USDM EVO 8/9 Year To Year Changes

The CT9A (Evos 7-9) have had a fair amount of changes and improvements over the years. There are some things that are different between USDM cars and those sold in other markets. This guide is meant to cover all of the changes that USDM Evo 8/9s (we never got the 7) saw every year that they were sold here as well as all of the parts required to retrofit most newer systems.



The addition of Mitsubishi’s variable intake cam timing system (MIVEC) required some changes to the 4G in order for Mitsubishi to add it for the E9. Most of the changes are in the cylinder head but there are a few other areas on the motor it affects as well. In the head, there are extra oil passages drilled to guide the oil to the cam sprocket to adjust cam timing. These passages are fed by an external line which gets oil from the port on the main gallery which is used for the oil pressure sensor on the E8. This port is actually machined differently for the E9 so technically the blocks are different between E8 and E9 because of this, but there are aftermarket MIVEC feed lines which work on the E8 block. There is also an intake cam sensor added to the side of the cylinder head next to where the exhaust cam sensor housing is located. The intake cam sensor is there to tell the ECU when an intake stroke is occurring so it knows how far the intake cam has been advanced. Since that port on the block is used for MIVEC the oil pressure sensor is moved to the oil filter housing. Mitsubishi also changed the spark plug used in the cylinder head, this isn't related to MIVEC but it's something to be aware of if you're swapping to a MIVEC head. E8 plugs are much shorter so they won't reach the combustion chamber in an E9 head, and since E9 plugs are longer they will get smashed by the pistons if used in an E8 head, don't make this mistake!

Parts needed to swap MIVEC into a non MIVEC 4G:

  • E9 cylinder head (1005A904)
  • E9 valve cover (1035A633)
  • E9 spark plugs (use aftermarket)
  • E9 MIVEC feed line (aftermarket braided recommended)
  • E9 MIVEC feed line head side banjo bolt (MF650115)
  • E9 MIVEC feed line head side crush washers x2 (MF660066) (16mm ID) 
  • E9 MIVEC filter (MD371660)
  • E9 MIVEC feed head fitting (MD373617)
  • E9 MIVEC feed head fitting crush washer (MF660065) (14mm ID)
  • E9 MIVEC solenoid (MD375473)
  • E9 MIVEC solenoid bolt (MF140203) (M6x12)
  • E9 MIVEC solenoid o-ring (1748A002)
  • E9 upper timing cover (MD373568)
  • E9 lower timing cover (1062A023) (E8 cover can be trimmed to fit)
  • E9 left rear timing cover (MD373570)
  • E9 water pump (1300A067)
  • E9 alternator bracket (1801A020)
  • E9 crank sensor bracket (1865A031)
  • E9 intake cam gear (1147A003)
  • E9 intake cam gear bolt (MD374247)
  • E9 intake cam gear cap (MD623113) (should come included with 1147A003)
  • E9 intake cam (if you’re doing all this work get aftermarket cams)
  • E9 intake cam reluctor (1015A239)
  • E8/9 cam reluctor bolt (MD368730) (same as the exhaust reluctor bolt)
  • E9 intake cam sensor (MR507814)
  • E9 intake cam sensor housing (1865A032)
  • E8/9 cam sensor housing bolts x2 (MF140025)
  • E9 intake cam sensor housing cover (1865A034)
  • E9 intake cam sensor housing cover gasket (1865A033)
  • E8/9 cam sensor housing cover bolts x3 (MF140204) (M6x14)
  • E9 oil filter housing (1230A018) (not needed if oil pressure sensor is elsewhere)
  • E9 ECU (you’re better off going to a standalone)
  • E9 wiring harness

Active Center Differential

When Mitsubishi brought the Evo to the US market in 2003 it came with a mechanical all wheel drive system similar to what is found in an E6. When the E7 came out Mitsubishi introduced their active center diff (ACD) system which is a computer controlled center differential. The US market wouldn’t get ACD until the MY 2005 E8 and it was continued for 2006 in the E9. All non USDM E8s have ACD (from what I’ve seen). In non ACD cars there is a viscous coupling inside of the transfer case which transmits power to the rear axle when there is enough friction created inside the coupling via speed differential between the front and rear axle. In ACD cars this viscous coupling is replaced by a hydraulically controlled clutch pack. The ACD pump supplies high pressure oil to the clutch pack to engage it. When the clutch pack is engaged power is sent to the rear axle. Depending on how much pressure is sent to the clutch pack will determine how much power is sent to the rear axle. The two main advantages of the ACD system are being able to change modes for different road surface conditions, and being able to preload the clutch packs to have power sent to the rear without having to wait for a differential in wheel speed. The ACD computer can be remapped for different clutch pack performance as well but there isn’t much info out there on it.

