Stillen HFC vs. BERK HFC

Originally Posted by wstar

or reflashing the ECU to ignore them.

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?!

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.

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.

Originally Posted by BerkTech

The ECU will only look at the secondary O2 sensor during closed loop operation (i.e. lean burn, steady freeway cruise, idle, etc). The ECU will make small adjustments to the fuel trims based on the small adjustments made during closed loop operation. This is on the order of a few percentage points. I don't recall ever seeing anything over +/-5% in the last couple of years.

If you guys have ever called Berk for tech support you've heard us say, "Clear the ECU learned values before running the HFC's. You will run less of a chance of throwing a CEL light". Over time your ECU may have adjusted based on your driving habits. By clearing the fuel trims you give your ECU a chance to start back at zero and readjust to the new cats. The cat is in essence an oxygen storage device. When installing a BERK HFC that flows twice as much as the OEM cat it does not have enough contact time with the catalyst to "scrub" the exhaust gas and let the reaction occur. So the O2 readings will be different. Most of the time the thresholds of CEL or no CEL are large enough that the ECU will readapt and the CEL will stay off. However some of you who were already operating on the outer range will pass that threshold after a few drive cycles and illuminate the CEL light.

During driving situations where the engine sees load it will completely ignore the secondary O2 sensor and go off of it's pre-programs maps. On one of our race cars we actually did not use any O2 sensors at all! We would run completely off the pre-programed maps on the stand alone. We would make small tweaks to the maps for high altitude race tracks and summer/winter weather.

So, the moral of the story..... the secondary O2 sensors technically DO make tiny fuel adjustments in concert with the primary wide band sensor in the header, but only to make the car run as clean and lean as possible during steady cruise. From the stand point of the car enthusiast, they don't do squat!

And to set the record straight in plain black and white:

Berk HFC's are not SMOG legal in CA. Can they pass a sniffer test? Yes, all the time. But Berk Technology does not guarantee emmisions performance.

The vast majority of you will never thorw a CEL. However there is a very small percentage of you who will throw the occasional P0420/P0430 CEL. Down the road there will also be a very small percentage of you who throw those CEL codes with the OEM cats!

Hope that gives you some good info to chew on!

Cheers guys!
Berk Technology

Originally Posted by JvKintheUSA

How do you "Clear the ECU learned values?"

Originally Posted by Jesse

Cats are not oxygen storage devices. They convert carbon monoxide ( CO) Hydrocarbons (HC) and oxides of nitrogen (NOx), into more friendly Carbon Dioxide and water. The precious metals used in the manufacture of cats (platinum, rhodium and palladium) will clean themselves if the input gasses are in the correct ratios. that is why it is critical that a vehicles fuel management system and air injection system are working properly (going from slightly rich to slightly lean) and injecting air at the right places at the right time (if air equiped).

Both the 'dual bed' and 'monolith' cats need differing amounts of oxygen to perform the gas conversions. The platinum or palladium metals require high levels of O2 to convert CO (carbon monoxide) and HC (raw fuel 'hydrocarbons') into water (H2O) and carbon dioxide (CO2). The rhodium element however operates well in the absence of oxygen to convert NOx into NO and O2. By comparison, the single bed catalyst only works on CO and HC.

In no way does a computer adjust to accommodate different catalysts (hence cel). The computer is programmed to 'feed' the cat to make it as efficient as possible and watch its degradation over time setting a code once it gets below a certian efficiency.

Also, closed loop is not 'lean burn, steady cruse, or idling. Closed loop simply means the oxygen sensors are heated enough to control fuel. (some cars coolant temp needs to be up also).

all engines are different and degrade so a 'fuel trim' is incorporated. I believe the limits to set a cel are +/-13percent.....I think....been a while since I reviewed this basic stuff.

Your computer does NOT adjust to your driving habits it just learns what the MOTOR needs at different conditions. Your computer is not going to re-tune itself to a race setting just because you race it. Now it may feel better over time if your computer is still learning to adjust to something like intake and exhaust. if these items increase air flow, your computer will learn over time to adjust with more fuel....making more power. You guys should drive your vehicle a couple weeks before you dyno your new parts!!!

By the way...your basically saying your cats flow good, but are crap when it comes to doing the job a cat was meant to do....CONVERT!

and your quote "During driving situations where the engine sees load it will completely ignore the secondary O2 sensor and go off of it's pre-programs maps. " ----what are you talking about? when your driving the engine is always under load unless you take your foot off going downhill. Your computer uses pre-loaded maps when under HARD acceleration. Also, your computer wants to see you driving a certian way before it will even run a catalyst monitor. For example, it wont check the cat if you go over 65mph or if your throttle position sensor is all over the place, if there is a problem with another sensor or not under the right load.....ect.

Your race car runs pre-programmed cause you have tuned tuned tuned with a dyno and you know what you want the settings at. In the real world for everyday driving in a car that changes over time...this wont work well. you would have to have a computer that adapts to the changing engine or keep re-tuning it every so many years.

Sorry to rant and rave...I think I got a contact high from my roomate. And he wont shut up about his Vegas trip!

Originally Posted by Jesse

Nope. your wrong bro. the car just has not learned what the engine needs at those conditions. once you put the engine in those conditions it learns what it needs and eventually feels better than before. I dont want anyone to think im just full of hot air. I dont know everything, and im still only 27. But my acomplishments include.......

ASE certs---A6 (auto electrical) A8 (engine performance) L1 (advanced engine performance), BAR clean air car course class and test, BAR laws and regulations class and test, BAR update class '05, '07 and just finished '09 (and tests). Auto 101, intermidiate auto, advanced auto at local college (which is known to have the likes of people like ARMY drag team shoemacher mechanics). Three years of auto in high school. 2 years interning as a smog tech with the number 2 (tested) mentor in the state. 6 or 7 years as a smog tech and mechanic at the most honest shop. Most days I smog 20 to 30 cars every day by myself. I have taken countless factory training courses in ford chevy and chrystler. I have rebuilt motors by hand, tuned turbo hondas. AC delco has classes i have taken. I have done a lot in my short life span, but I dont know it all....like to think I do sometimes I guess. But I think im pretty good about admitting when im not sure.

Damn.....I know I have done more than that....I just woke up. ill be at work today and more will come to me. But thats off the top of my head.