BIG 12HT Build Twin (Compound) Turbo

[Toy12HT]

Where are we up to with the build? Is it on the road yet? I think we could all learn from your findings.

[djroberts]

Pics?? n stuff, whats happening dude? Video maybe??

[BIG12HT]

Hi All, well as it is with most projects that people with families and jobs have, delays delays delays....

Since I don't own the HJ61, I havent been responsible for the work done on it after the rebuild. In any case, the owner, a friend of mine, has installed a water to air intercooler, 3" straight through exhaust and a boost gauge and a pyrometer. I will be doing the final tune hopefully in the next two weeks. I will have to check how well the intercooling system works and the injection timing before tuning the boost/fuel. When I assembled the engine, I just fitted the injection pump to a timing that was "she'll be right mate" location until all was running and will be properly timed up. As things go, it has been driven around for ages now like that. hard to believe it is jagged to be in the right spot but runs well enough. As it is it has been dynoed. I was not there but was told it made 127kw and am not sure if that was corrected flywheel or at wheels. In any case, we should get some good results really soon.

I have just started my own project again, finally. I have a Lexus LX470 which of course is a fully fitted out V8 petrol 100 series. I initially planned to fit a 12HT (I have one still) but due to time contraints decided easier to "plug and play" a 100 series engine/gearbox from a half cut. As a result I have purchased a 2006 43kkm factory turbo diesel (HDJ100R) 5spd auto half cut which should be at my door this weekend. I will be rebuilding the 12HT and selling (after I come to terms with the fact that I will never use it - I really like having the engine there - like keeping the dream alive...) and I will be selling off the v8 engine, gearbox, accessories and computer as a conversion package. So far I have removed the aftermarket extractors (not so easy...), front shaft, tail shaft, radiator, hoses and the wiring harness for the engine is neatly opushed through the firewall and sitting on top of the engine. I was really suprised how neat everything is and the ease of unplugging and unbolting - should be easy to put in another car since everything is part of the main harness! Perfect conversion for petrol 80 series.

This week and hopefully by saturday end the engine and gearbox (separately) will be out. I have an air locker for the front IFS diff, but because the TD has a 4.1 and the petrol has 4.3 diff's, I will swap them over. That will give me factory locker at rear (I have a factory 4.1 locker) and aftermarket locker at front all controlled by a factory 80 series diff lock switch which just happens to neatly fit in the 100 series factory diff lock location - nice! Anyway, before the engine goes in I need to do the diff swap, so hopefully that doesnt take much time. Also I havent ever fitted an air locker to tghe diff itself...maybe that is best left to the pro's...?

A new thread will be started. No photos taken yet because not much to see..... I will give the updates on the 12HT when it is tuned and also put a location for new thread for the 1HD-FTE swap when it is up.

[KiwiBacon]

I'll be interested to see how your swap goes. Does your 1HD-FTE have the varaible vane turbo or the CT26?

You know you want to chip it when you're done, right.

[craz3d]

ffs, this thread is useless without 12ht porn. That's the only reason most people open these threads

[BIG12HT]

Hopefully in 2 weeks I will have something for you.

[BIG12HT]

Hi Dougal, Wow, did some big posts and they dissappeared. I am not sure how long they take to load up. Anyway, to answer again, I am not sure if vnt or not. I am excited to find out but at the same time not sure what I prefer since I hav no idea about the governence of the VNT and feedback to ecu etc.

[BIG12HT]

For those interested, when I took all the measurements of the 12HT block when preparing for my build, at that time my brother who is a diesel mechanic commented on the apparant block thickness, or at least the thickness around the cylinders. As a result, it looked like a 95mm piston might fit. I did some ultrasonic wall thickness measurements and clearance measurements around the crank and thought that perhaps some increase in stroke might be possible. Well, the interestingt bit is that I found and purchased a set of pistons that were 95mm but the compression height was 7mm less than the 12HT piston. Thus the name BIG12HT came about from the idea of boring and stroking the 12HT. In the end I changed my mind to compound turboing which then ended up not happening due to time constraints and now I am at the 1HDFTE.

But, and here is the big but, a very close friend of mine was rebuilding his 12HT and I told him about my idea. After chastising me for not telling him about this earlier I sold him on the idea. As it is now, he has built the engine including a full balance and cryo treating the rods, port matched the heads and cleaned them up, fitted oversize exhaust valves and fitted to a , wait for it, 80 series! Indeed it is a 1990 Jap import VX-Ltd full spec 80 series, factory winch and difflocks like the one I owned and still miss.

