Why is a tune required with header/hi-flow cat installation?

[Higgs Boson]

Originally Posted by strych9

You nailed what I was thinking perfectly. The CEL needs to remain functional for the warning of other faults, IMO. As for the performance, that's what I reasoned to be the result of of an untuned alteration.

The check engine light that results from cat removal is generated by the rear O2 sensors and does nothing but tell you if the cat is there (and/or properly working). It does not do anything to adjust fuel trims, etc, those are the front O2 sensors, which are left alone. If the factory cat is indeed gone, why does the CEL light functionality (for that code) need to remain intact (unless you need additional reading light while driving)?

[2SS45th]

Originally Posted by Higgs Boson

I gotta ask, ever been in the car business? Do you know ANY of the real numbers behind markup, warranty costs, goodwill costs, etc? Just curious, because if you do and that is really your opinion, I guess that's valid, but if you are just saying that and you are an artist or something, then, come on, don't say what you don't know for sure.

My entire family has been in the car business man, my dad taught me, his dad taught him. I buy all of my parts at dealer cost, and I fully understand the way that the dealer makes money on service. Probably a near century in the business, I know how it all works.

[Higgs Boson]

Originally Posted by 2SS45th

My entire family has been in the car business man, my dad taught me, his dad taught him. I buy all of my parts at dealer cost, and I fully understand the way that the dealer makes money on service. Probably a near century in the business, I know how it all works.

Then I guess I don't understand where the profits comment comes from.

My father has 20 dealerships, my uncle has one, another uncle has a ridiculously busy repair shop in town, etc. I have worked in dealerships, run dealerships, worked for the factory, etc.

When you say there is so much money in profits, what are you basing that on? It varies widely depending on make, model, dealer, etc. And whatever the dealer makes on a car has nothing to do with what the factory makes on a car (when it sells it to the dealer).

What the factory makes is an unknown. No one knows, and the factory is paying for the warranty, so I am trying to figure out your correlation between the dealer profits and the factory warranty expense....

Car manufacturers spend literally billions a year on warranty work. It is so justified to check what you are doing.

[K32 Camaro]

AND my grandson owns every dealership on the east coast, gm, chrystler, and ford. Funny that I'm only in my 20's too! Stop the thread jack, Move your arguments to pm's.

FACT is OP, you do not 'need' a tune with headers or hi flow cats of any kind. You get a little more gain with a tune but there are many people that run them and just let the CEL sit on the dash. Most people do get a tune b/c advised to by a shop or paranoid people on here but I have never even heard of a single case where it caused a problem.

[2SS45th]

Manufacturers make profit no matter what. But the thread jack should end here. The op wanted to know if he has to have a tune. You don't have to have one, I don't and it's all fine. You can turn the light off, so you know when something else goes wrong. Go for it, and enjoy your headers!

[Higgs Boson]

Originally Posted by K32 Camaro

AND my grandson owns every dealership on the east coast, gm, chrystler, and ford. Funny that I'm only in my 20's too! Stop the thread jack, Move your arguments to pm's.

FACT is OP, you do not 'need' a tune with headers or hi flow cats of any kind. You get a little more gain with a tune but there are many people that run them and just let the CEL sit on the dash. Most people do get a tune b/c advised to by a shop or paranoid people on here but I have never even heard of a single case where it caused a problem.

The thread is dead, op was answered in the first few posts. It's a thread jack because you want to get your two cents in as well? Please. Conversations are dynamic, I am sure you can adapt.

My conversation with 2SS45th has nothing to do with you or your grandson.

[Cincy10SSRS]

Originally Posted by bucketobolts

High flow cats cause CEL because they are not working as GM designed. So why waste the money.

Good hi-flow cats by them selves (not replacing the stock exhaust manifolds) do not cause CEL's and provide up to a 22 hp gain. Sound great too. I've had them on for a while now and love 'em.

http://solo-performance.com/pe-camaro-ls3-std

[EliteCZM523]

To the OP:

Do you "NEED" a tune? No. If you buy the LT's and get High Flow Cats with them would you benefit from a tune? Yes. Same goes for any other "bolt-on" mod. You can put it on, and it should be ok - but you will reap the most benefit from a tune that modifies the vehicle to correctly adjust fuel/spark to the mods on it.

As far as warranty - its a simple misconception that a tune will Void your entire warranty. First off the vehicle would have to come in to the dealership with a drive-ability concern for them to check if you even have a tune.

Secondly - in terms of profit... You honestly think that there is such a large profit margin built into everything? Seriously? You do realize that 90% of goodwill or discounted services/repairs come out of the pockets of the service writers right? You do know that warranty work pays the technician about 1/4 the time that customer pay does right? Keep in mind 99% of dealerships out there pay technicians on a flat rate basis. Job pays 1.0 hrs - tech does it in .5 - he still gets paid for 1.0

Warranty work sucks - period. Dealership won't make a dime on the parts, nor the labor - they get re-imbursed for the cost of the repair - thats it!

If Automobile repair is so profitable - then why doesn't everyone own a repair shop and drive lambos?

Exactly my point.

