Dune-Buggy.com - Tim Systems Fuel Injection Controller Testing and Tuning

Injector Flow Test: Once you have the wires properly installed it's time to do some preliminary tests and tuning. The first thing you need to check is that the fuel pump and the injectors can handle the necessary fuel flow. Make sure all fuel lines are tight and there are no fuel leaks otherwise a fire and death may result. Did I cover my butt enough by telling you to get fire extinguishers?

In this step you're going to test all 4 Injectors and the Pump for flow. Do this in a well ventilated area (preferably outside) that is free of all ignition sources: Gas heaters, wood stoves, welding and grinding sparks, cigarettes, electric motors, children with matches, etc. Also it would be a good idea to grab that spare fire extinguisher and keep it handy.

Injector Hot Wiring: Disconnect the 12 pin connector from the computer and locate the 4 wires that run to the injectors. You need to take these 4 injector control wires and wire them through a 12 volt stop lamp bulb (1157) and then to ground. The bulb serves to limit the current to the injectors.

To put it a different way, jumper the 4 injector wires together at the connector, connect them to one wire of a taillight lamp, connect the other wire of the lamp to ground. The injectors will already be wired to a 12V source so it will work.

If wired properly your ignition switch will light the bulb and all 4 injectors will spray.

Fuel Flow: Remove the injectors from the intake manifold but leave them connected to the fuel rail. Slide some fuel hose over the injectors and place the hoses in separate containers so that you can capture the fuel they will be spraying. Another option is to drill holes into 4 container tops and spray directly into the containers. This allows you to check the spray pattern as well.

At the fuel pressure regulator, take the return hose to the fuel tank and mount it so you can see the fuel that is being returned to the tank. Make sure it is securely mounted so you don't have fuel spraying around the shop.

Fake-out your Pressure Regulator: Now you need a way to make the fuel pressure regulator think it's seeing turbo boost. Adjust the air regulator on your compressor to how much max boost you think you will make. (15 pounds for example). Connect a hose from the boost reference port on the fuel regulator to the air regulator on your compressor. A cheap air tank with 15 pounds of pressure in it will work in a pinch.

Hit the Key: Turn on your ignition; the fuel pump, the taillight, and all 4 injectors should turn on. Fuel should be flowing into the gas tank and the individual injector containers. If there are any fuel leaks or fuel vapor spraying in the air, stop and fix the problem NOW. Fuel vapor is extremely volatile.

Set your fuel pressure to 30 PSI without the air hooked up and make sure your fuel pressure increases to 45 PSI when the15 PSI fake boost pressure is put on the regulator reference port. Note how much fuel is being returned to the tank with and without the extra 15 pounds of pressure. If the return fuel line goes dry when the air pressure is applied then your pump is too small to feed the injectors at max boost. If you were to run the car like this it will be too lean under boost and you will damage the engine. You must correct this by getting a bigger/better pump, connecting two in parallel, or use the Boost-A-Pump method (soon).

If the fuel pump tests ok, empty the containers that the injectors were spraying into and this time get your watch out and run the injectors for exactly 1 minute. Measure the output of each injector. Check the output against what you expected the output to be and against the other injectors. If the injectors are different by 4 or 5% then you need to fix that problem. In a port injection system you want the injector flow rate to match as closely as possible. Try cleaning the injectors, weed out the ones with the bad spray pattern, get some more, or fix the problem another way.

If everything is OK put everything back together because your going to be hearing the purr of the motor soon. Congratulations.

TPS Testing Procedure and Idle Adjustment:
Because every engine is different, you have to make some initial tuning adjustments so that the computer starts out seeing the right input from the TPS sensor on your butterfly.

The TPS knob calibrates your butterfly and TPS sensor to your engine. Along with the Idle knob, the TPS knob sets the point at which the fuel curve originates.

Turn on the ignition, but do not start the engine.
Turn the TPS knob fully CCW (counter clockwise)

TPS Sensor Adjustments: The butterfly valve on street cars will typically be fully closed at idle. They use an idle air bypass valve to allow air flow at idle. Because you have an adjustment knob now, you can take off this bypass valve. You will need to block the holes left behind and use the butterfly set screw to open up the butterfly enough to allow idle air to flow. At this point you run into one tiny problem. When you crack open up the butterfly for the idle air, you also change the voltage that the computer is going to read. Since you still want it to see .80 volts at idle you will need to adjust the TPS sensor to the .70 volt position and use the TPS knob to adjust it further to .80. The sensors are plastic and usually don't have slots, so you need to drill slots in the TPS to allow for some adjustment. An alternative is to drill a hole in the butterfly to allow most of the idle air to flow through and use the set screw to make fine adjustments. This way you won't have to slot the TPS sensor as much.