As it is at the moment, there are MANY bugs to work out and all the gauges need to be made to work, intercooler to be fitted, aircon hoses setup and regassed, starter motor wiring done, kickdown cable adjustment needs to be sorted and there is somethging funny going on with the injector pump. Plus, many other things. But in the end, we have a running 4.76L 12HT. Actually, what seemed like an easy enough swap in the beginning turned out really really difficult - for him not me ;-) the engine itself was easy though.

That may be of interest also to some and I will report how it all goes. Pump was setup for 90cc. Turbo is a mildly high flowed CT26 (16G comp wheel).

Cheers

[CustomTurbos]

Hi All. I changed my name from BIG12HT to Dieslex because I am doing a diesel conversion in my Lexus and the name allows for any motor change..... The 4.7L 12HT is running but my friend is having troubles with oil pressure.

He took the sump off and changed the 1HDT squirters (twice as big as the 12ht ones) and that improved the pressure. Still very low at idle though, so he must have some other issue. At the moment he is using a test gauge as well so the pressures are accurate. (3psi at idle when at operating temp, 15-20 psi on cruise, 80psi when cold). Anyway, he will solve the problems but this all means power runs and tuning wont be done until the source of the issue is fixed.

Anyway, as promised I started a thread today on the 1HDFTE conversion. Turns out it (JDM 2006) does not have a VNT turbo. Maybe Europe only got them?

[Shadow]

Hi All. I changed my name from BIG12HT to Dieslex because I am doing a diesel conversion in my Lexus and the name allows for any motor change..... The 4.7L 12HT is running but my friend is having troubles with oil pressure.

He took the sump off and changed the 1HDT squirters (twice as big as the 12ht ones) and that improved the pressure. Still very low at idle though, so he must have some other issue. At the moment he is using a test gauge as well so the pressures are accurate. (3psi at idle when at operating temp, 15-20 psi on cruise, 80psi when cold). Anyway, he will solve the problems but this all means power runs and tuning wont be done until the source of the issue is fixed.

Anyway, as promised I started a thread today on the 1HDFTE conversion. Turns out it (JDM 2006) does not have a VNT turbo. Maybe Europe only got them?

sounds like a very common 2h / 12HT problem with the oil pressure relief valve being jammed shut, causing over pressure until it eventually opens. This is exactly what my 2H does.

The oil pressure relief valve is located in the timing case, bottom drivers side. Its a big cap, about 21mm from memory, right behind the PS pump.

[matts_gemmy]

how is this 12ht a 4.7l engine i did the sizes up and the most i can find in the capacity is 4.26L ???????

[hulsty]

Stroker crank!

[matts_gemmy]

a 1 off custom crank i doubt it still 700cc extra fill me me in very interested in the anwser

[80's_delirious]

a 1 off custom crank i doubt it still 700cc extra fill me me in very interested in the anwser

I'm guessing offset machined bigend journals and conrods from something else?

would love to know if this could be done with 1HD-T + bigger valves

[perko88]

video or it never happened, also keen to see a dyno sheet with torque curve

[RED60]

Can we be enlightened on what the 95mm pistons were from and how you got the 4.76l overall..... Hopefully this setup or similar could work on a 2h as well.. they need all the help they can get..

[bj on roids]

Still no pics?

[matts_gemmy]

pics? pics? pics?

[CustomTurbos]

Pics and video....well I will ask my mate if he took any pics - I am sure he did. As for video; until it is making some power (which wont be until we are sure about the oil pressure) what is the point? On the outside it looks like a 12HT. I guess a photo of the block without the head might be worth a look..?

As for stroking, it has 95mm pistons and 112mm stroke.

If I was doing a 2H I would look at TD42 pistons. Not sure on compression height though.... You just need to get a custom head gasket which isnt an issue these days.

There is more metal between the cylinders of a 2H than any other 4wd engine that I have seen. 107mm centre to centre (16mm between the bores except 3-4 which is 20mm)

Cant give away all the secrets. Being DI, it wasnt easy to get a piston to work and even then we (well, my mate on my lathe) had to mildly machine the combustion chamber to suit the injector position. Fortunately the increase in capacity was perfect for the extra metal removed from the piston. All in all an excellent result. The crank was welded up and offset ground for std bearings. The guy who did it has been doing it to gasser drag engines for over 25 years. Never had a failure, but never done a diesel either.....

