My HJ61 Rejuvenation

[Fifty Hertz]

Shortly after this I finally got around to fitting a "new" sound system. Fortunately a friend had a decent Pioneer double DIN unit that fitted. So the dash came apart to run all the wiring.

Head unit in.

I've put in a basic 2x 50W RMS amp. At the moment this is mounted on the front face of the drawer unit, although I may well relocate it later.

I've fitted a pair of 6.5" bookshelf speakers on the rear cargo divider (my fancy term for a piece of plywood). Had them kicking about as workshop speakers. The brackets allow them to pivot through 180°, so they can be turned around to face out the back when parked up.

Testing with some tunes

 

[Fifty Hertz]

I'm up to May 2019 now.

Late night preparations...

...for a quick weekend away with a few other 60 nutjobs...

 

[Fifty Hertz]

 

[Fifty Hertz]

Another weekend away. In October, so well into spring.

A pair of 60's

A trio of 60's

A 60 quartet

Three 60's and an 80

Five 60's and a 40

 

[Fifty Hertz]

I really love the west coast of Australia. So many awesome spots to explore and camp.

 

[Fifty Hertz]

Ok that's enough of the beauty shots for now. Time for an update on further mods

It's always been in my long-term plan to realise more power from the 12H-T. Now that the engine is fully run-in, I've decided to go to the next stage. Up until recently, I've only been running 15psi boost, which is moderate for a 12H-T. The limiting factor has been keeping the EGT to a safe level with the boot in it. The obvious solution: intercooling.

We're fortunate in Australia in that we have a really strong aftermarket scene for performance diesel products. A number of companies in particular do intercooler kits for various common vehicles. When you get into the older rigs like a 60, the options are of course more limited. But luckily for me, there are a few options for intercooling a 60. Check out HOME - Cross Country 4x4 Intercooler Systems for some examples. Although not listed, they do a very nice kit for the 60... which I went ahead and ordered. 8 days later, this arrived on my doorstep.

It's a 600mm x 300mm core. They've kept with a 50mm thickness, to keep the profile low and be able to fit it under the 60 bonnet (there isn't much clearance as it turns out). It comes with a fan on the hot side and a very nice mounting frame, which I'll explain in the next post.

 

[Fifty Hertz]

Installation of this kit is super simple and straightforward. It took a couple of hours, with a helper to assist lifting and positioning the core and mounting assembly. Plus an hour or so to wire the fan.

Finished result.

The way that the mounting frame works is quite clever. It actually mounts to the body rather than the engine, with the flexible silicone hoses allowing the engine to move relative to the intercooler.

The main advantage of this (aside from ease of fitment) is that the intercooler core moves in unison with the body, keeping it sealed tightly against the underside of the bonnet for maximum airflow through the core. Setups with the intercooler mounted to the engine typically require proper flexible bellows to seal the secondary air path whilst allowing adequate engine movement.

Here you can see the how the core mounting frame goes in. It's an intricate NC-formed tubular structure, engineered to fit perfectly around the engine and ancillaries, taking support all the way to the front panel.

Here's the core mounting frame detail.

At the front, two holes need to be drilled in the top of the radiator support panel (one on each side). These are the ONLY holes and irreversible modification that need to be done for the entire installation.

At the rear, the mounting frame clamps onto the welded seam of the firewall. It's solid and simple, and allows for a bit of lateral adjustment to get it sitting in just the right location. I've since put a strip of high density rubber over the seam to help it grip and prevent it rubbing the paint off. After several thousand k's it hasn't moved any.

 

[Fifty Hertz]

The most time consuming and tricky part of installing a top mount intercooler is marking and cutting the bonnet for the scoop. Now I didn't have this problem, as I'd already cut out an aperture for the VDJ scoop during the bodywork and painting phase.

The only problem I had is that the aperture is much larger than required. This was intentional. When I was doing the body, I didn't know exactly how the intercooler was going to be sized and located, so I made the aperture as large as possible with the expectation that modification would be required later. Obviously, modification is now required.

I made up an infill panel at the front edge using 2mm aluminium. This is riveted to the sheet metal.

I've also fitted a 20 x 20 aluminium angle on the underside, to stiffen it up and stop things vibrating.

There was only a small gap at each side, which I've similarly filled in with aluminium.

 

[Fifty Hertz]

Here's a view from underneath, with the pinchweld seals in place.

View of the rear of the core. As can be seen, I've placed the rear pinchweld seal on the welded lip of the core rather than the bonnet. Serendipitously, this sits in just the right place to seal up on the underside of the bonnet, as the bonnet sheet metal just overhangs the core. Putting the rear seal on the bonnet would have necessitated trimming the aperture out further at the rear. By going this way and putting the rear seal on the core, I avoided having to do any further cutting.

Here's the detail on the hot side.

Front view with everything in place.

 

[Fifty Hertz]

So what to do next after that? A dyno tune of course!

