This is quite a thread.
From my experience, and what is obvious from the comp map, the GT2860RS is prone to surge if you try and get two things accomplished at the same time -strong torque, like 550nm for example as a reasonable amount to chase, and boost low end boost say from 1600rpm. It just doesnt work if you want to get more than about 16psi from 1600 and even then you need to overfuel it to get there. The reason for the overfuel is that at 0.64, it is actually a little big and the reason for the surge is the huge trim on the comp wheel (which also gives it a very efficient midrange). Trouble is, it is a 4wd, not a car, and it WILL be heavily loaded up dragging down through the revs. Due to a fair amount of hysteresis in the aneroid circuit, surge may not be experienced always as the revs rise up during acceleration (but Ive seen it on the GT2860RS, particularly when the aneroid was almost eliminated to try and get a strong bottom end - only 115cc on this pump too), but put it in some beach sand and let it sink down through the rpms below 2000rpm (not unreasonable) while on boost and if your ~17psi or more it will surge like a bztd. And then the first class (for some applications), but puny, bearings will fail in a shorter time than any owner will want, like maybe 5000km's if loaded up regularly.
To Northside, and with all due respect, you made a comment that "you have tried almost every imaginable combination of turbos" but the comment was directed at Garretts offerings. That is hardly conclusive evidence that there is not a better option out there in traditional wastegated fashion. If we isolate a common requirement, I would say that most people would find it very useful to have 550-600nm at the crank and be able to get that from 1600-1800 at the highest rpm. 2000rpm is just too late (in my opinion) to really get the benefit from a diesel engine. On this basis, isolating this case, I think there are better offerings than what Garrett has in the GT28 size. I use in the example GT28 because in theory it is the closest to suit the requirement (Gt25 too small, GT30 too big) and this has been proven in practice.
So what do I think is wrong with the Garrett offerings. Two things, the housing A/R is slightly too big, and the comp wheels are either too big in flow for the best turbine match (71/0.48) or the flow is great but the trim is too big for low end and high PR (60/0.62). Do they work - yes they are all close enough to work, but they are not optimised. They are an off the shelf solution that has not been engineered for the application and as a result, it is an additional compromise to the myriad of compromises engineers already have to make.
So what do I think is better. Depending on the exact setup, the TD05H is one of the best options. It is available in a wider range of ex housings, has a more robust CHRA, is available with a wider range of better suited compressor wheel and cover combos to the point that it is good on everything from 120rwkw to 180rwkw in a road going trim (one might crack 200)- you can push them a bit harder/richer for a spirited off road fun truck, but thats not my bag - I'm allergic to too much smoke.
Another option for those with the CT26 flange is a correctly modified CT26. They have a robust CHRA except std they dont run a 360 degree bearing and they dont have a superback comp wheel. All of these things can be changed (I change them) and then they are similar in this respect to the TD05H. I have one on a 12HT that isnt intercooled but is making an easy 430nm at crank without smoke at only 1600rpm with 16psi (and 100rwkw, which I realise isnt a huge number, it wasnt the point, but its very clean at 18 psi and has been tested to 26psi at 3500rpm) - a GT2860RS, the only GT28XX close, is not able to do anywhere near 16psi at 1600rpm with the same fuel load. But, I've done alot of research on turbine mods, different housings to use, high flow covers with compressor wheels of other turbos (including the TD05/06) to get to this point.
Now that my advertisement is over on CT26 options (I only do Toyota Turbos and the Garrett vnts, not Mits turbos), the point here is that there are better options out there. Up to say 15psi, the GT2860RS is a good turbo above 1900-2100rpm, but it doesnt have a well matched turbine housing for a 4.2 Diesel in the low end (say, ~ 0.55 which would be a far better option and something similar in spec is available in other turbo offerings as mentioned) and it cant if its in a performance application because the tighter housing will only serve to exacerbate the surge issue in the low end. But there are TD05H options that can be matched as good as you could hope and for a reasonable price. Plus, they are far cheaper to rebuild.
Cheers
Northside 4x4 wrote:Enlighten me on your thoughts as to the Junk worthyness of the 2860 please?
Ive seen 1 fail in all the countless upgrades I have done personally and not heard of many other failures in normal operation...
Been using them for around 5 Years + now with oh, id say probably 300+ Kits being sold in that time, Ive never had to warrant 1 of them.
Saying they wont last because they 'want to run more boost' is a bit of a vague statement. Of course if you run them outside of normal operating conditions they may fail. Would people complain if they brought a tyre rated to carry 100kg and it pops when they have 2 ton resting on it?
Just FYI, I dont tinker with them in my spare time. I do it for a living and I do it ofter with a good chunk of time and money going into testing of various items for these and alot of other diesel cars.
So link me some of the dyno graphs of all these wiz bang turbo's out there that kill the 2860's please.
Cheers
. I hope your injector pump fuels in the 3000rpm to 5500rpm range with a ramp up and 180cc+. Not unrealsitic for the VE pump.
just to late i guess however it never got full boast until 2200rpm. Mate of mine has GU ute with HX35 fitted by 1500rpm he has over 8pound which is better than my current setup.