Connect a digital volt meter to the TPS test point that's located next to the connector on the computer. If you have an auto-range meter, make sure you lock the range so it doesn't switch on you.

As you open and close the butterfly you'll see that the voltage will change. It should change smoothly and it should be repeatable. Remember: The TPS sensor is the only way the computer will know how much your foot is on the throttle. A faulty or dirty TPS sensor and/or bad connections will result is poor performance and driveability.

The goal is to adjust the various pieces so that the voltage changes from .80 volts at idle to 4.50 volts or more when fully open. Most cars will come with the TPS already set to around 1.00 volt. Pull the TPS off the butterfly and make sure the voltage drops to at least .60 or .70 volts. Also make sure that it increases to above 4.3 Volts. If it doesn't, you need to get another TPS. The TPS knob can make minor adjustments to this voltage. To make larger adjustments, you will need to rotate the TPS sensor on the air valve. (See TPS Adjustment Box)

A good place to start is to turn the TPS knob all the way down (CCW) and adjust the TPS sensor on the butterfly until you read about .70 volts at the butterfly idle opening. Then turn the TPS knob until you read .80 volts.

Now turn the IDLE and MID knobs 1/2 way up; turn the TOP knob all the way up (CW) and start the motor. Remember you don't need to pump the gas anymore.

You need to adjust the TPS knob until you find the "sweet spot" where the IDLE knob will have an effect on the idle in both directions. Adjust the knobs for the fastest idle speed. If the engine runs too fast at this setting, slow it down by closing the butterfly opening a little, just like a carb. You adjust the fuel to the air. Too fast of an idle = too much air. If you can't adjust the idle high enough using the knobs, open the butterfly up a little. Remember you will need to keep an eye on the voltage reading as you do this and possibly make further adjustments to the TPS sensor, TPS knob, etc. Make small changes and gradually you will zero in on the spot where you have .80 volts at a good idle speed with the IDLE knob adjusted for the fastest idle.

Now the fun part:

Take the vehicle out and accelerate to about 2000 RPM, turn the MID knob until the engine runs smooth. You just dialed in your mid range.

NOTE: It has been noted that a different TOP know setting may be needed depending on the type of driving you do. If just cruising around and once in a while you get "on" it, that setting will be different from all-out drag racing or hill climbing.

The TOP knob has the most effect over 2500 RPM so be sure your pointed in the right direction. Turning the knob down too far will cause the engine to lay down (too lean). Turning the knob up too far should cause the engine to blubber. (too rich) If you cannot make the engine blubber you might not have enough fuel pressure or your injectors are not big enough. Try increasing the Fuel Pressure up in 5 pound increments. Generally speaking you want the lowest fuel pressure that will allow you to have the TOP knob turned almost all the way up.

Other Computer functions you should be aware of:
Flooded Engine: If the engine ever becomes flooded, floor the throttle while you crank it over. The computer will automatically turn off the injectors to dry out the motor. If the motor should start and reach 400 RPMs, this dry-out function will be disabled.

Limp Mode: If your away from home and your TPS should fail, disconnect the wires to it and the computer will revert to "limp-home-mode." The fuel mix will probably be too lean but by adjusting the other knobs you should be able to get home.

Choke: None offered. A fast running engine could cause too much oil pressure when cold especially in a full-flowed VW). The EFI controller and port injection will allow the engine to warm up to operating temperature at normal idle speed.

Tuning the Controller for a Turbo:

Once you follow the above directions and set the fuel curve with the turbo disabled, it's time to hook up the waste-gate and set the fuel enrichment for the turbo. These two knobs only work when the turbo is boosting and can only add to the fuel that the motor is receiving.

The BOOST START knob sets at what PSI you want boost enrichment to occur and when the boost light comes on. The range is from about 5" of vacuum to 5 PSI. With the ignition on and the engine off, turn the BOOST START knob CW (clockwise) until the boost light just comes on then turn the knob back until the light just turns off. This is the recommended setting and sets the Boost Enrichment to start at just above ambient pressure. ie. Whenever the turbo is adding boost to the motor, the computer will be adding enrichment fuel.

The BOOST QTY sets how much boost enrichment is added to the normal fuel curve. The range is from 0% to 100% depending on how much boost pressure there is and the engine RPM. Set this knob about half-way up as a starting point. When under boost turn the knob up until the engine just starts to blubber, then turn the knob down a little bit until the engine runs right. If you cannot make the engine blubber under full boost with the knob turned all the way up (CW) stop and fix the problem. You need to make sure you can over-richen the motor with this knob in order to make sure that your fuel system can supply enough fuel at full turbo boost.