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EVO 8 & 9 Potential Turbo Charger/Intake System Leaks

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Important Service Bulletin for the 2003 – 2006 Mitsubishi EVO 8 & 9 Potential Turbo Charger/Intake System Leaks v1.00

We wanted to educate you about some common faulty equipment used on the stock 2003-2006 Mitsubishi EVO 8 & 9 vehicles. This faulty equipment can allow for turbo charger system leaks. This vehicle uses a MAF sensor to meter air for fuel, ignition, and boost control calculations it is critical that you check your vehicle for these leaks and repair them prior to installing the AccessPORT on your vehicle. These leaks can occur on a totally stock vehicle, even new vehicles with very few miles or drive time on them. With time and operation of the vehicle these leaks can and will get worse. If your vehicle is not tested for these leaks and these leaks do not get properly repaired then your vehicle will have the ability to over fuel itself causing bad gas mileage and poor engine performance. In addition, your turbocharger will overrun itself creating excessive heat which can lead to premature turbo and engine failure.

Is my car effected by these faulty or insufficient equipment?

It has been our experience that several of the factory seals on these vehicle are prone to leak when the turbo/intercooler system goes into boost. Specifically, the EVO 8 & 9 have the following problems:

  • The factory plastic BOV starts leaking air back into the intake system between 8-10 psiG. All leaks get progressively worse as turbo boost pressure is increased to the factory boost levels. This problem is unique to only the EVO 8 since the factory BOV was upgraded to a stronger, metal BOV on the EVO 9.

  • The factory throttle body shaft seals leak air which has already been metered by the MAF sensor when the system is pressurized to factory boost levels. The throttle body shaft seals seal the throttle plate shaft to the throttle body housing.

  • The factory lower fuel injector insulators can leak air which has already been metered by the MAF sensor when the intake manifold is pressurized to factory boost levels. These insulators seal the fuel injectors to the intake manifold.

  • The factory intercooler pipe couplers can leak air which has already been metered by the MAF sensor when the system is pressurized to factory boost levels. Common leak points are the joints beside the engine and battery, and the joint between the intercooler and turbo outlet.

How is my car effected by these leaks?

If you are operating the vehicle with these leaks then several adverse effects can and will occur. Any leak occurring after the MAF sensor has metered the air will make the fuel, ignition, and boost control calculations incorrect. A leak which is present on the charge side of the system (post turbo compressor housing) will make the engine run excessively rich. This occurs because the proper amount of fuel has been injected into the system based on MAF sensor calculations, but the air is leaking out of the system allowing the engine to overfuel itself. These leaks can and will cause bad gas mileage, poor engine performance, and premature wear. In addition, when your charge system has air leaks, it forces your turbocharger to work harder sometimes pushing the turbo beyond it efficiency range. When this occurs the turbo charger shaft speed will increase as it tries to make up for this inefficiency. This additional shaft speed will cause premature turbocharger wear and will create a higher charge temperature which is bad for your engine. This increased charge temperature also forces the intercooler to work beyond it's heat exchanging capabilities. You are welcome to read through the Map Notes for the particular calibration you are running to make sure the vehicle is performing as it should; 2003-2006 Mitsubishi EVO Map Notes Link.

How can I test for these leaks prior to installing my AccessPORT?

We have found that you can easily build your own test equipment to test your system for these leaks using common plumbing hardware found at your local home repair or hardware store. You will need to purchase five items: one 1.5” ABS 90 degree street elbow, one 1.5” ABS cleanout adapter, one 1.5” ABS plug, one threaded air hose adapter that will allow your cylinder leakdown test kit to connect to the plugged end of the pipe, and some ABS cement to glue the cleanout adapter to the 90 degree street elbow. You will then screw the ABS plug into the other end of the cleanout adapter and drill an appropriate hole so the 1/4” tapered air hose adapter can be screwed into the unit so that the fittings are air tight.

