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BIG 12HT Build Twin (Compound) Turbo

Tech Talk for Cruiser owners.

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BIG 12HT Build Twin (Compound) Turbo

Post by BIG12HT »

Am undertaking a rebuild on my 12H-T.

* Head been ported (done)
* Bigger Valves (got)
* Stiffer Spings (got)
* Ported inlet manifold (doing)
* VNT Turbo, direct bolt on!!! (got)
* Second, Compounded Turbo (doing)
* Laminova intercooler (got, need to build box)
* Bigger piston oil squirters (got)
* Cam - not sure yet, maybe standard (?)
* 1mm oversize, steel top ring lands in piston (got)

Would like to do the rods, but $2k and 3 months wait..... I will leave it, plus I believe the pump is good for only 200 flywheel HP and ~ 460nm

Why go to all the trouble above?? Fun and possibly LPG for the extra power above the maxed out fuel pump.

Why VNT? Should do 21psi by 1400rpm, I have an auto, so need it when the torque converter locks up.....

Why compound when a GT2860RS will do over 200rwhp with pretty good spool? Pumping efficiency increases (in theory, and when optimized against the compressor and turbine maps) when more stages are increased, so should eliminate smoke down low where people overfuel to build boost and up top when VE usually is up the creek, reduce EGT's and help with inlet manifold pressure vs exhaust manifold pressure ratio (helps VE). Also, I have a suitable second turbo......and.....as said earlier, for fun!

My Turbo setup will flow 670CFM @ 36psi (@ inlet manifold) reached by 3800rpm so should be able to support around 230 flywheel KW (if someone knows the ration better, please let me know) but I doubt the rods will stand it and the pump won't flow the fuel!
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Post by dumbdunce »

Graeme,

the whole point of a variable nozzle turbo is to eliminate the need for compounding; the VNT is a good idea but a second turbo is just added cost and complexity for little or no gain. the 12H-T doesn't like to rev so aiming for good torque at moderate revs is the right approach. The rods are good for it.

since the inlet manifold on a 12H-T is a plenum style, I don't understand what porting you can actually do?

otherwise good on you, good to see someone breathing life into a 12H-T, it's the best diesel engine toyota ever made.

cheers

Brian
Free air locker to the first 20 callers!
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Post by BIG12HT »

Hi Brian,

I can see your point, but must disagree. Case in point, the current BMW 3L has a single turbo and twin option. Both are 3L motors, both have VNT's turbos and the twin is a compound setup, runs higher boost and has a flatter torque curve, hence more power up top. 165kw vs 215Kw.

All turbos boost are limited by a combination of maximum shaft speed, turbine flow and compressor exducer diameter. My VNT is good at 22psi and can do 30psi but is out of it's efficiency range. Some people might say who cares, use a good intercooler. Well, the intercooler might remove the temps, but an inefficient compressor means it needs more energy to drive it, which means more backpressure for the turbine, which means decreased VE etc etc.

The 12H-T injector pump is set for flat fuel flow delivery to 3500rpm, and still has 95% by 3800rpm before it signs off with the rev cut.

The torque curve does not reflect this and my theory for the loss in torque, other than parasitic loses, is airflow to burn the fuel. I propose to compensate for the VE degradation with revs by proportionally correcting the VE with increasing boost with revs.

I have bell mouthed the inlets of the head and match ported where the plenum bolts to the head.

based on my theory, I will not overstress the rods by huge torque to make big power, rtaher extra power should be gained in the top end through a better torque curve.

I have done airflow calcs and applied some fluid flow theory and the curves outputed match real world measurements. The spreadsheet and graphs look good to me.

As for the 12H-T being strong... I am dissapointed at the strength compared to the 1HD-T. The later being a better designed, better engineered engine, full stop. I have the rods side by side on my bench - The 1HD-T wins.

I do think however the 12H-T may be a slightly more efficient engine with the long rod/stroke ratio and smaller bore diameter. 160mm rods compared to 130mm for 1HD-T (Approx figures). This is the only drawback of the 1H series; in order to make a more compact engine, they went for short rods. This serves to make the rods stronger, but frictional losses from the thrust of the piston on the wall mean less efficiency. Having said that, short rods mean also mean greater rate of change of pressure at the top of the stroke; so it is a case of balance and I don't know which side the balance lies........... My guess is that, with 12H-T's giving often better than 11km/l (ie: 8.5-9L/100km), the frictional losses are more significant that the pressure rate of change.

I Embarked on this project due to pushrod and inline injector pump and direct injection and reputation of motor. Next engine would be likely the 1HT-FTE.

