Engine
Basic information
The 8th generation VR4 uses the Mitsubish 6A13TT (Twin Turbo) engine which is part of the 6A1 engine family, with the 6A13 being the largest displacement in this family, at 2.5 litres. The 6A13 came in a few configurations, with both SOHC and DOHC non-turbo variants; however, we focus only on the 6A13TT found in the VR4.
| Item | Details | Notes |
|---|---|---|
| Configuration | V6, 60 degree separation | |
| Displacement | 2.5L | Slight increases in stroke are possible via crank regrinds (up to 2.7L) but are as-yet uncommon. |
| Cylinder Bore | 81mm | |
| Cylinder Stroke | 80.8mm | For stock camshaft. |
| Block | Cast iron | The block uses a closed-deck design which was common in the 1990s. The stock block can support north of 350kw at the wheels.
No power limit to the stock block has yet been found, but one will exist and only come to light once these power levels have been obtained by the community. |
| Heads | Aluminium Dual Overhead Cam (DOHC) | The 6A13TT does not use variable cam timing. Some investigation has been made into converting 6A12 MIVEC heads to suit, without success so far. |
| Compression Ratio | 8.5:1 | |
| Turbochargers | Mitsubishi TD03-7T | |
| Peak Power (stock) | 206kw | Some sub-variants have slightly lower power |
| Peak Torque | 367Nm | Some sub-variants have slightly lower torque |
Common Issues and Limitations
Valve train noise
The 6A13 shares the same valve lash adjuster design with the 4G63 as used in the Lancer Evolution and can suffer from "lifter tick" due to clogged oil passages in the lifters. Noisy lifters can be solved by replacing the stock lifters with newer units that have larger openings to reduce the risk of blocked oil passages.
IFS Failure
The Ignition Failure Sensor is known to fail. Refer to the Ignition Failure Sensor page on the Wiki for advice on managing this issue.
Torque limit
Tuning which increases torque beyond about 420Nm brings risk of stretching the stock head bolts (lifting heads allowing combustion gases to enter the cooling system) or bending the stock connecting rods. At a minimum, head bolts must be replaced with stronger aftermarket bolts. Beyond 450Nm of torque, the motor will require forged connecting rods and pistons in order to last.
Modifications
Details of modifications are provided separately on the Wiki, but the most common modifications are stated here as a summary.
| Modification | Details | When Required |
|---|---|---|
| 3-port wastegate solenoid | The stock wastegate actuator solenoid is a two-port design. At higher boost pressures, the ability to control this solenoid accurately for accurate boost control is poor. A 3-port solenoid is essentially a drop-in replacement, but does require tuning of the Wastegate Duty Cycle (WGDC) to take advantage. It should not be installed without a corresponding tune. | Reliable boost control above 14psi (i.e., most tunes) |
| Regrind camshafts | The stock camshafts can be reground for [commonly] a 262 duration and higher lift. However, this regrind requires shims to be installed under all of the valve lifters to avoid over-extending the lifters and causing valvetrain clattering noises. | Power above 200awkw on stock internals and turbos (pump fuel) |
| Billet camshafts | Kelford offers billet camshafts for the VR4 via Transformance Mechanical Engineering which increase lift, duration, and cam timing. | Power above 260awkw on pump fuel |
| Adjustable Cam Gears | https://www.ozvr4.com/threads/billet-adjustable-cam-pulleys.17081/ | |
| High flow injectors | Replacement fuel injectors can be installed to provide for power outputs above 200awkw. Note that injectors will require that the ECU is re-tuned on a dynamometer. | E85 Tunes
Power above 200awkw |
| Head bolts | The stock head bolts will allow for combustion gases to push into the coolant jacket at high torque and power outputs. | Torque above 425Nm
E85 Tunes (due to increased Torque) |
| Forged bottom end | The stock pistons and conrods are not reliable beyond an estimated 425Nm. "Your mileage may vary", but it won't be a lot of mileage. The bottom end of the engine should use forged rods and pistons which TME currently recommends.
At very high power, Prism rods have been known to wear out the piston gudgeon pin and wipe out the piston rings as a result, so these are not recommended. |
Torque above 425Nm |
| E85 | The stock ECU can be reflashed with a dedicated E85 tune, or using a custom ROM that allows for E85 flex fuel or switchable maps. Aftermarket ECU options can also be used for E85. | High torque
Safety at high power levels |
| 3SX fuel loop | A larger interconnect between the front and rear fuel rails is recommended for consistent Air/Fuel ratios between the front and rear cylinder banks | Power above 200awkw
E85 Tunes |
| Parallel fuel rails | Parallel fuel rails use a Y-split in the fuel supply so that even for very high power outputs, there is no difference in fuel pressure between the front and rear cylinder banks | Power above 280awkw |
| Aftermarket Fuel Pressure Regulator | For high power outpouts, the stock fuel pressure regulator can become a limitation, particularly if the fuel pressure needs to be raised. | High power builds |
| Larger intercooler | The stock intercooler is too small for high power tunes. The recommended replacement is a HDI GT2 intercooler which is essentially a drop-in replacement. | Power above 190awkw |
| High-Flow turbochargers | The stock turbochargers are designed for low-down torque with boost that comes on rapidly. The design however restricts airflow at high RPMs, with the stock turbocharger peak power at around 5,000rpm and with a boost limit of 20psi.
The 20psi figure does not equate to "good airflow" however and is more indicative of the restriction the turbine wheels. TME offers a range of bolt-on high-flow turbochargers, to suit up to and over 300awkw. Custom single-turbo conversions are also possible, but not common. |
Power above 245awkw |
| Coil on Plug (CoP) conversion | In stock form the VR4 engine has three coils set up in a batch-fire (wasted spark) system with each coil providing spark for two cylinders. At very high power outputs, and for any E85 tunes, the stock coils can fail to provide adequate spark. A Coil-on-Plug (CoP) kit replaces the three stock coils with six coils, one for each cylinder. This helps ensure a strong and reliable spark even for very high power output. | E85 Tunes
Power above 245awkw High boost |
| VK22 spark plugs | VK22 spark plugs are necessary to ensure good spark under the higher stress conditions of a tuned engine. These spark plugs help ensure a more reliable and stronger spark.
Note: your specific engine modifications and tune may justify the use of plugs other than the VK22. The VK22 is the best overall option, but may not be the best for every car. |
Any tune |
| Additional airbox feeds | The stock airbox inlet and rubber lip will collape and restrict power at higher power outputs. An additional hole in the airbox with a large diameter pipe leading to a suitable cold air intake location will ensure that the air intake is not a restriction. | Power above 260awkw |
| Custom intake and intercooler pipework | The stock turbo inlets are suitable for tunes exceeding 300awkw. Custom metal turbo inlets will allow for more audible turbo spool, and may be preferred for the aesthetics and audio experience.
|
Power above 350awkw |
| Larger radiator | The stock radiator is suitable for very high power outputs above 300awkw, but only for road use. | Track use |
| Stronger clutch | The stock clutch setup is not suitable for power above 200awkw. TME offers a stronger clutch pressure plate and better friction disk for power between 200 and 250awkw. | Power above 200awkw |
| Evo clutch | For power above 250awkw, a Lancer Evolution clutch kit should be used. There are many options on the market that can suit, including twin plate setups. Select the option you prefer that will support the torque you are generating.
Note: Evo clutch setups require an Evo flywheel, which also requires a spacer plate and longer flywheel bolts from TME. If buying a clutch kit that includes a flywheel (e.g. twin plate), then you will only need the spacer and bolts. |
Power above 250awkw |