Text and Pictures by Kelvin Dietz

For most 510 owners, the thought of an electronic fuel-injected car is completely abhorrent. "I'm not going to have a bunch of electric stuff on my car that's just waiting to fail and leave me stranded." Some of us are even afraid of electronic distributors, preferring to put up with the idiosyncrasies of condensers just for joys of fiddling with points. I felt the same way, but the challenge of one more unusual mod to my car was too much. That, and the urging of a couple Z-car driving friends who swore by their EFI 280Zs.

Well, they were right. This is a very worthwhile mod. I've been running a peanut-chamber L18 head with an L20B cam and an L20B bottom end. About 9.2:1 compression. Carburetion, until recently, was 44mm Z SUs. Good top end – the engine would pull to 7000 rpm. I changed to 38mm carbs and found bottom-end torque to be greatly improved but completely out of breath by 6000 rpm. With the EFI, the low-end power is better than ever, and it pulls well at the top end, too. Wonderfully smooth power from 1000 to 6500 rpm. It’ll pull to seven grand, but there’s no need to.

The car starts easily when cold and there's no choke to adjust as it warms. Absolutely no flat spot in the powerband. And when you turn it off it dies right now. No run-on. Another nice change for those of us who are skilled at the "clutch kill".

The highway mileage didn't go up much, still about 27.5mpg at 75mph with a 5 speed, but the improvement in city mileage is amazing. I have a 2.5 mile commute which was getting me between 16 and 17mpg. The car barely warms up. And most of my driving is in town. The mileage is now between 19 and 20mpg. Usually on the high side.

More power, better driveability and better fuel mileage. You have to like a win-win-win situation.

For those of you who aren't aware of it, Nissan sold fuel-injected, L-engined cars in Japan. The same system the 280Z was running over here. When these four bangers made it to the states as used motors, part or all of the EFI systems would occasionally come with them. I never bothered to collect any of this, but a friend did grab a manifold, and when he found out about my interest, he donated it to science. This manifold will be the only part of the following mod that might be hard to come by. If you can't come up with one, another option might be to cut down and reweld a 280Z manifold.

I’d highly recommend you get the Nissan service manual that covers the car from which you get the EFI parts. At least make copies of the Fuel Injection section and the wiring harness. This will not only provide you with an overview of how the system works, but will also prove invaluable for wiring and troubleshooting.

The donor cars for this project were a 1980 200SX (no O2 sensor) and a 1979 280ZX, although 280Z stuff might work as well. I didn't build a single bracket for this conversion, but I did modify a couple.

From the 200SX, grab the EFI wiring harness. It's plugged into the car's harness in a few places. If in doubt, cut off part of the car's harness. Let the next guy worry about the missing bits. There's a 2.2K resistor near the coil that should have blue wires running into it. Make sure you take it. If the car still has the electronic distributor, grab that, too. (1980, 4 plug head only) You don't need it for this mod, but it's a good thing to have. There are a bunch of relays in a plastic box on the right inner fender. Unscrew the whole assembly and throw it on the "good" pile. You don't need them all, but you'll sort that out later. You'll also need the black box (computer) bolted to the driver's-side kick panel.

Grab the fuel rail with injectors, pressure regulator, and any length of fuel hose you can easily reach. Take the fuel filter and mount. You'll want to replace the filter, but you can use the old one for testing. You will need the mount.

Get the Air Flow Meter. It's buried in that pile of plastic and aluminum behind the left headlights. You don't need any of the aircleaner and airpipe that run between the AFM and the throttle body. You also don't need the throttle body, which is bolted to the front of the manifold, or any other part of the manifold. I would suggest you take any brass or steel fittings that can be easily unscrewed. I don't remember exactly what pieces I used, but suffice it to say that you should grab any "bits" you can lay your wrench on.

You’ll also need to crawl under the back of the car and get the fuel pump. Cut the fuel lines and remove four fasteners to pull the whole assembly.

