1HZ vs 1HD-T - Pros and Cons

mudgudgeon

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Saying 10psi max is the absolute worst advise for 1HZ. It's been proven time and time again that boost doesn't hurt them. They love boost. Fuel is the issue, not boost.

Agreed the idea that boost should be less than 10psi is outdated.

A well matched turbo and boost compensator, intercooler, exhaust, and correct tune are the important things.
 

mudgudgeon

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A 1HZ is simple, reliable and easy to repair.

In comparing a 1HZ and 1HD-T, saying one is simple as a plus is kind of pointless. The two engines are 95%+ the same. Simplicity is equal
 

mudgudgeon

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Limiting boost to less than 10psi was probably good advice back when the turbo's commonly being used were mismatched and sourced from petrol engines.
If the turbo is running outside its efficient range and heating the intake air too much, then yeah, limiting boost makes some sense.

There's no shortage of aftermarket turbo options that are well matched to these diesels.
It makes more sense to use a well suited turbo that is capable of supplying a healthy increase in air flow and boost without over heating charge air.
Then boost is no issue.
 
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Prices to get a Jap import diesel motor here are quite high - 1hdt about A$10k up to about A$15k for 1hdfte.

don't know what a 'crate' 1hz would go for here.
 
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Agreed the idea that boost should be less than 10psi is outdated.

A well matched turbo and boost compensator, intercooler, exhaust, and correct tune are the important things.

Depends on your pistons and compression. High compression and unreinforced pistons don't take kindly to too much boost. If you've got Alfin pistons then they'll be okay with a little more. But ultimately putting bigger boost into a high compression IDI engine means you're doing it wrong.
 

mudgudgeon

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Depends on your pistons and compression. High compression and unreinforced pistons don't take kindly to too much boost. If you've got Alfin pistons then they'll be okay with a little more. But ultimately putting bigger boost into a high compression IDI engine means you're doing it wrong.

Lots of vague terms there Dougal.

Define these for us in context of this chat.

too much boost
Bigger boost
High compression
A little more ( more than what?)


I boosted my 1HZ with 14psi, was contemplating bumping that to about 18psi. I wouldn't go much beyond that on a 1HZ.

14 psi certainly woke it up.
There's loads of takes of woe from way back with turbocharged 1HZ over heating, cracking pistons etc with 7-10psi boost.
From various forums the common denominators are low boost, over-fueled, and no EGT monitoring, (or EGT post turbo), and old school turbos used.

With newer turbos, more boost, the seem to do a lot better.
 
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Lots of vague terms there Dougal.

Define these for us in context of this chat.

too much boost
Bigger boost
High compression
A little more ( more than what?)


I boosted my 1HZ with 14psi, was contemplating bumping that to about 18psi. I wouldn't go much beyond that on a 1HZ.

14 psi certainly woke it up.
There's loads of takes of woe from way back with turbocharged 1HZ over heating, cracking pistons etc with 7-10psi boost.
From various forums the common denominators are low boost, over-fueled, and no EGT monitoring, (or EGT post turbo), and old school turbos used.

With newer turbos, more boost, the seem to do a lot better.

It's all about Peak Cylinder Pressure.
The easiest way to keep Peak Cylinder Pressure safe is to limit boost. You can run higher boost as long as your fuel loading and injection timing are sympathetic to the overall goals. But this requires more understanding than the average owner has.

Average cylinder pressure produces power. Peak Cylinder Pressure determines if anything breaks. Modern engines are able to get more power from lightweight engines because peak cylinder pressures are carefully managed.

Dropping compression is an easy way to lower peak cylinder pressures. But do that on an indirect injection engine and they become hard to start. Direct injection engines start easier and run compression ratios that allow far more boost while keeping peak cylinder pressures safe.
 
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It's a very common misconception that high boost creates high cylinder pressures. In reality boost has very little to do with the peak cylinder pressure. The injection timing is the number one factor in peak cylinder pressures. You can easily drop 20-30% peak cylinder pressure by retarding timing 1-2 degrees but make up for the power lost with more boost and fuel. Both make the same power but using more boost with less timing keeps the peak cylinder pressures down. Not many people talk about or play around with this type of thing and even less can actually measure in cylinder pressures but in the world of high performance diesel drag and pulling applications it's widely used as they need engines to stay together. High boost does not mean high peak cylinder pressures, it's only one very small part of the equation.
 
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So let's hypothetically say cost is no object and I buy a brand new 1hz long-block motor made for a 79 series in a different market straight out of Japan or wherever there's stock. Let's say because I'm keen to experiment (and cost is still no object) I elect to fit an aftermarket turbo kit right off the bat after the new motor has been installed and tested.

What turbo kits are the best ones to match to a 1hz? Here in Oz there are a few places doing aftermarket 1hz turbo kits still.

How does one actually 'tune' a 1hz to run optimally with a turbo kit added when the motor is either new or has no major wear that will affect performance?
 

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