#LS STOCK ECU TUNING HOW TO#

Both systems ‘think’ they are in control of the engine, as they are processing all of the incoming information from these sensor inputs, and they are sending the corresponding OUTPUT signals in the way of fuel injector pulsewidths and ignition pulses. So what have you really done here?īasically, your goal in the above is to make sure that both the stock ECU and the MegaSquirt EMS have the INPUTS they need from all the necessary sensors so they can both independently make all of the calculations needed to control your engine. Another case where it pays to have separate sensors for the MegaSquirt and the stock ECU. These often don’t work with stock ECUs, so your best bet is to weld in a second bung for the wideband sensor. However, there’s a good chance you will want to add a wideband O2 sensor at some point, in order to give the MegaSquirt more tuning information. Oxygen sensor: It’s perfectly OK to share narrow band oxygen sensors with the stock ECU. Often, you can solve this by removing the pull up resistor from the MegaSquirt. If this happens, one or both of the ECUs will not get an RPM signal. Solution– don’t wire it backwards! With Hall effect or optical sensors, sometimes the combination of pull up resistors in the MegaSquirt and stock ECU can interfere with each other. If you have a VR sensor and you connect the sensor to the MegaSquirt backwards, you could possibly ground the sensor and wipe out its signal. IF your unsure of what to do here, your safest option is to provide the MegaSquirt with its own CLT and IAT sensors, separate from the stock CLT/IAT sensors that the factory ECU will continue to use.Ĭrankshaft position sensor / camshaft position sensor: These are sensors you can usually share with the stock ECU, but there are a few issues that can cause the MegasSquirt to not play nice with them. On some ECUs, like most GM computers, you cannot share temperature sensors with the stock ECU at all.

#LS STOCK ECU TUNING HOW TO#

This link provides more detailed information about how to share temperature sensors between the MegaSquirt and stock ECU. To do this, you will need to remove the R4 and R7 bias resistors from the MegaSquirt and determine the bias resistors the stock ECU uses, then calibrate the MegaSquirt appropriately. On some ECUs, like the early Miatas, it is possible to get the MegaSquirt and the stock ECU to both use the same sensor. Temperature sensors: These are a bit problematic.

You should not try connecting the Megasquirt’s VREF wire to the TPS, as tying two VREF signals together can cause problems. Just splice the Megasquirt TPS signal wire in to the signal wire to the stock ECU. If it never goes above 5 volts, and if its voltage increases as the throttle opens, you can use this sensor with MegaSquirt. Throttle position sensor: Check the TPS signal running to the stock ECU with a volt meter. MAP sensor: The MegaSquirt EMS has it’s own dedicated MAP sensor built in, so you will just need to add an extra vacuum line for it. These guidelines will help you deal with the sensors the MegaSquirt needs. Often the toughest issue is what to do about sensors. You can do this with injectors, coils, IAC valves, and most anything the MegaSquirt can control. Installing the MegaSquirt in parallel amounts to disconnecting the stock ECU from what you need to tune, and connecting these things to the MegaSquirt instead. The MegaSquirt does not change any signals instead, it will take over functions of the stock ECU outright. Sometimes this approach is called a piggyback, but that can cause a bit of confusion with systems like the Apex’i SAFC, which modifies signals to or from the stock computer. The whole idea behind a parallel installation is letting the MegaSquirt take control of what you’d like it to control (the fuel injectors and ignition system most commonly) without interfering with other systems that the factory ECU may control that may or may not really be engine management related. On a car like that, the solution is what’s called a parallel installation. Or you may have an ECU that controls the automatic transmission, has the voltage regulator for the alternator inside it, controls a drive by wire throttle, or has other features that aren’t easy to control with MegaSquirt. On some installations, you might want to have the MegaSquirt control just the fuel and would rather not deal with having to tune the ignition. There’s several reasons why you might want to do this.

While there are many cars where MegaSquirt can completely replace the stock ECU, on some cars you’ll need to leave the stock ECU in place.

Ls stock ecu tuning