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Now it's time to poke around the engine compartment to get a sense of where the turbo is going to sit, how it is going to be supported and where the intake pluming (including the plenum, air filter position, etc.) and exhaust plumbing are going to run. Now would also be a good time to see if you could fit an air-to-air or air-to-water intercooler either in the engine bay or front-mounted behind the bumper or airdam if you plan to use an intercooler or are open to the possibility of using one in the future (more on intercoolers within the intercooling topic). The important part that you need to establish here is the turbocharger size, mounting and positioning that is allowed by physical constraints of your engine and engine compartment layout, as these considerations will be part of the criteria in choosing a turbo. Know what size a turbo (in physical dimensions, such as 8 inches long by 6 inches high) you can fit between the engine and firewall and other obstructions that cannot be relocated. This criteria will limit the size of turbo you will be shopping for. During this stage, take into consideration how you are going to attach the exhaust manifold to the turbo, as this will affect how much space you have for the turbo. Your options are that you could chop the outlet end off the existing manifold and weld on an adaptor that is flanged to fit the turbo (providing that the cut manifold outlet's shape fits within the adaptor), or fabricate a bolt-on adaptor that goes from your existing manifold outlet to the turbo inlet (this is a clean solution, but uses up a lot of space and/or requires the turbo to be located quite a ways from the cylinder head) or, as in my situation, fabricate your own turbo header (more on this in the fabrication section). Next, look for a spot where you could bolt a self-fabricated turbocharger mounting bracket to. I strongly recommend having one if at all possible (OEM turbos almost always have brackets for a reason), as hanging a 20-40 lb. turbo off the exhaust manifold alone (which expands and contracts and is greatly heat stressed) is a risky proposition to both the structural integrity of the manifold and its sealing ability against the cylinder head. The bracket should mount to the engine block or other part of the engine that moves along with the engine flexing; it should not mount to the firewall or any other part that does not flex with the engine, otherwise the turbo will will want to resist the engine's flexing under hard acceleration and put a lot of stress on the exhaust manifold and manifold studs. Consequentially, you'll want to buy a turbo that you could easily bolt the bracket to, but should not be a concern as most turbos allow for this. Finally, determine where the exhaust inlet and intake outlet of the turbo need to be positioned, and hunt for a turbo that reflects this need. Some turbos can be reclocked with minimal work; reclocked meaning that the the turbine/compressor housing can be rotated so that the in/outlets can point in whatever direction you need them to. Not all turbos allow for this, so its up to you to find out if the turbo you are interested in can be reclocked if you need it to be. Also, make sure that you have room to route the coolant and oil feed and drain lines to and from the turbo, and that they will be away from the exhaust manifold. Make sure that the oil line feeds into the turbo's center section from the top and drains out the bottom, as most turbos' oil passages are designed to be gravity drained. The install section will tell you where the lines should come from and where they go to help you plan their routing.
Here is a basic list of items to give you an idea of what you'll need for the turbo kit. It is by no means comprehensive, as different installs differ in need. The fabrication and install section will give details as to why these components are needed.
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Material to build intake plenum. This can be made from 4-6 mm thick steel or aluminum, or around 5-10 mm thick fiberglass or even carbon fiber (beyond the scope of most budget setups). One could also cleverly modify a metal or plastic tank that is of the right shape and suitable for pressure into a plenum. The rule-of-thumb for intake plenum volume is that it should be 110-120% of your engine displacement.
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Galvanized mild steel or aluminum tubing (more expensive, but lighter and polishable) for intake piping, including straights and bends depending on your application. Easiest place to get mild steel tubing in straight sections and preformed mandrel (smooth, unkinked) bends are industrial supply shops like Acklands Grainger or Gregg Distributor (Canada only). Ask for the galvanized exhaust tubing and preformed bends (the tubing I used is made by a company called Nelson, I believe). Mufflers shops may also carry these tubes and bends, or could crush bend straight tubing for you if you don't mind the small performance loss of kinked bends. Also, you need rubber or silicone couplers/reducers and some hose clamps to join pipe sections. Silicone is more expensive but more durable by far. You could use radiator hose of the right inner diameter (ID) if your budget is tight, as silicone couplers are usually the territory of specialty hop-up shops and thus expensive. Baker Precision and Hose Techniques, amongst many, sell silicone couplers.
