Installing A Turbocharged 280ZX L28 Into An Early Z - The Basics:

Contributed By: Tony Genovese, IZCC#2044,

As of 19 July, 1999


Before you proceed, you have asked yourself, why?
Many reasons: first being the extra horsepower; this conversion is one of the simplest ways to get neck-bending acceleration outside of fitting the car with a V8. Next, is the ease of these installations; practically nothing has to be done to allow the early Z body to accept a ZX turbo motor installation. The engine bay of any L-6 powered Z or ZX will accept all variations of this engine: L20A, L24, L24E, L26, L28E, L28ET. Also, straight-six L-series motors had a very long production run at Nissan; not only were they used in many different models of the Z/ZX over the first 14 or so years of its existence, but also in other Nissan vehicles as well. These motors were placed in cars that were sold in many different markets all over the world, so their production numbers are conceivably in the millions of units. As a result, both the factory and aftermarket support for replacement parts was and is still very extensive. This only helps to simplify the process of transferring a motor from one car to another in the event you may break or lose an important component.

This can be accomplished through any number of means. However, your sucess may depend on which part of the country you live in; this usually determines the affordability and availability of such a thing. Locating a donor 280ZX Turbo shouldn't be too difficult, considering many turbo cars were produced from 1981-1983 model years. The Z car was produced in vast numbers and sold at an affordable price. In its twilight years on the road, this has given the car an incompareable position when it comes to finding one in any condition imaginable.

Depending on your intentions, the kind of car you end up with may or may not fit the bill. However, one thing you will want to ascertain is whether or not the car is an honest-to-god turbo model, and not some backyard creation/amalgamation of multiple Z-cars--in short, the more original, the better.

Also, depending on your auto-mechanical skills, you may want to make sure that the car, or more importantly the engine is in acceptable running condition. This is helpful in determining whether there is a reliable base to start from. The spectre of costly machine work and the replacement of certain expensive engine parts can be substantial hurdles to overcome in a project of this sort. Having a relatively healthy motor ready to drop in and experiment with is a lot more fun than beginning with one in questionable health that's just going to eventually fail. If the motor obtained is of that latter variety, it would be best to proceed with a general tear down and overhaul to establish a little reliability.

So let's just say you know your way around Z cars and engines, and you're already aware of the possible complications; you have commenced with a possible purchase of an engine or a donor vehicle for its drivetrain. You've either located it through the usual sources: the Auto/Parts Trader, the newspaper classifieds, or you're the hardy sort whose gone the distance and extracted one yourself from the local pick and pull junkyard. My own personal experience was to acquire one from a towing yard. I thought it beneficial for the fact that I was able to drive the car before I bought the motor. The car itself was a basket case, and I was lucky that the guy was willing to sell me just the parts I wanted.

Although the turbo unit that I received along with my motor was seized and a complete loss, this will not always be the case. The turbos for these cars in their stock configuration are readily available. The stock unit is a Garrett AIResearch T3. I acquired a replacement turbo unit from a junkyard for around $80.00, which is a very good price. If you have found one in a help-yourself yard, a good way to assess the condition of the turbo would be to check the impeller shaft for any significant side-to-side movement or end-play--anything more than a millimeter would be unacceptable.

It's just about the time to start on the actual metamorphosis, so it must be decided which components are necessary to begin the conversion.

When I found my donor car, I made sure not only to get the motor itself, but all the related engine management items as well. Unless you have planned to use an aftermarket system like a Haltec, SDS, or Electromotive, the easiest way to fire your F.I. turbo motor would be with the stock computer and wiring harness. These things are relatively easy to remove from the turbo ZX, but you must ensure that everything is there and intact. The wiring harness is probably the most complicated thing to separate from the car. It's attached to the battery as its power source via the fuse relay box in the engine compartment. In roughly the same spot, behind a plastic panel is the main Electronic Fuel Injection (EFI) Relay, which is wired into the harness also. At this side of the motor, the harness is connected to the knock sensor on the cylinder block and the cylinder head temperature sensor at the rear of the cylinder head. On the manifold side of the motor, the harness is connected to all the important fuel, air, ignition, and intake manifold vacuum accesories--a good tip is to leave all these things connected so you don't lose track of where they go when final hook-up is attempted, especially when it concerns the injectors!

The Bosch L-Jetronic injection is batch-fired, but it can still be confusing when all six injectors have become disconnected. For the most part, an injector plug's destination can be located by just studying the twists and turns the wiring harness leads take. Finally, follow the harness through the firewall to the location of the Electronic Control Unit (ECU), or "brain." Depending on what model the car is, it could be either a light blue or black slim rectangular box. Only the turbo ECUs have ports for three separate plugs (the normally-aspirated cars have an ECU that accepts one long plug). Later model turbo cars also have in the vicinity of the computer a fuel pump control modulator, which also is connected via the harness. Note: I highly recommend use of the later '82-'83 wiring harness, because it's more self-contained than the '81 counterpart, and I've had better results with it.

One last thing to do is hunt for the fuel pump relay which is buried behind the passenger side dashboard on the right side of the glove compartment. It's a green relay amid a cluster of other relays. The wiring diagram in any Haynes manual will show what color wires are connected to it.

In order to retrofit the harness into an early Z, such as a 240 or 260, a hole of at least an inch and a half diameter must be drilled in the firewall to allow the computer to be mounted in the drivers side of the passenger compartment. I used a little ingenuity to mount it below and to the left of the steering column. If you wish, you can secure the ECU aganist the kick panel in approximately the same location as the 280ZX, and the fuel pump modulator control box can fastened to the sheet metal above that.

