How To Megasquirt Your 2nd Gen RX-7: Starting The Car For The First Time

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Now that the wiring and programming is complete it is time to actually start the car for the first time. As exciting as this is, there is a certain method that should be followed to eliminate a lot of the hassles that can come from firing up an untuned standalone. Don't just dive right into it. Take the advice given in these instructions.

Check The Wiring Again

Go over the wiring one more time to make sure there is nothing grossly wrong. With the laptop connected and the car powered up, the intake and coolant temp sensors should read roughly ambient temperature. The MAP sensor should show atmospheric pressure and the TPS readout should respond when you push the throttle. If something isn't working, stop and examine your wiring to figure out the problem.

Remember unplugging the ignition coils during ECU programming? You can now plug them back in.

Disable Closed Loop Idle

The last thing we want when starting the car for the first time is the idle control trying to achieve an idle when the air/fuel ratios are likely completely wrong. This will cause all manor of frustration as the idle hunts around, the car stalls or the engine revs repeatedly up and down.

MS1 users don't have a way to completely disable idle control, so just unplug the BAC valve. The idle control algorithm on the MS1 doesn't modify anything but idle valve PWM so having it turned on won't have an effect once the valve is unplugged.

MS2 and MS3X/MS3-Pro users should go to the "Startup/Idle" menu, select "Idle Control" and set the "Algorithm" to "None".

Start The Car!

With the laptop facing you or a passenger to help, crank the car over and start it up. Assuming that all the settings are entered correctly and there are no wiring errors the car should fire up fairly quickly. If you get absolutely nothing at all, you will need to check for spark and fuel. A dead giveaway to a problem is if you get no RPM reading. That means there is something wrong with how the CAS is connected, how the ignition is configured or, if applicable, how the VR circuit is constructed/configured. If it feels like it wants to start for the first few cranks and then gives up, hold the pedal to the floor to enable flood clear and release it as soon as the car starts.

Keep It Running

As soon as the car has started, catch the engine with your throttle and hold the RPMs above 2000 RPM. It is likely that it will want to stall out on you and if you let it, it may flood and make the next startup very difficult. Continue holding the RPMs high while the car warms up. At this point, start looking at your wideband. If you find the car to be very rich (richer then 12.5) then decrease fuel in the VE table at the current load point until the engine stabilizes. If you find the car to be lean (leaner then 13.0) then increase fuel. You are currently working on the VE table while the warmup enrichment is also modifying the amount of fuel the engine receives so you will have to continually modify the VE table to keep the engine running. Continue doing this until the engine has warmed and is out of cold start enrichment.

Getting An Idle

Once the engine has warmed up to the point where the Megasquirt is no longer enriching the mixture (above 160 degrees), you can try to make the car idle on its own. While observing the wideband, slowly lower the RPMs to around 1000 while adjusting the VE table to keep the AFRs around 12.5:1. With luck, the engine will now be able to idle on its own somewhere around 1000 RPM. If it wants to drop lower, then try decreasing fuel a little. If it still wants to drop, you will need an assistant if you don't already have one.

With a somewhat stable idle (or at least a car that doesn't stall), go into the engine bay and adjust the hard idle stop on the throttle body. This is a bit hard to do if you have a top mount intercooler but it is possible with a long screwdriver. Slowly bring the idle up (or down) until the engine is idling at a steady 1000 RPM. Now, adjust the VE table until the AFR is around 12.5:1 to 13.0:1. At this point only small changes should be necessary. When you are adjusting the VE table, don't just change the bin closest to where the engine is currently operating, but adjust all the bins which are close. Adjust the closest bin the most, then make minor changes to surrounding bins. This is how you achieve a smooth map. If you find the engine wants to bog out, you have gone too rich. If you find it wants to hunt, then it is too lean.

The engine should now be idling by itself, so it is time to set the base timing.