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Cone/pod shaped foam/paper/cotton element air filter such as K&N or UNI brand filters. You could find cheap, used ones on Ebay quite often (where I find a lot of my parts). Alternatively, you could cleverly relocate and use your stock airbox or use an airbox out of a fuel injected car if it works out to be cheaper than an aftermarket filter, but since the aftermarket filters are usually cleanable/reusable and are easily installed (just clamp onto intake tube end), I recommend aftermarket filters.
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Fuel pump out of a fuel injected car, possibly new fuel lines and fittings to withstand the much higher pressures and a boost-referenced fuel pressure regulator from specialty manufacturers like MSD, at hefty specialty prices. Better yet, get an adjustable fuel pressure regulator out of a post-1968 Bosch D-Jetronic fuel managed car. These include:
VW Type III 68-73, Porsche 914 70-76 1.7L or 2L, Saab 69-74, Volvo, Renault 72-74. Bosch part # 0 280 160 001. You can get these brand new from the dealer for much less than the specialty ones, or dirt cheap used or from a junkyard. All you need to do is modify it to reference boost (more in fabrication section). -
A blow-off valve, also called a anti-surge valve, is needed for blow-through setups to relieve a pressurized plenum in the event of sudden throttle closing. If this pressure is not relieved, it will pressurize the float bowl of the carb and force fuel into the engine and flood it when the throttle is shut. BOVs are a very expensive item if you go with the trendy racing stuff. I recommend that you get a Bosch brand BOV that comes stock from a late model turbo SAAB vehicle, as these are inexpensive even brand new from factory and will flow enough bypass boost to fulfill your needs unless you are going for power levels beyond that of a budget setup.
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Boost gauge and fuel pressure gauge. Boost gauges can be expensive even used if you go with dedicated performance stuff. You can go with what I did; I just got a Wika standard air pressure gauge from Gregg Distributor for around $20 Cdn. (if I remember correctly) that is back-mounted and reads from 0-15 PSI. They come in 0-30 PSI as well for those of you planning on running high boost, as well as different mounting options such as panel mounting, etc. (here's a PDF catalogue page of what is available along with part numbers, you'll need Acrobat Reader to view it). They also need a pressure line kit; and for that I got the 6' Stewart Warner kit (also from Gregg, pt#82553-F) for around $25 Cdn. (relying on memory once again), but you could easily make one yourself by buying the necessary 1/8" NPT fittings and hose barbs along with some tubing. The gauges are not backlit and are pressure gauges only, thus will not read out vacuum like dedicated boost gauges will, but all you really need it for is to verify boost pressure from the cockpit anyway. As for fuel pressure gauges, ones that read from 0-15 or 30 PSI are cheap to buy used or even new (I got mine used for $15 U.S. on Ebay), as these gauges are only for use on carbs (fuel injected pressures are around 40 PSI on stock NA cars), thus not many people want these gauges. You'll also need a 3-way threaded tee-block (available at big chain parts stores or hydraulic/industrial supply shops) to run the fuel pressure gauge inline with the carb fuel feed line. At this point, it is a good idea (though not necessary) to buy a new factory fuel filter and/or run an aftermarket inline filter made for fuel injected cars. This may be a necessity if your factory fuel filter proves to be too restrictive to flow the higher amounts of fuel (which may cause your engine to run lean and detonate), in which case you must get rid of the factory filter and use a higher flow unit.
