Updated: Oct 15, 2021
LS vs TD5 / 300TDI, LS vs Cummins R2.8, LS vs diesel VW, BMW, Mercedes Benz, GM Duramax
A lot of times when people are contemplating an LS swap, they also are considering its cousin – the diesel swap. In this post, I am going to walk through the different diesel swaps on a surface level as compared to the LS swap. Keep in mind I am not a diesel expert, but I do have knowledge on engine swaps and what it takes to do one in the Discovery 2 platform.
To start, I generally want to mention that a diesel swap will, more than likely, be more expensive than an LS swap, and probably by at least 1.5 to 2 times. Diesel parts are also less common than LS parts in the US. Importing diesel engines is quite expensive and parts are generally rare. That being said, some general advantages of diesels are fuel economy and lots of torque at low RPM.
Land Rover Diesels: TD5 and 300TDI
From the factory the Discovery 2 came with the TD5 5-cylinder diesel in Europe, which was, in turn, developed from the 4-cylinder 300TDI. The TD5 is an electronically-controlled engine that works with the Discovery 2's electronic automatic transmission. To do a TD5 swap into a formerly V8 Discovery 2, you really need all the parts – the TD5 engine, engine control module, electronic throttle pedal, transmission control module, bellhousing, and the wiring harnesses. The engines frequently came with manuals in Europe, so swapping that along with the engine is an option as well. From what I understand, as long as you have an entire European donor car and someone that knows what they are doing to strip it for you. Welding is required to change the V8 motor mounts to the TD5 motor mounts. The TD5 is fairly reliable and can be tuned to make more power. This, however, ends up being an expensive option given the amount of imported parts required and the time involved in replacing not only the engine, but a significant number of wiring harnesses and ECUs.
The 300TDI is a mechanically-controlled engine. This engine came stock in the Discovery 1 in Europe. They can be built to make a significant amount of power over stock. It can be used with the automatic transmission, however since the 300TDI lacks engine electronics, either a hydraulic valve body ZF or aftermarket computer would have to be used to control the stock transmission. Most conversions I have heard of with the 300TDI do not retain the traction control / ABS / hill descent control.
Both engines are not common in the U.S. and have to be imported, making them more expensive. Parts are also not common stateside. For those reasons, I would suggest that other options are better overall for those in the U.S.
Cummins Diesels: 4BT, 6BT, and R2.8
Cummins has been in the diesel game for a long time. They have made some great diesel engines. The 6BT and derived 4BT have been used in many, many different applications from trucks to vans. They both very reliable and can make a large amount of power. There are a couple of issues: the 6BT is huge and would be hard to fit in a Discovery. The 4BT weighs over 700 pounds, almost double the factory Rover V8. That much weight I think rules out the 4BT for use in the Discovery without major modifications.
Now, the new kid on the block is the R2.8. Cummins built an engine specifically for retrofitting in older vehicles. The engine is sold as a package with the ECM and wiring harness and it weighs about 300 pounds less than the 4BT. The good news is that I know that the engine could be used with the factory Discovery ZF electronic automatic and our electronics could keep all the factory traction control and other features operational. The down side is that the R2.8 is expensive – for a similar price you are getting close to a factory crate LS3 engine package from GM. I just wish that the R2.8 had a little bit more power and was a little bit cheaper – then I think would be an actual competitor the LS. Currently, however, the price-to-performance ratio just isn't that good. I've also heard about some issues with reliability. Hopefully R2.8 prices continue to come down in the future, which may make it a more attractive option.
Other Diesels: VW, Mercedes-Benz, BMW, and GM Baby Duramax
There are loads of other diesel engines. The downside is that they are not as common in the US. VW has an entire series of diesel engines that have powered cars since the 90s. These engines have a sizeable aftermarket and are reliable. They are also cheap and widely available at junkyards. Tuning is popular and can easily get more power out of an engine without component upgrades. Turbo and exhaust upgrades can get additional power. However, most VW TDIs were designed for a transverse mounted applications. This would require a significant amount of engineering work to get this to fit in the longitudinally-oriented Discovery. Specific issues regarding oil pan clearance and the accessory drive fitment would have to be solved. Current control systems would also allow us to retain the ZF 4HP22 and 4HP24 with these engines. Unfortunately, the larger VW V6 diesels are probably a bit big to easily fit between the Discovery's frame rails.
Mercedes-Benz and BMW also had some diesel engines that were used in the US. BMW diesel engines were even used in some Land Rover models in Europe when BMW owned Land Rover and shortly after. The problem with the Mercedes-Benz and BMW diesels in the US is that they just aren't that common. Engines, like the Mercedes-Benz OM605 and OM606 and BMW M57, are common in Europe, but they just weren't that common here. So while they are great engines, parts are not exactly common, and the engines are generally expensive to acquire. The Mercedes-Benz straight 6 diesels are getting old at this point. The BMW M57 specifically has a lot of aftermarket support in Europe and if you could find one, it probably would make a good swap candidate. The M57 swap would likely also require bringing along its associated ZF 6HP transmission, making the swap quite a bit more expensive.
The interesting twist on diesels in my opinion are new the GM diesel engines aimed at the small truck market – like the Chevy Colorado diesel and GMC Canyon diesel. This small 2.8L diesel I think would be a great engine for the Discovery and has the benefits of being a GM product – so there is likely going to be more aftermarket support here. Parts should also be easier to find. However, these engines are not cheap to find now. Furthermore, GM cancelled the 2.8L diesel in 2020, so they are going to be a short production run. For these reasons, the 2.8L diesel is probably just not going to be common enough to swap, which is unfortunate. The bigger diesel offerings from GM and Ford are just not a logical swap for a Discovery – they are just too big and too heavy.
Overall, I think there is some potential for Discovery diesel swaps in the future. However, basically all of them are going to be more expensive and complex than an LS swap using one of our swap kits (probably two times over at least). Most people would probably find an LS swap a better candidate to meet their driving needs for a couple reasons. First, many diesels are harder to find parts for generally than an LS. Furthermore, any gas mileage difference between the LS and diesel would probably not be made up for a long time. Second, I also think the LS makes for a better driving package overall with the linear V8 power. That being said, if you just simply must have a diesel in your Disco, then hopefully this article gave you some ideas – and feel free to give us a shout. I've always wondered about playing with one in the future.