12H-T performance Build

[gbentink]

Dougal, I must agree and yet dive into the unknown for the sake of not being able to leave good enough alone

And yes....a CT26 for 650cfm. I hope for 600 actually. The factory compressor covers are very large compared with the TD05 20G covers. These are an under rated Turbo. Turbine wise they are bigger than TD05, so I think I am in the right zone. If not, will buy a TD06 genuine 20G.

My smaller turbo is VNT, the bigger turbo has a wastegate.

As for reduced exhaust temps, yep, this is a case of applying the little I know and hoping for what I don't.................

 

[gbentink]

I would like to call it an educated guess............but I think that would be stretching it!

 

[Dougal]

Dougal, I must agree and yet dive into the unknown for the sake of not being able to leave good enough alone

We need more people who'll try anything and document every step of it.
We've already got plenty of people who try something new and don't give enough information for those who follow (or decide not to follow).

So 600cfm is about 44lb/min. What equates roughly to 450hp worth of air on a petrol engine.
I know a guy with a reported 280rwkw on a supra, but he was using two CT26's.

What do you know about the CT20B? Is the entire CT20 and CT26 range based on the same core?

 

[gbentink]

regarding the CT20B, this is a difficult one because nobody seems to have the info.

Toyota brought out a revised range of the bigger CT series around 1996. These had larger inducers and smaller turbine exducers. I was fortunate enough to own a Toyota JZX100 Chaser Tourer V which had a single turbo VVTi 1JZ in it. 377nm @ 2400rpm and 206kw @ 6000rpm !! What an engine, amazing fuel economy also (10.5l/100km around town, auto, 1480kg Sedan)! Anyway, I looked at the inlet and exhaust but didnt remove the covers. (I *think* the 1HD-FTE also runs one of these Turbos. They run out of puff up top though).

I believe it to be what is commonly called a CT20B. Slightly smaller turbine exducer (like around 46-48mm) and the inducer was larger than the Supra CT26, around 47.7mm (I believe that to be the exact number).

All CT26 state that on the compressor cover, but these just say Toyota, that it.

I have a sneaking suspicion that the exducer on the compressor wheel was reduced to around 60mm from the std CT26 65mm, but I do not know for sure

But to answer your initial question, no, dont think cores are the same, and I think the shaft length is shorter in the CT20B than the CT26 by quite a margin, but run the same bearings and thrust washer etc.

They are also Ceramic turbines. This is a good thing in a diesel - my CT26 in the 1HDT was a Ceramic shaft, only because I wanted to prove a theory I had that the "18psi destruction point" everyone talked about in their Supras for blowing the ceramic turbines out the exhaust was predominantly high EGT and or backpressure and or overspeed issue. Well, after 32000km in a year towing a caravan pushing up to 27psi (once to 30psi) and no problems at all. So, I was either correct or I had a rare wheel - I think I was correct The mods I did was fit a Mitsubishi 18G compressor wheel which has a 68mm exducer and having a 49.2mm inlet, the higher choke flow and larger diameter should keep the shaft speed in check.

Great turbo, boosted like none other factory fitted to any 1H (except 1HD-FTE), but rear housing too small for top end power and the bigger supra housing was too big for the auto. I NEVER experienced compressor surge either. And, the turbo with 270 degree thrust bearing did OK!! I thought it would not destruct because I have an auto, so thrust is not so much an issue.

I have already back cut my turbine to "half way" copy my garrett. Just need to send of the turbo to get the cover and 20G compressor wheel machined up and all balanced. I will do final assembly.

Hopefully the whole process isnt too drawn out...........

By the way, I figure using a wastegate must be more inefficient than backcutting the turbine, fitting an appropriate housing and not using one........

 

[gbentink]

280rwkw with 2 x CT26, man boost must have come really late .............

 

[gbentink]

Dougal, I reread your post.

CT20 has shorter turbine shaft, cores are smaller. Same bearings, thrust etc though as CT26

 

[Dougal]

Thanks for the info on the CT20B. I know an MR2 owner who's looking for one.

Wastegates losing efficiency, that's a given. But only while it's open at max boost. The other 99.8% of the time when the wastegate is closed you're not losing anything through it.

I just did a lot more work on the intermediate intercooling and after plotting about 30 different data points I've got a simple equation to relate final intercooling to two stage intercooling.

All these numbers are ratios (0-1) for effectiveness.
Total intercooling = Final intercooling + (1-final intercooling)x0.62xintermediate intercooling.

So to get final boost temps equivalent to a 60% effective single intercooler, you can use a final intercooler of 50% and an intermediate cooler of 32%.
Using two 60% effective coolers is the equivalent of using one 75% effective cooler.
Using two 50% coolers is equivalent to one 66% cooler.

