E-manage ignition timing with DLI 4AGZE and 7MGTE engines Background Some Toyota ECUs (such as the 4AGZE and 7MGTE) expect a return signal from the Ignitor for each ignition signal sent. The expected IGf signal is a ground signal (from the igniters) in response to a charge signal (from the IGt ECU point to the igniter). Problem When using the e-manage s ignition harness with these ECUs the maximum advance/retard that can be set is around +/- 6 degrees. Any more than this will result in an error being detected as there will be a time difference between the IGt signal being sent and the IGf signal being received by the ECU. This will result in the Check Engine light coming on, base ignition timing being set and in some cases the injectors may be shut-off. This restricts usage of the e-manage s ignition timing function to only +/- 6 degrees. Solution There is an IGf Signal Generation Circuit within the Igniter which creates the IGf signal using a switching transistor from the same signal that is sent out of the igniter to the ignition coil. This circuit can be created external to the igniter and can be used to generate an IGf signal directly from the ECUs IGt signal before the e-manage intercepts (and alters) the IGt signal. Using this external circuit, the ECU is provided with a consistent IGf signal even if the actual ignition event is earlier or later than the IGt signal is triggering. ECU Ground External IGf generation circuit CH1 out CH1 in E-manage Ignition Harness Page 1 of 5
Making the circuit You will need the following tools: Soldering iron (and solder) Wire stripper 2cm Heat-shrink tubing (and lighter). You will need the following parts: NPN 2N3904 switching transistor 1watt 1K (1000) ohm resister Veroboard (at least 3x9 holes) 3 x 10cm lengths of different coloured wires. 1. Cutdown the veroboard using a hacksaw or sharp knife to the correct size. Note: I found some veroboard that had 2 complete tracks and then 2 broken tracks and cut it so there was a complete track along each long edge and 2 incomplete tracks in the middle. 2. Bend the pins of the transistor so it can be inserted in the veroboard. 3. Bend the ends of the resistor so it can be inserted veroboard. Your parts should look something like this: 4. Solder the transistor into one end of the veroboard so that pin 1 and pin 3 are using the complete tracks. Note: refer to picture below for pin locations on the transistor. 5. Solder the resistor in-line with pin 2 and bridge the points between pin 2 and the resistor. 6. If you have used veroboard without complete tracks, solder links between pin 1 and the end of that track and pin 3 and the end of that track. 7. Solder the 3 different colour wires onto each of the 3 track ends and note which colours you used for each of the pins. 8. Clip off the excess pins and wires from the back of the veroboard, check over all of your connections and either heat-shrink the circuit or install it in a small box for protection. Page 2 of 5
This is the circuit using a veroboard with tracks: This is the circuit using a veroboard without tracks (and therefore with links): Installing the circuit (permanently) 1. Cut the IGt wire farther away from the ECU than where the RPM signal has been spliced into it. 2. Solder the CH1 in wire (from the ignition harness) and the pin 2 wire (from the external IGf generation circuit) to the IGt wire coming from the ECU and heat-shrink the joint to protect it. 3. Solder the CH1 out wire to the IGt wire going to the igniter and heat-shrink the joint to protect it. 4. Splice the pin 1 wire (from the external IGf generation circuit) to the ECU ground wire (which you used for the E-manage ground: E) and heat-shrink the joint to protect it. 5. Cut the IGf wire at a similar length from the ECU as the IGt was cut. 6. Solder the pin 3 wire (from the external IGf generation circuit) to the IGf wire going to the ECU and heat-shrink the joint to protect it. 7. Heat-shrink the IGf wire coming from the igniter to protect it from shorting out. Installing the circuit (non-permanently) As the IGf signal is a fail-safe feature, bypassing the true IGf signal (from the igniter) will remove the fault checking capability of the igniter/ecu. Therefore, you may want to consider installing the circuit using bullet connectors on the IGf wire so that you can swap the external IGf generated signal with the true IGf signal easily. To install the circuit in this manner, perform steps 1-5 and: 6. Install a male bullet connector on the IGf wire going to the ECU 7. Install a female bullet connector on the pin 3 wire (from the external IGf generation circuit) 8. Install a female bullet connector on the IGf wire coming from the igniter and heat-shrink the connector to protect it from shorting out. 9. Connect the male bullet (on the IGf wire going to the ECU) to the female bullet going to the IGf generation circuit. Page 3 of 5
I went one step further and used bullet connectors for all of the connections (so I can remove the whole circuit if I need to). The top wire in the above picture is the ground signal (which has a male bullet coming off for the e- manage ground wire). I tapped a small wire with a male bullet off a ground point on the ECU. The middle wire (which has an adapted splitter that comes with the e-manage) is the IGt feed. The male bullet goes into a female bullet attached to the IGt point on the ECU (see below picture) and the two female points are used for the e-manage CH1 in signal and the e-mange RPM signal. Finally the bottom wire is the IGf generator wire which is connected as described in steps 6 to 9 above. Note: you can easily remove the pins from an ECU plug (see above) by inserting a small screwdriver into the plug from the ECU side and levering the small tab that holds the point in. You can then pull on the wire and the point will slide out of the plug (don t forget which point it came out from!). If you ever need to check to see if your igniter is faulty, you can: 1. Change to an ignition map that has less than +/- 6 degrees of advance/retard (it is probably best to switch to a standard map with all zeros) 2. Swap the pin 3 wire (coming from the external IGf generation circuit) with the IGf wire coming from the igniter by disconnecting the joint and connecting the other female bullet. Page 4 of 5
How does it work? An NPN transistor is a small and fast switch that allows a signal to flow from the collector to the emitter when a signal is received from the base. In the IGf generation circuit, when there is an IGt signal (connected to the base) the transistor permits a signal to flow from the ECU Ground (connected to the collector) to the IGf input on the ECU (connected to the emitter) which grounds the IGf point each time an IGt signal is received. Other thoughts/information Although the DLI setup also uses another ECU signal to the igniter (IGd on 4AGZE and IGdA/IGdB on 7MGTE) to trigger which coil to fire, intercepting the IGt signal and selecting a distributor configuration works fine. This is initially a little confusing, but looking at the following picture shows that the IGt signal is constantly oscillating regardless of which coil is being fired. References and thanks Thanks to Rollamods from www.twincam.org for informing me of the Greddy e-manage and also the existence of this circuit (and for the second photo of the circuit). Thanks to tsupra33 from the E-manage Yahoo Group for the diagram of the 7MGTE circuit in the files section of the E-manage Yahoo Group. Major thanks to John Simmerman from the Supra Owners Group International (SOGI) for originally designing the circuit. Diagrams of Toyota ignition setup came from www.autoshop101.com. Definition of transistor s operation is loosely based on an explanation given in the Beginner s Guide to Electronics by Martin T. Pickering available free from The Cool Bookshop. Cheers, JamitGZE. Page 5 of 5