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Necessary to tune the ECM after making intake and exhaust mods to a 1991 L98?

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Necessary to tune the ECM after making intake and exhaust mods to a 1991 L98?

 
Old 03-14-2019, 12:39 AM
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mostliharmless
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Default Necessary to tune the ECM after making intake and exhaust mods to a 1991 L98?

Hey guys! Tried searching around here and elsewhere but couldn't seem to get a straight answer.

So I'm planning to do some upgrades to the L98 intake and exhaust. Runners, headers, performance catback exhaust, K&N air filter, etc. that sorta thing.

I know from doing research that the L98 for this year had only a MAP intake sensor (no MAF), which from what I understand doesn't respond well to aftermarket mods and that it might need to be "tuned" for best performance.

Is this true? If so how do I proceed with something like that? Thanks!
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Old 03-14-2019, 08:01 AM
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Originally Posted by mostliharmless View Post
I know from doing research that the L98 for this year had only a MAP intake sensor (no MAF), which from what I understand doesn't respond well to aftermarket mods and that it might need to be "tuned" for best performance.

Is this true?
Your Key word here is best. To get the best performance, and I am assuming by best performance you mean the best power output, even the stock car benefits from a tune. The factory had to be a little conservative.

Cat-back and K&N won't need anything, air foil, AFPR and other minor bolt-ons won't need a thing and won't return much gains in general.

Runners/Headers will certainly benefit from a Tune but it's not necessary unless you have issues. This will depend on what Headers/Runners you choose.

If you do anything with the heads/cam/injectors you will definitely need a tune.

To save yourself time, money, and headaches. Decide what you want to do and see if you are willing to bank roll it all, write out a plan you know you will follow. There are forum members on here that have tune files that will probably be real close to what you need. Then you only have to do it once.
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Old 03-14-2019, 09:07 AM
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A MAP car would respond better, but it is not strictly necessary with those mods. A dyno curve will give an indication you if it does, but I'd wait for more extensive changes before I did the chip, unless you know youre done after these modifications.
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Old 03-14-2019, 02:47 PM
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Originally Posted by mostliharmless View Post
Hey guys! Tried searching around here and elsewhere but couldn't seem to get a straight answer.

So I'm planning to do some upgrades to the L98 intake and exhaust. Runners, headers, performance catback exhaust, K&N air filter, etc. that sorta thing.

I know from doing research that the L98 for this year had only a MAP intake sensor (no MAF), which from what I understand doesn't respond well to aftermarket mods and that it might need to be "tuned" for best performance.

Is this true? If so how do I proceed with something like that? Thanks!
First off, you are not using the latest and greatest car so, there might not be a tuner wanting to delve into the older stuff. You start with all the mods and you cannot find a tuner, you are going to have problems.

Start with the basics. Find a person with a dyno who is willing AND able to do the tune. The dyno session is about $600 and up. So, find that first and talk to him about what mods he has had good luck with. Otherwise, you might be like many who have the "Win a race on Sunday, sell a car on Monday". Just because I did well with this cam and he did well with that set of heads and she did well with that other set of headers doesn't mean they all will work together optimally. Best get the tuner to design a system that he knows will work.

I got the Superram Intake and Accel Tri-Y headers that LPE sold for my F-body. They woke the car up but it had moments of hesitation and wasn't as good as it could be. Brought it to LPE and had him (before he passed) tune it. All the issues went away and the car was better mannered and had a better power. Later on, heads and cam that they had good luck with and redid a dyno tune. Don't do one thing, tune, do another and tune, etc. It is a waste of money.
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Old 03-14-2019, 02:57 PM
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To ensure adequate WOT fuel install an AFPR and bump fuel pressure as air flow mods are added.

This method worked well with my '88 but not sure about with a MAP sensor.

If you're running an A4, a 2,000rpm TC and shift kit will work wonders for low end grunt and still be very "drivable".
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Old 03-14-2019, 05:14 PM
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Originally Posted by 65Z01 View Post
To ensure adequate WOT fuel install an AFPR and bump fuel pressure as air flow mods are added.
Within reason this works because you are increasing the flow rate of the injectors.. same pulse width gets more fuel and you keep it well within the short and long term fuel trims that the car can read based off the Oxygen sensor. I would suggest going to a wide band to keep an eye on things if you want to "optimize" this way.



Originally Posted by 65Z01 View Post
If you're running an A4, a 2,000rpm TC and shift kit will work wonders for low end grunt and still be very "drivable".
Agree here too. This gets overlooked a lot of times in build because torque converters just don't seem to be too sexy to discuss. It does make a difference.
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Old 03-14-2019, 05:44 PM
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Originally Posted by KyleF View Post
Within reason this works because you are increasing the flow rate of the injectors.. same pulse width gets more fuel and you keep it well within the short and long term fuel trims that the car can read based off the Oxygen sensor. I would suggest going to a wide band to keep an eye on things if you want to "optimize" this way.

Agree here too. This gets overlooked a lot of times in build because torque converters just don't seem to be too sexy to discuss. It does make a difference.
Can our system work with a wideband O2 or are you using it as a standalone system?

If the builder is any good, he'd recommend the right stall which you can check with the maker. That said, I know I was using a Precision Instrument TC and asked them the stall which they were happy to furnish. Their number was pretty much spot on with the builder's recommendation. Also, if not satisfied, PI will give you a free re-stall within 2 years. Problem is now you are sticking a good TC in front of an old trans. Not sure if it is a good idea without a rebuild or at least a refresh. OTOH, if you break it within 2 years, PI will cut it apart and clean it as part of their re-stall so that is a possibility.
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Old 03-16-2019, 12:19 PM
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Originally Posted by aklim View Post
Can our system work with a wideband O2 or are you using it as a standalone system?
I don't know if a 96 ECM can take a wide band. I was suggesting a stand alone. They make kits that have hand held readers. Just have a bung you normally keep plugged and only use it when you are tuning. Or you can mount one in the car.
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