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Discussion Starter #1
I've looked around a bit and haven't found exactly what I'm looking for so I was wondering if there's a list (here or elsewhere) of mods for the 4.6 (2-valve in my case) that require/don't require a custom chip tune. What I'm looking for is basically 2 columns, the first for stuff that can be done to the engine and the stock computer can adapt to (coil packs/wires, water pump, etc.) and then the second for stuff that need a custom tune because either the stock computer can't really take advantage of the changes or simply won't accept them and so the car runs crappy or not at all.

I have done little to my '95 Thunderbird so far beyond a J-Mod rebuild of my automatic (the ~300HP "mild" version), JBA shorty headers, Magnaflow cat pipes and a dual exhaust after the cats (I will stay California compliant there). I believe none of what I've done matters that much to the stock computer and doesn't rise to the level of needing a custom tune (car runs great, sounds better than when I started) but maybe I'm wrong about that.

Also, is there a rundown of different types of custom tunes and what companies do the best work without being stupid expensive? I understand that there are different types of changes, some that don't really hinge on aftermarket parts (changing shift points, rev limits) and other changes that are necessary because of different cams or compression changes or intake changes. I was thinking about having one of those that has more than one tune on it so that I can swap to "stock" for smog testing and then back to custom tune for the mods.

At some point I believe I'll get a set of '97 or so NPI heads done at Modular Motorsports (they are "local" to me in Camarillo) which I assume means PI or similar cams and porting + misc. drivetrain parts. That along with new timing chains/tensioners, oil pump and who knows what else I assume will be installed by them there and at that point I'd expect that they'd do a custom tune for the motor. What I'm wondering about is how much stuff can I do to the car that will be accepted by the stock computer so that I don't cross that line and change something that makes the car hate me because the stock computer is insulted and won't accept that change, hence the 2 lists question (all the changes that don't bother the stock computer/stuff that shouldn't be done without a custom tune).
 

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You "need" a tune if you change the MAF or injectors. Other than that, the computer can usually adapt pretty well, however with certain things like a different intake manifold, larger cams, or ported heads, you will sometimes have issues with it holding an idle. Also once you get past a certain power level, you have maxed out the stock injectors and MAF, so at that point you would have to upgrade those parts, and therefore have to have a tune to tell the computer what MAF and injectors are in it now. That being said, there are 2 things to consider. First, nothing you have done to the car will require a tune. Second, a tune, even with a completely stock motor, will be a more noticeable improvement in acceleration than the sum total of everything you have done.
 

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A short, general list of things that do require a tune...

Any modification to the MAF sensor. Replacement with a stock, unmodified part not included. :)
A differential gear change more than two steps in any direction (e.g. 3.27 to 4.10)
Changes to combustion [chamber] characteristics (e.g. PI or TFS heads, compression changes, radical cam swaps that induce dynamic compression changes) that require spark adjustments
Modifications to the fuel delivery system that affects flow rate (injector size, pressure)


Things that don't require a tune (but are often be better taken advantage of with)...

Drivetrain modifications such as the J-mod, higher stall converters, gear changes (of any size)
A higher volume fuel pump
Mild changes to intake or cams (e.g. PI intake or PI cams)
Exhaust system modifications (headers, duals, crossover pipes etc.)
Thermostat adjustment (e.g. from 195 to 180)


None of this is exhaustive, but hopefully it gives you a good idea.

For mail order tunes, Don LaSota is the one I think of. He wrote most of the in-program descriptions of the SCT PRP back in the day, and has written several tuning manuals. He is incredibly knowledgeable - and has a good way of breaking down what seems like a complicated task into simple steps.
 

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Damn, Decipha, you've done good!!

I wish you'd been doing this 10 years ago, when I was getting into tuning. :0

It would have saved me a ton of cash.

When I run into something I can't solve, I'll call you for sure.
 

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Discussion Starter #6
Here is a bit more in depth as well but basically a re-hash of whats already been covered

New Orleans Tuning - EFIDynoTuning.com
Thanks! I plan on getting a custom tune once I swap to a pair of '97 ported NPI heads with PI or other cams. By then all the mods I think I want for the car will have been finished.
 

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Nice Avatar Decephia. Very appropriate as we approach the anniversary of 9/11. :usa:
 
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