Does CAI and Cat-Back require a tune?
Thread Starter
Melting Slicks
Joined: Jun 2007
Posts: 2,673
Likes: 9
From: Upstate New York
Does CAI and Cat-Back require a tune?
I'd be interested in what our resident forum tuners have to say about this article in GM High Tech Performance - it's in the 6th paragraph.
http://www.gmhightechperformance.com...sts/index.html
Do they mean you need a tune to get the full benefit or are they saying making these changes causes the timing to get pulled and you actually may loose power?
This is the part I'm talking about:
Dan points out that that is important because the factory spark tables are based on airflow. As such, the stock computer tends to pull timing (stock GM timing for this engine runs right at 28 to 29 degrees) when it senses an increase in intake air or decreased backpressure with a better exhaust. (This also tells us that bolt-on exhaust and cold-air kits will need a companion tune to maximize horsepower.) Because of this, Dan estimates another 10 to 15 hp could be left on the table with the stock LS2 because there was timing getting pulled during our test runs
http://www.gmhightechperformance.com...sts/index.html
Do they mean you need a tune to get the full benefit or are they saying making these changes causes the timing to get pulled and you actually may loose power?
This is the part I'm talking about:
Dan points out that that is important because the factory spark tables are based on airflow. As such, the stock computer tends to pull timing (stock GM timing for this engine runs right at 28 to 29 degrees) when it senses an increase in intake air or decreased backpressure with a better exhaust. (This also tells us that bolt-on exhaust and cold-air kits will need a companion tune to maximize horsepower.) Because of this, Dan estimates another 10 to 15 hp could be left on the table with the stock LS2 because there was timing getting pulled during our test runs
Race Director
Joined: Jul 2004
Posts: 16,795
Likes: 62
From: Lake Havasu City, AZ
I am not a tuner... Just an enthusaistic driver. This is my layman's understanding. The PCM can adjust for a CAI and headers to some extent. Hence you will have power gains from using them.
However, this means the PCM is at or near its limit of corrective capabilities. Ideally you want re-tune tune to again put the PCM in the middle of its range of corrective capabilities. Doing this is where the 10-15 extra horsepower comes from.
However, this means the PCM is at or near its limit of corrective capabilities. Ideally you want re-tune tune to again put the PCM in the middle of its range of corrective capabilities. Doing this is where the 10-15 extra horsepower comes from.
Instructor
Joined: Apr 2007
Posts: 200
Likes: 0
From: Hawthorn Woods Illinois
LMB-C6,
Not totally sure if this will help at all but here's my experience. I have an '07 A6 that I had one shop put on Corsa cat backs, Kooks headers and Kooks hi-flo cats. Was told to expect the engine light to come on but I could drive it till I got it tuned and it would not hurt anything. Had already discussed this with my tuner. Brought to the 2nd shop (tuner) about 3 days later for the tune and all I can say is that SOTP speed and performance went WAY up. It was more responsive and had a hell of a lot more power.
From what I hear on the forum about stock dyno #'s being around 337RWHP, I gained 30 RWHP. Not sure if that's good, great or so-so, but it was way better than stock. And more fun!! Hope this helps a little. Good luck!
Fran
Not totally sure if this will help at all but here's my experience. I have an '07 A6 that I had one shop put on Corsa cat backs, Kooks headers and Kooks hi-flo cats. Was told to expect the engine light to come on but I could drive it till I got it tuned and it would not hurt anything. Had already discussed this with my tuner. Brought to the 2nd shop (tuner) about 3 days later for the tune and all I can say is that SOTP speed and performance went WAY up. It was more responsive and had a hell of a lot more power.
From what I hear on the forum about stock dyno #'s being around 337RWHP, I gained 30 RWHP. Not sure if that's good, great or so-so, but it was way better than stock. And more fun!! Hope this helps a little. Good luck!