From the 280ZX, you need part of the Air Flow Meter. The inlet side unscrews and will be screwed onto the 200SX AFM in place of the aircleaner housing. Also take the flat plate that bolts the AFM to the fender bracket,and the fender bracket. That is a hammer and chisel affair, but it works and looks factory original once it's modified to fit the 510 inner fender. It beats trying to design your own.

Grab the throttle body and any linkage, including the pieces mounted to the firewall. Also take the large rubber pipe that goes between the throttle body and the AFM. You'll probably want to replace this with new because the old ones are pretty hard by now, but for testing purposes the old stuff works fine. Also get any PCV hoses that are handy.

Get the Air Regulator assembly from the top of the manifold. There will be one with the 200SX as well, but you can never have too many spares.

You'll also need the thermostat housing and water temp sensor. There will be four receptacles in the 280ZX thermostat housing, of which you'll need two. Also take the ZX injector ballast resistors and bracket. Depending on where you mount the resistors, the ZX bracket might work better than the SX bracket.

I chose the 1980 200SX because it was available. The '81, '82, etc. would work, but they do have an O2 sensor. Not a problem, except you have to plumb it into the exhaust. I figure there was a whole generation of 280Zs that worked just fine without it, so what the heck. The airfilter is a K&N p/n RU-3120. A perfect fit for about $30.

On the head, I had to drill and tap two 10mm holes between the stock upper mounting holes for the new EFI manifold to bolt to the head. The injectors are pretty much in the location of the stock holes. That and a notch in each port for the injector nose was all that needed to be done on the head. Unfortunately, unless you're really good with a hand drill (and nobody is that good) this will involve pulling the head and, at the very least, using a drill press to drill the holes. I let my machinist do the work. You only get one chance.

While the head is off, it's a good time to make a template for the gasket and for drilling the above-mentioned mounting holes. I transferred the pattern of the head (stud and bolt holes, intake/exhaust ports, etc.) to a thin piece of cardboard. Then I punched out the mounting holes, matched the cardboard up with the manifold, and transferred the pattern from the manifold (intake runners, injector notches, mounting holes) to the cardboard. Be very precise in this, because you really want those 10mm holes to be in the right place. I modified a Felpro L20B manifold gasket. It might also be possible to shorten a 280Z gasket for this.

I used the 200SX injectors from the 1980 LZ20. I did have the L18 injectors that came with the manifold, but the larger ones proved to be the right size for my L20B bottom end.

The L18 fuel rail is an ugly bundle of worms, so I built a custom fuel rail/fuel plenum. I procured a big aluminum tube (approximately 7/8" ID, 1/8" wall) at the local scrapyard and welded caps on the ends. I tapped this for 1/8" pipe and filled the resulting holes with brass fittings (with JB Weld as a sealant) leading to the fuel inlet, outlet and injectors. I used PushLoc hose on all the injector fittings. A very tight fit with no clamps needed. Be sure to use PushLoc fittings on the fuel rail. I used standard fuel injection hose for the rest. (DO NOT USE REGULAR FUEL LINE FOR ANY OF THIS PROJECT!) I needed to use clamps (fuel injection clamps pirated from the SX and ZX) for this, but installation is much easier. If you make a custom fuel rail, make sure it's mounted solidly. Don't rely on the injector hoses to hold it up. The vibration will eventually cause the injectors to fail.

You'll have to decide for yourself how to plumb the fuel inlet and outlet. I bent and mounted a custom steel fuel line to run from right to left under the hood latch. Extra work, but it looks clean. You will need a fuel return line. If the car is old enough (‘68-71) it will be there. If not, you’ll have to add one.

I mounted the pressure regulator (which is usually located in the "bundle of worms") on the right inner fender. You'll also need a vacuum source to the pressure regulator. Do not mount the pressure regulator on the firewall. It makes a rather unpleasant buzz that is transmitted right into the passenger compartment.

I mounted the 200SX fuel pump and attendant hardware under the car behind the rear-seat footwell. It’s almost like it was made to go there and it hardly makes a sound when running.

