How to Add HAC to 3B engine in 81 BJ42

[cheric]

We have a 1981 BJ42 with AXT turbo. It does not have the HAC and we are commonly at altitudes from 1000 feet to 8000 feet, we live at 3500 feet. I can easily de-fuel it enough to not have EGT problem, but I was hoping I could add the high altitude compensator and be able to keep it fueled a little more. My questions are:

1) What parts do I need? I know I need the diaphram unit itself and perhaps some actuator rod? What else?
2) How hard is it to install? Is it a simple bolt on, or do I have to re-do a lot of stuff? It looks like a simple bolt on, and then add some fuel ...
3) Where can I get the parts -- does any have them for sale or know where I can get them?

Thanks! Eric

 

[Dieseler]

HAC reduces fuel supply at high alts when the air is thin this gives you proper air fuel mix without over fueling and billowing clouds of black smoke,not sure how you get a HAC to do the opposite of its function the turbo should supply extra air for the thin air problem if you need more fuel adjust your fuel screw just a notch this should help you out.

 

[cheric]

HAC

Yes -- if one has an HAC they can run at a higher level of fueling at 1000 feet because when they get to 8000 feet the HAC will defuel it. I want to use the HAC exactly as designed to allow me to run it with higher fuel levels at low altitude and automatically compensate to lower fuel at higher altitudes.

 

[lostmarbles]

I think all you need to do is replace your "full stop capsule" with a "diesel altitude compensator (DAC)". .... To use the terms given in my FSM.

 

[amaurer]

The EPC doesn't list it as a separate item so I doubt Toyota ever sold it as such. .... But no harm in asking them .... if you can find someone competent enough to be worth talking to

Only the bellows isn't listed separately, but I suspect he'll need the entire "Bellows Assembly" anyway, so no biggie.

BELLOWS ASSY, PNEUMATIC
22680‑48061 B, 3B, 2H..BJ4*, HJ47; W/HAC

My usual place for Toyota parts doesn't list that number, however, so it may be unavailable. Someone like Dave (Japan4x4) has ways of getting such things that are unavailable to mere mortals, I'd try him.

 

[lostmarbles]

Only the bellows isn't listed separately, but I suspect he'll need the entire "Bellows Assembly" anyway, so no biggie.



My usual place for Toyota parts doesn't list that number, however, so it may be unavailable. Someone like Dave (Japan4x4) has ways of getting such things that are unavailable to mere mortals, I'd try him.

Thanks Drew. - I've removed the incorrect stuff I wrote in my post. (For some reason I didn't at first notice that the "bellows assembly part number" was there.)

And that bellows assy part number you gave was apparently later substituted by 22680-48062.

 

[BreckenridgeCruiser]

I'm not sure if you were the guy looking to buy one on the JDM classifieds sections, but be aware of the limitations of these. I had a HAC on my gasser and it only compensated for 0-3800 feet and then was full open. Any altitude gain above that and the hac was not effective. I'm not sure of the operating specs of the diesel hac, but it looks like the same mechanics and probably has the same limitations.

I just tune my fuel when I drop to a lower altitude for any substantial time period. I find the turbo allows for a greater amount of variation without affecting my EGTs too badly.

my .02

 

[canucksafari]

I don't understand why you think you need a HAC when you have a turbo. The turbo alone is a HAC.

 

[cheric]

Thanks for all the info.

I believe the diesel HAC is better than the gasser one. The turbo adds more air as boost goes up. Boost is a mechanical function mostly determined by the amount of fuel burning which creates exhaust. It does not comensate for altitude -- that is, I won't get more boost at a higher altitude, all other things being even. My modern Ford Powerstroke will do exactly that because it is run by a computer that compensated for altitude. As you go up in altitude, if you wants the same fuel/oxygen ration all the time you either have to increase boost without increasing fuel (because you need more air at higher altitude to get the same oxygen) or you need to decrease fuel. Perversely, if you decrease fuel you lose power, so you put your foot down farther, and boost goes up and power is maintained ... but with the correct ration. It only takes me 15 minutes to go from 3500 feet to 6500 feet, and 10 more to be close to 8,000 -- I can't just change my fuel screw to compensate. I go up/down several days a week, and I would have to get out every few miles and adjust it! I think the HAC would be exactly what I want if it works

 

[amaurer]

You're very confident that in the HAC for someone who's never driven with one (I haven't either, mind you). The majority of the posts I've caught on this board wonder if it does anything at all.

Still, at 5000', the density of the intake charge is only 17% lower that at sea level, its hard to imagine that if you turned the fuel down by 17% that the truck would become undrivable - the net result would be that, at sea level, you'd be 17% slower than you are now, but would be no slower than you are at altitude (e.g. still fine).

I've been well past 5000 with no turbo OR HAC and did just fine as well. "get[ting] out every few miles and adjust" the fuel is silly hyperbole, and completely unnecessary.

