JP's hugantic CIS-E write up by Longitudinal

10 minute read

JP's hugantic CIS-E write up

Compliments of Longitudinal @ www.vwvortex.com

Here it is, folks. CIS-E write-up extraordinaire!

Cleaning:

Keep stuff clean. I like to remove the metering head (which is actually called the fuel distributor) from the air plate assembly periodically. This allows complete scrubbing of the air plate assembly with household cleaners. 

Usually, at least for us non-west-coasters, the external part of the air plate housing is oxidized. I skim off the oxide with an open razer blade, just like shaving. Then I use a 3M Scotch Brite pad and household (Simple Green, Greased Lightning, etc.) cleaner to clean all external surfaces. 

DO NOT scour the air plate or bowl. These come clean easily with a little penetrating oil and a rag. I wipe down the external surfaces of the metering head with penetrating oil and a rag. 

I lubricate all pivot and friction points on the air plate arm with ATF--just a drop everywhere one part moves against another. I also clean where the o-ring seals between the air plate housing and the metering head, then put a little lithium grease on that o-ring. That o-ring hardly ever needs replaced.

DO NOT dismantle the metering head. Just don't do it. If you want to see what they look like on the inside, dismantle a junk or spare unit.

If I am storing a fuel distributor for a long time, I usually put a drop of ATF inside each hole where a fuel line connects.

Maintenance and adjustments:

Mixture rarely needs to be adjusted. If your idle mixture seems off, you should not make adjustments to the fuel system before checking thoroughly for intake vacuum leaks or bad sensors. Also, please note that idle mixture screw adjustment is very touchy. A little goes a long way. Inexperienced users should turn the screw only perhaps a 1/16 turn at a time, followed by a hardy blip of the throttle and waiting for current to stabilize and begin to search again.

Access to the idle mixture adjustment screw is blocked by a factory-installed plug. At this point, many of these factory plugs have been removed, some very crudely by a drill and brute force. If you have a great yawning chasm where there should be a small round hole, don't worry. The air admitted through that hole is unfiltered, but not unmetered. If the plug is still there, it must be removed in order to make any idle adjustments. You can drill it or extract it any way you please, but it must not be punched through. This plug is tapered, so it must come out the top.

To monitor changes in AFR, you will need to construct or purchase a test harness that connects between the DPR and its connector. I have used the heater connector from an O2 sensor and a pulsed fuel injector connector to make the test harness. Connect the two connectors so that the ground side is uninterrupted and the power side is broken. The two open ends of the test connector are to be connected to an ammeter set to a 20ma scale. 

Clockwise (henceforth "CW") is richer and Counterclockwise (henceforth "CCW") is leaner. Note also that turning the idle mixture screw CW causes a DROP in current and CCW an increase. Smaller numbers mean that the ECU is able to send a smaller current to the DPR in order to maintain a proper mixture at the O2 sensor. Higher current means the ECU is sending more current in order to maintain the mixture it wants, which indicates a leaner adjustment.

Idle DPR current will "search" or "hunt" on a warm engine and a working lambda circuit. Adjust the mixture screw to find a current that searches between 6 and 10 ma. Modified engines tend to prefer a richer idle mixture. I normally set modified and turbo engines to center on around 5 ma, never exceeding 6ma.

When adjusting idle current, remember: a high current means mixture is too LEAN, so the screw needs to go CW. A low current means mixture is too rich, so the screw needs to go CCW.

Power Tuning:

Power tuning CIS-E is fairly straight forward. I will cover the basic stuff that gets the results 99% of users want to see. Any power tune must start with ensuring that all ignition parts are in good repair, that basic ignition timing and idle mixture (DPR amperage) are set correctly, that injectors have a good spray pattern, that no intake leaks exist and that all sensors function as they should. Not paying attention to the details and trying to tune the car with anything else out of spec or leaking will not result in a good tune. Also, power tuning the CIS will likely result in a small loss in fuel economy and, in extreme cases, may result in difficulties passing e-checks. The effects of a power tune are proportional to state of engine repair and modification. On a stock engine, the gain will be small. On a modified and/or turbocharged engine, gains will be dramatic. A mixture meter is extremely helpful for dialing in full throttle mixture. They're pretty cheap, too. Narrow band will do just fine for the kind of power you can make with CIS-E.

