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In today’s video we will discuss rear mount / remote mount turbo setups, so engine in the front turbo in the back. We will analyze their benefits, their drawbacks, we will see if they are actually a stupid idea and along the way we will hopefully learn some important lessons and bust some turbocharging myths.

So let’s start by answering the most obvious question…why would someone want to mount a turbocharger far away from the engine? Usually the primary motivator for a remote mount turbo is space. Sometimes it is very difficult to find space for a turbocharger in the engine bay of a car that came naturally aspirated from the factory. And even when you can find the space you might require a one-off complex custom exhaust manifold if you’re working with a platform that doesn’t have sufficient aftermarket support or if you’re doing an engine swap. If you don’t have the fabrication equipment and skills such an exhaust manifold can become a very expensive item on your parts list.

And even if you find the space for the turbo the location might be less than ideal and require complex routing of the intake piping and exhaust downpiping which may negatively impact performance. On top fo this a turbocharger is a major source of heat and the space you find for it may negatively impact the components around the turbo leading to a reduced lifespan of these components.

A remote mount turbo is sort of a path of least resistance towards solving these problems. There almost always plenty of space somewhere along the underside of the car, even more so at the back so finding space for one or even two turbos here is not an issue. A remote turbo is also a one stone two birds affair because it eliminates heat problems. By locating the turbo away from the engine bay we save the engine from the added heat and we also help the turbo itself to run cooler. Companies and individuals who specialize in remote mount setups and have completed such projects usually report turbine side or hot side temperatures of the turbo to be lower by around 300 degrees celsius.

This is a pretty significant difference in temperature which helps the turbo last longer and makes cooling the turbo less important. In other words it becomes feasible to run a turbo that isn’t water cooled, instead it can be oil cooled only. This reduces cost and simplifies install. Of course, you can still definitely run a water-cooled turbo in a remote mount setup, there is no harm in even better turbo cooling.

But it gets even better. The remote location of the turbo doesn’t just save the engine bay from the added heat, it actually positively impacts performance. If a turbo runs cooler than it doesn’t heat the intake air as much. On top of this we have as much as a car’s length of intake piping that’s exposed to fresh air passing along it which means that the intake air gets cooled even more before it gets to the engine. Cooler air is denser and denser air means that we can stuff in more air mass into the same volume which means more power.

Now this cooling effect isn’t as significant as that of an intercooler so ditching the intercooler isn’t a smart idea in my opinion, instead this is added cooling simply further improves performance and helps prevent knock which means that, all else being equal, we can potentially run a higher compression ratio in the engine than with a turbo mounted near the engine.

So, it costs less because you don’t need a fancy exhaust manifold, it reduces heat and it improves performance. As you might be guessing things can’t be all good, there must be downsides.

The biggest downside of a rear mount turbo setup is that it allegedly leads to massive amounts of turbo lag. And apparently this occurs because now the turbo has to pressurize an entire car’s length of piping. This requires time and we experience this time delay as turbo lag or reduced responsiveness of the engine, in other words a car with a rear mounted turbo will feel lethargic and sluggish due to the crazy lag.

This is simply not true and I believe that this idea that a rear mounted turbo creates massive lag comes from a mis-understanding of how a turbo actually works and how it increases engine performance.

A special thank you to my patrons:
Daniel
Pepe
Brian Alvarez
Peter Della Flora
Dave Westwood
Joe C
Zwoa Meda Beda
Toma Marini
Cole Philips

00:00 Benefits
04:38 Turbo Lag
12:29 Boost Threshold
17:22 Oil return, noise, damage

#d4a #boostschool