For this, I've gone back to the gurus - GTurbo in Balcatta, Perth. They made the "Grunter Extreme" turbo that I have on there, so they know better than anyone how to set them up.

The results?

The curves are somewhat disappointing. There are two main issues. Firstly, it's not developing boost down low to bring up the bottom end torque. Then it's running out of fuel by 2000 rpm. The AFR is literally off the chart, that's how lean it is.

So there's room for improvement here.

 

[Fifty Hertz]

On the dyno

 

[Fifty Hertz]

I drove around like this for 6 months, kinda happy with it but at the same time, kinda not. I mean it was certainly better than it's ever been. But it's frustrating knowing that there is (at least in theory) a whole lot more power there waiting to be unleashed.

After doing some research and talking again to the guys at GTurbo, I decided to bite the bullet and get the injection pump modified. For this, it was sent to ADS in Queensland.

They are experts on the older fully mechanical injection systems. They do a special high-flow pump for the 12H-T. They take your stock pump and fully strip it down. The pump elements are bored out and matching pistons installed from a Cummins injection pump. This gives the pump ~60% more flow. The whole pump is rebuilt with whatever new parts are required.

The second modification they do to the governor. They setup the governor specifically to suit the operating characteristics of the 12H-T with a GTurbo. They also modify the boost compensator, by fitting a diaphragm spring that is made to their specifications. These work together to supply the right fuel for a higher flowing 12H-T. A key part of this is a quicker response down low, feeding in more fuel earlier. This has a compounding effect, whereby the increased fuel flow increases the exhaust gas velocity and therefore spools up the turbo sooner, which in turn builds the boost quicker.

The final element for power is modified injectors. These also need to rebuilt to support the higher fuel flow, at the same time optimising the spray pattern and injector opening pressure.

As I'm now working away on site again with limited spare time, I opted for a drive-in drive-out service from GTurbo. They removed the pump, sent it to ADS, then refitted it and did a full dyno tune.

I don't have any photos to show of this work, other than a shiny pump. This is going to rust pretty quickly, so I've since given it a liberal coating of fish oil.

Here's the before chart again for reference.

370 Nm @ 2300 rpm | 95 kW @ 3250

And here's the after chart.

528 Nm @ 1750 rpm | 122 kW @ 3300 rpm

The difference is like night and day. The peak torque has shifted from 2300 to 1750 rpm. And look at the curves at 1500 rpm: it's DOUBLED, going from 250 to 500 Nm.

I'm super pleased with how it goes now. The drivability improvement is phenomenal, translating to a whole lot less cog-swapping and lower overall revs used under all conditions. Steep hills around home that previously required second are now easily taken in third with an upshift to fourth, which wasn't physically possible previously.

The 60 finally feels like the rig it was always meant to be

 

[LCnAZ]

My wife would kill for that orange. Great rig, sir.

 

[Fifty Hertz]

My wife would kill for that orange. Great rig, sir.

Cheers. FYI it's BMW "INKA". They offered this as a standard colour on the 2002 and E9 coupe (pictured) in the 70's. I always loved it and wanted something a bit different, so voila!

 

[Silveredition]

I like that dyno chart!
What differences in the dyno results would you expect on 31” tyres instead of the 33’s?

 

[Fifty Hertz]

I like that dyno chart!
What differences in the dyno results would you expect on 31” tyres instead of the 33’s?

No difference in power (kW) figures.

For torque, it depends on how the dyno is setup and what calculations have been applied to the measured values. Chassis dynos measure torque and rotational speed at the roller, that's how they work. The dyno operator has the option (using the menus in the dyno software) to display the torque as a "roller" torque or a "derived" torque. Roller torque is exactly that: the torque that the tyres are applying to the dyno roller. Derived torque is obtained by applying a calculation that compensates for the torque multiplication of the drivetrain to ESTIMATE the torque produced by the engine. This is typically just the diff ratio and the tyre OD, as dyno runs are normally done in direct 1:1 drive, so no transmission correction is required.

So if the dyno chart is showing the derived torque, then changing the tyre size should make no difference. If the dyno chart is showing the roller torque, then the values will obviously be affected by a change in tyre OD.

If I were to change from 33" to 31" tyres, the effective roller torque would be increased to 33/31 = 106.5%.

 

[Skniper]

So much freekin’ goodness here.

 

[Fifty Hertz]

So much freekin’ goodness here.

Thanks mate, I'm glad you like the content. I've tried to keep it informative, without going overboard on the words. There's still a fair bit to do, mostly on the interior fitout, ancillary electrics and other things for touring and camping.

So there will be more progress to come

 

[BHillteq]

Just finished reading through the build, and dang! Such a rad Cruiser. Incredible work with everything! And looks like a total blast to drive.

 

[SierraDelta]

Mate, I registered just to say well done, shes a beauty.

I have a 1986 HJ61 Sahara high top stored away ready for a similar project rebuild! Healthy 12ht with a mere 300k on the clock