Setting The Base Timing

The Megasquirt adjusts its timing assuming that the CAS is in the correct position and that the timing it is commanding is actually what the engine is seeing. To set the position of the CAS, we need to lock the timing in the Megasquirt and physically move the CAS until the timing pointer on the engine agrees with the timing the Megasquirt is commanding.

Start by connecting up a timing light to the L1 spark plug wire. Loosen up the locknut on the CAS so that you can rotate it. Clip your timing light to L1 (or L2) and make sure that it is functional.

For MS1 users, go to the "Spark: Spark Settings" dialog and set the "Fixed Angle" to "-5". Burn those changes.

For MS2 users, go to the "Basic setup: More Ignition Settings" dialog. Drop down "Fixed Advance" to "Fixed timing" and then enter "-5" into "Timing for Fixed Advance (degrees)". Burn those changes.

MS3X/MS3-Pro users should open up "Ignition Options/Wheel Decoder" from the "Ignition Settings" menu. Then set "Fixed Advance" to "Fixed Timing" and the "Timing for Fixed Advance(degrees) to "-5". Burn those changes.

At this point, the engine has likely begun to run poorly. This is expected as timing is no longer being advanced and has been fixed at -5 degrees.

Using the timing light, adjust the position of the CAS until the pointer lines up with the yellow (leading) mark on the main pulley. Once aligned, tighten up the CAS locknut and disconnect your timing light.

Now back at the laptop, undo the timing lock. For MS1 users, go to "Spark: Spark Settings" and set the "Fixed Angle" to "-10". This tells the Megasquirt to start reading the timing from the main timing table. Burn those changes and the engine should suddenly run a lot better. MS2 users need to go back to "Basic setup: More Ignition Settings" and drop down "Fixed Advance" to select "Use table". MS3X/MS3-Pro users head back into the "Ignition Settings: Ignition Options/Wheel Decoder" and set "Fixed Advance" to "Use Table". Then burn those changes.

Calibrate The TPS Again

Changing the throttle idle stop screw has altered the position of the TPS at idle, so in order to get correct readings in Megatune/TunderStudio the TPS needs to be calibrated again. Shut down the engine and then follow the TPS calibration instructions in the Programming section of this writeup for your ECU version to recalibrate the TPS.


Pat yourself on the back and sit down again with you favourite beverages because you have just succeeded in running your car under Megasquirt control. Next in this writeup will follow a set of basic tuning instructions designed to get you started on tuning the car.

But First...

Before we move on, there is one more task to perform. Since you now know that your wiring is correct, it is a good time to wrap up the wiring harness before it gets covered in engine bay gunk. Using split loom tubing and electrical tape, wrap up the harness. Two layers of tape provides a good result. Make absolutely sure to use a tape which can survive the conditions in an engine bay long term. Many cheap tapes break down quickly under oil and turn to a sticky mess. My favourite harness wrapping tape is 3M Super 88. 4 rolls is typiclaly necessary. Don't underestimate the amount of time this task will take because you need to work around all of the clutter in the engine bay. It will likely take the better part of 2 hours to complete this task.

<< Programming The ECU (MS3X / MS3-Pro)

How To Megasquirt Your 2nd Gen RX-7
Prerequisites And Requirements
Parts List
Building and/or Modding The Megasquirt MS1/MS2
Modding And Setting Up Megasquirt MS3X
Remove Stock Wiring and ECU
Modify Stock Wiring
Mount The Megasquirt ECU
Install CLT and IAT Sensors
Wire The Megasquirt MS1/MS2 Harness Into The Car
Wire The Megasquirt MS3/MS3-Pro Harness Into The Car
Wire The ECU Panel, Wideband and Fuel Pump
Reassemble The Engine Bay
Programming The ECU (MS1)
Programming The ECU (MS2)
Programming The ECU (MS3X / MS3-Pro)
Starting The Car For The First Time
Basic Tuning
Installation Video and Resources
Basic Tuning >>

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