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Isuzu reliability tester
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I was wondering if anyone has heard of high hp numbers out of the 4bd? What is the highest hp/tq? Do you guys thing 250-275 is an unreasonable number?
 

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I was wondering if anyone has heard of high hp numbers out of the 4bd? What is the highest hp/tq? Do you guys thing 250-275 is an unreasonable number?
I'm aiming for around 200 hp, from turbo and exhaust mods for around 30 psi boost, air to water intercooler and fuel injection pump adjustments.

My engine is going back together after being balanced. Head bolts have been replaced by ARP studs.

I still need to find better valve springs, have the pump serviced and adjusted, mod the exhaust etc.

I will try an air to water intercooler that I had made for another engine. If it proves too small, then will get something better.

Edit: I tried to get ARP studs to replace the main bearing bolts, but was told they don't make anything that large.
 

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Isuzu reliability tester
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Discussion Starter #3
I could be wrong but I bet 200 should be fairly easy to get with the mods you plan on doing. I have already talked with my local injection shop about modding the pump and the injectors they have been researching what can be done and say that my goal shouldnt bbe a problem. I just wanted to hear from people like you that have or are doing it. I didnt know that arp made head studs for our motors. hmm I may needa set of those.

Have you called comp cams to see about some custom valve springs, or to see if they have any suggestions?
 

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I could be wrong but I bet 200 should be fairly easy to get with the mods you plan on doing. I have already talked with my local injection shop about modding the pump and the injectors they have been researching what can be done and say that my goal shouldnt bbe a problem. I just wanted to hear from people like you that have or are doing it. I didnt know that arp made head studs for our motors. hmm I may needa set of those.

Have you called comp cams to see about some custom valve springs, or to see if they have any suggestions?
I think 200 will be enough for what I want. I do some long off road trips to remote areas and reliability is important. I would be concerned about the head gasket at higher boost pressures, without o-rings. My intention is to use ARP studs and a little more tightening tension than stock recommendation for a 4BD1-T.

The ARP studs were off the shelf items.

14 studs part number ARP-AU5.600-2LB
4 studs part number ARP-AU4.950-2B
2 packs 12 point nuts part number ARP300-8338
2 packs washers part number ARP200-8536

I didn't try to get studs for the 2 bolts that have a stud above the bolt head (for the fuel filter mounting bracket). I will use the same studs as for the other 2 short studs and customise the bracket.

I will have to pull my finger out and chase up some valve springs. I'm in Australia so will try locally first.

Good luck with your engine, I will be interested in how you go.
 

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Isuzu reliability tester
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Discussion Starter #5
Thanks for the part numbers I may look into getting some of those. I want to see what kind of boost I can get out of the new turbo first though.

I am not suprised this thread hasnt had a lot of response. I dont think anyone has pushed the limits of the 4BD.....

Sounds like a job for me:)
 

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I also think 200hp is stupidly easy to get.
The pump appears to put out enough fuel for far more than 200hp simply by turning screws.

According to my viaduct-dyno (man made viaduct which I know exactly the slope of, combined with a few calculations) I've got 500Nm of torque at 2000rpm with only more fuel and boost (no intercooler, no pump mods, T25 turbo at 20psi max). I am not at the limit on the fuel delivery screw.

If you can produce 500Nm at 2800rpm then you've got your 200hp. I think a larger exhaust and I'd be almost there. Larger exhaust and intercooler and I'd be easily past.
 

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Isuzu reliability tester
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Discussion Starter #7
so dougal what do you think I could make hp/tq wise with the HY35, intercooler, and turning pump screws?

I will get the local injection pump shop to mod the injectors and IP later if necessary.
 

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so dougal what do you think I could make hp/tq wise with the HY35, intercooler, and turning pump screws?

I will get the local injection pump shop to mod the injectors and IP later if necessary.
The fuel pump delivers up to roughly 120cc/1000 shots without any internal mods.
With a very conservative BSFC of 250g/kwh that equates to 550Nm.
With a possible BSFC of 220g/kwh that equates to 625Nm.
I'd expect to run up against the limits of an unmodified pump around there somewhere.
Injector nozzles is something I haven't monkeyed with at all. Mine had new nozzles fitted at a ludicrous price about 5000km ago. It gave a cleaner startup but no fuel economy or power change. I have the original tips in a box here somewhere if you'd like a photo.

Engine speed?
The governor setting appears different depending on what your engine was fitted to. Mine was out of a japanese truck and it runs to 3600rpm. This can be changed by simply adjusting the limit screw on the top of the pump. One changes idle speed, the other max rpm.