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Mild steel or stainless steel used for exhaust manifold fabrication/modification and down pipe fabrication. For the flanges, get some 3/8" - 1/2" thick mild or stainless steel plate, along with some 1/8" or 3/16" plate if you need a build a box-style collector section to join the tubes right before the turbo. Plate steel is commonly found at metal supply stores or even scrap yards, just make sure it is flat. As for the tubing, the cheapest and easiest route would be to use weld-joined hydraulic piping known as weld-els. You can get these at industrial and hydraulic stores like Acklands Grainger or Gregg Distributor and are not expensive. They come in both mild steel and stainless, with stainless being more expensive but offering better temperature and corrosion resistance. They come in a variety of diameters and shapes (straight, 45 and 90 degree short and long radius bends) and are beveled at the edges to form a nice filling channel for welding when the tubes are joined (click here to see what they look like). If you want the mild steel ones, buy the "schedule 40 NSP" grade ones in whatever diameter you need (see choosing components below); they are thick-walled and thus can survive the high heat of turbo duty. For the stainless ones, the most cost effective grade to get would be "Schedule 10, 304 stainless" grade material. You could get thinner walled stainless weld-els that would still withstand the heat if you move up a grade to 321 stainless, but the cost begins to rise as you move to higher grades. Keep in mind that you could weld mild steel flanges to stainless steel tubing and vice versa, so its not all or nothing in terms of which metal to use. If you want to keep costs down but still want the heat and corrosion resistance of stainless, go with the mild steel flanges and stainless tubing.
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A muffler, resonator, flex joint, exhaust tubing and bends, hangers, and catalytic converter(s), etc. will be needed if you run a whole new low-restriction exhaust. Depending on the legalities of your local public roads, race sectioning bodies and/or personal morals, the setup and cost will entirely depend on you, but I believe that a good performing budget system will run between $100-$500 Cdn. The most costly components will be the muffler and the catalytic converter, but these are not expensive if you avoid dedicated race stuff and shop around, especially for used parts.
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Of course, a turbo. For tips on what to look for in a turbo, see choosing components topic below.
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A boost controller. Again, very expensive ($300+) if you go with race stuff, so I recommend buying the manual, homemade type like this one easily found on Ebay for around $10 U.S. These are essentially tee-blocks with a ball-and-spring type valve inside and a screw running into the tee to adjust spring preload and therefore relief pressure that is used to open the wastegate. Thus, you can trick the turbo into running higher boost until the relief valve opens up at the specified pressure to allow the wastegate to open and control boost. You could just as simply make your own from a pressure relief pop-type valve available from Acklands Grainger, and then following the instructions on this site. However, I find it is cheaper and more convenient to get a cheap, homemade boost controller from Ebay.
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Various oil lines and coolant lines (specifically for the turbo feed and return), fasteners, hose clamps, fittings and hose barbs, etc. You may need to run all new fuel feed and return lines running from the gas tank to the carb (feed) and back (return) if your feed and return lines are too small, as this will restrict flow and wreck havoc on the pressure regulator's ability to regulate fuel pressure and causing all sorts of nightmares. A good size is 3/8" for return line and 5/16" feed line; this should flow adequately for healthy amounts of power. If you need new lines, be sure to buy good quality high pressure lines designated for fuel and that you adequately protect them when running these lines under the car.
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Possibly an aftermarket carburetor (and corresponding adaptor for your intake manifold, or fabricate one yourself) if your stock one proves too restrictive or if no parts to rebuild it and tune the fuel curve exists. Guru Corky Bell does not believe that turbocharging on a stock carb is possible, but I have heard of it being done and other experts such as Hugh MacInnes seem to state it is possible and that good performance can be attained, as long as the carb is flexible in tuning. I recommend getting an aftermarket carb anyway, as they are very tunable and rebuildable and are cheap and easy to find if you go with something like a small double-barrel downdraft. I recommend getting a progressive carb (one that uses one throat/barrel at low engine speeds, then opens up a secondary throat for higher speeds) with a mechanical progression linkage (as opposed to a vacuum operated one), as this type of carb seems to be favored by many enthusiasts. Pick these up used at vintage car clubs or on Ebay. Weber, Mikuni, SK, Dellorto and Holley seem to be the brands of carbs that experts favor, claiming that they are very tunable, respond well and can withstand (with preparation) the rigors of turbocharging. Whatever carb you go with, you need to have a tuning kit with an assortment of jets (or drills to drill out the stock jets, a cheap but risky proposition), emulsion tubes, accelerator pumps, etc. to tune your fuel curve via educated guessing and trial and error.