Patience, patience. You think this has been a long haul for you. My mate just wants to drive his car. At least it doesnt blow a bit of smoke under boost :-)

[matts_gemmy]

i think alot of ppl would b more interested in looking at the compund turbo set up on it and wat u have done to the intake side of if because surely u arnt using the tiny little like 2" inlet anymore with the vacum shut off wat do u use to turn off buy key???

[THE-Burger-Ring]

sounds like a waste of time and money really i am getting same power out of td42.

[KiwiBacon]

sounds like a waste of time and money really i am getting same power out of td42.

If it was just about peak power then we'd all be driving petrols with massive turbos.

[CustomTurbos]

Everyone has their own reasons for doing whatever project they embark on. As always there are pro's and con's for everything. In this instance, the vehicle is auto, so great torque off the bottom is important. Also fuel economy is an issue. If you want fuel econnomy you dont want to look at a TD42 or any other IDI diesel for that matter. My cousins TD42 puts down over 200rwkw with hardly any smoke at only 3000rpm. It has peak power at over 4000rpm so I know what you mean about getting power. But it uses HEAPS of fuel to do it and that doesnt interest me as something I would own - it certainly is interesting to much around with though.

Initially the thread was based on a compound setup on a 12HT. But there is alot of interest in the 12HT so I thought I should mention the stroked setup. We are very dissapointed that there is an oil pressure issue stopping progress but that is the way it goes. I still have the direct bolt on VNT. But I also have a GT37 VNT that I am more interested in trying for now and there is a new thread on that since it is now a 1HD-FTE I am working on.

I would reccomend that someone does a 12HT with compound turbos or just mods the 12HT in general. They are an excellent base engine to use, have great fuel economy and cheap to run long term with the relaible injector pump and long lasting injectors (2-4 times longer than IDI).

I just sold my 2US-FE to put in a 1HD-FTE. If it was all about budget power, I would simply have twin turboed the 2UZ. I am very sure that ~ 450kw for under $4000 would be possible. (1UZ conrods & cams, 2 x turbos from 1JZGTE VVTi, new pistons, eBay intercooler, new injectors and a fuel mixture and ignition interceptor, 15Psi). As Kiwibacon said, it wasnt about the highest power.

[dogbreath_48]

Have you come up with any leads into injector pump modification for the 12h-t? I assume they are limited by plunger (element?) size rather than lifter/supply pump size? (i understand 1hz/1hd-t pumps can benefit from an electric feed pump to complement the inadequate mechanical lift/feed pump?).

Sorry if none of this makes a lot of sense; i'm relatively cluesless on injector pumps at this stage.

-Stu

[matts_gemmy]

also reading on this i cant see anywhere about having your injector pump wound up???

[KiwiBacon]

also reading on this i cant see anywhere about having your injector pump wound up???

A lot of inline pumps have a huge amount of head-room in them from the factory. My Isuzu pump has factory injection volumes of ~71 cc/1000 shots which gives ~100kw and 330Nm. Pumps with 9mm elements deliver over 140cc wound out, 9.5mm elements over 180cc so mine should be good for over 200cc.

[CustomTurbos]

I havent looked at modding the injector pump because they have 9mm elements. Rack position doesnt go over 13mm yet there is 21mm potential movement.

Whether or not the fuel still gets pumped in at the right time and over the correct duration, I got no idea. Might flow mega cc and end up with a Yankee smoker - aint my style.

So in essence, I havent discussed pump mods because its getting the horse before the cart. If there was a researched off the shelf mod, then sure, but get the supporting components happened and then mod fuel delivery as required was the plan.

My mate with the stroked 12HT got 90cc from his pump on the bench. They said they could only manage 13mm rack movement due to the idle circuit or something.... I am sure there is a way around it. These pumps (or at least the 2H pump) can flow 170cc with some governer mods and 8.5mm plungers!

Hope that answers the Q

[CustomTurbos]

Also, regarding lift pumps, they have an internal pump that holds the pressure at ~ 40 psi IIRC. A theory of mine is that the main benefit of a lift pump, if fitted next to tank, it to eliminate air getting into the fuel lines as a result of the vacuum normally caused by the draw from the injector pump feed pump. Air makes for smoke, bad timing, lower power etc. I am sure that I suffered from this with my 1HDT a few years back.

In future, plan to use a lift pump for this very reason.

[matts_gemmy]

can you just take a pic of the engine bay already people want to see the set up of this supose BIG COMPOUND TURBO setup enough with the dribble about it how bout some proof!!!!

[perko88]

Matts_gemmy is right... Did this actually ever happen? Getting less and less convinced By the day... I will be very happy if you post pics and prove us wrong but you are starting to sound like teal slacks