Do All Engine Mods Require a Tune?
Thread Starter
Burning Brakes
Joined: Nov 2012
Posts: 1,049
Likes: 1
From: Wisconsin
Do All Engine Mods Require a Tune?
I've been researching intake and exhaust modifications and it seems that "tuning" needs to be an integral part of the modification and I just wanted to see if that is correct.
In particular on the LS3 engine, it seems that the engine's balance is delicate enough that when you mess with its air intake and exhausting capabilities you may actually be robbing the engine of performance (at least in some rpm range(s)) as it attempts to compensate for measured changes in air/fuel mixture or pressure. In this sense, it's not a matter of tuning to "get the most out of the modification" (even though with the tune and the mod you may add net horespower or torque), but more a matter of ensuring the mod is not costing you power. Am I understanding this correctly? Or have I fallen prey to tuner marketing wives tales?
In particular on the LS3 engine, it seems that the engine's balance is delicate enough that when you mess with its air intake and exhausting capabilities you may actually be robbing the engine of performance (at least in some rpm range(s)) as it attempts to compensate for measured changes in air/fuel mixture or pressure. In this sense, it's not a matter of tuning to "get the most out of the modification" (even though with the tune and the mod you may add net horespower or torque), but more a matter of ensuring the mod is not costing you power. Am I understanding this correctly? Or have I fallen prey to tuner marketing wives tales?
Drifting
Joined: Feb 2012
Posts: 1,796
Likes: 37
From: skiatook oklahoma
i'll let 'tuners' explain, i'm not qualified for that.
but what i can tell you is that besides your points, there are hundreds of codes that will/can be thrown when outside of allowed limits. tuning keeps you out of 'limp mode' at a minimum due to a cel thrown and out of unsafe limits that could harm the engine.
anyway, thats my point
but what i can tell you is that besides your points, there are hundreds of codes that will/can be thrown when outside of allowed limits. tuning keeps you out of 'limp mode' at a minimum due to a cel thrown and out of unsafe limits that could harm the engine.
anyway, thats my point
Thread Starter
Burning Brakes
Joined: Nov 2012
Posts: 1,049
Likes: 1
From: Wisconsin
i'll let 'tuners' explain, i'm not qualified for that.
but what i can tell you is that besides your points, there are hundreds of codes that will/can be thrown when outside of allowed limits. tuning keeps you out of 'limp mode' at a minimum due to a cel thrown and out of unsafe limits that could harm the engine.
anyway, thats my point
but what i can tell you is that besides your points, there are hundreds of codes that will/can be thrown when outside of allowed limits. tuning keeps you out of 'limp mode' at a minimum due to a cel thrown and out of unsafe limits that could harm the engine.
anyway, thats my point
Thank you. I believe I've found a performance product vendor who also does tuning. It seems as though this particular vendor's product does not require tuning and to the extent tuning is done as an option, it is done to keep the engine running properly. In other words, in addition to the 15 rwhp gain from the product, the vendor won't be tuning in such a way as to try to deliver an additional 20+ hp while subsequently voiding my warranty. Not ready to go there yet.
Thanks Again!
Last edited by Rathmullan; Feb 21, 2013 at 08:12 PM.
SUBVETTE
Joined: Jul 2006
Posts: 3,841
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From: San Diego CA
Plan your mods and then do them all at once followed by a dyno tune. Your goal is to maximize the output of the total package and that final tune does it by pulling it all together. You are correct in your analysis of the engine breathing and air fuel ratios effects. A tune will also be able to determine if, as you suggest, a mod is in fact interfering with engine performance in a certain rpm band. I had a cold air intake at one time that actually seemed to remove power in certain ranges. Turned out that it just couldn't be tuned out. It was causing turbulence and the fix was to go with a different system. The point is that the tuning operation clearly pointed out that there was a problem which I otherwise wouldn't have known. It's like a symphony, air, fuel and timing, working together properly to produce the best music.
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Plan your mods and then do them all at once followed by a dyno tune. Your goal is to maximize the output of the total package and that final tune does it by pulling it all together. You are correct in your analysis of the engine breathing and air fuel ratios effects. A tune will also be able to determine if, as you suggest, a mod is in fact interfering with engine performance in a certain rpm band. I had a cold air intake at one time that actually seemed to remove power in certain ranges. Turned out that it just couldn't be tuned out. It was causing turbulence and the fix was to go with a different system. The point is that the tuning operation clearly pointed out that there was a problem which I otherwise wouldn't have known. It's like a symphony, air, fuel and timing, working together properly to produce the best music.
