Fuel level sender specs: 74-ish ohms empty, 0-5 ohms full. This matches the specs for a VW Bug.

Disposing of the relay board:

The stock relay board tends to burn connections, lose it's waterproofing (which was never very good to start with) and generally flake out. Replacing it with some waterproof connectors and a sealed board is a good idea.

The Haynes manual shows three different diagrams for '70-71, '72, and '73. However, I didn't see much significant differences as far as this job is concerned. As far as I can tell, these should work for all D-Jet cars. I've not yet taken the time to look at an L-Jet relay board, and some of these instructions will probably not work for L-Jet.

The wire colors are main/trace. A green wire with a red tracer is green/red.

There is a main trunk of wire running through the center tunnel, through the firewall near the shifter, and up through the tin. There's an engine harness that leads to various places on the engine. There are four connectors of interest on the relay board, the 14 pin (near the firewall), the 12 pin, the 4 pin from the ECU, and the 3 pin voltage regulator (VR) connector. The connections are:

14 pin
1 yellow, main trunk, starter wire from ignition switch
2 blue, main trunk, goes to G light on combo gauge
3 gray/brown, main trunk, switched +12, attached at brake switch
4 gray/brown, below engine harness, reversing lamp
5 green/red, main trunk, oil pressure light
6 green/black, main trunk, oil temp gauge (even if not fitted, may not be on '72 -)
7 black/purple, main trunk, tach signal wire
8 black, main trunk, switched +12 from fuse 8
9 green/white, main trunk, rear blower switch
10 brown, grounding point for main power relay
11 brown/white, main trunk, "optional for sportomatic"
12 red, battery + terminal, to main power relay
13 black/red, to fuel pump (+12, switched by FP relay)
14 red, from battery +, to 25A fuse on board, FP relay and others

12 pin
1 green/red, engine harness, oil pressure switch
2 gray/brown, below engine, reversing switch
3 green/black, below engine, oil temp sender (might only be on '70-'71)
4 gray/brown, below engine, reversing switch
5 black/purple, engine harness, coil - (tach signal)
6 yellow, starter solenoid
7 black/red, coil +, ignition power
8 N/C
9 N/C
10 N/C
11 green, blower motor
12 white, Aux Air Regulator (AAR)

3 pin
red, D+ on alternator to D+ on VR
green, F on alternator to F on VR
brown, D- on alternator to D- on VR

4 pin
I switched power to ECU, pins 16 and 24 on ECU
II powered by starter wire, to pin 18 on ECU (cranking signal)
III fuel pump control (to FP relay) pin19 on ECU
IV powered by starter wire, directs power to cold start valve

Using a 6 pin connector, you can make some obvious connections for the gauge sensors:

black/purple, engine harness to black/purple, main trunk (tach)
green/red, engine harness to green/red, main trunk (oil pressure)
green/black, engine harness to green/black, main trunk (oil temp)
blue, main trunk to D+ on VR (G light)
brown/white to brown/white (sporto)

The brown/white wire is "extra", as no one really has a sporto 914, but it may come in handy someday. The wire terminates behind the combo gauge, on cars that have it at all. It may not appear on later cars.

I'd use a two pin connector for the yellow (starter) wire and the black wire (ignition switch). Direct the engine side of the yellow wire to the starter solenoid using a ring terminal. If you're doing a carb setup, that's all you need. If you're keeping D-Jet, another ring terminal with another yellow wire to a connector that splits the wire to the cold start valve and the ECU. Use a connector that will take 14g wire, and stuff two 18g wires for the valve and ECU on one side.
The engine side of the black wire should go to the new main power relay (which we'll get to).

The VR can simply be connected directly to the alternator, and you can mount this in several places. Borg-Warner makes a nice solid-state VR that will be more reliable than the mechanical Bosch units. Part number R588. Goop the spade connectors in silicone and mount it to the tin someplace.

