[Tim-HJ61]

Hello,

I've had a 3" exhaust installed on my HJ61 to help the 12H-T breathe a bit better. The results: impressive.

I can pull up long hills a whole lot better and hang onto the higher gears longer. In short, it gives more torque and makes for a more enjoyable drive.

The standard dump pipe on the 12H-T is a good flow design and does not need replacing if the new exhaust is following the same route as standard.







The new exhaust exits through a hole cut in the guard, and down to the rear on the outside of the chassis rail but inside the line of the body. It then ducks back inside the chassis rail at the rear wheel and follows the regular route with a resonator at the outlet.

I did this to give me more room for extra tanks inside the chassis rails.
Although the existing dump pipe is okay, leaving it in place would have led to too tight fit against the chassis, so the new exhaust was built onto a flange on the turbo.







I'd recommend this mod to anyone wanting more torque. It is also an important step in unleashing the power of these engines with extra boost and fuel - neither have much point with standard exhaust.

Tim

[Tapage]

any chance to get a video .. ? and pictures of your rig ..

[Tim-HJ61]

Hi Tapage,

This link will take you to my latest journey through Western Australia.



Click on this link to see a Movie of start up smoke and exhaust note

There is also a posting I made at my local off road forum on increasing power in a 12H-T

and my gauges mounted in the overhead unit. Gauges are vege oil temp, vege oil pressure, Turbo boost, EGT.


and I put some H1 HID inserts into the high beam, centre, lights. Outer light is still high/low beam. Inner light is HID only and switched separately as if they were spotlights. i.e. only coming on when high beam is on, AND their own switch is on. I power each of the 12v HID ballast separately from each battery via a 24v relay switched as I have described.



I'm looking for some locking diffs, and I could be talked into an intercooler if it would fit behind the grill and not be too difficult to fit.

Tim

[plumma]

did you dyno the engine before and after the exhaust mod without playing with the fuel ande boost? the reason i ask is on my hj 61 i dropped the exhaust just before the big standard muffler at the three bolt flange (so it only had the engine pipe attached to the turbo) and dyno ran it than hooked up original exhaust and re-dynoed and results were it lost torque and a single horsepower (1 bhp) with the 'exhaust dropped' although i hadn't played with boost or fuel. just a point of interest what boost is your engine running and what effects does it have, economy,power, reliability ect as i'm thinking of upping both fuel and boost but wondering what was the best compromise for the 12ht was with reliability economy and driveability being paramount. i don't want to destroy a great engine in search of max power or be unable to afford to keep fuel up to it

[Tim-HJ61]

Hi Plumma,

Always the big question isn't it!

Have a look at this link in the forum by my mate Graeme who has led me astray with the mods I have done to my IP.

No, I didn't get any baseline readings on the motor before making changes. Free and easy access to a dyno with readout would be a nice thing to have.

Standard boost is 7psi and I've been running 12.5psi for a year or so. It all went fine and all I needed to do was watch EGT's when towing.

When I added the big exhaust I immediately noticed more torque. I drove from Perth to Geraldton, 450km, and could hold gears on the long slow hills on the highway much more than I could before. I used to lose speed if I couldn't maintain 2000rpm and full boost going up a hill, power would drop off quickly once it went. After the new exhaust this wasn't the case and the increased torque was quite obvious. The big exhaust is essential I believe in enabling excess gas to escape quicker. I found EGT's are less with the big exhaust, perhaps 100°C at full power.

In Geraldton I unwound the fuel screw first one, then two full turns. Boost was left at 12.5psi. Power increase was immediately noticeable and the fully loaded car zipped up hills. I really had to keep an eye on EGT as with all that extra capacity for fuel, EGT rose if overfuelled.

Once I got back to Perth, I did my other tests with removing the waste gate control and found EGT's did not rise as much with the extra air supplied by the turbo. Power was, umm, substantial!!!

I've pulled back to 15psi boost and don't get to that very often. I mostly don't rev past 3000rpm as there is plenty of torque and max boost from 1800rpm to 3000rpm and well beyond.

