1HD-T Performance and Tuning Guide
This guide will provide clear information on upgrading your 1HD-T engine’s performance and what parts we would recommend. As with any popular engine to be upgraded, we have curated this article this in response to the high volume of questions we get on a weekly basis. Our recommendations and advice is based on our experience successfully supplying performance parts to Toyota Landcruiser customers all around the world, carrying out these performance upgrades in house at our workshop in Brisbane, and polishing things off with dyno testing.
The 1HD-T has earned a pretty good name over the years. From day one, it was a proud statement for a customer to drop us a hint that they’ve got a ‘factory turbo 80 Series’. With all their glory, it’s still important to know the strengths and weaknesses.
While the 1HD-T engine may not have the seemingly endless tuning potential of its big brother, the multivalve 1HD-FT/E, they are a much loved engine by 4×4 enthusiasts for their rugged simplicity and reliability in the 80 Series Toyota Landcruiser. In turn there are less parts to upgrade and this article is a bit shorter and more condensed. We have a bolt on solution for all of the parts and there is no custom work required, when used in conjunction with each other.
1HD-T Basic Specs:
- 6 cylinder, 4.2L DI diesel engine produced by Toyota from 1990-1994 in the 80 Series Landcruiser.
- ‘Single valve’ cylinder head. It has 12 Valves in total, one per cylinder for intake and exhaust.
- Direct Injection Engine, The injectors fire directly into the pistons combustion bowl.
- Factory ’12mm’ fuel pump. Yes, they come with a ’12mm’ fuel pump from factory. Not to be confused with a 12MM upgrade for common engines such as the 1HZ and TD42.
- Boost compensated injection pump.
- Factory CT26 turbocharger runs 8PSI of boost. Non intercooled.
- Crankshaft 1HD-T shares the same crankshaft as a 1HZ and 1HD-FT.
To make it even more convenient, all the parts are listed together, here:
https://hdautomotive.com.au/product/ufi-turbo-upgrade-kit-suitable-for-1hd-t-80-series-landcruiser/
Diesel Performance:
There’s a common misconception with new owners to diesel engines, especially coming from a petrol performance background, that simply upgrading a turbo or exhaust will increase the power. However, what is often misunderstood is that this must be done in conjunction with tuning the mechanical injector pump, to increase it’s output.
Power expectations:
Stock ~110hp:
The HDJ80 produces around 100HP and 280NM on our Mainline Dyno in it’s factory turbo, non intercooled form.
Turbo upgrade kit ~150hp:
Using these bolt on parts to increase airflow, the injector pump can be tuned to 150+HP / 450NM+
They usually comfortably land around the 170HP and 500NM mark in this configuration.
- Turbocharger upgrade
- Front mount intercooler
- Heavy Duty clutch upgrade
- 3″ Exhaust
Notes: The stock air box is suitable for this level of power upgrade, but there is no disadvantage to having an upgrade.
Further upgrades 200HP+
With an upgraded fuel pump, the engine can be tuned up to a maximum of 230HP / 680NM Using these bolt on parts!
We recommended a maximum target horsepower of 200HP and 600NM for the 1HD-T engine.
- – Turbocharger upgrade
- – Front mount intercooler
- – High flow airbox
- – Heavy Duty clutch upgrade (NPC 1300NM Recommended)
- – 3″ Exhaust
- – Performance injector pump upgrade
A quick note on injectors – there is no need to ‘upgrade’ the injectors at any power level a 1HD-T is capable of producing. There is no shortage of fuel available on the factory injectors, and the limitation on power is elsewhere on these engines, which we will provide more info on fuel system below.
Parts breakdown:
Turbocharger upgrades
If you are looking for no more than 170HP, my first recommendation would be the UFI 16G. This turbo will provide even better than factory boost response, while delivering a huge improvement in airflow up top. This is my pick of choice if you just want to replace your turbo with a better one, but aren’t looking to make huge power numbers.
UFI 18G is the perfect performance upgrade option for a 1HD-T, it’s still extremely responsive and can handle over 250HP, beyond what we know a 1HD-T engine can make. That means you can’t go wrong with it as a performance upgrade, with the potential to upgrade injector pump down the track without buying another turbo.
The 4″ Anti-surge inlet produces the truck-like whistle that sounds great on the HD-T engine.
The factory CT26 Turbo is renowned for snapping the shaft over 14PSI, we want to increase the boost beyond that, so a Turbo upgrade is absolutely necessary.
-All of the turbochargers we supply are ‘CT26’ Based, that means they bolt onto a standard manifold and standard Landcruiser parts.
-Water lines are not used on the UFI turbochargers.
Boost Controller: Boost control is a one-way street on a gated turbocharger, the Turbosmart Boost Tee allows boost level to be raised easily.
eg: The UFI Turbo has an 18PSI waste gate, by installing an adjustable boost tee, we can raise that up to target 25-26PSI increasing airflow.
https://hdautomotive.com.au/product/1hd-ft-boost-controller-kit/
Turbo Manifold?
