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A Practical Guide to Forced Induction for V6 F-Bodies



SUPERCHARGERS

There are several types of superchargers available on the market including Roots, Twin Screw and Centrifugal. Just because you can potentially buy a unit of one type does not mean that it can “bolt up.” The first two types require massive amounts of work to make work on the V6 F-body. As they are mounted on the top of the motor, cowl modifications need to be made at the least. We will therefore stick with the Centrifugal type as it is easier to adapt and kits exist for them.

There are of course choices in brands of Centrifugals including Paxton-Novi, Vortech, ATI-Procharger, Rotrex, and Powerdyne. There are some differences in brands and various strengths and weaknesses for each brand and unit. Paxton-Novi, Vortech, and ATI Procharger are all internally gear driven which makes them loud, powerful, and potentially less mechanically efficient. They also require some sort of lubrication for the gears. Both the Paxton-Novi and the Vortech units require an external source for lubricant (The ATI P600B does as well), usually the engine’s supply is tapped. This is an extra headache to deal with, but nonetheless these are still great blowers. The ATI P1SC is completely self contained. For all out power these are great options, but for the person who does not want to go over 10psi they might be a bit much.

The Powerdyne superchargers are internally belt driven (although they now offer a gear based unit). For low boost applications this can a bit more efficient, quieter, can require less maintenance. It is limited to under 12psi in most applications, due to the bearings, and is typically not taken over 9psi in the V6 F-Body community.

Rotrex units have not been adapted to a V6 F-body as of yet. If you are interested in the differences, go to www.rotrex.com (The Koenigsegg CCR has a dual Rotrex charged motor). After all this it must also be mentioned that currently none of these companies offer kits directly. There are, however, two kits being produced for our cars for our cars, one using the P1SC (a self contained unit) from ATI-Procharger, and the other using the BD11A from Powerdyne.

Powerdyne

The Powerdyne kit is available from RK-Sport and other vendors. It comes with 3 brackets (one for the blower, one to support the blower bracket, and one for the tensioner), the piping, an FMU, and all the needed hardware. The main issue with this kit is the fact that the blower is driven off the back of the accessory belt which is suboptimal. The pulley can slip on the belt resulting in less boost than is desired. To combat this the belt needs to be rerouted, the most popular is the John D “Power Wrap” method, along with a special grooved pulley used in place of the one supplied in the kit. This will bring the slippage down to an acceptable level. After all is said and done this kit can produce power in the range from 260-280hp depending on supporting mods. This is good for high 13's to low 14's in most cases. Not a bad setup, but by no means is it the end all of supercharger kits. The fact that this kit was the original and most produced is a great advantage for those looking to pick up one used. These kits are seen for sale used on V6 F-Body sites and Ebay regularly for $2000-2500 so it can be a cheap way to go to gain about 100hp.

The Powerdyne does have some options for upgrades of the actual unit that can both increase reliability and power. Though these are not offered through Powerdyne they are most definitely viable options. First there is an upgrade for stronger bearings and a stronger internal belt. This will allow the unit to be used for more boost than the stock version. The second modification is a shimming of the blades that puts them in closer proximity to the inducers wall. Compression is more efficient, thus producing more boost. The last mod for the blower is to have breathers installed. This allows the supercharger to circulate air near the bearings, allowing them to stay cooler and last longer.

ATI P1SC kit

The ATI based kit is available from Mach Performance. It’s a very well built kit that includes everything needed to install the supercharger, it also includes an intercooler and a tune to maximize power output. The kit is based around the P1SC which is a fully contained gear based unit. It has its own oil supply, so there is no need to tap the oil pan. It is available with different boost levels and will be more than enough for the average user. Power levels should be expected to be around 300hp. The higher boost kit comes with larger injectors, which is a big plus. All in all this is a very well designed kit. The biggest drawback is that it costs more than $4000.

TURBOCHARGER SYSTEMS

At this time there is no company that is selling off the shelf turbo kits for the V6 F-body. That means that you need to find a used setup, or create a custom system on your own.

