the wastegate is opening due to exhaust gas pressure. Even with the wastegate hose unhooked, I was seeing a maximum value of around 10PSI. I adjusted it tighter last night and I am now seeing 11 PSI. I will ratchet it down much tighter tonight to see what the true maximum is (I suspect it will be 15 PSI, where the pop-off valve opens). Noticeable difference from 10 to 11 PSI. If I can get it to 14PSI it will be aweome. Then to plug the pop-off valve.
Click to expand...

Right, but wouldn't that cause a lean condition? Or would the programming in the ECU read the additional boost at the MAP sensor and increase fueling to compensate?
 
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