I have a 70mm asura HFC on MY08. As a bit of background, this HFC has two bungs. The first located before the cat which goes straight into the exhaust stream. The other is after the cat but the bung is sealed closed completely.I was told by Asura that it was sealed intentionally as a CEL fix, but I think our o2 sensors are way too sensitive to be taken out of exhaust completely.

I have reset ecu several times and the CEL turns on within a mile or 2 in both cold and warm conditions.

Possible solutions:
Option 1 - Place the o2 sensor into the bung before the cat with the use of o2 spacer(s). The problem with this solution is that the o2 sensor will basically read the same as it would with a test pipe and I hear my MY08 do not like test pipes.

Option 2 - Drill a small hole in the o2 bung located after the cat so that the sensor can pick up more heat. Can I do this without messing up the pipe?

Option 3 - Disconnect a fuse. Can I disconnect a fuse somewhere for the o2 sensors without disabling the CEL completely? I would still like to pick up readings if something was truly wrong with my car.

 

hmm thats weird.. ihave a BERK hfc ive gotten the cel maybe once or twice but it disappeared on its own.. after like couple hundred miles of driving

 

Asura is a great guy and stands behind his products. Have you contacted him to work out a solution?

 

I contacted him and he recommended just to use the bung before the cat, but like I said I do not think that would work for a MY08.

 

I think the problem here is that the CEL fix of completely blocking the o2 sensor from exhaust stream and a MY06+ sensors might be too touchy for such a fix. Does the berk HFC do the same?

 

So here is my theory....

The o2 sensor would trigger either a cat failure code or cat efficiency code. Cat failure being that the core is clogged/restricting flow and cat efficiency is when there is too much flow (testpipe). So you have to figure that the o2 sensor will have a upper and lower limit for heat readings. Since the sensor is only picking up the heat coming from the exterior of the pipe, I highly doubt there is a enough heat put the sensor within its normal range.

FYI, I have yet to check what code my car is throwing because california passed a law that no longer allows people to borrow scanners from auto part stores and all of the shops near me wont let me use. I will have to go to honda one of these days to confirm if i am correct in my assumption that my car is throwing the cat failure code.

 

If I am in fact throwing a cat failure code, is it causing my car to run in safe mode or anything to hurt performance?... I did notice my car dropped 3 or 4 MPG after installing the test pipe.

 

Drill the hole in the bung. I have had the same problem with my AP1, and as soon as I drilled through, I haven't thrown a code since. The O2 sensor will throw a low voltage code for Primary Sensor, bank 2. 1/2" drill bit will work perfectly.

 

Wow i fail to see the purpose of that...can you at least buy i cheapy one that just reads/erase ?

 

I was under the impression that the purpose of the 2nd bung on the Asura HFC was for a wideband O2 hookup.