Now, the "new" relay plate. You can use inexpensive Radio Shack supplied 30A automotive relays. Much easier to get and much cheaper than the round ones on the board now. You can get a 4 position ATO fuse block at many FLAPS, as well as online in a number of places. Mount all of these to a flat plate. I would probably want to mount it either in the rear trunk, or in a waterproof box. There are small, cheap plastic cases called Pelican Boxes sold all over the place. A box roughly 4x5x2" is adequate, and shouldn't cost more than $20. If this is strictly a no rain car, you can just mount the plate to the firewall or even the stock relay board holder.

You'll need at least one relay just to make the car work. I'll detail options later. Each relay has 4-5 terminals on it, and each are numbered: 30, 85, 86, 87, 87a (5 terminal). Ignore the 87a, we'll only use the first four. 30 is the power in, so you need to hook that up to unswitched battery power (red wires from the B+ terminal). 87 goes to whatever is being switched. 85 and 86 go to the switch that controls the relay and ground (doesn't matter which is which). We'll use 85 as the switch and 86 as ground just to keep things consistent.

Run a 14g red wire to the relay plate, and daisy chain it to all of the 30 terminals on all of the relays you intend to use. Run a 14g brown wire from some convenient ground point to all of the 86 terminals.

The first relay is the main power relay, and is there to keep the current through the expensive and hard to replace ignition switch to a mininum. The 85 terminal should connect to the black wire from the main trunk. The 87 terminal needs to go to several places, so I'd put a ring terminal on the end, and put a bolt in the baseplate that you insulate from the base plate using fiber or plastic washers. Hook the ring terminal to the base plate, and all of the "out" wires will also have ring terminal on the end. Adding new switched power wires will be easy for later modifications. Power needs to go to the + side of the coil. For D-Jet applications, you'll also need to go to pins 16 and 24 on the ECU. If you're doing aftermarket PEFI, you'll also want to run power to the injectors from here, as most PEFI ECUs ground the injectors to switch them on (D-Jet reverses this).

The second relay is the fuel pump relay. If you're doing a carb setup, skip this and just run power from the main power relay through an 8 amp fuse in the 4-position fuse block to the fuel pump. If you're running EFI, you'll need this relay, and the 85 terminal needs to go to the ECU (pin 19 on D-Jet). Run the fuse, too, between the 87 terminal and the fuel pump itself.

If you want to keep the blower motor, run another relay, with 85 hooked to the green/white wire from the main trunk. Run a 15A fuse, at least.

On connectors, crimp connectors are generally better than solder connectors. Soldered connections are brittle and tend to break up if subjected to vibration. A good weatherproof connector is the Weatherpak line, which comes in many sizes, 1, 2, 4, and 6 pin being commonly available (try www.rs-autosport.com or www.speedwaymotors.com).

I hope to provide some photos later. I invite comments and bug reports.

What you need when doing a Six conversion:

An engine, of course. The best source here is Bruce Anderson's 911 book, as it covers all of the engines in detail. The real 914-6 used a '69 2.0 911T engine. Most conversions use a 2.7 ('74-'77) or a 3.0 (aka SC, '78-'83), as there are a lot of them, and they provide good power (160-180hp). SC engines are very reliable. 2.7 engines are cheap, as they have a bad rep due to poor design choices in handling emissions. The 3.2 engine is fairly common. The 3.6 is still pretty expensive, and pretty much maxes out the 914 gearbox. The older engines will usually need to be rebuilt, and this is not an inexpensive proposition ($7-12K). Get an engine with a complete induction system, as putting these together afterwards is difficult and expensive. The CIS (aka K-Jet) engines will fit, but only just. Carbs are often swapped in, but they're very expensive (Webers), or they're crap (early Solexes). The 3.2 and later engines all use EFI. The MFI engines (late 2.0 E and S, all 2.2, most 2.4) are very sweet, but MFI pump rebuilds are even more expensive than a set of 40IDA3 carbs.

