This information comes from the old Greddyfaq.com site. The site has changed considerably (looks like it was sold) so this info is not posted there anymore – so hopefully this will keep it available. I’ll use this in a HOWTO: document I am knocking together also but wanted to get it out for anyone who may have just grabbed a turbo off trademe
I have pulled this from archive.com so the links should still work.
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Contents:
IGreddy turbo kit basics
1 Overview of the Greddy turbo kit
2 What is included with the Greddy turbo kit?
3 What will the Greddy turbo kit do for me?
4 How does the Greddy turbo kit compare to other kits on the market?
IIUpgrading the Greddy turbo kit for more power
1 4.5 - 6 PSI boost levels
2 6 - 8 PSI boost levels
3 8 - 10 PSI boost levels
4 10 - 12 PSI boost levels
5 12 + PSI boost levels
IIIModifications you can (and sometimes SHOULD) make to the Greddy turbo kit and your vehicle
1 Exhaust manifold relief cuts
2 Knock control/ignition retard control
3 Adjustable fuel pressure regulator
4 High pressure fuel pump
5 Fuel injectors
6 Boost control
7 Intercooling
8 Intake configuration
9 Blow off/air bypass valves
10 Gauges
11 Clutch
12 Exhaust system
13 Nuts, bolts and fittings
14 Heat shield
15 Programmable ECU
IVWhere to purchase new/used parts for upgrading the kit
I Greddy turbo kit basics
1 Overview of the Greddy turbo kit
The Greddy turbo kit is an aftermarket system manufactured by Greddy for the 1.6 liter 1990-1993 Mazda Miata. The system is California carb certified and runs about 4.5 PSI of non intercooled boost in stock form. The addition of the kit will require the use of high octane (92 or greater) fuel in order to prevent detonation which can damage your engine.
2 What is included with the Greddy turbo kit?
The Greddy turbo kit is based around the Mitsubishi TD04H turbocharger. This turbo is pretty well sized for the 1.6 liter motor and versions of this turbo have been reported to have been used in the Mitsubishi Eclipse. The kit includes a cast iron exhaust manifold, the Mitsubishi TD04H turbocharger, a downpipe which connects to the stock Mazda Miata downpipe just in front of the firewall, two cast aluminum intake pipes, air filter, oil supply and return hoses, non adjustable Vortec rising rate fuel pressure regulator, fuel line, gaskets that go between the turbo unit and the manifold and between the downpipe and turbo, and various nuts and bots for securing the parts.
3 What will the Greddy turbo kit do for me?
The Greddy turbo kit is designed to run about 4.5 - 5 PSI with the parts included. This will result in about 40 more horsepower delivered to the rear wheels. Stock 1.6 Miatas tend to produce about 90-100 horsepower measured at the rear wheels. With this kit you will produce between 130-140 horsepower at the rear wheels depending on your vehicle's state of tune. Torque will also be increased to between 120 ft lbs and 130 ft lbs at the rear wheels.
4 How does the Greddy turbo kit compare to other kits on the market?
The Greddy turbo kit really doesn't have any direct competitors in the market as this point in time. It is designed to be an inexpensive, low boost system and is meant to give the Miata a nice boost in power without alot of fuss. At 4.5 PSI in stock form it makes less boost (and therefore usually less horsepower) than competing systems from Bell Engineering and Flyin' Miata, as well as the Jackson Racing supercharger system. Like most turbos, the physical turbo unit is capable of producing much more than 4.5 PSI however other modifications will be needed to be made to the supporting systems to ensure the same level of safety and reliability. I will detail those modifications in the next section.