For a Fox, the first step in a power tune is to wire up a full throttle circuit. This can be a simple procedure. It can be as simple as extracting ECU connecting pins from an old harness and inserting the pins into your car's ECU harness on pins 1 and 5. Pins 1 and 5 lead to the WOT switch. The WOT switch engages the full throttle open loop circuit and is definitely necessary for a power tune. Otherwise, the ECU never leaves closed loop, which means it will always try to pull the mixture back to stoich, which is not what you want for power. After this circuit is in place, you will require a KE-Jetronic ECU from a car with a full throttle circuit. Such cars include Audi 4KQ, QSW, KE-Jetronic A2 Golf and Jetta (including 16V GLI and GTI models) et al. I have not yet tried using a KE-Motronic ECU from a 16V Passat or Audi 80. The VAG PN will be 811906264A, B, C, or D. Any one will work. Connecting the full throttle switch should be self-explanatory, so I will skip that part. 

On boosted cars, I use a pressure switch instead of the WOT switch. Pressure switches are available from digikey, among others. These are nice becauce they are adjustable and permit the user to adjust the boost pressure at which open loop enrichment is desired.

Power tuning for 99% of the population will be accomplished by adjusting the differential pressure regulator. After checking that everything including idle mixture is good and correct, shut off the engine, disconnect the DPR connector, wrap a rag around the DPR and unscrew the DPR from the metering head. Fuel will spray. The rag is there to prevent fuel from spraying into the eyes, onto the skin, or onto a hot exhaust manifold. Keep track of the two green o-rings. They usually stay in the metering head, which is just fine.

Take the DPR from the car and place it in the palm of your hand in a folded-over shop rag. The rag is there to protect your skin in the event of flathead screwdriver slippage. Unscrew the brass flathead screw from the back of the DPR. The threads on this screw are amazingly fine. It is a marvel to me that such a screw could even be made. Remove the screw and KEEP TRACK OF THE COPPER WASHER. If you lose this washer, you will be looking for another DPR. 

Behind this screw is a small allen head (VERY rarely this screw is actually a very small flathead) setscrew. This screw is what you adjust to power tune CIS-E. Just as with the idle mixture screw, small adjustments are significant, and just as with the idle screw, CW enriches. A good initial adjustment is 1/4 turn CW. Turn the screw, then re-tighten the flathead screw and reassemble the DPR to the metering head and reconnect the DPR along with the test harness. Don't go nuts tightening the screws that hold the DPR onto the metering head. They don't require that much torque and they may well be coming right back off after a brief test drive.

Fire up the engine. The idle mixture that you just set a few minutes ago will now be way rich. As always, wait for the O2 sensor to heat up before making any adjustments. Once the O2 sensor is warmed up, the idle current will drop substantially, possibly to zero. Make small CCW tweaks on the idle mixture screw until current is back to spec. Continue running engine until cooling fan has cycled once. Once engine is fully warm and idle mixture is set, take the car for a test drive with the test harness connected and routed into the car for a passenger to read while under low-load cruising and acceleration conditions.

On the test drive, you are looking for a nice rich 12:1 if possible AFR under WOT/boost and a middle of the road amperage to the DPR under light cruising throttle. When the system is near the end of its range of adjustment, cruising amperage to the DPR will become very low. At the point that the cruising amperage touches zero, the ECU will no longer be able to make lean-out adjustments to correct light-load mixtures. Adjusting the system beyond this will cause poor economy with negligible (if any) power increases.

Repeat the above DPR adjustment procedure as necessary with this caveat: DPR adjustments from this point can be VERY touchy, so no more than a 1/8 turn increment per adjustment is advisable. Each time you adjust the DPR, you re-start the engine, warm it up and set idle mixture again as described above before driving. 

So far, I have found that 1/4 turn is all a stock engine needs to reach its full potential on CIS-E with a WOT switch. A 2L/big valve head/mild cam/good exhaust setup usually can take about 1/2 turn. A SUPER wild NA engine or turbo engine can use all the fuel it can get before the system can no longer adjust light load mixture--usually 3/4 turn. Beyond this, the system can usually no longer maintain a good stoich-ish mixture under light load.

When making these adjustments, remember: "Keep it real. Think slow. We should get through it just fine." Take your time and make small adjustments. Don't try to be a hero and jump to the final lesson. Each metering head, air plate and DPR will respond slightly differently based on their condition and pre-set internal adjustments. Don't rush. Use this information wisely and you will get some more useful power from your CIS-E. CIS-E is an excellent fuel system capable of excellent power and economy if properly tuned and capable of neither if jacked up and out of tram.