 

You can use this test equipment in conjunction with a cylinder leakdown test kit which will allow you to slowly regulate the pressurized air entering your system. Simply disconnect the first rubber intercooler coupler from the turbo J-pipe outlet and insert the test device into the coupler. You will need to loosen the connecting couplet worm drive so you can twist the pipe and turn it down for easier accessibility. Be sure securely tighten the pipe down using the stock worm drives. We suggest you install a vacuum T in the line that attaches to the top of the BOV so you can watch how much pressure is being built in your intercooler piping system. You will be able to audibly hear these leaks show themselves at various pressure levels. The factory EVO 8 plastic BOV will begin to leak at around ~8-10 psiG, the air will leak past the BOV piston and will leak through the outlet to the turbo inlet pipe. You can actually remove the BOV from the turbo inlet return pipe; this will allow you to better hear the leak as well as feel the leak with your hand. Once you install a BOV which can hold the appropriate pressure you will want to increase the pressure into the system until you reach ~22-24 psiG. Allow the air pressure to stay at this level for several minutes, this will allow you to see if you have any pending leaks. An alternative to this system is to install a tire schrader valve where the air hose adapter would go, this will allow you to inject pressurized air into the system. If you do this just be sure to not over-pressurize the system ( >40 psi ).

The factory throttle body shaft seals leak air to the atmosphere at the throttle body. You should be able to actuate and gently wiggle the throttle plate with your hand by opening and closing the throttle plate where the throttle cable attaches itself to the throttle body assembly. You should not be able to hear any tonal differences with a properly sealed throttle body. If you can hear air leaking from this area, if you can feel air leak, or if you can hear pitch changes as the air leaks when you gently wiggle the throttle plate shaft then you will need to remove and replace the throttle shaft seals with stronger ones.

The factory lower fuel injector insulator leaks can usually be heard and felt by hand. When the system is pressurized to ~22-24 psiG you would be able to notice any leaks; you can gently twist the fuel injectors to see if any leaks are apparent. Another option is to spray soapy water on these insulators to see if any bubbles are generated by the air leak.

The factory intercooler pipe couplers can leak air at any joint in the system, but these leaks are usually found at the bottom of the charge pipe (intercooler) system. When the system is pressurized to ~22-24G psi you would be able to notice any leaks, you can gently wiggle the fittings/pipes to see if any leaks are present. Another option is to spray soapy water on these joints to see if any bubbles are generated by the air leak.

If my car suffers from these issues, can they be “tuned out”?

Since these leaks are created by a mechanical problem and can get worse with time and operation of the vehicle, you would need to mechanically repair the system and thus it cannot be tuned out.

What are my options to repair these problems?

To solve the leaking BOV issue, you will need to replace the BOV with a stronger unit. You can replace the stock plastic BOV with the Cobb Tuning EVO BOV, or the stock EVO 9 BOV is an excellent replacement as well. The part # for the stock EVO BOV is 1545A001, and this item can be purchased from your local Mitsubishi dealer. This item retails for around $170.

To solve the leaking seals around the throttle body shaft you will need to remove and replace the factory seals with upgraded ones.

To solve the leaking fuel injector insulators you will need to remove and replace the factory insulators with new ones. New stock EVO fuel injector insulators work well. The part # for the stock EVO fuel injector insulator is MD087060, and these items can be purchased from your local Mitsubishi dealer. These insulators retail for around $3.40 each, we suggest you replace all four of your insulators with new ones if they are leaking.

The leaking intercooler pipe couplers will sometimes simply need to have the couplers properly installed or the worm drives tightened. If that does solve the leaking issue they you can replace the worm drives with t-bolt clamps or you can even purchase an intercooler piping kit. These intercooler piping kits are available from several retailers.

How do I test to make sure these problems have been solved?

Simply perform the same tests you did to discover the leaks. You should be able to see that the system does not begin to leak until around ~24-26 psiG at which point the EVO 9 metal BOV will begin to purge open which is normal. If you plan on running boost pressure above this point then you will need to upgrade your BOV to one which is capable of holding the desired boost pressure. We highly recommend that you make intake system leak tests part of your regular scheduled maintenance.

We have spent extensive time testing our calibrations on vehicles which were known to and tested to have solved all of these common leaks. You will need to make sure you vehicle does not suffer from these common leaks before you install your AccessPORT. The consistency of your vehicle's performance will depend greatly on how well your intake/turbo system is sealed.

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