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  #21 (permalink)  
Old 25th April 2013, 11:20 AM
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And I should've specified what I call BIG boost levels and EGT's, anything above say around 15 to 20 psi and 700degrees should be avoided. The factory Alfin turbo pistons are quite a bit 'stronger' and supposedly dissipate heat better, even without the oil cooling jets.

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Old 25th April 2013, 11:54 AM
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So whilst we are all waiting for mikes outcome, what needs to be done to an engine to say handle 30psi and 700egts all day long. Good head gasket, pistons, head studs etc....?????
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Old 25th April 2013, 12:01 PM
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Sorry to hear that Mike - fingers crossed and good luck.

Did you have the head off, and were the bolts tightened to 4BD1T specs or 4BD1?

Dinty had a thread a while back where his 4BD1 started knocking and that turned out to be a cracked piston.

For the 4BD1T (I don't know about 4BD1 changes), in Oct 88, Isuzu changed the piston design, improved piston cooling and changed the turbo to increase the durability of the piston. See pics below.

The changed piston design were:

1. Added slight radii along 2 areas on the lip at the entrance to the combustion chamber.
2. Increased the thickness under combustion chamber.

The changes to the piston cooling were:
1. New oil pump for 20% increase in flow
2. smaller nozzle (2.0 mm changed to 1.6mm)in the cooling jets.

The change in the turbo was for a larger nozzle area in the turbine housing to reduce reduce exhaust manifold pressure and temperature.

We should remember this engine was for a heavier truck than our Land Rovers, and those trucks are expected to be driven harder (higher duty) than we drive.ours.

Also as Dougal has posted, increased boost pressure with lower egt's is better for the engine than higher egt. The extra air mass, above what is required for combustion) takes a considerable amount of heat out of the cylinder. So long as exhaust manifold pressure is not too high - I believe I said in the VNT thread, you need to get those vanes opening early on the VNT turbo.

Rarely do people monitor the pressure in the exhaust manifold, because of the issues with temperature and soot. IMHO, it is a measure which is very useful, arguably as important as egt and boost pressure.
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Old 25th April 2013, 12:05 PM
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Hi all, I ran a N/A 4BDI in my 1985 County 110 wagon for 15 years with the LT95 gearbox. There were no engine issues at all and the only transmission issue was the need to replace the transfer mainshaft and bearings . I also had to repair the clutch throwout pivot point as it failed. My local engineering people drilled out the pivot point and pressed in a steel one in its place. Very satisfactory outcome.It was a very good bush vehicle but needed a fifth gear for highway use. Cheers, 130man.
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Old 25th April 2013, 12:26 PM
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In n/a spec it'll go forever, but talking Turbo spec here.
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Old 25th April 2013, 12:29 PM
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Quote:
Originally Posted by Vern View Post
So whilst we are all waiting for mikes outcome, what needs to be done to an engine to say handle 30psi and 700egts all day long. Good head gasket, pistons, head studs etc....?????
In reality, who would run 30psi and 700C all day long?

With my 89 4BD1T engine the fuel injection pump has been calibrated to get close to the maximum fuel rate possible, 180cc/1000 strokes, without significant modifications. I replaced the stock lift pump with an AirDog pump to ensure plenty of fuel in the fuel gallery.

As such I can have enough fuel to justify 30 to 40 psi of boost with intercooling, and have compound turbos, which should do that, when I get around to it.

I replaced the stock valve springs, with stronger after market springs from a chevy V8, to ensure the high boost pressure doesn't cause them to stay open.

I replaced the head bolts with ARP studs and used a stock genuine Isuzu MLS head gasket.
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Old 25th April 2013, 01:19 PM
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In reality, no one. What I meant was for an engine to withstand this and not melt a piston etc... what would be the optimal engine mods to be done, in particular to an early model non Turbo model as these seem to be what most people have.
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Old 25th April 2013, 01:33 PM
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JC, JC! No need to do this to everyone! All of a sudden, out comes the stories of head gaskets, melted pisons and weak spots in the 4BD1! Makes my TDI sound like a dream boat.

That aside, sorry to hear of the trouble Mike. Crappy luck compared to most peoples Isuzu experiences... I'll be following and hoping there is an easy fix. *fingers crossed*
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Old 25th April 2013, 01:48 PM
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No need to cause mass panic - I'd been running mine VERY conservatively the past few weeks, low egts from the get go, oil and water checked twice a day, and haven't pushed the engine at all really. It's one of the few times I can write something off to the ****tiest of luck. So no need to trade in the Isuzu land rovers for Toyota's just yet :-)

At this stage I'm guessing by the feel and balance of the engine, but I think I'm looking at just one piston, and that the future consists of a re sleeve and piston replacement. At least with the Isuzu you can buy parts by the pot.
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Old 25th April 2013, 02:04 PM
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It is crappy luck mike, you must have upset someone along the way. That was one of the smoothest and quietest 4bd1's I've ever heard
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