FUSO 4D34T3 fueling/power gain mods Questions

scubagai

Observer
Hello all. Been a while since I've been on here. I live in Northern California and have a 1992 Fuso FG439 with the 4D34T3 motor. The US spec one is turboed, and comes with a Zexel MD(Bosch inline prestroke control injection pump), and has an exhaust brake. We are all aware that these are torquey machines, detuned, and mated with stout running gear to let these trucks run for a million miles. Mine has 100,000 easy miles on it. I have no intention of driving it 900,000 more miles. I would like to drive another 150k to 200k on a slightly peppier motor. I am not looking for massive black smoke churning horse power/torque gains, however, I would like to get out of my own way going up grade, and be able to pass other "slower" vehicles on grade. I am not looking to do anything that would hugely effect engine longevity or fuel economy, but do realize that these are tradeoffs with making more power. I am ok with top speed of 62, i just want something left when passing.

Currently, I have 285/75/16 Hankook Mud terrains on 16" Marsh racing singles. These seem to help keep rpms down once at highway speed. I have a s280 communications shelter mounted on the back, which sticks above the cab about 18". So, I have a brick that i would like to throw more fuel at. I am not looking to be talked out of power mods. I would appreciate only positive responses from those that have information about producing more power out of these motors. I drive a 12 valve cummins(turboed/intercooled) on a daily basis, and a wrx, neither of which is hopped up too much. Fuel screw turned on cummins and cobb running stage 1 map on wrx. I am not throttle masher either. I have researched this subject via all types of forums, but most are inadequate at explaining it(plus most seem to be for swaps into landcruisers).

Ok, so the questions: How do I get more power out of this motor?

(The following are my current thoughts)
Air and fuel
I am planning on a 3" exhaust with a high flow muffler. However, I would like to remove the stock exhaust brake and find a 3" one to replace it. Any ideas where to source that?
I am planning on modifying the air intake...how, I don't know, but I would like less restricitve flow.
I am willing to purchase a turbo upgrade, if needed.
I am willing to have the pump tuned, if this is effective.(I have heard there is a shop in Redding, CA that does good pump tuning).

All of your positive comments and assistance are much appreciated.....you people from Oz probably have the most experience with this.
 
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SkiFreak

Crazy Person
If Fuso has not changed their exhaust brake assembly significantly between models, then my solution may be a viable option for you too.

On my FG84 I replaced the OEM 2-1/4" exhaust butterfly valve with a 3" one from an Isuzu FVR33, 1996-2000, with a sitec 6hh1-s engine.
This was a relatively simple changeover, as many of the parts were interchangeable between the two units.

my_exhaust_brake.jpg
 
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scubagai

Observer
Thanks. I will look into the exhaust brake info. My exhaust guy wants to do it all in one shot, so I'd like to have the replacement brake when I go to get the work done.
 

SkiFreak

Crazy Person
The only other thing I had to do was make the two flanges for either side of the butterfly assembly. These had a 45 degree angle on the main hole, which allowed for mating to the butterfly assembly. The taper provides the seal; there is no gasket.
 

scubagai

Observer
Thanks. As far as turning up the pump. What is the procedure? Can it be done on the motor or does it have to be removed? Does it require new govenor springs, etc?
 

scubagai

Observer
Thanks. As far as turning up the pump. What is the procedure? Can it be done on the motor or does it have to be removed? Does it require new govenor springs, etc?

And, with the air filter mod....I was thinking of a 4" air ram snorkle tip, 4" pipe to a larger air box with a larger filter. Any suggestions on filter box/filter size/manufacturer?
 

red EOD veteran

Adventurer
Not familiar with that engine in particular but being the same displacement and power ratings of the Isuzu 4bd and Cummins 4bt series the same upgrades should apply.

Upgrade to a 4" exhaust
Upgraded turbo to one in the hx30/hx35/s200 range, depending on your planned rpm. Need more info to determine which turbo is best for your goals.
Turn up the fuel to match the new turbo.
Possibility of requiring head studs.

That will get you started. From there stepping up to a compound turbo setup and having your injectors honed/ported for more flow would be the next step. In uncharted territory with that engine, no known weak spots to upgrade.
 

scubagai

Observer
Howdy. Still researching. I am thinking of going with a Donaldson ram intake snorkel head, but the outelet/intake to the filter is 6.25 inches. I was thinking of going with 4" intake aluminum piping to the air box...and going up one in size for the filter/housing. So, what do you think about the connection/reducer for the ram head to inlet pipe?
 

LeishaShannon

Adventurer
We're in the middle of installing a Donaldson filter and ram head on the NPS. I'm not sure what CFM your engine needs but the filter for ours has a 3.75" inlet and the ram head is 4" so I have a silicon reducer on the filter with 4" aluminium piping to the ram head. Its not ideal but it seems everything on our truck is a different size.. the filter outlet is 3.5" and the intake on the engine is 3.25" !
 

DzlToy

Explorer
join ih8mud

search for 4D34 engine swaps into 80 series Landcruisers.

Read multiple threads on tuning and modding 4D34 engine.
 

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