The Turbo

One of the black arts in forced induction is striking the balance between power production and spool when a turbo is selected. For example, a huge compressor will be efficient at high air flows and pressure ratios, but may surge in day to day operation and take forever to reach boost threshold. Or perhaps you want quick spool and select a very small turbine. Exhaust pressure at higher boost and rpms may become choked off due to the restriction of the wheel.

When selecting a turbo for your application, the first step is to either learn how to read compressor maps and calculate consumption, or talk to someone who does. While it is preferable that a person learn how to do things for themselves, sometimes maps aren’t readily available and some first hand experience from a turbo manufacturer or a race shop can be helpful.

After you have found a compressor that meets your power goals, half of the work is finished. You must now size the turbine. There are turbine maps out there, but they are even more difficult to find than the compressor maps. As a guideline, consider a T3 style turbine for a 3.1L, a larger T3 or small T4 for a 3.4L, and a T4 style for the 3.8L.

All in all the author recommends starting with a moderate sized turbo and working up to a larger unit as you refine your setup. Stick with a T3/T4 hybrid or a straight T04E series on a 3.1 or 3.4L and perhaps a straight larger T04E or T04B series for the 3.8L. It is the authors opinion that a T04B 60-1 compressor will probably meet or exceed the needs of most individuals looking to add a turbo to their vehicle. If you plan to run twins, than size each turbo for half of the airflow but the entire pressure ratio that you plan to run. T25s or even T3s are plentiful on imports and may make decent choices for a twin system.

The Hot Side

Now that you have found the cornerstone of your turbo system, it is time to figure out how to get it spinning. The two main strategies for creating a hot side have thus far been a reversed y-pipe reusing stock manifolds or off the shelf headers, or custom forward facing manifolds.

The stock manifolds are cast iron and will be stronger than almost anything that can be created custom within a reasonable price range. The cast iron should retain heat better than aftermarket units or custom jobs, all things being equal. The stock manifolds may be the best choice for a twin system if you can hang the units close to the flange.

Off the shelf headers are available and will flow more than the stock manifolds. They may not retain heat as well unless they are ceramic coated. Also, increased diameter primaries and secondaries can delay the exhaust pulses and create slower spool.

Forward manifolds have the potential to reduce exhaust piping length and increase spool. They will not be as strong as the stock manifolds. Correct sizing remains somewhat controversial. It is wise to either ceramic coat or heat wrap them to retain heat within the exhaust.

The log manifold has been somewhat shunned within the community as most expect a header style manifold with individual primaries to outperform a log. However, since we are dealing with a V6 that fires on one bank and then the other, the overlapping pulses that are a concern on a V8 do not apply. Also, because there are no primaries, the total length from the exhaust valve to the turbine should be minimized with this system. A log should also be easier to design and construct than a header style manifold, and may be easier to tuck close to the motor and save some space within the engine bay.

Another engineering bit to consider, especially for a forward facing system, is that of a divorced exhaust route. In this case the exhaust pulses from the two banks never meet before they reach the turbine. This should prevent the pulse from one bank from being reflected back through the other bank and interfering with an oncoming pulse.

Since the wastegate is part of the hot side, it will be discussed here. If you selected a turbo with an internal wastegate, you may skip this section. The Tial 38mm unit is a popular choice among V6 turbo cars, but any other comparable unit should work. The wastegate should be positioned such that it can divert enough exhaust such that the rpm of the turbo are controlled and you do not over-boost. The wastegate spring selected should equal the desired boost range unless a boost controller will be used. The reference pressure for the wastegate is typically the charge pipe right after the compressor, although some people reference the unit off the intake manifold itself. You can either have the wastegate dump to atmosphere, or route back into the exhaust post turbine to keep it quiet.

A boost controller allows you to alter the boost pressure that the wastegate samples. For example, if you are using a 5psi spring, the boost controller may be adjusted so that the wastegate does not see that 5psi until the actual manifold boost pressure is 7psi. The boost controller may be either manual or electronic. The actual installation of the boost controller should be performed by following the instructions that come with the wastegate and boost controller themselves.

