1HD-FT. The Story of an Engine That Wasn't Allowed to Breathe

[Dougal]

That sounds like CT27 - it is also an aftermarket one (ATS racing). I don't remember exactly the type of turbo wheel it has. RAYJON gave me the link earlier in this topic: CT27 Billet Turbo Upgrade - https://atsracing.net/products/ct27-billet-turbo-upgrade. But looking at their photos, they are also using old-fashioned gen.1 wheels. That means that you are talking about some different CT26 upgrade.

This sort of thing: Kinugawa Turbo 3" TD05H-18G-7 Toyota Land Cruiser 1HZ 75 79 80 100 105 - https://store.kinugawaturbosystems.com/products/kinugawa-turbo-3-td05h-18g-7cm-for-toyota-land-cruiser-1hz-75-79-80-100-105

They are showing an STS turbine wheel option that's out of stock, it appears they're mixing up their upgrade wheel option with ceramic BB which IMO is a less reliable option. My memory is fuzzy with TD05/TD06 but I think the shafts were the same but wheel machined OD'd varied. Which means one Gen 3 casting could do all of them.

What are the differences between STS, STS 55, and STS Advanced?

The STS (Superior Turbine Strike) turbine wheel will take a shorter time (a 5-8% decrease) to build boost, achieve higher top-end speeds, and extend the choking area. This is because it has less inertia and restriction compared to an 11 or 12-blade STD turbine, and it also has more flow...

store.kinugawaturbosystems.com

The standard MHI turbines are Gen2, Gen 3 is I think all aftermarket.

 

[VADUS]

Thanks. That one is for a single scroll. For the twinscroll CT26 they have the same 9-bladed STS, for CT20B they don't have anything - just a replacement with a CT26.

 

[Dougal]

I have a Gen 3 built turbo sitting in a box for the last decade. The turbo I use normally is a Gen 2 but I once built a smaller turbo with a Gen 1 paddlewheel on it to see how it would go.

I hit drive pressure at 4x boost. It was terrible. 60psi drive, 15psi boost and completely choked the engine. The Gen 2 can do drive pressure below boost if EGT is high enough (over 600C) and rpm low enough (under 2000rpm).
I have far too many projects that keep getting in the way of this one.

 

[VADUS]

I agree with you regarding poor 1st generation blades. That's why I am trying to find a 2nd gen. wheel, but to no avail. There is only 9-bladed wheel from Mamba for my turbo size. Kinugawa also makes 9-bladed STS wheel for the big CT26 turbo. The only way to simply reduce choking for me now is to make separate waste-gate piping and muffler.

 

[Dougal]

I agree with you regarding poor 1st generation blades. That's why I am trying to find a 2nd gen. wheel, but to no avail. There is only 9-bladed wheel from Mamba for my turbo size. Kinugawa also makes 9-bladed STS wheel for the big CT26 turbo. The only way to simply reduce choking for me now is to make separate waste-gate piping and muffler.

Wastegate mods won't change the operating pressure of the turbo, that's set by the efficiency and incoming energy. A wastegate can only lower boost. If the 9 blade is all that's available for your configuration I would try it.

 

[VADUS]

It seems like you are missing my point. I am talking about separating the two flows after the existing hot housing: from the turbine wheel and from the wastegate valves. I have integrated wastegate valves like most of us, and when they open, additional turbulence occurs behind the turbine wheel, causing increased backpressure and choking. I want to separate these flows and redesign my stainless turbo outlet by welding in a divider between them and making a dedicated exhaust pipe for the wastegate valves.

 

[VADUS]

If the 9 blade is all that's available for your configuration I would try it.

I'm afraid that a 9-bladed wheel will increase turbo lag. That's a lot of expense just to be disappointed. What do you think about porting my existing gen.1 blades? It should slightly reduce back pressure and wheel weight.

 

[Dougal]

It seems like you are missing my point. I am talking about separating the two flows after the existing hot housing: from the turbine wheel and from the wastegate valves. I have integrated wastegate valves like most of us, and when they open, additional turbulence occurs behind the turbine wheel, causing increased backpressure and choking. I want to separate these flows and redesign my stainless turbo outlet by welding in a divider between them and making a dedicated exhaust pipe for the wastegate valves.

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In a high rpm petrol engine with low boost you have a lot of wastegate flow and divorcing it can be significant. In a diesel with higher boost our wastegate flows are minimal, like single digit percentage, and I don't think you'll see any change. If you've got a noisey exhaust you can even hear when it's flowing and how much.

I'm afraid that a 9-bladed wheel will increase turbo lag. That's a lot of expense just to be disappointed. What do you think about porting my existing gen.1 blades? It should slightly reduce back pressure and wheel weight.

They used to clip blades to reduce the exit choke, while it will reduce blockage it will also reduce the effectiveness of the wheel and probably not improve efficiency. Might be good for high rpm but will increase lag. In my opinion the things that matter are wheel size, efficiency and leakage. The more efficient wheels run a bigger trim than the older gen1 wheels because the purpose of a turbine is to expand the gas flow and the bigger the exit the better it can expand the gas while still recovering kinetic energy.

I think the wheel shape and trim are the ultimate limits on how effective the upgrade wheels will be in older turbos. Some you could remachine the turbine housing but I think most would be better to adapt in a better designed turbo.

 

[VADUS]

In a diesel with higher boost our wastegate flows are minimal, like single digit percentage, and I don't think you'll see any change.

My small CT20B with the 60/50 turbine wheel is designed for a 2.0L 4-cyl. gasoline engine that revs about 2 times higher. I agree with you regarding the higher exhaust gas temperatures of a gasoline engine. At the same time, however, I have a 2.1‑times larger 6‑cyl. engine with mechanically controlled, inaccurate fuel delivery, which is an important factor. Even with lower diesel EGT, it produces a large volume of exhaust under maximum load, and this can easily choke both the turbine and the wastegate valves simultaneously. I have a choking problem that starts at around 3000–3200 rpm; it’s not very critical for me, but I want to resolve it by using a divided outlet and separate exhaust paths.

They used to clip blades to reduce the exit choke, while it will reduce blockage it will also reduce the effectiveness of the wheel and probably not improve efficiency.

Thanks for the advice. I came to the same conclusion regarding blade clipping. But I’m going to remove excess metal from the back side of the turbine wheel and the shaft nose without touching the blades — to reduce the moment of inertia and improve response — and polish the back side to reduce parasitic friction against the oil mist in the cartridge. And of course, the brand new billet-type compressor wheel 48/68 (72.7 in extended tips) is already purchased and awaiting installation.

 

[VADUS]

but I think most would be better to adapt in a better designed turbo.

This is too expensive a project, especially taking into account that I've just finished my twin-scroll project two years ago, and I am completely satisfied with my CT20B twin-scroll turbo.