For anything other than a 2.0, you'll need a flywheel. The 2.0 engines used the same cup-type flywheel with the push type clutch as the 914. The 2.2 to 2.7 engines can also use a 2.0 flywheel, as it will bolt on. The 3.0 and later engines can't use the early flywheel at all (9 bolts hold it on the crank instead of 6), so they need to be made or bought. Kennedy sells flywheels adapted to match the 914 gearbox to any Six.

An engine mount. The real 914-6 used a mount on the firewall with a single bolt holding the engine to this mount. Rich Johnson sells an updated version of this mount with two bolts, which is generally regarded as the best available. There are some bar-type mounts that attach to the 914-4 engine mounts, but these are of varying quality, mostly bad.

An oil tank. The 911 engine is a dry sump engine, meaning it has two oil pumps, one to suck the oil out of the tiny sump and into an external tank, and the other to take oil from that tank and pump in through the engine. The real thing had a tank that fit on the driver's side, forward of the rear wheel, aft of the firewall, between the inner and outer fender. Those indentations in that inner fender are cut out to make room for the oil filter, and the oil filler. Some people use a generic oil tank and mount it in the front trunk, sometimes also plumbing in a front-mounted oil cooler, too. Real 914-6 tanks, which were pressed steel, are hard to find. There are some knockoffs cast out of aluminum which frequently leak.

Plumbing. Real 914-6 lines are pretty much unobtainium, but they can be made up using custom fittings (available), AN fittings, and -12 to -10 hose. The exact fittings vary from engine to engine, but in most, there's a fitting under the engine mounted oil cooler that usually causes the most trouble, as you can't use the stock 911 fitting there, since the trailing arm is in the way. Cutting and fabricating is required here.

An oil cooler. This is optional for the milder engines (all T & E variations, SC is iffy). The 3.2 and later engines REQUIRE an external oil cooler, as they don't have one on board. The S versions of all engines will need an external cooler.

Exhaust. A set of 914-6 headers aren't too bad on price, but you get no heat. Stainless aftermarket HEs are a pretty penny. Used 914-6 HEs show up now and again, but are usually in pretty tatty condition, and still expensive.

Throttle linkage. The 911 uses rods for the throttle from the pedal all the way to the engine. Because the 914 installation flips the engine around, and uses a cable, some linkage is required to adapt the forward pull of the cable to a backwards pull to work with the 911 induction systems and linkage. A common way to do this is with a pivoting linkage back on the gearbox that uses a 911 throttle rod from the carb/efi linkage to back near the speedo drive on the gearbox, then run a cable from the pedal back to this pivoting linkage.

Engine tin. The 911 tin on the engine itself works fine, but the tin surrounding the engine one work at all in the 914 engine bay. Replica tin in fiberglass is available and quite inexpensive.

Depending on which mount you use, the shift linkage may need to be modified. The side-shifter long rod usually has to be cut and welded to straighten it, to keep it from hitting things (engine mount for cross-bars, HEs, the engine itself).

Note I have deliberately not included actual prices for things, as this information ages rapidly. A entire book could be written covering this subject in detail. I'm also only listing the things necessary to get an engine running in a car. Most conversions also upgrade the brakes, add flares for wider wheels, upgrade CV joints, etc.

With non-servo brakes, like on the 914, braking force at the brake rotor depends on:

1. the force applied to the brake pedal
2. the length of the brake pedal (distance between where your foot hits it and where the master cylinder pushrod is pushed)
3. the ratio of the master cylinder piston area to the total area of the caliper pistons
4. the pad material
5. the rotor material
6. the diameter of the brake rotor
7. the amount of heat in the brakes already

Note what's missing here: pad area. The size of the brake pads has no effect on braking force. Friction does not depend on area. Smaller brake pads will not provide any less braking than larger brake pads. Smaller pads will wear faster than larger pads, and smaller pads will be more vulnerable to brake fade from overheating, but in the absence of fade, larger pads gain you nothing.

