[gbentink]

Had a drive in Tims HJ61, goes really well.

He has since made further mods and skids around crorners apparantly.........what out for a Grey HJ61 at the Police Auctions soon - Anti Hoon legislation you know........

Have got mine running, goes really well too. Wish I had a 3" exhaust like Tim's :-(

See my turbine mods..... Havent sacrificed much down low, but should go very well in top end with the right exhaust. I think my exhaust is skinnier than the turbine outlet

[Tapage]

Huge .. !

from which poit to you go in your exhaust AR setup ?

[gbentink]

Hi Tapage, sorry, I did not understand the question.

[Tapage]

Originally Posted by gbentink

Hi Tapage, sorry, I did not understand the question.

sorry was no clear ..

which was the stock exhaust AR and now which it's the actual AR ...

[Tim-HJ61]

Performance comparison on one hill in an otherwise fairly flat city that I live in.

Before
Standard exhaust
12.5psi boost
Standard fuel setting
At 80kmh at bottom of hill in 4th gear, full power on.
At top of hill I'm really looking to change into 3rd


After
3" exhaust
14.5psi boost
Three turns out of the magic fuel screw
80kmh at bottom of hill in 5th gear, power on.
At top of hill I am still in 5th gear, still holding 80kmh
EGT getting high.

I predict that if I had gone up there in 4th gear I would have been able to accelerate up the hill, boost would have been higher and EGT lower.

Conclusion.
Impressive torque increase.
No noticeable increase in fuel consumption.
Not yet locked up with anti hoon laws Graeme ..... it's an advantage being twice the age of the police force.

T

[CruisinFJ60]

it seems odd to me that 14 psi is all that is really safe for these...

my 01 cummins factory boost to just under 20psi and with current mods im boosting to 45psi on all stock internals w/o a care in the world. at 50 psi i need to think about head studs to keep from lifting the head but they can handle up around 65 psi on stock headgasket and internals as long as you can keep the head from lifting (i.e. head studs)

[BjarniThor]

Hello Tim

Interesting routing of the exhaust. Could you post more pictures underneth how the exhaust goes at the back of the truck at the rear axle? It is a good idea to be able to save the space inside the frame rails in front of the rear axle (where the exhaust is normally) for e.g an extra fuel tank.

Another possible benefit of this confuguration is at the engine downpipe, for trucks who are equiped with a gear driwen winch, the driveshaft to the winch does not probably allow this much increase in pipe diameter unless the pipe is routed directly outside the frame as in this confuguration ?

I have a HJ61 with 12HT engine in Iceland. The engine is compleatly stock. The discussions in this forum for a power increase are interesting. For my choice, if modifing the engine I would like to have as much torqe avalable as early in the powerband as possible. What would be the list of mods and adjustments to increase (safely in terms of EGT etc.) to increase tourqe form idle to say ~1800-2000 RPM? Can the govenor max zero load speed be adjusted down from its original setting of 4200 RPM? I newer use more than 3000-3500 RPM on this engine.

Finally, for an optimum exhaust diameter for this engine in a tuned form, do you think there is noticable difference between 2 1/2" or 3"?. 3" sounds like much, is it nessecary in thems of flow restrictions ?

Cheers,

Bjarni

[Tim-HJ61]

Hi Bjarni,

My 19 yo son loved his week or so in your country earlier this year. He did 27 countries in through Europe in 7 months, with a jealous father back home in Western Australia :-)

You've asked very sensible questions.

My discussion on boosting power output of my 12H-t is at another forum Power boost.

At the rear the exhaust ducks back inside the chassis rail and follows it's normal route over the axle then exits at the normal point.

Yes, this configuration is excellent to allow larger exhaust when a vehicle is fitted with a PTO shaft. I don't know why they didn't do this from standard.

It also opens up the area inside the chassis rail for an additional long range tank. I currently have a 70l tank there and expect I could add an extra 40l at least if I was to extend that tank.

3" or 76mm is regarded as optimum for these engines. Don't have any evidence to prove that, just that's what we all believe - you know how it is, myths and legends, where do they start, but 76mm certainly made a significant difference. I doubt the cost would be a great deal different over a smaller pipe. Go the full size first go. My exhaust fitter agreed 76mm is the optimal size.

Bjarni, asking intelligent questions such as changing the power characteristics of the 12h-t will only lead one way. Once you do it, you will smile more. Arm yourself with two 10mm spanners, a 3mm allen key, then go forth and get stuck into it!! Oh, best to instal an EGT pyro first to keep an eye on things.

