Mods and Tune

[GodWentPunk]

In March of 2019 I'll looking to get some long-tube headers, high-flow cats, and some type of cat back exhaust (with x-pipe) for my 2015 SS (L99). I'm rather new to the "tune" concept so I was hoping that maybe someone could explain a little more why I need a tune and what it will accomplish. I do know that I'll be disabling my AFM but other then that, I sorta left hanging. I will be getting a professional tune but I just like to know beforehand what I should be expecting.


thanks!


joe...

[acammer]

Originally Posted by GodWentPunk

In March of 2019 I'll looking to get some long-tube headers, high-flow cats, and some type of cat back exhaust (with x-pipe) for my 2015 SS (L99). I'm rather new to the "tune" concept so I was hoping that maybe someone could explain a little more why I need a tune and what it will accomplish. I do know that I'll be disabling my AFM but other then that, I sorta left hanging. I will be getting a professional tune but I just like to know beforehand what I should be expecting.


thanks!


joe...

Joe - your engine is basically a big air pump, and when you change the way that the air flows through it (such as with an exhaust like you've described) it will impact the calibration. In simple terms, the amount of fuel required by the engine changes with the changes in airflow, and the tune will adjust for those changes.

A good tune will also make some other important changes, improve spark timing (depending on fuel octane you specify) and knock sensitivity, throttle response, remove AFM (if desired), transmission performance (shift firmness, shift RPM, shift schedule, torque converter lockup, etc), disable rear O2 sensor errors, top speed and RPM limits, etc. There are many things that can be changed and effected by the tune. Really, it needs a holistic approach as many of these things impact one another. A good tuner should be discussing what you want out of the car and calibrating it to achieve that.

[qcman]

Joe my L99 is all stock except for the tune on the engine and trans. Its a beast compared to stock now that chirps the first 3 gears with relative ease. Add your mods on top of that & you will be happy no doubt. Other than that acammer nailed it!

[christianchevell]

Yup torque management in a l99 car is a power killer to protect the trans. And most do the 160 degree thermostat at the same time and change the start for the fans temp. A couple nice things in advance for later mods. Just a couple thoughts....

[gapmoneyvision1]

I ordered some aftermarket headlights off eBay. Went and got them put on at my local shop I always deal with. The fog lights came with a faulty on/off switch button where the back light stays green even when the lights are not on (only when the car is running tho). The fog lights turn on and off tho. Could the faulty switch be a slow drain on my battery tho?

[silversleeper]

Originally Posted by gapmoneyvision1

I ordered some aftermarket headlights off eBay. Went and got them put on at my local shop I always deal with. The fog lights came with a faulty on/off switch button where the back light stays green even when the lights are not on (only when the car is running tho). The fog lights turn on and off tho. Could the faulty switch be a slow drain on my battery tho?

My limited experience with battery drain is to look at aftermarket things put on the car as the first thing to suspect. So yes. Unplug it and see if that stops the drain. One LED wouldn't be much drain but it could be mis-wired or shorted etc too.
Edit: That goes for non-oem car alarms and powered subwoofers etc too.

[pyroguy]

I have a cold air intake, ported throttle body, long tube headers w/ cats, and a catback exhaust. After getting headers is when I tuned the car for a few reasons:
- When you install long tube headers you will get a CEL. Some people it happens immediately, others it takes a while, but eventually you will have a CEL.
- The air fuel ratio is off when you allow your engine to breathe in and out easier. If your ratio is off too badly it can eventually damage the engine. Don't worry, you can drive the car to get tuned and around for a little while if you want. I just wouldn't recommend too many wide open throttle pulls until it's tuned.
- A L99 car is a COMPLETELY different animal with a tune. With a stock tune the cars are fastish but a little lazy. With a proper tune including tuning the transmission the cars REALLY wake up and become a heck and a half of fun. I had my tuner tune a "wife mode" for D and a more aggressive tune for M. When I'm in drive mode it shifts similar to stock with a little added firmness over stock, but not unbearable and with better shift points, but M mode has neck snapping shifts and really propels the car.

Funny enough, unlike most people who tune their cars, I still have AFM enabled. My exhaust setup is such that it doesn't sound awful when engaged and the car doesn't drone so I really don't mind the extra 1-2 mpg fuel efficiency. When I cam the car AFM is gone though.

[GodWentPunk]

Originally Posted by pyroguy

I had my tuner tune a "wife mode" for D and a more aggressive tune for M. When I'm in drive mode it shifts similar to stock with a little added firmness over stock, but not unbearable and with better shift points, but M mode has neck snapping shifts and really propels the car.

I totally like that idea...I wonder how much of a tune can be changed by the different positions?


joe...

[qcman]

Originally Posted by GodWentPunk

I totally like that idea...I wonder how much of a tune can be changed by the different positions?


joe...

They can be very different between D and M. My D is nice and it is firmer than stock but not crazy. My M mode is like Pyro's it will lock the seat belt when it upshifts. The stock trans tune is about the same between D & M when it comes to firmness and shifting speed. I found having the 2 modes stock kind of pointless really.

I happen to think a tune on the L99 is the best bang for the buck mod but maybe that's just me

[GodWentPunk]

silly question but with long tube headers and hi-flow cats, does the tune typically just disable the back O2 censors so they don't report anything? If so, will that still allow me to pass my emissions test? I'm in Illinois and I think all they do is check the computer for errors.


joe...

[pyroguy]

Originally Posted by GodWentPunk

I totally like that idea...I wonder how much of a tune can be changed by the different positions?


joe...

A tune can change shift points/positions, shift firmness, how long a gear is held after a hard acceleration, and more. It’s all in the computer these days.

Originally Posted by GodWentPunk

silly question but with long tube headers and hi-flow cats, does the tune typically just disable the back O2 censors so they don't report anything? If so, will that still allow me to pass my emissions test? I'm in Illinois and I think all they do is check the computer for errors.


joe...

As I understand it, the tune tunes out the error codes thrown on the dashboard for saying there’s an error. The sensors I think still read. However, the only state I believe that has banned long tube headers is California. I lived in a populated area of PA which had emissions testing and I passed with flying colors. The guy doing the test actually complimented my setup. Even here where I live in MO has emissions and they didn’t give it a second thought.

[christianchevell]

Some states dont check new cars for 5 years to smog, you have to look at what laws in your area, long tubes also have to have the Delayed response code not pop up with a CEL as the front o2s are further away from the engine. Your engines AFR will be determined by the front only O2 and if its good enough with out lots of unspent gas running rich in the tune you should pass ….also dependent on regulations...… Allowed long tubes here in Oregon. Only the weird in Portland Smog here.

[GodWentPunk]

It seems that going with Shorties will cause less grief and than LTH.. Maybe that's the way to go and I won't have to worry about all of these regulations. I'll still get a performance bump but just not as much as the LTH.


joe...

[zz430camaro]

Get long tube headers if you are going to do it. Go with the green cats from Kooks, they are better cats but expensive. The tuner will disable reporting codes that will pop up from cats and headers and it will pass the smog test.