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.