Parts required to swap ACD into a non ACD E8:

  • ACD transfer case (3200A058)
  • ACD fluid pump
  • ACD pump feed hose (3520A013)
  • ACD reservoir return hose (3520A014)
  • ACD fluid reservoir (3520A012)
  • ACD reservoir cap (MR580135)
  • ACD pump bracket (3520A009)
  • ACD mounting bracket (3520A007)
  • ACD computer
  • ACD wiring harness
  • ACD e-brake handle switch
  • ACD hard line from pump to soft line (3520A016)
  • ACD soft line from hard line to transfer case (3520A015)
  • ACD banjo bolt for soft line to transfer case (MF650114)
  • ACD banjo bolt crush washers x2 (MF660065)
  • ACD gauge cluster
  • ACD mode button
  • ACD diff compatible downpipe (aftermarket recommended)

Transmission Differences

All 2003 and 2004 E8s have 5 speed transmissions. In 2005 the MR trim level was introduced and it became the sole trim level for the 2005 E8 and E9s to come with a 6 speed transmission. Many regard the 6 speed as better trans for stock or near stock power daily driven cars, but it is considerably weaker than the 5 speed that came in all other E8s and E9s. Fortunately the 5 speed can be swapped into a 6 speed car relatively easily. From what I’ve seen the 6 speed has the same ratios whether it comes from an E8 or E9 so they are directly interchangeable. The 5 speed ratios had some changes between E8 and E9, it is common for people to mix and match gears depending on their needs. The JDM E8 also had a separate 5th gear ratio from the USDM E8. One other small change was to the cast iron rear mount bracket on the back of the trans, the bracket was changed in 05 to work on both the 5 speed and 6 speed so if you are swapping a 6 speed into your 03 or 04 car you will need that rear bracket too (PS our billet bracket fits both 5 and 6 speeds). The ratios are as follows:

5 speed ratios

  1. E8 = 2.928   E9 = 2.785
  2. E8 = 1.950   E9 = 1.950
  3. E8 = 1.407   E9 = 1.444
  4. E8 = 1.031   E9 = 1.096
  5. E8 = 0.720   E9 = 0.761   JDM E8 = 0.825

Parts needed to swap a 5 speed trans into a 6 speed car:

  • 5 speed transmission
  • 5 speed shifter assembly
  • 5 speed shifter cables (MN107670)
  • 5 speed shifter cable bracket (MR980787)
  • 5 speed electrical harness

Front Differential

When the E8 came to the US all of them came with open front differentials. In 2004 the RS model was introduced which came with a Torsen style limited slip front differential. In 2005 this front LSD became standard on all trim levels. So only 03 and 04 GSR models have an open front diff. The Torsen front diff can be swapped into these cars and are a direct fit, alternatively there are many options for aftermarket diffs too. The stock diff works well but they are known for breaking with heavy abuse.

Parts needed to swap in front LSD:

  • OEM Torsen front diff
  • Wavetrac front diff
  • Quaife front diff
  • ATS front diff
  • Cusco front diff

Cooling System

Most of the cooling system is the same between the E8 and E9. The E9 is the same as the E7 which is similar to earlier evos. For some reason Mitsubishi decided to change it for the E8 and then they reverted to the older setup for the E9. The main difference is in the lower thermostat housing and the water pipe that connects the lower radiator hose to the water pump inlet. In the E8 a traditional thermostat is used and the radiator bypass happens in the form of the coolant circuit for the turbo, throttle body, and heater core. For the E9 a circuit “switch” thermostat is used. When the thermostat is closed to the radiator, it opens the passage in the bottom of the thermostat housing to circulate coolant back to the water pump inlet pipe. When the thermostat opens it closes that bypass circuit so all of the coolant goes to the radiator. The circuits for the turbo, throttle body and heater core still act as bypasses but in the case of race cars where the heater core and throttle body circuits are deleted, a larger bypass circuit is needed. You could loop the heater core connections, but that circuit will always be bypassing the radiator so you are losing efficiency in the cooling system. So it is more advantageous to use the E9 cooling system for track use. If you are converting to the E9 system and are keeping your heater core you will need to remove the fitting in the head that feeds coolant to the throttle body and get the E9 one as it is a T fitting