Am I risking my engine? Maybe a little, probably not so much. There is plenty of reports around that 14 - 16 psi is fine for these engines. Extra fuel is always controllable by your right foot. High EGT's are the nasty thing to avoid that will melt stuff, load up your coolant and oil systems.

Yota put a light on the dash that switches on at 14psi, called the overboost light. I figure that Toyota say 14 psi is enough for them, so why not increase boost to that level? I've also got a posting at this link on power boosting, showing how I did it.

Tim

[plumma]

sounds the goods but would have been nice to know how much of an increase was gained, what is the fuel bill like, is yours a manual or auto. i have an 86 manual with 35 bfg and my brother has a 87 auto with 33 and mine has about 150 k more kilometers on the clock at over 450 k. saying that he is unable to keep up as mine has more grunt up hiils or on the flat and both engines seem to be stock ,factory boost ect similar weight ect but would always like a little more poke

[blis]

Originally Posted by plumma

sounds the goods but would have been nice to know how much of an increase was gained, what is the fuel bill like, is yours a manual or auto. i have an 86 manual with 35 bfg and my brother has a 87 auto with 33 and mine has about 150 k more kilometers on the clock at over 450 k. saying that he is unable to keep up as mine has more grunt up hiils or on the flat and both engines seem to be stock ,factory boost ect similar weight ect but would always like a little more poke

Ive seen upto 170hp by just tweaking fuel and boost in 12ht... 200hp and beyond with modifications, Most limiting factor seems to be the clutch...

[plumma]

well don't keep me in suspense, details, photos. 170hp 12ht i want one :w rench:

[Hendrik]

Originally Posted by plumma

well don't keep me in suspense, details, photos. 170hp 12ht i want one :w rench:

Check this link: G Bentink 12HT Performance Build

[plumma]

"12ht performance build" promises alot but doesn't really deliver. hopefully that will change and we'll see some results because it does have some interesting points

[Hendrik]

Originally Posted by Tim-HJ61

...and my gauges mounted in the overhead unit. Gauges are vege oil temp, vege oil pressure, Turbo boost, EGT.

Forgive my ignorance, but that overhead console looks original - I have not seen one like that before. I have an 86 HJ61 Sahara but it does not the overhead console.

Originally Posted by Tim-HJ61

.......I'm looking for some locking diffs...Tim

Cable lockers, auto-lockers, or ARB selectable ?? Just curious as I am looking at 2 x lockers myself.

[blis]

Originally Posted by plumma

well don't keep me in suspense, details, photos. 170hp 12ht i want one :w rench:

heres one dynograph, standard boost and air to water intercooler...

http://img171.imageshack.us/img171/4...nokppyrnv0.jpg

[Tim-HJ61]

Originally Posted by Hendrik

Forgive my ignorance, but that overhead console looks original - I have not seen one like that before. I have an 86 HJ61 Sahara but it does not the overhead console.

Jap import. Used to have indoor and outdoor temp gauge and an altimeter and I squeezed in the four gauges.

Tim

[Tim-HJ61]

Originally Posted by Hendrik

Cable lockers, auto-lockers, or ARB selectable ?? Just curious as I am looking at 2 x lockers myself.

Torsen / Truetrac would be nice. Not air lockers. Click click lockrights would be fine. Standard LSD wears clutches too easily and is running like an open diff.

T

[Tapage]

Tim great fitment of gauges on the overhead console .. I have it too .. but seems to be complicated toute the vacc line of the boost gauge up there .. ?

[Tim-HJ61]

Originally Posted by Tapage

Tim great fitment of gauges on the overhead console .. I have it too .. but seems to be complicated toute the vacc line of the boost gauge up there .. ?

Persistence, good luck, and an endoscope all helped. I used small nylon airline that was easy to poke through up the passenger side of the door frame. All the wiring was then strapped on and dragged through. The gauges cost me a fortune (A$550 I think) so I wanted them to look cool.