[justa25thTA]

Originally Posted by Higgs Boson

The check engine light that results from cat removal is generated by the rear O2 sensors and does nothing but tell you if the cat is there (and/or properly working). It does not do anything to adjust fuel trims, etc, those are the front O2 sensors, which are left alone. If the factory cat is indeed gone, why does the CEL light functionality (for that code) need to remain intact (unless you need additional reading light while driving)?

Is this the only reason for the CEL to come on (the rear O2's)? I ASSume that there are other codes that will trigger it and would prefer to see those codes to take care of any issues. I also ASSume that the fuel trims are just fine, since no codes are being thrown. I am talking about my set up, which is the JBA high flow cats. Not those running off road pipes and no cats.

[strych9]

Thanks for the input, guys. Good stuff.

[Higgs Boson]

Originally Posted by justa25thTA

Is this the only reason for the CEL to come on (the rear O2's)? I ASSume that there are other codes that will trigger it and would prefer to see those codes to take care of any issues. I also ASSume that the fuel trims are just fine, since no codes are being thrown. I am talking about my set up, which is the JBA high flow cats. Not those running off road pipes and no cats.

1) CEL's that result from the rear O2 sensors are strictly due to:
a. lack of cat
b. factory cat performing poorly
c. aftermarket cat not cleaning up the exhaust as good as the factory cat
The front O2 sensors are the ones that monitor engine performance and contribute to fuel trims etc. A tune can disable specific codes, ie. those related only to Sensor 2, which means rear sensor (behind the cats). If the tuner only disables the sensor 2 codes in the tune, no other codes need to be affected. You can highly correlate Sensor 2 and Catalytic Converter just as you can separately highly correlate Sensor 1 and Engine.

2) Fuel trims are adjusted based on feedback from your front O2 sensors (Sensor 1). BTW, Sensor 1 and 2 are on both sides, Bank 1 and Bank 2 (Bank 1 being driver side). Your fuel trims will be less than ideal without a tune but most likely not outside the range of adjustability. Typically that range is +/- 25% from the baseline. Tuning adjusts the baseline and lowers trim percentages, which has various benefits that I won't go into detail on here. If you are constantly pushing the 25% limit then you can get lean codes that typically generate based on Sensor 1 feedback. If you install long tube headers the O2 sensors are mounted farther away from the engine which many times does not allow them to heat properly (and therefore function properly) and they may throw switching error codes, otherwise verbalized as Slow to Respond codes. Many people will just toss in replacement sensors but this only alleviates the issue in the short term. The sensors are not bad, the closed loop tables in the tune need to be adjusted to show the sensors how to switch again to stay within their expected usable range. Of course, you can just turn those codes off too, but that's a bandaid (and a lot easier than doing it right).

With that said, trims are only active at part throttle, not at wide open throttle. If the trims are correcting the baseline by adding fuel (let's say 20%) then the computer thinks you are 20% lean. What this means is that instead of being at a 12.7 a/f ratio at full throttle, you will be dangerously lean. The thing is though, a stock tune is programmed to be pig rich at full throttle, leaving LOTS of power on the table, lots of throttle response, etc. This also means that if you add airflow and lean out the stock tune, you may be leaner, but not dangerously lean. As you add more parts, you add more airflow, and without measuring and adjusting (tuning), you will never know where you are, if it is safe, if there is more power on the table, etc. You are blind.

That's why I always say, "get a tune." Yeah, you don't have to and that makes the cost of entry to Modification Land much lower, but it's not something I agree with. My opinion only, but factor in the cost of tune to your first mod, whether intake or headers or whatever, and find a tuner that will tweak your tune for free or minimal cost as you add parts. Plan your mods, do them in bulk, don't redo them because you changed your mind or your plan (it happens though). Personally, I just feel a tune is an essential and integral part of the modding process.

[2SS45th]

I can agree with higgs about modding being integral. I think that a tune is very important when modding any car. I plan on tuning when I do my supercharger. However, a dyno tune costs about $400 roughly. So, when you can wait to tune until you have a part that it becomes essential, do so. Save your money, and don't tune for every little thing. Do it when NECESSARY, not for a 15hp gain.

[strych9]

Originally Posted by Higgs Boson

1) CEL's that result from the rear O2 sensors are strictly due to:
a. lack of cat
b. factory cat performing poorly
c. aftermarket cat not cleaning up the exhaust as good as the factory cat
The front O2 sensors are the ones that monitor engine performance and contribute to fuel trims etc. A tune can disable specific codes, ie. those related only to Sensor 2, which means rear sensor (behind the cats). If the tuner only disables the sensor 2 codes in the tune, no other codes need to be affected. You can highly correlate Sensor 2 and Catalytic Converter just as you can separately highly correlate Sensor 1 and Engine.

