All you need to know about rear-mounted turbo
A rear-mounted turbo is an efficient & cost-effective power boost alternative for your vehicle
So, if you have a car, an engine, and a spare turbocharger lying around? Then you have almost everything you need to install a rear-mount turbo setup. Though a single rear-mount turbo system may have problems delivering boost pressure at low RPM (a condition known as ‘turbo lag’), high RPM power is good with any engine-mounted turbo application.
If you just want an easy retrofit turbo option or have limited engine bay space, you’ll do well by considering a remote mount turbocharger. Usually, traditional turbochargers mount to the engine’s exhaust manifold under the hood, if there is space available, and it can cope with the heat.
This is where a remote-mount turbo or a rear-mounted turbo differs as it is fitted much further down the exhaust pipe. Most of the time, a rear-mounted turbo is installed at the rear of the vehicle just before the rear silencer.
Adding an aftermarket traditionally mounted turbocharger to a vehicle can be difficult, as many engine bays are cramped, and sometimes require modified hoods & other engine components. But, the rear-mounted turbo avoids this issue by mounting further down the exhaust underneath the car.
A rear-mounted turbo follows the same operational principles as a traditional turbocharger but is just further away from the engine bay. This keeps the temperatures in check as the exhaust dissipates much of the heat. Plus, the longer run means the boost levels are lower, and the spool rates are lower.
It also makes mapping the turbo easier & offers a pretty simple low boost turbo solution where engine bay space is limited. Also, the intake air is channeled back from the turbo compressor to the front & into the engine. Despite the long run, the delivery is practical and purposefully instantaneous, and if the pipework is in good condition, there will only be a minor loss in boost pressure.
How to Install a Rear-Mounted Turbo?
Engine and Turbo
Since Turbochargers can sometimes lag, or suffer from a condition known as Turbo Lag, a rear-mounted turbo system should ideally be applied to an engine no smaller than 4.0L. Torque-deficient, 4 cylinder engines get difficult & frustrating to drive if turbo-lag is too high. Also, it may require additional modifications to the gearing and drive-train to compensate. Some of the best deals on turbos come from diesel generators, over-the-road tractor-trailers, and agricultural machinery.
Apart from the turbo, a high-flowing single exhaust system is needed. Use mandrel bent pipes, and don’t go any longer than 3”. If the pipes are too long, it will reduce flow velocity & increase turbo-lag.
The single most expensive investment is oil pumps. And you’ll need two matching sets of pumps, one to pull oil from the turbo, and the other to send it back from the reservoir.
Further, to install a rear-mounted turbo kit, you’ll need to cut into the exhaust and direct the exhaust flow into the turbo intake. You may also need to get a heat shield, especially if the turbo is going to be mounted near the fuel tank. You’ll need to reroute the engine intake through the rear-mounted turbo, and we strongly recommend using good quality pipes, preferably metal.
However, high-quality silicone hoses can also work and are easier to fit. It means the air intake will be at the rear of your car to avoid the hot temperatures of the engine bay and a double run of pipe from the air filter to the turbo & back again.
Unless you opt for an oil-less turbo, it will need a supply of oil, either its pumped supply with a cooler or taking a feed from the engine oil. Next, you’ll need to adjust the fuelling & timing, a specialist job (you can call us for that).
A remap on a rolling road might be your only option if you don’t want your engine to blow up and want to extract the maximum amount of power from your mods. Injectors will also need to be updated, and many standard air filters will be unable to flow enough air where a turbo has been added.
More importantly, you will need to add safety systems as well. These safety systems would be detrimental to the turbo to keep the engine running if the turbo becomes too hot or somehow the oil line is cut.
Depending on your vehicle’s mapping, you may need to factor in some modifications to control the exhaust flow through the turbo. You may do this with a form of a wastegate control and a diverter valve to cut in when you come off the throttle to avoid over-boost.
If you are running high boost levels, you should probably reduce the engine’s compression ratio or introduce other measures against detonation like adding water injection & using higher octane fuel. Thankfully the rear-mounted turbo is relatively simple in its setup and tolerates a wide range of varying conditions compared to a conventional turbo.
After installing your rear-mounted turbo, you might need to fabricate a section of mandrel-bent tubing with a mounting flange for your turbocharger on one end. Apart from that, install or build a bracket to support the turbo from your car’s frame. This tubing is installed so that the turbo rests in a vertical position.
Mount the scavenge pump slightly below and as close to the turbo as possible. Connect the outlet line to your one-gallon trunk-mounted oil reservoir tank and the turbo drain line to the inlet side of this pump. Mount the second pump next to the reservoir & run a line from its output to the turbo oil inlet.
Run the aluminum tube from the engine’s mass air sensor or throttle body to the turbo compressor outlet. Use as many sections of rubber tubing as needed and keep the tubing as far away from suspension components and exhaust piping as you can. Install an oil-impregnated air filter onto your turbo compressor inlet. When this is done, remember to install a spring-loaded blow-off valve set to your desired pressure if you’re using a diesel turbo.
What are the advantages of a rear-mounted turbo?
Engines prefer denser, colder air to compress within the cylinders. Seeing as the traditional turbocharger increases the energy of the air by compressing it, the air exits the turbine in a boiling state, which is usually where an intercooler comes in. An intercooler is used to cool the intake air to the engine from a turbo system. You can see that heat is the enemy of all turbos, but the rear-mounted turbo housings are exposed to cool, flowing ambient air, helping them to remain cool and run more efficiently.
It is estimated that a rear-mounted turbocharger produces nearly 260 degrees centigrade less heat buildup than a front-mounted unit nestled in an engine bay. The temperature of a typical front-mounted turbo can reach 1100 degrees Celsius, while the rear-mounted setup commonly sees temperatures ranging from 650 to 700 degrees Celsius.
The huge amount of heat generated by a turbocharger can influence other components that don’t deal well with heat, like the engine cooling system and engine block. But, rear-mounting the turbocharger can take away all possible effects of heat soak from a turbocharger to unwanted areas.
The oil which circulates the turbine is used for lubrication along with cooling the system as the lack of fluid can spell disaster for your turbocharger. Moreover, the increased cooling effects are crucial for oil cooling, a very important aspect of reliable turbocharging. The massive flow of cold air under your car always helps in keeping the oil cool & keeping the turbocharger operating smoothly and this is the main advantage of a rear-mounted turbo.
More Reasons to go for a Rear-mount Turbocharger
- Ease of installation
- You don’t need major modifications to your vehicle
- Lower underhood temperatures
- No need for an expensive exhaust system
- Better overall system airflow
- Better weight distribution
- Cleaner look & more room under the hood
- Less noise and heat inside the vehicle
- Easier maintenance and room for other mods