There was no space for the proper brackets in the console, so they are glued into place. This is now a problem as I want to replace one of them, the vege oil pressure, for one with a lower range. I suspect I will use the one in the console for engine oil pressure and mount a new vege oil pressure gauge on the dash somewhere.

I would have preferred to angle them better so they were looking at me as the driver, but again lack of space meant I had no room to tilt them.

Tim

[cbpsray]

I have a 12h-t 24v sahara 1988 turbo. I am trying to find somewhere to get an alternator for it. Toyota say it can be 30amp 0r 40amp. My auto electrician says he cann't see a number.
Any idears where I can get one.

cbpsary

[gbentink]

Hi Plumma, yours has 0.84 final drive, your brothers has 0.716 final drive. Allowing for 35" vs 33" you still have a 10% shorter diff ratio which equals 10% more wheel torque at any given speed. Manuals also have a larger exhaust hiousing on the turbo which brings boost later, but will make more torque once revs get past ~ 2200rpm. I'll bet he beats you on fuel economy on long runs. Would like feedback on that.

Cheers,

[gbentink]

Well I can't argue that there has been no deliveries yet, BUT, the engine has been sold to a friend of mine and I will report on its progress. I have decided to do a stroker version of the 12HT, so I sold it.

The engine shown in the twin turbo thread will be intercooled, run max 18psi using a modded CT26 and a big exhaust. I will tune it on the pyro. It will be fitted to a manual, not auto as mine was to be. If funds allow, maybe he will go the twin turbo route. Unlike myself who likes to tinker, he does actually need the car daily so it isnt a practicle R&D vehicle.....

I fully expect some serious performance from this motor and will be sure to get Tim a drive of it once it has been run in and tuned up.

Dyno graphs are misleading. I looked at the graph posted with great interest, BUT if you dont know what smoke it was billowing or what EGT's it was running or if it was corrected flywheel or actual wheel power there is just too much to interpret to get something meaningful.... 161rwhp T such low boost would equal high EGT's and smoke. Tim has his set up nicely, I just wish he would install an intercooler ;-)

[plumma]

g'day gbentink, i'm assuming when you talk about final drives you are talking about the difference in ratios in the transfer cases ( one being an auto and the other manual ) as i'm pretty sure the ratios in the diff 4:11 are the same. As on the subject of economy, i believe mine gets slightly better economy (manual) against my brothers (auto). we have done a few trips side by side over about 500km one way and on the highway mine (manual) was getting about 10.5 litres per 100 which really ***** him as mine uses less fuel and has more power. win win for me and his doesn't seem to blow any more smoke than mine. if you could tell me the difference between a manual and an auto injector pump would be much appreciated thanks plumma

[gbentink]

Hi Plumma,

There is only a difference with respect to the governer characteristics that are change fueling to suit the auto. Should not reflect in a power difference.

I am interested to hear what you say on fuel economy. I was referring to final drive of gearbox (or is the OD in the transfer case??) anyway, for the manual it is 0.84, for the auto it is 0.716. Diffs in Australia were (I believe) all 4.11. Some Jap spec and US Spec received 3.73 in their manuals.

10.5L/100km is excellent economy, about the best I have heard. Not everyone gets this economy. It could be that your engine is well loosened up, your injector pump timing may be advanced more and your injector spray pattern may be better. Mostly these are the issues. Even things like thermostat temp. If the engine runs hotter, there is more potential for work. This is however a small variable.

I have heard many reports from people with very high km 12HT's reporting excellent economy - even with injectors that need to be replaced. This could be an issue too. As the injectors wear, their cracking pressure decreases and this has the effect of advancing the timing. Up to a point, advancing the timing a few degrees can help considerably with economy, at the expense of some noise increase. On my 540kkm engien, the cracking pressure was only 180 bar. Std they are set to 210 Bar, so this is a considerable drop in pressure. How this reflects in timing change exactly (degrees advance per % drop in pressure), I do not know.

