2020 Proton X50 has 2 turbo engines – one direct injection, one port, what’s the difference?

Hans · Sep 15, 2020 05:45 PM

As you would’ve know by now, the 2020 Proton X50, which is manufactured in Tanjung Malim, is offered in two engine options. Both are DOHC 1.5-litre turbocharged units but the fuel system is different, the 1.5T MPI engine uses port injection while the 1.5 TGDI uses direct injection.

The three cylinder direct injection unit (1.5 TGDI, codename JLH-3G15TD) makes 177 PS at 5,500 rpm and 255 Nm 1,500 – 4,000 rpm while the port injection (Proton calls it Multi Point Injection, MPI) 1.5T MPI makes 150 PS and 226 Nm - no details on engine’s rotational speed yet.

The former is also used in the Volvo XC 40 T3 (not available here) but contrary to popular opinion, that's not a Volvo engine, and it's built by Geely, not Volvo. The reasons behind it have been explained here.

The 1.5T MPI is a new development by Geely, and is not sold in China. Malaysia is the first market to launch this new engine. Details are still unclear (today’s announcement by Proton is just a preview) but we believe that this is a four-cylinder engine, an enlarged version of Geely’s 1.4T MPI unit (codename JLB-4G14T) used by the Geely Binyue Pro. The engine makes 133 PS at 5,200 rpm and 215 Nm at 2,000 – 4,000 rpm,

Is the 4G15T 1.5 T MPI engine an enlarged version of this 4-cylindere 4G14T?

We suspect that since Malaysia has no CO2 emissions tax, Geely has greater freedom to offer a more powerful, slightly larger capacity version of that engine, raising outputs to 150 PS and 226 Nm.

Correction: Proton has since confirmed that the 1.5T MPI engine is a 3-cylinder, and is not related to the Geely Binyue Pro's 4G14T engine.

Nothing to see here, move along

However, since it uses port injection, output is still a lot lower than the direct injection 1.5 TGDI engine (177 PS and 255 Nm), despite the latter having one less cylinder.

So what is the difference between port injection and direct injection?

Port injection

In the context of modern vehicles, the conventional fuel injection is port injection, also known as multipoint injection. In this setup, fuel is injected into the intake port to be mixed with air before entering the combustion chamber, where spark will ignite the mix.

Gasoline direct injection

Direct injection is a more sophisticated, and of course more expensive setup. In this method, fuel is injected directly into the combustion chamber at very high pressure – up to 350 bar. Of  course, all modern diesel vehicle engines run on direct injection so it's nothing new but in this context, we are talking about direct injection for petrol engines. 

Without going into too many technical details, direct injection improves fuel efficiency and power output.

In port injection, some residual fuel will remain in the intake port. With direct injection, fuel is atomized immediately as it enters the combustion chamber, minimizing wastage.

Since fuel has a cooling effect, direct injection allows engines to run at higher compression ratios, with in turn increases power output and torque.

However not all is good for direct injection. Direct injection engines are more sensitive to variations in fuel quality. And since the fuel no longer passes through the intake ports, the cleaning properties of fuel additives can no longer work on the intake valves and overtime, carbon deposits will build up, requiring more complex maintenance work.

Also, direct injection engines sound harsher, and some exhibit a diesel-like clatter at idle.

Toyota's D4-S combines both port and direct injection

This is why some manufacturers combine both port and direct injection systems into their engines, but that’s an even more complex setup. Toyota’s D4-S system is one such example.

As this is just a preview, we have yet to sample the Proton X50 on local roads. The model is expected to be launched sometime in October. Although it's based on China's Geely Binyue, our local Proton X50 boasts of a few unique features that are not available in the Geely donor car.