A couple guys are putting an eBay hi flow "cat" (I use that term very, very
loosely) on their Si's, myself included.

Despite the seller's comments (surprise), the test pipe does throw a CEL.

My question is, does this hurt performance? Does it cause the ECU to do anything
funky? So far, I've driven about 2000 miles with it on (FL to NC and back) and
while my gas mileage seemed a tad poor, it didn't seem to affect anything. City
driving didn't seem affected, either. But I don't have any sort of logging tool and
aren't positive about this.

I took the car to Honda for an oil change, but they just cleared the code and told
me why (duh) and didn't say anything about short/long term effects.

Note that this is the odd looking CEL light (it doesn't say "Check Engine Light") on
a 2003 Si.
The pipe looks something like:

 

from what the guys on clubrsx say about CELs from testpipes/race headers, is that it doesn't effect performance of the engine.

On a different note: I wonder how a shorty header + your test pipe stack up against a race header like the JR.

 

Cool, that's kind of what I was guessing was
the case (that it didn't really affect anything).

Not sure about stacking up against another
header, if I had my car I'd dyno it. Maybe in a
few weeks or early January.

 

Hmmm.... i wonder, becuase on other hondas when you throw a code for no cat it instantly runs you in limp mode, in other words really damn rich. I wonder if that happens on rsx's too.

 

there is an o2 simulator that is out for the RSX that supposed to take care of the CEL. Try http://www.casperselectronics.com/. Btw, what did you type in on ebay to get tht converter to come up? will it fit the rsx?

 

Chech this link http://forums.clubrsx.com/show...O2SIM
They have reports that the DC5 and EP3 have some sort of "active" O-2 sensor reading by the ecu. There were guys running race headers and ignoring their M.I.L. and after a while the primary o-s sensor (air/fuel meter) was failing...Causing poor engine performance, and possibly damage. The company Casper Electronics evidently has the cure for @75-80.00 with an active O-2 sensor that fluctuates the voltage readings to the ecu so it thinks that the sensor is there and alive and well.

 

Yeah I have the o2 sim but haven't put everything together because I have to replace my front sensor. Will that cat fit on the RSX's?

 

Bump for this.

Not sure if that cat will fit an RSX (especially
RSX-S). I think there are hi-flow cats geared
for the RSX though, too.

I found this on eBay using the following search
terms:
(02, 03, 2003, 2004, 2002, 04) civic (si, ep3, rsx)
(I saved the search, makes it easier).

There was some more discussion today on
ephatch about how the CEL will cause the
engine to run rich/lean, trying to get the cat
where it should be. I'm wondering if anyone
has seen this during any logging (specifically
Jack and the other hardcore tuners, if they
have come across CELs like this).

Thanks in advance...