I'm sharing an English translation of my article, originally written for the Russian Land-Cruiser community. I hope it will be a helpful resource for Toyota diesel enthusiasts worldwide. The article references several detailed technical threads from
Land-Cruiser.RU; you can use browser translation tools or Google web-page translator to read them.
In our daily lives, we often encounter peculiar paradoxes. For instance, powerful sports cars are sold all over the world. However, we can count on the fingers of one hand the number of countries with roads that allow a sports car owner to unlock the full potential of their steel steed, or to travel at high speed without risk to themselves or others. If we consider the legal aspect, the number of such countries becomes even smaller. Yet, we see these high-performance cars with their powerful engines more and more often stuck in endless traffic jams... As a long-time owner of the 1HD-FT engine, I would like to tell you a story about a similar paradox that happened to this remarkable powerplant. Nearly all the issues discussed here have already been covered on our forum in one form or another, often in even greater detail. However, the time has come to gather and systematize all the accumulated information, to transform quantity into quality, and to draw the appropriate conclusions.
So, the 1HD-FT engine—a 4.2-liter, inline-six, turbocharged diesel with mechanical fuel injection and a four-valve head—began to be installed in the Land Cruiser and Coaster from January 1995, replacing its two-valve predecessor, the 1HD-T (in all markets except for "general countries"). It would seem that the adoption of a four-valve design should have given the engine a significant boost in power and torque. But in reality, according to Toyota's official specifications, the 1HD-FT surpasses the 1HD-T by a mere 9 percent in peak power, and its advantage in peak torque is even smaller—just 6 percent. This seems rather meager, especially considering that the 1HD-FT's injection pump has a significantly more aggressive cam plate and is capable of delivering much more fuel to the cylinders. Of course, if we examine detailed power and torque curves for some specific modifications* of these engines, we will see that the 1HD-FT's superiority is more pronounced in the mid-range RPM, in some places reaching up to 20 percent. Nevertheless, the question arises: was it really worth it for the manufacturer to introduce such major changes to the engine's design—a completely new cylinder head and injection pump (not to mention the lesser modifications)—only to achieve such a modest gain in performance? I think not.
So, what happened, and why did Toyota take this path?
A common misconception is that the 1HD-FT was merely a "prototype" or a testing mule for the 1HD-FTE, with the manufacturer simply preparing the hardware for its future flagship diesel with electronically controlled injection. However, considering that the 1HD-FT was installed in the Land Cruiser and Coaster from 01/95 to 01/98, and continued to be installed in the Coaster for a year and a half
after the launch of the 1HD-FTE, until mid-1999, it becomes obvious that this view is far from the truth. "Test" versions are not produced for almost five years, and they are certainly not continued after the final version has been launched. So, where do we find the answer to our question?
The answer lies in a different direction. The 1HD-FT was, in a literal sense, unlucky—its launch in 1995 almost perfectly coincided with the adoption of the notorious Euro 2 standard. Of course, manufacturers knew about this event in advance, and it's equally clear that the new engine modification had been designed and tested for at least a year or two. Nevertheless, Toyota was forced to release two different versions of the 1HD-FT: one compliant with Euro 2 norms, and one non-compliant. It's obvious that the version
not compliant with Euro 2 was the more powerful and capable one. And it was this specific modification of the engine (*) that had up to a 20% advantage in the working RPM range compared to its 1HD-T predecessor. This issue is discussed in more detail in the thread via this link:
1hd-t или 1hd-ft на 105-ку ? Помогите выбрать. - http://www.land-cruiser.ru/index.php?showtopic=145779. But unfortunately, this modification was supplied only to Australia, and in small batches to the Japanese domestic market. The rest of the world had to make do with the more "progressive" version of the engine, compliant with the Euro 2 environmental standard. What was the price of this compliance?
The price turned out to be quite high. The 1HD-FT engine was equipped with an EGR system, with all the unfortunate consequences that entails. The manufacturer had to install a full
two EGR valves to strangle the engine down to Euro 2 norms. The EGR system adds exhaust gases to the intake manifold under certain engine load conditions ("partial" load modes), which reduces the amount of oxidizer in the combustion chamber. As a result, the combustion temperature of the mixture drops, achieving the primary environmental effect – a reduction in NOx emissions. The total mass of gas in the cylinder remains the same and is heated to the required temperature during the compression stroke. It's just that part of this gas does not participate in the combustion process. Furthermore, the EGR system's computer also limits fuel delivery, accounting for the reduced amount of oxidizer in the combustion chamber. On the 1HD-FT engine, pump control is managed through a vacuum actuator for the boost compensator—a rather perverted hybrid of a fully mechanical injection pump and an electronic control system. In other words, in certain engine operating modes, its power is forcibly limited. All other supposedly "positive" effects of the EGR system, such as "after-burning" of unburned fuel, reduced thermal load on the engine, etc., are nothing more than marketing nonsense pulled out of thin air. For those who are not well-versed in technical matters, I can offer a simple, accurate, and crude everyday analogy: the EGR system works as if, under severe financial constraints, you were forced to mix your own excrement from breakfast into your lunch, from lunch into your dinner, and so on. The size of the servings would be larger, but something horrible would happen to your body.