Pedal length and rotor diameter are both leverage effects. Push a 10ft pedal and you'll have to push much more gently for the same force on the master cylinder pushrod than with a 1ft pedal. You'll have to push the 10ft pedal a lot farther to gain the same amount of movement of the MC pushrod, however. If the caliper grips a 10ft diameter rotor, it has much more leverage in slowing the hub than a caliper gripping a 1ft diameter rotor, so the 10ft caliper doesn't have to grip as hard. Pedal length and rotor diameter are obviously limited by things like cabin size and wheel size.

The MC/caliper piston ratio is another leverage phenomenon. Force on the MC piston is multipled by the ratio between it's area and the area of the caliper piston(s). If the caliper pistons are 10x the size of the MC piston, you get 10x the force applied at the MC applied to the caliper pistons(s). If the pistons are 20x the size, you get 20x the force. However, the MC piston has to move farther in the 20x ratio to move the caliper pistons the same distance. So, the tradeoff here is pedal travel v. pedal force for a given caliper force. A smaller MC will give more braking with less effort than a larger MC, but you'll have to push the pedal farther to get that braking. This is why the common 19mm MC "upgrade" isn't much of an upgrade at all. You're requiring MORE force at the pedal to get the same braking as with the stock 17mm MC. However, the 19mm MC gives a firmer pedal that requires less travel, and some people prefer this.

The pad and rotor materials affect the coefficient of friction, which determines how the caliper force is actually turned into frictional force to slow the rotor. Cast iron has a relatively high coefficient of friction, which is why it's used in preference to, say, stainless steel.

Heat is the wild-card. Hot brakes may work better or worse than cold brakes, depending on the pad and rotor materials. Beyond a certain level of heat, the coefficient of friction will always go down unless exotic materials (carbon-matrix pads and rotors) are used, so as you get the brakes really hot, braking will worsen, and you'll be experiencing brake fade. Fade can get bad enough that you press the pedal and nothing happens at all. How much heat is generated depends largly on the weight of the car and the speed you're trying to get rid of. A heavier car will generate more heat (and this rises linearly, so 2x the weight gives 2x the heat load). A faster car trying to slow to a slower speed will generate more heat (and this rises exponentially, so 2x the speed gives 4x the heat load). Whether or not the braking system can get rid of this heat before brake fade becomes a problem depends on many factors, but rotor area, pad area, and airflow across them all figure prominently. Vented rotors give more than 2x the rotor area for a given rotor diameter, so they shed heat very efficiently.

Bleeding brakes:

Everyone natters on about pressure bleeders, using a friend to wear their leg out, yada yada...Here's a method you can do by yourself with nothing more than a length of clear plastic tubing and the appropriate wrenches to open the bleeders.

First, you have to understand that brake fluid is heavier than air, and relatively viscous. Air in the system will want to rise to the highest spot, and it will move along with moving fluid.

Open the reservior cap. Top up the fluid.

Attach the tubing to the bleeder, and drape it so it rises from the bleeder as straight up as you can get it. You want the tube to go up straight so the open end is higher than the reservior.

Open the bleeder.

Wait.

You'll see fluid rising in the tubing all by itself. Gravity is pushing fluid down out of the reservior, and up through the tubing, and will do so until the fluid level in the tube matches the fluid level in the reservior. Fluid seeks its own level.

If there's air in the system, you'll see it bubble up through the fluid. Air rises in brake fluid, so it will go up all by itself. The fluid is moving, which will push the bubbles along in whichever direction the fluid is moving, so eventually all of the bubbles will be transported to the bleeder and out.

Close the bleeder. Top up the fluid in the reservior. Go to the next caliper and repeat.

