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

[Higgs Boson]

Originally Posted by strych9

This thread has generated some interesting responses. For the record, I am interested in both sound and performance, but the scope of my inquiry focused on the sound benefits, and possible performance detriments if no tune was performed. I already have a cat back Flowmaster AT system. Sounds good, just not as good as my catless, MAC x-piped Mustang did with the same system.

Great points and input by all, including the spirited debate.

To be fair, NOTHING sounds as good as a mustang with exhaust. I mean this side of a mid mounted V12....

[ramsman34]

This thread has generated some interesting responses. For the record, I am interested in both sound and performance, but the scope of my inquiry focused on the sound benefits, and possible performance detriments if no tune was performed. I already have a cat back Flowmaster AT system. Sounds good, just not as good as my catless, MAC x-piped Mustang did with the same system.

Now my response is probably worthless as I haven't done a video of the sound of my intake/exhaust system yet.

I have the AT cat back like you matched to a CAI intake and Doug Thorley shorty headers. My car went from a whispering camaro to a very nice retro sounding musclecar. I don't want a Euro sound.

Now, I didn't dyno before or after. I don't have a tune, and I did all thees air flow mods at once. My cars tone is awesome at start up/idle, no real drone for the most part and at WOT is scares people. That being said, it has been argued by pros and amateurs alike that shorties do nothing or add up to 10 WHP.

I would like my car to sound a bit more badass without drone and I want more power Captain! I am debating either keeping everything except replacing stock cats with hi flows adding a racing scoop and getting a tune VS getting long tubes, hi flow cats,the racing scop op and a tune. My tuner syas the LT's are absolutely the way to go and will offer real gains with a tune compared to the shorties. My dilemma is $$$.

I will try to post a vid of my exhaust so you can decide wether yout AT's are enough or if shorties my be the way to go. The CAI help a lot as well.

[ramsman34]

.....Main point being, either keeping the shorties or swapping for long tubes I am getting a tune to get the most out of the mods.

[ParisTNDude]

Geesh, an awful lot of technical stuff posted here, but the simple fact is your car will most likely throw a code if you don't tune it and the performance is improved dramatically with a tune. I drove mine for a week or more with just the headers and HF cats added (mine did not light up a code) and you could clearly notice the improved performance gains, oh and the sound was awesome, but when I had it tuned, it simply woke the car up. Before the tune, running 12.68s at 109/110 afer the tune 12.49s at 111/112. Tune it for the full value of your $1500 upgrade.

[greenmachinedriver]

Originally Posted by Higgs Boson

I agree with all u said here.

I worked out of the Dallas regional office lol. don't tell me which dealer that had u do this, not that I care now.

well ill tell you it wasnt crest or Sewell. That kinda stuff went on alot there due to a greedy service manager. Im glad I moved on, I work for Lexus now.

[Higgs Boson]

Originally Posted by greenmachinedriver

well ill tell you it wasnt crest or Sewell. That kinda stuff went on alot there due to a greedy service manager. Im glad I moved on, I work for Lexus now.

very cool. Lexus dealers are top notch man. and I mean that. top. notch.

[strych9]

Originally Posted by ramsman34

Now my response is probably worthless as I haven't done a video of the sound of my intake/exhaust system yet.

I have the AT cat back like you matched to a CAI intake and Doug Thorley shorty headers. My car went from a whispering camaro to a very nice retro sounding musclecar. I don't want a Euro sound.

Now, I didn't dyno before or after. I don't have a tune, and I did all thees air flow mods at once. My cars tone is awesome at start up/idle, no real drone for the most part and at WOT is scares people. That being said, it has been argued by pros and amateurs alike that shorties do nothing or add up to 10 WHP.

I would like my car to sound a bit more badass without drone and I want more power Captain! I am debating either keeping everything except replacing stock cats with hi flows adding a racing scoop and getting a tune VS getting long tubes, hi flow cats,the racing scop op and a tune. My tuner syas the LT's are absolutely the way to go and will offer real gains with a tune compared to the shorties. My dilemma is $$$.

I will try to post a vid of my exhaust so you can decide wether yout AT's are enough or if shorties my be the way to go. The CAI help a lot as well.

I would be interested to hear your set up. Thanks!

[Blk-Ice]

Originally Posted by greenmachinedriver

Wow this thread is close to fail status.
op, I have been running high flow cats and long tubes over a year no tune. I have spacers in the rear o2 sensors to fool the ecu into thinking the cats are working. My cel comes on once every few months for a front o2 slow response due to slightly off mixture. I will and always planed to tune but am waiting on more mods first.
Higgs, you would have cringed when my service manager told me to warranty a long block for a client with a g35 with a supercharger that melted pistons. NNA should not havr to shell out 10k for somthing that the cient caused. But it just goes to show you warranty all depends on who your dealing with. Not to many clear cut answers.

So what do you do when your cel comes on, just delete it? Is there a negative side to deleting a code too many times?

[Higgs Boson]

Only to your psyche.

[Nessal]

Originally Posted by bucketobolts

You are really showing your brilliance, just as in other threads.

The 02 is passive and just reports. It does not know where it is nor does positioning effect its readings.

It is the converters that are not working...plain and simple, and the 02 tells the PCM to turn on the light.



I can also hijack if you would like to debate Constitutional Law. I bought and paid for my vehicle therefore it is my personal property. No one, especially you who has been contracted to work on my vehicle, has no right to rifle though my vehicle. I don't care who your daddy is or what he has bought you.

I don't believe it's a search if it's left out right in the open for anyone to see.

[Blk-Ice]

Originally Posted by Higgs Boson

Only to your psyche.

LMAO.....sarcasm, gotta love it!

[Blk-Ice]

Can the change of altitude and the temperature cause an 02 sensor alarm if let's my car was tuned in TX and then I bring it to NC which is a lower altitude and less dry heat?! I'm asking because a tuner told me this and it sounds kinda far fetched to me.

[Higgs Boson]

Originally Posted by Blk-Ice

Can the change of altitude and the temperature cause an 02 sensor alarm if let's my car was tuned in TX and then I bring it to NC which is a lower altitude and less dry heat?! I'm asking because a tuner told me this and it sounds kinda far fetched to me.

Not unless the tune was really far off to begin with and even then, it would not be an O2 sensor code. maybe a fuel trims outta wack code. If your tune was correct then a change in altitude and temperature should not set any codes. It should be just like a stock vehicle.

[Blk-Ice]

I think it's my HF Cats and LT Headers that's causing my issue. Seems like it's to be expected with those mods based on what everyone on here seems to think.