II Upgrading the Greddy turbo kit for more power
1 4.5 - 6 PSI boost levels (estimated 130-155 HP)
At the stock 4.5 PSI of boost the included components with the kit work quite well. There is adequate fuel being supplied by the stock Miata fuel pump. The included fuel pressure regulator, while not adjustable, is designed to run a bit on the rich side in the name of safety. However at this boost level, the arm that controls the wategate tends to be on the loose side and can rattle. Also, if left loose, this can cause damage to the wastegate seat inside the turbo. See this picture for the location of this rod. By tightening this rod a few turns the rattle can be eliminated and the wastegate valve can be protected from damage. This can also have the side effect of raising your boost level early in the RPM range by allowing your turbo to spool faster if your wastegate was leaking. This rod may be tightened even more to raise the boost of the turbo to about 6 PSI. At this level, I began to approach the limit of my stock fuel pump causing a lean condition. Some folks report having no problems at this level, but it's something to be aware of. If this is the case on your car, it would be wise to add an auxiliary high pressure fuel pump to your car. See this section for more information about the fuel pumps available. At the preset level of boost (4.5 PSI) you are probably pretty safe without a knock sensor or ignition timing retard device. You will probably wish to run 6 degrees of timing on your car to avoid detonation (ping) if you do not have a timing control device installed. Installing a knock sensor or timing control will allow you to run more than the stock boost level and will allow you to run more timing advance (for more lower end power). See this section for those options.
2 6 - 8 PSI boost levels (estimated 145-170 HP)
Above 6 PSI I feel that it is needed to have an intercooler added to your system. And intercooler is designed to cool the intake charge between your engine, and the turbo. When air is compressed inside the intake tract, it is heated by both the compression, and the exhaust gasses that superheat the turbo itself. In this boost range there are several intercooler options available. See this section for information on those options. Also at this power level, it is mandatory that you have some type of high pressure fuel pump. Your stock fuel injectors should be ok in the 6 - 8 PSI boost range. The fuel pressure regulator included in the Greddy kit seems to do ok up do the 8 PSI level. You may want to upgrade to an adjustable fuel pressure regulator, see this section for more information on the AFPRs available. Your stock Miata clutch (depending on mileage) should still be able to hold the power produced at these power levels. It might be a good idea to check out the exhaust options. With a turbo system you are able to run extremely free flow exhaust designs with a minimum of noise increase due to the dampening effect that the turbo has on the exhaust. Your turbo will spool up faster and give a higher output with a high flow exhaust design. See this section for various options. At this power level it is critical to have either a knock control device, or an ignition retard device installed. See here for those options.
3 8 - 10 PSI boost levels (160-180 HP)
At this boost level we begin to approach the limit of the stock fuel injectors (I could not run higher than this level on my car, however I have heard from some folks that have gotten as high as 12-13 PSI on the stock injectors and they seemed to work fine. Watch your Air/Fuel ratiometer to see if yours are doing ok or not). On a 90-93 Miata it is possible to install the larger injectors from a 1.8 L 94-97 Miata to increase fuel flow. These injectors are not large enough that they affect the idle quality or run too rich. See here for info on that, and other injector possibilities. Also at this power level your stock Miata clutch will likely begin to slip in the higher gears. There are various options for clutch replacement and they are discussed here. At this boost level it is also very important that you have complete control over your fuel management. I highly recommend purchasing an adjustable fuel pressure regulator. You may see that information here. Also at this boost level, it is very important to have some type of free flow exhaust in order for the turbo to have room to push the massive amounts of air it will be forcing into the motor at this point. It is absolutely necessary to have a knock sensor or ignition control device at this level as well or engine damage will be almost a sure thing. It is also a very good idea at this point to close down the gap on your spark plugs some to decrease the change of missing at high cylinder pressures and run colder heat range spark plugs. Flying Miata recommends the spark plugs to be gapped to between .030 and .035 (stock gap is .040). I also recommend moving to the NGK ZFR7 range plugs (or similar). These are colder range plugs than stock and will keep the heat down some.