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Possibly need upgraded ignition coil, distributor, wires and spark plugs that are one range colder than stock specs. Chances are your old ignition components are in need of reconditioning anyway, and turbocharging requires a hotter spark to light the denser charge than does NA. If your existing ignition system seems to do the job fine, then great. Otherwise, if there are problems under boost (plug fouling, over-rich smelling/looking exhaust), look to upgrading the ignition components.
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Carburetor rebuild kit (not necessary but highly recommended) along with some possibly needed metal epoxy (like QuickSteel) to seal small bores and secure screws. Also may need some can-dispensed minimum expansion polyurethane insulation foam along with plumbing (not electrical) solder (both can be found at hardware stores like Home Depot) to fill hollow carb floats. Refer to install section to see if you need these items for carb preparation.
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Not necessary, but once again highly recommended, are: oil pressure gauge, water temperature gauge and exhaust gas temperature gauge. Oil pressure and water temperature gauges are excellent warning devices that could save your engine, and factory ones are usually non-existent or inaccurate in older, carbureted cars. These are not expensive if you go with the generic Equus or Sunpro brands from big name auto parts franchises (even Wal-Mart carries these). Exhaust gas temp. (EGT) gauges are an invaluable fuel tuning tool as EGTs are the one of the best indicators of proper air/fuel mixtures. Unfortunately, EGT gauges and thermocouples (temperature probes) dedicated for automotive use are very expensive even used; I recommend you scout for ones used in ultra-light aircraft at salvages and surplus sources or Ebay.
The two most critical components that need to have their specs chosen in the planning stage are the turbo and the material to modify/fabricate a manifold.
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Choosing a turbo: The most important factor in choosing your turbo is that you choose one that matches your engine and your purpose. Turbo-to-engine matching is widely purported to be the most important aspect of the system's design. Finding the perfect turbo for your engine involves a little math work, and I find this is only useful if one is shopping for big-dollar aftermarket turbos, which of course is out of the scope of a budget setup. Budget setups are limited to using OEM turbos that offer no options in customization (different compressor/turbine trims and housing) other than the modification options offered by turbo specialty shops, whose services could easily cost more than the car to be turbocharged. Luckily, there is a quick and dirty method to turbocharger matching offered on the Ray Hall Turbocharging website in the form of Applet Calculators. Use the TurboMatch calculator and input your engine's data to find a good recommended Garrett brand turbo, and then search for an OEM turbo close to that recommendation that also fits the criteria you have identified in the layout phase above. Pay attention to the A/R ratio that the applet recommends, and look for a turbo from a car with similar engine displacement and A/R ratio. The A/R ratio of a turbo is usually stamped on the inside of the exhaust housing turbine inlet, right along the edge near the flange. You may need to rub a piece of chalk against it to read it, as chances are it may be encrusted with carbon and hard to make out. Remember that smaller A/R turbos will spool up faster and have great response but may choke off power at high engine speeds due to exhaust restriction and may even over-boost, while larger A/R ratios may be sluggish to spool but will offer better high-end flow exhaust flow; however too large an A/R may lead to low boost. Stay close to the recommended A/R ratio you get from the TurboMatch applet, and if in doubt, go with the slightly bigger A/R turbo when shopping around unless quick spooling and minimal turbo lag is your only design objective. This is a sufficient but very simple method of turbocharger matching, and I simply cannot do this science justice with this small write-up. If you want to learn more (and I suggest that you do) about turbo matching, such as how to read compressor maps and what they mean and what exactly an A/R ratio is, I highly recommend you get you hands on the books I have listed on the Links page, or at the very least check out some of the sites listed or ask around on the message boards that I have linked.