Parts needed to swap from E8 to E9 cooling system:

  • E9 water pump inlet pipe (1310A259)
  • E9 lower thermostat housing (MD363250)
  • E9 thermostat (MD363571)
  • E9 lower radiator hose (1370A098)
  • E9 water pipe to thermostat housing o-ring seal (MD030763)
  • E9 turbo coolant return line (MD366383) (if stock frame turbo)
  • E9 heater core T fitting (MD184160) (can be deleted)
  • E9 throttle body coolant feed line (1310A087) (can be deleted)

Other minor differences include an extra threaded boss on the water pump body for the E9 where the alternator bracket bolts. The alternator bracket was changed for the E9 because the E8 bracket sits where the MIVEC feed line goes into the cylinder head so an alternate mount was needed.besides this one extra threaded boss the water pumps are functionally identical, so the pump isn’t necessary to change over if you’re just updating to the E9 cooling system.

Body Panel Changes

When the E8 came here in 2003 it featured an aluminum hood and front fenders. The rest of the body is made from steel for all 2003 and 2004 cars. In 2005 when the MR model was introduced both the MR and RS trim levels received aluminum roof panels. Other than the aluminum roof, the body is the same across all E8s.

When the E9 came out the front bumper was updated with a different design. The panel cuts lines are the same between the E8 and E9 so bumpers can be interchanged between them without changing headlights or fenders. In Japan the E9 received a different rear bumper which has a styled diffuser integrated into it. These are a common modification to US cars and require either removing the rear crash beam or getting a lower profile aftermarket crash beam.

The rear wing was also changed between the E8 and E9. The E8 wing has exposed carbon on the inside of the endplate stands and the E9 is body colors. The inside of the center element portion is also foam filled on the E8 and hollow on the E9, the foam filled center element in the E8 has been proven to make the E8 wing more robust with a few E9 owners who have had their center element break directly in the middle from too much downforce at high speed.


When the E8 first came out it had a 9.8cm^2 turbine housing, this refers to the volute (scroll) size, this is also commonly expressed as an A/R. All you need to know is smaller volutes spool faster but sacrifice top end power in exchange and vice versa for larger volutes. For the 2005 MY E8 Mitsubishi increased the turbine housing volute size to a 10.5cm^2 housing, giving the stock turbo a bit more top end. For the E9 the compressor cover was made larger (same size inlet) which was done to help top end a bit more and reduce surging. Both of the compressor and turbine wheels are identical between the E8 and E9. Since the compressor cover is larger on the E9 the compressor outlet pipe is different. Since the turbine housings are externally identical between the 9.8 and 10.5 E8 turbos (E9 uses the same 10.5 housing) those can be interchanged without changing any other parts. Stock E9 turbos are known for being able to make horsepower in the low 400s.

Parts needed to swap from an E8 turbo to E9 turbo:

  • E9 turbo (most aftermarket stock frame turbos are E9 based)
  • E9 compressor outlet pipe (1515A057)
  • E9 turbo oil feed line (1225A042)
  • E9 turbo coolant feed pipe (1310A248)
  • E9 turbo coolant return pipe (1310A171)
  • E9 wastegate actuator (1515A056) (aftermarket recommended)


Bypass Valve

All E8s came with a plastic boost pressure bypass valve. Over time and heat cycles these begin to leak and fail. The E9 came with a metal bypass valve which isn’t prone to the failures of the plastic one. It can also be dented slightly on the top to increase spring pressure if desired. Externally they are identical so the E9 bypass valve is a direct swap.

Parts needed to swap from an E9 to E9 bypass valve:

  • E9 bypass valve (1545A001)


Intercooler Sprayer

When the E8 debuted in the states in 03 it came with an intercooler sprayer, basically a windshield washer sprayer system built into the front bumper cover that sprayed water onto the front of the intercooler to help cool it off. The system was removed in 05 and the button on the dash for it was replaced with the ACD mode button. The E9 never came with an intercooler sprayer. Most owners remove the system and it doesn't make all that much of a difference for charge air temps.


If there's anything that we've missed, drop a comment below and let us know! Thanks for reading along and we hoped you learned something!

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1 comment

I didn’t see anything on interior/wheel options/headlights. I didn’t see any mention of SSL models. Also I didn’t see any mention of the 03 evo 8 having the FMIC sprayers in the cooling system section.

You covered the mechanical portions pretty good. But still a lot of stuff missing.


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