GBentink has let me know there is a way of adjusting the fuel to give less fuel at the high end and more at the bottom. I have unwound my main fuel screw three turns now and can indeed say that my engine pulls now to 3500rpm and beyond I guess too, but I can control how far it goes by my right foot. I mostly change at 3000rpm as you do and don't like revving it out hard too often.

I have increased the overall fuel supply by unwinding the fuel screw at the front of the governor. There is a similar adjuster at the rear of the aneroid/governor which controls the extra fuel added under boost. I 'think' this is the screw that modifies the balance of the top end, low end fuel supply. gbentink is a better authority on this, but he has been busy doing 18 second 1/4 mile drags in his auto. 18 second 1/4 mile

In any event, the low end power has increased adequately too. More would be nice, but it is quite okay now. Above 2000rpm (full boost @ 15psi) it really lights up and pulls very strongly all the way to wherever I want it to. Acceleration from 80kmh to 110kmh is terrific.

Good luck with it all Bjarni, and stop asking sensible questions or I'll get gbentink onto you and he'll have you doing four wheel burnouts in no time at all :-)

Tim

[crushers]

some good info located in this thread.
14 lbs is no problem for these beasts.
2 1/2"-3" exhaust works well.
EGTs tell the fuel settings that should be used.

i would LOVE to go for a ride someyear.

[gbentink]

Check out Youtube YouTube - 12HT 1/4 Mile HJ61 18.04 seconds

This is std exhaust, extra fuel and 20psi (at a guess)

[crushers]

18.04 is slow.
sorry, just my opinon.

[CruisinFJ60]

Originally Posted by crushers

18.04 is slow.
sorry, just my opinon.

My dodge runs a mid to high 13....
and thats still to slow.

[crushers]

my point is that if he is actually running 20 lbs of boost (which is a guess without a boost gauge) then he should be in the high 13s to low 14s...
those engines pull like a locomotive.

[gbentink]

It is MUCH quicker than standard. The engines are great but "they pull like a locomotive" is not a measured statement.

Not trying to break any records here, just mucking around and getting started.

20lbs boost will not give you a 13-14 sec 1/4 mile! It weighs 5300lbs with drive, passenger and fuel!. Also, no intercooler and a VERY restrictive exhaust AND minimal smoke.

The 12HT std is only 130hp, put that in a online calculator with the weight and tell me what it does.

My previous car did 14.0, that felt fast and had 230kw and weighed 3500lbs with Driver!!

The big Cummins is a greater engine, but seriously, 1/4 Mile of 13.? seconds is quick in a Truck driven every day.

Bet you dont use ~ 10l/100km like the 12HT typically does!

[gbentink]

Stock, the 12H-T is 130hp @ Flywheel, 90hp @ wheels. Use 90hp @ wheels for online calc of std 1/4 mile times and 5300lbs

Mine did 0-64mph in 12.5 secs (Getting close to a stock 100 Series Turbo) when upping fuel and boost. Around the 120hp @ wheels currently

[BjarniThor]

Yep, I have always liked so much the 12HT engine design. 6cyl inline, long stroke (relatively bore 91 mm stroke 102 mm),factory turbo, direct injection, gear driven cam, piston oil cooler jets, inline fuel pump (engine oil lubricated, stronger than rotary type fuel lubricated).

Exactly how a heawy duty truck diesel engine should be designed. Given this, it is probably good to make some more power than the original setup in the Landcruiser. But in terms of operating this engine in the long future, I really hope that there will not be problems in general for parts supply ? What do you guys think about that? It was only available in LC for a couple of years, does some other trucks or equipment use this engine? ( Toyota coaster buses I think ?)

Tim, right now I am busy with some rust repairs on my truck, yes things rust here in this climate, not as good as it is in sunny Australia! I might start some mods of the engine if this ever gets finished.

Regarding your exhaust, I was concerned where exacly the pipe ducts back into the standart routing. It must be in front of the rear axle spring support? ( If you understand) For the 2 1/2"
3" debate, well 3" certanly has a higher cool factor. Anyway, good, my exhaust needs replacing soon so I might build a new one based on this configuration.

cheers

Bjarni

[crushers]

okay, lets compare... since you are getting defensive of my statement.
i had a 97 HZJ75 on 35s that was turbo'd with a mapped turbo .64 A/R set at 14 lbs max, i had the fuel cranked up and i had 3 CFM of propane being injected. my best time (using the timer on the dash clock) was 13.5 seconds from dead stop to 100 k/h BY THE SPEEDO. tht works out to 120 k/h using the tire fatio calculator of 20% difference.
now, your tank shoudl be getting much better acceleration than that with "20 lbs of boost" so either you need to increase your fuel to match the air being shoved down it's throat or you are generating too much heat from the compression (compression = heated air) or you need to use the throttle heavier.

no, pulls like a locomotive" is not a measured statement but then neither is "20 lbs boost - at a guess".

i have driven a number of 12HTs over the years both auto and manual and they pull hard but they have a low rpm max which means quicker shifts and lower top end.

