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Turbocharging 101*

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  • Turbocharging 101*

    by Ian (Screen name qksl2) at qksl2 and now FSR

    Turbocharging 101

    So you wanna turbocharge your Saturn? Do you want to build your own turbo kit but have no idea where to start? Are you unsure of what turbo, what intercooler, or how to add fuel to your setup? Well, I have am working on putting together a DIY Turbo installation section. I will try to cover everything that is needed to safely and effectively turbocharge your Saturn.

    1. What are your goals? How fast do you want to go? How much boost and what kind of driving do you want to do?

    If you want a quick street car for light to light racing, and extra punch all over, you'll want a low boost, small turbo setup. If you want a freeway terror, prepare to do a larger turbo along with more engine mods to handle the power output. First, make that decision. You'll always be compromising one aspect of performance for another. I'll write this with what I know best: a well balanced setup for the "average" enthusiast. This is assuming a driver who wants reasonable daily driveability, street quickness, and weekend warrior speed.

    2. The motor. Is your motor ok to boost on? Should you build the internals before boosting at all?

    Mostly, this depends on how much boost you want to run. Let me make this clear: it is entirely possible to run boost for a long time on a stock motor in good condition. The key? Proper tuning and smart driving. That means not getting greedy with boost, and careful maintaining of the car. Changing plugs and oil often is very important, minimally. You'll also want to make sure auxiliary items are in good shape: Fuel injectors, 02 sensor, fuel pump, etc... all need to be in good working order. As far as the motor, its best not to boost on high mileage cars. High mileage does NOT automatically mean the engine is in any worse condition, but it is more likely. One way to test if your engine is in good condition is to compression and leak down test it. Any shop can do it for you easily, or you can buy the tools to do it yourself from your local parts store. Compression should be between 180 and 210. Anything lower and your engine may not be a good motor to put extra strain on.

    Keep in mind that stronger internals do not mean more power. They are simply a way to have a "buffer zone" against engine damage, should detonation occur. Detonation that will break stock pistons or rings will break forged internals as well.... its just a matter of time. That being said, stock internals are good for lots of power if tuned correctly. The pistons on the older engines have thicker ring lands which are more resistant to cracking. All of the engines stock have 9.5:1 compression. With a good fuel system, one can safely run 200whp in good tune. This is good for low fourteens easily... For daily driving, though, I highly recommend boosting down: while maybe not necessary, it reduces stress on the motor. Believe me... 3 psi is more than enough for tooling around.

    3. The manifold: What style should I get? What kind of flange?

    A turbo manifold is just like your stock exhaust manifold except for that it directs air into the turbo to drive the exhaust wheel instead of leading straight out to the exhaust system. After going through the turbo, the downpipe is what connects the turbo to the rest of the exhaust. The design of this is critical. There are log style turbo manifolds, cast, and tubular style. Tubular equal length manifolds make the most horsepower, with longer runners and an equal length design. They are designed to where exhaust pulses do not interfere with each other. Faster spool up and strong top end power are characteristic of this style. However, they are typically more expensive, require more bracing to prevent any cracking. They also take up more space and are more difficult to design. Both Garage Advance and are making equal length tubular manifolds. Email me for details.

    Twistec has popularized the use of a stock cast exhaust manifold that has the bottom chopped off and a flange welded on. This design is efficient in packaging. The cast manifold is very strong, and although tedious, when properly welded, the flange mounting is good as well. This puts the turbo down low, which is generally a good thing. The main drawbacks for this manifold is that horsepower is limited by the extremely small stock runners. It is also not equal length. However, it is cheap to build, and effective for a low boost setup.

    Log style manifolds come in many variations. They are available now from as well as Garage Advance. Thomas Knight has had a design, but I believe is no longer making them. The Garage Advance design is a very typical and simple log style. This has been used to make great power on a saturn, despite its design. The benefits are that they are relatively cheap and simple, as well as strong. The log style is better than most, with slightly longer runners and a reasonable collector.