4 10 - 12 PSI boost levels (170-210 HP)
At this point it is a very good idea to have a fully programmable ECU to control the fuel and ignition. It is possible to run this amount of boost without this item, but it is walking a thin line. There are a few full replacement ECUs available for the 90-93 Miata...check out this section for these items. If you follow this path you will no longer need the AFPR, high pressure fuel pump, knock sensor or ignition retard device. However at this power level it is very important that you have an efficient intercooler to cool the superheated intake charge. Check out the intercooler section for that info.
5 12 + PSI boost levels (190+ HP)
The Miata engine seems to be able to take 12 PSI in stride. As high as 15 PSI is possible on the stock motor with very precise tuning. There have been failures at this level, so you must beware of those possibilities. At this level of boost, it is absolutely critical that you have a programmable ECU to control the action. A very efficient intercooler is also needed, along with a free flow exhaust. A very strong clutch is also going to need to be installed. Also beware that the Mitsubishi turbo seems to reach it's peak efficiency at around 12 PSI, as it's a fairly small turbo unit. I have heard of folks running up to as high as 16 PSI on the turbo though, but your mileage may vary.
III Modifications you can (and sometimes SHOULD) make to the Greddy turbo kit and your vehicle
1 Exhaust manifold relief cuts
Greddy exhaust manifolds have a reputation of cracking. See photos here, and here. There are things that you can do to prevent this from occurring however. The most important is the cutting of the manifold flange where it meets the head...between the 1 and 2 cylinders, and the 3 and 4 cylinders. It might also be a good idea to cut between the 2 and 3 cylinders as well. Here is a picture of this modification. These cuts go all the way through the manifold flange and basically divide the flange into 3 pieces...so they can expand and contract, move etc with the heat and not bind up and stress the manifold itself.
2 Knock control/ignition retard control
With a forced induction system on a car that was shipped from the factory naturally aspirated, it is necessary to control the ignition timing with an ignition retard device and have or have a device listen for knocks and retard the timing. The most popular (and possibly only) knock sensor on the market is the J&S knock sensor. It retails for $400-500 and it listens for engine knocking through a microphone mounted on the side of the block. When it detects knock, it retards timing up to about 20 degrees to prevent the knock from continuing. The J&S is also available with a software modification which will remove the timing based on RPM and throttle position (with the air flow meter signal) BEFORE the knocking starts. This is important because it takes more timing being removed to stop knock, than it does to prevent it from starting. Another popular modification is the MSD ignition retard. This device retards up to 6 degrees of timing based on boost level...usually one degree of timing per PSI of boost. This device retails for less than $200 but has no knock detection. There is also a popular mod for the MSD called the Bipes mod, which allows control of when and how fast the timing is removed based on RPM. This is device is sold from a private party. Both the MSD and the J&S are sold by various Miata.net vendors.
3 Adjustable fuel pressure regulator
The Vortec fuel pressure regulator that comes with the Greddy kit is not adjustable as it is delivered. Vortec does offer some bolt in parts that can modify the amount of fuel pressure increase per PSI of manifold pressure. More information on this can be seen on Vortec's page. There is an adjustable model available however. Bell Engineering (BEGI) produces the Cartech AFPR for about $200-220. This unit is adjustable for both rate of rise (the amount of fuel pressure increased per PSI of boost) and for base level (the amount of fuel pressure at 0 PSI). This gives much more control of the fuel delivery and can be used to tune out flat spots and other problems in the fuel system. This part can often be found used on the Miata.net classifieds.
4 High pressure fuel pump
The stock Miata fuel pump can only provide so much fuel...it was not designed for use with a turbo or supercharger. There are several options in the fuel pump market to remedy this problem. The most popular model is the Pierburg pump available from BEGI. This pump is capable of producing in excess of 120 PSI of fuel pressure...more than enough for any Miata application. The pump is priced near $200. Another option is the Walbro fuel pump sold by Jackson Racing as well as other places. This kit is probably good for up to 8 PSI of boost, but it does not seem to have the capability of producing enough PRESSURE to supply the small injectors with fuel. It would be a good option however if you need more fuel FLOW (if you have a programmable ECU for instance). Walbro does make a pump that would work well from what I've heard. The correct Walbro pump to use is the 255lph HP (HP stands for high pressure). You can get this pump for around $130 shipped. This pump is too long to fit into the stock 1.6 hanger (plug and play for a 1.8 though) so you'll need to throw away the rubber cushion, chop off the plastic tabs which engage the rubber cushion, shim the hanger end-piece, and then use a bunch of tie-wraps to secure everything in place. (Not pretty but works). Yet another option brought to my attention by John Daniels is the Bosch inline high pressure pump. He obtained this at a local parts store for $80 and makes 120 PSI of fuel pressure and he says it works quite well.
