LT1 Z51

FYI - Super similar thread over on an M3 forum. http://www.m3post.com/forums/showthread.php?t=653585

I agree with the one guy there (clearly), if it's not a part of the emission control system feedback look (ergo it has to have a sensor). It's not part of emissions.

Further to me, if it's not part of emissions, it's not a cat. Sure it may have the same material as a cat, but a cat is something which has an O2 sensor in front of it, and another one behind it.

LT1 Z51

Here's another thread from a BMW Forum (lots of BMW's seem to have these things).

http://www.1addicts.com/forums/showthread.php?t=942556

Again same thing, same argument, and I think same result. If it's not turning on a MIL, it's not an emissions control device, and then it's not a catalytic converter.

That thread states it might be for SULEV certification. I don't think we have that on Corvette, but it's nonetheless an interesting theory.

Even after reading maybe 10 other threads on other websites, I stand by my statement. It's not a cat.

Internets_Ninja

The only part I was wrong(technically an error) about was the secondary cats being monitored but no CEL being thrown. This was actually on another car I was tuning where the logic was different and the rear O2's did monitor the secondary cat(Subaru) . I actually came back to make a correction but you beat me to it. Nothing else about my post was wrong and I certainly have a great knowledge of how the ECU's work and how to tune them. I've tuned cars on multiple platforms and have been doing this for many years. Albeit I've never gone pro as I have no interest. I first started tuning in the days of LT1 Edit when it was the only way to tune GM cars. Then EFI came out with a solution but was far more expensive. Then along came HPTuners with the LS1's and this caused LT1 and LS1 edit to pretty much die as HP Tuners was a superior product.

Good news is that this was my only error in all of my posts on here. I have a documented track record of correct information. But anyhow, good day, try not to be so angry on the internets. .

P.S. The secondary cats are indeed still cats.

bigsapper

There were emission control devices, including catalytic converters, on cars well before the advent of ECUs. Not sure I understand the point of an emission control device having to be monitored by an ECU to be considered part of the "system".

Also, my understanding is that the secondary cats help deal with cold start/run emissions which I believe .gov added to the requirements some years back.

LT1 Z51

In those days they used closed loop mechanical controls (EGR valve for one). ECUs on engines are actually super old. Early 1980's, if not older.

Regardless a closed loop system needs to be used to monitor something. Because it requires a sensor. Technically you could still have a feed forward design with the sensor, but you'd never do that because once you have a sensor you can do feedback control (closed loop).

https://en.wikipedia.org/wiki/Contro...dback)_control

Maybe early emissions systems used only design controls, like a feed forward design. This could be why they were terrible. Or even optional for a time.

If the things after the O2 sensor are feed forward emissions controls then the only way you can ever find out if they have an issue is with a sniff test. Since the ECU isn't aware of them. If they are legally required, you'd expect the sniff test to also be legally required (this was a valid argument in one of those BMW threads).

To me catalytic converter is a loaded word. As is emissions control. A feed forward device doesn't fall into the current definitions of those words (see lack of snifter test thought process). If it did, then you can bet that the sniffer test would be mandatory as there is no way to prove that the device was removed otherwise.

I think a lawyer of any reasonable skill could argue that these things are not emissions control devices, do not partake in the emissions control system, and that regardless of construction should not be referred to as catalytic converters.

That's my engineering opinion. You can like it or lump it, but I don't see a flaw in it as of now.

bigsapper

Sorry, can't help you there. I think you're "tilting at windmills".

LT1 Z51

When you say catalytic converter immediately think, pipe with O2 sensor, then a catalyst then more pipe with an O2 sensor. For emissions control, the above and EGR systems are what I think of.

I'd tell you from a layman's term that's the general consensus in what those words mean.

Why do you think people ask what the devices are past the second O2 sensor? It's because they don't think they have anything to do with emissions.

Words have general meanings. You have to use them in ways people understand. Based on that, EVERYTHING is "tilting at windmills"

KGrant

I learned a new phrase LOL

"Tilting at windmills" is an English idiom that means attacking imaginary enemies. The expression is derived from the novel Don Quixote by Miguel de Cervantes, and the word "tilt" in this context comes from jousting.