Fran
Racer
Joined: Apr 2006
Posts: 380
Likes: 0
From: Spring Lake MI
I'm interested to hear what some of the experienced guys have to say about this one.. It's always been said, despite what the mfg lit says, that you won't gain much from just exhaust (maybe a couple rwhp)..but LOSING power?!! Not gaining much..fine..Losing power? Don't want to do that!!
pkstr
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 266
From: St. Louis, MO
St. Jude Donor '08
I'm interested to hear what some of the experienced guys have to say about this one.. It's always been said, despite what the mfg lit says, that you won't gain much from just exhaust (maybe a couple rwhp)..but LOSING power?!! Not gaining much..fine..Losing power? Don't want to do that!!
pkstr
CAI can change things, but not a lot unless you pull your maf screen out (I don't recomend that). Don't really need a tune for a CAI.
Headers are ok without a tune but you'll get a MIL for P0420 and P0430 most likely, cat inefficiency code. Really should get a tune if you get headers or you're missing a lot of the potential gain.
A tune is an excellent mod even if you are stock. CAI and a tune will be worth .4 and 3 mph in the 1/4 most likely. They make a big difference and I highly recommend a tune.
Here's some great reading for you.
http://forums.corvetteforum.com/show....php?t=1900057
Safety Car
Joined: Jan 2001
Posts: 3,879
Likes: 3
From: Hobart, WI
It varies as to which CAI. These cars start rich so a CAI should help lean it a bit. Problem is the MAF is very sensitive to element placement. Have seen a few C6Z systems that screwed up flow to the point that they could not be tuned and thus were erroneously lean (dangerously). Short answer> probably.
Safety Car
Joined: Dec 2004
Posts: 3,565
Likes: 5
From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
yes and no.
if basicmods (exhaust, air filter, intake) are made and it is tested immediately, yes, a loss can be noted. it takes at least 50 miles of continuous use before the pcm will begin to detect the changes and make adjustments.
even though the computer is able to compensate for some modifications does not mean that more power cannot be obtained with a proper tune.
a good tune will always result in more power, even if it hasn't been modded.
if basicmods (exhaust, air filter, intake) are made and it is tested immediately, yes, a loss can be noted. it takes at least 50 miles of continuous use before the pcm will begin to detect the changes and make adjustments.
even though the computer is able to compensate for some modifications does not mean that more power cannot be obtained with a proper tune.
a good tune will always result in more power, even if it hasn't been modded.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 266
From: St. Louis, MO
St. Jude Donor '08
It varies as to which CAI. These cars start rich so a CAI should help lean it a bit. Problem is the MAF is very sensitive to element placement. Have seen a few C6Z systems that screwed up flow to the point that they could not be tuned and thus were erroneously lean (dangerously). Short answer> probably.
I note you are using C5Z06 TI's - they are pretty restrictive on stock cubes and must be a real bottleneck on that ride of yours. I noted a solid .05 gain on the track going from TI's to my Stingers on my H/C C5.
The dyno sheet below is a buddy's C5Z with a G5x2, no other mods.
The dyno sheet shows through the Z06 TI mufflers and with his QTP cutouts open. Almost 10 rwhp/tq gain across the board with the cutouts open.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Safety Car
Joined: Jan 2007
Posts: 4,332
Likes: 0
From: Kuwait
yes and no.
if basicmods (exhaust, air filter, intake) are made and it is tested immediately, yes, a loss can be noted. it takes at least 50 miles of continuous use before the pcm will begin to detect the changes and make adjustments.
even though the computer is able to compensate for some modifications does not mean that more power cannot be obtained with a proper tune.
a good tune will always result in more power, even if it hasn't been modded.
if basicmods (exhaust, air filter, intake) are made and it is tested immediately, yes, a loss can be noted. it takes at least 50 miles of continuous use before the pcm will begin to detect the changes and make adjustments.
even though the computer is able to compensate for some modifications does not mean that more power cannot be obtained with a proper tune.
a good tune will always result in more power, even if it hasn't been modded.