Having said that, if this goes well, I may rebuild the other 12H-T I have with big rods, and fit bigger elements in the injector pump, bigger valves again, optimised cam etc etc.

One thing at a time though; must finish this one first.
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Post by 80's_delirious »

sounds cool, keep us updated, will be interested to hear how this pans out.
I love the concept of compounding boost, the yanks seem to be all over it with their pickups.
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Post by trev1 »

Any good clues about the bigger valves in the heads?? I posted about this a while ago and didn't really get any good ideas about how to go about the job. I realise that I'll have to buy new valves and seats, but which ones, and how big can you go? I'm looking at a 2H also, rather than the 12H-T, if I could get a 12H-T for a more realistic price I'd go that way but I've already got the 2H.
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Post by bj on roids »

PICS OR BAN!
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Post by AZZA'S HJ47 »

i think that with a vnt turbo that you will have a real winner on yor hands as to running two turbos i think that there will be a little bit of a niggel in doing so. I have heard of 12ht's getting around the 150-200kw at the wheels but have never seen any dyno sheets however i believe that it is achiveable if you go about the build in the right way.

like bj said

bj on roids
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Post by hoppy's79 »

Ha mate i'd be keen to see some pictures and the end results for this cause i done a bit of research to do this to my 1hz as i already have a pretty small turbo (tdo5h from MTQ) and was thinking of pluming it into something like a 35/40 Garret ball bearing turbo but still haven't got around to it. my car's gunna be off the road for 6 months or so, so money pending might get around to it
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Post by KiwiBacon »

Subscribing (yes I'm reading the one on IH8MUD too).

A couple of questions.
First one is, is your flywheel heavy enough to use 21psi boost at 1400rpm? I've got 17psi at 1400 rpm in my Isuzu, but it's not usable because the flywheel doesn't have enough inertia to smooth out the torque pulses at that speed.
The cummins 4BT flywheel is roughly twice the weight and inertia of my Isuzu flywheel. I plan to beef my one up but haven't got there yet.

Second one is the fueling.
You've said it runs flat rate fueling up to 3500rpm, but does it really? My Isuzu pump has a "torque plate" which the governer rotates as engine revs change, the height of the top of the torque plate dictates rack movement and fuel delivery.
Point being, the plate is profiled to match the air consumption of the engine and the desired characteristics (i.e. taper off the top end to make the drive change up).
A flat fueling rate would overfuel at idle and high rpm while not maximising torque in the midrange.

Does your pump have a similar setup?
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Post by Dzltec »

Interesting read, compounds are the way to go, have had them on a 1hdt and now a td42 for 3 years now.

Matching turbos is the critical thing, then supplying enough fuel for that extra air. Once done it will be an animal. The reason you have a toque decline is that power will be on a flat plateau once max fuel is reached. To get a falt torque curve you need power to be on a continual rise, something not possible in a mechanical fuel pump.

The 12ht uses a torque cam to some degree, not as intricate as an Isuzu, but similar. Study up on how an r801 governor works.

You might be doing a little too much theory in design. As far as I knew there are no vnt turbos to suit a 4 litre engine. You are either using too small or to big a turbo for the first unit. How are you controlling the vnt. It is usually done via a duty cycled vacuum valve, using boost and air mass to determine what it should be.

Even so, get it on the road, get it dynoed and post up the results. good luck, you will never go back to a single turbo after this.



Andy
www.diesel-tec.com.au Ph 03 9739 5031
Ball bearing turbo upgrades for factory turbo vehicles. Got a diesel question just ask.
Home of the twin turbo shorty and many 150rwkw+ patrols.
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Post by KiwiBacon »

Dzltec wrote:The reason you have a toque decline is that power will be on a flat plateau once max fuel is reached. To get a falt torque curve you need power to be on a continual rise, something not possible in a mechanical fuel pump.
Hi Andy

Is there something in an inline pump which prevents it from delivering it's maximum volume per stroke as rpms rise? Other than the torque plate or similar device which can be modified?

It seems to me that if a plunger can deliver say 100cc/1000 shots then it should be able to do so up to it's safe rpm limit. The volume injected is what determines torque (and the air to burn it cleanly of course).

Here's an Isuzu with a very flat torque curve, it's mechanical injection but has some electronic interference. It shows what is possible. The power only dips when the governer cuts in.
http://www.isuzu.co.nz/Engines/4he1_T.htm
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Post by Dzltec »

It will be the design on cam plate. If you have 100cc@1000revs, you will want 120@1500, 140@2000 etc to keep power rising. That is the hard part, almost like a rising rate regulator.