The phrase is sometimes used to describe either confrontations where adversaries are incorrectly perceived, or courses of action that are based on misinterpreted or misapplied heroic, romantic, or idealistic justifications. It may also connote an importune, unfounded, and vain effort against adversaries real or imagined for a vain goal

bigsapper

You might as well call them muffler bearings then.

JerryU

Liked my old bosses comment better, means about the same. He was a brilliant physicist that was in the Navy in WWII so when he said this is was usually with a few expletive deletives because he saw someone doing something foolish! He would say with distain, "Your solving a Problem not know to exist using a Method known not to work!"


He invented Plasma welding and cutting but could be a PIA for some of my folks when he visited our Lab. Fortunately we were in NE Ohio along Lake Eire so he seldom came in the Winter! The other Labs he managed were in SC, IN and NJ. Less snow!

Internets_Ninja

We should introduce this to Ask Tadge

Bill Dearborn

I seem to remember that when cats were introduced in 1975 there were no feedback mechanisms in place. Those cars definitely didn't have any sort of engine computer since the technology wasn't available to make a computer small enough or durable enough. I looked but can't verify whether or not any of those cars had an O2 sensor but I am fairly sure they didn't, but that occurred 43 years ago so I could have an erroneous memory.

I doubt it really matters whether there is an O2 sensor or not for something to be part of the emissions controls as those first cats were considered part of the emissions systems. If there is a cat in the exhaust system it is there to satisfy some sort of emissions requirement and the manufacturers wouldn't put it in if it wasn't required. It is well known they don't put parts in a vehicle if the parts aren't required. Cats are relatively expensive compared to a lot of parts in an automobile and they wouldn't put a low cost thermostat in the cooling system if it wasn't required to make the engine run properly.

It doesn't matter what an experienced or inexperienced tuner thinks about whether or not a device is emissions related or not. It only matters what the manufacturer and the government consider to be emissions devices. Saying you have X and Y amount of experience tuning cars and that makes you an expert on whether a device is an emissions device is what we were taught in school as an example of misplaced authority (http://www.softschools.com/examples/..._examples/430/). As my mother used to say about my excuses when caught doing something I shouldn't be doing: "What has that got to do with the price of Tea in China?"

Bill

bigsapper

I can tell you for a fact they weren't. I was an NIASE mechanic at Tom Peacock Chevrolet in Houston from 1977-1981.

C7/Z06 Man

Way back when & up to recent they measured your emissions through the tail pipe with a sensor. If it did not meet the requirement you had a problem. Remember the 'Guarantee to Pass' stuff?

timmyZ06

so basically, you choose between losing low end or sounds! There is no way around it, unless 2015 Z are less knock sensors sensitive!

Internets_Ninja

A slight timing adjustment and changing to the knock sensors will correct the loss. But if anyone is unwilling to tune their car they should stick to axle back exhaust only.

It literally is not worth even modding the car at all unless you're going to tune it.

6Speeder

Gotta disagree with you on this statement. I ran the Halltech CAI, the IW 9% overdrive pulley for the supercharger, and gutted the rear cats WITHOUT CHANGING THE FACTORY TUNE. I run a wideband and monitor the motor constantly. Yes, in cruise (closed loop) it runs slightly leaner (up to +5 LTFT's) with no KR. In WOT it still goes pig rich when COT kicks in. No problem or loss of low end torque. No timing changes or adjustments to the knock sensors.

Internets_Ninja

Sorry, I was speaking about LT1's specifically, not Z06's. I think it was earlier in this thread where I said intakes on Z06's was the exception to my "leave it stock if you wont tune it". However, I still think you should be tuned for those mods. How are you confirming you are running pig rich? You do know that COT doesn't always kick in right? Have you monitored knock? I'm mostly curious, not trying to accuse you of being wrong.

6Speeder

It's cool. I have a wide band 02 running continuously, and monitor LTFT's. Every so often I run a scan with HPTuners software and see the same occasional burst of KR, just like I did when stock.

Internets_Ninja

Is your Wideband pre or post cat? Only asking as I have heard some install post cat and "fudge" the Lambada a bit to compensate. Again, I only ask because I'm debating on installing post cat in the existing bung or if I should have an additional bung installed pre cat(which is more of a PITA). I've never installed one post cat before so I don't know how it would behave.

thanks