5 Fuel injectors
The fuel injectors that come stock on the 90-93 Miata have enough room to run about 8 PSI or so when using a high pressure fuel pump and AFPR. However above this level, the fuel pressure required to get enough fuel into the motor through the small injectors becomes so great, that the injectors actually lock. A very common modification is to install the larger injectors from a 94-97 Miata. These will provide you enough room to run about 10 PSI of boost with some tuning. If you are using a replacement ECU, the popular injector to use is the RC Engineering 440cc/min injector. Some people have also used the large injectors from the turbo Eclipses with some success. If you have used these, please e-mail (eric@greddyturbofaqs.com) me with more information. I have been informed that the stock ECU is capable of handling up to 270cc injectors with little problems. You will likely need to lower your idle fuel pressure some though to keep the air/fuel mix correct with the big injectors.
6 Boost control
In order to run more than 6 PSI of boost on the Greddy turbo, you will need to have some means of controlling the boost level. There are many aftermarket electronic controllers that run from anywhere between $300-600. There are also folks who have used mechanical bleed valves sourced from parts at hardware stores in order to raise the boost level. If you have experience with one of these, please e-mail (eric@greddyturbofaqs.com) me. Another option that Jerry Wellborn has used with great success is the addition of a wastegate "helper" spring. See this picture here (the arrow #3 points to this spring) to see this spring installed on his car. It works by providing more tension to the wastegate arm, holding it back until more pressure is pushing on the wastegate actuator before the wastegate can be opened.
NEW Another option is the Turbo XS boost controller. Here is a write up by Kilruf
7 Intercooling
If you are going to run higher than 6 PSI of boost you need to have some type of intercooler. There is one drop in replacement kit available from Flyin' Miata. This is the intercooler kit that I have installed on my Miata. The system comes with a 9" or so intercooler that is good for cooling up to about 12 PSI of boost. There is also a "racer" upgrade which includes a 16x8" intercooler for an extra cost. This system costs $1000-1300 and includes all plumbing, and an air bypass valve. Other Greddy users have had great success with designing intercooler systems themselves. A very popular option is obtaining an intercooler from a Starion/Conquest. This intercooler is large, and fits in the Miata mouth with little trouble. Another option is to install an intercooler from a SAAB 900 turbo. See Jerry Wellborn's pictures and descriptions here. See pictures of all these intercooler options on the intercooler page.
