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4G93T Modification From Mild To Extreme Part 1

Finally is time to write modify information for 4G93T. For all the first generation 4G93T owner (I am one of the proud owner :D), hope this modify information will help you all.

It is easier for a turbo engine to increase HP compare to NA (Normally Aspirated) engine. We can simple increase the boost slightly but not over the 4G93T limit. From my research, 4G93T original internal parts are able to withstand up to 100kPa (14.5PSI). With slightly increase of boost pressure, the original injectors, fuel pump and the ECU are still able to work as expected.

Start off by getting a full free flowing exhaust system preferably 2.5” or 2 ¾” the whole way through from the turbo. You will notice how much easier the car breaths now at higher revs. Don’t go to 3” as you will blow your turbo by over boosting it. (Unless you get an external waste gate) Even then, you will need it to be 2.5” from the turbo as the oil filter is in the way so a 3” will not fit. However bare in mind that open pod air filter without proper heat shield will make your engine suck in hot air which will reduce your engine performance. We can always install a CAI which suck in cold air directly from outside atmosphere or install a heat shield which prevent hot air in the engine cabin to be suck in by the air filter.

Intake (Air Filter):
Try to remove the factory air box. Then you will notice the original CAI (cold air intake) which 1 end is direct to the inner guard and the other end is to the factory air box. Replace the original factory air box by using either HKS open pod flow filter or K&N open pod air filter. From the research by some car enthusiasts, K&N is providing an overall performance in term of filtration and air flowing. Meanwhile, HKS open pod provide a very good air flow but the filtration is bad.

The GSR cooler is not going to provide you with much help at all. Take the bumper off and remove it, try and get an EVO I/C if possible but if not a VR4 or similar will do. Dependant on how you run the piping you may or may not need to get an EVO style bumper or hack apart your standard one. You can fit a huge IC if you pipe it so it doesn’t have the long return pipe over the intercooler, Run it the short way over the turbo on the passenger side instead. Piping is probably best at 2 1/4” or 2.5” max and try not to install a big size intercooler piping because with this you will feel the boost lag. You will notice a big difference on hot days and motorway type driving.

Intake 2 (Air Filter Piping):
Take a look at the black rubber pipe between the turbo and the airflow meter. Replace this with a mandrel bent 3” stainless pipe. Its also a help at this stage if you relocate the battery to the boot, then you will be able to get a much better airflow to the filter.

Although GSR factory fitted injectors (390cc) are able to work with 100kPa boost but this is not good to max out the injectors' duty. Therefore it is preferable to change to vr4 injectors (440cc) or Evo injectors (510cc) if there are future extreme modification. This should bring it up to around 270hp dependant on boost levels etc.

Throttle body:
The GSR T/B is 54mm an Evo one is 60mm but people think they are worth lots. You can get one from a Viento, it will bolt straight to your inlet manifold but you will need to sort out the piping (where it used to go through that metal elbow) you will need to adapt it from 2 3/4" back to the 2.5" intercooler piping that you have at the mo. Problem being the inside of your manifold is only 54mm still you will need a 60mm drill bit to fix this.

Inlet manifold:
Once this is off you will see how crap the factory castings are. The Holes in the manifold are hardly a flush fit with the holes in the Cylinder head. Also while it’s off widen up the ports near the injectors. Sounds hard but all makes sense once its in bits.

Fuel pump:
 GSR fuel pumps are weak! Get an Evo pump (bolt in) or a GTO pump or similar. At the same time increase the voltage to the pump by putting a relay in on the power to the pump and a heavier duty cable from the battery to the relay and relay to the pump.

By doing all the above modifications, the engine is able to produce 300hp and almost maxing out the GSR.

Oil Cooler:
Turbo engine produce heat more than a NA engine. Thus improve the reliability and life span of the engine is important. Getting an oil cooler from an EVO/ VR4 or similar oil cooler will help to reduce the heat of the engine oil.

