took off the straight mini cats and left only the angled units. just back from a good hours run, and I thought everything was great, until a mile from home and the codes returned.....uggg. FWIW: it took A LOT longer for the codes to show up, so something is different using the only the angled ones. what it all means, no idea......LOL If there are others that have never been able to eliminate these codes, I could live with that, but.......I would prefer to make every possible effort to straighten this out Can we agree that this is merely a nuisance, and there is no "problem?" Does the post O2 sensor report back to the ECU and change fueling or anything else? Or is this simply designed to report a bad CAT? Hoping its only the later...Gotta believe that there is a solution. It did take a good deal longer for the codes to appear......
Post the data for LTFT'S and STFT'S. What readings did the scanner give you from monitoring?. Can't help you without more info regarding voltages. Remember to read previous posts to help diagnose. It's not a nuisance there is a problem
Paul's case is different from yours as he has Cats but aftermarket, with probably somewhat lower efficiency which had to be compensated for. You have no Cats which is more difficult. The post-cat o2 sensors (like the pre-cat ones) are only recognising the amount of oxygen in the exhaust gasses and do not "know" about the content of other gasses that make the exhaust cleaner or more pollutive. The amount of oxygen is continuously varied by the engine ECU, based on the input from the pre-cat sensor, as it varies the mixture by a small percentage below and above the stoichiometric value. This variation causes the pre-cat sensor voltage to fluctuate (normal occurrence). The Cat smoothens out these fluctuations of oxygen and this is why the post-cat sensor's voltage is relatively steady. With no Cats, the extension or the elbow are supposed to prevent too much fluctuating content of oxygen from reaching the post-cat sensor but, at the same time, there shouldn't be too much or too little oxygen on the sensor. So, you need to keep experimenting. Not an easy task but I hope you will succeed.
I think we've been through this before Image Unavailable, Please Login In this case, I don't think it will be doing much correcting (since the O2 sensors are new), but how does it correct for front sensor aging?
In that case, I have to correct myself. I did not find similar text in the case of 2.7 348 and 355 where the post-cat o2 sensors are not even mentioned (perhaps they did not have them). The section for 5.2 355 contains the text Ian posted above. I also looked at the description of the functions of pre & post cat sensors in the case of my 1999 Daimler Super V8 and, for the post-cat, it only mentions "determination of catalyst conversion efficiency". Some other articles I read state that the method of how the mixture control is achieved (i.e. whether and to what extent is the post-cat sensor signal used for mixture control) varies between different car manufacturers and that it is more a feature of newer designs. This is an extract from the Bosch Automotive Handbook: " the upstream lambda sensor is heavily stressed by high temperatures and untreated exhaust gas, which impacts sensor accuracy as voltage readings can shift due to changing exhaust gas compositions. downstream lambda sensors are not as susceptible to impact on sensor accuracy, but are slower to respond to dynamic changes and mixture changes Two-sensor lambda control combines the beneficial aspects of both upstream and downstream sensors Greater accuracy is achieved with two-sensor control. Here, a slower correction control loop is superimposed on the two-step or continuous-action lambda control described by means of an additional two-step lambda sensor. The voltage of the two-step sensor downstream of the catalytic converter is compared with a set point value (e.g. 600 mV) for this purpose. On this basis the control evaluates the deviations from the set point value and additionally alters additively the controlled rich or lean shift of the first control loop of a two-step control or the set point value of a continuous-action control." In the case of 5.2 355, perhaps the post-cat sensor signal is used to help setting the mixture correctly when the pre-cat starts showing signs of being "tired" - maybe when its fluctuating signal from 0.1 - 0.9 volt gets narrower to, say, 0.3 - 0.7 volt?
Yes, you won;t find discussion of post cats O2 sensors for 2.7 cars because THEY DON'T HAVE THEM. They are only on OBD II cars. One of the reasons I bought an 95, OBD I car. Those of use with 2.7 cars don't have to worry about this silliness. The way to fix the car is to put cats on it, at lease high flow cats, and see if the problem goes away. Then at least you know exactly what you are dealing with.
That is encouraging.........I think......Does that mean that with new/healthy O2 sensors, I don't need to worry about mixture changes? That is my biggest issue: If the post sensors are mucking up my mixture, then it would be critical for me to find a solution. Not even close to throwing in the towel, just not sure what experimenting I should be doing? Any other ideas? Should I stuff the angled units with steel wool? Miro, do you believe that this can be resolved, or.....are there certain circumstances where it just needs to be tolerated?
