Applying the Basics to the 3S-GTE
The first and most important thing to do before embarking on any power modifications to the 3S-GTE is to get the basic engine in shape to handle them. Perform any basic maintenance that may have been neglected by either you or the previous owner. An oil change, new oil filter, spark plugs, distributor cap, rotor, spark plug wires and a flush of the cooling system should be the first priority of the day before proceeding. Also, keep in mind that a modified engine is less tolerant of poor maintenance and the price that you pay for increased performance is prompt and diligent maintenance.
Strength, a moderate compression ratio and an intercooler allow the stock 3S-GTE to easily handle higher that stock levels of boost pressure. Maximum stock boost pressure is 10-11psi. With the addition of three simple, inexpensive devices, this can be safely increased to 15psi for a gain of nearly 10rwhp per additional pound of boost. After doing this, you can expect to be producing approximately 200rwhp. First, you need an accurate boost gauge to be sure that you are not boosting above 15psi. The stock boost gauge is slow to respond, peaks below 15psi and has no numbers to tell you how high you are boosting. Second, you need to raise the point at which the protective fuel cut feature kicks in from around 12psi to 16 or 17psi. This can be done easily and inexpensively as shown here. Finally, you need a boost controller to raise the actual factory set boost pressure to 15psi. Manual boost controllers are inexpensive and do the job while electronic boost controllers are more expensive but allow easy adjustment from the cabin. If you get a manual boost controller, go with a ball and spring type instead of a bleeder type. Ball and spring controllers keep the wastegate shut until you approach the desired boost limit while bleeder types let the wastegate partly open at lower boost and result in a slower transition to full boost. Several boost controllers are available with CARB exemption stickers, so you can take advantage of this performance enhancement in all 50 states.
To help keep the cylinders cooler under high boost and insure that the stock ignition keeps the spark going strong, you should replace the stock plugs with a set of NGK 6097 copper spark plugs. These are one step colder than the stock plugs to help keep detonation in check. You should gap them at 0.028", which is a little less than stock to make it a little bit easier on the ignition system to keep the spark going strong and reliably even under higher boost pressure. These will need to be replaced every 5K miles or so. Note that you do not need to make any other changes to the stock ignition system until you reach a higher power point. It is a myth that you can make more power with aftermarket ignition components on the 3S-GTE. All that the ignition can do is lose power if it is weak or not properly functioning. The stock ignition and components, except for the spark plugs is adequate to 17-18psi in good working condition.
Because the engine needs air to produce power, a small but increasingly important amount of power will be gained by replacing the restrictive stock air intake with an aftermarket high flow air intake. At 15psi boost, you can expect to gain another 2-3rwhp from a relatively inexpensive air intake. The air intake is not as critical on a turbocharged engine as on a normally aspirated engine because the compressor can compensate for a restrictive intake better than a normally aspirated engine can. After upgrading the air intake, you should be making nearly 205rwhp. Many aftermarket air intakes are CARB exempt.
Much more important to the stock 3S-GTE than a less restrictive air intake is a less restrictive exhaust. The most restrictive portion of the stock exhaust is the b-pipe between the downpipe and muffler. This pipe contains a small catalytic converter so it is not legal to upgrade it in some states even though the primary catalytic converter in the downpipe cleans the exhaust enough to meet emission requirements. There are many aftermarket exhausts that replace the stock muffler and b-pipe. Choose one constructed with 2.5" or 2.75" mandrel-bent pipes. Any of these will yield an extra 10rwhp. If you are fortunate to live in a location without emission restrictions or to afford an additional exhaust system to put on just for off-road use, replacing the stock downpipe with a 2.5" downpipe will gain you another 5rwhp. At this point, you should be able to net around 220rwhp at the dyno.
To set a good foundation of reliability for the next stages, it is prudent to make the next modification to your 3S-GTE one that prevents detonation. A good aftermarket side-mounted intercooler will add another 5rwhp to your setup. The larger intercooler will make power in two ways. First, it will cool the air charge more than the stock unit. Second, there is less of a pressure drop across the larger intercooler core than there is across the stock unit, so the turbo has less work to do to reach the desired boost pressure. This means that cooler air will reach the manifold and produce more power at the wheels. Now that you have more cooling on your side, add another pound of boost to take you up to 16psi and get you another 5rwhp. If you have made all the modifications mentioned so far, you should be making around 230rwhp.