My brain hurts.

 

[gbentink]

Thanks for that. It does simplify things, and now my brain hurts less!

I believe that the exhaust turbine potential for the *big* turbo is the unknown and most likely the most restrictive component. That being the case, intercooling of the *big* turbo is of prime importance since less turbine backpressure would be required to drive the compressor for a fixed mass flow the better the intercooling is.

It is also for this reason that I do not want to operate the *big* turbo at a PR greater than 2.3 - try to keep it in the most efficient area on the compressor map.

On my 1HDT, in the end I disconnected the wastegate actuator boost hose completely such that I remained shut at all times. I then reduced the turns on the main fuel screw to limit boost to ~ 22psi. In the end, all things considered it was perfect. Very little smoke, and wastegate not even needed!

Boost was suprisingly consistent throughout the rev range, but I had more than 120rwhp at 2000rpm @ <1150F EGT, so I seldom reved it up.

By the way, there are quite a few >300rwhp 7m-gte supras with stock CT-26……the modded CT-26 do quite a bit more, but some go stupid and put 60-1 compressor wheels on it, poor ol CT26 turbine wouldn’t know what to do with a 60-1!!

 

[gbentink]

If I was your friend, I would seriously consider a TD04 with 19T wheel rather than CT20B.

CT20B is a nice turbo, but costs too much for what it is in my opinion.

This is a nice compressor wheel that I might upgrade my GT2560v to. It would make it a GT2558 but bigger trim, awesome surge line yet can flow > 500cfm

 

[Dougal]

If I was your friend, I would seriously consider a TD04 with 19T wheel rather than CT20B.

CT20B is a nice turbo, but costs too much for what it is in my opinion.

This is a nice compressor wheel that I might upgrade my GT2560v to. It would make it a GT2558 but bigger trim, awesome surge line yet can flow > 500cfm

I suggested garrett, but the sole reason for finding a CT20B is it'll bolt right up to everything he already has. Manifold and dump pipe.

One of the most fun cars I've driven lately was an old fiat with a small T3 turbo. Boost started at 2000rpm, starts whistling at 2500rpm.
Just great midrange punch that works really well in a touring car.

 

[gbentink]

Wasnt an X-19 by any chance?? I have always fancied either a 1973 or therabouts 124 or a X-19, FIAT made classy interiors and had great engineering - I am not sure where they went wrong as regards to oil leaks and rust though..... For the 124, there are some great engine swaps - like the Lancia Delta Integrale engine..... Years ago I almost bought an immaculate 1987 1500cc X-19 Bertone. It was LHD though and over here the cars must be RHD. The idea, even 12 years ago, was to turbo charge it.

I may be fitting the 12H-T to an 80 Series. I may have mentioned that already, it is subject to passing regulatory tests and I am in the middle of getting an answer from the authorities as to what that is. Having said that, my HJ61V is looking very pretty; new carpet arrived yesterday and I have been cleaning the other interior parts which come up near new look. I was very fortunate to get the last of the 60 series and it has the gray trim; which is very nice. It has travelled 200kmiles, so middle of the road kms.

To make everything fairly easy, a friend suggested I fit up the twin turbo setup to the 60 and then on to the 80 (or the new motor anyway, whichever vehicle it ends up residing in) after it is sorted. This is a good idea!

 

[Dougal]

This was a 124, always fancied a lancia delta too.

There's a turbo bible called "Turbocharging the Internal Combustion Engine" by Watson and Janota. It's long since out of print and at least one of the authors has died. But I think an internet search turned up a copy at a library in Perth.
Any chance you've read it or could get a look and see what the content is like?
Secondhand copies seem to fetch up to $US500.

There's another book by Bain which is supposed to be almost as good, but I cannot find any copies for sale.

I don't have access to a dyno, but I do have a large manmade viaduct which I happen to know the slope exactly. With a few sums I think my 4BD1T with 20psi boost can put 75kw to the ground at 2000rpm and 80km/h.
I still haven't fitted an intercooler so EGT's continue to climb, it's not a sustainable state of tune.

 

[gbentink]

An intercooler made ALL the difference to me. Chnaging the compressor and raising the boost made an improvement in the top end, though the bigger turbo was acceptable down low, clearly the turbo made easier boost with std compressor.

An intercooler on yours, with 20psi!!! will may a monstrous difference. 75kw @ 2000rpm already is very impressive - is that a 3 litre engine or 3.9 litre?, surely you will get around what I was getting which I would expect - both 2 valve heads, both DI, similar boost and similar capacity.