[crushers]

this is the only real reason i do not recommend the 12HT (H series) or the 13BT (all B series) as a swap engine. it would suck to spend huge money installing a dated motor and find out in a coupel years it has to sit becasue a part is non-existent...

Originally Posted by BjarniThor

But in terms of operating this engine in the long future, I really hope that there will not be problems in general for parts supply ? What do you guys think about that? It was only available in LC for a couple of years, does some other trucks or equipment use this engine? Bjarni

[gbentink]

Not defensive, just trying for a bit of persepctive on not only the results, but also the intent of the excercise.

31" tyres (std) to 35" Tyres is 12.9% by the way, not 20%.

I would fully expect a 1HZ with LPG and 14psi to be quicker than my HJ61 in its current form. No suprises there. Going to 20psi from 14psi is only a 16.8% increase in air IF the turbo operates at the same efficiency at 20psi than at 14psi.

Clearly it doesnt, because when left wide open, it only gets to about 20psi and stops (hits efficiency wall). I would expect 10% at best extra in going from 14 to 20psi in my setup when considering decreased compressor efficiency and increased backpressure.

A boost controller will be fitted this week and I plan to set to around 17-18psi or whatever gives the best results of power vs smoke until hardware changes are made.

The whole point of the excercise was to get a baseline to work from. It is good and well to say "mine went so much better after I did xyz" but it doesnt actually give anyone a measured idea on the results of the mods and so is not help at all to anyone wanting to mod their vehicle.

Further, for those with std 12HT setups (especially auto), they can measure their own performance against mine and see what is possible without making any hardware changes to their vehicle. perhaps they have the same or better performance than mine - entirely possible. Tims my be quicker, auto aside, it probably should be.

Now, if I change the exhaust I will be able to measure the effect.

I measure 122hp @ wheels using a G-Tech, which is about what I expected (120-130). 90hp is std for a 12HT manual, so it definately made a difference. Also consider than my vehcile weighed 2410kg at the time of the tests (subject to weighbridge confirmation)

No question that with less back pressure (good size exhaust), not running into choke flow on the compressor and using an intercooler, should be an easy 150- 160hp @ wheels at the same boost. I would expect time to drop to low 17 sec 1/4 mile and mid 11 secs to 100km/h.

[gbentink]

Parts are easy to get at the moment, and cheap!. Seals and gaskets mostly the same as the 2H.

If pistons ever get to be a problem, there are options there too.

Given that the engine I just rebuilt solved a factory problem and that the engine is 20 years old, in another 20 years I probably wouldnt be interested in a 12HT when it does die, and I very likely wont own it.

It will be a problem at some time, but at least 10 years away I would have thought

There are other considerations for getting a different motor than the 12HT, like engine noise. They are fairly noisey compared with the newer diesels. May be a consideration for some people.

[crushers]

this si your sand box, no need for me to rain on it.

cheers and best of luck in your build.

<BTW stock tires on MOST land cruisers including 61s were 29" tall, the 81 were the first to get 31s stock from the factory>

bye now.

[Tim-HJ61]

Originally Posted by BjarniThor

Interesting routing of the exhaust. Could you post more pictures underneth how the exhaust goes at the back of the truck at the rear axle? It is a good idea to be able to save the space inside the frame rails in front of the rear axle (where the exhaust is normally) for e.g an extra fuel tank.

Bjarn,

I found myself under the cruiser today changing the oil and remembered your request.

I also measured up the extra space created by removing the exhaust from inside the chassis rails. The only tape I could find was an old imperial one, and I can't easily do conversions from imperial to metric volume. So I download an App on the iPhone, did the calculations, and came up with 57 litres. This is all whilst I was lying under the car. Pretty cool I thought!

This 57 litres is in ADDITION to the existing 70 litre auxiliary tank already fitted, and will do nicely as a diesel tank to use as start up fuel for my vege cruiser.

Room for extra tank where muffler used to be. Also shows the pipe coming in in front of the rear tyre.



Ducking inside the chassis rail again in front of the left rear tyre.


Looking forward - Just made for it.