The introduction of the EGR system alone proved insufficient to meet Euro 2 standards. The four-valve system was well-designed and continued to supply a sufficient amount of air for efficient fuel combustion. Therefore, it became necessary to reduce the air supply by deliberately impairing combustion chamber ventilation. To achieve this, the maximum boost pressure of the 1HD-FT's turbocharger was reduced to 0.7 atm (the Toyota manual specifies a check range of 0.38-0.5 atm with no load). The maximum boost pressure of the two-valve 1HD-T was 0.8 atm (check range 0.5-0.65 atm with no load). This means both the operational and maximum boost pressures of the EGR-equipped engine were significantly reduced. Meanwhile, the non-EGR engines continued to be fitted with turbochargers featuring a wastegate that allowed them to reach the designed maximum of 0.8 atm, even though Toyota's parts catalog does not formally specify this difference.
A similar "trick" was performed with the exhaust system – as a "gas mask," the engine was simply fitted with the old exhaust system from the two-valve 1HD-T. As they say, "cheap and cheerful," with the added bonus for the manufacturer being "parts unification." Apparently, in the spirit of this same unification, the old exhaust system was also installed on non-EGR models (since very few of these were produced). For the sake of fairness, it should be noted that even the old exhaust system on non-EGR 1HD-T and 1HD-FT engines for Australian and some Asian markets differed from those for other markets, offering less resistance to exhaust gas flow due to the absence of an additional muffler in the final section.
We should also remember the "environmental legacy" inherited from the Euro 1 standard introduced in 1991. Back then, with the launch of the 1HD-T, its thermostat lineup was reduced to just one model with a range of 76-90°C. It made no difference whether the vehicle was destined for Africa or Northern Europe – there was only one thermostat. The goal was the same: to lower the combustion chamber temperature and reduce NOx emissions. Before Euro 1, the predecessors of the 1HD-T had a full range of thermostats: 76-90, 82-95, 88-100. The 1HD-FT inherited from the 1HD-T this same single, unique "African" 76-90 thermostat.
As a result of the measures described above, the 1HD-FT engine complied with the Euro 2 standard. However, in doing so, the 1HD-FT's dynamic characteristics were practically degraded to the level of its two-valve predecessor, the 1HD-T. Meanwhile, Toyota was already preparing for the introduction of the stricter Euro 3 standard. It was clear that electronic control over fuel quantity, air flow, fuel temperature, etc., would now be essential. This meant abandoning Toyota's legendary diesel reliability but allowed for the restoration of previous, and even higher, levels of air and fuel in the cylinders, improving performance without exceeding the stricter Euro 3 emission limits. Consequently, ahead of the Euro 3 norms taking effect in 1999, Toyota prematurely launched its new flagship, the 1HD-FTE, with its electronically controlled injection pump. Boost pressure was returned to the 0.7-0.85 atm range for Europe and 0.85-1.0 atm for "non-suffering" regions, an intercooler was added, fuel injection pressure was increased, and finally, a completely new exhaust system was fitted, allowing the engine to breathe properly. The EGR system had to be retained, although even this new engine had a superior Australian version where the EGR system was not installed.
Let's return to our hero, the 1HD-FT. Was it destined to "sniff" its own exhaust and remain in a gas mask for the rest of its existence? Of course not. And Mother Toyota left us many paths for retreat. This is especially true given that the engine's potential was clearly demonstrated by Yanmar with their 300-horsepower marine engine, the 6LPA-STP, producing 700 Nm of torque and built on the basis of the 1HD-FT with mechanical fuel injection. Naturally, extracting such power imposes certain longevity constraints, so we will focus on modernizing the 1HD-FT within the service life originally intended by the manufacturer for this engine. So, what needs to be done to achieve this?