Andy
www.diesel-tec.com.au Ph 03 9739 5031
Ball bearing turbo upgrades for factory turbo vehicles. Got a diesel question just ask.
Home of the twin turbo shorty and many 150rwkw+ patrols.
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Post by KiwiBacon »

Dzltec wrote:It will be the design on cam plate. If you have 100cc@1000revs, you will want 120@1500, 140@2000 etc to keep power rising. That is the hard part, almost like a rising rate regulator.


Andy
No, the fuel delivery is per stroke, so the total volume is already increasing with rpm.
100mm^3 at 1500rpm is 50% more fuel than 100mm^3 at 1000rpm.

Delivery per stroke sets your torque. Torque x rpm sets your power.

A flat torque curve (i.e. constant fuel delivery per stroke) gives the linear increase in power.
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Post by BIG12HT »

Hi Andy, I have met you and you showed me your twin turbo GQ and the holed TD42 block, and the 138kw 1HDT twin turbo 40psi dyno curve and 175kw 55psi TD42 twin turbo non intercooled dyno curve....before it said enough. You then dynoed my 80 series (Wife, Kids and I were on a trip around Australia at the time - red and silver 80) and it made ~ 108 rwkw @ 2 wheels = I had made 114kw @ 4 wheels, in Perth but lots of smoke and turbine backpressure....

Anyway, Kiwibacon makes a point that is per my understanding, so if you could enlighten me I would be appreciated.

I understand (from the manual) that at the fuel measurement is "delivered" fuel per stroke, that is, the torque curve should be fairly flat other than "losses" aka: friction, less than optimum burn characteristics etc.

My theory is then based on this understanding, that by at least artificially compensating for the falling VE with revs, at least the burn characteristics may be accounted for.

I have seen in a paper from VW on their TDI, that max efficiency is at 1700rpm and the efficiency decreases by 20% by the time peak power is reached. This is about the same level (%) that torque has also decreased - thus fuel has stayed constant, but torque has dropped off.

As for controlling the VNT, that will be a matter of experimentation because I do not know how much "back force" I will see from the VNT blades. I guess what I am trying to say is that as the turbine backpressure increases, more force is required to keep them in a lower A/R configuration.

The specs on the turbine are basically the GT25/28 but the compressor is a 60mm 50 trim (42.5mm inducer). The trim allows for 22psi by 1400rpm, I expect the turbine control will allow this. The small trim is perfect for compound turbo ....however after more reading and too much thinking, I think a 62 trim 52mm exducer compressor is a better option - less peak flow, but higher efficiency where it counts. These larger trim compressors have worse surge characteristics but man are they efficient !!! My smaller trim is slightly less efficient (ie: the 80% area is smaller) however it is also easier to work with (wider map and wont surge where I am running it).

I chose this turbine because my cousin Zac in Perth has this turbine on his Patrol and makes 202rwhp - I put him on to you and you did his pump - nice work, it hammers! His will not make the low end boost I want though without surge.

By the way, I would like to drive the difference between the twin and single with no fuel change and observe smoke/drivability etc.

I was increadibly lucky to find a GTVNT that bolts on to my stock manifold. I cant tell you exactly what it is off - because I don't know! I will be bolting my stock manifold upside down and sticking the high flowed turbo underneath.

I plan to use the biggest A/R exhaust housing I have and and keep back cutting the second turbo turbine until it needs no wastegate!

Andy, how many CC fuel required per cyl at 200 pump turns to make 600nm?? This is direct injection BTW, so ~ 10% less than TD42 600nm. Std it is set for 11.3-12.5cc but It can do easily 18cc.
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Post by BIG12HT »

Also, the turbo has a 5mm shaft where the compressor bolts on; I am concerned about ripping it off with the extra torque requirement!
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Post by BIG12HT »

Trev1 - I have no experience with the 2H or the 1HZ. I have read as I am sure you have that out of all the precom diesels (Mitz aside), they are about the worst for cracking.

You may or may not know that in the peak torque area, where they are mostly used, the precom engines use more than 10% extra fuel. This ALL goes as extra heat into the cylinder head. That is alot of extra heat to deal with.

Providing you are not looking for peak economy, if you put steam bleeds above the exahust area or around the precoms then you might solve the reliability aspect of the turbo 2H engines. Intercooling is a must.

Other than that, apparantly 2H rods are less stout than 12H-T and the 12H-T does not have piston cooling. Though, having said that, the pistons of the precom engines do not get as hot at the directs anyway, since the combustion chamber of the direct engine is in the piston itself, and the surface area of the piston is higher - so both equal hotter pistons in direct.

regarding GT3540, I assume of a XR6T. nice turbo. TD05 also a nice turbo. high flow with a small wheel 16G and should be a nice combo. I would do something about cooling for the precoms though and intercool it. Your pump will not flow std the fuel you want - send it to dzltec (Andy) and I think he can do up to 240 flywheel kw????