The last bit of the hot side is the down pipe and the exhaust. A 3 inch downpipe is more than adequate for the needs of most on this site, and in fact some prefer to run a 2.5 inch downpipe. The size of the downpipe will depend on the desired power level, but it should also be influenced by the outlet size of the turbine so as to minimize turbulence.

The Cold Side

Compared to the hot side, the cold side may seem like cake. Run an air filter to the turbo via some tubing, and then create pipes that run from the outlet to the TB and you are done.

There is a little more thought that should go into the system. Match the pipe diameter to the outlet of the compressor. Try to minimize the length and the number of bends within the pipe. Either weld the pipe or use quality silicone couplers to connect each section. If you plan to run an intercooler, your piping will be slightly more complicated and of greater length.

Also worth considering on the cold side is a blow off valve, especially for manual cars. Typically you want to mount the valve close to the throttle plate, or at the very least after the intercooler if you are using one. The vacuum source for the BOV should be the intake manifold.

Oiling

One of the most important considerations for a turbo system. Unlike the supercharger options, there are no self contained turbos that do not require an oil system. Your options are to either tap into the engine’s oil system, or create a dedicated oil system for the turbo. Most elect to tap into the engine oil system via a T at the oil pressure sender, and return the oil by gravity drain into the oil pan. A 3/8 inch feed and 5/8 inch drain size are usually adequate. You probably want to use stainless steel lines for the oil feed and drain, as they can take more temperature and survive the oil unlike most rubber line that is readily available.

If you elect to create a self contained supply, you will need a pump, a reservoir, and the lines. Since nobody on the V6s has elected to develop something like this, there are no pictures or cookbooks to follow.

GENERAL FI GUIDELINES

FI Fueling

The fuel system should be modified when FI is added to the vehicle. At the very least an FMU can increase the amount of fuel the stock injectors can supply. Typical FMU ratio is 6:1.

Eventually you will run into dropping fuel pressure due to the pump running out of flow. You can either replace the in tank pump with an aftermarket unit, or add an inline pump. The inline is much easier and often times cheaper than the in tank. It will be louder and less efficient than an in tank, however. The in tank option is typically preferred. It is generally more expensive and more time consuming to install. You can either drop the fuel tank or create an access panel in the hatch.

The fuel injectors will need to be upgraded after the FMU is no longer adequate, or at the beginning if you wish to forgo an FMU. Properly installed and tuned injectors should be more reliable than an FMU, although injector failure is possible. Unfortunately for later model cars, there are not many injector options that are plug and play with the Multec fuel injector connectors. There is a 42pph Multec type injector available, but it is shorter than the stock injectors and will require an earlier shorter fuel rail or modification to the fule rail. Alternatively, injectors of the correct length may be installed as long as the Multec connectors are replaced with Bosch style connectors.

Tuning

With any forced induction it is wise to invest in tuning software, such as HPTuners. A properly tuned car will be safer, faster, and get better gas mileage than a poorly tuned car. Unless you have experience with tuning, you may wish to let a professional tune your car on a dyno. More tuning information is available in the PCM forum on this site, and at some of the links at the end.

Intercoolers and Alcohol Injection

Contrary to popular belief, an intercooler is not an absolute requirement for FI, and may not always increase performance. While a lower intake charge allows you to run more boost for a given octane, the pressure drop cause by the intercooler can push you back to square one by reducing available pressure at the intake manifold. In order to see the boost you want, you may have to adjust the wastegate or change the pulley. But by increasing the boost you increase intake charge temperature, etc.

If you are using a Powerdyne, try to find an intercooler with minimal pressure drop if you are set on running one. The PD can be run at 9 psi on pumpgas without an intercooler as long as timing is controlled properly. The Mach Kit comes standard with an intercooler, and there are perhaps gains to be made if you can find a more efficient intercooler.

The same principles hold true for intercoolers on turbo setups. If you are happy with 5psi, you may want to forgo an intercooler. But if you want to go above 9, you should more strongly consider some sort of cooling option.

