Stillen HFC vs. BERK HFC

RCZ · 04-15-2009, 12:34 PM

I think some of your guys are misinterpreting Stillen, this is why he edited to add that they specifically affect CEL. The rear only checks for cat deficiency. The fronts control fuel under load, aka when it matters. You can drive the car with the rear o2 sensors completely unplugged and it wont affect anything. Its the CEL's that you have to worry about if you don't like lights on the dash like me.

wstar · 04-15-2009, 12:38 PM

Quote:

Originally Posted by RCZ

I think some of your guys are misinterpreting Stillen, this is why he edited to add that they specifically affect CEL. The rear only checks for cat deficiency. The fronts control fuel under load, aka when it matters. You can drive the car with the rear o2 sensors completely unplugged and it wont affect anything. Its the CEL's that you have to worry about if you don't like lights on the dash like me.

Right, he was responding to my comment about O2 sims. While the rears are only for emissions purposes (CEL), they can't be fooled with simple sims, because the ECU is actually looking for them to respond to small changes in fuel delivery. Killing the rear O2 without a CEL would require either a very advanced O2 sim/replacement that bases its outputs on what the car is actually doing (doesn't exist), or reflashing the ECU to ignore them.

RCZ · 04-15-2009, 12:48 PM

Quote:

Originally Posted by wstar

or reflashing the ECU to ignore them.

He shoots he scores.

wstar · 04-15-2009, 03:07 PM

Quote:

Originally Posted by Jesse

Now ill rock your brains. I can problably find out exactly what the computer wants to see as far as cats and rear o2 sensors. What I mean is..... The computer is looking to see the rear o2 sensor voltage within a certian percentage of the one before it on the same bank. If we could wire a resistor between the rear o2 and the front o2 tricking the computer in seeing it within that range at all times....eliminating the need for cats at all, eliminating the rear o2sensors and eliminating the check engine light. The computer wouldnt have a problem with catalyst light off time cause it would allways be in the perfect voltage range. This may even be easier with the wide band o2's the z uses right from the factory. The voltage does not swing like old school o2sensors. This is just my nerd smog tech mechanic theory. anyone heard of someone trying this? I know I can find the information with my resources........is that a pimp idea or what?!

Odds are good anyone running HFCs or Test Pipes is going to get their ECU replaced / piggybacked / reflashed anyways, once those solutions become available. Fixing it via the ECU will be much simpler.

ChrisSlicks · 04-15-2009, 03:09 PM

In theory if the secondary O2 sensor always sends a lower voltage than the front then the resistor trick could work. However in reality it could get a little more complicated than that as I'm not sure that the voltage response of the O2 sensor is linear.

The dummy sensors are similar, however they always send back a fixed voltage according to what the ideal is supposed to be.

wstar · 04-15-2009, 03:10 PM

Quote:

Originally Posted by ChrisSlicks

In theory if the secondary O2 sensor always sends a lower voltage than the front then the resistor trick could work. However in reality it could get a little more complicated than that as I'm not sure that the voltage response of the O2 sensor is linear.

The dummy sensors are similar, however they always send back a fixed voltage according to what the ideal is supposed to be.

It's more than that even. Even the existing dummy O2's that don't work for us don't send back a fixed voltage, they send back an oscillating signal.

ETA: Making custom O2 simulators

BalanBro · 04-15-2009, 06:48 PM

I'm still wondering one thing, doesn't each bank have 2 cats (4 total for both banks?) The typical OBDII arangement was:

O2/AFR-->1st cat(usually in OEM manifold)--> 2nd O2/AFR-->2nd (downstream) cat

I was under the impression that the HFC replaces only the downstream cat (after the last sensor). So how would the sensor know whats going on further downstream? It should only be monitoring the upstream catalyst efficiency in theory.

Please tell me if I'm wrong here because I'm assuming this based on the late 90's OBDII cars I am familiar with.

wstar · 04-15-2009, 07:02 PM

Quote:

Originally Posted by BalanBro

I'm still wondering one thing, doesn't each bank have 2 cats (4 total for both banks?) The typical OBDII arangement was:

O2/AFR-->1st cat(usually in OEM manifold)--> 2nd O2/AFR-->2nd (downstream) cat

I was under the impression that the HFC replaces only the downstream cat (after the last sensor). So how would the sensor know whats going on further downstream? It should only be monitoring the upstream catalyst efficiency in theory.

Please tell me if I'm wrong here because I'm assuming this based on the late 90's OBDII cars I am familiar with.

I've never heard of 4 cats, but maybe on some weird vehicles...

Our car only has 1 cat per bank. The arrangement on our car is Exhaust Manifold -> Cat -> (rest of exhaust), and there's an O2/AFR sensor in the exhaust manifold, and another O2 sensor right after the cat. The one in the manifold is the expensive wideband one that the ECU uses to regulate AFR. The simpler O2 after the cat is just used to validate that the Cat is functioning properly.

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04-15-2009, 12:34 PM	#1 (permalink)
RCZ A True Z Fanatic Join Date: Nov 2008 Location: Miami Posts: 6,403 Drives: '09 370Z Rep Power: 1120	I think some of your guys are misinterpreting Stillen, this is why he edited to add that they specifically affect CEL. The rear only checks for cat deficiency. The fronts control fuel under load, aka when it matters. You can drive the car with the rear o2 sensors completely unplugged and it wont affect anything. Its the CEL's that you have to worry about if you don't like lights on the dash like me.

04-15-2009, 03:09 PM	#5 (permalink)
ChrisSlicks A True Z Fanatic Join Date: Mar 2009 Location: North East Posts: 6,203 Drives: 09 370Z Sport M6 Rep Power: 655	In theory if the secondary O2 sensor always sends a lower voltage than the front then the resistor trick could work. However in reality it could get a little more complicated than that as I'm not sure that the voltage response of the O2 sensor is linear. The dummy sensors are similar, however they always send back a fixed voltage according to what the ideal is supposed to be.

04-15-2009, 06:48 PM	#7 (permalink)
BalanBro Enthusiast Member Join Date: Apr 2009 Location: NJ Posts: 318 Drives: 40th Anniv. 370Z Rep Power: 1113	I'm still wondering one thing, doesn't each bank have 2 cats (4 total for both banks?) The typical OBDII arangement was: O2/AFR-->1st cat(usually in OEM manifold)--> 2nd O2/AFR-->2nd (downstream) cat I was under the impression that the HFC replaces only the downstream cat (after the last sensor). So how would the sensor know whats going on further downstream? It should only be monitoring the upstream catalyst efficiency in theory. Please tell me if I'm wrong here because I'm assuming this based on the late 90's OBDII cars I am familiar with.