Megasquirt and emissions testing

My county verifies my '99 Tacoma is emissions compliant with an OBD2 scan (no visual, no tailpipe, just zero tolerance for CELs). I'm interested in turbocharging the motor (2rz) and also maintaining emissions compliance. I have no experience with turbocharging or with Megasquirt, but I'm interested in learning more about both. I see three approaches:

1) Stock fuel management - low boost (boring) 2) Piggyback or Megasquirt in a piggyback configuration 3) Megasquirt in a plug-n-play format and swap back the stock ECU for emissions testing

Option 3 is the most interesting to me. I'm still in the researching stage, but having a hard time finding much information on the feasibility of swapping ECUs back and forth. Anyone have experience doing anything similar? Other advice?

My only experience with the Manic Miata was horrid. It had a Link ECU in the stock housing, supercharger, and a bunch of other crap. I tried (for a year!) setting the car back to approximate stock, in various configurations, and never got the stock ECU to give a READY condition, even though it wouldn't throw any codes, or even any pending codes. Beware, or have a Plan B.

If your county is only looking at the dashboard for the light, you can pass by just removing the bulb.

But, far more likely is they are connecting to the ECU via the OBD port, and checking the readiness codes. That's a problem. You can check the piggyback results yourself via an ELM-27 scanner and the Torque app. If it doesn't give the code count necessary to pass, you're likely going with option #3 when it comes time to pass emissions.

Which is the fancy version of what all of us did years ago for tailpipe testing. We'd all detune our cars to pass the test, then retune as soon as we got home.

There may be an option #4.

Some ECUs are hackable, and can be tuned to run forced induction, or other far from stock conditions. Some can even be programmed to ignore certain things that could set off the CEL.

I have no idea if the Toyota ECUs can do any of that, but it's worth looking into.

Does your state or county have a law that you are emissions exempt if you don't go over certain milage?

Pennsylvania is 5k miles, if you are under that each year, you don't need to go through a emissions test. So most people around here that want to turbo something and pass emissions, go get a second cluster, and just swap the old cluster in when it's time to get their inspection/emissions checked.

Yeah the dealership will have an issue, but most independent shops won't care. So long as you don't leave your second cluster on the passenger seat.

Option 4)

Run it on the MS, but keep the stock ECU and connect it to either resistors or diodes, instead sensors/injectors, etc. so it thinks it's running a motor. You're just giving it the values it's looking for, so it should never set a code.

HappyAndy wrote: Some ECUs are hackable, and can be tuned to run forced induction, or other far from stock conditions. Some can even be programmed to ignore certain things that could set off the CEL.

I have a supercharger on my Focus. The stock ECU was reprogrammed and I have not had any problems. I have put it thru the MD OBDII emissions testing 4 times now with no problems.

Zomby Woof wrote: Option 4) Run it on the MS, but keep the stock ECU and connect it to either resistors or diodes, instead sensors/injectors, etc. so it thinks it's running a motor. You're just giving it the values it's looking for, so it should never set a code.

Don't know if you're joking but it would be ridiculously difficult to replicate every engine function sensor correctly with a resistor or diode.

HappyAndy wrote: There may be an option #4. Some ECUs are hackable, and can be tuned to run forced induction, or other far from stock conditions. Some can even be programmed to ignore certain things that could set off the CEL. I have no idea if the Toyota ECUs can do any of that, but it's worth looking into.

This is the best way, IMO.

I mean, uh, it would be wrong to bypass emissions testing by retuning the computer, because some nefarious tuners will do things like disabling certain things so that it always passes a misfire monitor even though it idles like a bowling ball in a clothes dryer, or always passes the catalyst monitor even though they are long, long gone. That sort of thing is illegal and unethical and possibly fattening and you shouldn't do that.

drdisque wrote:

Zomby Woof wrote: Option 4) Run it on the MS, but keep the stock ECU and connect it to either resistors or diodes, instead sensors/injectors, etc. so it thinks it's running a motor. You're just giving it the values it's looking for, so it should never set a code.

Don't know if you're joking but it would be ridiculously difficult to replicate every engine function sensor correctly with a resistor or diode.