Now, if you've really drained the system (replaced one or more calipers, or the MC, or lines), you may find that fluid doesn't start to come out on its own for quite some time, so the "Wait." step above may be for a good long while, like an hour. Air is compressing ahead of the fluid in the restrictive passages, and it takes awhile to "blow" the air through the system from the relatively weak push of brake fluid weight. Pumping the pedal with the bleeder open will help a bit here, as the MC will behave like a pump to move the fluid along. Raising the nose of the car can help get fluid to "fall" to the rear calipers a bit faster.

If you have enough tubing and can remove more than one wheel at a time (up on jackstands or the like), there's no reason you can't bleed more than one caliper at a time.

On the prop valve, you might need to crack the upper-most line until you see fluid, then close it again. I've heard people say you need to "mash" the pedal to "open the prop valve", which is wrong. The prop valve is OPEN if there is no pressure in the system (and with significant air, there will be nearly zero pressure). The prop valve CLOSES when there is significant pressure, so mashing on the pedal actually does the reverse of what's desired.

Don't worry about closing and opening the bleeders only with the pedal down. If you have a column of fluid in the tube (as you should just after opening it), then the fluid in the tube will be sucked back in when you lift off the pedal. This is why I've never understood the whole concept of "Speedbleeders", which have a check valve to prevent backflow into the caliper. If there's fluid in the line, where's the air supposed to come from? On some cars with bleeders that fit very loosely, you may find wrapping one turn of Teflon tape around the threads helps bleeding a bit. Air can get past the threads while you're pumping even if the tube is full of fluid. This air will just bloop right out of the bleeder again, but may fool you into thinking the air is coming out of the system. It also helps to not open the bleeder any more than is necessary.

When you get close, you may hear a squeaking noise as you press the brake pedal. This is the sound of a very small amount of air compressing, meaning you just have tiny bubbles left in the system. These very small bubbles often get stuck in restrictive passages, so tapping on joints, loops in hard lines, the MC, the prop valve, and calipers, can help loosen these. Vigorously pumping the pedal can also help.

Adding HID lights:

HID lights are, essentially, fluorescent lights. This makes them fairly efficient in terms of light for power used, but they require high frequency, high-voltage AC current to work, and your car's electrical system is a low-voltage DC system. So, this means an additional transformer is required, which takes up space and robs you of some of the efficiency by disappating some of the energy as heat rather than light. A typical HID light uses 35W of power to produce about 4x the light a normal 55W headlight bulb produces. The current draw from the transformer, however, raises this to about 80W for both front bulbs, which is still better than 110W for two non-HID bulbs.

However, when an HID bulb is turned on, a high current is required to get them started, about 200W per bulb for the first few seconds of operation. This is nearly 4x the current required to run regular bulbs, so the stock wiring harness is NOT adequate to power these lights. You need to run 30amp relays (one per bulb) and 20amp fuses (one per bulb) and heavy gauge wire (14g is just adequate, 12g would be better) from the relay to the battery and the relay to the bulbs to power them. Use the normal headlight wires to switch the relays.

If you do not do this, you're certainly going to blow fuses, and you may burn up the stock headlight switch, which is very expensive and hard to find.

In any no-start problem, start with the spark. Pull out a spark plug (any spark plug, doesn't have to be one that's in the engine now), hook it up to a plug wire, place the electrode end of the plug against the engine case (someplace where it's grounded), and have someone else turn the engine over. Don't be touching the plug while they do this. You should see a spark. If you see a spark, then chances are it's a fuel problem, not an ignition problem.

If you don't see a spark, then repeat that test, but use the center wire in the distributor, the one that goes from the coil to the distributor cap. Disconnect it from the cap and put a spark plug there. See if you get a spark now. If you do, then the rotor or cap is bad, so replace them.

If you still don't get a spark, then you go to the next thing. Is there a wire from the points to the - post of the coil? Is that wire any good? Sometimes, it can look good, but the connector isn't on properly. Test it electrically with a meter. You should get continuity between the connector and one side of the points. Verify with a meter that the points are actually opening and closing (check for continuity across the points, and a lack of continuity when the points are "on the cam").