High Cam!. This will give it a mean sounding idle and improved torque once on boost. Maybe another 10hp. In addition to this you could add in adjustable cam gears to make sure the timing is correct. Not long ago, TOMEI announced that they are producing high cam for 4G93T.

As of now, with all the performance parts changed and increase of horse power of the engine, the factory fitted brakes are not able to provide better "stop" power for the car. Get some decent pads or if you can find some front brakes off an Evo or an auto VR4. These are 2 and bolt up to the factory mounts. But please bare in mind that Proton Satria, Wira and Putra which mostly these models will install the 4G93T are having a PCD 100 wheel lug. If change to Evo or VR4 braking system, this will change the wheel lug to PCD 114.3.

Below are the flow rates for a few different options. All of these are TD05H based which is what is on VR4s and EVOs. It is quite easy to make a hybrid turbo so a good start would be a blown VR4 turbo. The compressor housings even though called TD05H can vary, the whole EVO housing is bigger than the VR4 housing to allow for the bigger wheel in it. I would recommend a VR4 exhaust housing and an EVO 3 compressor wheel and housing rather than a whole EVO 3 turbo because the VR4 exhaust housing is a 6cm and the Evo is a 7cm. Meaning the VR4 will spool up quicker. The flow rates might not mean much to you but are a good comparison to each other. Study the comparison result here. Standard on this site is VR4 14b to give you an idea.

14B (VR4) flows 370cfm @15psi
16G (EVO1-2) 505cfm @15psi
Big 16G (EVO 3) 550cfm @ 15psi

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+ akatsuki + said...

great info bro.

Ben said...

Hi Akatsuki, thanks for the visit. Btw nice MIVEC hybrid project you got there.

Anonymous said...

Great Info...TQ...Bro,i'm driving a wira 4g93t..appreciate it if u could share some idea on how to wind down the exhaust note to a standard silence (if possible)...without compromising (maybe a bit) on the performance...I'm currently using a 2.5" str8 pipe,a centre bullet and a 3" Jasma muffler...

Ben said...

Try to use the s-flow muffler. It definitely can help to reduce exhaust noise

Anonymous said...

Any idea on the brand?..or any custom s-flow would do the job?...

Ben said...


I recommend RSR as currently I'm using it. The noise level is very low.

Anonymous said...

Ok Bro...thx a lot...really appreciate it...gud luck in ur projects....happy motoring

Ben said...

No problem, it is my honor to share information with you.

Anonymous said...

magnificence post , this is so great just wish i could source all these parts just as u said but it is so hard to get these were i am from ........anyone who can help me get these stuff to the USA please pm me at

Anonymous said...

hi bro ben...need some advice..i own a 12 years old satria 1.6 auto transmission. i've installed 4-2-1 extractor, straight flow muffler and already put in coolent in radiator. The engine heat is still quite high. ANY suggestion on how to reduce the engine heat? should i istall that engine oil cooler. Is it the same with intercooler? can intercooler be used in standard engine not turbo like mine? I have problem with high engine heat and drop in horsepower. thx -


Ben said...

Hi Newbies,

First of all, have you check whether your radiator stuck? Try to flush your radiator. Second, check whether is your engine gasket is in good condition, this will cause heat problem as well. You may install an engine oil cooler to cool off your engine oil. Engine oil cooler is different from intercooler and it is useless for a normally aspirated (NA) engine to install one, unless you are talking showing off effect.


Cygee26 said...

Nice Guide for Upgrade Plans in an 4g93T
i know this is an old post but i want to check if what's under my hood are stocks. specially the Injectors.

when i got the car it has a 450cc Low Impedance Injectors
-offset intercooler side mount (Small)
-stock Turbo TD04L-13T-5.0

i will follow this guide to minimum. :)

Unknown said...

hi ben, first and foremost let me introduce myself. im a student currently, and will be working part time after getting myself a car. im having a tight budget, a very tight one and still couldnt figure out whether i should get a putra with mivec 4g93, or just should i go straight to turbo? i have no experience on proton maintenance, and i would really love if you could give your opinion on mivec and turbo platforms. thanks btw, ur site is really helpful