The factory low mount turbo manifold works perfectly and there is no noticeable power increase using a high mount turbo manifold at these horsepower levels. A high mount manifold is essentially done for the look, it only adds complexity cost into the picture. Due to the complete lack of quality (genuine merge collector) high mount manifold designs on the market, you will likely loose boost response, horsepower and torque by changing this.
Should I use a top mount or front mount intercooler?
Front mount intercoolers are always the best option, they consistently outperform every other option – they don’t suffer heat soak and any affect on the radiator is offset by providing much cooler air into the engine.
We don’t see any disadvantage for off road use, any mud that ends up on the core can be easily washed out. They also won’t suffer vibration cracking like aftermarket top mounts do. If it wasn’t going to clog up in your intercooler, then it’d be clogging up in your radiator… so you pick what’s easier to clean.
BOLT ON: PDI Intercoolers have a complete bolt on intercooler kit for the 80 series. It costs $1750
https://hdautomotive.com.au/product/pdi-80-series-front-mount-intercooler-kit-toyota-landcruiser-80-series/
BUDGET / DIY: HD Auto intercooler kit with brackets and a 600x300x76 intercooler for $430. The bar & plate core works great and you can save money fabricating your own pipe work.
https://hdautomotive.com.au/product/80-series-intercooler-bracket-kit/
Heavy Duty Clutch Options
The 1HD-T has a factory 300MM diameter flywheel. The factory clutch will let it down and slip shortly with increased power levels, so an upgrade is required. All of these clutch kits come with a new spigot & throw-out bearing for install.
Exedy 6874HD $789
Budget friendly and high quality. The Exedy HD clutch is suitable for mild upgrades up to 500NM.
https://hdautomotive.com.au/product/exedy-6874hd-heavy-duty-clutch-kit-toyota-landcruiser-hdj80/
NPC 6874-1A $985
Rated at 800NM. This NPC clutch can be used on your factory flywheel, just have it machined for a fresh surface. These are a great option that will suit most owners.
https://hdautomotive.com.au/product/hdj80-npc-heavy-duty-clutch-kit/
NPC 6874-1D $1820
NPC Super Heavy Duty. This Kit has an upgraded pressure plate rated at 1300NM, it requires the NPC Billet flywheel upgrade which is included. Suitable for heavy duty abuse and towing.
https://hdautomotive.com.au/product/npc6874-1d/
About NPC: NPC are an Australian company, with many years of experience supplying uprated clutches for the Landcruiser market. They have a clever process of modifying Exedy clutch kits, and combining them with custom flywheels for ‘Super heavy duty’ clutches with factory pedal feel.
High Flow Airbox / Snorkel
The high flow airbox further contributes to increasing airflow and achieving a ‘safe AFR’. The factory style airbox can become restrictive over 180HP so an upgrade is recommended. Same for the snorkel, an upgrade will help with air flow. The old style Safari plastic snorkels will juuuust work up to about 180HP, after that you might have to consider a 4″ forward or rear facing stainless snorkel.
We recommend using dry, synthetic type high flow filters like in the PDI Airbox, over the washable / oiled air filters. If too much oil is applied they restrict air flow and cause a mess in the intake.
The PDI airbox uses a VDJ200 Panel Air Filter.
https://hdautomotive.com.au/product/pdi-80-series-airbox/
Fuel System / Tuning info:
Why we upgrade the fuel pump, even though it’s a factory ’12MM’
Let’s say best case scenario you have a sub genuine 100,000km 1HD-T engine (unlikely). It’s still 30+ years old.
When you increase the fuel delivery of the injection pump, you are asking that pump to do a lot more work than it was initially calibrated to do. This causes a common issue seen in standard (or most rebuilt) 1HD-T pumps to begin to hunt the idle, and rev hang on gear change.
This is because it’s simply being asked to operate in a way it was not intended to. The factory Denso boost compensator setup has extremely limited travel in it’s pin and was only really setup to handle max 12PSI, so it’s becomes kind of a disaster. Because there is no load control, timing control, or fuel control left in the standard pump when it’s maxed out, you end up with a sooty mess of a setup, and makes driving around very tiring worrying about how much soot you’re making.
12MM ‘Mod Top’ Injector Pump
Wanting to increase the power beyond what a factory pump can provide? The injector pump upgrade is next.
https://hdautomotive.com.au/product/1hd-t-12mm-performance-injector-pump/
-When having an injector pump built, its important to have it done by a performance shop and built to your horsepower goal. There are many diesel pump rooms who simply don’t understand the performance industry, but will sell you a ‘rebuilt pump’ that has just standard internals and a higher fuel setting. There is a HUGE difference between a rebuilt pump and a performance pump.
Important note on injector pump install and timing: When rebuilding the 1HD-T engine, the timing gears must be set with the injector pump bolted in as per factory manual. If the gears are timed without the pump, there is a 100% chance of damaging the injector pump.