8 Intake configuration
Probably my biggest complaint about the Greddy kit is the ridiculous location of the air filter. This can be moved (with some work) to a location more accessible to some cooler air. See the pictures of my car before, and after I moved my intake. Also common is the replacement of the stock Miata plastic intake piping that Greddy uses in favor of a metal pipe...see pictures of that mod here. This can be a good idea because the stock plastic pipe can be a nuisance...often popping off under boost and can even crack due to the high temps that the turbo blows through it. John Daniels has also relocated his filter using the original Miata air box...just the top half with the filter attached to it. See this install here. This provides the turbo with a bit cooler air than it can get when trapped back in the corner by the clutch cylinder. There is no real step by step way to accomplish this however, so you'll probably need to fool with it for a while to get a system that you like. (Note: there may be inadequate room on cars with A/C and power steering to fit this type of intake system as the accessory pulleys and PS pump take up alot of space, limiting your options)
9 Blow off/air bypass valves
Turbos often suffer from a goofy noise that is caused by the pressure wave from the turbo smacking against the closed throttle plate when you shift, or let off the gas after a boosted run. In order to silence this noise, air bypass valves and blow off valves are available. If you are using the stock ECU, you have a few options. One option that is guaranteed to work is a bypass valve installed near the throttle body, that has the air vented back to a location between the air flow meter and the turbo inlet. Another option is to install an HKS super sequential blow off valve. The HKS SSBOV vents the air out into the engine bay, but unlike most blow off valves it does not leak at idle, a behavior that causes poor idle with other blow off valves on stock ECU'ed cars. Another blow off valve that has been reported to work very well venting to atmosphere with the stock ECU is the Bailey Motorsport EVO dumpvalve (picture here on GordyB's car) Yet another option (that I do not have experience with) is using a regular blow off valve, with a one way check valve installed in the vent tube. This keeps air from entering the system at idle, yet provides the air a way to escape during shifts. You can see pictures of all these options on the BOV page.
10 Gauges
Having a turbo system means being alert and attentive to your engine's operation. The best way to do this is with a variety of gauges. I highly suggest an air/fuel ratiometer, a boost/vac gauge, and a fuel pressure gauge (either mechanical with an extension hose mounted in the engine bay, or electric mounted in the interior). These three are a must have. The A/F gauge tells you the most important aspect of running a turbo, whether you have enough fuel or not. Other gauges that may be useful are exhaust gas temp gauges, volt meters, and oil temp gauges. All of these gauges are available from various manufactures like Autometer and VDO and are about $50. Intellitronix also makes an inexpensive air/fuel gauge available for around $35 from Summit Racing)
11 Clutch
If you're going to run over 8 PSI, you're going to need a stronger clutch. One that I personally like is the MAX-5 sold by Performance Buyers Club. It is rated to hold about 260 ft lbs of torque and should hold about anything that a Greddy owner could throw at it. It costs about $350 for the pressure plate, disc, and bearings. Another fav is the ACT. This clutch in 1.8 size (when coupled with a 1.8 sized flywheel from a 94-97 Miata) can hold anything even the most powerful Miata can throw at it. Recommended if you plan on running over 12 PSI.
12 Exhaust system
A free flow exhaust system does wonders to help a turbo Miata run fast. The turbo acts like a damper on the exhaust pulses, so it is possible to run a very free flow design without being too loud. A good exhaust will typically result in an increase of 1 PSI of boost (if using the mechanical controllers) and faster spool up. Results of up to 15 HP have been seen at 6 PSI. I have the FM turbo single exhaust installed on my car (available from FlyinMiata) and really like it. What you want is at least a 2.5" pipe from the cat back. Many folks have had custom system built with 2.5" piping and a turbo style muffler. High flow cat converters are also a good investment in a turbo car. There are a few different models available from makes like Flyin Miata, Jackson Racing, Rod Millen, and Random Technologies. It is also common for Greddy owners running high boost to replace the stock Miata downpipe with a larger 2.5" piece. I also recommend installing a flex joint in this new downpipe to take as much vibration out of the exhaust as possible before it gets up to the turbo. We plan to offer a 2.5" downpipe for the Greddy kit! Details here. Hear my FM exhaust on the sounds page.
We have just learned that the gasket included with the Greddy kit that goes between the exhaust manifold and the turbo can be replaced with a Nissan 300ZX gasket. Part number 14415-17M00. See here for a pic.