How do you think the engine VE changes with rpm? Do you expect around 90% at the 1500rpm marke dropping to 65% at near near the 3500rpm mark?

I tried to back calc the cfm data calced against the boost they give for the VW Tdi 1.9 and it appears to me the VE goes from a best of 74% down low to a worst of 68% up high - this is rather different to what I had thought.......

*IDEA* - Perhaps the cam timing is such that it closes the inlet valve quite late after BDC sacrificing low end VE but helping top end VE...........

 

[gbentink]

What turbo are you using at the moment, trim etc, VNT??

 

[gbentink]

I got my static timing advanced to the maximum but still within std spec, I definately lost exhaust energy down low for turbo boost and I received a measurable increase in fuel economy.

My 1HDT 80 Series rig @ 4900kg (I took it over a digital weigh bridge), huge amount of stuff on the roofrack, 33" tyres, 3" lift, 17'6" poptop caravan in tow (included in the weight), 15.6L/100km at 1800rpm, 90km/h with cruise control - that is the average for 2400km

This seemed quite good compared to others I questioned regarding economy - and I asked alot of people.

 

[Dougal]

Like you I bought an airflow meter some years ago with the intention of measuring VE. But it's just another project I never got around to. I'm of the opinion that the VE curve will closely follow the factory torque curve (they set the fuel curve to match the available air) but I'd like to prove it to myself.

My engine is 3.9 litres, the turbo is a T25 from a nissan CA18DET. As I've mentioned earlier I'm a big fan of small turbos. 0.49 turbine A/R, 0.48 compressor A/R, wheel is 51.3mm and 60 trim. At 20psi it's running off the map.
This engine spends it's entire life between 1500 and 2500rpm and I'm quite pleased with most of it. I need a bigger flywheel so I can use all the lowend boost I have. It's fine under acceleration but hill climbing in 5th gear below 1800rpm it rumbles with torsional vibration.

I have in the parts bin a large air/water intercooler (already have the pluming, pump and radiator fitted from a previous attempt), GT2256V, two T28's (one 0.64 turbine and 0.42 compressor from a skyline and one 0.86 turbine and 0.6 compressor) from a silvia.
Both need rebuild kits.

Just found Baines book on Amazon, so I bought a copy. Will be interesting reading I hope.

 

[gbentink]

Interesting regarding torsional vibration.... I look forwrad to hearing the results of the bigger flywheel

I have noticed that bigger trim compressors are significantly more efficient in the middle of their range than smaller trim, so smallest turbo with biggest trim is also my idea of the optimum turbo.

Interesting to hear about the Bains book and the other you mentioned - I will look them up. How much did you end up getting the Baines book for?

GT2256V should work nicely on your engine; maybe good as the smaller one for compounding?? Hw heavy of a flywheel do you need for 650nm??

 

[Tapage]

Good chat ..

just only one time that I ran 20 PSI on my 1HD-T with the factory CT26 but plenty of more fuel added .. was scared running the CT26 over " specs " and not sure it my engine can handle that boost ..

 

[gbentink]

1HD-T came out by yanmar with over 650nm and 190kw, 30psi boost. The 4 valve using the same rods has over 700nm.

Std conrods, 15.5 compression pistons. Some pistons had bronze inserts in them, others do not.

Diesels are generally overbuilt, the totally standard naturally aspirated TD42 Nissan motor (IDI) with 22:1 compression has often been bosted to 30psi. Just today I was discussing this motor with united Injection here in Perth, they have had one recently to 200rwkw - you read correctly. Head hasnt been off block, totally stock, but interccoled, 12mm plunger VE pump, high flowed turbo. They race this thing in a detuned state at 550nm and 158rwkw. I have watched it race (2 weekends ago) and it doesnt smoke much, but really hauls!

I also met with Andy and Diesel tech in Melbourne. He has done a compound turbo 1HDT and also a TD42. The TD42 had a GT2860RS for the small turbo and a GT30R (I think) for the big one. The 1HDT used the stock small turbo and the GT30R for the big one.

As for numbers;

1HD-T; 40psi boost, no intercooler, no smoke, 138rwkw, std pump, no problems but Wife needed car back
TD42; 55psi boost, no intercooler, no smoke, 177rwkw, modded pump and a conrod out the side of the block............

Having seen inside a 1HDT, I would feel comfortable running 50psi

I think I am taking a risk with the 12H-T

besides, we shouldnt be talking boost, it is the size of the bang that breaks the rods......

Now, a compound turboed 1HD-FT with fully modded pump - that would be fantastic!!!

 

[gbentink]

Dougal, I enquired about the book. A local library was supposed to have had it - in my shire, however the state library has it, so I will try and get it.