The intake manifold and TVIS were designed to provide good low end torque and high top end flow using a dual runner per port setup with a set of butterfly valves kept closed at low RPMs to increase air velocity into the port and open at higher RPMs to increase flow capacity. The proper TVIS opening point lowers as VE improves (better exhaust, turbo, valves or cams). The ECU keeps a fixed opening point around 4200RPMs which is too high for modified engines. Consequently, there will be a torque dip from around 3800 RPMs to 4200 RPMs. The ECU also uses the TVIS to reduce engine VE if it has detected knock in the recent past. This can cause variations in performance for no apparent reason. The TVIS be kept functional as long as you continue to use the stock intake manifold but you should control the TVIS with an MSD RPM switch. You will need to purchase an MSD 8950 along with an appropriate RPM module, which is going to be included in wither the MSD 8743 (for even 100 RPMs) or MSD 87431 (for odd 100 RPMs) opening points. Alternatively, you can make your own fully adjustable RPM module. Most modified 3S-GTEs will need to open the TVIS between 3600 and 3900 RPMs. The only way to know for sure is to do a dyno pull to 4500RPMs with the TVIS open and another one with the TVIS closed keeping everything else the same. Then, the point at which the two torque curves cross is your best opening point.
The best place to install the MSD 8950 switch is in the engine bay near the igniter/coil. Cut the red and blue loops on the switch since you are going to run on a 4-cylinder engine. Ground the black wire to any bolt that goes into the chassis. With the ignition key off, pull the 2 pin connector from the coil and splice the red wire of the switch to the black wire with a red stripe. Splice the white wire of the switch to the black wire with a white stripe. I recommend using good solder or crimp connections to do this. Plug the connector back into the coil. Now go under the intake manifold and locate the TVIS valve. This valve has one vacuum hose going to the TVIS actuator, another vacuum hose going to a blue/purple canister mounted under the intake manifold and a 2-pin electrical connector. Disconnect the connector and cut the green wire with a black stripe about two inches from the connector. Cover the end of this wire from the engine harness with electrical tape. Connect the other end of this wire going to the connector to the gray wire from the MSD 8950. Use a pair of spade connectors so that you can easily set the car back to stock or control the TVIS by hand to help you find the switch point at the dyno. Reconnect the connector
For the interim, install a 3800 or 3700 RPM module in the switch. Now you just need to find the best switch point at the dyno as explained above. To keep the TVIS open, you can disconnect the gray wire from the TVIS control valve and leave it hanging in air. To close the TVIS, ground the wire going to the TVIS valve. If you notice no difference, your TVIS system is not working properly and you must follow the directions in the BGB on how to diagnose it.
The next modification is a tricky one that requires the use of a wideband O2 (oxygen) sensor to do properly. Most performance shops that rent dyno time will hook one of these up to your car while you are using the dyno (and if they don't, go elsewhere). The stock ECU (Electronic Control Unit--the computer that controls the engine) is programmed to dump a lot of extra fuel after the boost pressure reaches 12psi to keep the engine safe from detonation. This extra fuel, however, reduces power by lowering combustion temperatures that we can reclaim by "leaning" the air-fuel mixture so that there is a little less fuel and a little more air than the ECU is programmed to deliver. The "best" air-fuel ratio (AFR) to run the 3S-GTE at on pump gas is around 11.5:1. The least expensive way to lean the AFR safely is to get an adjustable fuel pressure regulator, an inexpensive fuel pressure gauge and a fuel computer such as the S-AFC. Some performance shops will tell you that you only need an S-AFC, but the safest combination is to use all three. Install both the fuel pressure regulator and the S-AFC. Set the S-AFC to zero adjustment across the board and adjust the base fuel pressure to 35psi (base fuel pressure is the pressure when the fuel pump is running but the engine is not, insert a paper clip in your diagnostic connector between +B and FP to produce this condition). Take the car to a dyno and hook a wideband O2 meter to it. Readjust the base fuel pressure to 30psi and add about 10% fuel at every point in the RPM range. Do a pull on the dyno and print out the AFR chart. It should start at around 14.5:1 and quickly drop to near 10.0:1 or even lower. Use the S-AFC to take out a little fuel in the ranges above 3500 RPMs where the AFR is under 11.5:1 but don't go under the stock (0%) level. When you (or the tuner) is finished, you should be at or close to 11.5:1 AFR under high boost and you should have picked up another 10-15rwhp to get you in the 240-245rwhp range. This is around 300 horsepower at the flywheel, which is 50% more power than you get out of the stock 3S-GTE. Not bad for a $1000-$2000 dollar total investment so far.
This is about the most that you will be able to get out of the 3S-GTE with the stock CT-26 turbo. You now have a big decision to make: do you stay where you are at and call it good enough or do you want just a little bit more or do you want to go for truly serious (and expensive) power?
If you want just a little bit more power, you need to upgrade the CT-26, purchase a CT-20b which will bolt right on to the stock exhaust manifold or, if you are a little more adventurous and live in a state with less restrictive emission laws, invest in a TD05, TD06, GT25R, GT28R or T3/T4 turbo kit. If you upgrade the CT-26, get a CT-27 upgrade from ATS Racing. This is your best choice because you are now at the point where the biggest thing preventing your engine from producing more power is the restriction that the turbine wheel and turbine housing are placing on the exhaust. If you have been paying close attention to your boost gauge, you probably noticed that the CT-26 is unable to keep producing 16psi of boost beyond 5.5K RPMs. The CT-27 upgrade machines the turbine housing to allow more exhaust to escape the engine. This will allow you to continue producing 16psi of boost until 6.5K RPMs and add another 15-35rwhp to the car. This will take you up into the 255-275rwhp range. As you approach this range you will have to re-do the AFR tuning and you will reach the point where you will actually need to raise the fuel pressure back up to the 38-40psi stock levels to keep a safe AFR. At these levels the S-AFC will be zeroed out again and can even be removed.