13 Nuts, bolts and fittings
The Greddy turbo kit comes with bolts that hold the turbo to the manifold and the downpipe to the turbo. I had problems with these bolts always coming loose often, and eventually had 3 of them shear in the manifold. To relieve pressure at the turbo, I bored out the holes in the turbo's flange a bit to give the bolts some room so the turbo could expand/contract and not squish them. I replaced all these bolts with studs, lock washers, and doubled up nuts on top. I have had no problems since this change. Also not addressed by Greddy (BEGI kits include this) is a check valve for placement in the charcoal canister vacuum signal line. This prevents the canister from being compressed and the valves can be found at any auto parts store. Another tip that might save some trouble down the road is adding a 1/4" or so hose clamp to the rubber cap on the back of the intake manifold to prevent it from blowing off. I have not done this however, I probably should even though I have had no problems yet with it. Here are two pictures of my stud/double nut/lock washer setup. 1 2. NEW. Here is a scan of one of my damaged bolts (before I drilled out the holes in the turbo a bit larger...you can see the threads on one side are completely flat where the turbo flange pressed against them). Also shown are the studs I have switched to with the lock washer and double nuts that I use on top.
14 Heat shield
Because of how high the Greddy turbo sits, I find it very important to make a heat shield to block the hood from the intense heat. It is reasonably easy to make your own. Here are a few pictures of heat shields on Greddy turbos. My car has a welded aluminum heat shield (thanks Scott!) as well as a 1500 degree heat blanket secured to the hood with some 3M trim adhesive. This keeps the hood very cool, in fact before I installed the shields the hood was almost too hot to touch after a hard run, now is it very close to the temp of the rest of the body after a hard run. Jerry's car had a nice compact heat shield made from a cake pan! He says it was very easy to work with, but did not cover the back of the turbo/downpipe and he broke 2 dipsticks due to the intense heat. John's carhas a homemade heatshield that appears to work very well. He has also made a hood heat shield from sheet aluminum with 2200 degree heatshield blanket material behind it. Another topic that has been debated is the need to wrap the downpipe with a heat shield material. The Greddy manual recommends it, but some have said that wrapping it can lead to rusting, and eventual failure of the downpipe. Jerry Wellborn has wrapped his and has not had any problems with it. It would help keep some heat out of the engine bay and certainly protect the hoses, lines and brake master cylinder behind the downpipe. I do not have this wrap on my car, but my heat shield extends down about 4" below the top of the turbo behind the downpipe to block some of the heat from damaging these components.
David Hazim has come up with a solution that he says works well for him. He uses Thermotec heat wrap around the exhaust portion of the turbo. Here is a pic of his setup
It might also be a good idea to remove a portion of the rubber weather stripping along the top of the firewall to allow some more air flow inside the engine bay. I just removed the driver side half, but others have removed the whole thing with good results.
15 Programmable ECU
When running high boost on a turbo system (over 10 PSI) I very highly recommend installing a full replacement programmable ECU. There are two major players in the Miata ECU market. Probably the most popular and easiest to install is the Link ECU from Flyin Miata. This ECU replaces the stock Miata ECU and provides complete control of ignition and fuel maps in order to make sure your engine always has the optimal fuel mixture. This ECU also can control larger injectors, meaning you no longer need the fuel pressure regulator, or high pressure pump anymore. The ECU can control boost with an optional boost control solenoid, as well as give knock control with the optional knock sensor. With this ECU you also have the ability to do data logging...recording data from the ECU 12 times per second for complete review after the run. This is essential in tuning the ECU. Also available is the more complex, more expensive, but more powerful TEC-II. The TECII kit runs about $2500 which includes the knock sensor, 550 CC injectors, boost control, crank sensor, coils etc. There is no 90-93 specific kit however, so you must wire it up yourself. Check out http://web.archive.org/web/200501151925 ... mance.com/ for more info.
IV Where to purchase new/used parts for upgrading the kit
Because the Greddy turbo kit mostly appeals to those looking for cheap power, it is common practice to try to source used parts to keep the cost down. There are many places to find these. These include the e-mail me (nramsey@evergo.net) and let me know). Jim Bobowski is a great source for intercooler kits at low price. His page is here.
Some great sources for used OEM parts like 1.8 injectors, Torsen LSDs, etc: Mazda/Toyota Recycling, Mazmart, and Mazda Recycling
