Add 2% Fuel @ WOT using SCT X3 tuner

moncho

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Based on a custom tune I have it's set for a commanded A/F ratio of 11.7 @ WOT. I want to change this to 11.4. To achieve this I've been told to add 2% of fuel @ WOT. From what I've read when you begin flashing the PCM with the custom tune you will be prompted to make changes to the tune. I'm asking for what exactly will this option be defined as and will the change be in percentage points? I'd rather know beforehand than to dive in and possibly change something incorrectly.

Thanks in advance!

Cheers,
Ray
 

13BremboGT

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Are tune "options" enabled for your tune? When you write the tunes from a PC to the SCT device, you can opt to allow the end-user to have tweakable settings, or none at all. If your tune was written to your SCT device without any options available, there is no way for you to do it without getting another tune (or re-writing the same tune to the handheld with options turned on).
 

65fastback2+2

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If its enabled you should see a parameter labeled fuel...last time I did it the options were +/- 2%, 4% or 6%.
 

moncho

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Are tune "options" enabled for your tune? When you write the tunes from a PC to the SCT device, you can opt to allow the end-user to have tweakable settings, or none at all. If your tune was written to your SCT device without any options available, there is no way for you to do it without getting another tune (or re-writing the same tune to the handheld with options turned on).

According to the tuner these options are available.

Cheers,
Ray
 

VNMOUS1

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Great! Thanks.

Ray

Keep in mind that you're adding X percent of fuel at wot, so this can be anywhere from 1,000 rpm to the limiter. You're looking to add fuel at the top. Ask your calibrator to do that for you so you're not "fat" somewhere that you needn't be.:beer:

bj
 

moncho

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Keep in mind that you're adding X percent of fuel at wot, so this can be anywhere from 1,000 rpm to the limiter. You're looking to add fuel at the top. Ask your calibrator to do that for you so you're not "fat" somewhere that you needn't be.:beer:

bj

Thanks for the insight BJ.

Just for my understanding is the WOT AFR based on throttle position when determining WOT AFR? In other words when you put your right foot to the floor isn't this when the commanded WOT AFR is achieved? If so, my guess is that the 2% WOT AFR setting on the SCT would only come into play when TP is @ 100%? Someone please set me straight.

Thanks,
Ray
 

VNMOUS1

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Thanks for the insight BJ.

Just for my understanding is the WOT AFR based on throttle position when determining WOT AFR? In other words when you put your right foot to the floor isn't this when the commanded WOT AFR is achieved? If so, my guess is that the 2% WOT AFR setting on the SCT would only come into play when TP is @ 100%? Someone please set me straight.

Thanks,
Ray

Consider all the factors and let's look at a dynograph. When you mat the throttle at 2000 rpm it is wide open. But, until load/rpm/etc come fully into play the a/f drops quickly from 14.7 to (hopefully) commanded at an "angle" of more like 120* and not 180*.

As for the remainder of the pull, the throttle position is WOT, but you'll likely see some level of movement within the line, right? In a perfect world, the commanded fuel at X rpm/X load would be reflected in a line that's straight as an arrow. In that case, yes, you SHOULD be able to add a percentage of fuel at WOT and it have the exact same outcome all the way through the range. There are a lot of factors at work that cause deviations between what goes in and what comes out. Tire/belt/heat/you name it. Many things can cause varying load/spark/etc, thus variations in the outcome.



bj
 
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moncho

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^Sometimes I try to over simplify things, just the way I see things in general. What you say makes sense. Many variables that come into play. The tune is set for commanded 11.7 @ WOT so I may leave it alone but verify with a wideband. I'm just the type of guy that likes a little cushion just in case.

BJ - your a tremendous wealth of information on these forums and I thank you for that.:beer:

Cheers,
Ray
 

VNMOUS1

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^Sometimes I try to over simplify things, just the way I see things in general. What you say makes sense. Many variables that come into play. The tune is set for commanded 11.7 @ WOT so I may leave it alone but verify with a wideband. I'm just the type of guy that likes a little cushion just in case.

BJ - your a tremendous wealth of information on these forums and I thank you for that.:beer:

Cheers,
Ray

My pleasure Ray.

The easiest way for your to increase that cushion "for real" is to run good gas.

There's nothing wrong with 11.7:1, in fact it's a place for good power and safety with a blower car.
 

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