And for the others comments I WILL POST PICS, very busy in all manner of things at the moment, but will get to it.
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Post by BIG12HT »

IN THE LAST POST, I MEANT TO SAY 2H DOES NOT HAVE PISTON COOLING, OF COURSE, 12H-T DOES
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Post by -Nemesis- »

AZZA'S HJ47 wrote:i think that with a vnt turbo that you will have a real winner on yor hands as to running two turbos i think that there will be a little bit of a niggel in doing so. I have heard of 12ht's getting around the 150-200kw at the wheels but have never seen any dyno sheets however i believe that it is achiveable if you go about the build in the right way.

What sort of torque numbers would that yield out of curiosity? Obviously that's a pretty tame figure compared to cheaper petrol options, so there must be a Mt Vesuvias torque curve yeah?
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Post by BIG12HT »

AZZA, even 150rwkw is a huge number. After playing with my 1HD-T, I have an appreciation on just how hard it is. I had figured that using a 600cfm compressor wheel and 21psi I would have had an easy 150wkw. Real world results proved different!

Trying to get bottom end torque while also getting top end power contradicts turbocharger theory; and it gets worse when you use 2 valve heads direct injection because the swirl port is not a good flowing design (unlike say a TD42).

On top of this, the DI engines are more efficient at low rev (1400-2500rpm) and the poor flowing heads flow OK at these revs but badly up top. This actually serves to excacerbate the problem and is largely the reason that the ID engines feel more "revy" than the DI engines - common rail excluded - noting that common rail and 4 valve heads mostly go hand in hand.

The pump AND turbo that Andy @ Diesel-Tec supplied my cousin Zac's (not sure on his outer limits name) Nissan TD42 makes that a revy torquey machine. It hammers. 151rwkw in fact with flywheel estimated 580nm. After being in this car, it gives me an idea just how far away I was with my 1HD-T! Best of all it drives stock like in behaviour.
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Post by BIG12HT »

I should also mention that when I said 36psi = 230kw, this is also highly theoretical and probably not likely! If I get 150rwkw and no smoke except off idle with 600nm @ flywheel before 1600rpm, I will consider the project a roaring success

Also, I just have to hear the 2 stage turbo - never heard it before!!
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Post by BIG12HT »

If anyone can help with suggestion of parts for bigger elements in the injector pumps, that would be great. Pump numbers are as follows:

OK, the numbers listed on the pumps are:

AUTOMATIC:

17
ND-PES6A90B312RND147
093000-1471
7H0101

MANUAL:

20
ND-PES6A90B312RND190
093000-1900
6F0002


Hope that helps!
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Post by BIG12HT »

OK guys, some photos for you to chew on. Included are some porting pre/post photos and the primary VNT turbo.

Cheers!


OK, I can't work out how to insert photos - what a noob! I have posted on the IH8Mud site though
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Post by bj on roids »

Mate link us to Ih8mud site?

Email me the pics and I can post them.

Or just try and use photobucket!

cheers
Rob
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Post by BIG12HT »

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Post by ledgend80 »

so where are you up to with this build
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Post by BIG12HT »

the build will be completed in the next two weeks and the turbo installed will be a high flowed CT26....I sold it to a Mate and he wants to go conservative.

Will have some interesting times though over the next month with TD42. Already made 201hp @ rear wheels..... hopefully now 250-300hp!

Many secrets, but will share the actual results when they happen
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Post by drifter** * »

have you been doing a build thread on any other sites?

how much power can a 12ht crank handle, one of my mates broke a crank on the weekend.
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Post by bj on roids »

I broke a crank in a 2H I dont think they are all that strong.
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Post by BIG12HT »

We are aiming for 150-180 @ wheels.

Worked till midnight last night, looking preddy. Need to torque up Head/BE/Mains, fit numerous accessories.

As for crank strength = no idea. They dont look too strong really, after looking at a 1HDT. So what were the circumstances around these broken cranks?

But 110cc is the max the pump can flow (apparantly) which isnt huge. That number looks about right too. Expecting to only get 90cc without internal adjustments on pump, so 460-540nm and ~ 140-170kw @ Flywheel. Nice smoke free efficient power.

All theory though until all the bits are running. Hopefully soon, though he still has to do the exhaust and mount the intercooler..... (not to mention the engine).[/img]
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Post by pinkfloyddsotm »

awesome dude, post a vid too!
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