 

[cheric]

Not really that confident

Thanks for your input.

I'm just confident I want to try it!

I was only trying to express how fast and often I change altitude. Most people live on the flatlands and go to the mountains occasionally. I am "on the slope" so to speak ... and change often and by a large amount. To go visit my brother or to go out to dinner or whatever could be a 5000 foot elevation change in well under an hour. Which means any ideas concerning manually changing the fuel metering won't work for me.

 

[RufusTheDufus]

Has anyone used the HAC as a fuel enrichment device? I'd like to try to figure out a way to do it.

Instead of providing atmospheric pressure to the HAC it could be plumbed to get its signal from the intake after the throttle plate. It would most likely need some type of inline boost controller to tune the signal going to the HAC.

 

[BreckenridgeCruiser]

The HAC has a sealed bellows in it as the vehicle climbs into altitude, air pressur drops. Therefore the volume of isr sealend inside of the bellows expands (as the air pressure differential drops across the mebrane). The bellows expands, pushing a mechanical method of leaing out fuel or increasing air. Again, Toyota was a japnese compnay and all hacs I've seen were for 0-3800 feet., would love to find out the op specs on this thing. Even so, I bet the turbo makes enough of a differnece that you would feel nothing. From a piece of mind and the desire to not run a leaned out rig, I get hwere you are comig from, just not sure it's worh the effort. Love to hear more though!

 

[roalco]

The HAC has a sealed bellows in it as the vehicle climbs into altitude, air pressur drops. Therefore the volume of isr sealend inside of the bellows expands (as the air pressure differential drops across the mebrane). The bellows expands, pushing a mechanical method of leaing out fuel or increasing air. Again, Toyota was a japnese compnay and all hacs I've seen were for 0-3800 feet., would love to find out the op specs on this thing. Even so, I bet the turbo makes enough of a differnece that you would feel nothing. From a piece of mind and the desire to not run a leaned out rig, I get hwere you are comig from, just not sure it's worh the effort. Love to hear more though!

Far as I know, that's it in a nutshell, except technically it doesn't really lean out the fuel, it reduces the maximum fuel rack setting by moving the fuel stop positon. It also has a spring loaded section in the actuating arm that acts as a rack damper to slow accelleration in the top part of the rack travel range (more vacuum needed to increase fuel), all of which means as simple way to make less smoke (overfuelling) at altitude if the driver is driving it hard (skinny to the floor).
I'm not sure of the 3800 foot range, I'm going to put my spare HAC into a vacuum pot with an altimeter and see what the travel range actually is.
There is also an internal adjustment that actually moves the entire aneroid assembly back and forth, I'm not sure if it can be used to effectively alter the range set point or not ... very little in the FSM's on it.

 

[canucksafari]

all of which means as simple way to make less smoke (overfuelling) at altitude if the driver is driving it hard (skinny to the floor).
I'm not sure of the 3800 foot range, I'm going to put my spare .

Basically how I control overfueling with my NA TD4.2 is to drop a gear when I see any black smoke in my mirrors. Once you have diven your truck for a while, you will know what it feels like when you're overfueling without looking in the mirrors. With my engine, if i can easily maintain 2600-2800 rpm, I know I have the right gear and the right amount of skinny foot. I've been up over 6200' without issue - besides going a bit slower.

 

[roalco]

Basically how I control overfueling with my NA TD4.2 is to drop a gear when I see any black smoke in my mirrors. Once you have diven your truck for a while, you will know what it feels like when you're overfueling without looking in the mirrors. With my engine, if i can easily maintain 2600-2800 rpm, I know I have the right gear and the right amount of skinny foot. I've been up over 6200' without issue - besides going a bit slower.

Exactly!!!!!!!!!!!!!!!!!!!!

 

[cheric]

Thanks for all the replies, love to know the range

Since I live at 3500 and if this is used as zero, then when I go up it should compensate for 7300 feet which would be pretty good. I have poor impulse control on my right foot and I feel better if the truck would simply not reach insafe EGT. I am a bit spoiled by my modern Powerstroke which increase boost and de-fuels as needed by computer ... it de-fuels when EGT hits 1350 and keeps it from going over that no matter how hard I press the pedal. At higher altitudes it runs much higher boost for the same effort as it does at low altitude. I have my Cruiser set to 12 lbs max boost, the Powerstroke at 30 lbs! When pulling a 10,000 lbs trailer up these grades that is pretty critical. I know an older truck cannot be expected to be the same, but ... maybe I get some protection with the HAC. I have found one with brackets for 50 bucks ... and I "think" it is easy to install (never is ). Eric

 

[RufusTheDufus]

You might want to compare the injection pump casting where the HAC bracket mounts to your pump. I think the castings might be different. I don't think it will be a simple bolt-on procedure. You may need to make your own custom bracket.

 

[cheric]

Casting

Rufus -- I think you are right. It also looks like making a bracket won't be too hard ... I'll make a full report once I get it done! Eric