    As far as making your own, you'll have to work with a shop that does TIG welding. SS is the best way to go, and you can then have it ceramic coated. It is not necessary, but nice for looks and heat control. The best flange for most applications will be a standard T3 flange, as it allows you a variety of options.

    4. What kind of turbo should I get?

    Ok, let me make this easy. For a stock saturn motor looking for a great powerband, a T3 is the best way to go, period. For specifics, you'll want a .60 compressor side and a .48 exhaust. Right here, I won't go into the A/R's (Aspect Ratios) for simplicity reasons. But a larger number will flow more CFM at a given RPM than a smaller number. So a .48 exhaust ensures quick spool up, and a .60 compressor will flow a lot of air for lots of hosepower. Lag is the time that it takes for a turbo to get up to speed where it produces boost. So the weight of the rotating wheels causes the lag. A larger T4 compressor or exhaust wheel is heavier, and the extra inertia takes it longer to get up to speed. The exhaust wheel is 70% of the weight, so the size and trim has the most effect on spool up. You can change the compressor wheel a lot more without affecting spool up too much. That is why a conservative .48 exhaust is good, while a larger .60 compressor is perfect. On a stock saturn motor, this means boost in the 2000-3000rpm range, depending on your setup. The midrange is stronger, with a nice surge of power. Then you run right into a rip roarin' top end, a huge whack of power will lay you into the redline very quickly. On the freeway, lag as absolutely nonexistent: think about the go pedal and you're in boost, pulling harder than any n/a saturn can downshifting to third, while at 3000 rpm in fifth.... From a roll, it will break the tires loose as the boost comes up. Its really quite amusing.
    The T3 is also nice because it is easily rebuildable, cheap and plentiful to find, and can be upgraded to a T3/T4 later for more boost, simply by changing the compressor wheel and housing. As far as other turbos, a 16G is a good choice. Its somewhat comparable to a T3, though less plentiful. A T28 is a great turbo, as well. But again, my favorite choice is the T3 60 trim.

    5. How do I add fuel to my turbo system?

    This is the most controversial issue out there, right now. There are several methods that work, some proven, some not. For Saturns, you can do a few things: Larger injectors with an rising rate fuel pressure regulator (RRFPR), an AFC or AFR with larger fuel injectors, extra injectors and a control unit, or a full stand alone fuel system.

    A simple and effective way to add fuel for low boost would be to use larger injectors, such as 35# injectors along with a RRFPR. You'll need "Bosch" style injectors: commonly available as Ford or Mopar injectors. Check out for injectors. 35# injectors are good for a descent increase in power, along with a fuel pressure regulator that is either 1:1, 2:1, or maximum 3:1. This setup will be safe, consistent, and easy. It should be tuned on the dyno by adjusting base fuel pressure. BTW: A rising rate FPR bumps up fuel pressure as boost goes up. A 2:1 raises fuel pressure 2psi for every 1psi of boost. So at 5 psi of boost pressure, fuel pressure goes up 10 psi, which adds the extra fuel necessary for boost. This is not the most precise way, but it works, and should be reliable. It will DEFINETELY require tuning on a dyno, though!