Engine strength?
This is the big question mark. As far as I know no-one has pushed one of these engines to breaking point in the pursuit of power, so one of us will be the first.:grinpimp:

Some different ways of acheiving 250hp.

600Nm at 3000rpm is 255hp.
500Nm at 3500rpm is 250hp

Airflow:
To me the original intake manifold is going to starve the end cylinders of air. They modified the design of these later on to look and flow better, but a reverse header type design might be necessary to keep each cylinder getting it's fair share of air.
You would also probably want a custom exhaust header, equal length type thing. The bigger runners may lose a little down low, but once the turbo is spooled up the benefits should be there.

Boost:
NEF make a 3.9L engine in the cursor range which produces 490Nm and meets Euro 2 on 25psi boost. Max intake temp is 50 deg C.
Factor in the derating for industrial application and the emissions limits and I think 30psi boost should get us all we need for EGT and smoke control.
I don't know what backpressure limits Isuzu work to. But I've routinely hit 40psi in my exhaust manifold and accidentally hit 60psi (I imagine valves were floating at that point).
I've had backpressure/boost ratios at 1:1 even when running a little T25 turbo at 20psi which is right off the map, so hitting 30psi boost while keeping under say 40psi backpressure should be acheivable with good manifold design.
Unfortunately I've never seen a map for a holsett HY turbo, so I'd just be guessing what they can do.
 

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Isuzu reliability tester
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Discussion Starter #9
Given this some thought have you??? :) I can live with around 250hp for a little while, I think that would push my 4000 pound 2wd truck around ok.
Then when that gets old (roughly 2 weeks lol) I will be dropping it off to have the pump modded. I would like to see what one of these will take.

Dougal any pics of what you think would be a good intake design?

I agree about the 2 outer cylinders being starved a little more than the 2 center cylinders. I guess it would be as simple as makeing an intake with equal length runners since it only flows air and no fuel.
 

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Yes equal lengths and smooth bends will give you excellent results.

Obviously the factory didn't do it for two reasons.
1. It'd cost more
2. It wouldn't be as compact.

But for us they don't matter soo much.
 

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Isuzu reliability tester
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Discussion Starter #11
Hey bush did you ever find any valve springs? I have been way too busy messing with this fueling problem to even look, just curious.
 

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Hey bush did you ever find any valve springs? I have been way too busy messing with this fueling problem to even look, just curious.
Not yet, but I have been far too busy with other distractions.

Regarding the inlet manifold, I'm in the process of incorporating an air to water intercooler into the manifold. Waiting for one more part to be machined, then it can start going together. When I have all parts in my hands, the plan is to split the manifold lengthwise and weld the part with the 4 outlets to the case of the intercooler.

The pics show views of the tube bundle from different angles, the channel that bolts the the rear of the bundle. Laminova intercooler cores, which slide inside the tubes. The cores seal in the recesses in the channel.

The length of the intercooler matches the length of the inlet manifold. The centre distance between cores is 48mm (1.89").
 

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Okay, first off that looks like quality work :D .

But I'm somewhat confused (or maybe not, it's why I ask), the air runs across the tubes laterally, and the water flows through the tubes (inside the "Laminova intercooler cores")?
The air enters the slots in the tubes, passes over the fins on the outside of the laminova core, and leaves though the slots on the opposite side of the tube.

My intercooler is set up so the air from the compressor enters the slots in the upper 4 tubes, passes the fins on the cores then enters the slots in the lower tubes and makes a 2nd cooling pass of the lower cores.

The cooling water runs longitudinally through passages below the fins. The way my intercooler will be set up, the water enters the front of the lower 4 cores and returns through the front of the upper 4 cores. The cross drilled passages that can be seen in the channel, direct the water from the rear of the lower cores to enter the rear of the upper cores.

These laminova cores are reputed to be very efficient.
 

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Isuzu reliability tester
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Discussion Starter #18
Oh thats very very nice stuff bush. Great job! cant wait to see it finished.
 

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Last machined component for my air to water intercooler.

This is the head that goes on the front end of the intercooler. The 2 lower threaded ports are for connecting the cold water hoses. The heated water exits (and returns to the dedicated radiator) through the 2 upper threaded ports.
 

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Isuzu reliability tester
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Discussion Starter #20
That thing looks too nice to hide under a hood. Will you be compareing before and after intake temps? I would be very interested to see how this does over a very large air to air cooler.
 
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