Let me restate that changing the configuration of the spacers did change the reaction time the codes became present...... With the mini cat spacers stacked on top of the angled units, The codes came back within a few miles and a few minutes. Yesterday, when I removed the mini cats and only used the angled spacers, I drove for over an hour before the codes came back....hmmm Does this give anyone some additional insight?
Perhaps you can try mini cats first and angled on top of them (if space allows). If no improvement, then you can try with just angled and some steel wool inside.
I did not know you had test pipes. I thought rebuilt cats. Data from your scanner is definitely required but as John stated I think install cats.
Update: Smoke test confirms leak at all three of the muffler connections: On the left is the flange at rear of CAT bypass pipe removed from car, and on the right is the Hill Engineering flange, Image Unavailable, Please Login Here is the parts manual image of part #28, which does not resemble what I removed: Image Unavailable, Please Login It is obvious that when clamp #31 is tightened on the wrong flange, the other side of the flange would mushroom and create a leak. New flange should solve that one. Would this post CAT pipe leak have anything to do with LTFT or 0422/0432 codes??
It looks like the flange you took off your car has a 90 degree angle, and that will do nothing to seal the exhaust. The correct flanges need an angle so when you tighten the clamp it presses the cat/muffler junction together. I bought nice stainless V-band clamps off Amazon for $14 each to replace the factory garbage parts.
By "CAT bypass pipe", you mean the "catalyst replacement " (item 11 in the parts manual)? Image Unavailable, Please Login @Beetle had some codes generated by a leaky thermocouple. The flange is further away and downstream so I'm not sure if it could cause problems. I just don't understand how external air can get into the system if the exhaust gas has a positive pressure (unless it's due to a venturi effect). When I had my cats and V clamps replaced (with new items), the tech used some kind of heat resistant packing at the joints. It was a little unsightly, but did the job. Anyway, it sounds like you need to fit those #28's. So you also have a leak at the exhaust bypass valve entry point? As a reminder to readers, 0422 is cat efficiency and 0432 is cat efficiency (bank 2). I guess 0422 refers to bank 1 (?). "Below threshold (max).... 2) check for exhaust leaks..."
Yes. I have the Fabspeed SS pipes; same as item #21. Yes. The leak was minor, but it was "smoking" at the joint. Hoping this will clear up my 1448?? Also looked like I might have had a leak at the donut just before the bypass pipe on bank 2, but not certain. The pre sensor on same bank was not fully tighten. THAT MY FAULT So you think the 0422/0432 were due to leaks? Even if they were downstream? That sound great! Looking forward to no more codes...Thanks guys. Just finished installing the new Hill flanges, along with new Hill V-clamps, and everything looks great. If i can find a little more time, will smoke test again. May have to wait until tomorrow morning. Feeling strong......LOL
Any leak what so ever in the exhaust system will continue to give emmision related codes. Correct Ian Never go back to that exhaust shop. In my opinion if that was work carried out on my car the leaks would be fixed at there expense(installer of leaking system)
Use a high quality high temp sealer. I used muffler putty when re installing any exhaust flange/donut/slip fit joints. Just a light smear. It takes up any inconsistencies in the joints. Also always only use sensor friendly sealants or you will be replacing all the exhaust sensor's again. Ask me how I know?
Fabspeed bypass and Nouvalari Sport muffler was installed 07/2018 by PO. I don't comprehend the incorrect flange? The ID and OD match the pipe and match muffler; both Fabspeed and Nouvalari say to use OEM hardware and do not sell any. Thinking they might be for another Ferrari? Image Unavailable, Please Login
That's why this Forum is so helpful. People have all experienced these issues long before we have. You just have to read the context. The information is all there mate. Good luck. It's nice to eliminate a demon you can't find.
O2 sensors only start working when they are hit that’s why they have heating elements the pre O2 sensors control your fuel trims and post O2 Monitor the The efficiency of the emissions going through the cats if you have a scanner the pre O2 sensors both banks should be switching going over and under 450 mv (from 150mv LEAN to 725mv RICH) depending on idle or driving modes the post O2 both banks of the cats are in and working should stay around 450mv with little changes from 325mv to 525mv under most idle and driving conditions If the ecm see’s the post O2 switching at a rate higher (moving above and below 450mv) then it’s programmed for that’s when the codes are set have longer, bent and adding steel wool just allows the exhaust gas to stabilize before reaching the post O2 sensors Sent from my iPhone using FerrariChat.com mobile app