Just a recap I put my truck on a dynamometer with exhaust gas analyzing to run some tests of before and after with exhaust and intake modifications. The Exhaust gas analyzer used was a wide ban 02 sensor type that measured the oxygen content in the exhaust stream and a computer calculated the air fuel ratio based on this information. I started a thread called
Reason why the I-force v8 doesn’t respond very well to engine modifications. stating that the i-force V8 doesn’t respond to engine modifications because the air fuel ratio will go rich when you modify it. Some TS members argued that this was due to the fact that the catalytic converters skew the readings after the cats and give a wide band 02 sensor type exhaust gas analyzer false readings. I then argued that other vehicles there had similar emissions equipment and that if that were so than they too would show similar results on the exhaust gas analyzer.
I eventually talked the dyno owner operator (Dean) via e-mail and provided him with information I was getting from TS and he eventually talked to the dynojet manufacturer about this situation. Again I explained to them about how the catalytic converters could effect the after cat emissions when using a wide band 02 sensor and also explained to them about what I learned from TS members in this thread.
Dean wrote,
John,
I will have to forward this to Dynojet to see what they say. We have dynoed 100's of domestic and foreign cars including numerous with OBD2 as well as ULEV vehicles and have never had an issue. But in this day and age anything is possible with a particular model.
We have tested many cars by sampling with the wideband at the header and at the exhaust and readings are typically identical unless there is a hole somewhere in the exhaust system.
The majority of the top aftermarket tuners in the US all use the wideband O2 with no issues - I would not be able to justify a gas analyzer for only the Tundra as we have never had issues with any other Toyota model or any other model for that matter.
I will let you know how they respond as I dont have an answer for you.
Thanks,
Dean
www.nedyno.com
When I asked Dean if it is typical for him to see black smoke coming form the exhaust this was his response.
John,
Sorry for the delay getting back to you. If its running rich, and you have a good cat and mufflers you usually wont see a big black cloud. The wideband only goes to 10:1 on the low end.
Hope this helps!
Dean
www.nedyno.com
I just received a response from Dean stating this,
Here is the response I received from Dynojet:
Dean,
From all of the testing we (and many of our customers) have performed, measuring pre and post cat yield the same air/fuel ratio measurements. I believe the best answer for this is that while performing a typical roll-on on the dynamometer, the converters are overwhelmed to a large degree and cannot do their job. Converters work well under light load and especially at idle and I believe that is where emissions are focusing.
I really don’t have any real tangible scientific data or graphs for you but I hope this helps. I would recommend trying it yourself pre and post cat and see for your self. We had one customer who was adamant about it and we told him to perform his own testing and sure enough he called back and said there was no difference other than a slight delay in response from testing at the tailpipe versus the exhaust bung.
Let me know if you have any other questions.
I would like to get some more commentary from any TS members who are knowledgeable on this subject. In my opinion I think the only way to back up the validity of the results from the wide band 02 sensor readings is to compare them with the results from an exhaust gas analyzer that reads carbon monoxide, Oxygen, hydrocarbons, and carbon dioxide.
If the engine was actually running rich the carbon dioxide would go sky high and even the most efficient catalytic converters wouldn’t help unless there were an air pump to add additional oxygen to the catalytic converters and there isn’t an air pump on the Tundra. If there isn’t enough oxygen (02) present for the hydrocarbons (HC) to have complete combustion than instead of one carbon atom combing with two oxygen atoms and getting carbon dioxide (CO2) you get only one oxygen atom combining with one carbon atom and you get carbon monoxide (CO or CO1). We won’t worry about N02 emissions OK although they would indicate a high combustion temperature and an overly rich mixture would cool the combustion chambers.
Sampling in front of the catalytic converters could and would be a viable test but I would have to modify the exhaust by welding a bung in it and fitting it with an expensive wide band 02 sensor. If I remove the existing 02 sensors I would be removing the sensors that the computer relies on for reading the exhaust gas oxygen content and I’m afraid I would ruin something or skew the results of the tests. I could just put a DVM on the existing 02 sensor but it would only read the maximum voltage of .9 volts letting me know that the exhaust is rich but not by how much. When a rich exhaust goes beyond the range of the 02 sensor (and it will) than the maximum reading from the 02 sensor will read the same .9 volts regardless of how rich the air fuel mixture is.
I just need to find someone who has a machine like this that I could use for a reasonable price. I would like to be proven wrong with some kind of test as I have mensioned above. I don’t want to just assume anything!