The other related ancillaries deserve a mention, because they all function together to produce a well-running turbo motor. The Air Flow Meter (AFM), vacuum control modualtor, Auxillary Air Control (AAC) valve, injectors, coil ignitor, crank angle sensor, fuel pump and fuel damper are the most important of these and for the most part are unique to turbo models. Great care must be taken to make sure that these things are there and working and correct for the application.

One other thing that should be mentioned is the fuel tank. Unless the vehicle receiving the turbo engine is a 280Z, the fuel tank should be changed to one that originally came in one of the fuel-injected cars. This prevents the possibility of fuel starvation from inadequate feed out of a fuel tank that originally was intended for use in a carbureted car. On these fuel tanks, the outflow and return lines are too restrictive, and the baffling inside the tank cannot prevent the high-flow fuel pump from sucking air into the fuel line. This problem will manifest itlself when the car corners and all of a sudden the motor will cut out from lack of fuel pressure at the injectors. This is not a comfortable feeling for the driver, and it's definitely not a healthy thing for any turbo motor to experience especially under high throttle and boost. Remember, only model year 1975-76 280Z fuel tanks can be easily fitted into the fuel tank location in a 240Z or a 260Z. After 1976, the rear compartment of all 280Zs was redesigned, and does not resemble the configuration of the early cars.

Once in the engine bay of an early Z car, the turbocharged 280ZX L-28 looks suspiciously at home. The only item which has to be coaxed somewhat into place is the bulky AFM. It resides at the front drivers side of the engine bay at the head of the thick rubber intake tube. The stock fresh air intake duct must be removed to accommodate the AFM, but this is a minor inconvenience. Now the exposed hole in the radiator support can be used to employ whatever kind of tubing desired to route air via a K&N cone filter or custom air box to the AFM, turbocharger, and finally the intake manifold.

In routing the exhaust from the turbo unit itself, there are two items worth obtaining in order to facillitate this. They are the main down pipe coming off the wastegate housing of the turbocharger, and the following head pipe that affixes to the bottom of the down pipe with a custom slip-fit and a three bolt flange. The head pipe itself is 2.5" in diameter ending in a two-bolt flange approximately three feet behind the motor. These both come as stock pieces on all 280ZX turbos. Although after many years, these exhaust components will typically be fused/rusted together. If this is the case, the most effective way to separate the two is to do it while the motor is still in the donor vehicle. Using the underbody of the car as an adequate support, lever the header pipe out of the downpipe flange with an appropriate prybar. As always, excercise some caution, as it could be a violent separation.

With the pursuit of installing a later model fuel-injected motor into an early Z, the need to perform certain modifications automatically follows. In addition to the minimal ones enabling the motor and the engine wiring to fit, more radical mods can be undertaken. At this point, there is an open ended exhaust pipe emptying its product right under the drivers seat. Selection of an exhaust system is now necessary in order to maintain a comfortable noise level! Choices consist of the size of pipe desired and type of muffler. Exhaust tubing size is limited to two basic kinds: 2.5" and 3" sizes. I'd lean heavily in favor of using aluminized pipe, mainly for aesthetic reasons since it tends to resist corrosion. But in any case, I've found that 2.5" pipe is adequate for a street car, and crush-bent tubing is perfectly suited for street applications, but some people insist that 3" diameter tubing with mandrel bends and a free-flowing muffler are a must. Spending the extra money on mandrel bends is up to you, however, my suggestion is to keep within a reasonable budget and select a very non-restrictive muffler based on the type of exhaust note you prefer. You will find that this plan of attack keeps cost down and produces satisfying results in any street car.

Air intake usually has to be modified from the inception of this project due to the fact that the large stock ZX turbo air box is difficult to place into an early Z. Using an aftermarket K&N oil bath cone filter will merit better results; it will allow less restrictive and cooler air induction, it will filter particles far better than a stock paper element, and it will also provide a race-ready look both underhood and from the front of the car.

If you are seeking a serious increase in performance, then you may want to consider outfitting your turbo engine with an intercooler. This is the first and crucial step that needs to be made in order to run more boost. Intercooler choices are as numerous as any other mod-related upgrade, so do some research. An easy and commonly used alternative is the Mitsubishi Starion intercooler, although the limits of boost it's capable of sustaining are quite low according to some people. Along with increased boost are other important considerations. When more boost is produced by the turbo, the motor is subjected to more internal stresses like heat and pressure, which can sometimes overwhelm the stock components, so be mindful that changing one thing always affects another. Plan on upgrading your computer, turbo, intercooler, injectors, head gasket, and maybe even pistons if you want over 300HP. Some common upgrades using later model stock 300ZX components are out there as well.

A typical example is improving the air flow into the engine by using a Mass Air Sensor from a Z31. The much smaller MAS unit replaces the flap style AFM, but since it shares the same diameter, the intake tubing does not have to be changed. However, in order to use this set up, a modified 300ZX turbo ECU, must replace the 280ZX control unit. These can be obatined from performance retailers such as Jim Wolf Technology in El Cajon, CA.

Turbo units from the later V6 turbo Z cars can be fitted to replace the 280ZX one. The main difference between the two is the lack of a water-cooled bearing section in the earlier 280ZX turbo. There is a definite possiblity turbos from other vehicles and manufacturers can also be used in place of the stock Nissan components. Bigger turbos and different impeller designs can adversely affect the performance of your motor, so be aware that experimentation in these areas can either be very rewarding or very costly, depending on what you know or who does your work.

Tony Genovese
San Diego, CA
July 1999