1HD-FT. The Story of an Engine That Wasn't Allowed to Breathe

[TheBussman]

I'm sure the VDJ filter is far finer for the common rail system and will make these old mechanical injectors last longer. i'm supersized that it has a primer pump on it As i figured those trucks would have an electric lift pump in the tank. Your using the 2 small barb fitting for the winter mode? No reason why you couldn't just cap those off and it would work like normal right?

 

[VADUS]

No reason why you couldn't just cap those off and it would work like normal right?

Just a little bit easier: the return hose from the tank (outlet) should be reconnected from the filter housing back to the pump. Accordingly, the inlet hose should be disconnected from the pump and looped back to the housing. These manipulations take a couple of minutes, and you have summer mode. Do it in reverse, and you will get winter mode.

 

[VADUS]

I'm sure the VDJ filter is far finer for the common rail system and will make these old mechanical injectors last longer

It is. That is why you should not buy the really fine ones with 10 micron filtration - it will increase a load on a low-pressure section of the pump. From this point of view, the best filter is 17540, which I've posted above.

 

[tekach]

First of all, I'd like to thank everybody for their contribution, this post (and it's links) is really packed with valuable information.

I own a HDJ80, it's a 1997 EU spec 1HDFT with EGR, manual transmission... I hope I can remove the EGR in a clean and safe way (and maybe add intercooler later).

I understand there are few stages and few approaches that one can take when removing EGR, but since I also plan high altitude trips (think up to 3500-4000m) this fact alone might have impact on decision making...

To my understanding, there were three approaches in regards to EGR with toyota's 1hdft, depending on market
1) egr with ecu (EU version I have ... and I also wonder what controls BACS VSV)
2) no egr with altitude compensator connected to vacuum source (Japanese style)
3) no egr with no altitude compensator (Australian style)

Reading through all the posts it seems that at first, recommended solution was to connect bottom boost corrector directly to vacuum, then later it was realized it's also needed to adjust the spring, but at the end it was recommended to use Australian style = to leave boost corrector open towards atmosphere.

Which approach would you recommend in my case?

Big thanks for your help, expert advice and sharing your experiences.

Best regards,
Andrej

 

[VADUS]

To my understanding, there were three approaches in regards to EGR with toyota's 1hdft, depending on market
1) egr with ecu (EU version I have ... and I also wonder what controls BACS VSV)
2) no egr with altitude compensator connected to vacuum source (Japanese style)
3) no egr with no altitude compensator (Australian style)

That's right.. And most important thing is, that in each of these three cases, the preload spring of the boost corrector diaphragm is tuned differently on the factory. Thus, if you want to switch your config. to any other, you will need to readjust the boost corrector. Actually, this is the only right way.

Regarding altitude compensator - the only two things this device does are reducing the vacuum power (it has small breather into the atmosphere) and shouting vacuum down on high altitude, that in its turn, leads to reducing an amount of injected fuel. So, it is another ecological device. which doesn't help on high altitude, moreover - it bothers and its primary goal is to reduce emissions and smoking. That's why the best option is Australian one. Or, if you are not ready to adjust your boost corrector and install EGT sensor etc., and if you are looking for an easy way to implement the non-EGR scheme and to get a quick result, you can just connect the straight vacuum under the diaphragm. It will lead to a very strong fuel correction, however, counting the overall wear-out of the fuel pump (which reducing fuel delivery), you can obtain pretty good result. I had been driving like this for a six years. But I recommend to start from the right way - install EGT sensor, make an Australian scheme with a little mod. and readjust boost corrector. The little mod. is to relocate the breather from under the diaphragm to a little bit higher. I've made it like this:

 

[HDJ80L]

I've tested both leaving the BACS port open to atmosphere (with a little filter) and running it under vacuum. Leaving it open the engine makes no power at all, using vacuum the power is good, huge difference in low/mid range compared to factory setup (with EGR). Probably not ideal and would require tuning of the compensator to improve on-boost fueling either way but I think its safe to drive like this and makes good power (little to no smoke and safe EGTs, running it for a few k's now). Have you ever tried to adjust the spring pre-tension in the compensator while running vacuum on the port @VADUS?

 

[HDJ80L]

As for altitude compensation, in this thread I speculated about whether the EGR equipped FTs had altitude correction through the computer controlled BACS VSV but have found no evidence for that in official documents. If neccessary I'd have a look into the mechanical compensator used on the JDM non EGR engines, no downsides using that one? Well, except that it will be difficult to source as I've read the part is discontinued.

 

[tekach]

As for altitude compensation, in this thread I speculated about whether the EGR equipped FTs had altitude correction through the computer controlled BACS VSV but have found no evidence for that in official documents. If neccessary I'd have a look into the mechanical compensator used on the JDM non EGR engines, no downsides using that one? Well, except that it will be difficult to source as I believe the part is discontinued.

I planned to.give it a try with toyota part nr 25709-54060. Seems same denso unit with different bracket.