If all that checks out, switch on the ignition and ensure that the wire to the + post of the coil has +12v on it (test between the post and ground). If you don't have +12, now you need to start digging into wiring diagrams. I'd start at the ignition switch and work my way towards the coil.

If it does have +12, then check and double check the ignition timing. Timing that's way off (esp if it's 180d out, as it would be if the plug wires were on incorrectly) will prevent it from starting even with a spark. You'll need to do a static timing test, so set the engine to TDC on cylinder one, and make sure the rotor is pointing at the correct plug wire for cylinder 1. The rest of the cylinders should be 4, 3, 2 in clockwise order around the cap. Ignition timing doesn't have to be exactly right to start and run. It can be advanced by as much as 25d BTDC without really affecting starting. It can be retarded to about 5d ATDC before you have trouble starting the engine. So, you have a big window the spark for the car to start.

If the timing checks out but you still have no spark, try replacing the condensor (it's cheap). If that doesn't fix it, try another coil (not as cheap as the condensor, but still not expensive).

If you get to this point and you still have no spark, you skipped something, so start at the top and try again.

Once you determine you have a spark and the spark is happening at the right time (approximately), and the car still won't start, then you have a fuel problem.

Q: why can't the MPS be repaired? Can it be re-engineered?

The D-Jet MPS is, at this age, now prone to failure. The usual failure is the diaphram breaks, and the device no longer senses pressure changes. This would be no problem, if there were a source of replacement diaphrams. However, the original units were made of some exotic material like beryllium-copper alloy, which is not readily available to produce replacements. Attempts to duplicate the part in other materials have met with generally negative results. The only reliable source for the parts are other used MPSes. The MPSes are not all the same, but the diaphrams are, and interchange.

There are modern pressure sensors available that are solid-state, very reliable, readily available, and not expensive ($20-50). However, these generate a variable resistance based on absolute pressure. The D-Jet MPS does NOT use variable resistance, but instead uses the variable inductance of a coil with a movable armature to phase shift a square wave generated by the trigger points. The MPS used with the Type IV has TWO coils, and feeds back the output of the first coil into the second along with a voltage provided by the air temp sensor. This makes the MPS a genuine air-density sensor (pressure and temp determine density), not just a pressure sensor.

Duplicating the effect of the MPS using a MAP sensor, a temp sensor, and some electronics would be possible. However, the complexity of these electronics would approach that of a full fuel-only ECU. You'd need some way of reading the variable resistance MAP and air temp sensors and the trigger point's square wave, and output a square wave calculated from the sum of these inputs. This would really require a microcontroller (I'm sure it could be done using all analog parts, but probably only with a large parts count), which would have, using the simplest approach, a 3D map of rpm (read from the square wave in) and air pressure, with a 2D correction map for air temp. This is, essentially, all most fuel-only ECUs do. No cold-start or warm-up enrichment system would be required (provided separately on D-Jet), nor would you need the injector driver circuitry. Still, the jump from this to a full replacement ECU that uses a normal tach input (no trigger points, so any distributor could be used) and an off-the-shelf MAP sensor is fairly small, and you could also remove the aging (and sometimes troublesome) cold start system from the D-Jet as well as the MPS with a full replacement ECU.

Terms defined:

D-Jet = short for Druck-Jetronic (druck is pressure in German). The first mass-production electronic fuel injection system, devised by Bosch, and used from the late 60s on VW, Mercedes, Volvo, and Porsche cars, until the mid-70s. D-Jet is a speed-density system (see below).

L-Jet = short for Luft-Jetronic (luft is German for air). The second mass-production electronic fuel injection system, also from Bosch. L-Jet is a mass flow system (see below). The usual L-Jet sensor is a flapper type valve that measures airflow mechanically. Later systems used a "hot-wire" sensor that measured air using an electrically heated wire in the airstream, using the cooling effect of the air.