As for shopping for the turbo, you might want to check self-serve junkyards, used parts in classified ads, car clubs, or Ebay (though you have to be careful about this one as you cannot know for certain the condition of the turbo until after you have bought it). If you have a bit more to spend, you could get used units from turbo specialty shops and auto parts recyclers, as these places usually offer the best warranties. To check the condition of the unit, first see that there are no chips, cracks or bent fins in both the compressor and turbine wheels. Next, grab the center securing nut on the compressor wheel and spin the wheel. It should spin without binding at any point in the rotation and should spin freely, but not to the point of the wheel continuing to rotate after you have let go. Now grab the center nut again and pull back and forth, then shake up and down. There should be optimally no noticeable play in either direction, but a very small amount (around 1 mm or less) is tolerable, especially since you are shopping for cheap used turbos. Next thing to check is if the insides of the compressor housing and/or the intake tubing of the donor car (if available) are coated in oil. A thin coat is ok, but if it is dripping then that might be a sign of failed oil seals in the turbo. Check the exhaust housing for cracks; one or two small hairline ones not longer that an inch is still acceptable (depending on the price), but anything that will cause exhaust leaks is a definite no-buy. Next, use a screwdriver to pry the wastegate open on the exhaust housing side to ensure it is not seized shut. A seized wastegate would over-boost and could destroy your engine in short order. Finally, though not often possible, find out about the turbocharger's history, particularly the turbo's mileage (this may or may not be the donor car's mileage) and the history of the donor car's usage and maintenance records. Turbos with mileage around 150,000 km (around 100,000 miles) are suspect to needing rebuilding (which costs around $500-$1000 Cdn.), but this really depends on how well the donor car was maintained and how it was driven.
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Choosing exhaust manifold/downpipe tubing: If you are modifying your stock cast iron manifold or making an adaptor to fit a turbo, then thick mild steel is the material to use. If you are fabricating a manifold (or if your adaptor is long and complicated) then let your budget and intended purpose of the car guide your decision between either stainless or mild steel. The mild steel tubing recommended above in the parts need list will suffice, but if the car is intended for severe duty (such as hill-climbing or road racing) and/or you operate the car in environments highly corrosive to metal (salted winter roads, high humidity, etc.) then you might want to spend a bit more for stainless steel for the sake of longevity. For those fabricating a manifold, there are two designs to choose from: Log type and equal length. Pictures of each offer the best description, so click here to see the difference in design. The log manifold is simple to construct and offers good performance, however the equal length manifold theoretically yields the best performance at the cost of complexity in fabrication. For the internal diameter of the exhaust manifold primaries, go as close to the stock diameter of your existing manifold as possible. When in doubt, use the smaller diameter, as bigger is not always better in the case of exhaust manifolds; you want to maintain good exhaust gas velocity through the manifold to get good response from the turbo. As for the length of the primaries for an equal length setup, either try to aim for as close to stock as possible if all else fails, or go for as long as you can fit if you want low-end torque (around 12- 18 inches is a good size), or short (around 6-8 inch) if you want high end power. Many would say that this length analysis only applies to NA engines, however I (and many turbo experts) believe that intake and exhaust tuning principles can apply to both turbo and NA engines and are equally important in both. Exhaust manifold tuning theory is extremely complicated and I will not go into the details of it here, but if you want to learn the basics, a company called Burns Stainless has a good info on their tech page. As for the downpipe, choose the material with the same criteria as you did for the manifold. The diameter should be as big as you can fit (this is highly contraversial) as you want minimal backpressure after the turbo; this helps the turbocharger's spool up characteristics and overall efficiency.
When you have all the parts you need, the next step is fabrication.