But not sure anymore if I need it.

 

[VADUS]

Leaving it open the engine makes no power at all

Of course it does.. Like I said - you need to completely readjust your boost compensator to get a good result.

Have you ever tried to adjust the spring pre-tension in the compensator while running vacuum on the port

Yes I did that. The spring was released on 3 single clicks. Also I've turned the compensator shaft to choose the most optimal cone profile. But after all, I removed vacuum out of the boost compensator and completely readjusted the spring: - it was released for about 20-25 clicks. You have to choose the spring tension in accordance with your max. boost pressure. The main goal is to provide the maximum range for compensator shaft traveling, starting from the very low boost and finishing with the maximum boost pressure. You can mark the cone with the paint, apply required pressure and see - how long is the dash mark from the lever on the cone. The best result is when the dash stops at about the edge of the cone, almost reaching the waist (thalia) of the shaft. When you got your compensator adjusted for your max. boost pressure, you can start adjusting the main fueling screw. Important TIP - install EGT sensor and always watch for EGT.

But not sure anymore if I need it.

You definitely don't need it

 

[HDJ80L]

I was talking about factory settings without adjustments, with that you need the vacuum to make decent power (as you know). Haven't come around to do any adjustments but was also thinking about releasing the spring a few clicks as a simple measure. As you say to do it properly would require checking fuel pin travel and adjust for max boost and for that I like the idea of switching to the Aussie type setup as you can tune it easily without having to consider/adjust for vacuum.


As for the altitude correction, I think it's interesting that on the Japanese market Toyota found the need to fit a mechanical compensator on the non EGR variant while the EGR variant doesn't seem to have that feature. Maybe it does and it's just not obvious.

 

[tekach]

Please note, IF it matters, push rod in boost compensator for EU and JP version shares part number 22321-17840 while in AU it is different, 22321-17890. Diaphragms are all the same for all three markets, springs sets partially overlap, partially they have the same part numbers.

 

[HDJ80L]

I've noticed that too when I checked a while ago, the spring variants mostly overlap between EGR and non EGR. I think they were individually matched to each pump from the supplier so you can't really assign a specific part number to the engine variant.

 

[VADUS]

I think, that the spring difference is less im

As for the altitude correction, I think it's interesting that on the Japanese market Toyota found the need to fit a mechanical compensator on the non EGR variant while the EGR variant doesn't seem to have that feature. Maybe it does and it's just not obvious.

The thing is, the ECU of the EGR version strangles the fuel delivery in partial load modes. Therefore, no additional altitude compensation is needed there. As for non-EGR versions, apparently the Japanese couldn't allow their flagship Cruiser to puff black smoke on sacred Mount Fuji and thereby desecrate the holy place ). But seriously, the altitude compensator has a poor design because it constantly sucks dirty air from under the hood into the vacuum system through mediocre filters. In any case, the spring in such a boost corrector is preloaded differently than in the EGR version.

springs sets partially overlap, partially they have the same part numbers

The difference between spring types is not as critical compared to the spring preload (compression rate). Although for the Australian concept and for a longer correction range, it's probably worth choosing a longer and less stiff spring. Again, the starting point is the maximum boost pressure. The higher the maximum boost pressure, the longer range of shaft travel is needed for continuous and precise boost correction.

I was talking about factory settings without adjustments

The factory settings are socks. They consider the maximum boost pressure around 0.7 bar (for EGR) and 0.8 bar (for non‑EGR), plus emission norms by the EURO2 standard. If you want this engine to really go, you need to forget about factory settings

 

[HDJ80L]

The thing is, the ECU of the EGR version strangles the fuel delivery in partial load modes. Therefore, no additional altitude compensation is needed there. As for non-EGR versions, apparently the Japanese couldn't allow their flagship Cruiser to puff black smoke on sacred Mount Fuji and thereby desecrate the holy place ). But seriously, the altitude compensator has a poor design because it constantly sucks dirty air from under the hood into the vacuum system through mediocre filters. In any case, the spring in such a boost corrector is preloaded differently than in the EGR version.

We don't really know how the ECU operates exactly, as you stated its obvious that it strangles fuel delivery in certain conditions for emissions, that is very obvious driving with and without it. The computer having full control of the BACS VSV could perform a number of tasks, seamlessly increasing or reducing vacuum on the pump, including fuel compensation based on altitude. Like I mentioned in the linked thread above, most engine control units do it that way, adjusting fuel based on an inbuilt baro sensor. The 1HD-FT is of course far from a modern ECU controlled engine as only the EGR part is electronically controlled. If one is really interested, only two ways to find out: Either find confirmation in official documentation/manuals or veryify by measurement (data logging) on a standard vehicle which is quite the task requiring the right equipment.
To find out if adding a mechanical compensator (after EGR removal) makes sense will also require some testing at altitude as everyones setup and tune is different, I don't expect to I'll install one anytime soon but it's an interesting topic.