    Something not absolutely proven with Saturns, but commonly used among turbo Honda owners is a simple AFC or AFR with larger injectors. An AFC is a fuel computer by Apex, as the AFR is the same by HKS. Both modify the map signal to the computer so that you can adjust the injector pulse width at certain RPM points. I will be experimenting with this in the future, and will determine how well it works. This is a step up from using a fuel pressure regulator, as it is more precise.
    The most successful way of adding fuel to turbo saturns thus far has been the SDS EIC. That is: The Simple Digital Systems extra injector controller. I have used it, Chris used it, Alex, Tom, Paul, and Eric have all used it. While highly scrutinized by many never-had-a-turbo people, it has simply been reliable. Again, it is a somewhat crude, but works. A huge benefit of this system is that it is completely separate from your stock system. Think of it this way: Your entire stock fuel system goes on doing its job as it normally does: It idles just the same, runs just the same while not under boost and adjusts the a/f ratio for maximum economy when cruising. The SDS is a system that runs another fuel feed line to two extra injectors in your intake piping. (You can also get four extra injectors, one in each intake manifold runner). You weld two injector bosses into your intake piping before the throttle body, much like a wet nitrous system. The two extra injectors are controlled by the SDS, which is boost and rpm referenced. This means that it sees both boost and RPM, and adds fuel accordingly. You adjust it by two knobs: One to tell it when to come on (how much boost before it starts squirting), and the other is how much to inject. So when your engine goes into boost, it starts to add fuel. It is very easy to get it tuned on the street, and then can be fine tuned on the dyno. It is not too precise because you cannot adjust it at many RPM points. However, benefits are that there is no extra strain on your stock fuel system, and the car drives just like normal when you are not in boost.

    The last option is a full stand alone fuel system. I personally like the Haltec system. This is a whole different ball game, and I do not recommend this for anyone who does not want to really spend some time getting everything dialed in right. You'll definitely want to have a shop help you with this!
    The guys are working on what's call the Megasquirt, which is a DIY fuel management system. It is not full stand alone in that it does not control timing. However, it has complete control over the fuel system. It will allow us to run very large injectors, and tune completely for boost. Chris and Mike are also in on this, and big thanks to Canadian Ben for pioneering the subject. More on this as time goes on.

    6. Intercooler.

    I very highly recommend an intercooler with your turbo setup. It will cool off the intake charge greatly. Cooler intake charge means more power and more detonation resistance. This is pivotal with an engine not designed for boost. It allows for a buffer zone against detonation, and more consistency while running repeatedly. A great intercooler is the Starion intercooler. These can be found on ebay commonly for not much money. They utilize the same core as the Lancer Evolution does, so it flows very well and is efficient. Other options are the ginormous Twistec intercooler, or a custom spearco.
    Mounting a front mount is not too difficult on most saturns. It will require trimming of some of the plastic baffling, though.

    7. Intercooler piping.

    The best piping to use is 2" "hot" and 2.25 inch "cold". The reason for this is the velocity and air density change as it goes through the intercooler. Piping can be sourced from JC Whitney, Silicon connectors and clamps can be sourced from or For clams, the screw type works fine, though the T-bolt camps are very nice!

    8. A blow off valve is necessary.

    It relieves pressure in the intake piping created by the spinning turbo between shifts, where the throttle plate closes. It is to prevent damage to the turbo from spinning backwards, known as compressor surge. I like the Turbo XS units, though HKS and Blitz also make very nice ones. These can be commonly found on Ebay or other parts places. The vacuum line reference should go to the intake manifold for an accurate reading.

    9. Boost controller.

    An electronic boost controller is very nice. It allows you to run minimal boost for around town driving, and the bump it up for the occasional street encounter or drag race. However, a manual controller will work. Be careful, though, as manual boost controllers are more prone to boost spiking. As far as which controller, it is mostly preference. I really like my GReddy PRofec A, though the PRofec B is cheaper and simpler, but works well. The ACV-R is quite complex, and has some nice features, but costs quite a bit more.

    10. Gauges.

    Minimum would be boost and a/f gauges. Any boost gauge will work. For an a/f gauge, I like the Halmeter in combination with an o2 sensor from an 89 Escort. It has 3 wires instead of one, so its heated. The Halmeter is a 30led a/f gauge that is available from The best solution would be a wideband, but so long as you tune your car on the dyno, the Halmeter is good enough to simply monitor that everything is ok.

    11. Oil feed line.

    It should be a -4 an braided stainless line. Earl's lines are available through Summit Racing. The return line should be a minimum of -8 an, or even -10 an. It should have no kinks, and be downhill all the way. You'll have to have a turbo return line fitting welded into your oil pan. Make sure it is above the level of the oil!


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