Stock 94" TT going 15g, 550cc, flashed 98' VR4 ECU build.

[Jesters Deadd]

fix this?

[Drummer]

No, Im just a tester. I dont know if the boys working on this figured it out yet.

[Jesters Deadd]

Just put in some Lc1s and be done with it. YOu can sim the post cat O2s off the Lc1s. Or flp th periph and install one post cat O2 sim.

[Drummer]

Yea... i just really wish I could plug in the 98 VR4 ECU and simply disable the post cat 02's and have the upstream 02's work along with both of the banks trims. Im lazy :P I do have a MTX-L Innovate kit sitting at home. I was going to install it after the exhaust joins for tuning later.

[99 vr4]

Jay, yes turning off the downstream o2 sensors is a problem. Solution, don't turn them off. I have not manipulated any of the periphery on my car. Everything is factory in that regard.

Classic O2 sims do not work on the 98/99 ecu due to the way the ecu looks for o2 levels (more on this later), but there are two solutions:

1. Move the o2 sensors out of the exhaust stream with spacers.

2. I have a custom o2 sim modification that I developed that works 100%. Been passing obdii emissions with no problem for three years. I could have used method 1 because I still have to leave my o2 sensors in the car to pass "visual" inspection and the sim does not bypass the heater and heater warm up checks, just the output.

Back to the o2 sim issue. It seems the engineers at mitsubishi decided to check downstream o2 by comparing it to the upstream o2. At any given check point the downstream must read lower than the upstream. Classic o2 sims which just send a random signal to the ecu can and sometimes (read : often) do fail this check.

As far as I know this only pertains to the newer 98/99 ecu.

[Drummer]

Care to share that o2 sim mod? :P I dont plan on installing 2 more o2's, so Id rather just fool the computer into seeing them.

[99 vr4]

Check your pm for detailed info on why you need to still have the o2 sensors hidden somewhere.... I am to sick to repost the info on my cell phone...

[Drummer]

Some differences between the 94TT and the 99TT :

-The '94 EGT sensor is not used on the 99
-the 99 MAP is not on the 94
-the gas tank pressure sensor andthe EVAP vent solenoid on not installed on a '94
-The 99 manual says how the evap system works and how it uses the fuel tank pressure sensor and MAP (This is probably why my evap purge solenoid is going nuts)
-The O2 heaters are done off the MFI relay on a '94 instead of the ecu like a 99
-There are two precat O2 sensors and no post cat sensors on a '94


The ECU is expecting to see EVAP stuff that is not there, not to mention the MAP, o2's etc. Its doing strange things with the purge solenoid on my 94 because of this. Im wondering if the ECU will mess with F/A and timing when its trying to cycle the purge. Im told its probably nothing to worry about. I can either try to install the missing sensors or remove all the emmissions completely, set the periphery and forget it. Aaron has a working model of this currently. Some things can be shut off in the periphery bits, some things arent that simple (like shutting off downstream o2's causing rear trims to be lost). I may have to add the downstream o2's to get around this and just stow them.

For now the build is on hold until I get a lot of other stuff done

Thanks Blackstealth, Aaron, Jester, Greg, Jeff, Charger, Brett for the input so far.

[HLxDrummer]

Have you considered disabling the O2s altogether? Then you can do lean cruise and not have to worry about the rears. Blackstealth said he has done it and it works well.

Also, what emissions stuff do you still have/not have? I will end up deleting it all (since flashable ECUs can't really control EGR) and wondering what all to disable and what the issue your having is.

[Jesters Deadd]

Your names are too similar.