The factory settings are socks. They consider the maximum boost pressure around 0.7 bar (for EGR) and 0.8 bar (for non‑EGR), plus emission norms by the EURO2 standard. If you want this engine to really go, you need to forget about factory settings

Sure! I was simply trying to say with minimal effort, just removing the EGR system and hooking up the bottom port to vacuum makes a big difference and also seems to be "safe" to drive. Making further improvements by adjusting the compensator is definitely on the list now, thanks to your input.

 

[tekach]

Question for the experts (which I am not): would running rich at altitude mean higher EGT? Or have any other negative impact?

Think Atlas mountains - lots of steep ups and downs on curvy roads with heavy car, all on high altitude.

 

[VADUS]

would running rich at altitude mean higher EGT? Or have any other negative impact?

What do you mean by high altitude? First of all, for turbo-diesel any altitude under 3000m is nothing - you and your motor will not feel anything. Secondly, you can get noticeable increase in EGT under full load at the high speed - like 70-80 mph (110-130 km/h). I doubt that you will be able to drive that fast in mountains. If you are talking about mountain curvy roads, where the speed is usually less than 60 km/h, then don't worry about EGT at all. And finally - for really hard mountain conditions ALWAYS USE LOW GEAR in transfer case (with open center diff. of course) and engine braking. It will save your engine, your clutch, your gearbox, and what is the most important - your brakes and possibly your life.

 

[VADUS]

We don't really know how the ECU operates exactly, as you stated its obvious that it strangles fuel delivery in certain conditions for emissions, that is very obvious driving with and without it. The computer having full control of the BACS VSV could perform a number of tasks, seamlessly increasing or reducing vacuum on the pump, including fuel compensation based on altitude. Like I mentioned in the linked thread above, most engine control units do it that way, adjusting fuel based on an inbuilt baro sensor. The 1HD-FT is of course far from a modern ECU controlled engine as only the EGR part is electronically controlled. If one is really interested, only two ways to find out: Either find confirmation in official documentation/manuals or veryify by measurement (data logging) on a standard vehicle which is quite the task requiring the right equipment.
To find out if adding a mechanical compensator (after EGR removal) makes sense will also require some testing at altitude as everyones setup and tune is different, I don't expect to I'll install one anytime soon but it's an interesting topic.

This information is not a secret. You can search the web for a complete description of the EGR modes for FT and FTE engines. For the latter, there are delivery maps in accordance with other conditions. A dozen years ago I saw and learned that stuff. EGR always works under partial load modes, and NEVER works under full load. So, all of this stuff with HAC is a waste of time. It is useless.

 

[HDJ80L]

This information is not a secret. You can search the web for a complete description of the EGR modes for FT and FTE engines. For the latter, there are delivery maps in accordance with other conditions. A dozen years ago I saw and learned that stuff. EGR always works under partial load modes, and NEVER works under full load. So, all of this stuff with HAC is a waste of time. It is useless.

EGR and altitude correction are two separate topics that have nothing to do with each other, other than possibly being handled by the same control unit on the 1HD-FT. The information you are refering to are workshop documents meant for mechanics to repair, maintain and test the EGR system and give little to no insight to how the control system operates in regards to BACS (Boost Altitude Compensational Stopper). Since you mentioned it, the 1HD-FTE has a more sophisticated altitude compensation through the engine control unit, so from a manufacturers standpoint they certainly deemed it neccesary. You might get away with not having it depending on vehicle use, modifications, altitudes and driving style but I wouldn't call it useless.

 

[tekach]

What do you mean by high altitude? First of all, for turbo-diesel any altitude under 3000m is nothing - you and your motor will not feel anything. Secondly, you can get noticeable increase in EGT under full load at the high speed - like 70-80 mph (110-130 km/h). I doubt that you will be able to drive that fast in mountains. If you are talking about mountain curvy roads, where the speed is usually less than 60 km/h, then don't worry about EGT at all. And finally - for really hard mountain conditions ALWAYS USE LOW GEAR in transfer case (with open center diff. of course) and engine braking. It will save your engine, your clutch, your gearbox, and what is the most important - your brakes and possibly your life.

I mean Atlas (category 3000m), Pamir highway (category 4000m), Bolivian Altiplano (category 4000m)... those are the most demanding I did so far.

Good advice on open diff + low gear.

 

[VADUS]

EGR and altitude correction are two separate topics that have nothing to do with each other, other than possibly being handled by the same control unit on the 1HD-FT.

I think you are missing something here. These two 'separate' things are doing the same — reducing the amount of vacuum under the boost corrector diaphragm. And their final goal is also the same — to reduce the amount of injected fuel. So, if you consider HAC as a useful system, you might as well keep the EGR system with the same success. As for me, both systems are emission-based crap you need to get rid of.

Pamir highway (category 4000m), Bolivian Altiplano (category 4000m)... those are the most demanding I did so far.

What speed are you driving at?