i have just purchased a jdm spec sir vtech integra and have a few problems which i hope you guys could help me with. first the guy says he has removed the catalytic convertor and put in a straight pipe but has just taped the o2 sensor up under the car ! is this affecting my engine performance ? secondly the top tank on the rad is cracked and leaking when hot, is it ok to run the car and just keep it full without doing any damage untill i save up enough for a new one ?

 

As far as I know the absense of you cat is not hurting performance. Having no o2 sensor IS hurting performance because your motor is not running at it's best. About the radiator, GET IT FIXED! Sure, you can go around waiting for it to finally give out but that's not the greatest. just check it everytime you stop somewhere and watch the temp gauge like a hawk.

 

the o2 sensor is there ziptied somewhere underneath car but i have a permanent o2 sensor light on the dash which is really annoying. from reading archives apparently this sensor is a secondary and is not linked to ecu, is this true ? is it hurting my performance and if so could i sort it ? about the rad im watchin heat guage and keeping resevoir topped up, trying to get money together for a new one. is there a possibility of hurting my head gasket by running my motor in this condition ?

 

No o2 sensor= bad gas mileage and below optimum performance. You aren't hurting your head gaskey unless you overheat.

 

how does that work if the its the secondary sensor and not connected to the ecu ? the sensor is still there can i install it with the straight pipe or would that be a bad idea ?

 

They're both connected to the ECU...

The primary O2 sensor is located upstream of the catalyst, and the ECU uses that one to keep air/fuel mixture adjusted.

The secondary O2 sensor is located downstream of the catalyst, and the ECU monitors that one to see whether the cat is working. It does NOT use this one to adjust anything.

That's how it is in USA... I'm not sure about JDM. Is there a secondary sensor? I believe they have a high-temperature warning (sensor) at the cat, but that's not the same thing.

 

well all i know is the cat is out and a straight pipe installed and i have a constant red light on the dash which looks like a catalytic convertor !

 

I think that's the high-temperature warning. In USA the 2nd O2 sensor sets off the check-engine light.

 

The second 02 sensor does alter air/fuel mixture and without it your car will run lean and could cause some problems.
Do a search for 02 sim chips they are really cheap and you solder them on your ecu and it tricks the ecu into thinking the 02 sensor is still working properly.
Do not remove the 02 sensor because the computer will still check to see if it is heating. (it has a heating element in it)

 

so at the moment with the cat being removed and the o2 sensor not installed am i getting any improvement on engine performance or would i be better off installing the cat and o2 sensor back in untill i get the o2 simulator ?

 

I think first you've got to straighten out a high-temperature warning vs. a secondary O2 sensor. I really thought the whole 2nd sensor business was a US EPA thing, & I don't know how that plays in a JDM ECU. The red warning light shaped like a cat is not the malfunction indicator lamp (MIL).

If the thing you've got taped up is the primary O2 sensor, then YES you need to install a bung somewhere & put that sensor into the exhaust stream. If that thing is the high-temperature warning sensor, that's different...