There is also a small website of the same mod at this link

All the best

Tim

[BjarniThor]

Thanks Tim for those photos. They show exactly what I was wondering about. Took also a look at your travel photos in the link posted earlier. Man, makes my want to go and explore the land down under.

Bjarni

[Tim-HJ61]

Originally Posted by BjarniThor

Thanks Tim for those photos. They show exactly what I was wondering about. Took also a look at your travel photos in the link posted earlier. Man, makes my want to go and explore the land down under.

Bjarni

There's more :-)

Pleased the photos are useful.

Tim

[gbentink]

Originally Posted by CruisinFJ60

it seems odd to me that 14 psi is all that is really safe for these...

my 01 cummins factory boost to just under 20psi and with current mods im boosting to 45psi on all stock internals w/o a care in the world. at 50 psi i need to think about head studs to keep from lifting the head but they can handle up around 65 psi on stock headgasket and internals as long as you can keep the head from lifting (i.e. head studs)

I was wondering if you fitted the second turbo yourself? Do you still use the stock turbo and use a bigger second?

The Cummins 6BT is as strong as. The rods are MUCH bigger than the 12HT. I would hope the 12HT could manage 40psi.... 13 seconds is an awesome time, I would need over 350rwhp to get that in a HJ61...... Does yours remain smoke free under boost? How about the torque delivery? Did the the second turbo make your powerband wider or narrower? Turbo sizing, what AR did you use on the exhaust side? Sorry for the many questions, but this is a very intersting topic for me. I have athread on the development of a 12HT and hope to install a twin turbo setup.

[GM60]

A very interesting thread, and it has me thinking of trying to get a bit more out of my stock 12HT.
First though I'd like a bit of advice on the different fuel adjustment screw locations on the 12HT pump.
The reason is that my 12HT blows some black smoke when I take off, after the engine has been idling in slow traffic for a couple of minutes.
I can see it in the mirror and it is quite noticable, and doesn't impress whoever is drivind behind me, and it just looks bad.
There is also a bit of black smoke at idle when the motor is first started and cold.
The smoke is noticable as I accelerate in first gear after a couple of minutes of slow running/idling, and is sooty black.
It just gives one burst of black just as I take off and then it stops and does not blow any noticable smoke during normal driving.
Could this mean that the off boost adjustment has been turned up a bit too far at some stage?
If so, where is the adjustment screw for the off boost fuel?
I don't have a FSM for this motor and am unsure which screw does what.
What do you guys reckon. Do you think the black smoke is due to an over adjustment which can be re-adjusted, or could it be something else?
The injectors were done about 15,000 k's ago so they should be ok, and the engine is in pretty good condition.
You guys seem to be pretty switched on with the 12HT.
Any help on this would be great, then maybe I'll do a big exhaust etc.

Cheers

[Tim-HJ61]

Further up in the postings is my link to another forum posting I made about increasing the fuel supply with photos of THE screw. www.perth4x4.net/ 12H-T power boost

Re your black smoke, I was going to suggest your injectors need checking, but if they have been done not so long ago then maybe not. Did this black smoke always occur since you have had your injectors done? The big puff of black smoke is how they all are and it is because they are direct injection. the pump dumps a bunch of fuel in there on start up to make it go. Can't change that one. Call it character. Think of it as a badge of honour having a direct injection 12H-T

There is a second adjustment at the back of the governor housing that 'AS I Understand" adjusts the off boost fuel. I think it's tucked away in a really hard place to get to for a very good reason - it's not something to mess with!

I wouldn't worry too much about a bit of black smoke after idling for a while, especially if it goes away at normal running speeds. AFAIK most diesels will do this after prolonged idling.

What you need to do is to wind out that fuel screw so you get black smoke all the time

Hope that helps - apart from the last bit!

Tim

[GM60]

The time that I notice it the most is when the air con is running and after some slow running. As soon as it gets going, the smoke is not noticable , and I don't think it does it much if at all when the A/C is turned off.
Yeah, you definately have me thinking of cranking up the fuel a bit for some better power and torque, as well as getting the boost a bit higher and maybe fitting a 3" exhaust.
The only thing stopping me at the moment, is that I don't have either a boost gauge or a pyro, so I guess I'll have to fork out for those before doing any changes.
Thanks for the good advice and for all the information you have put into this thread!
Cheers
Al

[Tim-HJ61]

There is a possible issue of the piston cooling down at idle and not burning the fuel properly. Pulling out the throttle a little so it idles fast at 1000rpm might stop the smoke if you are going to leave it sitting idling for a while. I'd not fuss about it.

T