There are a lot of aluminum bosses that can be carved off the intake manifold. The EGR valve at the back comes to mind. When you remove this, you'll need to plug four holes in the bottom of the manifold to avoid large vacuum leaks. After removing the EGR valve, you can drill and tap a hole in the back of the manifold for a PCV valve. With the L20B lower PCV pipe, use the stock L16 lower PCV hose to complete the connection. The upper PCV hose is a shortened 280ZX hose that goes from the valve cover to the throttle body. To turn the valve cover fitting, use a large adjustable wrench and unscrew the fitting. Clean the fitting and epoxy it into the proper position. Do not try to unscrew it by sticking a screwdriver into the fitting. You’ll break it off for sure. You'll also want to build a brace from the motor mount to the intake manifold. I don't know if it would ever break, but a little flattened conduit is cheap insurance.

This system is very sensitive to vacuum leaks, so make sure all your connections are tight. This is also a good time to point out that a big cam won’t work with this modification. The air pulses from a large duration cam will get the Air Flow Meter really confused. The L20B cam works well. A little more lift and duration might work but I don’t know for sure. So far, so good. Now for the wiring.

You'll need to cut a hole in the firewall to feed the EFI harness through. I'd highly recommend a 2 1/4" hole saw. The EFI harness grommet fit this nearly perfectly.

I've provided a modified diagram of the wiring I did. You'll need two source wires from the 510 harness -- a 12V constant from the battery that runs the EFI and Fuel Pump relays, and a tap off the black/yellow starter solenoid wire that tells the brain box to enrich the mixture on startup. Keep in mind that the 200SX has an oil pressure and an alternator safety system that shuts the EFI off in the event of an accident. My design, at this time, has neither. I plan on figuring out how to wire the safety relays; I suggest you do the same.

Most of the wires in the EFI harness won't be the right length. Nissan EFI harnesses are separate from the donor car's harness, thankfully, but mounting the brain box on the 510 passenger's-side kick panel (instead of the driver's) means that all of the injector wires are too long and all of the AFM wires are too short. This still seemed like less work than mounting the box on the driver's side.

Since you'll be modifying the harness, you'd better know how to solder before taking on this project. And unless you want to take the harness apart at some future date, it better be mil-spec. I've seen some pretty scary stuff called "soldering". If you don't feel confident in you skills, spend the money on quality solderless crimp connectors. Molex makes a heat seal version that is about $12/pkg of 10 that work great. Don't try this with cheap butt connectors.

You could use inline fuses to wire this up, but I used an auxiliary fuse block ('68 Dime) mounted to the bottom of the glove box. Various fuses and fusible links from there.

I spent a few days on the bench figuring out how to make this run. I mounted everything on a piece of plywood and ran the whole system with a drill motor turning a distributor. The injectors had been sitting long enough to clog slightly, but by spraying mineral spirits (much less flammable than gasoline) and Techroline through the injectors, they cleaned right up. Once I had the basic wiring and plumbing figured out, it was about 16 days (Three long weekends and about 3-4 hours a night on the weekdays) from the time I pulled the head to the time I turned the key. Not to mention the tweaking done for a couple weeks afterwards. I could obviously do it faster now, but where to route wires and get it right the first time takes a ridiculous amount of time.

All in all, the installation looks pretty factory original, except for the fuel rail, which looks better. And it works great. I've had to play with the throttle linkage a bit (shortened 280ZX) and it's finally perfect after revising link lengths and moving pivot balls slightly.

Keep in mind this article is only a guide. It's a lot more than I had when I started carving and soldering, but there's still plenty of detail missing. And a lot of care to be taken. You'll be working with 30+ psi of fuel pressure and a few custom parts and fittings, so a good deal of common sense is in order. But with this text, the appropriate shop manual, and a ton of patience, there's no reason this induction system can't be duplicated. And the beauty of doing all this yourself is that you also learn how it works for future tuning and troubleshooting.

Besides, isn't it time to move your induction system into the 80s?

Copyright 1997 The Dime, Quarterly