The 4JB1-TC in my jeep now has 15,000km on it with no problems.
Nice family vehicle.
So now I'm starting to get "itchy" again and looking for something to build. I just bought a
1999 Dodge Dakota 4X4 and have been measuring up the Isuzu 4HF1 sitting outside.
Anyway thats another story and not what this post is about.
How much turbo boost can the 4JB1 take? This one is set at 8 PSI, how much can
I crank that up and what other mods would I have to do?

Thanks
Randy

Mine runs at 12psi boost but non-intercooled. Yours at 8 psi may be the same net boost with an intercooler.
For more power there are other things to can do also.
I don't know if you would have do any mods other than adjust the boost.

But if you are after more power add a 2.5" exhaust system from the turbo back. The turbo then comes in earler and the engine pulls harder.
You can crank up the fuel delivery, if it starts smoking it's to much.
You can advance the timming in conjunction with the fuel crank.
A couple guys over here have done just that with a dynotune for the fuel and timming advance and report a change of 117hp to 150hp and 225Nm to 320Nm at the fly wheel with these 3 changes. This is for the non intercooled 4JB1-T

I've done the 2.5" exhaust system and yet to do the rest but already it feels like a differant vehicle.

I installed 2.5" exaust when we did the conversion but I also installed a new Jeep V8 muffler. You can hardly tell the thing
is running from the back. I propably could have done without the mufler?
How do you crank up the fuel?
I'm also changing the air intake from a 3' long 1.5" pipe to a 2' long 2" pipe to help air flow.

Thanks for any help.

The 1.5" inlet will be restricting the flow a little. everyone over here fits 3" snorkles. 7" square coss section vs your 1.75" square cross section

I'm the odd one out fitting a 2.5" snorkle as the air box inlet is 2.5" it made sense to me.

Cranking up the fuel, I'd need to take a photo for you or scan a diagram, but this may help.

http://www.tstproducts.com/pump_adjustment.html

May I suggest checking the exhaust gas temperature as you increase boost.

Wouldn't want you to melt the insides of your power plant.
:-)
Eric

The 2.5" exhaust should help lower temperatures.
But I haven't measured or confirmed that.

A lot of the Toyota surf/hilux diesels warp heads over here with overheating. A 2.5" exhaust apparently makes the problem go away.

Thanks to everyone for the info. I increased the inlet pipe to the turbo to 2.25" and shortened it a foot, this
made the boost jump up much quicker.
I also (with much dificulty) adjusted the pump 3/4 of a turn and it made a dramatic differance in power
with no smoke. I think I will leave it at this and move onto the 4HF-1 Dakota / diesel project.
Thanks again for the help.
Randy

hello i am new here and know very little about diesel
i woudl like to know if the 4JB1-TC would be a good swap in my cj5. i have a t-18 tranny with granny low and 4.56 gears with 35" tires

i can probably make the adapter between the bell housing and tranny or use a gm bellhousing and modafy for a ford tranny

my other options would be a vw 1.9td i would like to know your opinion

I'd be much interested in the same project. I have a 1979 J10 that needs a new motor--might as well be a diesel! And an isuzu diesel to match the 223 that's in my 1979 Postal Jeep would be good It's been a while since I posted, but my postal jeep conversion is going well--engine is in and running - I can even start it from the cab now (fixed all those wiring gremlins). Drivelines are supposed to be done next week. Reweld the rear springmounts, and I should, in theory, be able to move it under its own power. Wooo!

Anyways, never one to learn from past hardships, I'm thinking about tackling my J10 next, but I'd like to reuse my existing T18 tranny this time. So I would need to come up with adapters as well. And the 223 would be a bit underpowered for a "real" truck, I'm thinking <img src="/forums/images/graemlins/wink.gif" alt="" />

Cheers all,

I've done a little mucking around with pressure gauges, temp sensors and the like.

More boost does increase the efficiency of your engine (higher effective comp ratio) which results in more power for the same fuel. But the back pressure in your exhaust manifold also starts to choke the engine more (my tests show a rough 2:1 back pressure to boost, gets worse near the limit of your turbo).

So basically you reach a point where you start to go backwards. I'm running 15psi without much intercooling (10%), the old turbo would blow up to 20 but it was an exercise in futility.