The other option for cooling the intake charge is alcohol injection. For more info and to purchase a system, visit Devil’s Own (a sponsor). When it is injected, the alcohol vaporizes and removes heat from the air in the intake. Alcohol will lower intake temperatures and increase effective octane. You can also just inject water to cool the intake charge, but it is non combustible and acts as a bystander in the cylinder as opposed to a fuel. Lastly with regards to lower intake temps, nitrous oxide injected into the intake will lower the temperature of the charge as well. However, care should be taken so that you do not run lean or increase cylinder pressures beyond the safety margin of your motor and fuel system.

FI Peripherals

There are several things that must be done before installing a supercharger or a turbo. On our cars, the PCV draws fresh air from the throttle body. This works well on an N/A car that never sees positive manifold pressure. When you pressurize the intake, the flow reverses and you can pressurize the crankcase. Most people plug the hole in the TB with either JB Weld or by using a tap and plug. You must now create a source for the PCV to draw fresh air. The easiest is to get a filter breather and put it on you valve cover in place of your oil fill cap. This is simple and will work but will also allow for blow by so it is not optimal. Another option is to drill little holes in the TB along the bottom where the PCV vent runs towards the opening within the TB. Alternatively, some sort of catch-can based system could be engineered, but there are no examples at this time.

Spark plugs should be 1 heat range colder than stock (NGK TR6 or Autolite 103's will work), and then they should be gapped to no more than .045 (.042- .035 is the most common range) to prevent them from getting blown out.

The gauges that you choose will depend on what information you wish to display. However, it is probably wise to have at least a boost gauge and a fuel pressure gauge. If you have the capability, a wideband exhaust O2 or air-fuel ratio gauge would be nice. Alternatively, EGT may be an alternative.

The Motor

You can make a lot of power on a stock motor with some boost and adequate fueling and tuning. The author believes that it is wise to dial in the rest of the car (chassis, drivetrain, suspension) before huge motor mods are attempted.

When it comes time for the motor, a few guidelines are as follows. You do not want to jump to the lowest compression possible. The stock compression ratio of the 3.8L allows good performance outside of boost, and is also adequate for most boost levels on premium fuel. If you jump to a low compression ratio, performance out of boost will suffer but you may have a greater tuning window at higher boost levels for the same octane fuel.

The cam should be chosen based on the form of forced induction. Superchargers like minimal overlap with high lift and duration. Most prefer more exhaust duration on a supercharged motor as the intake flow receives help from the supercharger and the exhaust must fend for itself.

The cam on a turbo car is more complicated. Traditionally, reverse split cams with smaller exhaust duration where used to increase exhaust velocity and spool. The stock cam is very good for a turbo application, however. If you wish for added performance in the future, you may wish to discuss your setup and goals with a professional.

Valve springs should be adequate to support the added pressure on the valves, in order to prevent float at higher boost.

Everything else on an FI car

A setup is only as good as the weakest link, meaning that you can have a bunch of power but it is worthless if you cannot control it. It is important to remember that the FI system and the motor are only one piece of the puzzle in a performance car.

For the suspension, you must decide if you are going to build a dragster or a road racer. While a road race suspension will be ‘adequate’ for drag racing, a drag suspension will be horrendous for handling. The main point is that a stock suspension should not be expected to perform well at either job, and so should be modified to support the added power.

The drivetrain will require some modification as well. Clutches will need to be upgraded in a manual car, and an auto will benefit from a stall and a shift kit. Rear gears should be matched to your power curve. A centrifugal blower car should consider lower rear gear ratios, whereas a turbo car will need to balance a shorter ratio with the greater load a higher gear places on the motor.

The exhaust system should be adequate to support your power levels. For supercharged cars, headers are recommended. On turbo cars the downpipe should be sized properly and the rest of the system should be able to support the power level.

Links

Grayman’s Supercharger and FI resource:
Link

TurboV6Camaros site, lots of information:
Link

Wastegate function
Link

Garrett’s Turbo information
Turbo 101 Basic
Link
Turbo 102 Advanced
Link
Turbo 103 Expert
Link
FAQS
Link

FI Registry
Link

Spark Plug thread
Link

What Turbo thread
Link

The Classic MP70 Thread
Link

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