I have a '97 GSR that I'm building up for road race. I had a question regarding all the emissions and "non-essential" sensors for an off-road vehicle.

With an OBD2 ECU, is it possible to remove the emissions components and/or sensors without the engine going into backup or limp mode? I don't care if the ECU throws a CEL light, I just want to make sure that the motor is running normally with timing and air/fuel, etc.

If it is possible, what can all be removed, or what ECU codes can occur without the engine performance degrading? Secondary O2 sensor, purge valve, etc?

Are racers out there running OBD2 systems with the emissions installed, or are all converted over to OBD1 or Hondata type systems?

Thanks.

 

what emissions equipment are you talking about? you could use a JDM ecu to do away with your cat since it behaves like obd1 with an obd2 plug, you only need your front o2. nothing else effects performance in the slightest. even the cat barely does, especially if you run a high flow.

 

The secondary O2 sensor is one for example. As far as I understand it is just a CAT diagnostic to make sure it's there and working, otherwise disconnecting or removing it doesn't affect anything. If that's correct.

Removing the carbon canister could cause a CEL on fuel tank pressure, or a CEL regarding purge solenoid pressure. Then unplugging or removing the purge solenoid valve will cause a CEL as well. Are all these "soft codes", in that they'll trigger a CEL but not put the ECU in a backup mode?

I assume these errors wouldn't affect engine performance, but I don't have any experience with it.

From your statement above it sounds like you can get rid of the secondary O2 sensor and other vapor controls, and everything still runs 100%. You'll get the annoying CEL, if you don't pull the light that is, but otherwise everything is functional. Is that correct?

 

with the usdm computer it will go into safe mode with the light on. i have seen motors make over 200 whp with all the emissions hooked up.

 

Really? (regarding the CEL light) I'm not disagreeing with you, but I find it hard to believe, or just simply odd, that the ECU would go into safe mode just because something like Fuel Tank Pressure was out of whack. Or the Secondary O2 sensor was not correct.

I'm just trying to remove clutter. If they need to remain hooked up I'll leave them.

 

this is not true. only some codes will trigger safe mode. code 441 which is the evap purge will not cause safe mode.

 

Do you know which codes will trigger "safe mode" then? Besides setting up the car, it will help with diagnostics if something goes wrong.

If code 441 doesn't cause "safe mode" then it's something that won't immediately concern me if I'm having engine problems. Besides air leaks of course.

Thanks.

 

On my '98 Prelude it would throw a CEL emission code every 3 start cycles. The way around it was that I put a switch on the constant power wire to the ECU so that when switched off it would not power the ecu when the ignition was off. That way the ECU would never see more than 1 start cycle so no codes. I put the switch instead of just cutting the wire since there are some instances where you want to keep power to the ECU to read other CEL codes. This was on a track only car so I didn't worry too much about long term fuel trim.

 

you can leave the smog stuff on the car it would hurt that much or just run an after market ECU

 

FYI: I just got my car running again after 8 months. I only had a header pipe and neither O2 sensor was hooked up.

The ECU might be running the car "conservatively", but these specific CELs it didn't affect the VTEC engagement or rev limiter...

 

Just an FYI. I removed all the emissions equipment under the hood that dealt with the carbon canister. Left the line from the fuel tank vented into the engine compartment. Removed the solenoid valve, etc. For the CAT converter, we're faking the computer out with an O2 extension. Works like a charm.

Various road / break-in miles and 2 events so far and no CEL light for the OBD2 ECU. At least for my car it doesn't seem to be that picky...

 

Just a heads-up, that fuel tank vent line can kind of...leak, when left open into the engine bay. Had that problem on Sander's Integra at one point. I might be remembering wrong, but the solution was to just not overfill the tank.