Mitsubishi 4G94: Everything You Need To Know

4G94 engine belongs to the Mitsubishi 4G9 series. These engines are built in Japan and were launched in the Mitsubishi Lancer. 4G94 engines along with 4G91, 4G92, and 4G93 are inline-4 engines that use both the SOHC and DOHC 16-valve camshaft heads. Some 4G engines feature MIVEC variable valve timing. It has four displacements in the family with 1.5, 1.6, 1.8, and 2.0 L. So today, we will take a deeper emphasis look at the largest 4G engine made by Mitsubishi Motors. Its variants, the difference of each variant, and how they affect the course of the engine direction of the following years to come.

Engine Specifications and Design:

  • Production Run: 2000 – 2010
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Cast-Iron
  • Configuration: Inline-4
  • Bore: 81.5 mm
  • Stroke: 95.8 mm
  • Valvetrain: SOHC and DOHC 4 Valves Per Cylinder
  • Displacement: 2.0 L
  • Compression Ratio: 9.5 and 11.0
  • Weight: 330 lbs.
  • Max HP: 145 HP at 5,700 RPM
  • Max Torque: 141 lb-ft at 3,750 RPM

4G94 engine design is based on the 4G93 engine, but it is more extensive, and it is, by fact, the largest engine in the 4G9 family. One of its adopted components from the 4G93 engine is the cast-iron cylinder block with multi-point fuel injection. It has a higher deck height of 231.mm and an increased bore from 81 mm to 81.5 mm. Inside, we can see that Mitsubishi installed a 95.8 mm stroke crankshaft, 152.9 mm forged steel connecting rods, 30.4 mm compression height, and 81.5 mm pistons. 4G94 can displace 2.0 Liters.

4G94 comes with two-cylinder head variants: the aluminum SOHC MPI head, which has 32 mm intake valves and 29 mm for exhaust valves, and a DOHC head variant which used GDIs (Gasoline Direct Injection) instead of MPIs and appeared in Mitsubishi Galant; both have four valves per cylinder, 240 cc injectors, and 52 mm throttle body size.

4G94 SOHC 16 Valve MPI

  • Multi-Point Injection
  • 81.5 mm bore
  • 95.8 mm stroke
  • Compression Ratio – 9.5
  • Maximum Output – 123 HP at 5,200 RPM
  • Maximum Torque – 130 lb-ft at 4,250 RPM

4G94 DOHC 16 Valve GDI

  • Gasoline Direct Injection
  • 81.5 mm bore
  • 95.8 mm stroke
  • Compression Ratio – 11.0
  • Maximum Output – 144 HP at 5,700 RPM
  • Maximum Torque – 141 lb-ft at 3,750 RPM

Applications:

  • Mitsubishi Pajero iO
  • Mitsubishi Pajero Pinin
  • Mitsubishi Shogun Pinin
  • Mitsubishi Montero iO
  • Mitsubishi Pajero TR4
  • Mitsubishi Lancer
  • Mitsubishi Galant
  • Hawtai Santa Fe

Engine Tuning, Upgrades, and Modifications

The primary thing to consider when tuning your 4G94 engine is that you need to buy and install a MIVEC head. To convert your SOHC to DOHC head, you will need, of course, a 4G92 MIVEC head together with its entire intake and exhaust systems. You will also need to buy 4G92 pistons, ACL main and rod bearings, MIVEC ignition and fuel systems, 4G93E oil pump, head gasket, head bolts, 4G92 harnesses, and a 7M-GTE timing belt. In this setup, you can get a 200 HP. If you are not yet satisfied and you want to add more power, you need to do some head porting and polish the MIVEC head, throw in some performance parts like a cold air intake system, 4-1 header, Evo throttle valve, JUN type 1 camshafts, a 2.25-inch exhaust system, and a stand-alone ECU. Good thing that 4G94 can withstand these upgrades and does not need high compression pistons. Once you’ve already configured these upgrades, it can give you 230-240 HP.

MIVEC Turbo

Another option from the bag to add power to your 4G94 engine is the forced induction. But even using a Mitsubishi TD05H-16G turbocharger, it has low boosting pressure. This setup can still amount to the same 200 – 250 horsepower result due to the weak stock internals of the 4G94 engine. If you want to add more power, you will need a powerful engine. In order for you to do this, the stock pistons and rods should be replaced with K1 rods and forged pistons with a compression ratio of approximately 9.1. This engine also needs forged internals like ACL bearings, oil cooler, ARP head studs, which can give you more than 200 HP. For the turbo, you need performance parts for this setup like turbo manifold for the Evo turbocharger, large intercooler and pipes, NGK spark plugs, Evo throttle body, fuel pump. AEM fuel rail, 630 cc fuel injectors, Aeromotive fuel pressure regulator, 272 cam, valve springs, 2.5-inch exhaust system, boost controller, and a stand-alone ECU, just like we mentioned above. This can result in at least 300 HP in your pocket.

Common Problems

4G94 engines are almost the same as the 4G93s, so they most likely share some common problems. And as much as we wanted to keep the pristine condition of our engine, It cannot be avoided, and we should understand that there would be wear and tear if there are any moving parts. So some preventive measures and precautions might come in handy like this.

The first is excessive oil consumption. We all know that excessive oil consumption corresponds to loose components and not tightly fitted internal parts. This is due to the engine’s age, and the total mileage traveled throughout its service life. The wear and tear expedite the process, and if you use poor engine quality, it will be more detrimental for your engine. It can also be caused by some leak and improper maintenance methods to your engine. However, this issue can be solved by either replacing the piston rings and valve stem seals or disassembling the engine if it needs overhauling. Most of the time, it is the latter.

Next is the knocking sound in the engine. Usually, the knocking sounds are caused by poor engine quality. You might ask why. Inferior engine oils become thick and dense through time. This results in a non-lubricating medium; they don’t do well in extreme conditions, especially inside a hot engine and different temperatures and cycles. This targets the hydraulic lifters, and it just needs replacements for this to solve.

Another thing is the rough idling. Idling problems occur when you have inconsistent fuel combustion in the chamber that causes some hiccups or idles, which are prevalent on GDI engines. Several factors that may be causing this issue are that you have a dirty throttle body, a clogged high-pressure pump, spark plugs, and spark plug wires. These guys just need some thorough cleaning, and it might solve it. If this is not the reason, check the idle air control valve. It might need replacement also.

On top of those, GDI engines have EGR valve issues also. EGRs are the link that connects the exhaust manifold to the intake manifold and controls the flow of exhaust gases that is being recirculated on the engine. A clogged intake manifold might be the reason for this. Also, the 4G92 engine uses a timing belt instead of chains, and it needs replacement every 60,000 miles to prevent breakage because timing belt breakage leads to valve bending.

Summary

4G94s are incredibly reliable engines that can surpass the 200,000-mile mark. It is the largest engine in the 4G9 family that displaces 2.0 L. Even it is not the most powerful engine made, and it has a respectable reputation to go over and beyond our expectations. Even though it has some minor issues that might cause trouble and headache for some time, we cannot agree more that with the correct maintenance, high-quality engine oil, and proper management of the necessary component replacement, this engine will be a lifetime worth of service to you.

With that, I hope that the things that we discussed here gave you a clear idea about how the 4G94 engine works, its design, tuning, maintenance, and its overall impact on the automotive community. May this be a little guide for you to understand it even more whether you are buying or already owned one. Stay tuned!

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