MPS = manifold pressure sensor, key part of the D-Jet system. This is an electro-mechanical system with a metal diagphram and two coils to provide inductive signals to the ECU. See speed/density and MAP.

speed/density EFI = a method of fuel injection that uses engine speed as one signal, and manifold pressure and air intake temperature as paired signals to derive air density and engine load. see MAP.

mass flow EFI = a method of fuel injection that uses the mass of the air flowing into the engine as the primary signal. Theoretically, this is all that needs to be known to derive mixture (and thus calculate fuel). In practice, you also need to compensate for cold-running conditions.

MAP = manifold absolute pressure. Can be expressed in several units of pressure, but is most commonly quoted in kilo pascals (kPa). 0kPa is absolute vacuum, 100kPa is (more or less) normal atmospheric pressure at sea-level. MAP is measured in the intake manifold between the throttle(s) and the intake valve(s). Typically, you'll see MAP values between 20kPa (deceleration) and 98kPa (WOT on a good engine). Idle is usually around 35-40kPa.

Narrow-band O2 sensors v. wide-band O2 sensors:

Engines run on air/fuel mixtures ranging from 10:1 (very rich, lots of fuel) to 17:1 (very lean, little fuel). Best power is achieved with the mixture around 12-13:1. Best economy (gas mileage) is achieved with the mixture around 16-17:1. Best emissions with a modern catalytic convertor are achieved with 14.7:1, which also happens to be the "chemically correct" mixture for getting 100% combustion when burning gasoline in air. This ratio is called "stoichochoimetric", which many people shorten to "stoich".

Narrow-band sensors were invented to detect in a very unambiguous way when the air/fuel mixture was EXACTLY 14.7:1, since emissions were the primary concern. They act as a three-way switch: rich, stoich, lean. It's the nature of these "switches" that you can really read them as: way rich, a bit rich, a tiny bit rich, stoich, a smidge lean, somewhat lean, way lean. However, you can't reliably attach a number like 14:1 to "a smidge rich", nor can you rely on all sensors behaving properly beyond the three way rich/right/lean scale. So, the 10-20 LED meters out there aren't really telling you the truth. The main reason for this is the sensors weren't designed to be accurate beyond 14.7:1, and they're very temperature sensitive. Exhaust gas temps vary pretty wildly as load, mixture, and ignition timing vary, and these sensors have no way to compensate for the temperature fluctuations. The sensors work by generating a voltage between 0.1 and 0.9v, where 0.5v is just right. I think > 0.5v is rich, but I really don't remember. Any voltmeter can be used to read these sensors.

Wide-band sensors use a different technology, and are accurate from at least 10:1 to 20:1, down to about 0.1 point. They were originally invented for the cars that deliberately run quite lean for excellent economy. However, where the narrow band sensors are very simple devices that require very little effort to read, the wide-band sensors require much more complicated electronics to make them work. 6-7 years ago, wide-band setups cost $800-1000, and the sensors alone were over $400. Today, the sensors are down around $25 each, and the control electronics are as cheap as $150 retail. Now, you can have a meter with 10-20 LEDs on it that really mean something. You can reliably tune an engine to run exactly at 13:1 or 15:1 or 18:1.

Places to get wide-band units are Tech Edge (Australia), Innovate Motorsports (California), AEM (US), and SDSEFI (Canada).

Tuning a Type 4 using a narrowband sensor is asking for serious trouble. Cylinder head temps peak a bit lean of stoich, and if a Type 4 is tuned to run under load at stoich, CHT will soar, and you'll very likely destroy your engine. Since you can't accurately tune a narrowband sensor to run a bit rich (there's no perceptible difference, as far as the sensor is concerned, between rich and really rich), this setup is not all that useful for setting the mixture on a 914. Wideband units are now cheap enough that there's little reason not to get one in preference to a narrowband setup.