A Guide to Liberating the 1HD-FT: Restoring the Engine's True Potential
1. EGR Removal
The first and most critical step is to disable and, preferably, completely remove the EGR system, including cleaning and replacing any related components. The "why" and "how" are detailed in these threads:
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EGR system removal and cleaning
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EGR valve study and diagnostics
2. Restoring Mechanical Pump Operation
Next, eliminate the influence of the EGR computer on the injection pump's fuel delivery. This effectively returns the pump to the standard operation of the rare, non-EGR models. The procedure is described here:
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EGR computer removal and injection pump adjustment
3. Optimizing Air Intake
Use the original air filter
17801-61030. This filter offers less airflow restriction compared to the
17801-68030 filter designed for EGR-equipped engines. The 17801-61030 was used on non-EGR Australian 1HD-FT models and is also rated for the more powerful 1HD-FTE and 1FZ-FE engines. A bonus: it is washable for extended service life. In reality, even this filter is a restriction. A more radical solution is to modify the airbox to accept a larger filter from the 100-series. Details here:
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Modifying the airbox for 100-series filter element
4. Installing a Proper Thermostat
If you live in a temperate or northern climate, replace the thermostat with one suited to your region. For more information, see:
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Thermostat selection and replacement
5. Freeing the Exhaust
The next step is to remove the "gas mask" by replacing the restrictive exhaust system. While fitting a 1HD-FTE system is difficult, there are many quality aftermarket options from manufacturers like Fujitsubo, Ganador, and Saxon that offer high-flow systems for this engine. For examples, see:
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Aftermarket exhaust systems discussion
6. Restoring Boost Pressure
Return the turbocharger's maximum boost pressure to its original designed value of 0.8 atm. It is also advisable to use a two-stage boost controller for the wastegate for more effective low-end response. See this thread:
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Boost controller installation and tuning
7. Camshaft and Cylinder Head Upgrade
Installing a camshaft from the 1HD-FTE is a worthwhile upgrade. This cam has a more low-end and mid-range performance, as its intake valve closing timing occurs 8 degrees earlier compared to the FT cam (24° ABDC for FTE vs. 32° ABDC for FT). If you need to replace the cylinder head, it is recommended to use one from a 1HD-FTE, as it incorporates several useful improvements. More info here:
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1HD-FTE cylinder head and camshaft upgrade
8. Post-Modification Results and Further Tuning
After these modifications, you will finally experience what this remarkable engine was meant to be. You will find that its performance is nearly on par with its electronically controlled, intercooled sibling. Note that we have not excessively tuned the engine with extreme boost or fuel; we have simply returned these parameters to values that disregard the Euro 2 standard.
For those seeking more power, consider adding a front-mount intercooler from the 1HD-FTE or a more powerful Safari intercooler for the 1HD-FT. The standard turbocharger, with its small 42mm compressor inducer, becomes a major restriction and should be replaced. A pre-facelift turbo from the FTE is a direct bolt-on upgrade. This must be accompanied by corresponding adjustments to the injection pump for increased fuel delivery. More details here:
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1HD-FTE turbo and intercooler installation on 1HD-FT
9. Advanced Tuning: Twinscroll Turbocharger System
A significant step forward is implementing a twinscroll turbocharger and corresponding exhaust manifold. This setup greatly improves engine efficiency, cylinder scavenging, lowers EGT, and enhances turbo response across the entire RPM range. This is particularly effective on inline-six engines, where the firing order allows for a relatively straightforward manifold modification. Safari Turbo Systems used this approach in some of their turbo kits for the 1HZ.
When switching to a twinscroll turbo, it is advisable to move away from the standard FTE air-to-air intercooler setup and adopt a more efficient air-to-water charge cooling system. The "cherry on top" is to separate the wastegate gas flow from the main twinscroll turbine flow, routing it through a dedicated downpipe and exhaust. This requires a custom turbine outlet and a separate exhaust section, significantly reducing backpressure and improving high-RPM breathing and EGT. As mentioned, the stock turbo's 42mm compressor inducer is a major "restrictor plate," limiting power to ~180-190 hp. Switching to an FTE turbo (46mm inducer) reduces this restriction, increases compressor trim and flow, and allows for 220-230 hp. Ideally, upgrade to a fully-machined (milled) 48/68 compressor wheel from a Celica, enabling the engine to breathe well at high RPM and produce up to 270-290 hp. For more, see:
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Another Twinscroll for 80-series 1HD-FT. This time CT26 Small from Celica 205
10. Enhanced Cooling for Tuned Engines
If you have installed an intercooler and an alternative turbo, significantly increasing power, it is crucial to upgrade the cooling system. Install a more robust viscous clutch and cooling fan from the 1HD-FTE. Details here:
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1HD-FTE viscous clutch and fan installation on FT
Also, use a high-quality carboxylate (OAT) antifreeze, such as BASF Glysantin G30.
11. Further Cooling and Oil System Improvements
Another consideration is replacing the oil pan with the larger unit from the newer heavy-duty 70-series. According to Toyota manuals, this pan holds 1.5 liters more oil (+15%), which benefits oil temperature and service life. However, its fitment on a non-lifted 80-series is yet to be fully confirmed. More here:
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Question about HZJ78-79 oil pan, part number 12101-17200
An alternative for increasing oil capacity is to replace the inadequate stock oil filter with a larger, cartridge-type truck filter. This adds roughly the same 1.5 liters of oil and offers numerous other advantages. Details here:
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Question about 1HD-FT oil system
12. Electrical System Optimization
A useful modification for prolonging battery life is installing a switch for the intake air heater mesh. The mesh draws up to 80A and can operate for 80-120 seconds
after engine start. This significantly drains the batteries, especially on short trips. On a well-maintained engine, the mesh is only beneficial as a pre-heater for cold starts below -20°C. Above this temperature, the engine starts perfectly without it. Post-start heating is another "environmental nonsense" feature that slightly improves combustion in a cold engine at the cost of slowly killing your batteries. More here:
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Is the intake air heater necessary for 1HD-FT engine?
Good luck and more torque to you,
Vadim Akopyan, aka VADUS
and greetings from Greece!