When rebuilding my current 12HT in the HJ61 (which I started for the first time yesterday), the bores were well worn at the turn around point; very common problem in the 12HT. I used a snapon parrallel hone to bore out the cylinders until the lip had dissappeared. This put the pistons and the rings out of "new" spec tolerance. In fact, out of spec completely on pistons, but in spec on the rings (0.7mm gap. For rebuild 0.2-0.45mm, for worn engine up to 1.2mm). In any case, I filed back a set of oversize rings to 0.4mm gap and got a piston, heated it to ~ 180 degress and tried it in a well lubricated bore for a fit. Well, it "only just" slid in. Very nice fit and wouldn’t want it any tighter. The aluminium/silicon alloy pistons have a much greater coefficient of expansion that cast iron and will be at a temperature higher than the water cooled block. A friend of mine knows of people that build their new engines this way - heating the pistons, checking hot clearance etc with quite impressive results.

In essence, what I am saying is that it may be (I am hoping) that my engine with looser piston to bore clearance but better sealing rings, *may* do the 10.5L/100km if I advance the timing a few degrees. I will share all the measurements with folks. It is an interesting experiment. I am in the quest for great economy and this is a major reason for wanting to keep revs as low as possible on the cruise. Typically a diesel is most efficient at full load and 1700-1800rpm. Note that HJ61 manual does about 2550rpm @ 110km/h with std 31" tyres, so I am very (happily) surprised to hear such excellent economy from the manual when doing these sorts of revs.

By the way, visible smoke turned out to be not such a great yardstick for fuel economy as I had initially thought - it seems to be reasonable to think so, but there are many other factors governing fuel economy.

[gbentink]

Blis, I have done some back calculations.

Firstly, 0.67 Bar (10psi) is not stock, stock is around 5.5-7psi.

Second, peak torque at flywheel appears to be 400nm and peak torque at peak power (4200rpm!) is 320nm. The later is an excellent torque figure. The former is correct for an intercooled 12HT with 10psi boost.

So, intercooled, 3" exhaust and 10psi on an excellent engine according to my spreadsheet could possibly do the power quoted, nice to see the dyno sheet. I would be interested in EGT's and smoke though.

It would sure be a fun vehicle to drive - very revy!

[plumma]

my hj61 runs 35's and it actually gets better fuel economy on a trip when it's loaded with my camping gear rather than empty and mine does just over 2100 rpm at 100kph, the reason i ask about injector pumps is my brothers ( the auto ) seems to only rev to 3500 rpm even when you hold it in gear and mine will happily rev to about 4100rpm. I'm not sure if it was designed like that or his has some other issues, either way i think the manual is superior.

[Tim-HJ61]

Originally Posted by plumma

my hj61 runs 35's and it actually gets better fuel economy on a trip when it's loaded with my camping gear rather than empty and mine does just over 2100 rpm at 100kph, the reason i ask about injector pumps is my brothers ( the auto ) seems to only rev to 3500 rpm even when you hold it in gear and mine will happily rev to about 4100rpm. I'm not sure if it was designed like that or his has some other issues, either way i think the manual is superior.

Those tall tyres will be making a good difference, unless you've got 3.7 diffs installed. I used to run at 2450rpm @ 100kmh on 31x10.5x15's and now run 265/75/16 which are a bit taller and subsequently lowered revs to about 2300@100kmh approx.

I suspect your IP has been adjusted a little. Before I played with my fuel screw, my manual used to run out of puff towards yellow line of 3500rpm, but now I have unscrewed it two turns, it still has heaps of go at that speed and would probably run to 4000rpm if I let it - or let gbentink drive without me in the car

I'm not looking for high revs - I don't rev more than 3000rpm on most gearchanges and in my mind a good setup would allow the fuel supply to taper off at higher revs to reduce high EGT's at full power/high revs - but also supply more fuel lower down to build up turbo pressure early. I can max boost (15psi) at 1800rpm now, but there is not much grunt between 1000rpm and 1500rpm. gbentink has described how this is possible to adjust inside the governor at the back of the IP and one day I might venture in there with an allen key.