It wouldn't be difficult, it would be impossible! The computer doesn't look for "resistance HERE" it looks for things like how soon and how fast the rear O2 switches compared to the front O2, or timed pressure drop on the fuel tank when the purge and vent solenoids are shut (this is GM method, Toyota has some really bizarre arcane E36 M3 when it comes to evap monitoring, makes Chrysler look sane) (actually Chrysler is really awesome in theory, highly well engineered... but it has moving parts so it fails sometimes) or it watches the O2s when it opens X to see if Y is flowing and so on and so forth...

You could probably spend a few weeks/months poring over documents to see what the computer is looking for and program a PLC to fake those things... and by trial and error find out the things that are not documented... or you could see if something like AccessPort is available for your PCM.

All ECUS are hackable, some just have already been figured out and have a handy write up to make it easy. Then again, some of them are probably already so hacked a person with little regard for the law could likely make a GM ECU say its a Toyota Tacoma ECU (with the proper Toyota VIN number and everything) and everything is just dandy even though it's only connections are power, the factory OBD2 port, and maybe some sensor inputs to make a believable live data screen.

I know for a fact that HP Tuners will not allow you to enter a VIN that does not match what the PCM's operating systems was for. (If you have a truck OS then the VIN must jibe with what a GM truck would have)

Other tuning software, and I can't think of the name offhand, WILL allow you to program any old VIN in there. There are people with, say, LS1 engined BMWs, with a BMW VIN in the GM computer, and they pass a scantool emissions test. Of course this is with full catalysts and a transplanted GM evap setup (it's very swappable) and everything

I have a 3400 swap in the longterm RX-7 plans... it will be with a GM PCM and I plan on doing catalysts/swapping the evap monitoring stuff in too, because it doesn't hurt anything to have and it makes the car more planet-friendly so why not?

drdisque wrote:

Zomby Woof wrote: Option 4) Run it on the MS, but keep the stock ECU and connect it to either resistors or diodes, instead sensors/injectors, etc. so it thinks it's running a motor. You're just giving it the values it's looking for, so it should never set a code.

Don't know if you're joking but it would be ridiculously difficult to replicate every engine function sensor correctly with a resistor or diode.

Not joking. You don't have to do all of them for it to work. Some sensors will still work as they should. It can be done.

I have done #3 and it can made to work. Biggest pain in the rear is putting enough stock stuff to make it work.

Zomby Woof wrote: Not joking. You don't have to do all of them for it to work. Some sensors will still work as they should. It can be done.

So when the computer tries opening the EGR valve and doesn't see the appropriate drop in MAP/change in fuel trim to indicate that flow is occuring (for example) how are you going to get around that with a resistor?

OBD-II internal diagnostics is waaay more sophisticated than just checking to make sure things are plugged in, which is all a resistor or diode is going to be able to fake.

Let it run the EGR and put a zener diode on the MAP so it doesn't go out of value under boost.

Checking back in. Sounds like at some point I'm going to have to take the plunge and deal with issues whether I do a parallel install or standalone/stock ecu swap. I'll keep researching and reading. Thanks for the replies and tips.

Zomby Woof wrote: Let it run the EGR and put a zener diode on the MAP so it doesn't go out of value under boost.

What if it is watching fuel trims? Let the computer control fuel too...

Knurled wrote: I know for a fact that HP Tuners will not allow you to enter a VIN that does not match what the PCM's operating systems was for. (If you have a truck OS then the VIN must jibe with what a GM truck would have)

HP tuners can jump off a cliff, survive, and slowly die.

EFI Live is much better, and doesn't have some hokey "Buy more credits for each reflash" nonsense.

In reply to yamaha:

Yah... guess which one we went with...

I guess it made sense at the time, but it is easy to rack up a ton of credits. Say you swap to drive by cable, need to register the PCM and the program that you're throwing in, so that is four credits ($200) right there. Then you update it to realtime tuning or 2/3-bar MAP-based OS and it's another two credits on top of that.

OTOH, at least for the common V8s, the support is very good. I haven't played with EFI Live to say which is "better".