Friday, May 10, 2013 at 19:09
I am taking it that you have a 12h-t.
I was not aware you could put a sleeve inside a 12h-t
bore. Never heard of that before, but that's not to say it's not done. These engines usually last a very long time - 500,000km plus and then only need a small rebore and new Alfin pistons with a steel ring land insert. There is a design problem with the original 12h-t pistons in that the top ring tends to bash a groove in the top ring guide and eventually bits break off and bounce around on top of the piston, causing all sorts of nastiness.
This generally starts to be evident at 300,000km and can be fixed by renewing pistons at that time and a light honing. Then drive another 600,000km without problems.
Is it possible you have not been given the correct information. For example, you were told it was a 12HDT - never heard of that one before.
Regarding strength of the engine. There is no problem. I could explain all this in detail as to why there is no problem, but at the end of the day, you're either going to believe me or not. I guess I need to explain myself a little:
Potential problems with high boost.
Head Gasket:
There is a LOT of clearance between the pistons, water and oil galleries on a 12H-t. I have been running 19 to 20 psi boost for a couple of years with not a problem. The thing is that it is not at that boost for very long unless you are towing a very heavy load up a very long
hill. With the GTurbo and other mods I have made, I never run out of power unless the load is exceptional. I'm talking overtaking roadtrains at 120kmh towing a 1.5t camper up a
hill. The thing that kills these diesels is heat, not high boost. You control the heat and before any mods you MUST install a pyrometer or EGT gauge, Exhaust Gas Temperature pre the turbo so you get a reasonable measurement of the temperatures inside the combustion chamber. If you exceed 750°C for too long, that is bad. Comfortable levels are below 600°C.
With the G Turbo, given it's capacity to flow vast amounts of air and burn all the fuel my IP can pump in, I rarely exceed 450°C, and under the passing road train conditions described above it might get to 600°C.
Anyway, boost and therefore the heat you produce, is controlled by your right foot.
The second aspect of high boost people worry about is the bottom end. The 12h-t has oil squirters onto the bottom of the pistons to keep them cool. I have never known of any problems with a standard 12h-t and the bottom end, no matter what boost.
So - there is no problem with high boost and a 12h-t. By high boost I mean in the vicinity of 20psi. Creeping up to 25psi and 30psi increases the realms of risk and is not something I am prepared to do. Others might and find no problems. I suggest you will need significant IP modifications in order to give you enough fuel to justify those levels of air flow. I have unscrewed my IP fuel screw to its maximum and find 19psi a happy setting. Besides, by boost gauge only goes to 15psi!!
Moving onto your question "How is high powered 3rd party turbo for
rock crawling? Does it ever get unstable?"
Unstable?? Not sure what you mean. It's not going to fall off.
Rock crawling typically requires very low speed, both on the ground and for the engine. You don't load the engine up very much with low gearing and low speed, so the turbo won't boost very much. Turbo's come into their own on the highway, towing, sand dunes and general acceleration around town. Low speed along beaches were the engine is loaded up dragging the car through sand is also nice to have more power. But not for
rock crawling. If you're talking about building a vehicle for off road competition
rock crawling, then you're on the wrong
forum and need to go to IH8MUD or Outer Limits and get the high tech expertise that is pretty thin on this site.
When looking for a turbo, another option is a cheap version from China via ebay. Some people have found these to be useful for them, and they might be okay. I have also heard of poor fitting control and bits of swarfing and other
debris left inside the internals which was only going to cause problems.
If you read the thread at the IH8MUD
forum I gave in my first reply to your question, you will find that what people appreciate about the GTurbo over the other options is that it is a direct bolt up replacement for your standard turbo, and to the outside observer it remains looking standard. What Graeme has been able to achieve however, is boost that comes on much lower than other options and maintains stable boost all the way to the maximum revs for each engine it is designed for.
By fitting a smaller turbine housing, on the exhaust side, it is possible for any turbo to give you boost at lower revs and increase drivability with more low down power. But then the challenge is to maintain that efficiency through the rev range and this is where smaller turbines by themselves come unstuck as a solution. Hence manufacturers built variable vane turbos that provide a good solution across the rev range. But a 12h-t cannot be fitted with a VV turbo without special modifications.
What Graeme has done is designed both the turbine and compressor to match the engine in a much better way than the standard turbo, and from what others across the world are saying, better than any of the other aftermarket options. And he continues to develop these turbos so they provide greater efficiency. One component of efficiency is to ensure the compressor wheel is designed to still 'grip' the air at high speed and boost. Poor design just creates poor air flow, extra heat and limited air flow.
So, sure, you can buy a turbo from Garrett, KKK and Holset but it really needs to be properly matched to your engine, both the exhaust and the compressor side. You will be spending a lot of money whichever way you go, unless it's an ebay version from China which used to be around $400 last time I looked.
Boost on a 12h-t standard is 7psi. They are lame at that setting, absolutely lame.
Mine has been dynoed to measure 50% increase in torque and at at least 200 rpm lower than standard. It's been like this for a couple of years and I expect it will continue for many more to come. The EGT are remaining remarkably cool, indicating low load on the engine, the oil stays remarkably clean, indicating highly efficient burning, I get good fuel economy, enjoys heaps of power and it's all thoroughly enjoyable. Especially when I take on friends on hills, or drive around them on the road - all by a little wheel pumping a bit of air!!!
I trust this adds clarity for you.
Tim
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