2) Fuel trims are adjusted based on feedback from your front O2 sensors (Sensor 1). BTW, Sensor 1 and 2 are on both sides, Bank 1 and Bank 2 (Bank 1 being driver side). Your fuel trims will be less than ideal without a tune but most likely not outside the range of adjustability. Typically that range is +/- 25% from the baseline. Tuning adjusts the baseline and lowers trim percentages, which has various benefits that I won't go into detail on here. If you are constantly pushing the 25% limit then you can get lean codes that typically generate based on Sensor 1 feedback. If you install long tube headers the O2 sensors are mounted farther away from the engine which many times does not allow them to heat properly (and therefore function properly) and they may throw switching error codes, otherwise verbalized as Slow to Respond codes. Many people will just toss in replacement sensors but this only alleviates the issue in the short term. The sensors are not bad, the closed loop tables in the tune need to be adjusted to show the sensors how to switch again to stay within their expected usable range. Of course, you can just turn those codes off too, but that's a bandaid (and a lot easier than doing it right).

With that said, trims are only active at part throttle, not at wide open throttle. If the trims are correcting the baseline by adding fuel (let's say 20%) then the computer thinks you are 20% lean. What this means is that instead of being at a 12.7 a/f ratio at full throttle, you will be dangerously lean. The thing is though, a stock tune is programmed to be pig rich at full throttle, leaving LOTS of power on the table, lots of throttle response, etc. This also means that if you add airflow and lean out the stock tune, you may be leaner, but not dangerously lean. As you add more parts, you add more airflow, and without measuring and adjusting (tuning), you will never know where you are, if it is safe, if there is more power on the table, etc. You are blind.

That's why I always say, "get a tune." Yeah, you don't have to and that makes the cost of entry to Modification Land much lower, but it's not something I agree with. My opinion only, but factor in the cost of tune to your first mod, whether intake or headers or whatever, and find a tuner that will tweak your tune for free or minimal cost as you add parts. Plan your mods, do them in bulk, don't redo them because you changed your mind or your plan (it happens though). Personally, I just feel a tune is an essential and integral part of the modding process.

I agree with all that you've said in this post. I even agree that a tune is essential if you want to extract the maximum available power from your mods. The cost of the tune is irrelevant. If I can drop $1500 + on headers and cats, I can drop another $500 for the tune. Point is, I am not willing to devalue my Camaro's worth by programming the ECM. If I were to trade or sell it within the powertrain warranty period, I want the value-add that the warranty provides. That is the ONLY reason that I'm anti-tune.

The other point being, I could cam, heads, headers, intake, CAI, exhaust, NOS, all day long with the Mustangs with no tune and no CEL and run high 11's all day long. So, I wanted to know why that couldn't be so with the Camaro. Thanks again.

[lynxone]

Originally Posted by Higgs Boson

1) CEL's that result from the rear O2 sensors are strictly due to:
a. lack of cat
b. factory cat performing poorly
c. aftermarket cat not cleaning up the exhaust as good as the factory cat
The front O2 sensors are the ones that monitor engine performance and contribute to fuel trims etc. A tune can disable specific codes, ie. those related only to Sensor 2, which means rear sensor (behind the cats). If the tuner only disables the sensor 2 codes in the tune, no other codes need to be affected. You can highly correlate Sensor 2 and Catalytic Converter just as you can separately highly correlate Sensor 1 and Engine.

2) Fuel trims are adjusted based on feedback from your front O2 sensors (Sensor 1). BTW, Sensor 1 and 2 are on both sides, Bank 1 and Bank 2 (Bank 1 being driver side). Your fuel trims will be less than ideal without a tune but most likely not outside the range of adjustability. Typically that range is +/- 25% from the baseline. Tuning adjusts the baseline and lowers trim percentages, which has various benefits that I won't go into detail on here. If you are constantly pushing the 25% limit then you can get lean codes that typically generate based on Sensor 1 feedback. If you install long tube headers the O2 sensors are mounted farther away from the engine which many times does not allow them to heat properly (and therefore function properly) and they may throw switching error codes, otherwise verbalized as Slow to Respond codes. Many people will just toss in replacement sensors but this only alleviates the issue in the short term. The sensors are not bad, the closed loop tables in the tune need to be adjusted to show the sensors how to switch again to stay within their expected usable range. Of course, you can just turn those codes off too, but that's a bandaid (and a lot easier than doing it right).

With that said, trims are only active at part throttle, not at wide open throttle. If the trims are correcting the baseline by adding fuel (let's say 20%) then the computer thinks you are 20% lean. What this means is that instead of being at a 12.7 a/f ratio at full throttle, you will be dangerously lean. The thing is though, a stock tune is programmed to be pig rich at full throttle, leaving LOTS of power on the table, lots of throttle response, etc. This also means that if you add airflow and lean out the stock tune, you may be leaner, but not dangerously lean. As you add more parts, you add more airflow, and without measuring and adjusting (tuning), you will never know where you are, if it is safe, if there is more power on the table, etc. You are blind.

That's why I always say, "get a tune." Yeah, you don't have to and that makes the cost of entry to Modification Land much lower, but it's not something I agree with. My opinion only, but factor in the cost of tune to your first mod, whether intake or headers or whatever, and find a tuner that will tweak your tune for free or minimal cost as you add parts. Plan your mods, do them in bulk, don't redo them because you changed your mind or your plan (it happens though). Personally, I just feel a tune is an essential and integral part of the modding process.

That was a great read!