Proton Iriz R5 rally car – 4B11 engine actually sourced from Proton Inspira, not Mitsubishi Lancer Evolution X

With the engineering of UK-based Mellors Elliot Motorsport (MEM) providing the support for various rally campaigns entered by the Proton Iriz R5 rally car, we’ve previously known the Malaysian B-segment hatchback to be powered by a version of the 4B11 engine that comes from the Mitsubishi Lancer Evolution X. As it turns out, the heart of this rally car originates closer to home in Malaysia.

This 4B11 engine that provides the basis for the powertrain in the Iriz R5 rally car is actually sourced from Shah Alam, pulled from the Proton Inspira. The engine’s rather more mainstream origins compared to the Lancer Evolution matters little, as only the engine block and head area used, with competition-grade products used for parts such as the pistons, connecting rods, crankshaft, camshafts, cylinder sleeves, turbocharger and the like.

To comply with R5-class technical regulations, the engine has to be capacity-reduced to 1.6 litres from its original 2.0 litre displacement. Why not use the Campro S4PH engine, which already displaces the correct 1.6 litre capacity in the production Iriz?

There are several factors, according to MEM founder Chris Mellors, and they are mostly to do with fitment. In the case of the S4PH Campro engine block, its exhaust valves and ports which face the front of the car. Due to packaging constraints, this would require the turbocharger plumbing to be fitted in front of the engine as well.

This, in turn, would require a more substantial and complicated exhaust routing that would need to go around the gearbox before carrying on rearwards to the back end of the car. As the Iriz R5 transmission also comprises of a transfer case to send drive to the rear wheels, the driveline hardware altogether takes up more space than it would in a simpler FWD layout. To further complicate matters, rally car engines are typically reclined 25 degrees rearwards to help attain a more balanced distribution of weight.

Using the 4B11 engine block is ideal, then, as its rearward facing exhaust ports allow the use of simpler, shorter and therefore lighter exhaust manifold design. The packaging advantages afforded by this layout also benefits performance, as the rearward exhaust routing channels away the gases more directly without having go around the engine as if the exhaust ports were in front, which helps the engine run cooler.

In line with R5 class regulations, the 4B11 engine in the Iriz R5 is fitted with a 32 mm restrictor on its turbocharger, which caps maximum output in the region of 350 hp and 450 Nm of torque. The Iriz R5 transmits these outputs to all four wheels through an Xtrac five-speed sequential gearbox.

Mellors Elliot Motorsport released a brochure for the Iriz R5 last year, that was comprised of a parts list, along with options packs and an estimate of running costs. The rally car starts from GBP140,000 (RM776,000) in base specification, and arrives in tarmac trim (GBP23,500/RM130,222 if purchased separately). The gravel kit is priced at GBP19,900 (RM110,397).

Rally cars in the R5 category are versatile, as they can be eligible for the European Rally Championship (ERC) and WRC qualifying rounds such as the British Rally Championship (BRC). Here at paultan.org, we’ve followed the development of the MEM-built Iriz R5 with interest, and we got to discover some interesting facts pertaining to the background of the rally car.

This has been translated from the original story written by our BM counterpart.

GALLERY: Proton Iriz R5 brochure

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