High altitude compensator 1HZ retrofit? (1 Viewer)

[JDM Journeys]

Boosting the 1hz has its champions and detractors, but there is no denying that in stock form it suffers as the air density decreases.

Without diving into turbo debates, I'm wondering about high altitude compensation.

In some markets it came from the factory with an HAC on the injection pump. Has anyone here added one to a rig that didn't originally come with it? Did you see any real world difference as your altitude increased? Was it worth the effort/expense?

 

[Krankieone]

Following with interest In going the turbo route but very curious to know how it works.

 

[JuanJ]

Hello,

HAC and a low-pressure turbo. HAC will ease your altitude concerns. A low-pressure turbo will add some power without stressing the 1HZ.

There is a thread on the install of both in a BJ70, complete with the engine swap, very detailed and worth checking. The search function is your friend.






Juan

 

[JDM Journeys]

A search yielded nothing specific to the 1HZ in terms of an HAC retrofit. And as of this moment, as I said above, I am looking at the non-turbo options. As far as I know, the HAC is removed when adding a turbo, and replaced with a boost compensator, which performs a similar function, but in tandem with a turbo.

I'm simply looking at all options, but surely someone has tried this before me.

 

[JuanJ]

Hello,

This is the thread:

Builds - 1985 BJ70 Story and Modifications

Greetings, I wanted to initiate a thread about my 1985 CND BJ70 and hopefully tell the story and provide some details about the modifications that I have done to the vehicle. This is not intented to be a full restore/refurbrish of the truck, but rather fix some issues and enhance the...

forum.ih8mud.com

I would tune the turbo for low-pressure boost.

Hope this helps.





Juan

 

[likethewheel]

I’m struggling to source a boost compensator for 1HZ but I did manage to find a HAC and I’m being told that the HAC will function similarly to the BC with a turbo installed. Main difference being the HAC can’t handle quite as much boost as the BC. Does this sound accurate? Seems to me you’d ideally want both but curious to know what kind of boost one could safely run with just the HAC?

 

[Blomdala]

I’m struggling to source a boost compensator for 1HZ but I did manage to find a HAC and I’m being told that the HAC will function similarly to the BC with a turbo installed. Main difference being the HAC can’t handle quite as much boost as the BC. Does this sound accurate? Seems to me you’d ideally want both but curious to know what kind of boost one could safely run with just the HAC?

Look as safari turbo install instructions. They show using the HAC for a boost compensator. If you want to get deeper into "tuning" the HAC as a boost comp, you may have to lead the way on it as most install the boost compensator when going the turbo route.

 

[wjyeo103]

I’m trying to retrofit a HAC like the OP. Injector pump ran fine before I swapped HAC on, and it worked fine after it took it off. With the HAC on it refused to work at all, no fuel plumes from glow plug holes or injector fittings.
I’m not exactly a noob at working on the 1HZ, and this would normally be the point where I just look in the shop manual for the differences in adjustments between w/HAC and without it, but apparently it’s easier to find the Russian nuclear codes than anything about the HAC. Can anyone point me at any reasonably detailed information about installing the HAC? The only difference in parts that I can tell is that the return manifold bolt differs a bit because the end goes into the body of the injector with the normal top, and there’s a port in the HAC body instead.
It just can’t be this hard to find info on a stock 1HZ part!

 

[JDM Journeys]

Wish I could say I got somewhere with this, but I didn't. Doesn't seem to be anybody retrofitting.

I'm running at 1100m of elevation daily. I advanced the pump a little until I got the best compromise between fuel consumption, black smoke, and white smoke on cold start.

 

[wjyeo103]

I took a look at the Safari turbo destructions like Blomdala suggested. Makes me wonder if increasing fuel flow with the main fuel screw because there’s more headspace between the injector body and the top of the HAc than between the body and the regular top?

 

[wjyeo103]

Thanks JDM. Apparently Toyota considers the HAC information top secret or something. Guess it’s just time to tweak timing & fuel ratio until something works. If I figure it out I’ll post the procedure.

 

[Blomdala]

Thanks JDM. Apparently Toyota considers the HAC information top secret or something. Guess it’s just time to tweak timing & fuel ratio until something works. If I figure it out I’ll post the procedure.

The hard part is its likely not Toyotas design info for it, probably Denso or Bosch has the deeper details. I'm sure some down under who rebuild pumps and could give instructions to make it work.

 

[wjyeo103]

The hard part is its likely not Toyotas design info for it, probably Denso or Bosch has the deeper details. I'm sure some down under who rebuild pumps and could give instructions to make it work.

That’s a couple of good potential leads Blomdala, thank you. I don’t know why I didn’t try to hit up somebody in Oz since my truck came from there. I’ll check into it.

 

[JDM Journeys]

@wjyeo103 wondering if you ever made any progress with this? I've had a full season of trips with my 1hz and am now looking at options again for making its performance a little more optimal at altitude, esp with the weight I've added, not to mention living in the foothills.

If HAC was a simple bolt on and go it'd be a no brainer, but it doesn't sound like it is?

 

[Blomdala]

@wjyeo103 wondering if you ever made any progress with this? I've had a full season of trips with my 1hz and am now looking at options again for making its performance a little more optimal at altitude, esp with the weight I've added, not to mention living in the foothills.

If HAC was a simple bolt on and go it'd be a no brainer, but it doesn't sound like it is?

One other thing to take a look at might be 1st gen 12v Cummins pump parts. I have been graced with one in my side yard now and the pump looks identical. Different shaped compensation top, but the bolts and throttle linkage hole looks identical. Those have to be easy and cheap to get

 

[JDM Journeys]

One other thing to take a look at might be 1st gen 12v Cummins pump parts. I have been graced with one in my side yard now and the pump looks identical. Different shaped compensation top, but the bolts and throttle linkage hole looks identical. Those have to be easy and cheap to get

Oooh. Around here the Cummins is as plentiful as a field of wheat. Thanks for the idea! I'll have to check out that avenue.

I'm assuming it would be a *boost* compensator on the Cummins, as opposed to an alt compensator? Without a turbo, I wonder if I could still retrofit it?

 

[Blomdala]

Oooh. Around here the Cummins is as plentiful as a field of wheat. Thanks for the idea! I'll have to check out that avenue.

I'm assuming it would be a *boost* compensator on the Cummins, as opposed to an alt compensator? Without a turbo, I wonder if I could still retrofit it?

You got it! They are all turbo on the dodge so they have the actual boost comp! When I see videos online if people pulling the pin out to modify it, it looks just like ours. Worst case scenario you need to grab a pin for a Toyota but at least those exist. I would guess a factory Cummins pin could be tuned enough though, both 6cyl.

 

[JDM Journeys]

Well, I was able to source an HAC from a member on here, and its on its way from the US as we speak. I'll source a gasket for the cover before I attempt any disassembly. Then I'll see if it makes any difference. This truck lives at 1100m (3600 feet) and regularly sees climbs to 5000 feet in the summer.

 

[mt72]

Subscribed! Did you have by any chance the part number for the HAC? Please share your set up too this looks like a very good option

 

[JDM Journeys]

Subscribed! Did you have by any chance the part number for the HAC? Please share your set up too this looks like a very good option

It is NOLA from what I can tell, but it's still listed on places like partsouq. I'll post up here with the pn# and of course keep you updated with my fitment.