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The Roaming G8
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Discussion Starter · #1 ·
So from what I've reading throughout the board is that if you install headers then your car would be running "rich" prior to a tune and if you do enough modifications to the air intake that you'll be running "lean".(http://www.g8board.com/forums/showthread.php?t=68275&page=2) So my question is if you were to do intake modifications to where you are running lean and then install your headers and don't get them tuned(yet) so that you could be running rich wouldn't that balance out?
 

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The Roaming G8
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390 Posts
Discussion Starter · #2 ·
Actually I should've posted this in the V8 Tech section. Could one of the admins move this to the V8 Tech section or would I have to move it?
 

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Yep, that just happened..
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Moved....
 

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The Roaming G8
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Discussion Starter · #4 ·
Anyone have a answer or explanation for this?
 

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The Roaming G8
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390 Posts
Discussion Starter · #6 ·
Well i kinda thought that you would run lean but from alot of threads in this forum I've seen it where everyone claims that after a header install with no tune their car runs rich. I was questioning it in my mind but never spoke out until now.
 

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The Mustang dude
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1,438 Posts
If you ran a wideband I suspect you'd see a richer condition at part throttle as the PCM tries to figure out whats going on, then it'd quickly go to a lean; but probably not dangerously lean at WOT or during aggressive acceleration.
You can live without a tune for a bit, but you will eventually throw codes, so its best to get it tuned as soon as you can after install.
 

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Headers run rich by every LSx car Ive seen on the dyno. The problem with what the OP is getting at is when you run headers and intake on the stock tune the computer cannot adjust far enough to compensate for both.
 

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The Roaming G8
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390 Posts
Discussion Starter · #9 ·
um...yeah...i guess.lol. Yeah so with the stock tune people say that when they install headers that the car runs rich(from what i've read on the forum).Then from the link in my original post it seemed that (for example the vcm) runs lean with the big increase in air. So yea I was thinking that if you installed headers and your car was running rich instead of running lean, and then install a VCM intake which could make you run lean, wouldn't they cancel each other out?lol
 

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Camshaft Master
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126 Posts
The car will run rich, Just recently installed LTS and xpipe, no cats. Stock axle backs, the car has lost a good bit of gas mileage, as i'm only able to get around 21-22 mph whereas on cruising i was around 27-29. With that said, i'm not doing another mod until i'm able to tune it, it just recently threw a CEL and its probably because i have no cats, i'll scan it monday at the shop to make sure, but you do run rich from headers/xpipe install.
 

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Improved air flow through an engine will lean it out. Those that get tuned after a header install, if it is rich, it was rich before the install too. Stock tune is known to be rich. The loss in mileage after an install is the computer re-learning the new mod. It will take a couple hundred miles for a stock tune to learn new fuel trims.
 

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The Roaming G8
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390 Posts
Discussion Starter · #13 ·
Wouldn't it help if you installed the intake and headers then disconnected the battery for 2 hours,connect it back and then drive it around so that it can re-learn what it needs? Not saying this as a alternative for a tune because I'm pretty sure that i'm going to get Pat G to hit me up with a tune. Just trying to feed my brain with information.lol
 

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more air = leaner. Better intake tract (CAI) and/or better exhaust tract (headers,hfc,etc) will lean out the base tune, meaning fuel trims will need to adjust the real stoich verses what the recipie (tune) commands it to have. A Wideband AFR gauge (aftermarket) allows you to verify this, especially at WOT where it's more formula based instead of feedback based.

Some say the stock tune is on the rich side, so by adding a cai or headers or both will cause that to become imbalanced.

Borrow someone's cortex or datalogger and check your LTFT1 and LTFT2's for yourself to learn more. No sense in "guessing" what is happening, that can be "dangerous".

Products like cortex, hptuners, and dashboss all offer differing capabilities for datalogging and display, and if you datalog your own car "before and after" you will not only be able to verify your predictions with empirical data, but you will learn in the process which can't hurt as well! :)

Fuel trims near zero translate to "the tune is accurate for environment and mods". Fuel trims in the + range (for example, +13) means that the base tune is 13% too lean, and the engine is adding 13% fuel in realtime to burn at stoich, as the base tune is inadequate. Likewise, fuel trims in the - range (for example, -4) means that the base tune is slightly rich, and from the feedback of the MAF and narrowband O2's at part throttle, the ECM is pulling / removing 4% of the fuel to burn at stoich. Anything outside of the 20 point sweep of -10 (through zero) to +10 is considered okay, anything beyond that range is considered not okay. If you have a fuel trim of +23 for example, you will probably throw a CEL that translates to a "Bank too lean" code. If you go WOT during this condition, very possibly boom goes.

Does this help?

--zepcom
 

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The Roaming G8
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390 Posts
Discussion Starter · #15 ·
I think that helps out alot. Guess I should invest in some kinda tuning device for at least datalogging purposes. I just started trying to find some kinds vocational school or something where I could go and learn about this stuff hands on. I most definitely don't want to be shooting in the dark with stuff about my car. Cost too damn much.
 
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