If you go with a CT-20b, you can expect to pick up another 15-35rwhp after you re-do your AFR tuning. Depending on the state of your fuel system, you may or may not be able to make over 275rwhp with the stock genII fuel system. If you can, then for less than $3000 dollars (if you have done your own labor), you should be at or near 275rwhp. You are now sitting at or close to the limits of the fuel system and you run a serious chance of damaging your engine if you exceed those limits. You now are or have already surpassed the limits of the stock clutch and need to be thinking about replacing it with an aftermarket clutch that can hold more torque. ACT, Clutch Masters and SPEC all make good aftermarket street clutch kits for the 3S-GTE. While replacing the clutch, you can also install a lighter flywheel. The flywheel will not produce more power, but it does lower the rotational mass that the engine has to spin up and thus transfers power to the wheels faster. It will improve drivability once you master the easier-to-bog nature of the lighter flywheel.
A Few Myths
Let me say a few things about what not to spend your money on unless you want to do it just to show off.
An aftermarket Blow-off valve is not needed and will gain you nothing except maybe a loud sound and rough running or stalling after it goes off. The stock bypass valve is strong, fast and quiet.
Fancy wires and ignition boxes don't do much for you. Also, these devices never produce power (except through ignition timing tuning, which is not essential to getting to 275rwhp).
Getting larger fuel injectors or a larger fuel pump won't do you any good until you have the proper electronics to control them properly. An S-AFC is not the proper electronics. Since the stock fuel system can be pushed to 275rwhp, you definitely don't need or want bigger injectors or pumps before then.
You do not need to get rid of the AFM, the TVIS, the EGR or upgrade your stock cams, or port your head, or get a larger throttle body, or an aftermarket intake manifold, or get forged pistons or anything like that until you go over 275rwhp (and way beyond that for some of these things). Don't waste your money on these.
You don't need to mess with your base ignition timing or your cam timing to hit 275rwhp, so leave that stuff alone and mess with the things I mention because those are the ones that will make you safe and reliable power.
A 2.5" downpipe and exhaust system is perfectly adequate to support 275rwhp. There is no need to invest in a 3" exhaust system unless yo are seeking to make 300rwhp or more.
The notion that a CT-26 just puts out hot air above 15psi is nothing more than hot air. All turbos produce hot air and the higher the boost the hotter it is. Proper intercooling allows higher boost to be safely used regardless of which turbo is being used to produce it.
Contrary to popular belief, bigger is not better in the power game. Balance is essential and "just big enough and no larger" is usually optimal. For example, if your intake runners or valve ports are larger than they need to be, you will lose power instead of gain it. If your compressor wheel is larger than you need, you spool slower but get no additional power to make up for it. So, if there is something that you feel you need to compensate for, don't go doing it with engine parts, otherwise you are going to be feeling pretty bummed the next time that you go to the dyno.
Big Power, Big Money
If you are still reading, then you must be looking for serious power and willing to spend some serious money to get it. Beware that street manners and very high power are very often at odds. A very high power 3S-GTE is not necessarily a pleasure to drive every day in traffic. Be mature when you set you performance goals and realize that you cannot have it all. In particular, very high power and high reliability are not cousins in the world of 4-cylinder engines. If you cannot afford to be without your 3S-GTE, then leave it relatively unmodified.
Somewhere around 275rwhp, you will reach the limits of the stock fuel system and you must upgrade the fuel system to safely move on. If you do not, you run the risk of letting the air-fuel mixture get too lean and burn your pistons, particularly on cold mornings when the air is denser.
At this point I strongly recommend investing in an aftermarket engine management system (EMS). An EMS is a completely programmable fuel and ignition management computer that can be programmed to deliver the precise amounts of fuel and timing for all situations. There are several reasons to do this. First, the stock ECU is programmed with stock fuel injector sizes and stock VE values and the next few stages are going to change those values dramatically. Second, some of the stock engine sensors have reached and surpassed their measurement ranges and, in the case of the AFM, are becoming a serious power restriction. Third, black boxes like the S-AFC that can be used to some extent to trick the ECU into changing its behavior will quickly multiply and create an inscrutable and untenable tuning infrastructure. By replacing the heart of control system, you greatly increase what can be done and greatly simplify how it is done. There are several good EMS units to choose from. Expect to pay $1500-$3000 if you do the installation yourself or go with a plug and play system or if you go with a non plug-and-play system $3000-$5000 and have somebody else do the installation.
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