There might be another turn of the fuel screw coming up too!



Tim

[gbentink]

Hi Plumma, if you mean the manual pump, then it is basically identical, so not possible to say one is better than the other. As for Manual over Auto box, fair enough.

As for the rpm issue, most definately his is NOT tuned correctly.

Easy to fix.

On the left hand side of the pump there is a screw (large bolt, at least 14mm, possibly 17mm). That is the governer rpm setting. I cant remember which way does what, but it should be set to deliver ~ 4200rpm when not in gear, foot to the floor.

Your pump has probably had someone optimise it. Standard the 12HT is not so inspiring, but a good engine. if you hold it flat in neutral, what does it rev too? That will tell you alot.

Std, fuel cut starts gently in the 3500-3800 range. Given that torque drops with revs anyway, stock it should be athsmatic over 3500-3800rpm. Given yours revs to 4200 in gear, it has been played with.

There are so many adjustments on these pumps that you can set them to rev like a petrol with a fairly flat torque curve or have mountainous torque down low and rev to 3000rpm max! So, having a crap setup is easy to believe!

Given that yours runs 35's and I assume you cruise at 100km/h (?) that explains alot. Is that with a roof rack and is yours the high roof? 2100rpm is a good rpm for that motor (obviously given your figures). I want to run 35's purely to drop the revs. The looks are good too! Your Brothers with 33's should be sitting on 1870rpm while you are at 2070.

Does your engine have a stronger diesel knock at idle? If so, maybe your injector pump has been advanced a few degrees. This is a great way to get better economy.

In a nutshell, there are quite a few things that can be done. Given your brothers has taller gear by about 10% allowing for tyres, he would benefit from increasing boost from factory 7psi to 10psi, increasing fuel slightly also 10psi is no stretch even with std exhaust - I would set for ~ 12psi. Not to mention advancing the timing. More boost and fuel means more torque = less gear changes. Since they (autos) lock up at ~ 72km/h std, it is really costly fuel economy wise if doing less than that. Further, given the tall gearing of the auto, coming to a hill means most likely changing gears and unlocking of the TC (bad economy here). If your Brother gets the auto valve body modified by Wholesale Automatics (~$800) it will lock up also in 3rd. With the other mods he should be able to equal your economy, possibly better it. I just remembered that a friend of mine (450kkm manual) does BETTER than 10L/100km. It is HE that has bought the motor in my Performance 12HT thread. That motor has some serious issues too, blows some smoke, runs a little off beat, but economical as!

[gbentink]

Hi Tim - Hey, I started my 12HT yesterday!! If you want to hear what one sounds like without a turbo on the manifold, drop by ;-)

[gbentink]

Hi Tim, it might be an idea to look at reducing the tension on the aneroid spring.....This is at the top left hand side of the pump :-)

EGT's should be tuned much lower in the lower rpm, best way is check for smoke, but could smoke as low as 500 deg C if at 1800rpm. Manufacturers on the old style engines typically opt on a ramp of 450 to 570 deg C (low revs to high revs).

Having said that, if you unscrew 1 more turn it will bring the boost up quicker anyway - 15psi @ 1800rpm is actually very good. Maybe worth a try, but I would be (pleasantly) suprised if you can get away with yet another turn and STILL avoid smoke!

An intercooler will also help alot ;-)

[Radd Cruisers]

Great read, good to see some new blood in these forums as it always makes for great variety of information.

[Tim-HJ61]

Originally Posted by gbentink

Hi Tim - Hey, I started my 12HT yesterday!! If you want to hear what one sounds like without a turbo on the manifold, drop by ;-)

I wondered about that thunder I could hear with clear skies :-)

I'll come around over the weekend

Plumma, and anyone else, there is a link to my thread on perth4x4.net that covers off increasing power on a 12ht including photos of THE screw.

Tim

[Tapage]