Tech Contributor
Joined: Dec 1999
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From: Anthony TX
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SUB VETTE
Adding any simple mod like an air filter or CAT back mufflers, your PCM will NORMALY easily be able to adjust the fuel trims and allow the engine to run without issues.
When you start adding mods like a CAM, intake manifold (FAST 90/92/102 or headers; you significantly change the air flow thru the engine and the PCM has a tougher time adjusting to run correctly.
The PCM adjust a table called Long Term Fuel Trims (LTFTs) to correct for the AIR FUEL RATIO changes. The PCM can only adjust +- 25% and some mods will max out that table in the RICH direction.
That will cause the Wide Open Throttle Air Fuel Ratios in the Power Enrichment (PE) table to be significantly rich and performance will not be optimum when the AFRs are too rich.
Bottom line.. Any mod that DOESNT need tuning will not increase the engine performance all that much.
Adding any simple mod like an air filter or CAT back mufflers, your PCM will NORMALY easily be able to adjust the fuel trims and allow the engine to run without issues.
When you start adding mods like a CAM, intake manifold (FAST 90/92/102 or headers; you significantly change the air flow thru the engine and the PCM has a tougher time adjusting to run correctly.
The PCM adjust a table called Long Term Fuel Trims (LTFTs) to correct for the AIR FUEL RATIO changes. The PCM can only adjust +- 25% and some mods will max out that table in the RICH direction.
That will cause the Wide Open Throttle Air Fuel Ratios in the Power Enrichment (PE) table to be significantly rich and performance will not be optimum when the AFRs are too rich.
Bottom line.. Any mod that DOESNT need tuning will not increase the engine performance all that much.
Last edited by Bill Curlee; Feb 22, 2013 at 05:12 PM.
Former Vendor
Joined: Aug 2005
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From: Lewisville TX
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SUB VETTE
Adding any simple mod like an air filter or CAT back mufflers, your PCM will NORMALY easily be able to adjust the fuel trims and allow the engine to run without issues.
When you start adding mods like a CAM, intake manifold (FAST 90/92/102 or headers; you significantly change the air flow thru the engine and the PCM has a tougher time adjusting to run correctly.
The PCM adjust a table called Long Term Fuel Trims (LTFTs) to correct for the AIR FUEL RATIO changes. The PCM can only adjust +- 25% and some mods will max out that table in the RICH direction.
That will cause the Wide Open Throttle Air Fuel Ratios in the Power Enrichment (PE) table to be significantly rich and performance will not be optimum when the AFRs are too rich.
Bottom line.. Any mod that DOESNT need tuning will not increase the engine performance all that much.
Adding any simple mod like an air filter or CAT back mufflers, your PCM will NORMALY easily be able to adjust the fuel trims and allow the engine to run without issues.
When you start adding mods like a CAM, intake manifold (FAST 90/92/102 or headers; you significantly change the air flow thru the engine and the PCM has a tougher time adjusting to run correctly.
The PCM adjust a table called Long Term Fuel Trims (LTFTs) to correct for the AIR FUEL RATIO changes. The PCM can only adjust +- 25% and some mods will max out that table in the RICH direction.
That will cause the Wide Open Throttle Air Fuel Ratios in the Power Enrichment (PE) table to be significantly rich and performance will not be optimum when the AFRs are too rich.
Bottom line.. Any mod that DOESNT need tuning will not increase the engine performance all that much.
You can look at it like this to make it really simple. If it is in front of the MAF, or after the 02 sensor you can change it and it wouldn't need a tune.
Anything between the MAF and front 02's will probably require some sort of tuning change to get the most from that modification.
Thread Starter
Burning Brakes
Joined: Nov 2012
Posts: 1,049
Likes: 1
From: Wisconsin
Bill and Anthony:
Thank you kindly. Your responses are straight forward and to the point and worded such that even I can understand. This is most helpful and will influence my purchase decisions going forward.
Thanks again!
Sincerely,
Rathmullan
Thank you kindly. Your responses are straight forward and to the point and worded such that even I can understand. This is most helpful and will influence my purchase decisions going forward.
Thanks again!
Sincerely,
Rathmullan
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Burning Brakes
Joined: Mar 2007
Posts: 1,107
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From: Wichita Falls, TX
You can look at it like this to make it really simple. If it is in front of the MAF, or after the 02 sensor you can change it and it wouldn't need a tune.
Anything between the MAF and front 02's will probably require some sort of tuning change to get the most from that modification.
