Whats up. I have a prelude that has a hi flow catalytic converter with a custom exhaust. The system definitely puts out a lot more smoke than usual. Is this common for high flows? Also, would a high flow trigger the check engine light?

 

if you have a 97-01 lude its common for the light to come on when you modify anything on the car as far as performance engine wise.

 

...smoke might be because there is dirt in the cat... how long have you seen the smoke... ussualy the resegnators dont smoke for too long mine soked the first few times i ran it hard... but yeah

 

a Hi Flow Cat isnt gonna throw a CEL...my advice would be to read the code to see what it is for sure...if you are blowing blk smoke then you are more than likely running rich.
this smoke combind with a CEL if I had to guess you may need to replace O2 sensor...if car has been running rich for sometime carbon may have built up and failed the sensor....Most manufacturers recommend replacing O2 sensors at about 50k miles...
so it cant hurt if youve never done it....

OEM part is expensive as all hell...most ppl use universal 4 wire BOSCH O2 sensors from the Auto parts store but you will have to use your factory plug so cut it off leaving you some slack and solder/shrink wrap it to the new sensor.


another suggestion would be to remove your EGR valve and blow it out...look for extreme carbon build up there also if running rich and blowing drk smoke....
both EGR and O2 are the only things I can think of that would produce both a CEL and smoke

 

A Hiflo cat will through the CEL if its an obd2 car. Another question, anyone know where I can get a random technologies hiflo cat for a reasonable price?

 

i back SH
yes itll throw a O2 CEL
reason: the lack of restriction and backpressure upstream of the CAT causes a big drop in EGT, the O2 sensor needs to be at LEAST 600*F or more for it to give accurate readings to the ecu, the result is that the ECU detects the BS reading from the O2 and trips back-up mode (aka limp mode, aka full rich mode).

PS - a high flow cat is really a straight pipe, or at least mine is

 

hope its not white smoke ore blue smoke.

 

If it's an o2 sensor I recommend www.prostreetonline.com got mine within 3 days of ordering for $160 shipped