1HD-T Injectors:
-There is just no need to ‘upgrade’ the injectors at any power level a 1HD-T is capable of producing. There is no shortage of fuel available on the factory injectors, we recommend standard injectors in combination with an injector pump upgrade.
-Old, worn injectors may have a poor spray pattern & will contribute to loss of power.
-We have brand new injectors in stock, alternatively yours can be sent in for reconditioning.
https://hdautomotive.com.au/product/denso-1hd-t-hdj80-series-injectors/
Radiator upgrade?
The Factory radiator and it’s fan are well designed and perfectly fine, they will perform and last better than anything else. Turbo & intercooler upgrades are important because a safe AFR will keep the temp down on a tuned Landcruiser.
We don’t recommend thick core aluminum radiator’s on 4wd as they are severely prone to cracking on corrugated roads.
Exhaust?
-A 3 inch exhaust will have enough flow to handle all the power you can make on your 1HD-T engine, it is recommended to increase flow and responsiveness with your turbo upgrade. It also unlocks the famous Toyota straight-six sound.
-There is no performance difference between Stainless Steel or Mild Steel, just look & longevity. It is reasonable to expect a mild steel exhaust to last 3+ years and Manta warranty their Stainless systems for 10 years.
The Manta 80 Series exhaust, has options for quiet, medium, loud and starts around $1300.
https://hdautomotive.com.au/product/80-series-intercooler-bracket-kit/
Engine Internals / Limitations:
Let’s discuss some major flaws of the 1HD-T engine so you know where your limiting factors are, and where to watch out for during maintenance.
Big End Bearings
Most 1HD-T engines are coming up to 30 years old now. If they have not been rebuilt once already, they may be already on their way to a second rebuild. This is because of a known factory fault with the engine bearings Toyota fitted to the original 1HD-T engines. They were reaching around 80,000-100,000km and ‘spinning’, causing a knocking noise from the bottom end of the engine. This caused Toyota to recall these affected bearings and fit new bearings to them, essentially increasing their life span. But, it did not fix the root cause of the issue.
Toyota revised the piston design of the 1HD-T during it’s production period, and I personally believe this had something to do with these big end bearing failures. By first exploring the piston design, you will notice it has an offset combustion bowl in the piston. This is unusual, as most direct injection diesels have it in the centre (like the 1HD-FT, and FTE). This was done because the injectors enter from the side of the cylinder head, not from the vertical top down position such as the 24 valve FT. I believe that when the engine reaches it’s peak injection period, creating maximum cylinder pressure, this offset bowl in the piston unequally transfers harmonics/pressure through the connecting rod dispersing oil away from it’s vital protective layer in between the conrod, and crankshaft. By no means do I believe it is completely washing it away, but I think this repeated cycle thousands and thousands of times over gradually causes the bearing to make material contact with the crankshaft or connecting rod, causing it to eventually create a rough surface on the bearing, enough to grab onto something, and unfortunately destroy the engine giving it that ‘knock’ none of us ever want to hear.
The best practice for maximising the longevity of your 1HD-T engine is to replace your standard bearings with ACL Race series bearings, then replace them every 100,000kms as preventative maintenance. ACL redesign their bearings with a blend of materials to increase strength and failure resistance, making them a better choice than factory. For only about $140, rod bearings are cheap by comparison.
This issue of cylinder pressure leads me onto the next biggest flaw..
The Cylinder Head
If I had a dollar for every ‘rebuilt’ 1HD-T I tuned in our first 5 years of my business that pushed coolant on the dyno, I probably wouldn’t even have to write this article. There is a serious lack of understanding in what causes the 1HD-T engine to be such a dog when it comes to sealing the cylinder head to the block. I’ve physically watched world class engine builders immaculately measure, bore, re-measure, fit, deck, check for straightness, deck again, measure piston protrusion, assemble each component to the nano millimetre perfectly, all go together and start pushing water 1000km’s later with no rhyme or reason why. No overheating, no big horsepower, NO reason anyone can find. Genuine parts used, brand new blocks used, brand new cylinder heads, nearly every combination. I’ve watched this happen between 20+ different engine shops. I did initially blame them, now I don’t. So, just be weary. This is why we encourage the limit to be 200HP and 600nm. We find the sort of boost that allows a good running engine to make this kind of power will last. Beyond that they just become a bit of a time bomb.
Airflow
While on the topic of cylinder heads, there seems to be a limiting factor inside the cylinder head and the way it swirls air into the cylinder that severely restricts it from making horsepower over 240HP. It just seems like the number no one can really crack, irrespective to the size of the fuel system or turbo. I have also seen cylinder heads ported to within an inch of their life to no real benefit here either, so just something to be aware of. These engines are not capable of producing 250HP+. A 1HZ can, but they have a different piston, head and injection system, which is what leads me to my conclusion.
Summary
Keeping the above information in mind, the key to successfully upgrading your 1HD-T engines performance is using simple bolt on upgrades and keeping it’s limitations in mind. Armed with that information we’re sure you will enjoy your 80 Series Landcruiser for many years to come.
